OSNR Monitoring Technique for DPSK/DQPSK Signals Based on Self-Heterodyne Detection

We describe a new method for monitoring the “in-band” optical signal-to-noise ratio (OSNR) of differential phase-shift-keying (DPSK) and differential quadrature phase-shift-keying (DQPSK) signals. This technique estimates the OSNR by analyzing the radio frequency spectrum obtained by the self-heterodyne detection. The results show that the performance of the proposed technique is not sensitive to the effects of chromatic dispersion and polarization-mode dispersion. In addition, this technique can be used for monitoring the polarization-scrambled signals. For a demonstration, we measure the OSNR of the polarization-scrambled 10-Gb/s DPSK and 20-Gb/s DQPSK signals in a 640-km-long transmission link.      

偏振分光法光信噪比监测技术研究

偏振分光法是基于偏振特性分离信号和噪声的光信噪比(OSNR)监测技术,光纤的非线性效应和偏振模色散会引起传输信号偏振态的改变,影响OSNR的测量准确性.在介绍偏振分光法工作原理和设计流程的基础上,定量分析了非线性效应对偏振分光法测量精度的影响,最后提出了一种附加光滤波器的双通带偏振分光法OSNR测量方案,仿真实验证明该测量方法可提高OSNR的测量精度.     

In-Band OSNR Monitoring Technique Based on Link-by-Link Estimation for Dynamic Transparent Optical Networks

A cost-effective optical performance monitoring system, based on link-by-link optical signal-to-noise ratio (OSNR) estimation, is proposed for a dynamic transparent optical network. The proposed technique estimates the OSNR by monitoring the channel powers at the input and output of each optical link and the total input power to the inline EDFAs. In-band OSNR monitoring was successfully demonstrated at 42.7 Gb/s RZ-DQPSK signals, reflecting the transmission performance.     

PMD对偏振分光OSNR监测方法的影响

偏振模色散(PMD)引起的传输信号去偏是造成偏振分光法监测光信噪比(OSNR)准确性下降的主要因素.研究了偏振模色散对信号和放大的自发辐射(ASE)噪声功率测量的影响,推导得出了误差计算公式并通过仿真实验得到验证.理论分析和仿真实验结果均表明:测量误差随着PMD的增大而增大,当差分群时延(DGD)为80 ps时,误差达4.5 dB;测量误差还随着系统传输速率和信道自身光信噪比的提高而变大.     

Independent and Simultaneous Monitoring of Chromatic and Polarization-Mode Dispersion in OOK and DPSK Transmission

We propose and demonstrate a novel technique for a simultaneous chromatic and first-order polarization-mode-dispersion (PMD) monitoring method using a partial bit delay Mach-Zehnder interferometer (MZI) with radio-frequency (RF) clock tone monitoring. RF clock tones at the output of the two branches of the MZI behave oppositely with increasing chromatic dispersion (CD) which improves the sensitivity of the measurement. The technique increases CD monitoring sensitivity over standard clock tone methods by a factor of two for a nonreturn-to-zero intensity modulation format and a factor of five for a differential-phase-shift-keying modulation format. The accuracy of PMD monitoring is also enhanced. Moreover, the partial bit delay allows the signal to pass through the constructive branch of the MZI with no observable degradation of the signal quality, allowing it to be normally detected by a receiver     

Design and Performance of an All-Optical Wavelength Converter Based on a Semiconductor Optical Amplifier and Delay Interferometer

The design and performance of an all-optical wavelength converter based on a semiconductor optical amplifier (SOA) and a delay interferometer (DI) are presented for 10-Gb/s return-to-zero (RZ) transmission systems with pulsewidths of 25-45 ps. The performance of the wavelength converter is investigated in terms of the operating conditions for the SOA and DI, and the properties of the input signal. The regenerative characteristics of the wavelength converter are also examined for input signals degraded by amplified spontaneous emission noise and residual dispersion. With proper design, the SOA-DI structure provides a high-performance all-optical wavelength converter for 10-Gb/s RZ transmission with practical pulsewidths.     

