Interferometer configured for signal processing in an interference path

Abstract

An interferometer is provided that includes a first path and a second path. The first path is configured to propagate an electro-magnetic signal at a first wavelength. The second path is configured to convert a portion of the electro-magnetic signal from the first wavelength to a second wavelength for processing and is configured to convert the portion of the electro-magnetic signal from the second wavelength back to the first wavelength for interference with the electro-magnetic signal of the first path. The first wavelength may be an optical wavelength or any other suitable wavelength of the electro-magnetic spectrum. The second wavelength, which is different than the first wavelength, also may be any suitable wavelength of the electro-magnetic spectrum.

What is claimed is: 
     
         1 . An interferometer, comprising:
 a first path configured to propagate an electro-magnetic signal at a first wavelength; and   an interference path configured to convert a portion of the electro-magnetic signal from the first wavelength to a second wavelength, to convert the portion of the electro-magnetic signal from the second wavelength back to the first wavelength, to interfere the electro-magnetic signal of the first path with the portion of the electro-magnetic signal converted back to the first wavelength, and to modulate a pilot signal onto a signal generated within the interference path.   
     
     
         2 . The interferometer of  claim 1 , wherein the second wavelength is at baseband. 
     
     
         3 . The interferometer of  claim 1 , wherein the interference path comprises an optoelectronic path. 
     
     
         4 . The interferometer of  claim 3 , wherein the optoelectronic path comprises a fixed laser or a tunable laser. 
     
     
         5 . The interferometer of  claim 3 , wherein the optoelectronic path comprises at least one of an analog portion and a digital portion. 
     
     
         6 . The interferometer of  claim 3 , wherein the optoelectronic path comprises:
 an optical-to-electrical conversion element configured to receive the optical signal at the first wavelength and convert the optical signal at the first wavelength to an electronic input signal;   an electronic processing element configured to receive the electronic input signal and process the electronic input signal to form thereby an electronic output signal indicating removal of the optical signal at the first wavelength; and   an electrical-to-optical conversion element configured to receive the electronic output signal and convert the electronic into an optical output signal for coupling with the optical signal propagating via the optical path to remove, via destructive interference, the optical signal at the first wavelength.   
     
     
         7 . The interferometer of  claim 3 , wherein the optoelectronic path comprises a subcarrier modulation function. 
     
     
         8 . The interferometer of  claim 3 , wherein at least one path of the interferometer comprises a delay element. 
     
     
         9 . The interferometer of  claim 8 , wherein the delay element is configured to be tuned for providing substantially equal delays in the first path and the optoelectronic path. 
     
     
         10 . The interferometer of  claim 8 , wherein the delay element is configured to be tuned based on a control signal received from a control detector responsive to detection of the pilot signal by the control detector. 
     
     
         11 . The interferometer of  claim 3 , wherein at least one path of the interferometer comprises a phase adjustment element. 
     
     
         12 . The interferometer of  claim 11 , wherein the phase adjustment element is disposed in the first path or in the optoelectronic path. 
     
     
         13 . The interferometer of  claim 11 , wherein the phase adjustment element is configured to be tuned to provide an interference property at an output coupler of the interferometer. 
     
     
         14 . The interferometer of  claim 1 , wherein the pilot signal comprises a pilot subcarrier in an Orthogonal Frequency-Divisional Multiplexed (OFDM) signal or a temporal pilot symbol. 
     
     
         15 . The interferometer of  claim 1 , further comprising:
 a control detector configured to control an element of the interferometer based on the pilot signal.   
     
     
         16 . The interferometer of  claim 15 , wherein the control detector is configured to control the element of the interferometer to drive an error signal toward zero. 
     
     
         17 . The interferometer of  claim 15 , wherein the element of the interferometer comprises at least one of a delay element or a phase adjustment element. 
     
     
         18 . The interferometer of  claim 15 , wherein the control detector is configured to detect an output signal and to feed the detected output signal to an electronic processing module of the interference path for comparison with an expected output signal. 
     
     
         19 . An apparatus, comprising:
 an interferometer comprising:
 a first path configured to propagate an electro-magnetic signal at a first wavelength; and 
 an interference path configured to convert a portion of the electro-magnetic signal from the first wavelength to a second wavelength, to convert the portion of the electro-magnetic signal from the second wavelength back to the first wavelength, to interfere the electro-magnetic signal of the first path with the portion of the electro-magnetic signal converted back to the first wavelength, and to modulate a pilot signal onto a signal generated within the interference path. 
   
     
     
         20 . An optical transmission system, comprising:
 an interferometer comprising:
 a first path configured to propagate an electro-magnetic signal at a first wavelength; and 
 an interference path configured to convert a portion of the electro-magnetic signal from the first wavelength to a second wavelength, to convert the portion of the electro-magnetic signal from the second wavelength back to the first wavelength, to interfere the electro-magnetic signal of the first path with the portion of the electro-magnetic signal converted back to the first wavelength, and to modulate a pilot signal onto a signal generated within the interference path.