基于腔内光放大器结构的光纤激光器噪声抑制方法

设计了一种将半导体光放大器耦 合于光纤激光器腔内的结构,以抑制光纤激光器的相对强 度噪声。基于半导体光放大器的增益饱和效应,将光纤 激光器在弛豫振荡峰处的相对强度噪声抑制了30 dB。更进 一步地,通过腔内的放大器结构使得放大器内部的光学 强度达到一个稳定态,最终使得激光器的频率噪声没有因 光放大器的加入而产生劣化。     

基于频谱分割的光码分多址接入系统实验研究

利用频谱分割技术进行了光码分多址接入 (OCDMA)系统传输实验。该实验的编解码器利用可调谐法 珀腔的不同自由谱域来区分不同用户 ,分析、测量了多址干扰对系统性能的影响 ,对系统中的光源、信道和编解码器的特性进行了讨论。测试表明 ,该接入系统在速率为 15 5Mb s ,MAI值是接收用户光功率 30倍的情况下 ,传输 11km普通单模光纤后 ,误码率优于 10 - 9。该系统实现简单 ,成本低 ,是全光接入的可选方案。     

开环光纤陀螺的光源强度噪声抑制方法研究

光纤陀螺系统中的宽带光源会产生光源相对强度噪声,要提高陀螺性能就必须对其加以抑制.由于开环光纤陀螺使用正弦波调制,相对强度噪声不能直接由陀螺信号相减消除.针对基于正弦波调制的开环光纤陀螺系统信号差分电路放大的特点,设计了一种实现强度噪声抑制的新算法.经实验验证,该算法有效,可使开环光纤陀螺的随机游走减小18%.     

数字化噪声的频谱分析

给出两种数字射频噪声的产生方法，即多频选择方式和PSK调制方式。分析用这些方法产生的射频噪声的频谱特性，并指出这些方法的应用场合。     

抑制掺铒光纤光源强度噪声的方法研究

目前,高精度光纤陀螺普遍采用掺铒光纤光源,对这种陀螺来说检测灵敏度受强度噪声限制.分析了强度噪声的特点及对陀螺的影响,并提出了一种软件实现的方法来抑制强度噪声,经验证随机游走减小了30%.     

强度反馈对半导体激光器量子噪声的改善

本文研究了强度负反馈对半导体激光器(LD)量子AM噪声的抑制。     

频带灵活运用的分割扩展频谱技术

本文研究在扩展频谱（ＳＳ）无线定位系统与其他无线电业务之间干扰最小的方法。重温控制ＳＳ信号功率谱密度（ＰＳＤ）的方法。介绍使相互干扰最小的一种新技术，称作“分离信号”法。这种方法通过将ＳＳ信号分割成几个低速率窄带分量，利用非连续的射频谱，这些分量射频谱有间隙地独立发射，到接收机再合成。通过分析和模拟，将分割信号的ＳＳ无线电定位系统的性能与常规宽带ＳＳ系统的性能做了比较。     

频谱分割WDM无源光网络中的损耗和串扰研究

提出了一种频谱分割WDM无源光网络（PON）的损耗和串扰模型，通过理论分析和数值计算，得到了损耗和串扰与光源带宽、复用器参数、信道数以及信道失配系数等系统参数的关系，对频谱分割WDM PON的设计具有一定的指导意义。     

半导体激光器相对强度噪声的实验研究

建立了一套半导体激光器噪声测量系统用于生产测量和科学研究,其特点是简易,且兼容性大。用该系统对相关的半导体激光器(不同腔长,镀膜与不镀膜等)进行了测量研究,着重研究了镀膜与不镀膜的条件对激光器噪声特性的影响,发现镀膜后管芯一致性提高、受反馈影响增大。为实际生产提供了改进建议,即需要针对实际应用来精心选择端面镀膜的反射率,前端面镀膜反射率不能太低。     

Reduction of excess intensity noise in spectrum-sliced incoherentlight for WDM applications

We investigate wideband reduction of excess intensity noise in incoherent light for application to spectrum-sliced WDM systems. The noise reduction scheme is based on optoelectronic feedforward compensation. We derive expressions for the probability density function of noise-reduced incoherent light and present measurements that are in good agreement with theory. We evaluate the significant levels of improvement obtainable in the capacity of spectrum-sliced WDM channels. For example, to obtain a signal-to-noise ratio of 50, a noise-reduced channel requires six times less optical bandwidth than a spectral slice without noise reduction     

Noise suppression of incoherent light using a gain-saturated SOA: implications for spectrum-sliced WDM systems

In this paper, we present an experimental and numerical study of semiconductor optical amplifier (SOA)-based noise suppression and its relevance to high-channel-density spectrum-sliced wavelength-division-multiplexed systems. We show that the improvement in signal quality is accompanied by spectral distortion, which renders it susceptible to deterioration in the presence of subsequent optical filtering. This phenomenon originates from the loss of intensity correlation between spectral components of the SOA output when the signal spectrum is altered. As a consequence, a design tradeoff is introduced between intensity noise and crosstalk in high-channel-density systems. These adverse effects can be overcome by optimized SOA design, resulting in a significant improvement in signal quality.     

