Ultraweak intrinsic Fabry-Perot cavity array for distributed sensing.

This Letter reports on an ultraweak intrinsic Fabry-Perot interferometer (IFPI) array fabricated by a femtosecond (fs) laser for distributed sensing applications. Ultralow reflectors (<-60  dB) were obtained. IFPIs with different physical lengths showed identical temperature sensitivity (-1.5  GHz/°C). A distributed temperature sensing test was conducted. No crosstalk between IFPI elements in the array was observed, implying the device's utility as a distributed sensing system. The possibility of using smaller bandwidths for sensor interrogation was experimentally proven. A small-scale temperature distribution test was conducted on a continuously cascaded ultraweak IFPI array, demonstrating its high spatial resolution. The temperature detection limit of this system was measured to be less than 0.0667°C.