Optical fiber sensor and change detection method
The optical fiber sensor includes a setting unit which sets a section to be evaluated set in the optical fiber to one of a first section and a plurality of second sections, each of which is shorter than the first section, an extraction unit which extracts a state change of light from the optical fiber, and a detection unit which detects a change in the surrounding environment based on time-series data of the state change of light in the section to be evaluated.
1 . An optical fiber sensor that detects a change in a surrounding environment of an optical fiber, comprising:
a memory storing software instructions, and
one or more processors configured to execute the software instructions to
set a section to be evaluated set in the optical fiber to one of a first section and a plurality of second sections, each of which is shorter than the first section;
extract a phase difference in a backscattered light from the optical fiber, and
detect a change in the surrounding environment based on time-series data of the phase difference in the section to be evaluated,
wherein the one or more processors are configured to execute the software instructions to switch the section to be evaluated between the first section and the second section when determining a time average of amplitude of time-series data of the phase difference in the section to be evaluated exceeds a predetermined value.
2 . The optical fiber sensor according to claim 1 , wherein
the one or more processors are configured to further execute the software instructions to
determine a feature of a signal based on the signal including information on the phase difference, and
switch the section to be evaluated between the first section and the second sections in response to a determination that the determined feature matches a predetermined acoustic feature.
3 . The optical fiber sensor according to claim 1 ,
the one or more processors are configured to further execute the software instructions to
set the section to be evaluated to a plurality of short sections, each of which is shorter than the second section, and
identify the short section presenting a maximum value of a time average of amplitude of the time-series data of the phase difference in each of the plurality of short sections.
4 . The optical fiber sensor according to claim 1 , wherein
the one or more processors are configured to execute the software instructions to set the second section to a length shorter than a half the length of the first section.
5 . The optical fiber sensor according to claim 1 , wherein
one optical fiber microphone is formed by an entire length or a part of the optical fiber wound around a cylindrical resonant medium that resonates to an acoustic signal.
6 . A change detection method for detecting a change in a surrounding environment of an optical fiber, comprising:
setting a section to be evaluated set in the optical fiber to one of a first section and a plurality of second sections, each of which is shorter than the first section;
extracting a phase difference in a backscattered light from the optical fiber, and
detecting a change in the surrounding environment based on time-series data of the phase difference in the section to be evaluated,
wherein the section to be evaluated is switched between the first section and the second section when determining that a time average of amplitude of time-series data of the phase difference in the section to be evaluated exceeds a predetermined value.
7 . The change detection method according to claim 6 , further comprising:
determining a feature of a signal based on the signal including information on the phase difference, and
switching the section to be evaluated between the first section and the second sections when determining that the determined feature matches a predetermined acoustic feature.
8 . The change detection method according to claim 6 , further comprising:
setting the section to be evaluated into a plurality of short sections, each of which is shorter than the second section, and
identifying the short section presenting a maximum value of a time average of amplitude of the time-series data of the phase difference in each of the plurality of short sections.
9 . A non-transitory computer readable recording medium storing a change detection program, wherein
the change detection program causes a computer to execute:
setting a section to be evaluated set in the optical fiber to one of a first section and a plurality of second sections, each of which is shorter than the first section;
extracting a phase difference in a backscattered light from the optical fiber, and
detecting a change in the surrounding environment based on time-series data of the phase difference in the section to be evaluated,
wherein the section to be evaluated is switched between the first section and the second section when determining that a time average of amplitude of time-series data of the phase difference in the section to be evaluated exceeds a predetermined value.