光纤喇曼增益系数的简捷测量

基于小信号开关增益原理,采用抽运光-探测波法,利用SLD(超辐射激光二极管)作为宽带小信号探测光源,快速测量出了标准单模光纤(G.652)的频移为0.5～20 THz内的喇曼增益系数,测量结果和文献中已有的值基本吻合,所测得的光纤喇曼增益系数可用于光纤喇曼放大器的理论和实验研究,该方法同样可以对其他类型光纤的喇曼增益系数进行测量.     

喇曼光纤放大器阈值分析

基于泵浦未耗尽和洛仑兹线形假设对G652,G653,G655,LEAF四种光纤用作喇曼增益介质时的喇曼阈值进行了分析结果表明:喇曼域值同泵浦模式,光纤的有效面积有关,同向泵浦的域值低于反向泵浦,并且域值随光纤有效面积的增加而增加四种光纤中,G653光纤的域值最低,为0.222W.     

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.     

光纤喇曼放大器的特性及其在宽带通信中的应用

随着宽带业务的增长和 DWDM技术的发展 ,人们需要更宽增益带宽的全光放大器。光纤喇曼放大器由于其可放大任意波长信号的特性而得到广泛的关注和重视。介绍了喇曼放大器的特性 ,总结了国外近年来对喇曼放大器在宽带通信应用中的研究 ,并讨论了喇曼放大器的发展方向     

多泵浦光纤喇曼放大器的模拟分析

通过使用综合理论模型对不同配置条件下的多泵浦分布式光纤喇曼放大器的增益谱进行了数值模拟研究,该理论模型包含了瑞利散射、放大自发辐射和不同交互效应,包括泵浦与泵浦、泵浦与信号和信号与信号之间的交互与能量转移.模拟研究了泵浦源功率、泵浦源波长间隔及光纤损耗对喇曼增益谱的影响,结果表明设计多泵浦光纤喇曼放大器需要对泵浦源功率、泵浦源波长间隔光纤损耗谱进行综合考虑,需对泵浦源功率、泵浦源波长间隔进行合理配置.在本文的泵浦源波长设定条件下,考虑实际光纤的损耗谱特性,为了获得大的增益带宽和小的增益不平坦度,短波长泵浦源和最长波长的泵浦源需要更高的泵浦功率,中间波长泵浦源的功率应较低.     

反向抽运光纤喇曼放大器增益特性分析

将打靶法和龙格库塔法两种数值计算方法相结合，对反向抽运光纤喇曼放大器中信号光和抽运光相互作用的耦合微分方程进行数值求解.在分别选取不同参量且取不同值的条件下，详细分析了光纤长度、初始信号光功率、初始抽运光功率、光纤有效面积、喇曼增益系数及光纤对信号光与抽运光的损耗等参量对增益的影响，最后提出了有效提高增益的方法.     

高速色散补偿系统中喇曼放大器性能研究

利用喇曼放大器的非线性偏微分耦合方程组,对带喇曼放大器的色散补偿系统进行了仿真,并与传统的仿真方法进行了比较.结果表明:在色散完全补偿系统中,当传输速率较高时,忽略色散后的传统仿真方法的结果,与采用色散补偿技术后使整个系统色散为零的仿真结果有一定偏差,此时不能忽略色散的作用.还对前补偿系统和后补偿系统进行了研究,利用Q值性能判别法,分别得到了信号光脉冲的最佳占空比和最佳脉冲阶数.     

双向反馈布里渊-喇曼光纤激光器输出特性

设计了一种双向反馈布里渊-喇曼光纤激光器,研究了布里渊泵浦对输出特性的影响.布里渊-喇曼光纤激光器由一段7km色散补偿光纤、1 455nm喇曼泵浦、可调谐激光器及双反馈环组成.喇曼泵浦功率固定在250mW,布里渊泵浦工作波段在喇曼峰值增益处附近,可得到较多波长数输出.随着布里渊泵浦功率增加,相邻的布里渊斯托克斯光和经背向瑞利散射的斯托克斯光之间功率差减小,同时各阶斯托克斯光平均强度增加并达到饱和.受色散补偿光纤中喇曼交叉增益影响,布里渊泵浦功率由1.8dBm增加到6.9dBm,输出多波长数先增后减.当布里渊泵浦功率为4.4dBm时,对应输出波长数最多,为37个,波长间隔0.078nm.     

