Apparatus and method for controlling polarization of an optical signal

Abstract

A polarization controller includes a first polarization beam splitter operable to receive an input optical signal having an input state of polarization and to separate the signal into a first and a second principal mode of polarization. The polarization controller further includes at least three stages of phase shifters each operable to introduce a phase shift between the first and second principal modes, at least one phase shifter comprising a beam splitter that is shared with at least one other of the phase shifters. The at least three stages of phase shifters include a first stage coupled to the first polarization beam splitter and a last stage coupled to a second polarization beam splitter. The second polarization beam splitter is operable to receive phase shifted copies of the first and second principal modes, and to align the phase shifted copies of the principal modes to an output state of polarization.

1 . An optical processing system, comprising: 
 one or more polarization converters operable to receive an optical signal and to manipulate at least a portion of an input state of polarization of the optical signal;    a first beam splitter operable to divide the optical signal into at least a first part and a second part, the first part of the optical signal having at least a first principal mode of polarization;    an optical signal separator operable to receive at least the first part of the optical signal and to communicate at least a portion of the first part to a polarization adjustment system for processing, the polarization adjustment system comprising: 
 a first polarization beam splitter operable to receive the at least the portion of the first part of the optical signal and to separate the at least the portion of the first part of the optical signal into at least the first principal mode of polarization; and  
 at least three stages of polarization adjusters each operable to introduce a polarization rotation to at least the first principal mode of polarization, at least one polarization adjuster comprising a second beam splitter that is shared with at least one other of the polarization adjusters, the at least three stages of polarization adjusters comprising a first stage coupled to the first polarization beam splitter and a second stage coupled to a second polarization beam splitter, wherein the second beam splitter that is shared comprises a partially transmitting mirror and wherein the polarization adjusters operate at least in part by reflecting light from a reflective surface;  
   a combiner operable to combine one or more polarization adjusted portions of the first part of the optical signal into a polarization adjusted output signal; and    an optical reflector operable to receive at least some of the polarization adjusted optical signal and to communicate the polarization adjusted optical signal to an output.    
   
   
       2 . The optical processing system of  claim 1 , further comprising a light guide operable to communicate at least a portion of the optical signal for processing, the optical signal comprising a plurality of wavelengths  
   
   
       3 . The optical processing system of  claim 2 , wherein the light guide is a light pipe.  
   
   
       4 . The optical processing system of  claim 1 , wherein the first and second beam splitters are selected from the group consisting of a substrate having one or more layers of dielectric coating, a partially silvered mirror, and a fiber coupler.  
   
   
       5 . The optical processing system of  claim 1 , wherein the polarization converter is operable to manipulate the at least the portion of the input state of polarization of the optical signal to an orthogonal mode of polarization.  
   
   
       6 . The optical processing system of  claim 1 , wherein the polarization converter is selected from the group consisting of wave plates, transverse electrical transverse magnetic converters, Faraday converters, polarization beam splitters, and mirrors.  
   
   
       7 . The optical processing system of  claim 1 , wherein the optical signal separator is a beam splitter with one or more dielectric layers.  
   
   
       8 . The optical processing system of  claim 1 , wherein at least one of the polarization adjusters is formed on a semiconductor substrate.  
   
   
       9 . The optical processing system of  claim 8 , wherein the semiconductor substrate is selected from the group consisting of silicon and polysilicon.  
   
   
       10 . The optical processing system of  claim 1 , wherein at least one polarization adjuster changes state based on a voltage applied to the polarization adjuster.  
   
   
       11 . The optical processing system of  claim 1 , wherein at least some of the polarization adjusters operate in parallel on different portions of the first part of the optical signal received from the optical signal separator.  
   
   
       12 . The optical processing system of  claim 1 , wherein the optical reflector comprises one or more mirrors.  
   
   
       13 . The optical processing system of  claim 1 , wherein the optical reflector operates to change the direction of the polarization adjusted output signal to the output.  
   
   
       14 . A method of processing multiple wavelengths of light, the method comprising: 
 manipulating at least a portion of an input state of polarization of an optical signal;    dividing the optical signal into at least a first part and a second part, the first part of the optical signal having at least a first principal mode of polarization;    separating the first part of the optical signal into at least a first portion of optical signal wavelengths and a second portion optical signal wavelengths;    receiving at least the first portion of optical signal wavelengths at a polarization adjustment system;    using the polarization adjustment system, controlling a state of polarization of at least the first portion the optical signal wavelengths, wherein controlling the state of polarization of the first portion of the optical signal wavelengths comprises: 
 separating the first portion the optical signal wavelengths into at least the first principal mode of polarization; and  
 introducing at least three stages of polarization rotation to at least the first principal mode of polarization, wherein at least one polarization rotation stage shares a beam splitter with at least one other polarization rotation stage, wherein the beam splitter that is shared comprises a partially transmitting mirror, and wherein at least one stage of the polarization rotation at least partially operates by reflecting light from a reflective surface;  
   combining one or more polarization rotation portions of the first portion the optical signal wavelengths into a polarization adjusted output signal; and    reflecting the polarization adjusted optical signal to an output.    
   
   
       15 . The method of  claim 14 , wherein the beam splitter that is shared is operable to pass a first copy of the first portion of the optical signal wavelengths in a first direction and a second copy of the first portion of the optical signal wavelengths in a second direction.  
   
   
       16 . The method of  claim 14 , further comprising communicating at least the optical signal for processing, the optical signal comprising a plurality of wavelengths;  
   
   
       17 . The method of  claim 14 , wherein the polarization adjustment system changes state based on one or more voltages applied to the polarization adjustment system.  
   
   
       18 . A method of processing multiple wavelengths of light, the method comprising: 
 manipulating at least a portion of an input state of polarization of an optical signal using a polarization converter;    dividing the optical signal into at least a first part and a second part, the first part of the optical signal having at least a first principal mode of polarization;    separating the first part of the optical signal into at least a first portion of optical signal wavelengths and a second portion optical signal wavelengths;    receiving at least the first portion of optical signal wavelengths at a polarization adjustment system;    using the polarization adjustment system, controlling a state of polarization of at least the first portion the optical signal wavelengths, wherein controlling the state of polarization of the first portion of the optical signal wavelengths comprises: 
 separating the first portion the optical signal wavelengths into at least the first principal mode of polarization; and  
 introducing at least two stages of polarization rotation to at least the first principal mode of polarization, wherein at least one polarization rotation stage shares a beam splitter with at least one other polarization rotation stage, wherein the beam splitter that is shared comprises a partially transmitting mirror, wherein each of the polarization adjuster stages are operable to introduce at least a portion of a polarization rotation to the first principal mode in less than one milli-second, and wherein at least one stage of the polarization rotation at least partially operates by reflecting light from a reflective surface;  
   combining one or more polarization rotation portions of the first portion the optical signal wavelengths into a polarization adjusted output signal; and    reflecting the polarization adjusted optical signal to an output.    
   
   
       19 . The method of  claim 18 , further comprising communicating the optical signal for processing, the optical signal comprising a plurality of wavelengths.  
   
   
       20 . The method of  claim 18 , wherein the polarization adjustment system changes state based on one or more voltages applied to the polarization adjustment system.