| 摘要 |
PURPOSE:To realize a high optical reception sensitivity with low noise at the reception side by using an image rejection mixer. CONSTITUTION:In the process of obtaining a demodulation signal from a received signal light, the polarized state of the signal light and the local oscillation light is adjusted and they are made coincident after the adjustment, the synthesized light is separated into two orthogonal linearly polarized light components, which are subject to optical heterodyne detection respectively, two intermediate frequency signals having a phase difference of 90 deg. obtained by the light heterodyne detection are coupled and the combined intermediate frequency signal is divided into two signals based on the frequency arrangement of the signal light and the local oscillation light. As a means to realize the method, an image rejection mixer 19 is used. Thus, a semiconductor laser is used for the light source at the sender side in the frequency shift keying (FSK) optical heterodyne detection optical communication system and even when the frequency shift is selected large at FSK modulation, the band required for the reception side is suppressed lower. |
