This PDF file contains the front matter associated with SPIE Proceedings Volume 11340, including the Title Page, Copyright Information, Table of Contents, Author and Conference Committee lists.

In this paper, combining with the tenth anniversary load test of Sutong Bridge, we proposed the Brillouin Optical Time Domain Analysis (BOTDA) to conduct health monitoring research on the bridge, and completed the following three aspects: Firstly as an auxiliary measure of strain monitoring, monitor the level of stress and strain along the longitudinal bridge to each position. Secondly through the parking of the vehicles at different positions on the bridge pavement, the influence lines on the overall structural stress of the bridge are obtained. Thirdly through the long-term strain monitoring of the bridge, the impact of the usual traffic load information on the bridge strain is obtained.The results show that the technology not only breaks through the monitoring bottleneck of traditional point sensors, but also realizes distributed measurement of strain on the transmission path; it can also be used for real-time monitoring, damage identification, crack location, settlement monitoring of traffic load information of bridges and other structures.. Compared with the traditional sensor test results, the effectiveness and frontier of the technology are proved, and the significance of the distributed fiber-optic sensor technology for the health monitoring of major structures such as bridges is fully explained.

Space light-fiber coupling technology converts spatially transmitted beams into fiber-optic transmissions, facilitating free-space optical communication, and fiber laser radar systems for signal processing in optical fibers. However, it is very difficult to accomplish precise alignment between the spatial beams and the fiber with micron level. In this paper, particle swarm optimization is applied to achieve two-dimensional auto-alignment between the spatial beams and the fiber. The theory proves that when the dimension takes 2, the number of groups is 10, the inertia weight is 0.4~0.8 and the number of iteration does not exceed 100, the particle swarm optimization can converge to the maximum coupling power, and the greater the weight of the inertia, the slower the convergence speed, the larger the search area. If the inertia weight decreases linearly with the number of iterations, the spatial light-fiber coupling auto-alignment function can be quickly completed while searching the alignment space in a wide range.

Most of irradiation resistant fibers are designed to contain pure quartz fiber core to ensure good irradiation resistant performance. However, multimode (MM) fiber containing pure quartz core owns lower bandwidth because of the step index (SI) distribution. Thereby the application of it will be limited though the irradiation resistance is fine attributing to pure quartz core. To combine better irradiation resistance and higher bandwidth, a novel irradiation resistant and high bandwidth MM fiber (RMM-fiber) being of special waveguide was designed and experimental investigated via testing attenuation, bandwidth and mechanical strength before and after ⁶⁰Co radiation (up to 25 Mrad(Si), 10 Mrad(Si)/s). It is indicated that the RMM-fiber owns lower irradiation induced attenuation comparing with normal MM fiber, and the bandwidth after irradiation is 403.1 MHz km @1300 nm that is much higher than SI type MM fiber. The RMM-fiber shows no reduction but a little rising on mechanical strength. Additionally, it has outstanding environmental suitability in -100°C~+125°C temperature cycling test.

On the base of an analyzing system, we demonstrate a testing method to reveal whether the FOG scale factor is stability after a long term ageing. The temperature of the chamber is set to 85°C in order to accelerate ageing of the adhesive. The FOG scale factor data is sampled each month. Results show that the MTTF (Mean Time to Failure) of the FOG coils is not satisfied with the application need. The analyzing system has good application prospects in testing the instabilities of the FOG’s Scale Factor.

The change of field of view (FOV) which is caused by the image defocus of laser communication terminal introduced in the process of assembly will have a great interference to the link energy budget. In view of the problem, the method of measuring the FOV is proposed to calculate the defocus amount of receiving system. On the premise of the sensitivity of the detector is satisfied by the received energy, the relationship among the defocus receiving energy, defocus amount and FOV are derived by the theoretical analysis and calculation. With the link distance is 1km, the defocus amount of 0.27mm is calculated under the FOV of 0.965mrad which is measured by experimental test. The maximum FOV from 2km to 4km can be reversed further. At the same time, the test experiment platform was designed and the FOV of the laser communication terminal was measured. Compared with the theoretical calculation results, the maximum error is less than 55μrad, which is conformed to the error allowable range. Conclusion: By the method of measuring the FOV of the system, the defocus error which is caused by assembling can be calculated, so the maximum FOV of the system in different link distance can be simulated. The method not only solves the problem that the defocus amount is difficult to measure, but also provides theoretical guidance to increase the FOV of laser communication by introducing the image defocus.

A novel imaging sensor which is made of image optical-fiber bundle and industrial camera is proposed. All of the image optical fiber component are custom made and the diameters of the mono fibers are only 1 or 2 μm. In order to match the resolution of image optical-fiber bundle, the pixel size of the sensor chip are also smaller than 2 μm. After removing the protective glass window that cover the sensor chip of camera, the high-resolution imaging can be realized by bonding the optical fiber component and the sensor. The theoretical analysis and experimental result show that the resolution of the sensor is larger than 250 lp/mm, which can improve the imaging quality of industrial detection and monitoring. In particular, the proposed imaging sensor is suited for the oil mist or dust detection environment.

In this paper, a magnetic field sensor with simple fabrication, high sensitivity and wide measurement range is proposed. The sensor consists of fiber Bragg grating, sensitivity enhancement structure (SES), magnetostrictive particles and epoxy resin matrix. Metal tube with length of 5 mm is glued onto both sides of the grating as SES, and the mental tube is covered with grooves. The FBG with mental tubes is coated with the matrix made of magnetostrictive particles and resin. During the curing process of matrix, a uniform magnetic field with 200mT and parallel to the fiber is applied to make the orientation of magnetostrictive particles constant. It also can make particles have uniform spatial distribution. Firstly, by comparing the performances of sensors made of three different resin without mental tube with the sensor made by gluing FBG onto Terfenol-D rod directly, it is found that the sensor with epoxy crystal adhesive has the highest sensitivity reaching 0.58 pm/mT. Secondly the sensor based on epoxy crystal adhesive with SES is evaluated. Compared with the sensor without SES and gluing diretly, the sensitivity increases 5.17 times to 3.58 pm/mT and the measurement expands ranging from 0 mT to 226 mT.

According to the principle of optical coherence domain polarimetry (OCDP) technique, the use of a ghost-peak-free white light interferometer is introduced for performance controlling of fiber optic gyroscope (FOG) fiber coils, including raw polarization maintaining fiber (PMF) quality inspection, PMF coil winding process design, coil winding machine performance evaluation and PMF coil temperature induced stress measurement. One can see from measuring result, OCDP testing at all of these stages does provide a very powerful distributed tool for improving the performance of fiber coils.

