中文摘要：

理论分析了光纤信号传输系统中光纤端面菲涅耳反射所引起回波的多光束干涉效应,计算了光纤端面的反射回波相干叠加后回波光强随光纤端面间距的变化,针对光的振幅调制设计了基于回波干涉效应的新型光纤信号调制.实验中,从光纤耦合器输入端输入光波,将调制信号以电压形式加载于压电陶瓷管,使其伸缩振荡来控制两光纤端面间距离,光信号在光纤端面发生菲涅耳反射产生回波并发生回波干涉效应,从光纤耦合器回波端得到回波信号.实验结果表明,这种光纤信号调制器获得调制度约为95%,信噪比约为10 dB,带宽约为200 kHz.

英文摘要：

The multiple-beam interference of the echo wave which is aroused by the Fresnel reflection between two end faces of a couple of fibers is analyzed theoretically and the intensity of echo wave at the end face of fiber is calculated. A new modulator for signal in fiber is designed based on the echo interference. In the experiment, the optical signal is input to the inputend of the coupler,and the modulating voltage signal is amplified and drives the piezoelectric ceramic pipe vibrating in order to control the distance between the two fiber end faces. At the same time the light can be reflected from the two faces of the fibers and the interfered echo wave signal can be modlated. In the experiment,the device is operated for amplitude modulation,the modulation ratio can reach 95%. the S/N ratio is about 10 dB,and the bandwidth is about 200 kHz. This device is innovative,can be used easily and has low price,and can be applied as a modulator or chopper in optical signal transmission system.