Mechanism of SOA-based regenerative amplification of phase-noise degraded DPSK signals

Presented is dynamic analysis for SOA-based regenerative amplification (SORA) of phase-noise-degraded DPSK signals, which led to the first recent practical demonstration of a SORA. The modelling results agree with the experiment. The regeneration is achieved without wavelength conversion and/or using additional laser resources.     

SNR improvement of DPSK signals in a semiconductor optical regenerative amplifier

Signal-to-noise ratio improvement using a semiconductor optical regenerative amplifier (SORA) is characterized. It is demonstrated that for a noise-degraded return-to-zero differential phase-shift keying signal at 10 Gb/s the Q factor at the SORA's output is improved relative to its input for both the phase and amplitude noise cases. The Q-factor improvement is 1.6 dB in single-channel operation for the phase-noise only case and 0.55 dB for the amplified spontaneous emission noise-only case through the SORA.     

Bit error rate analysis of reduced-state Viterbi differentialdetection of M-ary DPSK signals

A tight upper bound or bit error rate (BER) is derived for approximate maximum likelihood differential detection (DD) implemented by the reduced state Viterbi algorithm (VA) known as RSVDD. The BER performance of RSVDD is compared with Viterbi DD (VDD) for M-ary DPSK in additive white Gaussian noise (AWGN) channels     

Highly efficient multichannel wavelength conversion of DPSK signals

This paper demonstrates a multichannel wavelength conversion of differential phase-shift-keyed (DPSK) signals using four-wave mixing in a highly nonlinear fiber. The wavelengths of three 10-Gb/s nonreturn-to-zero (NRZ) DPSK channels are simultaneously converted without incurring the cross-gain modulation penalty usually associated with on-off-keyed signals. A maximum conversion efficiency of 85% was achieved for both NRZ and return-to-zero DPSK signals.     

QD-SOA的四波混频及DPSK信号的异或逻辑研究

采用有限差分方法对量子点半导体光放大器(QD-SOA)中的四波混频(FWM)现象进行了研究。通过仿真计算,分析了多个参数对四波混频效率的影响。增强泵浦光功率、增大QD-SOA 的长度以及注入电流,四波混频效率明显增大。增大探测光功率以及泵浦光和探测光的波长间隔,四波混频效率均降低。基于四波混频效应实现了差分相移键控信号的异或逻辑操作,模拟得到了异或逻辑的时域和频域输出结果。在多个波长位置同时实现了异或逻辑,并对32 比特的序列异或操作进行了仿真研究,得到了异或逻辑的时序结果及眼图。     

Experimental demonstration of postnonlinearity compensation in a multispan DPSK transmission

We demonstrate significant performance improvement in 10-Gb/s multispan differential phase-shift keying transmissions by employing postnonlinearity compensation (PNC) for both dispersion-managed soliton and quasi-linear transmission. Measurements of timing misalignment tolerance as well as bandwidth requirement of the PNC unit show that the PNC technique is robust and practical, and can be easily extended to higher bit-rate transmissions.     

Cutoff rates of multichannel MFSK and DPSK signals in mobilesatellite communications

This paper studies the coded performance of multichannel MFSK and DPSK signalings in mobile satellite environments characterized by various kinds of multipath fading. Rician, Rician/lognormal, and a convex combination of Rician and Rician/lognormal or Rayleigh/lognormal distributions are used to model these communication channels. We investigate the minimum average signal-energy-to-noise ratio required to yield a cutoff rate that is greater than or equal to a given code rate. Also examined are system design issues such as the effect of quantization and metric conversion, the choice between binary codes and M-ary symbol codes, the optimization of the diversity order and the signal size, and the order of deinterleaving and diversity combining. Numerical examples are given to answer concerns raised by these issues     

Postdetection phase combining diversity for reception of faded DPSK signals

A new postdetection diversity scheme for the differential phase detection of faded DPSK signals is proposed. It combines the detector outputs in proportion to the squared value of each branch signal envelope. The average BER of pi /4-shift quaternary differential phase shift keying (QDPSK) with two-branch diversity is obtained through computer simulations assuming Rayleigh fading. It is found that the proposed diversity is superior to selection diversity by approximately 1.5 dB.<>     

Chirping techniques for enhancing the performance of SOA-based UWB over fiber systems: An experimental demonstration

A phaser-based processing technique was adopted in an UWB over fiber system employing SOA. The target is to simultaneously reduce the ASE noise impact and nonlinear effects inherent to optical amplification. Experimental results prove the effectiveness of chirping in terms of cross correlation and bit error rate.     

Time-frequency analysis of myoelectric signals during dynamic contractions: a comparative study

In this paper, we introduce the nonstationary signal analysis methods to analyze the myoelectric (ME) signals during dynamic contractions by estimating the time-dependent spectral moments. The time-frequency analysis methods including the short-time Fourier transform, the Wigner-Ville distribution, the Choi-Williams distribution, and the continuous wavelet transform were compared for estimation accuracy and precision on synthesized and real ME signals. It is found that the estimates provided by the continuous wavelet transform have better accuracy and precision than those obtained with the other time-frequency analysis methods on simulated data sets. In addition, ME signals from four subjects during three different tests (maximum static voluntary contraction, ramp contraction, and repeated isokinetic contractions) were also examined.     

