| 摘要 |
PCT No. PCT/GB90/01416 Sec. 371 Date Apr. 20, 1992 Sec. 102(e) Date Apr. 20, 1992 PCT Filed Sep. 13, 1990 PCT Pub. No. WO91/04617 PCT Pub. Date Apr. 4, 1991.An optical detector for use in detecting digital optical signals has an optical fiber coupler which splits a received optical signal into two signal portions. The coupler has unequal length output fibers so that one signal portion impinges upon an associated photodetector delayed relative to the other. The photodetectors are connected in series nonopposed when the delay is equal to the bit period of the optical signal the output of the detector is the differential code (dicode) of the received signal which can be recovered by a high input impedance, i.e. integrating, amplifier. By forming the dicode in the optical domain in this manner large DC and AC dynamic ranges are obtained without linearity constraints on the optical transmission source that apply when the optical signal is transmitted as a dicode.
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