Simulative investigation of the impact of EDFA and SOA over BER of a single-tone RoF system

In this paper, we investigate the impact of EDFA and SOA amplifiers over BER and Q-parameter of a Radio-over-Fiber (Rof) system consisting of two different system set-ups using direct- and external-laser modulation techniques. In this work, we also measured and compared the electric Rf power at receiver at different modulating Rf frequencies up to 20 GHz using two different optical amplifiers, i.e. EDFA and SOA. Further, we also compared the received electric Rf power at different optical powers without and with different optical amplifiers. An improvement of −11 dB (approx.) of received Rf power was observed using EDFA with the external modulation technique, on comparing with direct modulation.     

Analysis of 2.5 Gbit/s GPON downlink optical-receiver performance

In the gigabit-capable passive optical network (GPON) optical communication system, the selection of fiber and system performance-analysis is the key links for the realization of system function. Especially the characteristic budget and parameter setting of downlink receiver are topped the list. The analysis of receiver power penalty can reduce the influence on receiver sensitivity and bit error rate (BER) that caused by waveguide dispersion and pulse widening. This article will simulate the performance of GPON downlink receiver, then analyze typical characteristics such as Four Wave Mixing (FWM), Erbium-Doped Fiber Amplifier (EDFA), system eye pattern and Q factor and so on, so as to validate the feasibility of the optical downlink.     

Impact analysis on performance optimization of the hybrid amplifier (RA + EDFA)

The configuration of the hybrid amplifier (Raman Amplifier: RA + Erbium-Doped Fiber Amplifiers: EDFA) has been introduced and the restriction conditions of its optimum design have also been analyzed and discussed, and then the ASE noise and Rayleigh noise in Raman Amplifier (RA) as well as their influences on the Signal Noise Ratio (SNR) of the receiver have been analyzed in depth. Furthermore, the influences, which result from these noises, on the performances of the optimum design for the hybrid amplifier (RA + EDFA) have thoroughly been researched. Finally, some significant conclusions to play an important role in guiding the optimum design of the hybrid amplifier have been obtained by the above analyses and researches.     

掺铒光纤放大器在多路模拟光纤传输系统中应用

对应用掺铒光纤放大器的副载波频分复用模拟电视光纤传输系统的噪声和失真进行了实验研究，利用掺铒光纤放大器作为系统的功率提升和中继放大器，分别成功地进行了１８５ｋｍ和２１５ｋｍ的系统传输试验     

Power penalty in multitone radio-over-fibre system employing direct and external modulation with optical amplifiers

This paper presents a multitone RoF system employing a central station and a remote antenna station to transmit modulated microwave or mm-wave signals. Two configurations of the system employing direct and external modulation are presented. First, at the central station, the modulating signal is directly and externally modulated at 1549.5 and 1550.5 nm, respectively, and the combined signal is then transmitted using wireless mode. In the second configuration, the combined signal is transmitted over 20 km to the remote antenna station using optical fibre connectivity. At the remote antenna station, both channel wavelengths are separated and amplified with an EDFA and SOA and are detected. The demonstration results show that there exists a small power penalty between the direct and the external modulation. But a large power penalty is reported depending upon the choice of optical amplifier viz. EDFA or SOA. Better performance is recorded in later case. The results also show that power is being distributed among the operating frequency and sidebands adjacent to it after transmission over a fibre link.     

The L-band EDFA of high clamped gain and low noise figure implemented using fiber Bragg grating and double-pass method

The L-band erbium-doped fiber amplifier (EDFA) of low noise figure and high clamped-gain using gain-clamped and double-pass configuration is presented in this paper. A total of five different configurations of EDFAs by reflection scheme with single forward pumping schemes are examined and compared here. Among these configurations, we first find the configuration of 1480-nm pumped L-band EDFA with optimum gain and noise figure value. To further minimize the gain variation, a fiber Bragg grating (FBG) with 1615-nm center wavelength and 1-nm bandwidth is determined and added in double-pass L-band EDFA. The gain variation and maximum noise figure of EDFA while channel dropping is investigated. As the number of channel dropping from 32 to 4, the L-band type-A EDFA keep the variation of gain within 2.9 dB and the maximum noise figure below 5 dB with each channel’s input power of −23 dBm.     

有源循环式光脉冲复制系统的输出特性研究

改进并验证了一种基于有源循环光纤延迟线的模拟光脉冲信号复制技术.实验系统采用低增益掺铒光纤放大器补偿循环损耗.进行了光脉冲信号复制的仿真和实验,在掺铒光纤放大器增益为6.774 dB,光滤波器－3 dB,带宽为0.8 nm时,测得第500个复制光脉冲的信噪比为31 dB.仿真和实验结果表明,选用小增益掺铒光纤放大器可以实现低于3 dB的噪音系数,降低掺铒光纤放大器的放大自发辐射噪音并提高输出脉冲序列的信噪比,有望成为提高光脉冲复制器性能的一种新方法.在系统中插入窄带光滤波器等手段也是改善信噪比的有效措施.     

