Design of A CWDM OADM for Fiber Optical Communication Network

A CWDM is proposed for fiber optic communication networks. The OADM is designed based on SOI structure. The scheme for CWDM optical signal protection is presented.

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.

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.

Flipped-Exponential Nyquist Pulse Technique to Optimize PAPR in Optical Direct-Detection OFDM Systems

In this paper, we describe a novel technique based on the flipped-exponential （FE） Nyquist pulse method for reducing peak-to-average power ratio （PAPR） in an optical direct-detection orthogonal frequency-division multiplexing （DD-QFDM） system, The technique involves proper selection of the FE Nyquist pulses for shaping the different subcarriers of the OFDM. We apply this technique to a DD-OFDM transmission system to significantly reduce PAPR. We also investigate the sensitivity of a received OFDM signal with strong nonlinearity in a standard single-mode fiber （SMF）.

Impacts of operational parameters on nonlinear polarization rotation-based passively mode-locked fiber laser

The operational parameters including the polarization controlling and the pump power in a nonlinear polarization rotation-based passively mode-locked fiber laser are studied in this paper.The carrier rate equations of the activated erbium-doped fiber are first employed together with the nonlinear Shro¨dinger equations to reveal the relation between the operational parameters and the output state of the passively mode-locked fiber laser.The numerical and experimental results demonstrate that the output state of the mode-locked laser varies with the polarization controlling and the pump power.The periodicity of the polarization controlling is observed.With given pump power,there exists a set of polarization controlling under which the ultra-short pulse can be generated.With given polarization controlling,the mode-locked state can be maintained generally except for some particular values of pump power.Three shapes of the output optical spectra from the fiber cavity can be identified when the pump power changes.The results in this paper provide a comprehensive insight into the operation of the nonlinear polarization rotation-based passively mode-locked fiber laser.

Optical 64QAM-OFDM Transmission Systems with Different Sub-Carriers

In this paper, the transceiver performance of optical 64QAM-OFDM signals with different sub-car- riers is studied. Firstly, we build a 40Gbit/s optical coherent 64QAM-OFDM transmission system. 64QAM-OFDM optical signals with 16, 32, 64, 64, 128, 256 and 512 sub-carriers are transmitted over 100 km single mode fiber (SMF). Then, the optical spectrum diagrams before and after transmission, the bit error rate (BER) and constellation diagrams of received signals were compared. The simulation results show that, with the number of sub-carriers increasing, the value of PAPR will gradually increase and the quality of the received optical signals will deteriorate. Moreover, with the number of sub-carriers increasing, the computational complexity will increase when digital signal processing (DSP) is used. Therefore, we should choose the optimal number of sub-carriers, and the PAPR influence and BER are also considered for achieving effective transmission.

Review of In‑Vehicle Optical Fiber Communication Technology

With the continuous development of automotive intelligent networking and autonomous driving technologies,the number of in-vehicle electronic systems and applications is increasing rapidly.This change increases the amount of data to be transmitted in the vehicle and puts forward further requirements of higher speed and safety for in-vehicle communication.Traditional vehicle bus technologies are no longer sufficient to meet today’s high-speed transmission requirements,in which copper cables are used extensively,resulting in serious electromagnetic interference(EMI).Vehicle optical fiber communication technology,besides greatly improving the data transmission rate,has the advantages of anti-EMI,reducing cable space and vehicle mass.This paper first presents the motivation of applying vehicle optical fiber communication technology and reviews the development history of vehicle optical fiber communication technology.Then,the paper researches the devel-opment trend of automotive electrical and electronic architecture(EEA),from distributed EEA to domain centralized EEA and zone-oriented EEA.Based on the discussion of the development trend of automotive EEA,an EEA based on vehicle optical fiber communication technology is proposed.Finally,the key points and future directions of vehicle optical fiber communication technology research are highlighted,including vehicle multi-mode optical fiber technology,vehicle optical fiber network protocol,and topology.

