日电公司最近研制出的光通信系统.不用中继器的传输距离可达300km,这是一般光通信系统的五倍.该系统应用了超外差技术.尤为重要的是,它的振荡器能产生衍射点阵,只允许某一波长的激光束通过,不会有余光.它还能将很强的继续信号和微弱的接收信号迭加产生新的信号. The recently developed Optical Communication System by NEC Corporation has a repeater transmission distance up to 300 km, which is five times that of a general optical communication system, and employs a superheterodyne technique, and most importantly, its oscillator Can produce diffraction lattice, only allow a certain wavelength of the laser beam through, there will be no more than light, it will also be a strong continuous signal and the weak received signal superposition to generate a new signal.