Absorption line profile recovery based on TDLS and MEMS micro-mirror for photoacoustic gas sensing

A novel and efficient absorption line recovery technique is presented. A micro-electromechanical systems (MEMS) mirror driven by an electrothermal actuator is used to generate laser intensity modulation through the mirror reflection. Tunable diode laser spectroscopy (TDLS) and photoacoustic spectroscopy (PAS) are used to recover the target absorption line profile which is compared with the theoretical Voigt profile. The target gas is 0.01% acetylene (C2H2) in a nitrogen host gas. The laser diode wavelength is swept across the P17 absorption line of acetylene at 1535.4 nm by a current ramp, and an erbium-doped fibre amplifier (EDFA) is used to enhance the optical intensity and increase the signal-to-noise ratio (SNR). A SNR of about 35 is obtained with 100 mW laser power from the EDFA. Good agreement is achieved between the experimental results and the theoretical simulation for the P17 absorption line profile.     

利用光纤光栅对实现双波长增益控制掺铒光纤放大器特性的实验研究

控制激光的弛豫振荡和空间烧孔现象的存在 ,对全光增益控制掺铒光纤放大器 (EDFA)的性能产生劣化影响。采用一种新颖简单的利用两对光纤光栅对形成谐振腔结构 ,实现双波长增益控制掺铒光纤放大器。由两个不同波长的激光共同承担增益控制的任务 ,降低了控制激光引起的空间烧孔现象和瞬态输出变化。在动态工作条件下 ,双波长激光增益控制掺铒光纤放大器显示出优越的特性 ,适用范围扩展为普通单波长增益控制掺铒光纤放大器的两倍 ,能够适应 0～ 43kHz的上下载频率。     

Investigation of Hybrid Optical Amplifiers for Dense Wavelength Division Multiplexed System with Reduced Spacings at Higher Bit Rates

Abstract

This article proposes various combinations of optical amplifiers for a dense wavelength division multiplexed system and investigates the impact of reduced channel spacing at high bit rates in terms of quality factor, bit error rate, eye closure, and output power. It is reported that the hybrid optical amplifier (Raman–erbium-doped fiber amplifier [EDFA]) provides better results with a maximum covered single span distance (220 km) at channel spacing of 6.25 GHz. The maximum acceptable bit rate for the 12.5-GHz channel spacing dense wavelength division multiplexed system is also investigated, and the recommendation is provided that for the Raman–EDFA, Raman–EDFA–Raman, EDFA–Raman–EDFA, and EDFA–semiconductor optical amplifier–EDFA, the operating bit rate should not be greater than 20, 16, 19, and 20 Gbps, respectively.     

Bright prospects for erbium-doped fiber amplifiers in future lightwave communication systems

In the light of achievable component performance from both a theoretical and an experimental point of view, the applications of erbium-doped fiber amplifiers (EDFA) in long distance repeaterless digital transmission and analog cable TV distribution is discussed. In digital repeaterless systems, EDFA postamplifiers are capable of output powers over + 15 dBm; preamplifiers and remotely pumped amplifiers improve system budgets by more than 7 dB and 13 dB, respectively, when compared to a conventional APD (avalanche photodiode) receiver. In analog AM-VSB TV distribution networks, EDFA postamplifiers improve the power budget by more than 10 dB, and cascaded EDFA repeaters hold promise for power budgets over 35 dB, allowing large splitting ratios in the network.     

L-band EDFA 性能与增益光纤长度关系的分析

分析和模拟L_band EDFA的增益特性对其优化设计和实验有着重要的意义。基于Giles模型,数值模拟了L_band EDFA中的信号光、泵浦光和放大自发辐射(ASE)在一定泵浦功率下与铒光纤长度的关系;分析了L_band EDFA本征增益平坦的产生机理;数值模拟了小信号增益平坦特性。结果表明,在一定的泵浦功率下,如果在所选择的L_bandEDFA中铒光纤长度合适,则不需要任何平坦化处理就可以得到比较平坦的增益谱线。     

L-Band掺铒光纤放大器的优化设计

提出了泵浦分配两段级联,并利用前向ASE推动下一级EDF工作的L-Band放大器的新结构.基于Giles模型并考虑了ASE噪声的影响,运用数值模拟算法系统分析了泵浦光功率分配和铒光纤分配比例对这种EDFA性能的影响.最后优化得到高增益且增益谱平坦的L-Band EDFA,其在输入信号光功率为-20 dBm时,在1571～1608 nm范围内,增益值高达35 dB,增益偏差小于1 dB.     

