Distributed strain and temperature discrimination in polarization maintaining fiber

A method for analyzing a portion of a polarization maintaining (PM) optical fiber having two polarization states, comprising:

• determining first scatter data of the portion of the PM fiber for first values of temperature and strain;
• determining second scatter data of the portion of the PM fiber for second values of temperature and strain, where at least one of the temperature values or the strain values is different between the first and second sets;
• using the first and second scatter data to discriminate between strain and temperature at the portion of the PM fiber and to determine a change in strain or a change in temperature at the portion of the PM fiber;
• and
• providing a signal based on the determination of the change in strain or the change in temperature at the portion of the PM fiber.

Apparatus for analyzing a portion of a polarization maintaining (PM) optical fiber having two polarization states, comprising:

• optical processing circuitry configured to optically scan a portion of the PM optical fiber over a range of wavelengths to acquire a first light intensity signal and to later optically scan the PM optical fiber to acquire a second light intensity signal;
• and
• data processing circuitry configured to:
• determine a first spectral response of the PM fiber portion based on the first light intensity signal, where each polarization state of the PM fiber portion has a corresponding spectral component in the first spectral response;
• determine a second spectral response of the PM fiber portion based on the second light intensity signal, where each polarization state of the PM fiber portion has a corresponding spectral component in the second spectral response;
• perform a first spectral analysis of the PM fiber portion using the first and second spectral responses;
• perform a second spectral analysis of the PM fiber portion using the first and second spectral responses;
• based on the first and second spectral analyses of the PM fiber portion, determine a first physical characteristic affecting the PM fiber portion distinct from a second different physical characteristic affecting the fiber portion;
• and
• provide an output signal related to the first physical characteristic affecting the fiber portion.

Apparatus for analyzing a portion of a polarization maintaining (PM) optical fiber having two polarization states, comprising:

• Optical Frequency Domain Reflectometry (OFDR) circuitry configured to determine first scatter data of the portion of the PM fiber for first values of temperature and strain and second scatter data of the PM fiber portion for second values of temperature and strain, where at least one of the temperature values or the strain values is different between the first and second sets;
• and
• a data processor configured to use the first and second scatter data to discriminate between strain and temperature at the portion of the PM fiber and to determine a change in strain or a change in temperature at the portion of the PM fiber;
• and
• provide a signal based on the determination of the change in strain or the change in temperature at the portion of the PM fiber.