基于混合光纤放大器的波分复用光纤传输系统研究

在研究了入纤功率、光器件的插入损耗以及非归零码中1码出现的概率对系统误码率影响的基础上,提出了一种基于混合光纤放大器的波分复用(WDM)光纤传输系统设计方案,并对该系统的噪声特性进行了详细地研究。提出了一种抑制前向噪声的有效方法,实现了20路WDM信号320km无误码传输。试验结果对基于混合光纤放大器的波分复用光纤传输系统的设计具有一定的指导意义。     

混合型光纤喇曼放大器增益和带宽的研究

混合型色散补偿光纤喇曼放大器由普通G652光纤和色散补偿光纤(DCF)组成,包括:DCF +G652、G652 +DCF和 G652+DCF +G652。讨论了它们的工作原理.使用FRA-OptiAmplifier4.0软件对其进行了优化设计,最佳结构为G652 +DCF.它可补偿光纤网络的色散,扩展通信波长范围.1427 nm的喇曼激光器作为激发源,用Q8384光谱分析仪测量了光纤的喇曼增益谱和小信号放大光谱,混合型色散补偿光纤喇曼放大器在S带和C带具有88 nm的增益带宽,这增加了光纤通信网络的传输通道.     

Adding channels with PSBT format at 40 Gbit/s in an existing 10 Gbit/s optical network

Until recently, the wavelength-division-multiplexed (WDM) transmission system has reached record capacities and distances due to innovations such as FEC (Forward Error Correction), distributed Raman amplification, new transmission fiber and advanced optical format. Optical-communication systems exclusively employed conventional On-Off Keying signals in either Non-Return-To-Zero (NRZ) or Return-To-Zero (RZ) format. Recently a number of advanced modulation formats have attracted attention. Some of these formats carry information through On-Off-Keying but also modulate the optical phase in order to enhance the robustness of signal to chromatic dispersion, optical filtering and non-linearities. Through extensive sets of simulation results, we showed that it is possible to replace a channel with higher bit-rate on existing DPSK or OOK at 10Gbit/s transmission link. Duobinary formats are ideal candidates to do it and are known for their low spectral range and high tolerance to residual chromatic dispersion. These particularities make them very attractive for both high bit rates and high distance-transmissions. Today, Phase Shaped Binary Transmission (PSBT) is considered as being the promising format for the deployment of 40Gbit/s technology on existing links at 10Gbit/s WDM long haul transmissions.     

Performance of an optical wideband WDM system considering stimulated Raman scattering,fiber attenuation and chromatic dispersion

The performance of an optical wideband wavelength division multiplexed (WDM) communication system is analyzed considering the effects of stimulated Raman scattering, fiber attenuation and chromatic dispersion. Improved models for the Raman gain and the fiber attenuation constant are proposed, which yield better and reliable performance results of the WDM system. Effect of fiber chromatic dispersion is also investigated and it is observed that dispersion can suitably be selected to overcome the limitations imposed by the stimulated Raman scattering phenomenon.     

用于光纤熔接系统的纤芯检测镜头设计

光纤已广泛应用于当今社会的信息传输领域。为了满足长距离光纤传输中高质量光纤熔接的需要,介绍了一个应用于光纤熔接系统的透射光纤纤芯检测系统。该系统中的核心器件是一组能对光纤纤芯成像的特殊镜头。借助于ZEMAX软件,设计了这组检测镜头。该镜头具有8倍放大倍率、长工作距离、短结构、高精度等特点。论述了镜头的设计方案和设计过程,并给出了满足要求的设计结果。通过在LightTools软件中对整个系统检测结果的模拟,证明了该设计的可行性。     

Comparison of the performance of optical systems in fiber links 4000 km long

This article reports a numerical investigation of the performance of single-channel and WDM optical systems, assuming a fiber link 4000 km long in the presence of the Kerr effect, chromatic dispersion, and the amplifier spontaneous emission noise of the optical amplifiers. Both solitons and NRZ signals are considered, and IM-DD and coherent asynchronous ASK detections are used. Results on the technique of the midpoint spectral inversion are also reported.     

Analytical investigations on crosstalk in fiber Raman amplification for WDM systems

In this paper, the analytical investigations for the crosstalk in fiber amplification for WDM channels have been reported. The crosstalk between WDM channels with external Raman amplification including second-order dispersion terms has been investigated. It has been shown that the higher-order dispersion severely degrades the performance of optical communication systems. To ensure small crosstalk, the signal gain and the injected pump power should be limited to the value well below the threshold of Raman amplification. Analytical formula for signal interference ratio (SIR) and gain in fiber Raman amplifier including the impact of second-order dispersion terms for WDM systems has been derived at different wavelengths. It has also been shown that there is increase in crosstalk due to second-order dispersion.     