Simulative investigation the impact of optical amplification techniques on single- and dual-electrode MZM and direct modulator's in single-tone RoF system

Since the introduction of erbium-doped fiber amplifier (EDFA) in optical fiber communication systems at 1550 nm, the fiber loss is no longer considered as the limiting factor but the fiber dispersion and chirp parameters play an important role in degrading the performance of optical communication systems. Further, the invention of external modulators of Mach-Zehnder (MS) type minimizes the transmission power penalty due to fiber chromatic dispersion as these modulators are consider almost chirp-free modulators. Also, better suppression of nonlinear distortions consists of harmonic distortions (HDs) and intermodulation distortions (IMDs) were achieved by using Mach-Zehnder external modulator [8]. In this work, a simulation comparison of external- and direct-modulation schemes using different optical amplifiers; SOA and EDFA in single-tone RoF system is reported. A single-tone channel of 20 GHz is transmitted over single-mode fiber (SMF) either externally modulated by using single-electrode (SEMZM) - and dual-electrode (DEMZM) - Mach-Zehnder modulator or by direct-modulation scheme. Better improvements in the measurement of received RF power of a 20 km linked single-tone RoF system are achieved by using SEMZM with EDFA, which means maximum optical link is achieved between Central Office (CO) and Base Station (BS). Further, this scheme provides better BER as compare to other schemes discussed in this paper.     

低噪声、高增益的L -band EDFA的实验研究

针对传统的L-band EDFA的工作效率低,提出了一种基于单根光纤光栅、泵浦分配、两段级联的EDFA的新结构,其中的光纤光栅用来反射无用的后向C-band ASE.系统地研究了泵浦比例和光纤光栅波长对增益噪声指数的影响关系.最后经实验验证,得到了低噪声、高增益的L-band的EDFA.其在输入信号光（1570 nm）功率为-30 dBm及泵浦功率为70 mW时,增益为22.26 dB,增益噪声指数为4.96 dB.     

PDL-Compensated Mechanically Induced Long-Period Grating for EDFA Gain Flattening

We present and demonstrate a polarization-insensitive mechanically induced long-period fiber grating (MLPG) for EDFA gain flattening. By forming a 90° fiber rotator in the middle of the MLPG the PDL of the MLPG was substantially reduced. The PDL-compensated MLPG was able to flatten the ASE spectrum of an EDFA successfully without deterioration of the polarization characteristics.     

PDL-Compensated Mechanically Induced Long-Period Grating for EDFA Gain Flattening

We present and demonstrate a polarization-insensitive mechanically induced long-period fiber grating (MLPG) for EDFA gain flattening. By forming a 90° fiber rotator in the middle of the MLPG the PDL of the MLPG was substantially reduced. The PDL-compensated MLPG was able to flatten the ASE spectrum of an EDFA successfully without deterioration of the polarization characteristics.     

Dynamic-channel-equalizer using in-line channel power monitor and electronic variable optical attenuator

We propose and demonstrate a polarization-insensitive dynamic-channel-equalizer (DCE) for compensating erbium-doped-fiber-amplifier (EDFA) amplified signals after dynamic optical add/drop. The DCE can be monolithically integrated on silicon-on-insulator (SOI) platform and is potentially low cost and compact. The DCE can compensate complicated gain slope shape, which may be generated in cascaded EDFAs or deliberate channel add/drop, based on individual channel equalization. Fifteen-decibel receiver sensitivity improvement at 10 Gb/s bit-error-rate (BER) measurement of 10⁻⁹ was achieved in the compensated channel by removing cross-gain-modulation generated by neighboring channel add/drop.     

Study on EDFA Gain Tilt and Nonlinear Distortion in an AM-VSB CATV Optical Fiber Transmission System

1IntroduCtionAMVSB(~litUdemodulationwithvestigialsideband)CATVoPticalfibertrandriSSdrisystemiswidelyaPpliedduetocomplete1ycomatibilitywtthekistingCATVtechntheyandoccuPationaverynarrowband.Theopticalpowerbudgetofthesystemistoollttle(about5~8dBm)toreallzealDngdistancetransndssion,andoPticalmodulationdegreeisalsorestrainedinanarrowrangeinordertOguaranteethenonlinearrequlrementssinceitissensitivetOthenonlineardistortion.EDFAisintroducedintothesystemtoimProvetheopticalpoWrbudget.Indongs…     

基于长周期光纤光栅滤波器的掺铒光纤放大器理论和实验研究

从理论和实验上研究了带有高频二氧化碳激光写入的低成本长周期光纤光栅（LPFG）掺铒光纤放大器（EDFA）.结果表明,单波长和多波长EDFA的性能都可以通过在掺铒光纤（EDF）中插入长周期光纤光栅用作自发辐射噪声（ASE）滤波器或增益平坦器来提高性能.优化设计了带LPFG噪声滤波器的线放EDFA,与没有LPFG噪声滤波器相比,线放的噪声和小信号增益分别被减小和提高了约0.5 dB和7 dB。通过在多波长EDFA的EDF中插入一个LPFG增益平坦滤波器的方法,获得了1.5 dB的增益平坦度,与没有LPFG平坦器相比,EDFA的噪声被减小了0.1 dB,增益被提高了1 dB.