Postdetection Adjustable Simultaneous Compensation of DGD and GVD in a 40-Gb/s Optical Single-Sideband System

Results on postdetection compensation of group velocity dispersion (GVD) and differential group delay (DGD) in a 40-Gb/s optical single-sideband system are presented. An electrically adjustable transversal filter structure and a microstrip line are used as electrical compensators. Our results show that 408 ps/nm of GVD or 18 ps of DGD, considered separately, are compensated with less than 1.3-dB optical signal-to-noise ratio (OSNR) penalty to back-to-back without compensator, for an extinction ratio (ER) of 6 dB. The simultaneous effect of 12.3 ps of DGD and 374 ps/nm of GVD is compensated with less than 2-dB OSNR penalty, also for ER of 6 dB. Simulations performed support the experimental results.     

Performance limitations of high-power DFB fiber lasers

In this letter, we experimentally study several different configurations of high-power single-frequency sources based on distributed-feedback fiber laser (DFB FL). In particular, we have compared two schemes in terms of pumping efficiency, relative intensity noise (RIN) and optical signal-to-noise ratio (OSNR): directly pumped DFB FLs pumped by a high-power fiber-based pump source (stand-alone DFB FL) and a combination of a DFB FL and a power amplifier (amplified DFB FL). At the output powers below 40 mW, a stand-alone DFB FL has the highest OSNR (> 63 dB) and the lowest RIN (< -165 dB/Hz). The net efficiency of a stand-alone DFB FL can be doubled by using an amplified DFB FL at the expense of degraded OSNR and RIN. It is also shown that RIN below -160 dB/Hz and OSNR > 60 dB can be achieved by an amplified DFB with output power greater than 1 W.     

Enhanced Optical Generation of 42.7 Gbps Phase Shaped Binary Transmission

A novel method for optical phase shaped binary transmission (PSBT) generation has been recently reported and experimentally evaluated. An amelioration of the optical signal‐to‐noise ratio (OSNR) sensitivity of the optical PSBT modulation format is proposed with the application of the concepts of enhanced electrical PSBT signal generation. Enhanced optical PSBT is proposed here as a modulation format producing a 0.7 dB gain in OSNR sensitivity compared to OPSBT, while maintaining a good robustness to group velocity dispersion: 100 ps/nm for enhanced optical PSBT and 120 ps/nm for optical PSBT, compared to 50 ps/nm for standard NRZ signals.     

Polarization-Insensitive Low Timing Jitter and Highly Optical Noise Tolerant All-Optical 40-GHz Clock Recovery Using a Bulk and a Quantum-Dots-Based Self-Pulsating Laser Cascade

We report on the experimental assessment of an all-optical clock-recovery scheme at 40-Gb/s cascading a polarization-insensitive bulk-based self-pulsating (SP) laser and a high spectral purity quantum-dots-based SP laser. It is demonstrated experimentally that such a clock-recovery scheme is polarization insensitive, efficient in the jitter filtering, and tolerant for an input optical signal-to-noise ratio (OSNR) as low as 15 dB/0.1 nm. It is shown theoretically that the jitter-filtering function of the cascade is the product of the transfer functions of both lasers. The contributions of the phase noise of these two lasers to the final jitter are also identified and quantified. The influence of the degradation of the OSNR to the total timing jitter is also analyzed. The approach proposed in this paper offers the real opportunity to realize an all-optical clock recovery with a performance compatible for system applications     

OSNR Monitoring Method for OOK and DPSK Based on Optical Delay Interferometer

We describe a simple method to measure the optical signal-to-noise ratio (OSNR) of on-off-keying (OOK) and differential phase-shift-keying (DPSK) signals by using an optical delay interferometer (ODI) having a sinusoidal and tunable passband. This OSNR monitoring method is independent of chromatic dispersion, polarization-mode dispersion, and noise polarization. We show experimentally that accurate OSNR measurements are made for a 10-Gb/s OOK signal by using a 1-bit ODI and a 40-Gb/s DPSK signal by using a partial-bit ODI with the OSNR ranging from 5 to 25 dB.     

反向抽运分布式光纤拉曼放大器的实验研究

实验研究了1425 nm和1453 nm双波长反向抽运50 km单模光纤的分布式光纤拉曼放大器(RFA)。利用改进的时域消光法测量了放大器的输出特性和光学信噪比(OSNR)随开关增益的变化关系。在C波段(1530~1564 nm)内,测得放大器的开关增益约为13 dB,增益不平坦度小于±0.6 dB,相对于双瑞利散射(DRS)噪声的光学信噪比为45 dB,总的光学信噪比为39 dB。同时还测量了信号光经过二级级联分布式光纤放大器传输后的特性,结果表明,与一级光纤拉曼放大器结构相比,二级放大器的开关增益和不平坦度都增大了一倍,而输出的光学信噪比减小了约2 dB。     

RZ-DPSK transmission using a 42.7-Gb/s integrated balanced optical front end with record sensitivity

We have demonstrated a record sensitivity of -37.0 dBm (38 photons/bit) for a BER of 10/sup -9/ at 42.7-Gb/s using an integrated balanced optical front end. Results were obtained using optical preamplification of RZ-DPSK modulation and an external delay-interferometer. The OSNR requirement was measured to be 16.9 dB in a 0.1-nm bandwidth. The impact of polarization-mode dispersion (PMD) and chromatic dispersion on the optical front end performance has been measured. Performance for enhanced forward error correction has been projected based on 10/sup -3/ BER performance.     

