Toward Low-Cost Flexible Intelligent OAM in Optical Fiber Communication Networks

Low-cost,flexible and intelligent optical performance monitoring and management is a key enabling technology for network quality guarantee,especially in the era of explosive growth of communication capacity and network scale.However,to the best of our knowledge,it is extremely challenging to implement real-time performance monitoring and operations,administration and maintenance(OAM) in a highly complex dynamic network.In this paper,we propose an innovative optical identification(OID) scheme that can realize both performance monitoring and some advanced OAM sub-functions.The basic concepts,applications,challenges and evolution directions of this OID tool are also discussed.

2.5 Gbit/s monolithic ICs for optical fiber transmitter and receiver in 0.35 μm CMOS process

2.5 Gbit/s monolithic integrated circuits （ICs） for optical fiber transmitter and receiver in 0.35 μm CMOS （complementary metal-oxide-semiconductor transistor） process are presented. The transmitter, which includes a 4： 1 multiplexer and a laser diode driver （LDD）, has four 622 Mbit/s random signals as its inputs and gets a 2.5 Gbit/s driving signal as its output; the receiver detects a 2.5 Gbit/s random signal and gets four 622 Mbit/s signals at the output. The main circuits include a trans-impedance amplifier （TIA）, a limiting amplifier, a clock and data recovery （CDR） unit, and a 1： 4 demultiplexer （DEMUX）. Test results prove the logic functions of the transmitter to be right, and the 10% to 90% rise and fall times of transmitter＇s output data eye diagram are 211.1 ps and 200 ps, respectively. The sensitivity of the receiver is measured to be better than 20 mV. The root mean square jitter of the DEMUX＇s output data is 15.6 ps and that of the clock after 1： 4 frequency dividing is 1.9 ps. Two chips are both applicable to 2.5 Gbit/s optical fiber communication systems.

Research and Progress of Service Driven Optical Switching Network in China

National R&D activities on optical switching networkare introduced. Optical switching network testbedswere established in China including 3T-net andOBS ring and mesh network test-bed with the supportof national '863' program. As an importantmodule in OPS network, a novel all-optical serialmulticast mode is discussed.

Equivalent Noise Models in Fiber Optical Communication Systems

An equivalent noise model of optical receiver amplifiers as shown in Fig.1 has been given in many fiber optical communication literatures. It is proved in this paper that this equivalent noise model is neither equivalent to the original one nor measurable. The main reason is that the position of the input impedance in this noise model is not the same with its in the typical noise model,but the same S vn , S in with the typical noise model are used. So the equivalent noise model above is wrong and is not fit to be taken into application.

All optical wavelength converter and its application in optical network

All optical network （AON） is a hot topic in recent studies of optical fiber communications. Key techniques in AON include optical switching/routing, optical cross connection （OXC）, all optical wavelength conversion （AOWC）, all optical buffering, etc. Opti- cal switching/routing is in fact wavelength switching/ routing. OXC and wavelength conversion （WC） are introduced into cross nodes so that a virtual wavelength path is established. With WC, communication route is formed only if there is unused wavelength in an individual segment link. The rate wavelength usage is thus greatly increased. The blocking rate of network can be reduced by adding WCs, especially for huge capacity multiple nodes ones. Therefore, WC has attracted much attention in basic research of optical communication and is used in some experimental networks.This dissertation studies all optic wavelength conversion and its application, with the contributions in the following five aspects.

Optimization of Spectral Inverters in Optical Fiber Communication Systems with Mid-Span Spectrum Inversion

In this paper, signal distortions caused by spectral inverters which are used in 10Gb/s optical fiber communication systems with mid span spectrum inversion in terms of dispersion shift fibers are analyed numerically. It is shown that there exist the optimal input signal power, fiber length and fiblter bandwidth for the spectral in verters. System transmission penalty can be minimized by optimizing these parameters.

Training-based symbol detection with temporal convolutional neural network in single-polarized optical communication system

In order to reduce the physical impairment caused by signal distortion,in this paper,we investigate symbol detection with Deep Learning(DL)methods to improve bit-error performance in the optical communication system.Many DL-based methods have been applied to such systems to improve bit-error performance.Referring to the speech-to-text method of automatic speech recognition,this paper proposes a signal-to-symbol method based on DL and designs a receiver for symbol detection on single-polarized optical communications modes.To realize this detection method,we propose a non-causal temporal convolutional network-assisted receiver to detect symbols directly from the baseband signal,which specifically integrates most modules of the receiver.Meanwhile,we adopt three training approaches for different signal-to-noise ratios.We also apply a parametric rectified linear unit to enhance the noise robustness of the proposed network.According to the simulation experiments,the biterror-rate performance of the proposed method is close to or even superior to that of the conventional receiver and better than the recurrent neural network-based receiver.

