| 摘要 |
PURPOSE:To obtain an optical coherent equipment with a simple configuration by dividing a short optical pulse train into laser beams whose optical frequencies differ from each other, adopting one of them for a reference light, and using at least one beam other than the reference light and modulating it into a signal light, sending them simultaneously to an optical transmission line and allowing a receiver to use the received reference light as a local oscillation light and to detect the signal light. CONSTITUTION:A short optical pulse outputted from a semiconductor mode synchronization laser 11 is branched by a branching filter 12, from which laser beams with optical frequencies of f1-fm are obtained. For example, let a repetition period of the mode synchronization laser 11 be 2GHz, the frequency interval of the optical frequencies f1-fm becomes 2GHz. The optical frequency f1 among the laser beams with the optical frequencies of f1-fm is defined as a reference light and the other laser beams are modulated respectively by an optical modulator 14 to obtain signal lights. The receiver inputs the received lights to a photodetector 31 in a lump. In this case, the reference light not modulated works as a local oscillation light. Thus, the photodetector 34 observes (m-1) kinds of signals whose pitch is 2GHz. |