扫频相干探测光谱幅度码标记交换系统的传输性能分析

基于光谱幅度码(SAC)标记的生成原理,利用扫频相干探测技术,搭建对156Mbit/s SAC标记进行识别的SAC标记交换系统。加载40Gb/s强度调制(IM)净荷信息后,分别对背靠背、40km和80km传输距离下,本振光源(LO)线宽、发射功率以及净荷与标记频率间隔对标记接收质量的影响进行仿真分析。同时分析接收光功率(ROP)、光信噪比(OSNR)、标记与净荷频率间隔对净荷误码(BER)特性的影响。结果表明:传输40 km、80 km后,标记接收眼高度(EH)与背靠背系统相比差别较小,且都能达到-0.6 dB左右;同时,传输80 km后,当净荷BER为10-9时,其ROP与OSNR分别为-17.8dBm和14.5dB。     

Optical Signal-to-Noise Ratio Estimation Using Reference Asynchronous Histograms

This paper presents and experimentally demonstrates a novel method for the estimation of optical signal-to-noise ratio (OSNR) based on the comparison of an asynchronous histogram of the signal under analysis with a reference asynchronous histogram. The latter is acquired from the signal under analysis at a calibration stage. The proposed method allows the use of optical amplification to increase the sensitivity of the optical monitoring system (OMS) by a factor 20 dB, when using an erbium doped fiber preamplifier. In addition, the use of a semiconductor optical preamplifier, initially designed for nonlinear operation at 2.5 Gb/s is used in the OMS to preamplify 40-Gb/s signals, achieving a sensitivity gain of 10 dB. It will be experimentally demonstrated that the proposed method is applicable to 40-Gb/s nonreturn to zero (NRZ) signals arbitrarily degraded by group velocity dispersion (GVD). Furthermore, accurate monitoring of the OSNR of return-to-zero (RZ) signals will also be possible using a simple RZ-to-NRZ converter based on narrow-band optical filtering within the OMS. The proposed method also allows estimating of the GVD-induced OSNR penalty between the signal under analysis and the signal at the calibration stage.     

All-optical in-band OSNR monitoring at 40 Gb/s using a nonlinear optical loop mirror

We present an all-optical in-band optical signal-to-noise ratio (OSNR) monitor using a nonlinear optical loop mirror. Monitoring is enabled from the nonlinear power transfer function of the loop mirror. Experimental results are provided at 40 Gb/s for three modulation formats: nonreturn-to-zero, carrier-suppressed return-to-zero, and return-to-zero. The monitor discriminates the various OSNR levels over a dynamic range of more than 25 dB with every modulation format.     

Multiple-channel OSNR monitoring with a single detector

We report a multichannel optical signal-to-noise ratio (OSNR) monitoring method using the integrated planar lightwave circuit and fast Fourier transform techniques with a single detector. The OSNR of four-channel wavelength-division-multiplexing signals can be monitored for a dynamic range of 20 dB with an accuracy of /spl plusmn/1 dB. This method can further allow one to suppress the optical crosstalk in accordance with the requirements of OSNR accuracy and dynamic range.     

多跳相干探测光谱幅度码标记交换系统传输特性分析

提出了一种基于标记栈技术的两跳相干探测光谱幅度码(SAC)标记交换系统.利用仿真软件,搭建了包含两个转发节点、两个156 Mb/s光谱幅度码标记、与40 Gb/s差分正交相移键控(DQPSK)净荷的光标记交换系统.利用接收光功率与光信噪比(OSNR)分析系统传输性能,并得到结论:经两个节点传输后,标记与净荷产生的功率代价与OSNR代价均未超过3 dB.     

Optical Performance Monitoring of Phase-Modulated Signals Using Asynchronous Amplitude Histogram Analysis

As optical networks continue to grow towards high capacity and high flexibility, new transmission technologies are being introduced. In order to maintain the quality of signal and control over network in the transparent domains, optical performance monitoring (OPM) systems are becoming a necessity. Phase modulation formats emerge as the solution of choice in transparent domains because of their sensitivity, spectral efficiency, and resilience to optical impairments. In this paper, we demonstrate a flexible OPM method for phase-modulated signals using asynchronous amplitude histogram analysis. We show numerically and experimentally the monitoring of optical signal-to-noise ratio (OSNR), chromatic dispersion (CD), and polarization-mode dispersion (PMD) for differential phase-shift keying (DPSK) and differential quadrature phase-shift keying (DQPSK) signals. The OSNR can be measured within range of 20-35 dB and accumulated chromatic dispersion between 600 and 600 ps/nm. The asynchronous amplitude histogram monitoring method is proved to be a precise and versatile monitoring tool for high-capacity optical networks.     

