Analysis of Pulse Tolerance to Pump Depletion Induced Noise in DWDM Systems Using Distributed Fiber Raman Amplifiers

In distributed optical fiber Raman amplifiers,instantaneous pump power depletion is related to patterns of input DWDM signals and results in extra optical noise and crosstalk.This noise has different effects on non-return-to-zero (NRZ) and return-to-zero (RZ) pulse forms.These phenomena are compared with present simulation results.     

Optimal Configuration of Multiple Pump Powers and Wavelengths for Balanced Pre- and Post-pumped Raman Fiber Amplifiers

A novel configuration algorithm for bi-directionally pumped Raman amplifier is developed by adopting simulated annealing algorithm. Automatic design of optical fiber Raman amplifier using 10 laser diode pumps with different wavelengths and powers is demonstrated for 64 channels DWDM systems. The resulted gain ripple is less than 2.6 dB in amplification bandwidth of more than 50 nm for a transmission span of more than 300 km. The algorithm can be practically applied to desired signal channel number and gain profile.     

光纤拉曼放大器中双重瑞利背向散射噪声的抑制

研究了光纤拉曼放大器中双重瑞利散射噪声的特性，提出了在考虑拉曼光放大作用时，双重量早散射噪声的表达式。给出了在加入隔离器进入抑制后，双重量早散射噪声的计算方法，并进行了模拟分析，得出了旋转隔离器的最佳位置。     

Optimal Configuration of Multiple Pump Powers and Wavelengths for Balanced Pre- and Post-pumped Raman Fiber Amplifiers

A novel configuration algorithm for bi-directionally pumped Raman amplifier is developed by adopting simulated annealing algorithm. Automatic design of optical fiber Raman amplifier using 10 laser diode pumps with different wavelengths and powers is demonstrated for 64 channels DWDM systems. The resulted gain ripple is less than 2.6 dB in amplification bandwidth of more than 50 nm for a transmission span of more than 300 km. The algorithm can be practically applied to desired signal channel number and gain profile.     

Transient Response and Control of Pump-Reflecting Raman Fiber Amplifiers

Abstract

This article analyzes the transient effect in pump-reflecting Raman fiber amplifiers. In order to better understand the impact of reflecting the unused pump power in the amplifier behavior, several scenarios are investigated. Results show that this pumping scheme has a worse response to dynamic channel add/drop. However, a pump-controlled gain-locked system is proposed that is able to mitigate the amplifier transient response. Following this approach, an efficient low-cost Raman fiber amplifier suitable for dynamic optical networks is obtained.     

Numerical Routines for the Optimization of Pump Power and Wavelength in Distributed Raman Amplifiers

We present optimization routines developed to define rapidly and precisely the best pump wavelengths and powers for distributed Raman amplifier design. We confirm the validity of our method through simulations by solving the full propagation equations, which govern the amplifier behavior. The sensitivity of the results obtained on the target bandwidth and on the correct selection of the pump wavelengths is studied. Finally, we compare the efficiency of the presented method in relation to previously presented algorithms.     

Polarization-Dependent Gain in Raman Fiber Amplifiers with Depleted Pumps

Polarization-dependent gain in a Raman fiber amplifier in the depleted pump regime is investigated. Numerical investigations are realized and show that gain fluctuations are highly reduced when signal and pump interactions allow pump depletion.     

S波段光纤拉曼放大器中级联受激布里渊散射串扰的实验研究

研究了光纤激光器前向抽运的S波段分布式光纤拉曼放大器中级联的受激布里渊散射(SBS)串扰现象。用窄光谱带宽(<100MHz)的可调谐激光二极管作为信号源,通过S波段分布式光纤拉曼放大器,当被放大的信号功率超过单模光纤受激布里渊散射的阈值时,出现了前向受激布里渊散射,这是传导声波布里渊散射在光纤放大器中放大的现象。随着拉曼放大器抽运功率的提高,在斯托克斯区,出现了两阶受激布里渊散射线,在实验中观测到偶数阶的受激布里渊散射谱线功率大于奇数阶的布里渊一瑞利散射线。当进一步增加拉曼放大器的抽运功率,出现了前向级联的多阶受激布里渊散射现象,拉曼放大器的增益下降,被放大的信号功率转换为受激布里渊散射,噪声变大。受激布里渊散射的串扰破坏了拉曼放大器的特性,使拉曼放大器无法在密集波分复用光纤传输系统中使用,因此需要严格地控制入纤的信号功率和放大器的抽运功率。在实验中还观测到在光纤拉曼放大器中被放大的信号光和受激布里渊散射线两侧的伴线。     

