The filtering demodulation is realized by using the good linear sideband near 1530 nm of the super-fluorescent fiber source.The light source of system adopts double-pass backward configuration,because the detecting sensitivity of light source decides the whole system′s sensitivity.When the linear sideband is 2.5 nm,the sensitivity of power is -14.7 μW/nm,and the degree of fitting is 0.9995.The system uses all-optical structure to improve the demodulation speed.By the way of computer simulation,its detection sensitivity for the wavelength and strain separately are -1.27 pm/mV and 1.06 με.The results show that this demodulation system has high sensitivity,good stability,quick demodulation speed,and it can realize real-time detection of seismic wave.