Patent ID: 6704375
Filing Date: 2004-03-09
Classification: H04B,H04L

Abstract:
A device for the homodyne reception of optically phase-keyed signals of preselected frequency comprising:a first heterodyne receiver having an input for receiving the optically phase-keyed signal of the preselected frequency and an output; a first data discriminator having an in-phase channel for receiving the optically phase-keyed signal of the preselected frequency and having an a data signal output; a frequency acquisition circuit for tuning to the preselected frequency of the optically phase-keyed signal at the output of the dated discriminator; a local oscillator laser for generating an optical signal at the preselected frequency having a phase matched to the optically phase-keyed signal received at the first heterodyne receiver; a feedback unit for an optical phase-locked loop having multiple inputs and an output, at least one of said feedback unit inputs connected with the output of said first data discriminator; a window discriminator having two or more thresholds inserted between the output of said first heterodyne receiver and another input of said feedback unit; a reversing switch for supplying a control input of said local oscillator laser with an output signal selected from at least one of a group consisting of an output signal of said feedback unit or an output signal of said frequency acquisitions circuit; a filter circuit connected with said reversing switch; a second heterodyne receiver having an input from the first heterodyne receiver, an input from the local oscillator laser and an output; a second data discriminator for a quadrature channel having a data signal output and an output wherein the output of said second data discriminator is connected to an input of said feedback unit; and, a first optical beam splitter connected to receive the optically phase keyed signal of preselected frequency with output to the first heterodyne receiver and an output to the second heterodyne receiver; a second optical beam splitter connected to receive an input from the local oscillator laser and with output to the first heterodyne receiver and the second heterodyne receiver; whereby a phase keyed comparison can occur between the data signal output of the first data discriminator and the data signal output of the second data discriminator for decoding the optically phase keyed signal at the selected frequency.