Penalty free biphase linecoding for pattern independent FSK coherent transmission systems

Biphase coding is used to eliminate the unwanted influence of nonuniform laser characteristics in frequency-shift-keying (FSK) transmission systems. Compared to other (ternary) linecoding schemes, biphase has the advantage that it does not give a 3-dB sensitivity penalty when properly decoded in the receiver. This has been demonstrated in a 140-Mb/s 280-Mbaud transmission experiment. The receiver features a new type of reliable unambiguous clock extraction. Due to the compact IF spectrum, as compared with ternary linecoding schemes, biphase equipped FSK systems are especially suited for efficiently spaced coherent multichannel (CMC) systems. FSK heterodyne transmission experiments show a sensitivity eta P of -56.7 dBm for 2/sup 10/-1 pseudorandom patterns, only 4.8 dB from the shot-noise limit.<
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