Lithium-ion batteries have become a most promising energy storage candidate in power station and electric vehicles because of its high power capability, high energy-conversion efficiency, and environmental friendliness. It is significant to diagnose the security of battery by monitoring the its state parameters. Wherein, temperature and strain are the two of the important ones. In this work, a sensitivity-enhanced FBG strain sensor was designed for the strain measurement of lithium-ion batteries. This proposed sensor consists of two FBGs and a lever mechanism. The lever mechanism works as a displacement amplifier. The amplified deformation of battery act on the functional FBG and induce the larger wavelength shift. The thermal compensation FBG can eliminate the influence of ambient temperature. The calibration test shows that this sensor has a high sensitivity of 11.55 pm/με and a good linearity. Application test on a battery illustrates that the strain responses of the sensor has a good repeatability in three cycles. Then, artificial neural networks were used for state of charge (SOC) estimation. When the strain and temperature data were set as input parameters, SOC can be well predicted. Therefore, this sensor can monitor the strain on the cell with high sensitivity and accuracy. This research demonstrated a new solution for SOC estimation especially based on strain signals, which can provide more informative data for battery management system.

The fiber optic current transformer (FOCT) is affected by complex environment in actual operation which will lead performance deteriorate or even malfunction. This paper introduces the application status and common fault modes of FOCT, and a fault diagnosis algorithm of FOCT based on Wavelet-Allan variance is presented. Wavelet transform is used to identify the jump signal for the mutation fault diagnosis, and Allan variance analysis is used to analyze the noise distribution for the gradual fault diagnosis. By combining the two methods above, the condition monitoring and fault diagnosis of FOCT can be realized without changing the structure of the original transformer or adding additional detection equipment. This method is proved to be effective and accurate by diagnosing faults from FOCTs in substation.

We present a novel microstructure evolution model for PCFs in heating process, which is based on Navier-Stokes Equation in fluid mechanics and level set method. The model can be applied to describe microstructure deformation for PCFs. Utilizing the theoretical model, we have calculated accurate PCF microstructure changes from the different heating parameters, one of which may conduce an excellent microstructure for splicing, tapering, or else. The model is feasible in PCF optical devices design and manufacture without trial and error, which promotes the performance of PCFs partially. We have further performed a representative experiment on heated PCFs, and good agreements are found between experiment results and the simulations.

The fiber optic gyroscope has become to one of the most important sensors in developing due to light in quality, high accuracy, compact in dimension and long life^[1-4]． These features have developed new applications of the gyroscope not only in conventional aerospace application area but also in industrial application area, such as control and navigations of unmanned vehicles, antenna/camera stabilizers, and so on. More and more FOGs have been applied in all kinds of satellites for attitude control. With the great technology progress on fiber optic gyroscopes in recent years, the reliability of fiber optic gyroscopes has been focused on. The fiber coil, as one of the most critical components in fiber optic gyroscope，its reliability directly determines the reliability of the fiber optic gyro. This paper uses the Bayesian estimation method to study the reliability of the fiber coil. Aiming fiber optic gyroscope fiber coil Failure Data Reliability analysis of the problem, on the basis of analyzing the failure mode, select Weibull distribution as its life mode, the estimated time of each detection without failure data using Bayesian theory failure rate, and thus the estimated model parameters fiber coil reliability. The Bayesian estimation method combined with experience information greatly reduces the number of test samples, and to overcome the shortcomings of the traditional reliability evaluation method relies on failure data, has a high value in engineering applications. This estimation method shows its significance in saving test costs and time.

The development of robots has played an important role in industrial production. Because of the complexity of application objects, traditional rigid robots have some shortcomings in security and flexibility. Due to the high flexibility of the material of the robot body, the robot soft hand provides a new idea and direction for solving the complex adaptability and flexibility of the robot in complex environment. However, the non-linearity and complex geometric characteristics of soft materials make modeling and control a problem. For this reason, this paper takes advantage of the advantages of high sensitivity, light weight and good flexibility of optical fibers. Fiber grating is embedded in the soft material to detect bending force and contact force without affecting the motion of the soft hand, so as to realize the sensing function. On the basis of pointing out the shortcomings of existing flexible sensors, an embedded soft material detection method based on optical fiber is proposed. Firstly, the structure of pneumatic soft finger is simulated and optimized, and the optimal size of soft finger is determined. Soft fingers were prepared by wax loss process. Fiber Bragg Grating (FBG) is embedded and a tactile sensing system is established. The results of FBG-based flexible finger bending and contact force detection are verified. The validity and rationality of the sensor are proved. This is of great significance to the research of soft robots. Finally, this paper summarizes the full text.

In the traditional multi-granularity switching system, the wavelength is the smallest exchange granularity, but the wavelength granularity is coarse, which is not suitable for small-scale integrated services.Therefore, the optical code packet granularity is introduced, and a three-layer multi-granularity optical cross-connect (MG-OXC) system is established based on optical code division multiplexing (OCDM).Subsequently, the Code Group Routing Entity (CGRE) technology was proposed, which not only improves the utilization of wavelengths, but also reduces the number of ports required for service transmission and reduces network operation costs.In this paper, based on the premise of CGRE technology, a code group routing table is established according to the PCEP general standard and a new code group routing allocation strategy is proposed.The new code group routing allocation strategy can make full use of optical code resources in the wavelength, improve network performance, and reduce network operation costs.

In the existing GMPLS-based distributed control switching network, each network node needs to bear the traffic pressure, not only to calculate the service transmission path, but also to be responsible for data forwarding. In software-defined networking (SDN), the control plane is decoupled from the forwarding plane, which simplifies the network structure and facilitates network maintenance and management. The multi-granularity network is combined with SDN, and the stateful PCE is used as a controller of the network control plane to implement soft control of the network and ensure that the information of the network traffic is controlled in real time. The standard PCEP protocol is extended to add optical code granularity and CGRE (Code Group Routing Entity) related messages, making it suitable for code group switching networks, thereby enabling network services to be transmitted more efficiently and intelligently.

Fiber optic gyroscope (FOG) is a multi-technology product which integrates optics, mechanics and electricity. It has the advantages of high reliability, long life, light weight, small size and "all solid state". It has been widely used in military and civil fields such as sea, land, air, sky and submarine, and has become the mainstream gyroscope in the field of inertial technology. With the widespread application of FOG, the degradation of its key performance indicators gradually emerges as time goes on. Therefore, it is urgent to obtain the reliability index of FOG. In order to obtain reliable reliability index of FOG with time and cost saving as much as possible, it is necessary to choose reasonable acceleration test method, acceleration model and life distribution model to study the acceleration life model of high precision FOG. To this end, this paper carries out the following aspects of work: (1) The basic composition and main reliability index of high precision fiber optic gyroscope are introduced. (2) The sensitive stress of high-precision FOG is temperature and humidity. A high-precision FOG acceleration model based on temperature-humidity double-stress Peck model is established for the first time. (3) The life distribution model based on drift Brownian motion is analyzed, and the applicability of the life distribution model is determined by Monte Carlo simulation combined with the acceleration model of Peck model. (4) According to the performance degradation data of accelerated life test of FOG, the reliability of life distribution model of high precision FOG is evaluated.