An OSNR monitor for optical packet switched networks

Optical packet switched networks bring about new challenges to the research in optical performance monitoring. We present the first experimental demonstration of an optical signal-to-noise ratio (OSNR) monitor capable of direct OSNR monitoring on the packet basis. By measuring the radio frequency noise from optical packets with a special performance monitoring segment, the OSNR monitoring error is found to be less than 0.6dB for consecutive packets with varying OSNR of 16 to 27 dB. The response time of the OSNR monitor can be around 10 ns.     

Statistical Analysis of Optical Signal-to-Noise Ratio Monitoring Using Delay-Tap Sampling

We derive analytical expressions for the optical signal-to-noise ratio (OSNR) monitoring using delay-tap sampling for intensity-modulated direct-detection (IM/DD) systems. We demonstrate through our theoretical analysis and experimental results that modeling of noise correlation due to low-pass filtering between delay-tap samples enables accurate monitoring of OSNR, without recalibration for each system setup. Effects of chromatic dispersion (CD) and polarization-mode dispersion on the proposed technique are investigated through numerical simulations. The monitoring error remains within $pm$ 1 dB for CD up to 400 ps/nm and differential group delay up to 45 ps.      

通过恒包络调制提高相干光OFDM系统的光纤非线性容限

相干光正交频分复用(CO-OFDM)对光纤链路中 的色度色散(CD)和偏振模色散(PMD)具有较强的容忍性,但 是OFDM信号高峰均功率比(PAPR)的特点使其对光纤非线性效应 非常敏感,严重影响了系统传输性能。 本文提出了基于恒包络(CE)调制的方法使得系统中光信号PAPR降低为0dB,从而提高了CO-OFDM系统的非 线性传输性能。仿真结果表明,子载波采用16QAM调制的40Gbit/s单信道CE调制CO -OFDM系统,在经800km无色散补偿、欠色散补偿和周期全色散补偿 标准单模光纤(SSMF)链 路传输后,虽然较传统CO-OFDM存在约1.8dB的代价,但是系统最大 发射光功率分别提高 了6.2、9.3dB。并且,将本文方案应 用 到CO-OFDM和10Gbit/s NRZ-OOK混合传输WDM系统中,信道最大发 射光功率仍获得了5.2dB的提高。因此,本文提出的CE调制方法能有 效地提高CO-OFDM系统在不同传输环境中的光纤非线性容限。     

Research on the transmission performance of turbo codes in DDO-OFDM system

With the rapid development of optical elements with large capacity and high speed,the network architecture is of great importance in determing the performance of wavelength division multiplexing passive optical network(WDM-PON).This paper proposes a switching structure based on the tunable wavelength converter(TWC)and the arrayed-waveguide grating(AWG)for WDM-PON,in order to provide the function of opitcal virtual private network(OVPN).Using the tunable wavelength converter technology,this switch structure is designed and works between the optical line terminal(OLT)and optical network units(ONUs)in the WDM-PON system.Moreover,the wavelength assignment of upstream/downstream can be realized and direct communication between ONUs is also allowed by privite wavelength channel.Simulation results show that the proposed TWC and AWG based switching structure is able to achieve OVPN function and to gain better performances in terms of bite error rate(BER)and time delay.     

40Gbit/s RZ-DQPSK Transponder模块的技术研究

文章重点介绍了40Gbit/sRZ-DQPSK(归零码-差分正交相移键控)Transponder模块的组成和关键技术,针对发射端和接收端控制给出了合理的实验方案。通过眼图、星座图以及光信噪比试验进行验证,眼图良好,光信噪比为12.3dB。实验结果表明,采用该方案设计出的光模块的参数能满足标准要求,可以应用于光通信领域。     

Monitoring optical network performance degradation due to amplifier noise

The relationship between optical performance as monitored within a network and the end terminal optical signal-to-noise ratio (OSNR) and bit error ratio (BER) is measured for the case of performance degradation due to amplified spontaneous emission noise. Measurements on 10-Gb/s signals reveal that performance monitoring sensitivity to OSNR levels of 26 dB is sufficient for identifying degradations that impact the end terminal BER.     

用偏振模色散模拟器加偏振片实现带内光信噪比检测

提出了一种基于偏振模色散(PMD)模 拟器加偏振片的带内检测光信噪比(OSNR)的方法,理论分析了检测方 法的工作原理,证明了方法不受光纤链路色散和PMD的影响,并且与信号偏振态 、调制格式及传输 速率无关。测试结果表明:在9dB到34dB的测量范围 内,本文检测方 法的测量误差在0.5dB内;在1dB的测量误差范围内,对偏振相关损 耗(PDL)的容忍范围为1dB。