| 摘要 |
PURPOSE:To easily monitor the normal operation of an optical transmitter by using a directional optical coupling switch capable of obtaining in-phase and opposite phase optical modulation outputs as an external modulator and converting the opposite phase output into an electric signal. CONSTITUTION:A DC power source 1 drives a laser diode 2 and its optical output is coupled optically with an optical directivity coupling switch 4. The optical output is subjected to intensity modulation via a driver circuit 3 with a transmission signal inputted from a transmission signal terminal 10, subject to intensity modulation and sent to an optical fiber 5. The switch 4 has two output terminals, through which opposite phase optical modulation signals are obtained. A photodiode 6 is coupled optically with the terminal in the opposite phase relation to the output terminal coupled with the optical fiber 5 and the optical reception signal is converted into a logic signal by an optical reception circuit 7 and the discordance is detected with the transmission signal at an E-OR circuit 8. The output of the circuit 8 is sampled with the transmission clock at a FF 9, the result is sent to a monitoring output terminal 12 and the signal is monitored without the degradation of performance. |