光信噪比对光自愈环的影响

在光自愈环系统中，光信噪比是限制其传输距离的一个重要因素，本文给出了一种计算光信噪比所允许的最大传输距离的方法，分析了在不同业务配置方式复用段保护情况下的业务最大传输距离，指出在提供复用段保护的自愈环中业务的配置应尽量采用近端路径来实现。     

XPM Statistics in 100% Precompensated WDM Transmission for OOK and DPSK Formats

We numerically study cross-phase modulation (XPM) statistics in 100% precompensated wavelength-division-multiplexing transmission with on–off keying (OOK) and differential phase-shift keying (DPSK) formats. XPM and its randomness are determined by nonlinear diffusion bandwidth and specific modulation format in the target channel. XPM degradation in DPSK channels shows much less stochastic than that in OOK channels. The small duty cycle also helps to reduce XPM randomness.      

Bidirectional ROF Links Using Optically Up-Converted DPSK for Downstream and Remodulated OOK for Upstream

We propose a novel radio-over-fiber system to provide full-duplex services by using optical differential phase-shift keying modulation format at the central station for downstream and on-off keying remodulation of the downlink carrier at the base station (BS) for upstream. The optical carrier suppression modulation scheme is employed to simultaneously generate and up-convert 40-GHz optical millimeter wave. As the same optical carrier is used for both uplink and downlink, no additional light source is required at the BS, which greatly reduces the cost and simplifies the overall system. Simulations and experimental results show that the bidirectional 2.5-Gb/s data is successfully transmitted over 40-km single-mode fiber (SMF-28) with less than 2-dB power penalty     

Measured Noise Performance for Heterodyne Detection of 10-Gb/s OOK and DPSK

Heterodyne detection of 10-Gb/s nonreturn-to-zero (NRZ) on-off keying and NRZ differential phase-shift keying is demonstrated. The noise performance of the heterodyne receiver with and without the use of an optical preamplifier is experimentally investigated     

The effects of PMD and PDL on the performance of OOK and DPSK systems

Using multiple importance sampling （MIS） technique, the optical communication system performance affected by polarization-mode dispersion （PMD） and polarization-dependent loss （PDL） is simulated numerically. The power penalties and system outage probabilities are obtained for optical communication systems with on-off keying （OOK） or differential phase shift keying （DPSK） modulation. The simulation results show that DPSK always performs better than OOK. When the system has moderate PDL （about 1.5 dB）, it is necessary to compensate effectively the fiber PMD in order to enhance the system tolerance to the PMD and PDL. However, the efficiency of PMD compensation will degrade rapidly when the PMD of the whole optical link drops into the low value.     

Gamma-Gamma信道下OOK与DPSK调制误码性能分析

从理论和实验两方面对自由空间光通信中常用的两种调制方式进行性能比较分析,旨在找出一种最适合的调制方法抑制大气湍流。在分析Gamma-Gamma信道下OOK(开关键控)和DPSK(差分相移键控)调制的误码率时,将广义超几何方法引入分析。利用Matlab软件搭建系统,通过实验可知,采取相干及平衡探测的DPSK调制时性能要比基于OOK调制的直接探测高出3.21dB;通过对双管平衡探测和单管探测进行实验,结果表明,双管平衡探测的信噪比优于单管探测,约提高21.6dB。因此,基于DPSK平衡探测的相干通信方案具有可行性和优越性。     

基于偏振实现OSNR和PMD的同时监测

在介绍偏振度(DOP)监测方法工作原理,分析偏振模色散(PMD)导致传输信号去偏问题的基础上,提出了一种采用扰偏器和偏振分束器实现光信噪比(OSNR)和PMD同时监测的方案.波分复用传输信号经扰偏器扰偏后解复用分离出待测信道信号,偏振分束器将待测信号分成偏振正交的两个支路,然后通过检测两支路信号功率之间的关系得到信道的OSNR和PMD值,系统中使用了电放大器,以提高监测灵敏度.     