The fiber-optic hydrophone, with the characteristics of high sensitivity, easy multiplexing and long transmission distance, is becoming a new direction for the development of the underwater detection system. The overflow cavity type optical fiber hydrophone is composed of a sensitizing inner shell, a rigid outer housing, sensing optical fiber and other auxiliary structures. It is a small-size and high-sensitivity hydrophone in the form of the air-backed sensitized structure, which could be applied to new towed array and fixed array system. In this paper, the acoustic performance of the hydrophones in different sound fields was simulated using the COMSOL finite element analysis. In the light of the design of the overflow cavity type optical fiber hydrophone, the acoustic field distribution of the hydrophone surface and the strain distribution of the optical sensing fiber were analyzed and compared with the free sound field model and the standing wave field model. And the sensitivity response of the hydrophone was predicted. On this basis, the sample of the overflow cavity type optical fiber hydrophone with the same design parameters was developed, and the sensitivity test was carried out in the standing wave tube. The experimental results show that the test frequency is 315 Hz to 2 kHz, the phase shift sensitivity of the hydrophones is -143 dB ref.1 rad/μPa. The difference between the test results and the simulation results is less than 1.5 dB under 1kHz.

In this paper, for the first time, we propose a large-broadband orbital angular momentum (OAM) mode converter based on helical long period fiber grating (HLPG) working at turning point (TP). Owing to the combination of dual-resonance peaks at TP, an OAM mode converter with 3-dB bandwidth of ~287 nm is readily obtained, and a high coupling efficiency of ~100% is achieved. We believe that this OAM mode converter will play a key role in fiber communication and other fields.

In the existing three layers multi-granularity optical switching network based on code group routing entity (CGRE), network nodes can not only achieve the switching of fiber granularity, wavelength granularity, and optical code granularity, but also bundle the associated optical codes into CGRE to transmit in the CGRE pipes. In multi-domain optical networks based on this switching system, the research of routing and optical code allocation is a key point. In the process of optical path establishment and optical codes selection, there is still a phenomenon of network delay and optical code allocation conflict by the traditional serial processing. In order to solve the above problems, based on stateful PCE (Path Computation Element) technology, this paper proposes a strategy for build CGRE pipes (B-CGREP) module and a mechanism for optical code allocation element (OCAE), and introduces the architecture of hierarchical stateful PCE (H-SPCE) in multi-domain network, the architecture consists of a main stateful PCE and multiple sub-stateful PCEs. Add a B-CGREP module to main stateful PCE, and each sub-stateful PCEs is equipped with an OCAE. On the basis of the interaction between the B-CGREP module in the main stateful PCE and the OCAE of each sub-domain, every domain can perform the intra-domain signaling process independently and parallel to achieve fast allocation of cross-domain optical paths and avoid optical code allocation conflicts among domains, as a result, improving the performance of multi-domain intelligent optical networks.

The key technology and main difficulty for optical fiber perimeter system is the extraction and recognition of intrusion signals, vibration signals normally consist of noises, intrusion and disturb signals. Firstly, a new detection method combining constant false alarm rate (CFAR) method and Level Crossing (LC) method was proposed to distinguish the intrusion and no-intrusion signal before recognition. The former can produce adaptive thresholds to eliminate noise and disturb signals according to the background homogeneity, the later can ensure the integrity of the intrusion signal and further reduce disturb signal. Second, multi-feature parameters including traditional timedomain features, wavelet packet energy Shannon entropy and wavelet packet energy, energy proportion, kurtosis, skewness are accurately extracted from the intrusion signal. Finally, use support vector machine (SVM) identify multi-feature vectors of different types of vibration signals. The proposed method was experimented on Sagnac optical fiber pre-warning system. The result show that the method can extract vibration signal effectively form sensing signals, improve the system recognition rate.

The precise and time of OTA test is mainly determined by the number and the distribution of the measurement points on the sphere of the DUT. Two methods have been developed to measure TRP and TIS. We propose an evenly distributed sampling method, which is more accurate and efficient to evaluate TRP and TIS than the evenly angle sampling methods. And also give the test result to support the evenly distributed sampling method.

Optical-path difference (OPD) is a key parameter for the fiber-optic interferometer, especially for the large-scale multiplexing of fiber-optic interferometric sensors (FOIS) array. Due to the OPD directly affects the background noise of the system and the performance consistency among different array elements. Most of the time, the latter is very critical for the FOIS array. Several methods have been adopted for the OPD measurement of the fiber-optic interferometer, including the white-light interferometry, the optical-time-domain reflectometry (OTDR), the optical-frequency-domain reflectometry (OFDR). Unfortunately, none of the methods mentioned above can directly realize OPD on-line measurement of FOIS, which is multiplexed with the time division multiplexing (TDM) and the wavelength division multiplexing (WDM). In this paper, an OPD measurement method for multiplexing FOIS using TDM and WDM based on the improved OFDR has been present. The most distinguishing feature of this method is that it transformed the FOIS array under tested into a part of the OFDR system. The modulated linear sweep light directly injected into the FOIS array under tested and traversed every array element through array network. Thus every interferometer of FOIS became the interferometric structure of the improved OFDR, and the OPD measurement of complexity multiplexing FOIS array has been vastly simplified into the fiber length measurement of interferometer in proper order. Results show that the measurement accuracy of this approach can achieve millimeter level and the measurement range up to hundred meters for FOIS using TDM and WDM through a single measurement.

In view of mode field matching problem between the polarization-maintaining photonic crystal fiber and the conventional optical fibers, the polarization and mode field distribution characteristics of photonic crystal fiber were analyzed and investigated by using a finite element method. The loss mainly comes from the mismatch of two kinds of optical fiber mode field diameter (MFD). The collapse of air hole in photonic crystal fiber can be accurately controlled by heating photonic crystal fiber with fusion splicer, and MFD of photonic crystal fiber can be increased. We presented changing the fusion parameters of fusion splicer to reduce the fusion splicing loss and improve the splicing quality between PCFs and PMF with arc discharge of fusion splicer. Finally, we get a loss of 0.8dB for the later from PCF to PMF, and 0.5dB from PMF to PCF. At the same time, tensile strength is better than 100kpsi.

A demodulation based on the principle of fiber Bragg grating edge filter method is used to measure impact energy of acrylic plate (PMMA) and aluminum plate in this paper. A new demodulation method based on damping attenuation principle is proposed. Fiber Bragg grating sensing system is built in the experiment. The complex vibration wave generated by impact energy is processed by using the envelope of peak value in MATLAB. The experimental results show that using the time length corresponding to the peak attenuation of 10% as the demodulation basis has a higher Goodness of fit. The linear fitness of PMMA plate and aluminium plate is 0.94 and 0.89, respectively. At the same time, it is concluded that this method can be used to preliminarily determine whether the plate is viscoelastic or not. This is a new potential demodulation method for practical impact energy detection based on fiber Bragg grating.

With the expansion of the Qiongzhou Strait shipping market, shipping pollution has become increasingly harmful to atmosphere and ocean. Ships have become China's third largest source of air pollution, and existing technologies cannot meet the regulatory needs of the maritime sector. Therefore this paper proposes a ship network monitoring system based on narrow-band internet of things (NB-IoT). The system obtains ship related information through GPS, monitoring and sensors, which can monitor vessel track, ballast water, sewage, oil-water separator, exhaust gas and incinerator, etc. It has the characteristics of narrow bandwidth, low power consumption and wide coverage and reuse of spectrum resources. The system improves the efficiency of vessel surveillance and can be extended to other waters or industrial management areas.

