Distributed temperature sensor with shortened sensing regions

A system for the detection of temperature increase of a segment of an optical fiber, the system having:

• a laser optical source enabled by a controller, the laser optical source generating at least one pulse of optical energy in response to a pulsed laser enable input;
• a circulator having an optical input port coupled to said laser output, a bidirectional port coupling energy from an optical output of said laser to a reference loop and to a measurement optical fiber having one or more sensor regions, each said sensor region having a ratio of optical fiber length to sensor extent of at least 10, each said sensor region generating temperature-dependent backscatter optical energy;
• said backscatter optical energy directed by said circulator bidirectional port to a signal port of the circulator;
• one or more photodetectors coupled to said signal port through an anti-Stokes optical filter and/or a Stokes optical filter;
• each said one or more photodetectors coupled to a histogram processor, said histogram processor having a plurality of counters which extend over a count extent, each said count extent associated with a delay time interval associated with a pulsed laser enable;
• whereby said histogram processor estimates the temperature of a sensor region by comparing a photodetector response at the output of an anti-Stokes filter with the photodetector response at the output of the Stokes filter.