Impact of nonlinear phase noise on direct-detection DQPSK WDM systems

The performance degradation of differential quadrature phase-shift keying (DQPSK) wavelength-division-multiplexed (WDM) systems due to self-phase modulation (SPM)- and cross-phase modulation (XPM)-induced nonlinear phase noise is evaluated in this letter. The XPM-induced nonlinear phase noise is approximated as Gaussian distribution and summed together with the SPM-induced nonlinear phase noise. We demonstrate that 10-Gb/s systems, whose walkoff length is larger than 40-Gb/s systems', are more sensitive to XPM-induced nonlinear phase noise than 40-Gb/s systems. Furthermore, DQPSK WDM systems show lower tolerance to both SPM- and XPM-induced nonlinear phase noise than differential phase-shift keying WDM systems.     

Cross-phase-modulation-induced nonlinear phase noise in WDM direct-detection DPSK systems

In direct-detection differential-phase-shift-keying (DPSK) systems, the signal-spontaneous emission beat noise introduces phase noise due to Kerr nonlinearity. In wavelength-division-multiplexed (WDM) systems, this nonlinear phase noise comes not only from the channel itself through self-phase modulation (SPM) but also from the other channels through cross-phase modulation (XPM). In this paper, we theoretically and experimentally investigate XPM-induced nonlinear phase noise. We calculate the performance degradation of DPSK systems caused by XPM-induced nonlinear phase noise in addition to SPM-induced phase noise and experimentally verify it using a 600-km nonzero-dispersion-shifted-fiber link.     

A method of simulating intensity modulation-direct detection WDM systems

In the simulation of Intensity Modulation-Direct Detection WDM Systems,when the dispersion and nonlinear effects play equally important roles,the intensity fluctuation caused by cross-phase modulation may be overestimated as a result of the improper step size. Therefore,the step size in numerical simulation should be selected to suppress false XPM intensity modulation （keep it much less than signal power）. According to this criterion, the step size is variable along the fiber. For a WDM system,the step size depends on the channel separation. Different type of transmission fiber has different step size. In the split-step Fourier method,this criterion can reduce simulation time,and when the step size is bigger than 100 meters,the simulation accuracy can also be improved.     

Sources of intensity noise in wide-band UHF analog optical communication systems: Their elimination and reduction

The feasibility of high-speed multimode analog fiber-optic transmission was examined by conducting a wide range of experiments on a fiber-optic link. The experimental link consisted of a laser transmitter with pigtail terminated in a fiber-optic connector, 240 m of fiber, and a detector with a pigtail terminated in a connector. Four different laser transmitters were used in the link. Changes in the amplitude and frequency separation of peaks in the noise spectrum due to optical feedback from the fiber-optic connectors and detector surface were investigated. Results indicated that index-matching gel placed in the connector nearest the transmitter reduced the near-end reflection peaks. Gel placed in both connectors increased the far-end reflection peaks when a conventional detector was used. However, these far-end reflection peaks were eliminated by using an angled detector which had a surface tilted at an angle relative to the end of the pigtail fiber. A heavily-moded laser showed substantially smaller reflection peaks and less change in the noise floor due to connector/fiber vibration than a laser with 1 or 2 modes.     

Investigation of amplitude noise and timing jitter of supercontinuum spectrum-sliced pulses

We numerically investigate the amplitude-noise and the timing jitter of pulses obtained by slicing coherent supercontinuum spectra. Applications such as time-division-multiplexing/wavelength-division-multiplexing systems and all-optical data regeneration are addressed. System parameters for optimizing the quality of sliced pulses are also discussed. We show that supercontinuum generation is a suitable method for generating amplitude-stable pulses and that no timing jitter is associated to the sliced pulses.     

WDM传输系统中的高阶色散管理方法

在长距离波分复用(WDM)光纤通信系统中，色散和非线性是影响系统性能的主要因素，为减小由此引起的四波混频(FWM)窜扰和信号波形失真，本文详细分析了传输线路局部参数对系统性能的影响，提出了在不同DWDM系统中，高阶色散管理线路的最佳参数配置方法，用以增加系统传输容量，提高系统性能。     

Phase-induced intensity noise in digital incoherent all-optical tapped-delay line systems

In this paper, the authors analyze conditions under which they can be certain on the intensity addition of a given device, such as tapped-delay lines, used in digital incoherent all-optical communication systems. A general expression for phase-induced intensity noise that is applicable to all types of semiconductor lasers is derived by defining an optical self-SNR expression that can be used to analyze and measure phase-induced intensity noise. The result shows that in order to have a minimal phase-induced intensity noise in most digital optical incoherent systems, a large optical self-SNR, e.g., 20 dB or more, is needed. This in turn is shown to place a limit on the maximum rate of processing in a typical incoherent optical system even neglecting the bandwidth limitation of the photodetector. Furthermore, it is shown that the maximum rate of processing depends on the laser autocorrelation function and laser coherence time.