Patent ID: 7995874

Claim:
An optical fiber distribution type detecting method of measuring Brillouin scattered light outputted from an optical fiber at least partly placed in an object, so as to detect an amount of physical change at a specific location of the object, said method comprising: a control step of allocating at least one search domain as a detecting subject to at least part of a region to be measured in the optical fiber placed in the object before supplying the optical fiber with probe light and pumping light modulated with the same modulation frequency and modulation index in a state maintaining a predetermined phase difference therebetween, said control step including a domain control substep of determining a length of the search domain by regulating the modulation frequency and modulation index, and a location control substep of determining a location of the search domain by regulating the phase difference between the probe light and pumping light; a measurement step of receiving, as output light from the search domain specified as the detecting subject by said control step, the probe light having acquired a gain by Brillouin scattered light occurring as the probe light and pumping light propagate through the specified search domain, and measuring data related to a form of a Brillouin gain spectrum as a spectrum of the gain acquired by the received probe light; and a detection step of detecting a temperature change or strain change of the optical fiber in the specified search domain in accordance with the data related to the form of the Brillouin gain spectrum of the received probe light measured in said measurement step; wherein said measurement step and detection step are carried out repeatedly at a fixed interval of time or every time at least one of incidents of changing the length of the search domain in said domain control substep and changing the location of the search domain in said location control substep occurs.