A detailed experimental study on single-pump Raman/EDFA hybrid amplifiers: static, dynamic, and system performance comparison

This paper presents an experimental study on the performance comparison of three different schemes of single-pump dispersion-compensating fiber (DCF)-based Raman/erbium-doped fiber amplifier (EDFA) hybrid amplifiers together with a DCF-based Raman-only amplifier in terms of static properties, dynamic properties, and system impact: Raman-only amplifier (Type I), Raman/EDFA hybrid amplifiers recycling residual Raman pump in a cascaded EDF located either after (Type II) or prior to (Type III) a DCF, and a Raman-assisted EDFA (Type IV), the concept of which was proposed by Kurosawa et al. With respect to the overall gain and system impact based on bit error rate (BER) measurements in a transmission system, the hybrid amplifier of Type II was found to have the best performance among the four types while the Raman-only amplifier shows the best tolerance to transient response.     

Dispersion-compensating Raman/EDFA hybrid amplifier recycling residual Raman pump for efficiency enhancement

We experimentally demonstrate a novel concept of the dispersion-compensating Raman/erbium-doped fiber amplifier hybrid amplifier recycling residual Raman pump for increase of overall power conversion efficiency. The proposed dispersion-compensating hybrid amplifier system has only one pump source for Raman amplification in the dispersion-compensating fiber (DCF) and the residual pump power after the DCF is recycled for secondary signal amplification in an erbium-doped fiber cascaded to the DCF. Using the proposed scheme, we achieve the significant enhancement of both signal gain and effective gain-bandwidth by 15 dB (small signal gain) and 20 nm, respectively, compared to the performance of the Raman-only amplifier.     

On the optimization of hybrid Raman/erbium-doped fiber amplifiers

A comprehensive theoretical study on the optimal configuration of hybrid Raman/erbium-doped fiber amplifiers has been carried out yielding a closed form analysis. In order to compare different system configurations, a weight for the impact of fiber nonlinearities has been introduced. The maximum reachable distance has been evaluated as a function of the span length and nonlinear weight, given a target optical signal-to-noise ratio     

TDFA/Raman hybrid amplifiers covering the entire S-band pumped by a single laser

Hybrid amplifier configurations are reported cascading one Raman and one or two Tm/sup 3+/-doped fiber stages, using a single pump at 1426 nm, allowing seamless amplification of the entire S-band (1460-1530 nm). Different configurations were studied, with gain over the entire band width and peak gain up to 24 dB. Noise figure as low as 7 dB was achieved.     

混合放大器(Raman+EDFA)在10 Gbit/s长距离传输中的应用

文章介绍了拉曼放大器(RA)与掺铒光纤放大器(EDFA)组成的混合放大器在10Gbit/sSDH系统中的应用.在160km的G.652光纤线路中,在没有前向纠错(FEC)的情况下,采用混合放大器能够将系统的接收灵敏度提高到-37.5dBm.将采用混合放大器的系统结构与另外两种系统结构进行比较和分析,指出混合放大器的优越性.     

Performance comparison of GaInNAs vertical-cavity semiconductor optical amplifiers

This paper reports on theoretical and experimental investigations of the influence of the number of GaInNAs quantum wells (QWs) on performance of 1.3-/spl mu/m vertical-cavity semiconductor optical amplifiers (VCSOAs). Full characterization is carried out for two optically pumped VCSOAs with 6 and 15 QWs in the active layer. The 15-QW amplifier is found to be more efficient for amplification purposes but the highest gain to date was obtained for a 6-QW GaInNAs VCSOA, 19-dB on-chip gain in single-mode operation, having a top mirror reflectivity of 97.7%. At high-gain and for low enough reflectivity, the intrinsic noise figure is smaller than 5 dB.     

Merit of hybrid EDFA/Raman amplification in fixed‐grid all‐optical network exploiting multirate transponders

The constant need to improve network capacity and reduce power consumption in current fixed‐grid WDM networks motivates researchers to find alternative solutions other than replacing the deployed equipment. One of the possible solutions is the use of hybrid EDFA/Raman amplifier, which improves signal‐to‐noise‐ratio in a point‐to‐point link. This work aims at quantifying, by means of a detailed power model, the effect of these novel ideas on the power consumption of the network, which is key to build a future green Internet. In particular, we consider the use of a randomly generated topology of 20 nodes to study the effect of hybrid amplification, fiber type, fiber span length, and sensitivity to average link length and average traffic per node. Results show that hybrid amplification in moderate pumping regime minimizes total network power consumption for networks made up of all 3 fiber types in particular for nonzero dispersion‐shifted fiber.     