一种新颖的宽带光纤喇曼放大器优化设计方法

介绍了一种新颖的宽带光纤喇曼放大器的优化设计方法.通过研究多波长后向泵浦光纤喇曼放大器的传输方程, 分两步来确定各泵浦波的频率及输入功率的大小.首先通过模拟煺火算法迭代出满足条件的泵浦波频率,然后利用平均功率分析方法,采用四阶阿当迭代方法计算出各泵浦波输入功率的大小,从而设计出具有较宽平坦增益带宽的光纤喇曼放大器.该算法是一种简单有效的优化方法.     

单模光纤中受激喇曼散射对调制不稳定性的影响

基于修正的非线性薛定谔方程，利用线性扰动理论和数值方法研究了单模光纤中的调制不稳定性.由于受激喇曼散射的作用，使得喇曼增益谱叠加到光纤中的调制不稳定性增益谱上.这样，原本调制稳定的光纤正常色散区也出现了调制不稳定性；而在反常色散区，随着初始功率的增加，常规的调制不稳定性增益谱的增益和频谱范围均增大，而喇曼增益谱的增益增大但其频谱范围基本不变，这样导致常规的不稳定区域逐渐侵入并最终掩盖喇曼增益区.数值模拟验证了解析结果的正确性，并证明了利用反常色散情形下的调制不稳定性可以产生超短脉冲序列，但这种脉冲序列的进一步传输将会出现喇曼孤子自频移现象.     

Simulation and experimental characterization of Raman/EDFA hybrid amplifier with enhanced performance

We present simulation and experimental characterization of a hybrid amplifier comprising of a Raman amplifier and an erbium doped fiber (EDF) amplifier, with enhanced performance. The incorporation of a pumped EDF section in a fiber Raman amplifier (FRA) employing a dispersion compensating fiber is demonstrated to provide superior performance than a sole FRA system. The hybrid amplifier is characterized in terms of single channel gain and noise figure, and the results of measurements are shown to be in close agreement with the simulated results. Polarization-dependent gain (PDG) and multi-channel measured and simulated gain characterization of the Raman/EDFA hybrid amplifier are also presented.     

Amplification effect on SBS and Rayleigh scattering in the backward pumped distributed fiber Raman amplifier

The amplification effect on stimulated Brillouin scattering （SBS） and Rayleigh scattering in the backward pumped G652 fiber Raman amplifier （FRA） is studied. The pump source is a 1427.2-nm fiber Raman laser whose power is tunable between 0 - 1200 mW, and the signal source is a tunable narrow spectral bandwidth （〈 10 MHz） external cavity laser （ECL）. The Rayleigh scattering lines are amplified by the FRA and Stokes SBS lines are amplified by the FRA and the fiber Brillouin amplifier. The total gain of SBS lines is the production of the gain of Raman amplifier and that of Brillouin amplifier. In experiment, the SBS gain is about 42 dB and the saturation gain of 25-km G652 backward FRA is about 25 dB, so the gain of fiber Brillouin amplifier is about 17 dB.     

Research on WDM optical fiber transmission system based on fiber Raman amplifier

After wavelength division multiplexing (WDM) optical fiber transmission system based on fiber Raman amplifier (FRA) is investigated in detail, the influence of the collocation of dispersion compensation fiber (DCF), the dispersion coefficient, dispersion slope (DS), effective core area, nonlinear index, length of FRA, launch power and the bandwidth of Bessel filter on bit error rate (BER) is deduced. The influence of Rayleigh backscattering noise on optical signal noise ratio (OSNR) is also investigated, which affects the performance of long haul transmission badly. The result indicates that the broadband long haul transmission can be realized through the reasonable design of the fiber. The result is useful to the optimal design of the WDM optical fiber transmission system based on FRA.     

