Aspects of the present disclosure describe monitoring of optical fiber by distributed temperature sensing (DTS) and determining optical fiber degradation and/or abnormal environmental events including landslides, fires, etc., from DTS data.

Aspects of the present disclosure describe monitoring of optical fiber by distributed temperature sensing (DTS) and determining optical fiber degradation and/or abnormal environmental events including landslides, fires, etc., from DTS data.

An optical fiber temperature distribution measuring device includes: an optical fiber as a sensor; a calculation control unit for measuring a temperature distribution along the optical fiber by using backward Raman scattered light from the optical fiber; a far-end-position dispersion characteristic calculation unit for obtaining a dispersion characteristic of the optical fiber at a far-end position thereof; a per-unit-length dispersion characteristic calculation unit for obtaining a per-unit-length dispersion characteristic of the optical fiber based on the dispersion characteristic of the optical fiber at the far-end position thereof; and a correction parameter calculation unit for calculating a correction parameter for correcting a dispersion characteristic of the optical fiber based on a dispersion characteristic at each of different positions along the optical fiber.

A system may include a sensing fiber that can receive interrogation data via a coil of reference fiber, the coil of reference fiber configurable to be of a same type of fiber as the sensing fiber, and the sensing fiber configurable to be coupled in series with the coil of reference fiber. A known temperature and a known strain can be received from the coil of reference fiber. The known temperature, the known strain, and the interrogation data can be outputted for calibrating a measurement of the interrogation data.

A system may include a sensing fiber that can receive interrogation data via a coil of reference fiber, the coil of reference fiber configurable to be of a same type of fiber as the sensing fiber, and the sensing fiber configurable to be coupled in series with the coil of reference fiber. A known temperature and a known strain can be received from the coil of reference fiber. The known temperature, the known strain, and the interrogation data can be outputted for calibrating a measurement of the interrogation data.

A measurement system includes a cable having a length, a light source, at least one detector, and at least one processor. The light source is operably coupled to the cable and is configured to transmit an optical signal to the cable. The at least one processor is operably coupled to the cable and configured to: receive a scattered signal from the cable responsive to the optical signal transmitted to the cable; map the scattered signal to the length of the cable; and de-convolve a spatial averaging effect of the scattered signal using a weighting profile corresponding to the light source and the cable to generate a distributed property profile defined along the length of the cable.

A temperature distribution measurement apparatus includes a laser light source optically connected to an optical fiber, a photodetector configured to detect light backscattered in the optical fiber, and a temperature distribution measurement unit configured to obtain a true measured temperature distribution by performing correction calculation using a transfer function on a temporary measured temperature distribution obtained based on an output from the photodetector. The temperature distribution measurement unit stores therein data on a transfer function set for each entire length of the optical fiber and for each longitudinal position in the optical fiber. Then, when the length of the optical fiber is changed, the temperature distribution measurement unit changes the transfer function to be used in the correction calculation by using the data on the transfer function.

In some examples, a temperature distribution sensor may include a laser source to emit a laser beam that is tunable over a wavelength range. The wavelength range may be less than a Raman bandwidth in a device under test (DUT), or of-the-order-of the Raman bandwidth in the DUT. A pulsed source may apply a pulse drive signal to the laser beam or to a modulator to modulate the laser beam that is to be injected into the DUT. A bandpass filter may be operatively disposed between the laser source and the DUT, and may be configured to an anti-Stokes wavelength that is narrower than the Raman bandwidth. A photodiode may be operatively disposed between the bandpass filter and the DUT to acquire, from the DUT, anti-Stokes optical time-domain reflectometer traces for two preset wavelengths of the laser beam to determine a temperature distribution for the DUT.

An optical fiber temperature distribution measurement system includes a temperature difference calculator configured to calculate a temperature difference between corresponding spatial resolution zones based on a first temperature distribution obtained by a return light from a first optical fiber part and a second temperature distribution obtained by a return light from a second optical fiber part, and an abnormality detector configured to calculate a temperature difference for evaluation for each spatial resolution zone, the temperature difference for evaluation being a sum of a temperature difference of each spatial resolution zone and a temperature difference of a spatial resolution zone adjacent thereto, and to determine that an abnormality has occurred in a roller near the spatial resolution zone when the calculated temperature difference for evaluation exceeds a reference value.

A pipe type solid insulation cable system includes a plurality of solid insulation cables; a plurality of steel pipes in which the plurality of solid insulation cables are inserted, respectively; and a refrigerant circulation path that includes a plurality of refrigerant pipes, which are provided to be adjacent to the plurality of steel pipes, respectively, circularly connected with each other to circulate a refrigerant therein, wherein the pipe type solid insulation cable system is configured to indirectly cool the plurality of solid insulation cables in the plurality of steel pipes, respectively, by cooling at least a part of a periphery of each of the plurality of steel pipes by the refrigerant circulation path without flowing the refrigerant in the plurality of steel pipes.