In this paper, a miniaturized highly-selective six-pole filter with wide stopband is reported. For this purpose, a triple-mode resonator loaded with stub and patch is proposed, which is characterized both by theoretical analysis and full-wave simulation. The designed six-pole filter is composed of two identical triple-mode resonators. The two resonators are coupled to each other to increase the selectivity. There are two transmission zeros at each side of the passband, which increase the stopband attenuation. The other two transmission zeros suppress the harmonic frequencies, which extend the 20dB stopband rejection levels up to 6GHz. The center frequency of the filter is 2.2GHz, the fractional passband is 13%, and the 30dB regular coefficient is better than 0.6.

The rapid development of fiber optic sensing technology has enriched the types of wind tunnel strain balances. Numerous wind tunnel tests and research institutions have carried out various work on the fiber optic balance (FOB) based on the fiber optic strain gage (FOSG). In hypersonic wind tunnel tests, the total temperature of airflow is so high that both the model and the balance will be heated by the heating airflow, resulting the thermal output of the FOSG which affects the accuracy of the FOB. In order to reduce the thermal output effect, a new self-temperature compensation (STC) method has been proposed in this paper, by subtracting thermal expansions between the balance and a STC structure. In addition, the structure can not only reduce the thermal output, but also achieve a strain amplification of the FOSG. The formulas of both strain amplification and thermal compensation of the FOSG with the STC structure were deduced, as well as finite element simulation and tests were carried out, which verified the effectiveness of the compensation structure. The results of theoretical derivation, simulation and tests showed that the strain amplification decreases with the increase of the distance of installation points of the FOSG, and there is a zero point in the thermal output. However, due to the simplification of the STC structure, there are deviations in the theoretical derivation which can only be used in the preliminary design. The agreements between experiments and simulations, verified the temperature compensation effectiveness of the STC structure.

Traditional quartz optical fibers can not overcome their own shortcomings in non-linearity, Rayleigh scattering, dispersion and high delay^[1,2], while anti-resonant hollow fibers can break through Shannon limit, and have the characteristics of low loss, low delay, high bandwidth and high damage threshold. With the development of new technologies such as Internet of Things and large data, people's increasing demand for information and traditional reuse. Ways including wavelength division multiplexing, frequency division multiplexing and space division multiplexing have gradually encountered bottlenecks ^[3]. We need to explore new ways of multiplexing, improve the information capacity of communication networks, and meet the growing information needs of people. Through research, we find a new type of cylindrical vector beams, which is not only the spatial orthogonal mode, but also the basis of optical fibers. The signature mode can improve the communication capacity of the channel.

In this paper, different fiber structures and their applications are introduced, such as terahertz solid-core dielectric fiber, terahertz hollow dielectric fiber and terahertz porous core fiber. Terahertz fiber is a kind of waveguide made of polymer materials in terahertz radiation band. Metal fibers in terahertz radiation band are mostly proposed by scaling the size of metal fiber structures in microwave and radio radiation bands. In metal fiber devices, high-frequency radiation waves such as visible light dissipate quickly, but terahertz radiation waves do not. They can still conduct in metal fibers. According to the different fiber structures, terahertz metal fibers include terahertz metal wire fibers, terahertz metal hollow fibers and terahertz metal planar fibers. With the rapid development of terahertz fiber technology, the application of terahertz fiber devices are more and more extensive. The application of terahertz fiber in coupler, absorber and refractive index sensor has also become the focus of science research and discussion.

Using rolling shutter effect of the CMOS camera can increase the data rate of camera-based visible light communication (VLC) system. However, when fewer pixel columns represent one bit, the grayscale value fluctuation becomes serious, which leads to data logic not being correctly defined by the threshold, and therefore degrades the demodulation performance. In this paper, a thresholding scheme based on adjacent pixel grayscale value to reduce the influence of grayscale value fluctuation is proposed, which sets threshold using the grayscale values of the forward and backward pixels adjacent to the current pixel. And combining with segment downsampling, experimental results show that the proposed demodulation algorithm can achieve a bit-error-rate (BER) performance well below the forward error correction (FEC) limit of 3.8×10^-3 with the bit resolution of 2.962 pixel/bit, and the net data rate can reach 10.56 kbit/s.

As a key research material, graphene has high thermal expansion coefficient and heat conductivity. FBG with cladding by coated graphene can effectively improve temperature sensing characteristics according to the temperature sensing principle of FBG. Firstly, after removing the coating on FBG surface with acetone and stripping pliers, graphene nanosheets were deposited on the cladding material of FBG by a simple evaporative deposition method. The temperature sensing sensitivity 13.05 pm/°C was obtained in experiment after linear fitting of data, which was about 67% higher than that of bare FBG of 7.82pm/°C. Secondly, in order to improve the purity, compactness and controllable thickness of the coatings, we deposit graphene films of FBG cladding with coating process in vacuum by pulsed laser deposition (PLD) technology. Finally, the temperature sensing sensitivity of the FBG sensor coated with graphene thin film by PLD reached 17.31 pm/°C, which was about 120% higher than that before deposition. Moreover, the whole temperature sensing system of FBG with cladding graphene film has simple structure and high practicability

In order to complete the high-speed wavelength demodulation of output signal of Fiber Bragg Grating (FBG) sensing unit, an edge filter wavelength demodulation system is established in this paper. This wavelength demodulation system uses a reference FBG as an edge filter. First, the mathematical model of the system is built based on demodulation principle. In the model, the spectrum of FBG is simplified to Gaussian distribution. The model describes the relationship between the output voltage and input wavelength differential. According to the research above, the hardware and software of this demodulation system are developed. Besides, a calibration method of the system is proposed. Finally, experiments are carried out. According to the experiment results, the sensitivity of the wavelength demodulation system is 6.3mV/pm. When the demodulation frequency is up to 5kHz, the wavelength resolution is 0.23pm. This system has many advantages, such as simple structure, low cost and high resolution in high speed wavelength demodulation

Fiber Bragg grating (FBG) sensing technique is used to measure physical parameters by monitoring wavelength-shift. The key to the high-speed demodulation of FBG sensor signal is how to extract the central wavelength of FBG reflection wave quickly. Compared with other methods, the demodulation technology based on tunable laser has the advantages of high-speed and accuracy. In this paper, in order to solve the problem of inaccuracy in high-speed scanning of tunable laser, a high-speed dynamic calibration scheme is designed. The simulation and experiment are carried out. The relationship between wavelength and control current is accurately obtained.

