Patent ID: 8705176

Claim:
An interferometer, comprising: means for splitting, at a splitting location, an input light beam into a first beam and a second beam; means for recombining, at a recombination location, said first beam and said second beam to produce at least one output beam; and means for detecting said at least one output beam; wherein said first beam will travel a first optical path length (OPL) from said splitting location to said recombination location; wherein said second beam will travel a second OPL from said splitting location to said recombination location; wherein, when said input light beam carries phase modulated data with a fixed time interval between two adjacent data symbols, then the difference in optical path lengths between said first OPL and said second OPL is about equal to said time interval multiplied by the speed of light and is set by at least one etalon placed in the path of at least one of said first beam and said second beam.