掺饵光纤放大器及其在波分复用系统中的应用

介绍了掺饵光纤放大器（ＥＤＦＡ）的原理、组成结构和所用元器件，阐述了ＥＤＦＡ的增益、噪声和增益谱特性，并对ＥＤＦＡ应用于波分复用（ＷＤＭ）系统中带来的增益谱平坦问题进行了讨论。     

光波分复用技术讲座：第二章 掺铒光纤放大器的原理及其在DWDM中的应用

掺铒光纤放大器（ＥＤＦＡ）已成为密集波分复用（ＤＷＤＭ）系统中最关键的组成部分,从ＥＤＦＡ的原理出发,描述其工作过程,并简要介绍了各种状态下的性能特点。在ＤＷＤＭ系统中,ＥＤＦＡ同时放大多个波长,并级联使用,带来了功率及增益平衡等新问题,结合波分复用（ＷＤＭ）系统,讨论了ＥＤＦＡ的增益及功率均衡问题,对目前广泛使用的平衡增益和稳定功率的几种方法进行比较。     

适用于WDM的几种增益平坦的掺铒光纤放大器

近年来，掺铒光纤放大器（ＥＤＦＡ）与波分复用（ＷＤＭ）相结合的传输技术已成为高速率，大容量光通信发展的主流方向。本文分析总结了国外研制适用于ＷＤＭ的增益平坦ＥＤＦＡ的几种有效方案，为适用于ＷＤＭ的ＦＤＦＡ实用化研究提供参考。     

DWDM用增益平坦EDFA研究

本文阐述了ＤＷＤＭ系统对ＥＤＦＡ的要求和ＥＤＦＡ为达到这些要求的几种实现方法。并给出了ＤＷＤＭ用ＥＤＦＡ级联和增益锁定的实验结果。     

声光可调滤波器在光纤通信系统中的应用进展

声光可调滤波器以其宽的调节范围、窄的滤波线宽、多信道并行滤光等特点,在光纤通信系统中作动态增益均衡器具有很多优点。用声光可调滤波器实现ＥＤＦＡ级联的ＷＤＭ系统的动态增益均衡,可扩展增益带宽（～５２ ｎｍ）,提高传输距离 （～ ２４００ ｋｍ）。     

新一代掺铒光纤放大器的设计

波分复用（ＷＤＭ）技术作为改进现存光纤容量的最优秀的技术推动了寻求高性能光纤放大器方面的研究．与ＷＤＭ系统相互兼容的掺饵光纤放大器（ＥＤＦＡ）曾经在光纤网络设计和性能上引起巨大的变革,可以同时传输的通道数达到８个．但是最新经济实用的密集式ＷＤＭ(ＤＷＤＭ）系统则是为１６、３２、４０通道数而设计的,而且１００个通道数的系统在不久的将来也会成为现实。标准ＥＤＦＡ的高效率是由于其高增益,高功率输出、低噪声、宽带和与光纤网的兼容性,然而其他的一些特性对数据的ＤＷＤＭ系统应用则不是那么有效．更宽的带宽,更…     

WDM+EDFA+DCF光纤传输系统中色散补偿方案的分析

由于在ＷＤＭ＋ＥＤＦＡ光纤传输系统中使用常规单模光纤（ＳＭＦ）在１５５０ｎｍ窗口的大色散限制了传输距离,采用色散补偿光纤（ＤＣＦ）进行色散补偿是上前一种较为理想的方法。本文基于光纤ＷＤＭ＋ＥＤＦＡ＋ＤＣＦ的长距离传输系统,讨论了ＤＣＦ色散补偿对光纤非线性效应交叉相位调制和四波混频（ＦＷＭ）的影响,提出了采用ＤＣＦ集总、后置、非完全补偿的色散补偿方案,这种方案可合系统具有更佳的传输性能。     

波分复用信号传输技术

本文介绍了波分复用系统中的多波长信号传输相关技术，主要包括光纤技术、色散管理、增益均衡、增益平坦ＥＤＦＡ及偏振优动等，分析了目前水平的发展方向     

WDM系统中EDFA饱和增益谱特性的实验研究

对ＷＤＭ光纤传输系统中ＥＤＦＡ的增益谱特性的研究表明：在饱和工作状态下，多个信道同时输入时各信道的增益低于相同总输入功率的单个信道的增益，且增益谱宽变窄，增益谱峰值随饱和程度的加深向长波长方向偏移。     

