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Method and apparatus for differential phase optical coherence tomography

  • US 6,665,456 B2
  • Filed: 01/11/2002
  • Issued: 12/16/2003
  • Est. Priority Date: 01/12/2001
  • Status: Expired due to Term
First Claim
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1. A dual channel optical reflectometer comprising:

  • a broad bandwidth optical light source;

    an optical source path incorporating a depolarizing element that decorrelates optical signals in orthogonal fiber polarization channels and optically connects both channels to a path coupler;

    a path coupler that separates light into birefringent sample and reference paths while maintaining energy separation and decorrelation of optical signals in the fast and slow fiber polarization channels;

    a birefringent optical reference path optically connected to the path coupler and optically coupled to a scanning delay line;

    a birefringent optical sample path optically connected to the path coupler, wherein the birefringent sample path comprises a polarization channel separator/combiner, wherein the polarization separator-combiner divides/reunites optical signals in fast and slow polarization channels into two distinct optical beams that intersect at a single point in the sample under test, wherein the polarization channel separator is optically connected to a beam combiner that reunites optical signals in fast and slow polarization channels;

    the birefringent reference and sample paths are configured so that optical path length differences between fiber reference and sample paths in the fast and slow channels are less than one-half wavelength of incident light;

    a birefringent optical detection path optically connected to the path coupler and a polarization channel separator that is optically coupled to a first and second photoreceivers that produce first and second output signals, respectively, wherein the first and second output signals pass through a bandpass filter and amplifier;

    an analog-to-digital converter connected to the bandpass filter-amplifier; and

    a computer connected to the analog-to-digital converter.

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