| 摘要 |
PURPOSE:To execute a loop back test at an optical signal level. CONSTITUTION:A transmitted optical signal is monitored by a first light receiving element 13 and impressed to a selector 14 as a monitor signal. On the other hand, a received optical signal received by a second light receiving element 15 is impressed to the selector 14 as a received electric signal. When a loop back signal expressing the start of the loop back test is impressed from a loop back signal output part 17 to the selector 14, the selector 14 outputs the monitor signal as a select signal. This select signal is amplified by an amplifier circuit 16. Thus, since the monitor signal is selected by the selector 14 in the case of the loop back test, the loop back test can be executed at the transmitted optical signal level while including the optical output function of a light transmitting element 12 as well. |
