Reserach On The Amplification Of Weak Optical Signal Based On Stimulated Brillouin Scattering In Optical Fiber

Detecting weak signals is always difficult in LIDAR, laser communications and other fields. Amplification of weak optical signal, is an effective means to improve system operating range and sensitivity. Among various optical amplification technology, one which is based on Stimulated Brillouin Scattering(SBS) and operated in optical fiber, with high gain, frequency selectivity and high system reliability advantages, has important application value in the field of optical amplification.The effect of Brillouin amplification parameter on signal amplification factor(SAF) and signal to noise ratio(SNR) is studied in this article, including the pumping power, signal pulse width, fiber length, etc. In order to achieve high gain, high SNR of weak signal amplification, parameters are optimized.First, the Brillouin amplification model including noise, which is used to stimulate the SBS process, is derived theoretically. The variation of SAF and SNR under different situation is studied, by changing pumping power, signal pulse width, fiber length etc. separately. The results show that SAF increases gradually with pumping power and signal pulse width, while declines with signal power; SNR declines along with pumping power, while increases with signal pulse width and power.Experimentally, the non-scattering signal Brillouin amplification is carried out first. Using continuous laser as pump and pulse gauss as signal, by changing pumping, signal parameters in different fiber, the effect of those parameters on SAF and SNR during the SBS process is obtained. In experiment, the SAF of 0.43μW signal achieves 107, with SNR 11 dB. Comparing the results with theoretical simulations, found the variation of SAF and SNR is corresponding, and determined using a fine core optical fiber under weak pumping power, a normal single-mode fiber under strong pumping power. Then the scattering Brillouin amplification is carried out and the effect of pumping power, signal pulse width and power, fiber length etc. on Brillouin amplification is obtained. By optimizing parameters, the SAF of 0.43μW achieves 106 with SNR 10 dB, achieving high gain, high SNR for weak optical signal. Finally, comparing the results with non-scattering’s, found that SAF and SNR both decreased, indicating depolarization did have impact on the SBS process in optical fiber.