JPS57113327A - Low temperature position detecting system by optical fiber - Google Patents

Abstract

PURPOSE:To enable simple detection of a temperature change occurring position in a wide measuring range, by a method wherein an optical fiber, which is sharply increased in an optical transmission loss at low temperature, is connected at every arbitrary lengthes for mounting to measure a quantity of a back scatter light against incident light. CONSTITUTION:An optical fiber 1, showing a steep increase in an optical transmission loss at a low-temperature region, is connected at every arbitrary lengths l1-l2 at a zone to be measured of temperature through connection parts A-N wherein the optical transmission loss changes. A light incident terminal is connected to a luminous source 3, and an amount of a back scatter light is measured by the incident terminal to approximately orientate a temperature change occurring position from a position relation of a measurement light corresponding to each of the connection parts A-N to a measured light corresponding to increase in the optical transmission loss at a low-temperature region X. For example, a pulse light, generated in the luminous source 3, is caused to enter the optical fiber 1, a back scatter light is collected at a collecting detector 5 through a half-mirror 4, and this performs said orientation.