Optical frequency discriminators based on fiber Bragg gratings

An optical receiver having an optical frequency discriminator, the optical frequency discriminator comprising:

• a polarization controller configured to receive an incoming optical signal and to polarize the optical signal such that optical power is allocated into a first polarization mode and a second polarization mode;
• a polarization-maintaining (PM) coupler configured to receive the polarized signal and transmit the polarized signal;
• a polarization-maintaining fiber Bragg grating (PM-FBG) configured to receive the polarized signal transmitted by the PM coupler and to reflect at least a portion of the polarized signal thereby providing a reflected optical signal, the PM-FBG having reflectivities for the first polarization mode and the second polarization mode that are based on a frequency of the incoming signal;
• a beam splitter configured to receive the reflected optical signal and to split the first polarization mode from the second polarization mode in the reflected optical signal, thereby providing a first signal defined by a portion of the optical power in the first polarization mode and a second signal defined by a portion of the optical power in the second polarization mode;
• and
• first circuitry configured to compare the first signal and the second signal to provide a third signal having an amplitude that varies linearly with a frequency of the incoming optical signal received by the polarization controller.