Patent ID: 6941076
Filing Date: 2005-09-06
Classification: H04B

Abstract:
1. A method of auxiliary data communication between terminals in a free-space optical communication system, the method comprising: generating an auxiliary data signal; multiplying the auxiliary data signal with a carrier tone to produce a modulated carrier signal; generating a primary data signal; multiplying the primary data signal with the modulated carrier signal to produce a product signal, wherein the product signal is added to an integer multiple of the primary data signal to generate a data communication signal having the modulated carrier signal superimposed thereon; transmitting the data communication signal as an optical signal from a first free-space optical terminal to a second free-space optical terminal; receiving the data communication signal at the second free-space optical terminal via an optical element; splitting the data communication signal into a first optical signal and a second optical signal; detecting the first optical signal via a high speed detector and processing the first optical signal to retrieve the primary data signal; detecting the second optical signal via a detector having a plurality of cells, the detector generating electrical outputs corresponding to the plurality of cells; summing the electrical outputs from the detector to produce an output signal; multiplying the output signal with a reference signal to produce a referenced signal; filtering the referenced signal to produce an output signal comprising the auxiliary data signal and the primary data signal; sampling the output signal to regenerate the auxiliary data signal; and passing each of the electrical outputs from the detector through a low-pass filter to generate a cell signal, wherein the cell signal corresponds to an amount of the second optical signal incident upon a corresponding cell of the detector.