Optical fiber sensing device and method
An optical fiber sensing device of the present disclosure includes: an optical fiber sensor system including a plurality of sensor units having different propagation delay times; a first light source for outputting an incident light to the optical fiber sensor system; a second light source for outputting a local light for combining with a transmitted light through the optical fiber sensor system; and a signal processing unit for detecting a change in an optical fiber using a received light signal I(t) obtained by combining the transmitted light and the local light, and, given that τi is an inter-optical-path propagation delay time difference at an i-th sensor unit of the sensor units, a change at the i-th sensor unit is derived using an autocorrelation between an optical intensity I(t) at the sensor unit and a signal I(t+τi) obtained by shifting the optical intensity I(t) by a time τi.
1 . An optical fiber sensing device comprising:
an optical fiber sensor system including a plurality of sensor units having different propagation delay times;
a first light source for outputting an incident light to the optical fiber sensor system;
a second light source for outputting a local light for combining with a transmitted light through the optical fiber sensor system; and
a signal processing unit for detecting a change in an optical fiber using a received light signal I(t) obtained by combining the transmitted light and the local light,
wherein, given that τ i is an inter-optical-path propagation delay time difference at an i-th sensor unit of the sensor units, a change at the i-th sensor unit is derived by the signal processing unit using an autocorrelation between an optical intensity I(t) at the sensor unit and a signal I(t+τ i ) obtained by shifting the optical intensity I(t) by a time τ i .
2 . The optical fiber sensing device according to claim 1 , wherein the propagation delay time τ i of the incident light passing through the i-th sensor unit is shorter than a coherence time of the local light, and a propagation delay time difference |τ i −τ j | compared with the propagation delay time τ j of the incident light passing through the j-th sensor unit of the sensor units (j is a natural number except i) is longer than a coherence time of the incident light.
3 . The optical fiber sensing device according to claim 1 , wherein the optical fiber sensor system comprises a plurality of Mach Zehnder interferometers connected with each other in series, the sensor units are unilateral optical paths in the Mach Zehnder interferometers, and the inter-optical-path propagation delay time differences τ at the sensor units implemented in the plurality of Mach Zehnder interferometers are different from each other.
4 . The optical fiber sensing device according to claim 1 , wherein the optical fiber sensor system comprises the plurality of sensor units connected with each other in parallel, and the propagation delay time T of the incident light passing through the optical fiber sensor system is different for each sensor unit.
5 . The optical fiber sensing device according to claim 1 , wherein the change at the sensor unit is a change in temperature or distortion at the i-th sensor unit.
6 . A method for optical fiber sensing, comprising the steps of:
inputting an incident light from a first light source to an optical fiber sensor system including a plurality of sensor units having different propagation delay times;
combining a local light from a second light source with a transmitted light through the optical fiber sensor system; and
detecting a change in an optical fiber by a signal processing unit using a received light signal I(t) obtained by combining the transmitted light and the local light,
wherein, given that τ i is an inter-optical-path propagation delay time difference at an i-th sensor unit of the sensor units, a change at the i-th sensor unit is derived by the signal processing unit using an autocorrelation between an optical intensity I(t) at the sensor unit and a signal I(t+τ i ) obtained by shifting the optical intensity I(t) by a time τ i .