Penalty free biphase linecoding for pattern independent FSK coherent transmission systems

Abstract

Biphase coding is used as a method to eliminate the unwanted influence of nonuniform laser characteristics in 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-Mbit/s 280-Mbaud transmission experiment. The receiver features a new type of reliable unambiguous clock extraction. Due to 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 0 P of -56.7 dBm for 2'' -1 pseudorandom patterns, only 4.8 dB from the shot-noise limit.

Frequency Spectra in an Optical CPFSK Heterodyne Delay Demodulating Receiver using Manchester Coding

“…To eliminate distortion effects during long sequences of zero or one signals, biphase Manchester coding is often used [5]. Moreover, with this coding technique the data clock signal can be recovered very easily.…”