Application of the Spectrum Peak Positioning Technology Based on BP Neural Network in Demodulation of Cavity Length of EFPI Fiber Optical Sensor

An Extrinsic Fabry-Perot Interferometric (EFPI) fiber optical sensor system is an online testing system for the gas density. The system achieves the measurement of gas density information mainly by demodulating the cavity length of EF- PI fiber optical sensor. There are many ways to achieve the demodulation of the cavity length. For shortcomings of the big intensity demodulation error and complex structure of phase demodulation, this paper proposes that BP neural net-work is used to locate the special peak points in normalized interference spectrum and combining the advantages of the unimodal and bimodal measurement achieves the demodulation of the cavity length. Through online simulation and actual measurement, the results show that the peak positioning technology based on BP neural network can not only achieve high-precision demodulation of the cavity length, but also achieve an absolute measurement of cavity length in large dynamic range.

Polarization Jitters Caused by Fiber Nonlinearity in PM Optical Communication System

The phenomenon of polarization jitters caused by fiber nonlinearity is investigated. A general formula about the polarization jitter is concluded in polarization multiplexing (PM) system based on two orthogonal linear polarization states when the best polarization correction is used. A 100 Gb/s PM system based on NRZ code is investigated by simulation, and the Stocks parameter about polarization jitter and Poincare sphere diagrams are got for different power and phase difference of two orthogonal polarized light. The results show that the polarization jitters will be suppressed when the combined PM signal is the linear or circular polarization state.

Fiber Grating Ring Laser in All Optical Communication System

Erbium fiber grating ring laser (EFRL) witn an integrated travelling wave and low polarization mode noise is reported. Through modulated experiment of a successful 2.488 Gb/s RZ data, it is shown that the EFRL is a promising alternative to DFB lasers for high-speed transmission applications.

Design and Implementation of Optical Fiber Test Equipment

In order to meet the needs of the rapid development of optical fiber communication technology, combined with the thinking of the Internet of Things, a new idea of designing an optical fiber test equipment using Raspberry Pi is proposed. At the same time, the design of a multi-parameter measuring device for optical fiber signals based on Flask was completed.

Efficient stochastic parallel gradient descent training for on-chip optical processor

In recent years,space-division multiplexing(SDM)technology,which involves transmitting data information on multiple parallel channels for efficient capacity scaling,has been widely used in fiber and free-space optical communication sys-tems.To enable flexible data management and cope with the mixing between different channels,the integrated reconfig-urable optical processor is used for optical switching and mitigating the channel crosstalk.However,efficient online train-ing becomes intricate and challenging,particularly when dealing with a significant number of channels.Here we use the stochastic parallel gradient descent(SPGD)algorithm to configure the integrated optical processor,which has less com-putation than the traditional gradient descent(GD)algorithm.We design and fabricate a 6×6 on-chip optical processor on silicon platform to implement optical switching and descrambling assisted by the online training with the SPDG algorithm.Moreover,we apply the on-chip processor configured by the SPGD algorithm to optical communications for optical switching and efficiently mitigating the channel crosstalk in SDM systems.In comparison with the traditional GD al-gorithm,it is found that the SPGD algorithm features better performance especially when the scale of matrix is large,which means it has the potential to optimize large-scale optical matrix computation acceleration chips.

A survey of free space optical networks

Free Space Optical （FSO） networks, also known as optical wireless networks, have emerged as viable candidates for broadband wireless communications in the near future. The range of the potential application of FSO networks is extensive, from home to satellite. However, FSO networks have not been popularized because of insufficient availability and reliability. Researchers have focused on the problems in the physical layer in order to exploit the properties of wireless optical channels. However, recent technological developments with successful results make it practical to explore the advantages of the high bandwidth. Some researchers have begun to focus on the problems of network and upper layers in FSO networks. In this survey, we classify prospective global FSO networks into three subnetworks and give an account of them. We also present state-of- the-art research and discuss what kinds of challenges exist.

