Study On The L-band Variable Gain EDFA

C-band variable gain EDFA is employed successfully and becoming more and morewelcome in applications. as the EDFA operating bandwidth expanding, L-band variablegain EDFA should be deployed in the actual application.This thesis analyses the amplifying principle of L-band EDFA. The key issues indeveloping L-band variable gain EDFA are the low pump conversion efficiency(PCE) andbad noise figure(NF) performance. In this thesis, the theory analyses and experimentalstudy are done on the L-band EDFA key iusses and the root reason of the key issues isindicated. Analyzing on pumping mechanism, amplifying process and transientcharacteristic is done. Several optical configurations simulation results indicateanti-propagating pump has much higher PCE than co-propagating pump, but much worsedeteriorated NF. Multi-stage optical configuration has better PCE and NF than single stagein co-propagating pump amplifier.L-band EDFA is more sensitive to temperature than C-band. To get a stable gain shapeover whole operating temperature, a attemperator is proposed to make the Er-doped-fiberwork in constant temperature.A variable optical attenuation is deployed to achieve L-band variable gain EDFA.Onthe basis of analyzing of noise figure of multistage configuration,3-stage opticalconfiguration is choosed as preferred option. Experiments on a3-stage opticalconfiguration that the first stage Er-doped-fiber is low concerntraion and highconcerntration respectively is done, results indicate that the noise figure deployed lowconcerntration fiber in the first stage is lower than high concerntration when they haveequivalent fiber length. Experiment on different pump methods in a2-stage amplifier isdone, the results indicate that amplifier deployed single pump has better noiseperformance than2-pump,at the same time, experiment shows that1480nm pump can passthrough the isolator with about only0.7dB insertion loss, this discover will simplify theamplifer optical configuration. On the basis of the theory design and experimentalinvestigation, a3-stage optical configuration L-band variable gain EDFA is proposed andexperimented, the performance such as better pump conversion efficiency and noise figureis achieved. Such EDFA utilizes the instrinc gain flattening of L-band amplifer andachieves gain flattening without gain flatten filter(GFF). Furthermore, the novelconfiguration simplify the optical configuration by deploying1480nm pump pass through structure, and can also save quantity of pump, which is important for reducing the cost, andwill promote the L-band EDFA.