| 摘要 |
<P>PROBLEM TO BE SOLVED: To achieve high start-up speed of a receiver and high reliability in operation by preventing two receivers from converging on a state of receiving the same polarization state. <P>SOLUTION: A polarization multiplexed transmitter 200 previously applies frequency shifts of frequencies +Δf and -Δf to digital information signals 205-1, 205-2 of X polarization and Y polarization to be transmitted, and modulates and polarization-multiplexes the digital information signals by optical electric field modulators 102-1, 102-2. As a result, a frequency difference of 2Δf is applied to X polarization and Y polarization components. A polarization diversity digital coherent receiver 215 receives the signal. A frequency estimation section in a signal processing circuit 214 detects a frequency difference signal in both polarization components. This signal is used to control a polarization separation section in the signal processing circuit 214. <P>COPYRIGHT: (C)2012,JPO&INPIT |