A large-range three-coil coaxial optical fiber displacement sensor for measuring the air gap of a direct-drive wind turbine is designed in this paper so as to overcome the problem that the traditional reflective optical fiber sensor has a small measuring range. The mathematical model of the modulation function of the three-coil coaxial large-range fiber displacement sensor is established by using the simplified geometric optical reflection spot model, so that the ratio compensation mechanism under different combinations is analyzed and compared, and the parameters affecting the characteristics of the sensor, including the fiber core radius R and the numerical aperture NA of the transmitting fiber, and the number of receiving fiber loops in the second, third and fourth layers of the sensor probe are analyzed by simulation. The results show: As the number of laps of the receiving fiber turns, the sensor range is significantly improved, and its sensitivity is improved, but the corresponding initial dead zone is also increased; the smaller the numerical aperture of the transmitting fiber, the larger the linear range of the output characteristic curve; the larger the radius of the fiber core, the larger the linear range of the output characteristic curve, but the corresponding initial dead zone becomes larger and the sensitivity is reduced, so that the final selected design parameters of the system are given by analysis. Finally, through the sensor characteristics experiment, the actual measurement range of the sensor probe is consistent with the theoretical simulation results, and its measuring range can reach 3.5mm- 8.5mm.

There is temperature and pressure cross-sensitivity when using ordinary fiber to detect pressure. In order to solve this problem, a fiber Bragg grating pressure and temperature sensor based on double equal thickness and equal strength cantilever beam was proposed in this paper. Feasibility of the structure was verified by theoretical analysis and simulation. The first sensing element of the sensor is a cantilever beam with equal thickness and strength. It mainly consists of temperature-strain sensitization zone of bimetal and load-bearing zone of stress-strain optical fiber. The second sensing element consists of two fiber Bragg gratings with different grating spacing distributed on a single fiber along the axial direction. The distance between these two gratings are predetermined. Because the initial grating spacing of the two fiber Bragg gratings is different, the corresponding demodulated wavelength varies and possesses a certain wavelength difference as well. Hence, the measurement of two different parameters can be realized. The first Bragg grating is fixed on the bimetal temperature sensing region and cannot measure pressure as it does not vary with external pressure. The theoretical derivation of optical fiber sensing proves that the distance between the two peaks (the wavelength difference between the two peaks) of the second Bragg grating reflectance spectrum is only proportional to the pressure and independent of temperature variation. From this principle, the pressure is measured. The simulation results reveal that the proposed structure can realize two-parameter measurement of pressure and temperature. The fiber Bragg grating detection device has the advantages of low cost, stable and reliable operation.

In order to improve the accuracy of the fiber bragg grating (FBG) demodulation system and the spectral flatness of the tunable laser, a calibration scheme and flatness optimization method for effectively calibrating the etalon error are proposed. The scheme utilizes the higher temperature stability of the acetylene gas cell and The position of the standard sensor in the etalon is known, enables calculation accuracy of the etalon spectral nonlinearity error. The paper analyzes and optimizes the problem of the flatness of the tunable laser, verifies the data processing effect of the correlation filtering and calibration algorithms. The experimental results show that this paper has certain significance for the study of tunable laser flatness and related data processing schemes. The final demodulation system has an accuracy of 1 pm, the difference between the maximum optical power and the minimum optical power is less than 4dB and the flatness of tunable laser is improved by nearly 10dB compared with optimization. Related research solutions can provide reference for performance optimization of FBG demodulation systems.

A photonic crystal fiber ring resonator (PCF-RR), constructed with a length of high-birefringence PCF and a conventional polarization-maintaining (PM) coupler whose pigtail fiber is of PANDA type, is fabricated. The resonating curve of the PCF-RR is experimentally obtained with the finesse about 14. Moreover, the backscattering curve of the PCF-RR is measured and the in-cavity equivalent backscattering coefficient is estimated. In addition, the shot-noise limited sensitivity (SLS) of resonant fiber optic gyroscope (RFOG) equipped with the fabricated PCF-RR is numerically calculated and disscussed.

A theoretical model combined with finite element simulation and numerical analysis is presented to design and optimize of the fiber-wrapped mandrel optic microphone based on distributed acoustic sensing (DAS). To increase the acoustic pressure sensitivity, the optimized fiber-wrapped mandrel microphone with engraved uniform grooves is fabricated and tested as the acoustic transducer. The average sensitivity is -136.915dB re:1rad/μPa between 50 Hz to 2450Hz, which is 25.306dB higher than the same fiber optic microphone without uniform grooves. The experimental results are in good agreement with the theoretical results, which shows this theoretical approach is effective to design and optimize the fiber-wrapped mandrel optic microphone based on DAS.

A series of theoretical study of HWC for distributed acoustic sensing system is proposed to optimize the gaugh length. With the considition of SNR and spatial resolution, the optimal gaugh length is 0.4/(sinαcosθ) to 0.5/(sinαcosθ) times of the Ricker wavelet’s spatial wavelength, when the Ricker wavelet seismic wave travelles to the HWC with the wrapping angle α and the incident angle θ. Similar with the situation in DAS with straight fiber, the optimal gaugh length can achieve the SNR bigger than 90% of the maximum, and the deviation of detected temporal wavelength is less than 14%. Additional coefficient of 1/sinαcosθ is provided to any imping angle of the seismic wave and wrapping angle for the normal working environment.

Stable environmental factors are important for operation of optical communication equipment and devices. With the large number of applications of mobile unmanned base stations and wireless laser communication devices, more equipment and devices work in a nonstable and unclosed environment, and the working environment is more complicated, even those are used on a mobile platform. Environmental factors such as temperature, humidity, height, vibration, shock, acceleration, dust, mold, salt spray, noise, etc. put forward higher requirements for the environmental adaptability of optical communication equipment and devices. At present, there is a lack of uniform standards and operational evaluation methods for the environmental adaptability evaluation of optical communication equipment operating in complex environments. In this paper, a comprehensive evaluation method of environmental adaptability of optical communication equipment is proposed by using analytic hierarchy process, Delphi expert evaluation method and fuzzy comprehensive evaluation method, and the process of environmental adaptability evaluation based on these three methods and a three-tier evaluation index system are constructed. The method is of great value to the environmental adaptability evaluation of optical communication equipment.

Lack of suitable towed array has existed as a main problem for further extended use of small underwater mobile platforms such as UUV. In this paper, an ultra-thin fiber-optic hydrophone towed array is developed based on DFB fiber laser, which diameter is only 12mm. And the performance of the towed array of the fiber-optic hydrophone is tested by towboat. The experimental results show that the towed noise of the array is 69dB re. uPa/√Hz@1kHz. In addition, the fiber towed hydrophone array can precisely determine the spatial characteristics of the underwater acoustic field at 6 knots, which verifies the feasibility of the ultra-thin fiber laser hydrophone towed array in UUV and other underwater platforms.

The fast increasing of mobile data traffic, and the stringent requirements of the emerging services in terms of latency and bandwidth, have spurred numerous influences for the change of Cloud Radio Access Network (C-RAN) and cloud computing. MEC enabled C-RAN have emerged as promising candidates for the next generation access network techniques to accommodate the fast growing IoT traffic and improve the performance of IoT services. Deploying MEC servers in C-RAN, which brings IoT services to the edge network, not only improve users quality of service (QoS), but also alleviates the network traffic of core network. The deployment performance of MEC servers is, however, highly related to the workload assignment. Therefore, the deployment mechanism of MEC servers and workload assignment scheme would jointly affect QoS of users, economic benefits of operators. In this paper, we jointly consider MEC deployment and workload assignment for minimizing the sum of deployment cost and delay in C-RAN based on optical rings. Simulation results showed that the proposed algorithm not only minimizes the total cost (MEC deployment cost and E2E delay), but also demonstrate good trade-off between deployment cost and average delay.

