基于FBG铥钬共掺光纤放大器反向ASE的再利用

Reusing the Backward ASE in Tm-Ho Co-Doped Fiber Amplifiers Based on FBG

针对铥钬共掺光纤放大器在放大2μm以上长波段信号光时因存在反向放大的自发辐射(ASE)而造成的放大效率浪费的问题,提出了在放大器输入端插入一个中心波长为1950nm的光纤光栅(FBG)的方案,并从理论上研究了光栅参数对放大器在2μm以上波段增益特性的影响。通过数值模拟给出了几种不同的铥钬掺杂比例下、有无FBG时,放大器对2040nm信号光的增益随光纤长度的变化曲线,分析了插入FBG后放大器最大增益和对应的最佳光纤长度的变化,以及这种变化对铥钬掺杂比例的依赖性。通过模拟放大器输入端的反向ASE光谱,以及抽运光、信号光、ASE与FBG反射光功率沿光纤传输的演化行为,解释了FBG对放大器产生影响的根本原因,并进一步指出为提高放大器长波段增益而加入短波段FBG的适用条件。并初步研究了加入FBG对放大器增益谱及噪声特性的影响。

Regarding to the problem that the backward amplified spontaneous emissions（ASE）in Tm-Ho co-doped fiber amplifier reduce the amplification efficiency beyond 2μm band,the influence on gain property beyond 2μm band by inserting a 1950 nm fiber Bragg grating（FBG）into the input terminal of the amplifiers with different Tm/Ho doping ratios is studied theoretically.Simulation results of the 2040 nm signal gain over the fiber length with or without FBG are given under several different Tm/Ho doping ratios in order to analyze the variations of maximum gain and corresponding optimal fiber length due to the insertion of FBG,as well as the dependence of the variations on Tm/Ho doping ratio.The influence of FBG is explained through simulating the backward ASE spectrum at z=0,and the propagation of pump,signal,ASE and reflected light from FBG along the fiber.Discussions on the simulation results further point out the applicable conditions of short-band FBG for improving long-band gain of amplifier.In addition,the influences on gain spectrum and noise characteristics by FBG are also investigated.