Amplification effect on stimulated Brillouin scattering in the S-band forward G652 fiber Raman amplifier

The amplification effects on forward and backward stimulated Brillouin scattering (SBS) lines in the forward pumped S-band distributed G652 fiber Raman amplifier (FRA) have been studied. There is a pump threshold power of Stokes backward stimulated Brillouin scattering (B-SBS) line in the forward pumped G652 FRA, it is about 1 mW. The Stokes B-SBS lines are amplified by FRA and fiber Brillouin Brillouin gain. In experimental work, the saturation gain of the first order Stokes backward SBS line is about 58 dB and the saturation gain of 25-km G652 forward FRA is about 25 dB, so the gain of FBA is about 33 dB. The forward stimulated Brillouin scattering (F-SBS) is generated and amplified in S-band G652 FRA. The stimulated threshold powers of the forward first order Stokes SBS (SB1-), second order Stokes SBS (SB2-), and third order SBS (SB3-) in the forward pumped FRA are 2.3, 1.6, and 1.6 mW,respectively. In experimental work, the saturation gains of SB1-, SB2-, and SB3- are about 38, 62, and 60 dB, respectively. The saturation Raman gain of 25-km G652 forward FRA is about 8.8 dB, so the Brillouin gains of SB1-, SB2-, and SB3- are about 29.2, 53.2, and 51.2 dB, respectively. The forward and backward cascaded SBS lines have been observed.     

一种增益平坦的光子晶体拉曼光纤放大器

为解决传统拉曼放大器增益系数低和增益不平坦的问题,采用级联光子晶体光纤的设计方法设计了一种增益平坦的拉曼光纤放大器.采用受激拉曼散射效应的稳态分析理论,分析了光子晶体光纤的拉曼增益谱,建立了拉曼放大器的理论模型.通过解耦合方程,推导了实现增益平坦的约束条件,发现光纤长度和泵浦功率是影响拉曼光纤放大器增益平坦度的两个参数.仿真结果表明,在1 508～1 544 nm的带宽范围内,实现了一个增益高达21 dB,增益平坦度仅为0.14 dB的光子晶体拉曼光纤放大器,可在光纤通信系统应用中发挥重要作用.     

Single-wavelength-pump bi-directional hybrid fiber amplifier for bi-directional local area network application

This paper proposes a novel bi-directional hybrid fiber amplifier using a single-wavelength pump laser diode (LD) at 1495 nm. The hybrid amplifier is theoretically applied in a 50 km bi-directional local area network (LAN) with 26 ch × 10 Gb/s for bi-directional transmission. Thirteen C-band channels serve as downlink signals while the other 13 L-band channels are employed as uplink signals. Without loss of generality, four channels (two from each band) are experimentally analyzed. Erbium doped fiber (EDF) provides amplification for the C-band channels and Raman amplification amplifies the L-band channels. The pump efficiency is improved by employing a double-pass scheme for both the Erbium doped fiber amplifier (EDFA) and Raman fiber amplifier (RFA). The chromatic dispersion incurred by all the channels is precisely compensated for by inserting a fiber Bragg grating (FBG) array in appropriate locations along the dispersion compensating fiber (DCF) segments. Moreover, gain equalization of all the channels is achieved by adjusting the FBG reflectivity. Both the simulation results and experimental measurements confirm the proposed device feasibility and potential application in a bi-directional LAN.     

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.     

Zero-Loss Broadband Dispersion Compensation Scheme for G.652 Fibers

We have evaluated the gain characteristics of an erbium-doped broadband dual-core dispersion compensating fiber (DCF) to achieve a loss-less dispersion compensating module for long-haul G.652 fiber links.     

1410 nm波段分布式光纤拉曼增益放大器的研究

讨论了分布式光纤拉曼增益放大器的工作原理,采用1320nm固体激光器作为抽运源,获得了1410nm波段附近的光放大,在单模GI光纤长度为23km时,初步研究了拉曼放大器增益与光纤作用长度的关系,抽运脉冲峰值功率分别为50W、30W时,光纤的有效作用长度分别为15．5km和10.5km;研究了在不同的光纤有效作用长度时,拉曼放大器增益与抽运功率的关系;从光纤拉曼光谱图估算了光纤拉曼放大器的光谱宽度为50nm或250cm^-1。     

Multi-channel gain and noise figure evaluation of Raman/EDFA hybrid amplifiers

We present detailed multi-channel experimental characterization of different configurations of single pump hybrid Raman-erbium doped fiber (EDF) amplifiers. The incorporation of an EDF section in a dispersion compensating Raman amplifier is demonstrated to provide superior performance than Raman only system. It is shown that the multi-channel gain spectrum is quite different form the single-channel case. We have also measured the polarization dependent gain (PDG) of the hybrid amplifier configurations and results show that different configurations of hybrid amplifiers have different PDG effects on long-haul optically amplified link.