Wide-band and gain-flattened hybrid fiber amplifier consisting ofan EDFA and a multiwavelength pumped Raman amplifier

A wide-band and finely gain-flattened hybrid fiber amplifier is realized. The seamless 3.0-, 1.3-, and 1.0-dB bandwidths of 80, 76, and 69 nm with relative gain-flatness of 11.3%, 4.7%, and 3.7%, respectively, are achieved for the first time using the amplifier. The amplifier consists of an erbium-doped fiber amplifier, which has a short fluoride-based erbium-doped fiber, a discrete Raman amplifier, which has two isolated Raman fibers pumped simultaneously at three wavelengths, and a small-peak-loss gain-equalizer. The amplifier also yields optical noise figures under 6.0 dB     

掺铒光纤放大器性能参数测试

阐述了掺铒光纤放大器EDFA的基本原理,介绍了EDFA性能参数测试的一般方法,对插入测量法进行了改进,使其更精确。利用改进后的插入法对980nm波长泵浦的EDFA在1530—1560nm间的增益和噪声系数进行了测量,绘制出了性能曲线。     

240-km CWDM transmission using cascaded SOA Raman hybrid amplifiers with 70-nm bandwidth

We demonstrate the cascading of broad-band semiconductor optical amplifier-Raman hybrid amplifiers which provide nearly flat gain over 70 nm. A coarse-wavelength-division-multiplexing transmission system consisting of three spans of 80 km shows uniform performance and <1-dB power penalty.     

光纤拉曼放大器的优化设计

文章介绍了一种设计多波长泵浦光纤拉曼放大器（FRA）的方法以及怎样用此方法实现需要的增益曲线。利用这种方法仿真实现了增益接近20dB、平坦度小于0.2dB的拉曼放大器，它与现有的拉曼放大器相比具有更平坦的增益曲线。     

喇曼光纤放大器的几项关键技术

喇曼光纤放大器具有优越的宽带性能 ,是现代宽带通信的较理想放大器。它的实用化得益于一些关键性技术的发展。对喇曼光纤放大器的最新发展进行了研究 ,对其中的关键性技术进行了分析、对比 ,以期有利于今后的实用化研制工作     

Hybrid fiber amplifiers consisting of cascaded TDFA and EDFA for WDM signals

The detailed gain characteristics of hybrid fiber amplifiers that consist of cascaded thulium-doped fiber amplifiers (TDFAs) and erbium-doped fiber amplifiers (EDFAs) are reported. The experimental results showed that the hybrid amplifiers have gains of over 20 dB with the bandwidth of more than 80 nm in the wavelength range between 1460 and 1560 nm. The low noise figure (NF) below 7 dB was obtained in 1460-1540 nm when placing a TDFA in the first stage followed by an EDFA and in 1480-1560 nm when placing amplifiers in a reversed order. The gain of TDFA and EDFA was optimized for minimizing the gain variation ratio (GVR=(maximumgain-minimumgain)/minimumgain: in the unit of decibels) of the hybrid amplifiers, and it could be minimized to less than 0.4 for the amplifiers that have gain in the wavelength region from 1460 to 1537 nm. The gain-equalization technique was applied, and the hybrid amplifier that had an average gain of 20 dB, a gain excursion of less than 2 dB, an output power of 14.5 dBm, and an NF of less than 7 dB in the 77-nm gain band was achieved.     