In recent years, the power level of laser outputting from twins fiber, being of pump unit fiber and gain unit fiber, is continuing rising. However, little report is focused on the pump coupling efficiency and thermal management on account of the distinctive waveguide of twins fiber. In this paper, the experiment study was launched on pump coupling efficiency and thermal management based on our previous work. To facilitate observing, two waveguides were designed as “cycle pump unit + octagonal gain unit” and “cycle pump unit + cycle gain unit”, while both gain units contained no doping core and the claddings were all 125 um approximately. It indicated that the pump power proportion between pump unit and gain unit was gradually changing with increasing of fiber length when the fiber was pumped from only one side of pump unit. The dynamic balance of pump power proportion could be obtained as the length of “cycle pump unit + octagonal gain unit” twins fiber is more than 4 m. By contrast, the balance point appeared earlier for “cycle pump unit + cycle gain unit” twins fiber before the length was up to 4 m. Further, the laser experiment was executed by using typical twins fiber that was consisted of one octagonal gain unit, containing Ytterbium (Yb) doped fiber core, and cycle pump unit. When the power was pumped into the fiber from the pump unit, the temperature of pumping point was obviously lower than conventional double cladding active fiber.

The TDM-PON is a promising candidate for mobile fronthaul due to its high scalability and cost effectiveness. Mobile fronthaul traffic has a strict one-way latency requirement of about 250μs. Therefore, latency is a critical issue for applying TDM-PON to mobile fronthaul. The traditional equal-length transmission division scheme can reduce the latency in TDM-PON. However, the scheme can still be optimized in terms of latency and bandwidth utilization. We propose a variable-length transmission division scheme to further reduce the latency in TDM-PON and improve the bandwidth utilization compared with the traditional scheme.

The random walk coefficient of fiber optic gyroscope (FOG) is a kind of gyroscope output error accumulated over time by white noise. In order to achieve 100s bias stability of high precision FOG less than 0.0001 °/h, the random walk coefficient of FOG is less than 0.0000167 °/√ht. Based on the analysis of the factors affecting the random walk coefficient of FOG, a random walk coefficient model is established in this paper. Considering the characteristics of high precision FOG such as oversampling and low bandwidth, a method to reduce the random walk coefficient of high precision FOG is proposed. Through the theoretical analysis of the above methods, the feasibility of the method is proved theoretically. Furthermore, the comparative test of the precision of the high precision fiber optic gyroscope using the above method proves the feasibility of the above method. The random walk coefficient of the gyroscope is significantly reduced, which makes the bias stability of the high precision fiber optic gyroscope achieve the design goal.

The improvement in the performance of fiber optic gyroscope raises increasingly high standard on the performance of potting adhesive for optical fiber coil. It cannot only enable the stability of coil potting, but also maintain long-term stability under complex environmental stress. In order to meet the indicators of temperature performance of optical fiber coil, we have prepared the acrylic matrix potting adhesive via UV photo-curing by grafting the hard-segment chain containing benzene ring with polyurethane acrylate(PUA) as the matrix, studied the influence of resin matrix, photoinitiator and active diluent on the UV curing of potting adhesive for optical fiber coil, and went into in details the indicators including the curing rate, modulus and glass transition temperature performance of potting adhesive so as to provide experimental support for obtaining the best matched UV potting adhesive curing system. In this study, we have characterized the molecular structure of potting adhesive via infrared spectroscopy, studied the thermomechanical properties of potting adhesive by thermal analysis, and finally verified the process stability of potting adhesive and the temperature characteristics of coil through coil winding and potting and curing.

With the rapid development of FOG inertial navigation technology in China, it is possible for FOG inertial navigation system to achieve " one nautical mile in a month" navigation accuracy under temperature control environment. As the core component of FOG inertial navigation system, the performance of high precision FOG directly affects the accuracy of navigation system. Even in a good temperature control environment, the current performance index of high precision FOG is not enough to support the navigation accuracy of "one mile in January". Broadband ASE light source is widely used in high precision fiber optic gyroscopes. The low temporal coherence of the light source is conducive to improving the noise level and bias stability of the gyroscope. With further research, If the output power of ASE light source exceeds a certain level (The power detected by photoelectric detector greater than 10uw), it is found that the relative intensity noise(RIN) of the light source will be the main noise of the FOG. On the basis of studying the sources of fundamental noises (especially intensity noise) in high precision FOG, this paper puts forward the technology of suppressing the noise of high precision FOG, and further designs (large ring size and fiber length) and develops a prototype of high precision FOG with noise suppression technology. The test results of the prototype demonstrate the effectiveness of the suppression technique (for example, ALLAN variance comparison results before and after using suppression technique). The prototype of the accuracy is expected to approach the navigation accuracy of " one nautical mile in a month " through further testing in the FOG inertial navigation system.

Regardless of many researches done in recent years, most wind turbines are still unable to reach their design lifetime ^[5]. Failures in the gearbox, especially in the planetary stage, have been a major cause of reliability problems in the modern wind energy turbine system. The following paper proposes a fault diagnosis method based on the strain signal of the ring gear. First, the strain signal is collected from the side of the ring gear using FBG sensors in normal condition and faulty condition. Then the collected strain signal is processed and analyzed. In the time-domain analysis, traditional statistical indicators like Peak to Peak, Kurtosis, Crest factor and Peak value are adopted. The analysis results show the effectiveness of the proposed method for identifying tooth crack fault of the ring gear.

With the rapid development of mobile Internet, the business volume continues to increase, which puts forward higher requirements for carrying network. As the current mainstream load carrying network scheme, IPRAN network conforms to the load carrying requirements of various services, not only adapting to base station transmission, but also compatible with multi-service comprehensive transmission. Different networking schemes will lead to great differences in cost. How to design the lower cost IPRAN networking scheme rapidly while meeting the business requirements has always been the concern of telecom operators. This paper presents a cost optimization scheme based on IPRAN networking. Based on the actual situation of BBU and RRU distribution in the region to be planned, we designed the access scheme for RRU with the aim of minimizing the sum of lines between BBU and RRU, so as to ensure the lowest line cost. In addition, we propose two constraints, namely, the number of comprehensive service access nodes on each comprehensive service access ring and the number of centralized BBU on each comprehensive service access node. Under the two constraints, we choose the scheme with the lowest equipment cost. Finally, we conducted simulation on the algorithm proposed in this paper, and the results showed that: for IPRAN networks with less than 1000 base stations, this algorithm could select the scheme with the lowest equipment cost from many schemes within 0.7 seconds, and meanwhile give the line design scheme with the least optical fiber loss, providing reference for IPRAN network.