Performance comparison for RZ-DPSK signal in DCF-based and CFBG-based dispersive transmission system

The impact of the phase noise induced by self-phase modulation and intrachannel nonlinear effect for return-to-zero differential phase-shift keying (RZ-DPSK) in long haul 40 Gb/s transmission systems where dispersion is compensated by chirped fiber Bragg grating (CFBG) is analyzed and numerical evaluated, and it is compared with what is derived from the conventional DCF-based phase-modulated system. Our work also provides a clear physical picture of how the transmission performance is affected by CFBG, which is instructive for further research on CFBG compensated phase-modulated formats.     

Performance comparison between digital back propagation (DBP) and pilot-aided method for fiber nonlinearity compensation in different fiber links

We numerically investigate and compare the performance of fiber nonlinearity compensation using digital back propagation (DBP) method and pilot-aided method in coherent optical transmission systems using different fiber links. Simulations for wavelength division multiplexed (WDM) 112 Gb/s polarization division multiplexed quadrature phase shift keying (PDM-QPSK) systems with dispersion unmanaged (no DM) and dispersion managed (DM) fiber links are implemented. System Q-factor and maximum transmission distance at bit error rate (BER) of 3.8 ÿ 10^?3 are calculated for performance comparison. The results show that, for system with no DM fiber link, DBP method outperforms pilot-aided method, because DBP method has better performance for intra-channel fiber nonlinearity compensation. However, for system with DM fiber link where inter-channel fiber nonlinearity plays an important role, pilot-aided method performs better than DBP method, because of its ability for inter-channel fiber nonlinearity compensation.     

Multi-wavelength hybrid gain fiber ring laser based on Raman and erbium-doped fiber

A stable and uniform multi-wavelength fiber laser based on the hybrid gain of a dispersion compensating fiber as the Raman gain medium and an erbium-doped fiber (EDF) is introduced. The gain competition effects in the fiber Raman amplification (FRA) and EDF amplification are analyzed and compared experimentaUy. The FRA gain mechanism can suppress the gain competition effectively and make the present multi-wavelength laser stable at room temperature. The hybrid gain medium can also increase the lasing bandwidth compared with a pure EDF laser, and improve the power conversion efficiency compared with a pure fiber Raman laser.     

Effect of transmission fiber and amplifier noise on optical chaos synchronization

Optical chaos propagation has few constraints peculiar to itself which do not become as significant in conventional nonchaotic optical communication. We have investigated the effects of transmission fiber nonlinearities, dispersion and noise of erbium doped fiber amplifier (EDFA) on chaotic signal synchronization in lumped and distributed configuration. It is found that the effects of fiber dispersion can be easily compensated; however, the effects of fiber nonlinearity on chaos cannot be overdone and must be avoided. Three distinct configurations with different combinations of standard telecommunication fiber, dispersion compensation fiber and lumped and distributed EDF for amplification are analysed. The results are compared in terms of sync diagrams and noise figure. The chaos after propagation through distributed amplification performs better as compared to lumped amplification. Also, a new quantitative measure for the calculation of deviation in sync diagram of chaos is introduced.     

光相位共轭色散补偿波分复用系统的传输带宽

导出了光相位共轭器（DPC）接于常规单模光纤链路中点的色散补偿波分复用（WDM）系统传输带宽的估算公式，并用数值仿真的结果验证了公式的正确性；采用不对称接入光相位共轭器提高传输带宽的方法，导出了光相位共轭器接入位置对传输带宽影响的估算公式，利用公式估算和数值仿真的结果表明，当光相位共轭器处于最佳接入位置时，色散补偿的波分复用系统的传输带可以提高近一倍。     

Optical phase remodulation for Rayleigh noise mitigation in 10 Gb/s/channel WDM passive optical networks

We investigate the principles of optical phase remodulation and demonstrate its application in a future-proof10 Gb/s/channel wavelength-division-multiplexed(WDM) passive optical network to realize a colorless optical network unit and bidirectional transmission over a single fiber. The modulation depth of downstream differential phase-shift keying is properly reduced to facilitate phase remodulation and Rayleigh noise mitigation. For both downstream and upstream 10 Gb/s signals, error-free transmission via a 20 km single-mode fiber is demonstrated without dispersion compensation operation.     

光子晶体光纤的原理、结构、制作及潜在应用

传统光纤中的光能损耗和色散是阻碍其进一步向大容量和远距离通信方向发展的主要原因，因此制造具有低色散和低损耗的光子晶体光纤成为光纤技术努力的方向。在介绍光子晶体光纤的制作、导光原理和特点的基础上，研究了普通光纤不具备，而光子晶体光纤所具有的无休止的单模特性、奇异的色散特性、可控的非线性和易于实现的多芯传输等特点。研究结果表明，光子晶体光纤在光纤传感器、光子晶体天线、超宽色散补偿、光学集成电路等多方面具有广泛的应用前景。     

