With the development of coherent optical communication systems, the optical communication networks are becoming more dynamic and complex. The optical signals in communication networks are vulnerable to various impairments. Therefore, optical performance monitoring (OPM) is essential for optical networks, which ensures the robustness of the networks. Real-time chromatic dispersion (CD) monitoring is the basis for the compensation of CD induced transmission impairment. Therefore, to enable the high quality-of-service of reliable optical networks, it is essential to implement accurate CD monitoring for fiber optical transmission link. In this paper, we present a blind CD estimation method in conjunction with artificial neural network (ANN) for polarization division multiplexing (PDM) coherent optical communication systems. The CD monitoring range is set from 1340ps/nm to 9380ps/nm with step of 1340ps/nm. We experimentally demonstrate the proposed method in PDM quadrature phase-shift keying (QPSK), PDM 16 quadrature amplitude modulation (16-QAM) and PDM 64-QAM systems. The experiment results in our scheme show that CD values can be estimated successfully. The root-mean-square errors (RMSEs) of CD monitoring for 112Gbps PDM QPSK, 112Gbps PDM 16-QAM and 120Gbps PDM 64-QAM are 3.79ps/nm, 7.57ps/nm and 9.68ps/nm respectively.
A smart cushion based on single-mode-fiber-multimode-fiber-single-mode-fiber (SMS) with core-offset splicing, which can simultaneously realize human vital signs monitoring and activity monitoring, is proposed and experimentally demonstrated. The SMS structure is sandwiched between a piece of fiberglass mesh and a polyvinyl chloride (PVC) layer and then embedded in a common home or office cushion, which is the component of the proposed cushion. When people sit on the cushion placed on a chair, micro-strain induced by human activity including respiration, heartbeat and body movement will change the output light intensity of the fiber structure. By signal processing algorithms including filtering, fast Fourier transform (FFT) and feature extraction, the respiration rate (RR) and heartbeat rate (HR) can be obtained and human activity state on the cushion including nobody state, movement state and normal state can be judged. Furthermore, the performances of two memory foam cushions with different thicknesses are compared and proven to be both available. Such a smart portable cushion can realize real-time, noninvasive and highly sensitive monitoring of vital signs and activities within the accuracy of one second, especially for the elderly in nursing homes and office workers.
A novel fiber-optic sensor based on all-fiber up-taper-core-offset-up-taper structure is proposed and investigated. The sensor is fabricated by splicing a large core offset between a pair of up tapers in the single mode fiber (SMF). This structure is sensitive to refractive index (RI) and strain with low cost and easy fabrication.
A novel mode interferometer for simultaneous strain and temperature measurement is proposed, which is based on Mach-Zehnder interferometer (MZI) realized by splicing a short section Er-Doped fiber (EDF) between two sections of single mode fibers (SMF) with core-offset technique. The structure is compact and easy to fabricate. A strain sensitivity of 0.0247 dB/με and a temperature sensitivity of 0.2225dB/℃are achieved experimentally.
The transmission rates of the next generation intelligent optical networks are high, and the use of dense wavelength division multiplexing and a reconfigurable optical add-drop multiplexer makes the traditional optical signal-to-noise ratio (OSNR) monitoring techniques unsuitable. Hence, we investigated the OSNR monitoring method based on the nonlinear effect of four-wave mixing (FWM), which applies to the next generation intelligent optical networks. Due to FWM in a highly nonlinear fiber, a converted wave is generated and its power is dependent on the OSNR of the input signal. Two scenarios are studied, single-pump and orthogonal-polarized dual-pump. Under the condition of the given fiber length and the appropriate pump power, the monitoring ranges of OSNR could be extended to 23 and 30 dB for single-pump and orthogonal-polarized dual-pump, respectively.
A flexible and efficient channel bandwidth assignment is highly required for next optical generation networks. Among various techniques to enhance the wavelength routing capability, wavelength conversion plays an important role on improving network reconfigurability. In this paper, we experimentally demonstrate a sub-band wavelength conversion of a wide-band optical orthogonal frequency-division multiplexing (OFDM) signal based on four-wave mixing (FWM) using high-nonlinear fiber (HNLF) to solve the spectrum conflicts in the flexible coherent optical OFDM (CO-OFDM) networks. Combining with the wavelength selective switch (WSS) in a reconfigurable optical add/drop multiplexer (ROADM), some spectrum-overlapped sub-bands are successfully relocated to ‘seamlessly’ form a new wide-band signal, which efficiently eliminates the spectrum conflicts, and achieves a good spectral efficiency.
