| 摘要 |
<P>PROBLEM TO BE SOLVED: To detect input-off of differential M phase-shift modulated signal light even if the input power of color light is large. <P>SOLUTION: A demodulating part (105, 106 and 107) performs the delay interference of received differential M phase-shift modulated signal light to demodulate it. A phase error detecting part 110 detects an error of a control phase amount of the delay interference by the demodulating part (105, 106 and 107). A control part 111 adjusts the control phase amount of the delay interference by the demodulating part (105, 106 and 107) to a prescribed phase amount on the basis of the error detected by the phase error detecting part 110. A data processing part 109 monitors the error state of a data signal demodulated by the demodulating part (105, 106 and 107). The control part 111 changes the control phase amount from the prescribed phase amount when the error state is a prescribed error state, and determines the received state of the differential M phase-shift modulated signal light on the basis of an error detected later by the phase error detecting part 110. <P>COPYRIGHT: (C)2008,JPO&INPIT |
