本文重点讨论了用长、短波长的发光管作光源时系统的带宽问题以及它对中继距离的影响。虽然此时的带宽与用激光器作光源的系统相比要窄很多,但采取一定的措施,可以得到适当弥补。另一方面,它对光纤带宽的要求却降低了,加之发光管有造价低、寿命长、使用维护方便等优点,因此在一般市话中继通信系统中使用发光管作光源还是有其广阔前景的。 This article focuses on the use of long and short wavelength LED light source system bandwidth and its impact on the relay distance. Although the bandwidth at this time is much narrower than the system using a laser as a light source, certain measures can be taken to make up for it. On the other hand, its requirements on the optical fiber bandwidth are reduced. In addition, the LED has the advantages of low cost, long service life, convenient use and maintenance, etc. Therefore, it is still very promising to use a LED as a light source in a general public telephone relay system .