Monitoring the geometry of an moving element is a crucial task for example in robotics. The robots equipped with fiber bend sensor integrated in their arms can be a promising solution for medicine, physiotherapy and also for application in computer games. We report an all-fiber intensity bend sensor, which is based on microstructured multicore optical fiber. It allows to perform a measurement of the bending radius as well as the bending orientation. The reported solution has a special airhole structure which makes the sensor only bend-sensitive. Our solution is an intensity based sensor, which measures power transmitted along the fiber, influenced by bend. The sensor is based on a multicore fiber with the special air-hole structure that allows detection of bending orientation in range of 360°. Each core in the multicore fiber is sensitive to bend in specified direction. The principle behind sensor operation is to differentiate the confinement loss of fundamental mode propagating in each core. Thanks to received power differences one can distinguish not only bend direction but also its amplitude. Multicore fiber is designed to utilize most common light sources that operate at 1.55 μm thus ensuring high stability of operation. The sensitivity of the proposed solution is equal 29,4 dB/cm and the accuracy of bend direction for the fiber end point is up to 5 degrees for 15 cm fiber length. Such sensitivity allows to perform end point detection with millimeter precision.
In this paper we present the possibility of supercontinuum generation in the dual mode and single mode regime of highly birefringent microstructured fibers. Unique birefringent fiber geometry enables precise dispersion control in both fundamental and second order modes. Our results are related to create new functionality in the generated supercontinua: polarization based spectrum tunability and flatness control. We analyse experimentally the stability of the generation of nonlinear effects in our series of fibers, related to polarization coupling and dispersion changes. The domination of nonlinear effects can be changed in the fundamental and second order modes according to the fiber geometry in order to generate a spectrally flat broadband source. Here we demonstrate the ability to generate a customized supercontinuum in three regimes of mode operation - dual mode, fundamental mode only and second order mode only - where spectral flatness and range are controlled.
We present the novel 7-core and 19-core hole-assisted fibers designed to satisfy the most demanding requirements of the ITU-T G.657.B3 recommendation for bend-insensitive fibers. The fibers are compatible with standard single-mode fibers with regard to modal properties, dispersion characteristics, and transmission loss. The fibers presented exhibit no crosstalk and it is possible to use them together with other multiplexing methods like CWDM or DWDM. Dedicated fanin/ fan-outs have been created in order to make immediate use in industry possible. The hole-assisted 19-core fiber with single-mode cores is being presented for the very first time.
In this paper we present possibilities of tuning spectrum of supercontinuum with the use of temperature change. Our study is based on the information about the role of dispersion characteristics in the process of nonlinear effects generation in nanosecond pulse regime. We obtain tunable spectrum effects in microstructured fiber and we show how to optimize its properties. Our experimental results showing nonlinear effects generation in fiber pumped in normal and anomalous dispersion regime enables to determine how the nonlinear effects depend on temperature changes. We show that even small changes of dispersion characteristic of microstructured fibers enable to obtain significant modification of generated spectra when four wave mixing is dominant effect. Controllable generation of tunable supercontinuum can be used in numbers of potential applications such as diagnostics and measurement systems.
It is well known that the Young interference experiment is the fundamental setup to combine two beams and to construct the phase modulated light. Moreover, homodyne phase demodulator is based on signal decoding in back Fourier focal plane using bicell photodetector (B-PD). On the above base, we propose a novel experimental approach to the signals demodulation by using the optical interferometer which operates in homodyne mode, combined with liquid crystal spatial light modulators operating both phase as speckle modulator. Dynamic phase changes between the two beams can be controlled by monopixel liquid crystals cell placed in one branch of the interferometer. A phase modulation effect in a signal arm of interferometer is observed as a dynamic shift of the speckle pattern. Simple arithmetic combination of signals from B-PD placed in speckle pattern plane is only one necessary numerical manipulation to obtain exactly phase difference. Concept of signals demodulation in the Fourier focal plane can be only used for exactly defined geometrical (B-PD as well as Young interferometer) and physical parameters (polarization, wavelength). We optimize the setup geometry to obtain extremely high measurement resolution. In this paper we focus on the principles of operation of each part of the system as well as discussion their requirement in order to increase the signal to noise ratio.
