Study On Erbium-doped Fiber Superfluorescence Source And The Gain Flattening Technique

The super-fluorescent fiber source (SFS) and the gain flattening technique are studied in this paper. The high flattening fiber soure produced can be applied in the distributed FBG sensing system, the long optical fiber communication systems, fiber optic gyroscope, and so on. The studies of the paper are useful for the design of the high flattening erbium-doped super-fluorescent fiber source.First, the article gives a detailed introduction about the erbium-doped fiber, the pumping source as well as the main optoelectronic devices, which compose the SFS. Then, systematically describes parameters,fundamental structures and mathematical model about erbium-doped fiber super-fluorescent source. Based on the studies of the C band and L band ASE, the C+L band ASE is lucubrated. By studying the C+L band ASE of single-stage single-pass, single-stage double-pass and dual-stage double-pass structure, a high flatness C+L band ASE is presented using the three-stage erbium fiber and two pump LDs of 980 nm structure. The flatness of the spectra from 1543nm to 1603nm is less than±1.3dB without using any external spectral filters. But the the flatness of the spectra from 1523nm to 1603nm is more than±3dB, because there is a peak near by 1532nm.The typical spectra of erbium-doped fiber source is not a flat spectra containing a high-intensity region and a flat part spectra. In order to make the spectra flat, some gain flatten techniques are introduced. Thereinto, research focus is the gain flatten filter. The filter studies include cascaded Mach-Zehnder Interferometer (MZI) based gain flattening filter, long period fiber gratings (LPFG) and fiber loop mirror. Analyse their working principles theoretically, test their effects by the experiments, and contrast their characteristics. Based on the spectra of designed fiber source, the transmission spectrua of the LPFG can be computed. By utilizing the LPFG built according to the computing result, the flatness of the spectra from 1525nm to 1605nm is less than±0.66dB, the output power is 1.05 dB samller than before. So it is better than others.According to the project of our laboratory, the performance of fiber source used in distributed FBG sensing system is analysed. The optimized C+L band ASE is applied in the distributed FBG sensing system, experiment results indicate that the high flatness ASE not only extends the bandwidth for large number of sensor, but also is beneficial to accurate demodulation.Finally, the shortages of the study are listed, which definitize the targets and the problems to be solved in the future study.