VDM+EDFA系统中光纤非线性效应影响的研究

系统分析了光纤非线性效应对光纤主干网ＷＤＭ＋ＥＤＦＡ扩容的影响，在信道间隔相等的条件下，得出了光纤非线性响应影响下的阈值功率，信道数，信道间隔和ＥＤＦＡ级联数等之间的关系。结果表明，在信道数和信道间隔不同时，ＦＷＭ，ＸＰＭ和ＳＲＳ分别起不同作用；为实现ＷＤＭ＋ＥＤＦＡ技术，每个信道的输入功率必须小于一定值。     

用光纤环路镜实现WDM系统中的EDFA增益均衡

EDFA对不同波长的光产生的增益不同 ,这种增益不平坦特性成为 WDM系统中高速率、大容量信息传输的障碍 ,因此对 EDFA的增益进行均衡就显得特别重要。介绍用光纤环路镜实现 EDFA增益均衡的机理 ,并进行了实验 ,结果表明该方法简单易行 ,均衡效果显著     

Gain equalization of EDFA cascades

Investigates the impact of wavelength-dependent erbium-doped fiber amplifier (EDFA) gain spectrum on multichannel direct-detection lightwave transmission systems employing multiple amplifiers. An analysis is presented which quantifies the constraints imposed by received power imbalance, signal-to-noise ratio (SNR), and receiver sensitivity on an EDFA cascade. Expressions are derived which relate the system constraints to the EDFA gain imbalance, bit rate, number of channels, and receiver dynamic range. Results demonstrate that when four-wave mixing (FWM) is compensated in an 11-channel system, received power imbalance can impose a significant constraint on transmission distance when the EDFA gain imbalance is greater than 1 dB or when bit rate is less than 1.8 Gb/s. In addition, performance of the preemphasis gain equalization technique is studied for multichannel systems employing APD or p-i-n/FET direct-detection optical receivers. Simple expressions are derived which can be used to quantify the increase in transmission distance obtained when employing preemphasis equalization. Results indicate that equalization of the received power spectrum can provide a two- to four-fold increase in the transmission distance when using APD receivers, compared to a one- to two-fold improvement with p-i-n/FET receivers. Analytic results are compared with results obtained by proven simulation methods and found to be in good agreement     

Gain equalization of EDFA's with Bragg gratings

Flat-gain amplifiers are needed to ensure proper amplification of every channel in wavelength-division-multiplexed communication systems. Such amplifiers can be realized by combining a precisely tailored filter with an erbium-doped fiber amplifier (EDFA). In this letter, we show that Bragg gratings can lead to accurate EDFA gain equalization. Reflection and transmission gratings have been used to demonstrate gain equalization over 32 nm with excursion inferior to ±0.1 and ±0.3 dB, respectively. A maximum 0.04-dB noise-figure penalty results from this process. By extension, Bragg gratings could also equalize the gain of any arbitrary gain profile, over any arbitrary bandwidth     

Application of preemphasis to achieve flat output OSNR intime-varying channels in cascaded EDFAs without equalization

In this paper, we present a new method for optical signal-to-noise ratio (OSNR) equalization of wavelength division multiplexed (WDM) channels at the end of a cascade of several erbium-doped fiber amplifiers (EDFAs) by use of preemphasis, as well as the proper choice of EDFA design parameters. Identical OSNR at the end of the cascade ensures better signal detection and quality of service. The dynamics of the equalizing method have been demonstrated by simulation for single- and double-stage amplifier designs using a numerical model incorporating time variation effects in EDFA. Calculations are based on the solution of a transcendental equation describing the dynamics of the reservoir, i.e., the total number of excited ions, for each EDFA. Traffic on eight WDM channels is modeled as statistically independent ON-OFF time-slotted sources. In addition, we investigate the effect of gain clamping of the first amplifier in the cascade-by implementing a ring laser and propagating the lasing power through the cascade-on the statistics of OSNR variation. We show that it is possible to achieve dynamic OSNR equalization for a WDM system by the use of preemphasis and an appropriate choice of EDFA parameters, without resorting to optical equalization filters. Most previous equalization methods are static with flat gain for a given inversion level in the amplifier. Changes in the input power (due to network reconfiguration or packetized traffic) will lead to a varying inversion level and hence non optimal equalization     

具有动态增益均衡特性的低噪声全光增益箝位EDFA

针对全光增益箝位EDFA噪声指数恶化以及用于WDM系统时增益动态变化两个问题,提出具有动态增益均衡特性的低噪声全光增益箝位EDFA,在35 nm范围内,输入信号功率在-40 dBm到0 dBm之间变化时,增益变化被箝制在1 dB范围内,同时保持单波长输入噪声指数<4.5 dB,多波长输入增益谱不平坦度<0.4,噪声指数<5.5 dB,有效解决了以上问题.     

