S波段光纤拉曼放大器中级联受激布里渊散射串扰的实验研究

研究了光纤激光器前向抽运的S波段分布式光纤拉曼放大器中级联的受激布里渊散射(SBS)串扰现象。用窄光谱带宽(<100MHz)的可调谐激光二极管作为信号源,通过S波段分布式光纤拉曼放大器,当被放大的信号功率超过单模光纤受激布里渊散射的阈值时,出现了前向受激布里渊散射,这是传导声波布里渊散射在光纤放大器中放大的现象。随着拉曼放大器抽运功率的提高,在斯托克斯区,出现了两阶受激布里渊散射线,在实验中观测到偶数阶的受激布里渊散射谱线功率大于奇数阶的布里渊一瑞利散射线。当进一步增加拉曼放大器的抽运功率,出现了前向级联的多阶受激布里渊散射现象,拉曼放大器的增益下降,被放大的信号功率转换为受激布里渊散射,噪声变大。受激布里渊散射的串扰破坏了拉曼放大器的特性,使拉曼放大器无法在密集波分复用光纤传输系统中使用,因此需要严格地控制入纤的信号功率和放大器的抽运功率。在实验中还观测到在光纤拉曼放大器中被放大的信号光和受激布里渊散射线两侧的伴线。

Experimental Study on Cascaded Stimulated Brillouin Scattering Crosstalk in a S band Fiber Raman Amplifier

The crosstalk of cascaded stimulated Brillouin scattering (SBS) in the S band distributed fiber Raman amplifier forward pumped by the fiber laser has been studied. By S band distributed fiber Raman amplifier using narrow spectral bandwidth (<100 MHz) as signal source, the forward stimulated Brillouin scattering was observed when amplified signal power is larger than the threshold of SBS, which is the phenomena that transmitting sound wave Brillouin scattering is amplified in fiber amplifier. Second-order SBS in the Stokes region appeared with the increase of pump power, and the power of even order SBS was stronger than that of odd order Brillouin Rayleigh scattering in the experiment. The forward cascaded multiple stimulated Brillouin emerged when the pump power is increased further, and the amplified signal power is translated into SBS with stronger noise when the gain decreased. The crosstalk of SBS damaged the performance of Raman amplifier and made Raman amplifier useless in DWDM fiber transmission system, therefore the signal power and pump power entering fiber had to be controlled strictly. In the experiment, the signal and companion lines beside SBS could be observed, too.