Performance comparison of integrated fully-differential filterless class-D amplifiers with different feedback techniques

Two integrated stereo fully differential filterless class-D amplifiers are presented in this paper. The object is to develop a modulation of a class-D audio amplifier with high power efficiency in this paper. The traditional H-bridge class-D audio amplifier has a shortcoming of large signal distortion which is worse than realized. However, the proposed circuit improves the drawback and provides high power efficiency at the same time. The circuit implements a modified scheme of pulse-width modulation. In this paper, we presented two class-D amplifiers, compared their differences and explained why the efficiency and distortion performance can be modified. The increase in total harmonic distortion (THD) is due to non-linearity in the triangle wave. To overcome this problem, a negative feedback from the output of the switching power stage is adopted to reduce the THD. When a 0.7-V_PP and 1 kHz sine wave is used as an input signal, the minimum THD is 0.029 % and the maximum power efficiency is 83 %. The fully differential class-D audio amplifier is implemented with a TSMC 0.35-μm 2P4M CMOS process, and the chip area is 2.57 × 2.57 mm² (with PADs).     

Modeling of photonic crystal fiber Raman amplifiers

An accurate model has been developed to study photonic crystal fiber Raman amplifiers. The proposed approach calculates the Raman gain efficiency starting from the knowledge of the fiber cross-sectional characteristics, i.e., the geometric parameters and the germania concentration in the doped area. The model allows the study of the Raman amplification process in a photonic crystal fiber with any air-hole dimension and disposition, with or without a central doped area, as well as in standard single-mode fibers with an arbitrary refractive-index profile. This flexibility allows identification of the optimum values of the physical and geometrical photonic crystal fiber parameters, and thus it guarantees an efficient design for Raman amplifiers. For example, a Raman gain of 13.7 dB at 1554.8 nm has been obtained with a 6-km-long low-loss germania-doped triangular photonic crystal fiber with d//spl Lambda/=0.44 and /spl Lambda/=4.2 /spl mu/m.     

分布式光纤喇曼放大器实验研究

为了对后向抽运分布式宽带光纤喇曼放大器的特性进行实验研究,采用多波长1426nm,1440nm,1460nm,1475nm和1495nm的半导体激光器作为抽运源,实现了C+L波段近80nm带宽的信号光放大,获得了比较好的平坦增益、偏振相关增益,系统平均开关增益为10.7dB,增益平坦度为1.5dB,最大噪声指数为-1.96dB,偏振相关增益小于0.4dB。结果表明,光纤喇曼放大器的抽运源波长、功率选择比较合理,系统所有技术指标均满足光纤通信使用要求。这一结果将对通信产业化发展有着重要的指导作用。     

分布式光纤喇曼放大器实验研究

为了对后向抽运分布式宽带光纤喇曼放大器的特性进行实验研究,采用多波长1426nm,1440nm,1460nm,1475nm和1495nm的半导体激光器作为抽运源,实现了C+L波段近80nm带宽的信号光放大,获得了比较好的平坦增益、偏振相关增益,系统平均开关增益为10.7dB,增益平坦度为1.5dB,最大噪声指数为-1.96dB,偏振相关增益小于0.4dB.结果表明,光纤喇曼放大器的抽运源波长、功率选择比较合理,系统所有技术指标均满足光纤通信使用要求.这一结果将对通信产业化发展有着重要的指导作用.     

Gain saturation spectrum of backward-pumped broad-band Raman amplifiers

The gain saturation of optical amplifiers due to changes in wavelength-division-multiplexed channel loading is characterized using a technique that determines the saturation effect on each channel. This channel gain saturation (CGS) measurement is applied to a broad-band backward-pumped Raman amplifier and used to study how the CGS spectral tilt is controlled by the relative contributions of the pump-to-pump and channel-to-channel interactions. The CGS is also used to measure the gain dependence on the channel add-delete pattern.     

Quantitative analysis of Rayleigh crosstalk in Raman amplifiers

Exact and approximate analytical formulas for the inband crosstalk caused by discrete reflection followed by Rayleigh backscattering are derived. Also, a simplified expression for the double Rayleigh backscattered power is found and the total crosstalk in terms of elementary functions is calculated. Results of measurements performed in a nonzero dispersion-shifted fibre agree with theoretical predictions within 1 dB.     

Optimal design of flat-gain wide-band fiber Raman amplifiers

We present a novel method for designing multiwavelength pumped fiber Raman amplifiers with optimal gain-flatness and gain-bandwidth performance. We show that by solving the inverse amplifier design problem, relative gain flatness well below 1% can be achieved over bandwidths of up to 12 THz without any gain equalization devices. This constitutes a substantial improvement in gain flatness compared to the existing wide-band optical fiber amplifiers