波分复用系统中掺铒光纤放大器增益谱特性的实验研究

利用已有４×２５Ｇｂ／ｓ波分复用光纤传输实验系统进行了３×１５０ｋｍ四级掺铒光纤放大器级联传输实验．实验结果得到,由于光纤放大器中掺铒光纤的均匀展宽特性．多路信号同时放大时信道间的增益交叉耦合作用导致各信道增益不同,而影响增益谱特性的根本因素是粒子数反转水平即放大器的饱和深度．     

拉曼+EDFA宽带混合光放大器的实现和设计优化

基于对增益和噪声特性的分析,本文实现了长距离宽带传输系统中由分布拉曼放大器和掺铒光纤放大器中组成的宽带混合放大单元,并提出了混合放大器进行优化设计的方法,特别指出适当调整拉曼放大器和掺铒光纤放大器的增益谱可以实现噪声谱的平坦.     

光纤CATV用掺铒光纤放大器的简化分析

在不考虑放大自发辐射(ASE)对掺铒光纤放大器(EDn)饱和特性影响的条件下,推出了掺铒光纤放大器(EDFA)三能级系统功率传输的解析表达式,简化了理论分析,所得结果也适用于二能级系统.根据该简化分析方法具体计算了前向泵浦时光纤CATV用掺铒光纤放大器(ED队)的信号增益曲线.计算表明,当信号增益约在25db以下,即在光纤CATV用掺铒光纤放大器(EDFA)的工作范围内,简化分析所得的计算结果与较精确的数值计算结果一致.     

掺铒光纤放大器多信道放大的理论和实验研究

本文用ＭｃＣｕｍｂｅｒ理论从掺铒氟光纤中Ｅｒ３＋的发射截面参数推算出其正确的吸收截面参数,据此从理论和实验上研究了具有平坦小信号增益谱的掺铒光纤放大器在光波波分复用系统中应用时可能存在的问题,得到了理论计算和实验结果相一致的结论;提出采用掺铒氟光纤放大器作为＂掺铒光纤放大器＋光波波分复用＂干线系统中的级联放大器并通过调节其工作点的简单办法实现系统的全程信道增益均衡。     

高性参掺铒光纤放大器的优化研究

根据二能级近似的Giles模型,计算了对于给定泵浦功率的最佳掺铒光纤长度,实验研究了掺铒光纤长度对于放大器增益谱形状的影响,通过进一步优化掺铒光纤长度获得了高增益,低噪声指数和宽带平坦增益谱的高性能放大器,并针对在DWDM和长距离多级联放大器系统中的应用提出了改进方案。     

掺铒光纤放大器多信道放大器的理论和实验研究

本文用ＭｃＣｕｍｂｅｒ理论从掺铒氟光纤的Ｅｒ＾３＋的发射截面参数推算出其正确的吸收截面参数，据此从理论和实验上研究了上有平坦小信号增益谱的掺铒光纤放大器在光波波分复用系统中应用时可能存在的问题，得到了理论计算和实验结果相一致的结论：提出采用掺铒氟光纤放大器作为“掺铒光纤放大器＋光波波分复用”干线系统中的级联放大器并通过调节其工作点的简单办法实现系统的全程信道增益均衡。     

利用非线性偏振旋转锁模技术产生0.7nJ,1.5ps光脉冲

为了研究锁模光纤激光器以增益平坦型掺铒光纤放大器作为增益介质对输出特性的影响,采用增益平坦型掺铒光纤放大器结合光纤偏振控制器、偏振相关光隔离器组成锁模光纤激光器,基于非线性偏振旋转锁模技术,实现稳定、自起振锁模运转,得到了中心波长1560nm、重复频率6.495MHz、单脉冲能量0.7nJ、脉宽1.5ps的超短光脉冲。同时实验观察到峰值波长为1557nm和1570nm的双峰值波长锁模脉冲的产生。结果表明,采用增益平坦型掺铒光纤放大器替代普通掺铒光纤组成锁模光纤激光器,可获得较高单脉冲能量的超短光脉冲,锁模脉冲的输出光谱可能出现双峰结构,从而可为超短脉冲光纤激光器设计及实用化提供参考。     

高增益、低DMG少模掺铒光纤及其放大性能研究

空分复用技术是大幅提高单根光纤数据传输容量的重要技术之一。对于长距离模分复用传输系统而言，少模掺铒光纤放大器是补偿光纤传输损耗必不可少的器件。因此，在少模掺铒光纤支持的所有模式中获得均衡增益至关重要，高差分模态增益会降低系统的传输性能。本文通过改进的化学气相沉积技术制备了18μm/124μm少模掺铒光纤，实验演示了基于该光纤的两模掺铒光纤放大器。当使用LP_11b模式泵浦时，该放大器所支持的LP₀₁和LP_11a模式可以在1535～1560 nm波段获得19.4 dB以上的增益，差分模态增益最大为0.66 dB。     

两段级联宽带碲基掺铒光纤放大器特性研究

利用四能级结构速率方程组和光功率传输方程组,研究了在碲基掺铒光纤(EDTF)中内插一个光隔离器、形成两段级联的碲基掺铒光纤放大器(EDTFA)后对EDTFA性能的改善.结果表明,在给定泵浦方式、泵浦功率、纤芯掺杂浓度和输入信号功率条件下,两段级联EDTFA可以有效的抑制光纤中反向传输放大自发辐射(ASE)噪声,降低反转粒子数的消耗,从而提高信号增益、输出功率,并且降低了噪声系数.对不同光纤长度和光隔离器内插在光纤中不同位置的研究表明,当光纤为最佳长度和光隔离器在最佳位置处时,可使短波长信号增益增加10 dB,噪声系数减小1 dB,并进一步增加了放大带宽以及功率转换效率.     

