Patent ID: 7154659

Claim:
A device, comprising: a polarization beam splitter (PBS) to receive an input optical beam with a coherent length and to split the input optical beam into a first beam and a second beam polarized orthogonal to said first beam; a first reflector positioned relative to said PBS to reflect said first beam back to said PBS; a 45-degree Faraday rotator located in front of said first reflector to change a polarization of light passing therethrough; a fiber coupled between said PBS and said Faraday rotator to transmit said first beam between said PBS and said first reflector; a second reflector positioned relative to said PBS to reflect said second beam back to said PBS; and a polarization element located between said second reflector and said PBS to rotate a polarization of a reflection of said second beam at said PBS to be perpendicular to said second beam when initially exiting said PBS, wherein said first and said second reflectors are positioned to produce a difference in optical paths of said first and said second beams upon being reflected back to said PBS.