Patent ID: 8385746

Claim:
An optical interface device for converting a first optical signal that is received from a first optical transmission line to a second optical signal that can be transmitted through a second optical transmission line which is different from the first optical transmission line, the optical interface device comprising: an optical receiver configured to receive the first optical signal, and configured to recover a first data signal and a first clock signal corresponding to the first optical signal; a clock generator configured to generate a second clock signal corresponding to the second optical signal; a frequency difference detector configured to detect a frequency difference between the first clock signal and the second clock signal, and configured to generate information regarding a stuff amount for a stuffing process to be applied to the first data signal for compensating for the difference; a stuffing circuit configured to subject the first data signal to a stuffing process based on the information generated by the frequency difference detector according to timing of the second clock signal; a determination circuit configured to determine whether a frequency deviation of the first clock signal is abnormal based on the information generated by the frequency difference detector; an alarm generator configured to receive a data signal from the stuffing circuit, and configured to generate an alarm indication signal indicating that the frequency deviation is abnormal to another component that is disposed downstream therefrom through the second optical transmission line when the determination circuit determines abnormal frequency deviation, to thereby insert the alarm indication signal in a predetermined region of the data signal; a converter configured to convert the data signal passed through the alarm generator to a second data signal having a frame structure that is compatible with the second optical signal; and an optical transmitter configured to modulate light according to the second data signal, to thereby generate the second optical signal.