EDFA对长距离分布式光纤传感系统的附加拍频噪声研究

EDFA-Induced Additional Beat Noise in Long Distance Distributed Optical Fiber Sensing System

在基于波分复用技术的分布式光纤传感系统中,由于宽谱光源具有较大的强度噪声,光谱法测噪声系数的噪声特性评估方式不再适用.本文利用光的受激辐射与自发辐射偏振状态的差异性,提出一种双光路偏振平衡法,可以较为准确地测出分布式光纤传感系统中由掺铒光纤放大器(EDFA)引入的附加拍频噪声及该噪声对系统性能的影响.实验结果表明:输入光功率是影响系统附加噪声因子的主要因素,随着输入EDFA的光功率从10μW增大到250μW,系统的附加噪声因子随之线性增加,而泵浦电流对附加噪声因子影响较小.对于实验中所采用的EDFA及系统光源,将输入EDFA的信号功率控制在100μW以内,可使其附加噪声因子控制在0.002以下,使系统保持较好的性能.

In the long distance distributed optical fiber sensing system based on wavelength division multiplexing,intensity noise is dominant compared to quantum noise of the light source,thus traditional noise factor measurement is no longer applicable.Therefore,a double-path polarization balancing method is proposed by using the difference between the polarization state of the signal light and the spontaneous emission,which can be used to measure the additional beat noise caused by distributed optical fiber amplifiers and its influence on the long distance optical fiber sensing system.It is shown that input signal power is the main influencing factor of additional noise factor.And when the input power of the EDFA increases from 10μw to 250μW,the additional noise factor of the system increases linearly.However,it maintains at a constant value as pump current increases.Consequently,for the single-mode Erbium-doped fiber amplifier used in this experiment,if the input power of the EDFA is controlled below 100μW,a small additional noise factor less than 0.002 can be achieved,thus the long distance optical fiber sensing system can maintain good performances.