4.096 Tbit/s multidimensional multiplexing signals transmission over 1000 km few mode fiber

We experimentally transmit eight wavelength-division-multiplexing(WDM)channels,16 quadratic-amplitude-modulation(QAM)signals at 32-GBaud,over 1000 km few mode fiber(FMF).In this experiment,we use WDM,mode division multiplexing,and polarization multiplexing for signal transmission.Through the multiple-input-multiple-output(MIMO)equalization algorithms,we achieve the total line transmission rate of 4.096 Tbit/s.The results prove that the bit error rates(BERs)for the16QAM signals after 1000 km FMF transmission are below the soft-decision forward-error-correction(SD-FEC)threshold of2.4×10^(-2),and the net rate reaches 3.413 Tbit/s.Our proposed system provides a reference for the future development of high-capacity communication.

PIM Application Based on Client/Server Architecture

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.

Optical PPM-CDMA Communication System with Optical Hard Limiter

An optical PPM CDMA communication system with an optical hard limiter in front of the correlator of a receiver is proposed in order to reduce multi user interference. The performance of the system is evaluated when the effects of both multi user interference and photo detector shot noise are considered. An upper bound on the bit error rate is derived. The comparison of the performance of the above receiver with that of the optical PPM CDMA system without an optical hard limiter is made. Simulation results show that the performance of the system with an optical hard limiter is superior to that of the conventional one.

Capacity and Flexibility Improvement of Traffic Aggregation for Fixed 5G:Key Enabling Technologies,Challenges and Trends

As the emergence of various highbandwidth services and the requirements to support 5G/Wi-Fi 6 wireless networks,the next generation fixed networks,i.e.F5G,are expected to be realized in the 5G era.F5G is endowed with new characteristics,including ultra-high bandwidth,all-optical connections and optimal service experience.With the prospect of optical-to-everywhere,optical technologies are used for mobile front-haul,mid-haul,and back-haul.Optical access networks would play an important role in F5G to support radio access network and fixed access network.Low-latency PON is a key for cost effective-haul traffic aggregation.In terms of signal transmission,intensity modulation directdetection(IM-DD)is a promising scheme due to its simple architecture.The fundamental challenge associated with direct-detection is the disappearance of the transmitted signal’s phase.In access network,the flexibility and low latency are the two key factors affecting service experience.In this article,we review the evolution of PONs and the challenges of current PONs in detail.We analyze key enabling digital signal processing(DSP)techniques,including detection linearization for direct-detection and simplified coherent detection,adaptive equalizers,digital filer enabled flexible access network and low-latency inter-ONU communications.Finally,we discuss the developing trends of future optical access networks.

Exploiting the Faster-Than-Nyquist Concept in Wavelength-Division Multiplexing Systems Using Duobinary Shaping

This paper begins with Nyquist wavelengthdivision multiplexing （WDM） and then introduces fasterthanNyquist. In fasterthanNyquist a certain amount of intersymbol interference （ISI） is accepted, which violates the fundamental principle of Nyquist WDM. This results in muchrelaxed transceiver bandwidth and simpler spectral design. However, in fasterthanNyquist, implementation complexity is shifted from the transmitter side to the receiver side. Therefore, successful application of fasterthanNyquist depends on innovation in the receiver structure. In this paper, we discuss the guidelines for implementing suboptimum, lowcomplexity receivers based on fasterthanNyquist. We suggest that duobinary shaping is a good technique for trading off achievable spectral efficiency, detection performance, and implementation complexity and might be preferable to Nyquist WDM. Experiments are conducted to verify robustness of the proposed technique.

Blind Nonlinearity Equalization by Machine-Learning-Based Clustering for QAM-Based Quantum Noise Stream Cipher Transmission