低泵浦功率的遥泵放大在超长跨距密集波分复用系统中的应用

针对长跨距密集波分复用系统中喇曼放大入纤泵浦功率过大的问题,将遥泵放大器（RP-EDFA）引入到系统中,通过对共纤RP-EDFA的噪音性能及其优化设计的研究,在理论上计算比较了RP-EDFA系统和后向喇曼放大系统在不同泵浦功率水平下的光信噪比和非线性相移,表明遥泵放大技术有效降低了入纤泵浦的功率水平,更适合长跨距应用.运用遥泵放大技术,对一个典型的长跨距系统进行系统Q值的模拟,结果表明：在 220 mW泵浦功率水平下可以实现跨距为 167 km的40×11.6 Gbit/s系统1000 km传输,Q值裕量4.4 dB.     

多路干涉对光纤拉曼放大器噪声因数的影响

考虑了多路干涉与拉曼自发辐射噪声具有不同的谱分布特性，推导出信号的背向瑞利散射导致的多路干涉对光纤拉曼放大器噪声因数影响的解析表达式，给出了考虑多路干涉后光纤拉曼放大器的噪声因数的光学测量方法。分析了不同开关增益、不同输入信号功率、不同增益光纤背向瑞利散射情况下多路干涉对光纤拉曼放大器噪声因数的劣化程度。随着拉曼增益的增加，输入信号功率越大、背向瑞利散射越大，多路干涉的影响越大。     

双重瑞利散射导致的多路干涉噪声对光纤喇曼放大器噪声系数的影响

在没有对喇曼增益分布做任何假设的情况下,利用所推导的光纤喇曼放大器噪声系数的解析表达式,研究了不同光纤长度、不同信号输入功率、不同增益、不同瑞利散射下双重瑞利散射导致的多路干涉噪声对喇曼放大器噪声系数的影响.结果表明随着光纤长度,信号输入功率、喇曼增益和瑞利散射的增加,多路干涉噪声对噪声系数的劣化越严重.但通过合理的优化光纤长度、控制喇曼增益可以取得噪声和增益间的最佳平衡.     

Theoretical Analysis of Rayleigh Backscattering Noise in Fiber Raman Amplifiers

In this paper, a new theoretical model for Rayleigh backscattering (RB) analysis of fiber Raman amplifiers is proposed. The model includes all the interactions among the pumps, signals, and all orders of RB. The results show that the higher order RB has a negligible influence on the performance of the amplifier. The co-propagating and counterpropagating RB power of the signal grow quadratically with the net-gain of the amplifier. The signal to double Rayleigh backscattering noise ratio (OSNRDRB ) of backward-pumped FRAs is better than that of the forward-pumped ones at high net-gain level (＞ 13 dB), while at low net-gain level the OSNRDrb of the forward-pumped FRAs is slightly better than that of the backward-pumped ones.     

Theoretical Analysis of Rayleigh Backscattering Noise in Fiber Raman Amplifiers

In this paper, a new theoretical model for Rayleigh backscattering （RB） analysis of fiber Raman amplifiers is proposed. The model includes all the interactions among the pumps, signals, and all orders of RB. The results show that the higher order RB has a negligible influence on the performance of the amplifier. The co-propagating and counterpropagating RB power of the signal grow quadratically with the net-gain of the amplifier. The signal to double Rayleigh backscattering noise ratio （OSNRDRB ） of backward-pumped FRAs is better than that of the forward-pumped ones at high net-gain level （〉 13 dB）, while at low net-gain level the OSNRDRB of the forward-pumped FRAs is slightly better than that of the backward-pumped ones.     

