초록 ▼

An optical fiber apparatus measures an external parameter, such as temperature, at any of a number of different locations using time-domain reflectometry techniques. Sensor devices, each comprising a chip or plate of ruby glass, are interconnected by optical fibers. A laser launches along the fiber

An optical fiber apparatus measures an external parameter, such as temperature, at any of a number of different locations using time-domain reflectometry techniques. Sensor devices, each comprising a chip or plate of ruby glass, are interconnected by optical fibers. A laser launches along the fiber string short pulses of light at a first wavelength on the absorption edge of the ruby glass and a second wavelength in the transmission region away from the edge. A timer controls sampling circuits to measure backscattered energy at each wavelength at spaced times corresponding to spaced points along the fiber on opposite sides of a selected sensor device. A processor calculates the absorption loss in the sensor device at each wavelength by comparing the backscattered energy from the two points on opposite sides of the device, and calculates the differential absorption loss by comparing the losses at the two wavelengths. Embodiments employing a wedge shaped absorber are used to measure displacement. Signal to noise ratio is improved by incorporating retroreflectors in the fiber lengths between sensor devices.

대표청구항 ▼

An apparatus for remotely measuring values of an external parameter at a plurality of locations from a monitoring position, said apparatus comprising: an optical sensor means at each of the locations; lengths of optical fiber serially interconnecting the sensor means to the monitoring position with

An apparatus for remotely measuring values of an external parameter at a plurality of locations from a monitoring position, said apparatus comprising: an optical sensor means at each of the locations; lengths of optical fiber serially interconnecting the sensor means to the monitoring position with the monitoring position at one end of the string of interconnected sensor means, the optical sensor means each being such as to permit light to pass from one optical fiber length to the next with a loss co-efficient through the sensor means which is dependent on the external parameter to be measured; means for launching light pulses into the end of the optical fiber length at the monitoring position and monitoring backscattered energy emerging from said fiber end to determine said loss co-efficient at selected sensor means by optical time-domain reflectometry, said means for launching and monitoring including means to detect and measure the energy of the backscattered light; timing means for controlling the detecting and measuring means to measure the backscattered energies at each of two temporally spaced times selected relative to the time of launching the light pulses to correspond to energy backscattered from a pair of points in the optical fiber lengths on opposite sides of a selected one of the sensor means; and computing means connected to receive from said detecting and measuring means signals representing the two measured backscattered energies and arranged to compute therefrom a value for said loss co-efficient and thence said external parameter which is normalized to minimize any dependence on the launching energy of the light pulse.