Patent ID: 6456422
Filing Date: 2002-09-24
Classification: H04B

Abstract:
A method of optical frequency modulation discrimination, comprising the steps of:splitting an optical beam having a frequency &ohgr; into a first optical beam having a frequency &ohgr; and a second optical beam having a frequency &ohgr;; providing a first photodetector, the first photodetector providing a first current I1 responsive to the first optical beam input thereon, the first photodetector having a first photodetector spectral response and being biased such that the first current I1 is in a first direction; providing a second photodetector, the second photodetector providing a second current I2 responsive to the second optical beam input thereon, the second photodetector having a second photodetector spectral response and being biased such that the second current I2 is in the first direction; coupling an input of a transimpedance amplifier to an output of the first photodetector and to an input of the second photodetector to provide an output of the transimpedance amplifier proportional to the difference between the first current I1 and the second current I2; and providing a first optical filter to receive the first optical beam prior to incidence upon the first photodetector and a second optical filter to receive the second optical beam prior to incidence upon the second photodetector, wherein the first photodetector spectral response and the second photodetector spectral response are each broader than respective passbands of the first optical filter and the second optical filter to provide photocurrent vs. optical frequency characteristics determined by the respective first optical filter and the second optical filter.