考虑损耗时拉曼放大泵浦光的偏振效应

利用高非线性和较大吸收损耗的光子晶体光纤制作光纤拉曼放大器，是当前的一种趋势，这导致泵浦光非线性旋转效应明显增强．本文在考虑吸收损耗条件下，研究了泵浦光的非线性旋转问题，首次得出了连续光条件下的解析解．结果表明，输入线偏振光与圆偏振光都不会产生非线性旋转，只有椭圆偏振光才有非线性旋转．旋转是绕着邦加球的纬线进行，s3保持不变．随着吸收损耗的增加，有效长度变小，相对的旋转速度变慢．这表明，如果光纤对于泵浦光的吸收越强，越有利于拉曼放大．

Polarization Rotation of Pump Light in Raman Fiber Amplifier with Attenuation

The production of Raman fiber amplifier by using the photonic crystal fiber with high nonlinearity and the bigger absorption attenuation is a new trend, leading to the remarkably enhanced nonlinear polarization rotation of pump beam. In this paper, considering the absorption attenuation, the nonlinear polarization rotation of pumping light is investigated, and, for the first time, an analytical solution is obtained under continuous light conditions. The results showed that input linearly polarized and circularly polarized light will not produce nonlinear polarization rotation, and only the elliptically polarized light will produce nonlinear polarization rotation. Rotation is parallel to the latitude in the Poincare Sphere, and the s3 remains unchanged. With the absorption attenuation increases, the effective length will be smaller, the relatively rotation speed will be slower. This suggests that if the absorption for pump light in optical fiber is stronger, the more is conducive to Raman amplification.