Combined Transmission Interference Spectrum of No Core Fiber and BP Neural Network for Concentration Sensing Research

To investigate wavelength response of the no core fiber（NCF）interference spectrum to concentration,a three-layer back propagation（BP）neural network model was established to optimize the concentration sensing data.In this method,the measured wavelength and the corresponding concentration were trained by a BP neural network,so that the accuracy of the measurement system was optimized.The wavelength was used as the training set and got into the input layer of the three layer BP network model which is used as the input value of the network,and the corresponding actual concentration value was used as the output value of the network,and the optimal network structure was trained.This paper discovers a preferable correlation between the predicted value and the actual value,where the former is approximately equal to the latter.The correlation coefficients of the measured and predicted values for a sucrose concentration were 1.000 89 and 1.003 94;similarly,correlations of0.999 51 and 1.018 8 for a glucose concentration were observed.The results demonstrate that the BP neural network can improve the prediction accuracy of the nonlinear relationship between the interference spectral data and the concentration in NCF sensing systems.

Combined optical fiber interferometric sensors for the detection of acoustic emission

A type of combined optical fiber interferometric acoustic emission sensor is proposed. The sensor can be independent on the laser source and make light interference by matching the lengths of two arms,so it can be used to monitor the health of large structure. Theoretical analyses indicate that the system can be equivalent to the Michelson interferometer with two optical fiber loop reflectors,and its sensitivity has been remarkably increased because of the decrease of the losses of light energy. PZT is powered by DC regulator to control the operating point of the system,so the system can accurately detect feeble vibration which is generated by ultrasonic waves propagating on the surface of solid. The amplitude and the frequency of feeble vibration signal are obtained by detecting the output light intensity of interferometer and using Fourier transform technique. The results indicate that the system can be used to detect the acoustic emission signals by the frequency characteristics.

Loading Localization by Small-Diameter Optical Fiber Sensors

Structural health monitoring(SHM)in service has attracted increasing attention for years.Load localization on a structure is studied hereby.Two algorithms,i.e.,support vector machine(SVM)method and back propagation neural network(BPNN)algorithm,are proposed to identify the loading positions individually.The feasibility of the suggested methods is evaluated through an experimental program on a carbon fiber reinforced plastic laminate.The experimental tests involve in application of four optical fiber-based sensors for strain measurement at discrete points.The sensors are specially designed fiber Bragg grating(FBG)in small diameter.The small-diameter FBG sensors are arrayed in 2-D on the laminate surface.The testing results indicate that the loading position could be detected by the proposed method.Using SVM method,the 2-D FBG sensors can approximate the loading location with maximum error less than 14 mm.However,the maximum localization error could be limited to about 1 mm by applying the BPNN algorithm.It is mainly because the convergence conditions(mean square error)can be set in advance,while SVM cannot.

Research on Additional Loss of Guidance Optical Fiber

The factors which cause additional losses of guidance optical fiber in wound state were analyzed.A mathematical model used to analyze the macro-bend losses in the cross region producing in the precision winding process was established.For an actual guidance optical fiber,the measured data of the fiber's additional losses under low temperature and the loss curves with radius were given in the paper.The simulation results were compared with the test data.It shows that the additional losses of optical fiber caused by bending and low temperature can meet the actual requirements of the fiber optical guidance system.The established model can be used to predict the change trend of fiber losses in the winding process with a certain tensile force.

FAST EVALUATION OF THE CHARACTERISTICS OF SINGLE-MODE OPTICAL FIBERS

This paper describes a method for fast engineering evaluation of the transmission characteristicsof single-mode optical fibers.A versatile microcomputer program is presented which can be utilized to ana-lyze mode field characteristics of single-mode fibers with arbitrary refractive index profiles.Our computationshows that the mathematical algorithm and the corresponding programs developeod in this paper are rela-tively simple and accurate enough for the engineenring design of single-mode fibers for optical communica-tion systems.

A Novel Packet Switch Node Architecture for Contention Resolution in Synchronous Optical Packet Switched Networks

Packet contention is a key issue in optical packet switch (OPS) networks and finds a viable solution by including optical buffering techniques incorporating fiber delay lines (FDLs) in the switch architecture. The present paper proposes a novel switch architecture for packet contention resolution in synchronous OPS network employing the packet circulation in FDLs in a synchronized manner. A mathematical model for the proposed switch architecture is developed employing packet queuing control to estimate the blocking probability for the incoming traffic. The switch performance is analyzed with a suitable contention resolution al-gorithm through the computer simulation. The simulation results substantiate the proposed model for the switch architecture.