Based on the application requirements of light source in fiber Bragg grating(FBG) sensing system a two-stage double-pass and erbium-doped amplified spontaneous emission(ASE) fiber source is designed.The structure of source,way of output,length of erbium-doped fiber and pump power are optimized.The results show that under the optimal condition,the ASE output with central wavelength at 1 564.5 nm,output power of 35.8 mW and 85 nm bandwidth in C+L band spectrum is achieved.Its flatness from 1 525 n...