We show a new possibility for extension of supercontinuum spectrum generated in photonic crystal fibre towards the UV light. To do so, we use four wave mixing and cross phase modulation nonlinear effects as well as interaction of fundamental mode with higher order modes. It is shown that a few modes operation and proper dispersion profiles of these modes give a possibility of nonlinear effects optimization and thus improvement of UV generation. The advantage of presented solution is the employment of cascaded nonlinear interactions inside one microstructured fibre.
We investigate a change of dispersion characteristic in a series of nonlinear photonic crystal fibers caused by slight
variation of structural parameters, i.e. an air-hole diameter and a lattice constant. Each fiber has been fabricated to have
zero dispersion wavelength close to 1064 nm. The generation of supercontinuum is also demonstrated with the use of
fabricated fibers pumped at the wavelength of 1064 nm. We provide the comparison of SC evolution and different
nonlinear effects in fabricated fibers. Due to the extensive content of experimental research performed for different
photonic crystal fibers, our paper indicates how to design a fiber to be tolerant to the fabrication inaccuracies and to
obtain the desired supercontinuum characteristics.
In this work we would like to present the results of low loss coupling of a novel soft glass fiber for super continuum generation with standard single mode fiber by a filament splicing method. For our experiment we used an all solid soft glass microstructured fiber (MSF) made from a composition of F2 lead-silicate glass and NC21 borosilicate glass. The structure and material properties of the fiber were optimized to achieve all normal dispersion (ND) flattened around 1560 nm, which offers two general advantages for supercontinuum generation. The ND supercontinuum avoids soliton dynamics, hence it is less sensitive to pump laser shot noise and has larger degree of coherence than supercontinuum in the anomalous dispersion range. Furthermore flattening around 1560 nm indicates optimal supercontinuum pump wavelength, which is readily available from erbium doped femtosecond fiber lasers. Using Vytran splicing station (GPX3400) we were able to achieve repeatable splice loss between a standard fused-silica single mode fiber (SMF28) and the low-melting-temperature soft glass MSF as low as 2.12 dB @1310 nm and 1.94 dB @ 1550 nm. The developed very low loss splicing technology together with the above mentioned all solid soft glass MSF advantages give very promising perspectives for commercial applications.
Phase sensitivities of temperature, longitudinal strain or pressure, are very important fiber features in sensing and
telecommunication applications. The most common ways to modify such sensitivities are to change the material
properties (by adjusting the core doping level) or employ microstructured fibers (which properties strongly depend on the
cross-section geometry). We decided to investigate strain sensitivity influenced by effective mode field area and mode
field diameter as clear consequence of fiber cross-section geometry.
In this paper we present the results of a three dimensional numerical analysis of the correlation between the fiber mode
field diameter and its longitudinal strain sensitivity. Both conventional and microstructured (commercially available and
custom designed) fibers are investigated. Furthermore we compare the theoretical results with experimental data. To
measure fiber sensitivity we developed a dedicated all-fiber Mach-Zehnder interferometer which enables the
measurement of strain induced phase changes in various fiber types (including conventional and microstructured fibers).
As a conclusion of our work we present relationship between strain sensitivity and MFD .