Investigation of optimum pulse shape for 112 Gbps DP-DQPSK in DWDM transmission

This paper reports the simulative analyses to investigate the impact of different pulse shapes on DP-DQPSK modulation for high-spectral efficient DWDM transmission at 112 Gbps per channel. In the simulation model we have considered three different pulse shapes viz. NRZ, 50% duty cycle RZ (RZ50) and 67% duty cycle RZ (RZ67) in symbol-aligned and symbol-interleaved format. The analysis has been carried out for various linear and nonlinear system impairments where the pulse is subjected to degradation under the influence of amplified spontaneous emission (ASE) noise, group velocity dispersion (GVD), cross-phase modulation (XPM) and polarization mode dispersion (PMD) and thus, limiting the system performance. Results show that the RZ50 pulse shape for DP-DQPSK with symbol interleaving shows the maximum tolerance for the various system degradations in long haul DWDM transmission. Even the system based on the NRZ pulse shape can gain significant improvement from the symbol-interleaving.     

光纤色散参量对光孤子系统传输性能的影响

采用计算机系统仿真方法研究光纤色散参量对应用相敏光放大器(PSA)作为在线放大器并采用平均孤子传输方案的光孤子通信系统传输性能的影响。研究结果表明：由于相敏光放大器增益的相敏特性．光纤色散导致孤子脉冲主瓣幅度下降,脉宽展宽,出现旁瓣。光纤色散值越大,经长距离传输后,孤子脉冲主瓣的幅度下降和脉宽展宽越显著;旁瓣的幅度越高,宽度越大。显然。对这种系统,要实现长距离传输,必须采用较低色散系数光纤。     

Dispersion compensating fiber used as a transmission fiber: inverse/reverse dispersion fiber

This paper gives an overview of IDF/RDF fiber design and development for submarine system. It starts with the concept of dispersion management line and its difference from the conventional DCF used in a module. Then it reviews the fiber design details and optical properties of various types of fibers used as parts of dispersion management lines. Fiber splicing issues using MFD expanding method and a brief summary of transmission experiments using the dispersion management lines are also included. Finally, we discussed a medial dispersion alternative comprising a positive and negative medial dispersion fiber and future optical properties improvements possibilities.     

非零色散位移光纤的改进设计及制造

介绍了一种新颖的非零色散位移光纤结构设计方法及其MCVD+OVD制造工艺,所制备的光纤有效面积达到71 μm2以上.采用关键结构区域精确微扰方法,改进了光纤的色散特性.1550 nm处色散斜率由0.0715 ps/(nm2·km),分别减小至0.0605 ps/(nm2·km),0.0466 ps/(nm2·km),零色散波长由1500 nm附近移至1450 nm以下.测量表明,所得光纤具有优越的光学传输特性、抗弯曲性能和熔接性能,适用于C+L和S+C+L工作波长的大容量高速率长距离密集波分复用系统.光纤关键结构区域精确微扰是改进光纤性能的一种有效方法,该方法不限于MCVD工艺和非零色散位移光纤,对新型光纤的设计和生产具有积极的指导意义.     

Polarization mode dispersion in WDM systems

The coupled nonlinear Schrodinger equations for two wavelength optical pulses in a birefringence fiber are given. The model for treating polarization mode dispersion in two channel (WDM) system is established. Based on this model, optical signal propagation behaviors in two channel WDM with polarization mode dispersion are numerically simulated. The influences of polarization mode dispersion on two channel WDM system are also analyzed.     

Priority-based parameter optimization strategy for reducing the effects of four-wave mixing on WDM system

In order to meet the ultra high speed and ultra long-haul transmission distance in wavelength division multiplexing (WDM) systems, the nonlinear impairment affecting the overall spectral efficiency and system performance should be minimized. This paper proposes a strategy to mitigate the four-wave mixing (FWM) effect in WDM system. The strategy determines the effect of both single and combined effects of second, third, and fourth optimization priority parameters such as fiber length, input power, dispersion, channel spacing, and effective area on FWM power. A comparison study was made under different types of optical fiber such as single-mode fiber (SMF), dispersion shifted fiber, non-zero dispersion fiber, and non-zero dispersion shifted fiber. In addition, the system performance in term of bit-error-rate was calculated in the case of single priority (impact of effective area) and combined priority (impact of effective area, input power, fiber length and channel spacing). The results show that the FWM effect was reduced based on the transmission parameters order of optimization, i.e., priority selection proposed. Moreover, the results indicated that increasing sequentially the effective area, fiber length; channel spacing and decreasing the input power provide the most significant sequence in suppressing the effects of FWM. This priority sequence brought the suppression ratio to approximately 26.3% in SMF, which suppressed the FWM effects up to −50 dBm. In term of BER; the combined priority introduces improvement in BER of 2.31 × 10⁻²⁵ in comparison with single priority that has value of BER 4 × 10⁻¹⁴. Finally, this work suggests that the proposed priority-based parameter optimization strategy is an ideal solution for optimum performance of WDM system.