With the popularization of emerging services such as 5G, cloud computing, the backbone network traffic has grown rapidly and the network running state will change frequently. Unfortunately, the unrelated development of the IP layer and the optical layer in the existing network leads to lack of flexibility in services and makes the hardness and cost of the overall operation and maintenance of the backbone network higher and higher. although the IP layer and the optical layer are converged, due to the uncertainty and unpredictability of the IP business itself, the lack of dynamic interaction mechanism between the two layers becomes increasingly prominent. Therefore, this paper proposes a new NSE-RFC (a network operation state evaluation algorithm based on random forest classification) algorithm, which provides a scientific and comprehensive evaluation of network running state. The results show that the correct rate of the algorithm is 97.5%, which can accurately evaluate the network running status. Finally, the validity of the model is verified by the consistency of the evaluation results of the model and the variation of the time distribution characteristic map of each evaluation index.

This paper presents a path and algorithm scoring method, which can quantitatively evaluate the degree of optimization and intelligently alert potential problems to realize automatic planning and maintenance of optical networks. Since the development of the networks, there is a growing demand for high speed, low latency, and low power consumption. Path selection has always been a problem that needs to be considered in detail in network communication. The combination of classical graph theory and continuously developed algorithms makes algorithms appear constantly. It is found that the increase in the number of services makes the high separation between the actual paths and optimal paths. Combining the scores, we can allocate routing and spectrum for different types of services, meanwhile the average running time of a single service performs lower using the path and algorithm scoring method, which will save a lot of processing time. The result of the simulation shows that as the number of services increases, the scoring method has a clear advantage in processing services. According to this method, a data foundation can be provided for automatic optimization threshold monitoring for operators to adjust the network in advance.

This paper proposes an access network requirements analysis method based on similar service feature values clustering. The network service feature values data are collected from the real access network, including devices and users’ information. The K-means ++ algorithm is adopted to cluster the PON ports, based on the similar service feature values of users connected to them. 3 classifiers are selected for classification training and prediction. They are K-nearest neighbors, SVMs and perceptron. In the case of no clustering, K-nearest neighbor algorithm performs better, and the classification correct rate is about 91.1%. And if the data is divided into 5 groups by K-means++ algorithm, it can be calculated that the average accuracy is 94.3%. Compared with the result without clustering of service feature values, it achieves more accurate prediction and the correct rate is increased by 3.3%. With this method, the operator can determine whether the PON port needs to be expanded, making the expansion planning more forward-looking. At the same time, combining the prediction results with the PON port geographic information, it can distinguish areas with sufficient or insufficient broadband resources, and helps operators adjust service allocation plans to match user needs.

A 45° fiber cantilever beam for high temperature measurement was fabricated by femtosecond laser in single mode fiber. The temperature sensitivity is obtained to be about 17 pm/℃ at 800 ℃ and 1560 nm. The 45° fiber cantilever beam possesses good repeatability and stability in high temperature. The sensor is small in size, cheap and good stability.

A novel temperature-insensitive sensor probe is proposed and experimentally characterized. The sensor probe uses an etching cladding Few Mode Fiber Bragg Grating (FM-FBG) to sense the surrounding refractive indexes (SRI), which depends on the reflection peaks. To compensate for the temperature effect in SRI sensing, various guides modes in FM-FBG that have the different sensing behaviors are used for implementation. Both the propagation characteristics and operation principle of such a sensor are demonstrated in detail. A sensitivity of ~2 nm per refractive index unit (RIU) are obtained within the SRI range of 1.333–1.373. This sensor is temperature independent due to the temperature-insensitive nature of wavelength differential Δλ between the two reflection peaks of the etching cladding FM-FBG.

In this process, the processing flow of fiber Bragg grating (FBG) embedded carbon fiber reinforced composites are prepared by means of pressurized film forming and end-surface elicitation. Firstly, the development of composites in aerospace field is introduced. Then, according to the principle of FBG sensor, a scheme for embedding fiber grating into carbon fiber composites is designed. There are three key steps involved in this process, namely, laying the bare fiber parallel to the carbon fiber cleavage direction, applying the end-surface elicitation method with the use of stainless steel thin tubes and Teflon fine tubes for protection, and pasting the rubber strip tile on the end to prevent the curing of the fiber break. After processing, a 260x60x3mm surface intact product is made according to the design scheme. There is no deformation in Carbon fiber surface and the end-surface is intact.

A non-invasive vital signs monitoring system based on fiber-optic interferometers using single mode fiber (SMF) is presented in this paper. The fiber-optic interferometers was formed by a dual biconical structure without splicing point.The experimental setup was designed to collect the vital signs data of user on bed for processing. With optimized algorithm, human being’s heart beat and respiration signals can be monitored in an contactless and non-invasive way. The experimental results on the measurements of breathing rate and heart rate agree well with the results obtained from medical equipment.

At present, the portable carrier catalytic methane detection and alarm instrument for coal mine generally has many problems, such as high power consumption, short standby time, low detection accuracy, few parameters and single function, which can not meet the rapid development needs of mine safety. In this paper, a low power portable laser methane detection and alarm instrument based on tunable laser absorption spectroscopy (TDLAS) is designed. The instrument can detect methane concentration, ambient temperature and ambient pressure at the same time. It has the functions of sound and light alarm, historical data storage and query, and integrates Wi-Fi to realize data wireless transmission. The instrument can work continuously for 36 hours, and the response time is less than 15 seconds. It has the function of self-diagnosis. The overall performance of the instrument has been greatly improved compared with the traditional mine methane portable instrument. A mobile methane alarm Internet of things(IOT) system for coal mine based on portable instrument has been developed, which realizes real-time upload of data and cloud analysis, makes the traditional mine gas monitoring and control system powerfully supplemented, greatly improves the detection level of coal mine gas, and has broad application prospects.

Based on the application field of high precision Fiber optic gyroscope (FOG), high requirements are put forward for the accuracy of FOG, the stability of scale factor and the nonlinearity of scale factor. The performance of light source is closely related to the performance of these gyroscopes. Therefore, the requirements of high power, high stability, high spectral symmetry and low coherence are put forward for light source. According to the characteristics of high precision FOG, an ASE source is proposed. In the light path aspect, the physical model of ASE light source, the influence of Erbium-doped fiber length, optical path structure scheme, pump wavelength and pump power on the average wavelength of the light source are analyzed. The optical path structure and the length and pump power range of Erbium-doped fiber are determined. Through the analysis of spectral coherence, the Gauss spectrum with no sub-peak of the coherence function is selected as the filtering scheme through orthogonality. Optimize the parameters of light source by experiment and filter simulation. In the aspect of power control, improving power stability by power feedback with controlling the temperature characteristics of the feedback loop device. The ASE light source designed above can provide power output of more than 20 mW. Within operation temperature of high precision FOG, the change of wavelength stability is less than 5 ppm and the change of power output is less than 1%. It is an ideal light source for high precision FOG.

An optical model to simulate the distributed fiber optical sensor based on spontaneous Brillouin spectrum is derived. The reliability of this model is validated with experimental measurements. Using this analytical expression, parametric studies are conducted to investigate impacts of key factors including fiber loss, signal to noise ratio, bandwidth and scanning step on the optical fiber sensor measurement error. The simulation results exhibit good agreement with previous published calculation results. Applying this novel model into the data interpretation, measurement error of distributed fiber optical sensor based on spontaneous Brillouin scattering can be better controlled.