宽带碲基掺铒光纤放大器掺杂特性的理论研究

对WDM系统中宽带碲基掺铒光纤放大器(EDTFA)多信道增益谱特性的研究表明,在给定泵浦方式、泵浦功率和光纤长度的工作条件下,碲基掺铒光纤中铒掺杂浓度对EDTFA各信道信号增益的影响并不相同,相比于长波长信道,短波长信道的信号增益随着光纤中铒掺杂浓度的提高更易趋于饱和及快速衰减状态,同时信号增益谱向长波长方向萎缩.     

All optical gain-locking in erbium-doped fiber amplifiers usingdouble-pass superfluorescence

All optical gain-locking in an erbium-doped fiber amplifier (EDFA) is demonstrated. A double-pass superfluorescence is created by using a broad-band fiber reflector centered at 1530 nm at the output of the EDFA, to lock the gain at 21 dB. Experiments on an eight-channel wavelength-division-multiplexing system shows promise with gain variation between channels of less than 0.6 dB over the input signal power range. While, gain variation with input signal power is about 0.2 dB for all channels     

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     

Polarization dependent gain in erbium-doped fiber amplifiers:computer model and approximate formulas

A computer model for polarization dependent gain (PDG) in Er-doped fiber amplifiers (EDFA) is presented. The model assumes that each erbium ion possesses an ellipsoidal gain surface and that all ion orientations are equally likely. By dividing the ions into subsets based upon orientation and computing the inversion of each subset in the presence of polarized pump and signal waves, the model predicts the dependence of the PDG induced by this polarization hole-burning (PHB) on the design of the EDFA, the signal degree and state of polarization (SOP), and the pump SOP. For moderate gain amplifiers (made from the same fiber) with the same gain peak wavelength and the same compression level, the magnitude of the PDG is nearly independent of the EDFA gain. Internal and random fiber birefringence are included to model real fibers. In fibers which cause the signal SOP to walk rapidly around the Poincare sphere, the PDG is reduced by a factor of 2/3 when compared with a linear polarization-maintained signal. Scrambled signals and partially-polarized saturating tones are also considered. Simple rules are derived for predicting the PDG of a given EDFA     

A study of green wavelength-division multiplexed optical communication systems using cascaded fiber bragg grating

This paper studies the performance analysis of wavelength-division multiplexed optical communication systems (WDM). First, flat-gain erbium doped fiber amplifiers (EDFAs) are seriously needed to obtain proper and equal amplification of all channels. Such amplifiers can be designed by intrinsically modifying the host material or extrinsically using proper filters. In this research, we benefit from both the intrinsic and extrinsic methods to achieve sharp flat EDFA output gain using cascaded fiber Bragg gratings (FBGs). Second, the performance of our technique has been evaluated through calculating the bit error rate (BER) and signal-to-noise ratio (SNR) of a WDM system embedded with the reported EDFA flattening system. The parametric simulations of the FWHM of FBGs, SNR, optical power and the transmission distance have shown a noticeable improved performance. Sending data via an optical WDM system will be proven from comprehensive simulations to achieve high quality signal transmission spectrums, increased transmission distances and low power consumption. By extension, the reported design using cascaded FBGs can also be generalized to equalize the gain of any arbitrary profile.     

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     

Effective suppression of signal-wavelength dependent transients in a pump-controlled L-band EDFA

Typical pump-controlled L-band erbium-doped fiber amplifiers (EDFAs) in a feed-forward scheme give significant transients due to gain difference on wavelength of input signal when only a few channels are left. The fiber Bragg grating added pump-controlled L-band EDFA eliminates the wavelength dependent gain difference and transients.     

Polarization dependent loss induced gain ripple statistics inerbium-doped fiber amplifiers

A Monte-Carlo model is used to simulate the wavelength-dependent polarization dependent loss (PDL) statistics and PDL induced gain-ripple statistics for a chain of concatenated optical elements in an erbium-doped fiber amplifier (EDFA). Simulations indicate that unlike polarization-mode dispersion (PMD), the quadrature sum of PDL overestimates the mean of the PDL distribution. We show that EDFA total PDL variance scales linearly with the individual component PDL variance. Moreover, the relative impact of PDL on the gain ripple is reduced in the presence of the PDL independent gain ripple in the EDFA     

光纤喇曼放大技术及其应用

概述了光纤喇曼放大器的发展情况、分布式喇曼放大器的原理和特性 ,重点阐述了掺铒光纤放大器与喇曼放大技术的组合应用 ;最后指出 ,这两种技术的组合应用能明显提高长距离光纤通信系统性能 ,使掺铒光纤放大器具有更广阔的应用前景。     

高速长波长星间光通信中掺铒光纤放大器应用的理论研究

提出了一个增益自动控制的级联 EDFA系统 ,通过对掺铒光纤光放大理论模型的数值模拟 ,论证了它在高速长波长星间光通信系统中应用的可行性。同时进一步分析了在大信号、高泵浦功率条件下高速光脉冲信号放大过程中的各种畸变特性以及放大的自发辐射对系统信噪比增益的影响。     

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.