Bit error rate of binary and quaternary DPSK signals with multipledifferential feedback detection

A differentially coherent detection scheme with improved bit error rate (BER) performance is presented for differentially encoded binary and quaternary phase shift keying (PSK) modulation. The improvement is based on using L symbol detectors with delays of 1, 2, . . ., L symbol periods and on feeding back detected PSK symbols. Exact formulas for the bit error probability are derived for the case that correct symbols are fed back. The effect of symbol errors in the feedback path on the BER is determined by computer simulations     

Bit error probabilities of NCFSK and DPSK signals in microcellular mobile radio systems

Microcellular mobile radio systems are studied where the desired signal has Rician statistics and the cochannel interferers experience Rayleigh fading. The probability density function of the signal-to-interference ratio is derived and is used to obtain the bit error probabilities of noncoherent frequency shift-keying and differential phase shift-keying signals.<>     

基于光纤四波混频DPSK系统相位噪声提取检测和抑制

差分相移键控(DPSK）在长距离光纤通信系统中有高接收机灵敏度、高频谱效率以及抗非线性效应方面的优势,最近受到广泛关注。在DPSK通信系统中,线性相位噪声和非线性相位噪声是影响系统性能的主要因素。研究了如何利用光纤四波混频（FWM）效应来监测和抑制相位噪声,降低相位噪声对DPSK通信系统的影响。结果表明利用光纤FWM效应产物可以检测相位噪声值,并且基于光纤饱和FWM效应全光限幅器可以有效地降低非线性相位噪声,提高了DPSK系统性能。该结果对研究高速全光通信有重要意义。     

稳定的单选、再生放大同步电路

为了得到高功率微微秒激光脉冲,可从锁模中选出微微秒单脉冲进行再生放大,然后进行多级放大。由于此系统比较复杂,除对光学元件及调正要求严格外,在电路方面,则要求提供多级氙灯稳定泵源及多个高精度同步开关。 对同步电路的要求:(1)与锁模激光脉冲同步,选出稳定的单脉冲,(2)单脉冲的注入必须在再生放大器反转粒子数最大状态,即与再生腔氙灯的点燃时间同步;(3)各普克尔盒之间应接一定要求启开与关闭。 同步电路的获得:     

Optical demodulation and amplification of FSK signals using AlGaAslasers

Stimulated Brillouin scattering is used as a narrowband amplifier to demodulate and amplify FSK signals at bit rates up to 250 Mbit/s. Gain of as much as a factor of 1000 is obtained for a pump over of 12 mW. Both pump and signal lasers are simple AlGaAs lasers     

Error probability of DPSK signals with intrachannel four-wave mixing in highly dispersive transmission systems

A semianalytical method evaluates the error probability of differential phase-shift keying signals with intrachannel four-wave mixing in a highly dispersive fiber link with strong pulse overlap. Depending on initial pulsewidth, the mean nonlinear phase shift of the system can be from 1 to 2 rad for signal-to-noise ratio penalty less than 1 dB. An approximated empirical formula, valid for penalty less than 2 dB, uses the variance of the differential phase of the ghost pulses to estimate the penalty.     

Improved-performance noncoherent weighted-coefficients diversity combiner for DPSK and NC-FSK signals in nonidentical Nakagami fading channels

It is well-known that noncoherent equal-gain combining (NC-EGC) is the simplest combining technique for noncoherent and differentially coherent communication systems. However, for nonidentical Nakagami-m channels (channels having nonuniform multipath intensity profile (MIP) and/or arbitrary non-integer fading parameters), the use of NC-EGC has three main disadvantages. First, its performance serves as a lossy upper bound to that of the optimum diversity combiner. Second, it results in complicated expressions for the system average error performance. Third, it incurs noncoherent combining loss (does not aid the use of diversity) at relatively low average signal-to-noise ratio (SNR). In this letter, we propose a modified version of the NC-EGC, which is a noncoherent combiner with weighting coefficients, to overcome the disadvantages of the conventional one. We show that this alternative combiner does provide improvements over the conventional N.C-EGC for all values of average SNRs, it does not incur any noncoherent combining loss, and it leads to a design of the receiver whose average error performance can be evaluated easily.     

Field demonstration of 565 Mbit/s DPSK coherent transmission systemover 176 km of installed fibre

Reports the results of a 565 Mbit/s coherent system field trial over 176 km of installed SM fibre. Fully automated endless polarisation control was employed using a novel method and error free operation was achieved with BER readings of better than 10^-13     

Investigation on parametric analysis of dynamic EMG signals by amuscle-structured simulation model

In the analysis of electromyographic (EMG) signals during dynamic movement, we have proposed an estimation algorithm for the time-varying parameters of an autoregressive model. The parameters correspond to less biased time-varying reflection coefficients. We determined the less biased estimation using a locally quasi-stationary model and named these parameters "k parameters." We estimated k parameters up to the fifth order for the surface EMG signals of a masseter muscle during rapid open-close movement of the lower jaw, a ballistic contraction, and fatigue. According to the results, the time courses of the k parameters displayed remarkable properties. In order to study the behavior of k parameters physiologically, we produced a muscle-structured simulation model based on anatomical and physiological data. The simulation results suggested that the behavior of the third parameter is related to the number of active motor units (MU's) at the shallow layer of a muscle. The detailed recruitment mechanism in terms of the MU's types has not yet been solved. Although further study is required, the parametric analysis using k parameters offers a new perspective for evaluation of muscle dynamics during several movements.     

Transmission of optical communication signals by distributed parametric amplification

For the first time, to the authors' knowledge, distributed parametric amplification (DPA), i.e., the use of a transmission fiber itself for parametric amplification of communication signals is proposed and demonstrated. To account for the inevitable fiber loss, solutions were derived for the distributed amplifier, with either one or two pumps: They are obtained in terms of confluent hypergeometric functions. Low-penalty DPA of a 10-Gb/s nonreturn-to-zero (NRZ) signal over a 75-km dispersion-shifted fiber (DSF), is demonstrated by using only 66.5 mW of pump power. Three adjacent channels have been simultaneously transmitted, with little penalty due to nonlinear crosstalk. It is experimentally verified that DPA requires less pump power than distributed Raman amplification (DRA), for similar power penalties.