Fundamental properties of pure silica microstructured fibres (MSFs) can be determined by their geometrical crosssection design. Investigation of nonlinear effects was widely evaluated in diverse types of MSFs with exactly defined dispersive properties. Proper design of Zero Dispersion Wavelength (ZDW) strongly influences generation of nonlinear processes resulting especially in supercontinuum generation (SC). ZDW shift to short wavelengths together with high nonlinearity (small effective mode area) can be obtained by dramatic decrease of microstructured fibre pitch and increase of air-filling ratio. Fibre geometry must be properly scaled preserving technological tolerances to obtain precisely defined position of ZDW near visible range. Additionally, higher air-filling ratio results in multimode guiding regime. Therefore, in the paper we present studies of novel type of fibre geometry with ZDW near visible range together with endlessly single mode propagation regime. Chromatic dispersion measurements and ZDW analysis are performed with use of interferometric method. Presented MSFs series (the same structure type, but different ZDW position) is manufactured by stack and draw method. Proposed MSFs geometry enables fabrication of desired chromatic dispersion characteristic while respecting all technological tolerances, which is very difficult in case of manufacturing typical photonic crystal fibres for supercontinuum generated with 780 nm wavelength pulses from titanium-sapphire laser. Additionally, proposed endlessly single mode operation provides high quality white light output beam, simultaneously with stable and flat SC source. Paper also reports on the SC generation with pumping in the anomalous and normal side of chromatic dispersion with femtoseconds and picoseconds pulses.
Nonlinear phenomena in microstructured fibers (MSFs) is defined by dispersive properties of a fiber. Zero dispersion wavelength (ZDW) and pump source wavelength play an important role in estimating the nonlinear effects and thus are subject of wide investigations. Multiple nonlinear processes like: four wave mixing (FWM), cross phase modulation (XPM), cannot be very efficient without phase matching which is achieved when a fiber is pumped in anomalous dispersion region. On the other hand, other nonlinear processes, such as self-phase modulation (SPM) and Raman scattering (RS), profit from pumping fiber in normal dispersion region. Thus the efficiency of supercontinuum (SC) generation in a fiber is dependent on its chromatic dispersion properties, which can be tailored by the proper fiber geometry design, and by the pump source wavelength. In our paper we present experimental analysis of SC generation obtained for a series of nonlinear MSFs. Our fibers have different ZDW and therefore when pumped by the same pump source, different nonlinear effects contribute to the SC generation. We analyze and explain the influence of ZDW on nonlinear effects. Comparisons of nonlinear interactions for fibers pumped in anomalous and normal dispersion regimes are provided. In our silica MSFs an ultra-short UV radiation was obtained by nonlinear processes estimation. We provide experimental analysis of MSFs geometrical parameters influence on UV conversion efficiency. Our studies present effective SC generation in near infrared, visible and UV ranges. Unique information about the influence of MSFs geometry on UV generation efficiency gives possibility to increase its application potential.
We present possibility of demodulation signals with different types of modulation. Our setup gives possibility to obtain
high accuracy and precision of measurements. We explain how to optimize the setup to obtain optimum condition to
phase demodulation for signals with different types of modulation. Real time phase measurements and stable working
conditions are provided experimentally. Thermal stabilization and errors analysis based on geometrical and physical
setup parameters is demonstrated and optimized, too. Our phase demodulation method is effective and simple in opposite
to other phase decoding methods with are overloaded by digital signal processing steps.
Sensitivity of optical fibers to the temperature, longitudinal strain or pressure, is a very important feature in many applications, such as sensors or telecommunication. The most common way to modify (depending on application - either mitigate or strengthen,) this sensitivity is changing the fiber material properties by appropriate glass doping or by employing appropriate microstructure in the fiber. In some cases the precise adjustment of a doping level and sophisticated design of air-holes arrangement is needed to obtain required features of the fiber. In this paper, for the first time, to the best of our knowledge, we report the investigation of the mode area and geometry influence on the fiber temperature and mechanical sensitivities. To do so, we engaged a dedicated all-fiber interferometer which enables the measurement of the temperature and longitudinal strain sensitivities of different fiber types, including conventional and microstructured fibers with different core diameters.
Numerical Aperture (NA) is one of the fundamental properties of optical fibres. It determines the ability of efficient light coupling into the fibre and low loss splicing with other fibres. NA is essential when novel fibres are manufactured. Moreover, dispersive behaviour of geometrical guiding mechanisms, existing in microstructured fibres, is completely different comparing with material guiding mechanisms of classical fibres. Therefore we constructed measurement system, for characterization the dispersive properties of NA of specialty microstructured fibres in broad wavelength range. Additionally, presented setup can be applied for measurements refractive index of different materials (including highly absorbing) filling the holes of microstructured fibre in broad wavelength range.
