| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical delay detection unit for an optical multi-value modulation signal for reducing the number of control circuits for controlling central wavelength to one, and for reducing the constraint of the control circuit itself by using a central wavelength monitor, and for reducing costs by simplifying an electric circuit. <P>SOLUTION: This optical delay detection circuit for differentially receiving an input optical signal is characterized to branch the input optical signal into two which are given a delay time difference by a first optical delay part having a delay time difference fine adjustment function part, and to branch the optical signals into N sets (N is two or more) which are input to a pair of photoelectric conversion elements, wherein at least two sets of optical signals among the N sets of optical signals are given different delay time differences by a second optical delay part, and interfered by an optical multiplexing/demultiplexing circuit, and input to the pair of the photoelectric conversion elements. <P>COPYRIGHT: (C)2008,JPO&INPIT |
