Research On Gain Control Characteristics Of C+L Band Erbium-doped Fiber Amplifier In Linear Cavity

Erbium doped fiber amplifier(EDFA) is the core component in wavelength division multiplexing optical communication system. It is required to enhance the transmission quality and ensure the flatness output of the gain spectrum and the stable output of the signal. However, due to network data will affect the amplifier gain stability when the input power and channel number changed. In order to stabilize gain, AOGC(All Optical Gain Clamping) have received much attention. But the penalty is to surely generate a clear loss at the lasing-wavelength, which may lead the unexpected flatness-worsening. The contradiction between gain clamping and gain flatness limit the application of high performance fiber amplifier. Therefore, to balance relations between gain flatness and stable has important research significance for realizing amplified signals simultaneous flattening and clamping.The linear cavity all-optical gain clamped as the theoretical basis, in C and L band signal gain spectrum as the research object, through optimizing the parameter such as fiber Bragg grating center wavelength and reflectivity, in order to achieve the synchronization gain control of EDFA, the main work is as follows:1. C band EDFA as the research object, then through simply selecting the central wavelength reflectivity and bandwidth of single-FBG, test the gain clamping characteristics of linear cavity structure, find out the relationship between them and the linear cavity gain clamping effect. We studied the gain flattening of a fiber Bragg grating(FBG) with low reflectivity and gain flat filter, EDFA un-flatness(±0.6dB) in the range of 1530-1558 nm can be obtained;2. The use of single / dual Bragg grating structure, synchronous control gain for L band EDFA. The two structures have their own characteristics, and the output gain of the single grating structure is high, 22.3dB average gain and ±0.83 dB flatness in the range of 1570-1610 nm can be obtained together by our scheme. In addition, the ±0.1dB stability of multi-wavelength signals is also guaranteed within-40 dBm to-15 dBm dynamic range. Compared with single grating, the output gain of the dual grating structure is slightly smaller than the single grating, the average gain is 20 dB, but its stability is better, the signal input power in the range of-40 dBm to-10 dBm, the gain fluctuation within+0.1dB. But the more flat gain spectrum, gain flatness +0.77 dB.3. A combined broadband EDFA is proposed, and the gain flatness of C+L band signal is gained by using this structure. The experimental results obtained its 3dB bandwidth reaches 70 nm, the signal gain reaches above 20 dB.