In this paper we present the experimental comparison of mechanical and temperature sensitivities of Mach-Zehnder
interferometer with replaceable FC connectorized sensing fibre arm, such as: off-the-shelf endlessly single mode
microstructured fibre (MSF) or standard telecom single mode fibre. Experimental results clearly show reduced crosssensitivity
to temperature of studied MSF compared with standard doped core fibre. Additionally, microstructured fibre
Mach-Zehnder interferometer with standard FC receptacles allows using different fibres as sensors with the same device.
Moreover, investigated interferometer consumes in total extremely low electric power (< 20 mW) and VCSEL as the
light source.
Microstructured fibres (MSFs) reveal unique properties including endlessly single-mode operation from ultraviolet
to infrared wavelengths, very high birefringence or nonlinearity, very large or very small effective mode field area,
and many others. The size, shape and the location of the air holes allow for tailoring MSF parameters in a very wide
range, way beyond the classical fibres, what opens up the possibilities for various applications. Due to their
advantages MSFs obtain growing attention for their perspectives in sensing applications. Different MSF sensors
have already been investigated, including interferometric transducers for diverse physical parameters. Until now,
there have not been any publications reporting on the sensing applications of MSF Mach-Zehnder interferometers,
targeting the mechanical measurements of vibrations, dynamic or static pressure, strain, bending and lateral force.
Moreover, a critical feature opening the prospective of optical fibre transducer to successfully accomplish a
particular sensing task remains its cross-sensitivity to temperature. Studied MSF is made of pure silica glass in the
entire cross-section with a hexagonal structure of the holes. Consequently, there is no thermal stress induced by the
difference in thermal expansion coefficients between the doped core region and the pure silica glass cladding, in
contrast to standard fibres.
In this paper we present the experimental comparison of mechanical and temperature sensitivities of Mach-
Zehnder interferometer with replaceable FC connectorized sensing fibre arm, such as: off-the-shelf endlessly single
mode MSF or standard telecom single mode fibre. Experimental results clearly show very low cross-sensitivity to
temperature of studied MSF compared with standard fibre. Additionally, microstructured fibre Mach-Zehnder
interferometer with standard FC receptacles allows using different fibres as sensors with the same device. Moreover,
investigated interferometer consumes in total extremely low electric power (< 20 mW) due to the implementation of
exceptionally effective data analysis electronics and VCSEL as the light source.
Dispersion characteristics are the fundamental properties of microstructured fibres (MSFs) with respect to the nonlinear
applications. The changes of fibre dispersion may strongly influence the whole chain of diverse nonlinear effects
resulting in supercontinuum generation (SG). Transferring the experience from the topics related to tailoring different
properties of MSFs to investigate the potential design freedom of dispersion opens novel possibilities of building the
customized, all-fibre broadband and bright light sources.
The silica nonlinear microstructured fibres, as presented in this paper, become compatible with standard fibre
components and technologies (e.g. splicing, connectorization etc).
Supercontinuum generated in a small-core MSF is a very interesting nonlinear phenomenon from application-oriented
point of view. A development of tailored dispersion of highly non-linear silica MSF offers us the possibility of
constructing a customized broadband light source.
Therefore, in the paper we present a theoretical and experimental investigation of dispersion characteristics of several
different MSFs. Our studies are leading to the development of adapted dispersion properties, allowing construction of
customized supercontinuum sources. All fibre, white light interferometry set-up, resulting in extremely high precision
measurement of chromatic dispersion, is demonstrated, together with fully computer controlled fringe pattern analysis.
Constructed set-up permitted comparison of chromatic dispersion measurements of microstructured fibres with modified
fibre cross-section dimensions during the production process. High correlation between modelling and measured data
gives possibility to control dispersion level in manufacturing process. Additionally, precisely designed and measured
chromatic dispersion, especially around the zero dispersion wavelength, enables superior estimation of MSF nonlinear
effects.
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