| 摘要 |
PCT No. PCT/GB93/01353 Sec. 371 Date Jan. 17, 1995 Sec. 102(e) Date Jan. 17, 1995 PCT Filed Jun. 29, 1993 PCT Pub. No. WO94/00928 PCT Pub. Date Jan. 6, 1994An optical source for a communications system includes an optical signal source whose output is modulated to contain sidebands. The sidebands interact to produce beat frequencies and modifying apparatus, such as a length of dispersive optical fibre, is used to modify characteristics of the sidebands so that the beat frequency can be detected at a receiver such as a photodetector. In this way, high frequency signals can be generated and photodetected, the output of the receiver being suitable to drive a microwave antenna, thus providing an optically fed microwave communications link. Using a video signal generator a video signal can be superimposed on the received beat frequency and therefore carried by the microwave link.
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