| 摘要 |
PURPOSE:To increase the range of the length of transmission line in which the optical transmission is made possible without using any control line, by noticing that an optical transmission line has the same length and same characteristics between its ascending and descending lines and then varying the output level of the transmitting part in response to the fluctuation of the input level at the receiving part. CONSTITUTION:The ascending and descending optical transmission lines 15-1 and 15-2 have the same length and same characteristics. The transmitting and receiving parts 13-1 and 14-2 plus the transmitting and receiving parts 13-2 and 14-1 belong to the same system of the same station. In this case, the transmitting circuit control signals of the parts 14-1 and 14-2 are fed to the parts 13-2 and 13-1 of the same system in the same station against a change of an optical input level. Thus the optical output level is changed at the parts 13-2 and 13-1. As a result, it is enough to control the optical output level at the transmitting part of the same system in the same station without controlling the transmitting part of the remote side at the receiving part by means of a control line of the system. |