Crostalk in WDM SCM Systems due to SRS

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Analytical Model of Non-dispersion-limited Transient Stimulated Raman Scattering in Single-mode Silica Fiber in WDM Optical Communication System

The non-dispersion-limited analytic solutions of unidirectional N-channel transient stimulated Raman scattering (SRS) coupling wave equation which governing the propagation of the optical signals in single-mode (SM) silica fiber have been presented. Taking into account the SRS cross coupling among the N-channels, the analytic solutions are applicable to the system with arbitrary channel separation and input signal light power.     

Analytical Model of Non-dispersion-limited Transient Stimulated Raman Scattering in Single-mode Silica Fiber in WDM Optical Communication System

1 IntroductionNowadays, fused silica fiber still is the most common fiber in wavelength divisionmultipleeing (WDM) OPtical commwhcation syStem. In the WDM system, themodulation type of input signal in one channel differs from another channel. FOrinstance, in the Ralnan fiber amplifiers, the pUmP is a continuous wave (CW) whilethe signals are pulse modulated. SO, when we study the SRS effect in the system, wemust take into account the different modulation type of signals. For a tWO-cha…     

Output Characteristics of High-Power Continuous Wave Raman Fiber Laser at 1484 nm Using Phosphosilicate Fiber

A continuous wave (CW) high-power Raman fiber laser (RFL) with maximum output power of 2.24 W and slope efficiency of 32.8% at 1484 nm is obtained using a CW 8.4 W/ 1064 nm Yb-doped double-clad fiber laser as a pump, 700 m phosphosilicate fiber, and cascaded cavities with two pairs of fiber Bragg grating mirrors for the first and the second Stokes orders. Theoretical simulation of the RFL using a very efficient and rapidly converging collocation method is done to understand and optimize the fiber length to obtain maximum second Stokes power. RFL performance for the 300, 700 and 1150 m phosphosilicate fiber lengths was experimentally investigated by observing maximum output power, slope efficiency, threshold power, and full-width at half maximum at the second Stokes wavelength.     

喇曼放大器系统中光信噪比与传输码型相关性研究

分析研究了采用分布式光纤喇曼放大器的DWDM光纤传输系统中,瞬态泵浦消耗噪音对信号眼图、误码率等性能指标的影响,比较了不同比特率和信道数时这种噪音所带来的影响,给出了模拟仿真结果;分析并比较了瞬态泵浦消耗噪音与喇曼串扰噪音对系统性能影响的程度,同时分析了不同码型所对应的瞬态泵浦消耗噪音,发现归零码(RZ)具有更好的噪音特性.     

Simultaneous Double-Color Continuous Wave Raman Fiber Laser at 1239 nm and 1484 nm Using Phosphosilicate Fiber

Simultaneous double-color high-power continuous wave (CW) Raman fiber laser at 1239 nm and 1484 nm is demonstrated which uses CW 8.4 W Yb-doped double-clad fiber laser at 1064 nm as a pump, 1 km phosphosilicate fiber, and cascaded cavities consisting of two pairs of fiber Bragg grating (FBG) mirrors. Maximum output powers are 0.65 W at 1239 nm and 0.97 W at 1484 nm with a 50%/50% output mirror reflectivity pair, and 0.37 W at 1239 nm and 1.06 W at 1484 nm with a 75.5%/50% pair. The output characteristics of this laser for different FBG mirror reflectivities are reported.     

Overview of DWDM/ODC Project

Abstract

This article introduces the main achievements resulting from the DWDM/ODC project. The five areas of research activity within the DWDM/ODC project cover some of the main issues of design and development of dense wavelength division multiplexing systems for transparent optical networks. These issues are: performance assessment with arbitrary optical filtering; performance of signaling formats; dispersion compensation strategies for directly and externally modulated systems in presence of nonlinear transmission-induced degradation; and the impact of noise and crosstalk in the extent of transparent optical networks. All five areas of research activity have contributed significantly to a better understanding of the limitations present in dense wavelength division multiplexing systems.