Optical 8-DPSK and receiver with direct detection and multilevel electrical signals

Abstract

This paper presents a differential 8-level phase-shift keying (8-DPSK) modulation format with a simple new receiver for transmission of 3 bit/symbol. The receiver with direct detection is based on a differential quadrature phase-shift keying (DQPSK) receiver with binary decision devices and a combinational network for estimating the transmitted bit sequences from the detected multilevel electrical signals. The 8-DPSK transmitter is based on a differential quadrature phase-shift keying (DQPSK) transmitter with an additional phase modulator. Spectral properties of 8-DPSK and chromatic dispersion tolerance are investigated.