EDFA-based DWDM lightwave transmission systems with end-to-end power and SNR equalization

An approximate analysis is presented which can be used to predict the performance of power and signal-to-noise ratio (SNR) equalization schemes when applied to dense wavelength-division multiplexing (DWDM) lightwave systems employing erbium-doped fiber amplifier (EDFA) cascades. Expressions are provided which relate the maximum number of amplifiers, EDFA gain imbalance, bit rate (R/sub b/), transmitter power, receiver dynamic range and number of channels. The relative advantages of these two equalization strategies are quantified by comparing the maximum number of amplifiers allowed by each scheme. It is shown that, while SNR equalization represents, on balance, the more desirable equalization strategy for future EDFA-based DWDM lightwave transmission systems, under certain conditions power equalization may be a better choice. When employing an APD receiver, for instance, power equalization can support 1.9 times more amplifiers than SNR equalization. However, when employing the more conventional preamplified PIN/FET receiver, SNR equalization can support 1.7 times more amplifiers than power equalization.     

Synthesis of long-period fiber gratings with the inverted erbium gain spectrum using the multiport lattice filter model

This paper proposes an accurate modeling technique of concatenated long-period fiber gratings (LPFGs). The proposed technique is then applied to the synthesis of LPFGs for the erbium gain equalization using both the simulated annealing and the steepest descent minimization technique. A piecewise-uniform LPFG is theoretically synthesized according to the inverted gain spectrum of a commercially available erbium-doped fiber amplifier (EDFA) over the range of 1525-1570 nm. Sensitivity analysis of the designed structure is presented by Monte Carlo simulation with regard to the manufactured amplitude mask. To verify a synthesizing technique using the proposed modeling, the piecewise-uniform LPFGs for gain flattening of EDFA are fabricated and their spectra are also presented experimentally.     

Effects of signal power control strategies and wavelength assignment algorithms on circuit OSNR in WDM networks

Software-defined networking is enabling wavelength-division multiplexed (WDM) networks to be programmable down to individual components. While taking into account typical gain and noise figure profiles of erbium-doped fiber amplifier (EDFA) components, the authors consider a number of signal power control strategies and compare their performance in terms of achievable lightpath optical signal-to-noise ratio (OSNR). These strategies are applied network-wide to concurrently control the gain of each individual amplifier and the signal power equalization at each reconfigurable optical add/drop multiplexer. Simulation and (in part) experimental results show that the lightpath OSNR is affected by three factors: the EDFA gain control strategy, power equalization strategy and wavelength assignment (WA) algorithm. A trade-off between lightpath average OSNR and OSNR variance across the WDM channels is also noted. Experimental work is conducted using a five-node meshed WDM network testbed proving both feasibility and effectiveness of a coordinated use of signal power control strategies and WA algorithms.     

多波长掺铒光纤激光放大器的放大特性研究

为了研究多波长掺铒光纤激光放大器的放大特性,在单频放大器的基础上,忽略放大自发辐射,推导了描述多波长掺铒双包层光纤放大器的稳态速率方程组,建立了多波长掺铒光纤放大器的理论模型。利用该模型对单波长放大、双波长放大、四波长放大的特性,进行了数值模拟和理论分析;以四波长的激光信号放大为例,对多波长掺铒光纤放大器的放大特性,均衡增益特性进行了研究。结果表明,在单波长注入情况下,光纤放大器的掺杂光纤存在最佳光纤长度为8m;与小信号放大不同,大功率掺铒光纤放大器在1530nm~1560nm之间增益谱趋于平坦;双波长放大输出功率差随着波长间隔的增加线性增大波长间隔为20nm时,通过调节输入信号功率比可以实现最大功率差6.855W的功率均衡补偿;四波长放大时,通过信号功率配比之后的四波长激光输出功率最大偏差为0.28W,在一定范围内实现了均衡增益。这一结果对于掺铒光纤激光的多波长激光输出以及在激光多普勒测风雷达中的应用具有一定帮助。