基于Sagnac干涉仪的新型声源定位光纤传感器

利用法拉第旋转镜（FRM）把Sagnac光纤干涉仪的环形光纤臂改成单臂直线结构的新型零程差干涉仪，克服了传统Sagnac光纤干涉仪结构上的缺点。另外，FRM作为偏振补偿器解决了偏振诱导信号衰弱问题。对该装置进行了理论分析，并以管道的泄漏声为例进行了实验研究，实验结果与理论分析相吻合，定位误差小于1％，表明该装置可以实现宽频声信号源的定位。     

Noise Transfer Characteristics in a Semiconductor Optical Amplifier With Application to Wavelength Conversion Based on a Delay Interferometer

A theoretical model is presented to analyze the noise transfer characteristics in a semiconductor optical amplifier (SOA) under the excitation of a noisy pump signal and a noise-free probe signal. An analytical expression is derived for the optical signal-to-noise ratio (OSNR) of the output probe signal from the SOA. The influence of the gain saturation of the SOA, and the pump and probe signal powers on the noise transfer characteristics is investigated. The noise transfer model is used to determine the output noise power of a delay interference wavelength converter. An analytical expression is obtained for the nonlinear phase change in the SOA, which determines the output power of the wavelength-converted signal. These results show that the noise transfer in the wavelength conversion can be suppressed by increasing the probe signal power, but that the improvement in the output signal OSNR relative to the input signal OSNR is accompanied by a reduction in the conversion efficiency. This fundamental tradeoff can be readily investigated during the design optimization process using the concise results derived in this paper.     

Wavelength-Tunable Laser for Signal Remodulation in WDM Access Networks Using DPSK Downlink and OOK Uplink

In this investigation, a simple wavelength-tunable laser based on a Fabry–PÉrot laser diode (FP-LD) and an erbium-doped fiber amplifier to serve as a downlink signal in a colorless wavelength-division-multiplexed passive optical network (PON) is proposed and experimentally demonstrated. The tuning range of the proposed laser is between 1529.48 and 1560.72 nm, and the output performance of proposed laser is discussed. Colorless operation is implemented by using an FP-LD and a reflective semiconductor optical amplifier in each optical network unit for uplink signal remodulation, respectively. In addition, error-free data signal remodulation using 10-Gb/s downlink differential phase-shift keying and 2.5-Gb/s uplink on–off keying is achieved in a 25-km reach PON.      

基于微分干涉仪的新型光纤声传感器

基于微分干涉仪原理，建立了一套新型光纤声传感器系统。对该系统进行了理论分析，建立了系统的数学模型，推导并分析了干涉仪的输出信号，并以宽频信号做声源进行了实验研究。实验结果与理论分析相吻合，解决了目前双干涉仪线性范围窄的问题，简化了信号处理电路，可使用低相干光源，并且系统不受外界缓变因素的影响，对宽频声源定位的误差小于1％。     

偏振正交外差光信噪比监测技术研究

传统偏振方法监测光信噪比的准确性易受偏振模色散和非线性双折射影响,提出了一种新的偏振正交外差监测方法以克服传统偏振监测方法的缺点.该方法通过将信号分成两个支路并控制偏振态达到相对偏振态正交,用偏振正交的两支路信号外差混频消去信号,通过测量保留下来的差拍噪声实现对光信噪比的监测.仿真试验证实,该方法对偏振模色散和非线性双折射引起的信号偏振态变化不敏感.     

Comparison of DPSK and OOK modulation format in 160 Gbit/s transmission system

Single-polarisation 160 Gbit/s OTDM transmission over 3/spl times/80 km dispersion-managed SLA fibre using DPSK and OOK modulation is reported. The influence of the fibre input power is experimentally and theoretically investigated. A significant advantage for DPSK is revealed.     

基于自适应滤波的DPSK解调方法及性能

本文研究了一种基于自适应滤波（ＡＤＦ）算法的解调差分相移键控（ＤＰＳＫ）信号的方法,用常用的最小均方误差（ＬＭＳ）自适应算法,研究了自适应解调（ＡＤＥＭ）方法对ＤＰＳＫ信号的解调及其性能,计算机模拟结果表明,自适应ＤＰＳＫ解调比传统的ＤＰＳＫ相干解调性能优越,便于用数字信号处理技术实现。