This paper introduces an intelligent fiber detection system for perimeter security. This system detects personnel turning over wall and passing through ground intrusion by a common single-mode communications optical cable on the wall or under the ground. When the intrusion happens, the system detects and locates the behavior. Then the high-speed camera will be controlled to turn and shoot the location of the invasion through the relay module, video recorders, switches and fiber optic transceivers. Meantime, the alarm information will be remotely published. This whole system design is reasonable and put into operation for half years in Daxing smart parks in Beijing. It realizes the function of the intrusion monitoring, identification, proof providing and information publishing, which improves intelligence level of the park administration.

Laser methane sensor has been widely promoted and successfully applied in coal mines as a new and effective technology building on the approach of laser-based absorption detection. Compared with the traditional catalytic methane sensor, the laser methane sensor discussed offers the important advantages of a long calibration period, high detection precision, the absence of ‘zero drift and low power consumption, all of which are significant advantages for use in coal mining applications. By compensating for the temperature and pressure of the gases present, the accuracy of the methane sensor is evident across a wide range of temperatures and pressures, making it suitable for gas detection, including methane, in pipelines as well. The wireless laser approach which is incorporated into the methane sensor allows wireless transmission and data uploading to a cloud server through NB-IoT. This tackles the problem in gas pipeline monitoring of the length of many pipelines and thus the wide distribution of the sensors, avoiding complicated wiring and thus high associated cost. Further, remote data management can then be achieved, all of which greatly improves the flexibility and security of the management of the pipeline and the data generated.

In this study, distributed optical fiber temperature sensing (DTS) system is used as the method of monitoring the temperature field inside the thermal storage tank. On the basis of a practical engineering application, the temperature field characteristics inside the thermal storage tank is obtained and analyzed when the thermal storage and heating system operates. The results show that the distributed fiber temperature sensing system is convenient to construct and build, and it can provide effective data support for the evaluation and design of the thermal storage and heating system.

In order to monitor and position the leakage of the heat network in real time effectively, this study introduces and adopts distributed optical fiber temperature sensing (DTS) system as the method of heat network leakage monitoring. The temperature change rate is used as the basis for determining the operating state. Not only does the whole system have no blind zone of leakage monitoring, but also provides accurate alarm information and fast response, which enables managers to deal with faults timely and avoid heavy losses. Therefore, the DTS system has a high promotion value in the field of heat network leakage monitoring.

Distributed optical fiber temperature sensing system (DTS) is a sensing technology for real-time sensor of spatial temperature field distribution. The technology is based on Raman scattering and optical time domain reflection (OTDR),, and is composed of a demodulation host and a temperature sensing cable. The system obtains the ground temperature field change through the temperature sensing cable, calculates the geothermal energy replenishment amount and the recharge rate, and determines the recovery of the geothermal field after heating. It provides according to setting the allowable amount of geothermal energy to be mined and ensuring the long-term sustainable operation of the geothermal heating system.

This paper discusses the research progress of low-power technology of laser methane sensors for coal mine. On the basis of environment of coal mines, such as ultra-long-distance transmission and high stability, a series of studies have been carried out. The preliminary results have been achieved in the research of low power consumption, temperature and pressure compensation and reliability design. The technology is applied to various products in coal mines, and achieves high stability and high reliability in products such as laser methane sensor, laser methane detection alarm device, wireless laser methane detection alarm device, and optic fiber multichannel laser methane sensor. Experimental testing and analysis of the characteristics of laser methane sensors, combined with the actual application.

Oil storage tank is an important facility for oil production and refining. This paper presents a fire monitoring system for oil storage tank based on distributed optical fiber temperature sensing system(DTS), and demonstrates the laying method for both routing fiber and temperature sensing fiber. This system can realize real-time distributed temperature monitoring on the perimeter of secondary sealing ring of oil storage tank and has various alarm mechanisms. The system has been installed and tested in Shikong oil transportation station of China National Petroleum Corporation(CNPC) in Gansu, China. Through the actual test results, the feasibility and advantages of the distributed optical fiber temperature measurement for oil storage tank are verified and the temperature accuracy of the system is better than 1°C.

Laser methane gas sensors have been increasingly accepted in coal mine safety monitoring. Most laser spectroscopic methane gas sensors are based in BFB lasers at around 1650nm. However, they suffer from high power consumption and high cost due to temperature control is required for laser diode operation at constant temperature. VCSEL lasers have offered low operation current and low power consumption when operating at non-TEC mode. However, it is found that the interference noise is critical for laser methane detection. This paper report typical results of the laser diode ripple characterization method and methods of noise reduction methods are discussed.

Numerical assessment of temperature uncertainty of Raman-based distributed temperature sensor is taken out in this paper. The sensing system utilized a modified loop-configuration to avoid stimulated Raman scattering and wavelength dependent loss. The experimental results show that the temperature accuracy reaches 0.74°C (RMSE) between -65°C to 300°C with 2 km fiber under test.

Shaft is an important structure of mine. Deep mining increases mine pressure, induces shaft deformation and affects mine normal lifting. How to improve the inspection efficiency, reduce the maintenance cost and ensure the normal operation of the shaft is an important problem facing the mine. The paper introduces the optical fiber sensing technology to monitor the equipment status of the main shaft, puts forward the implementation scheme of the optical fiber monitoring of shaft deformation, and sets up a shaft equipment condition monitoring system based on the optical fiber sensing technology. It can realize equipment displacement monitoring, strain monitoring and vibration signal monitoring in the process of shaft operation. Comprehensive on-line monitoring of shaft running state can be realized, which opens up a new method for shaft deformation monitoring technology. Fiber optic sensing monitoring technology is of great significance to the safe operation of shaft.

The belt conveyor serves as the main coal transport equipment in a coal mine and its safe operation is the lifeline of safety in coal mine production. However, traditionally, monitoring for ignition and for roller faults along the belt conveyor is problematic and so this paper puts forward an approach using radial grating vibration sensing technology for both belt conveyor roller vibration monitoring. This can then be used to predict the fault state in the roller and its position, using distributed optical fiber temperature measurement technology which can be used for ‘hot spot monitoring’. This enables better fire prevention along the belt conveyor, which plays a positive and effective role in better mine safety.

The coal industry plays an important role in the economic development of China. With the increase of coal mining year by year, coal mine accidents caused by gas explosion also occur frequently, which poses a serious threat to the life safety of absenteeism and national property safety. Therefore, high-precision methane fiber sensor is of great significance to ensure coal mine safety. This paper mainly introduces two kinds of quasi-distributed gas optical fiber sensing systems based on laser absorption spectroscopy. The gas fiber optic sensor based on absorption spectrum has high measurement accuracy, fast response and long service life. One is quasi-distributed optical fiber sensing system based on spatial division multiplexing (SDM) technology and the other is quasi-distributed optical fiber sensing system based on optical time domain reflection and time division multiplexing(TDM) technology.