A PSK modem for suppressed carrier coherent fiber optic transmission using decision driven demodulation

In this paper we present an extension of the Costas loop type demodulator which regenerates the suppressed carrier and detects the data using a configuration known as “decision-driven” demodulator with applications in coherent fiber optic communications with phase shift keying PSK modulation. When using this kind of loops, the problem of joint carrier and bit synchronization is to be solved. We first describe the modulation system used to generate the PSK signal that is transmitted. We next present the development of the biphase demodulator based on modified Costas loop in a “data aided” configuration. We present the design criteria and experimental development of the joint carrier and bit synchronization subsystem. Finally, we describe the complete experimental implementation of the decision-driven BPSK demodulator and present preliminary measurements