| 摘要 |
PROBLEM TO BE SOLVED: To prevent the deterioration of the waveform of a transmission clock signal when a receive clock is returned and changed into a transmission clock in the case of a loop test in a transmission device or the like. SOLUTION: The clock switching device is composed of a light receiving section 1 receiving a light signal from a transmission line and converting it into an electric signal, an electric-signal interface section 9 receiving the receive clock signal and outputting a clock signal required in the device, a phase synchronous circuit 10 generating the required clock signal in the device and a light transmission section 3 receiving the electric signal and converting it into the light signal and outputting the light signal. A receive-clock extracting section 4 generating the clock signal is installed to the light receiving section 1, the first receiving buffer 5, the first transmission buffer 7, a frequency demultiplier 11, the second transmission buffer 12 and the second receiving buffer 13 are mounted on the electric interface section 2, and a selector 14, a phase comparator 15, a control filter 16, a VCXO 17 and the frequency demultiplier 18 are secured to the phase synchronous circuit 10. |
