High speed distributed temperature sensing with auto correction

A system for auto-correcting temperature measurement comprising:

• a. a first source configured to provide a primary light signal;
• b. a second source configured to provide a secondary light signal;
• c. a distributed fiber optic sensor that receives the primary and secondary light signals and that is configured to generate back-scattered Stokes and anti-Stokes bands for each of the primary and secondary light signals, wherein a Rayleigh component of the primary light signal overlaps with the Stokes band of the secondary light signal and a Rayleigh component of the secondary light signal overlaps with the anti-Stokes band of the primary light signal;
• d. a wave division multiplexer (WDM) for continuously receiving the primary light signal and the secondary light signal and passing a resulting combined signal into the distributed fiber optic sensor;
• wherein the WDM also acts as a de-multiplexer, separating the backscattered light from the distributed fiber optic sensor into an anti-Stokes band from the primary light signal and a Stokes band from the secondary light signal;
• e. two notch filters that match the wavelengths of the Rayleigh components of the primary and secondary light signals and that continuously receive, from the WDM, the anti-Stokes band from the primary light signal and the Stokes band from the secondary light signal and filter out the Rayleigh components of the primary and secondary light signals;
• f. two photo detectors for receiving signals from the notch filters and measure the intensity of each;
• g. a signal processor configured to receive output from the photo detectors and to calibrate and measure the temperature distribution along said distributed fiber optic sensor based on the ratio of the intensity of the anti-Stokes band of the primary light signal and the Stokes band of the secondary light signal.