In quantum noise stream cipher(QNSC)systems,it is difficult to compensate fiber nonlinearity by digital signal processing(DSP)due to interactions between chromatic dispersion(CD),amplified spontaneous emission(ASE)noise from erbiumdoped fiber amplifier(EDFA)and Kerr nonlinearity.Nonlinearity equalizer(NLE)based on machine learning(ML)algorithms have been extensively studied.However,most NLE based on supervised ML algorithms have high training overhead and computation complexity.In addition,the performance of these algorithms have a lot of randomness.This paper proposes two clustering algorithms based on Fuzzylogic C-Means Clustering(FLC)to compensate the fiber nonlinearity in quadrature amplitude modulation(QAM)-based QNSC system,including FLC based on subtractive clustering(SC)and annealing evolution(AE)algorithm.The performance of FLC-SC and FLC-AE are evaluated through simulation and experiment.The proposed algorithms can promptly obtain suitable initial centroids and choose optimal initial centroids of the clusters to achieve the global optimal initial centroids especially for high order modulation scheme.In the simulation,different parameter configurations are considered,including fiber length,optical signal-to-noise ratio(OSNR),clipping ratio and resolution of digital to analog converter(DAC).Further-more,we measure the Q-factor of transmission signal with different launched powers,DAC resolution and laser linewidth in the optical back-to-back(BTB)experiment with 80-km single mode fiber.Both simulation and experimental results show that the proposed techniques can greatly mitigate the signal impairments.

Study on the DOP of Output Pulse in Optical Fiber Transmission Systems

In this paper the expression of the output pulse Stokes vector is derived based on the Jones matrix model proposed by A.Orlandini et al. The basic properties of degree of polarization (DOP) for output pulse are investigated.

Low-resolution optical transmission using joint shaping technique of signal probability and quantization noise

In this paper,we propose and experimentally demonstrate a joint shaping technique to improve the performance of a lowresolution transmission system for the first time,to the best of our knowledge.The joint shaping technique combines probabilistic shaping(PS)and error feedback noise shaping(EFNS).In the 40-Gbaud intensity-modulation direct-detection(IM/DD)experimental transmission system,a bit-error-rate(BER)of 3.8×10^(-3)can be achieved easily with the joint shaping at the physical number of bits(PNOB)of 3.In the 30-Gbaud dual polarization(DP)coherent experimental transmission system,a BER below 1×10^(-3)is easily obtained with a 3-bit quantizer by using joint shaping.The optimization of the shaping degree is also analyzed.

An Approach to a Method of Construction of (F, K, 1) Optical Orthogonal Codes from Block Design

F, K, 1) Optical orthogonal codes (OOC) are the best address codes applied to optical code division multiple access (OCDMA) communication systems, but the construction of the codes is very complex. In this paper, a method of construction of the OOC from block design is discussed and a method of computer aid design is presented, by which we can construct desired (F, K, 1) OOC easily.

Novel iteration-free blind phase noise estimation for coherent optical OFDM

We propose a novel iteration-free blind phase noise estimation scheme for coherent optical orthogonal frequency division multiplexing （CO-OFDM） systems. In the new algorithm, the cost function is selected as the similar expression with real and imaginary parts as that in the modified constant modulus algorithm, and the new cost function is derived under some assumptions, where it is infinitely approximated by the sine and cosine functions. By means of the analytical formula of the cost function, the initial coarse common phase error can be obtained with only some samples, where the algorithm avoids computational complexity of conventional blind phase noise compensation scheme. In CO-OFDM systems with high-order modulation format （32 quadrature amplitude modulation） and narrow linewidth lasers, it is proved by the simulation results that the nhase noise can be effectively compensated with the proposed blind estimation method.

Gaussian pulse transmission over ultra-high PMD fiber

Experiment was conducted to study Gaussian pulse transmission over ultra-high PMD fiber. Gaussian pulse is broken into a series of deformed pulses when it transmits over ultra-high PMD fiber. It is indicated that the walk-off deformed pulses were caused by ultra-high PMD. Transmitted experiment has been done using fiber with PMD coefficient 237.95ps/km1/2. The result of the experiment is consistent with the simulated one.

Study of Temporal Thermal Response of Microfiber Bragg Grating

Fiber Bragg grating has been successfully fabricated in the silica microfiber by the use of femtosecond laser point-by-point inscription.Temporal thermal response of the fabricated silica microfiber Bragg grating has been measured by the use of the CO_(2) laser thermal excitation method,and the result shows that the time constant of the microfiber Bragg grating is reduced by an order of magnitude compared with the traditional single-mode fiber Bragg grating and the measured time constant is〜21 ms.