We propose and experimentally demonstrate a novel loading scheme to improve the maximum system power budget for orthogonal frequency division multiplexing access-passive optical network (OFDMA-PON). For the downstream traffic, optical network units (ONUs) with asymmetric distribution fiber lengths are paired together, and information for the paired ONUs is loaded into the same OFDM signal by forward error correction loading combined with bit and power loading scheme. Power budgets of ONUs with long distribution fiber lengths can be improved at the cost of the power budget degradation of ONUs with short distribution fiber lengths, while maintaining the data rates for both ONUs. Besides, the total number of subcarriers used in downstream OFDM signal remains unchanged. A proof-of-concept experiment is performed to demonstrate the feasibility of the proposed scheme. A maximum of 80 km transmission and a 1∶128 split ratio is achieved by the scheme, which improves the maximum system power budget by ∼4 dB than traditional methods.
Dispersion compensation with a wavelength selective switch-based reconfigurable optical add/drop multiplexer is experimentally realized in an optical transport network testbed. Through considering various dispersion compensation scenarios (including different fiber types, different wavelength ranges, and single- and multi-channel cases), we show that without deploying new optical components, a wavelength selective switch can successfully compensate for chromatic dispersion in its dispersion control range.
In this paper, we propose a novel bandwidth-flexible reconfigurable optical add/drop multiplexer (ROADM) architecture
based on coherent optical-orthogonal frequency division multiplexing (CO-OFDM) technology. The bandwidth-flexible
ROADM architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a
highly spectrum-efficient manner, thereby providing a fractional bandwidth service. We simulate and compare the
blocking performance of bandwidth-flexible ROADM with and without wavelength converters. It is found that
wavelength converter could obviously improve the blocking performance of bandwidth-flexible ROADM with different
frequency grid. Moreover, the conversion ratios are calculated for different load and channel spacing. Based on the
analysis of conversion ratio, we could make an appropriate configuration of wavelength converters in bandwidth-flexible
ROADM.
Arbitrarily-shaped ultrashort pulse waveforms could be synthesized with optimized high-resolution zero-dispersion pulse
shaping system. The system and optimized parameters are analyzed and discussed. It is shown that the optimized pulse
shaping system could resolve frequency components of ultrashort pulse and avoid spatial shaping of individual
frequency components. The specified shaped pulses are generated through our optimized system, which can potentially
improve the performance of optical wireless communication system.
A novel configuration of semiconductor all-optical switch based on Fabry-Perot cavity is proposed. The principle and
structure of this kind of all-optical switch are presented. We also analyze the performance of the all-optical switch. The
wavelength selectivity of the all-optical switch changed with the power of the control light is given. We discuss its
viable application in the future optical switching.
Optical Burst Switching (OBS) functioning as an IP traffic aggregator at the edge of the Optical Transport Network is provided to enhance network flexibility and efficiency. This paper gives an overview of OBS node and the benefits it will bring about. It explains how an OBS node is modeled and simulated under different traffic conditions and gives the effect of Fiber Delay Line (FDL) in OBS node. Finally, the simulation results are presented and the performances of OBS node are evaluated.
In this paper, the process of fabricating coarse wavelength division multiplexing (CWDM) passive components using Fused Biconic Taper (FBT) technology is introduced. The performances and specifications of CWDM passive components are measured and reported. And we compare the performances and cost of this kind of CWDM module with the performances and cost of CWDM module based on thin-film-filter technology and dense wavelength division multiplexing (DWDM) module.
In this paper, we presented the results of bend loss measurements for single-mode optical fiber over wide bend radius 1mm ~ 8mm and wavelength 1530nm ~ 1565nm. The oscillations caused by the coupling between the whispering gallery mode propagating in the cladding and the buffer and the core guided fundamental mode was observed versus both bend radius and wavelength. And a good agreement between the experimental results and the theoretical numerical evaluation was obtained.
Using a spectrum-sliced device composed of two cascaded fiber Bragg gratings, a novel multiwavelength fiber light source is manufactured based on broadband amplified spontaneous emission from Er-doped fiber. Two channels incoherent light near 1550nm with FWHM of 0.23nm, 0.45nm, respectively, output power of above 1mW are obtained. Using this fiber amplifier light source, we transmit a 34Mb/s incoherent light signal over 10 Km single-mode standard fiber. The error floor level is less than 10-9.
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