photonic switching in fiberoptic networks如何翻译?

　　In general,photonic generation of microwave or millimeter-wave signals can be divided into three categories.In the first category,two laser beams from two different laser sources are applied to a photodetector (PD).A beat signal with a frequency equivalent to the spacing of the two wavelengths is obtained at the output of the photodetector.To generate a signal with low phase noise and high stability,the phases of the two laser sources must be locked,which are usually implemented by using op-tical injection locking [1],[2] or by an optical phase-locked loop [3],[4].For both methods,a high-quality microwave reference signal is required.For many applications,such as wireless com-munication and radar systems,the microwave generation system would be used as a local oscillator,and no reference source is available.在一般情况下,光子产生的微波或毫米波信号可以分为三类.在第一类中,从两个不同的激光源的两个激光束被施加到光电检测器（PD）.甲得到在光检测器的输出的拍频信号与当量的频率的两个波长的间距.以产生一个信号,具有低相位噪声和高稳定性,必须被锁定的相位的两个激光源,这通常是通过使用光学注入锁定[1],[2]或通过的光的相位锁定环[实施3],[4].对于这两种方法,高品质的微波参考信号是必需的.对于许多应用,如无线通信和雷达系统,微波产生系统将被用来作为一个本地振荡器,并且没有可用的参考源.