Patent ID: 7546041
Filing Date: 2009-06-09
Classification: H04B,H04L

Abstract:
1. A method of transmitting a plurality n of binary digital baseband data streams, comprising: differentially pre-coding the plurality of baseband data streams to form a plurality of baseband drive signals, directly driving an optical phase modulator means with the plurality of drive signals to generate a differential M-ary (M=2 transmitting the differential M-ary phase shift key-modulated optical carrier signal from said optical phase modulator means; optically demodulating the differential M-ary phase shift key-modulated optical carrier signal using a first interferometer, free of a local oscillator, having first and second arms and first and second outputs, and using a second interferometer, free of a local oscillator, having first and second arms and first and second outputs; the first and the second interferometers each utilizing an optical delay of substantially one symbol period and imparting a relative phase shift for the optical carrier between its respective first and second arms such that there is a difference of π/2 radians between the relative phase shifts of the first and the second interferometers for the optical carrier frequency; performing balanced detection using a first balanced optical detector at the outputs of the first interferometer; and performing balanced detection using a second balanced optical detector at the outputs of the second interferometer.