A fiber-optic sensor having a Michelson sensor portion and a Mach-Zehnder sensor portion, and an operative coupling therebetween configured to enable the sensor to detect a disturbance, the sensor comprising: a first fiber portion and a second fiber portion defining a sensitive portion of the sensor, each extending between respective proximal and distal ends; a first splitter-coupler positioned adjacent the proximal ends of the first fiber portion and the second fiber portion and configured to split incoming light between the first fiber portion and the second fiber portion; a first detector and a second detector; characterized by a coupler positioned adjacent the respective distal ends of the first fiber portion and the second fiber portion; a first polarization-phase conjugation device configured to conjugate a polarization phase of incident light corresponding to the first fiber portion and a second polarization-phase conjugation device configured to conjugate a polarization phase of incident light corresponding to the second fiber portion; a second splitter-coupler positioned adjacent the distal end of the first fiber portion and configured to split light from the first fiber portion toward the first polarization-phase conjugation device and toward the coupler; a third splitter-coupler positioned adjacent the distal end of the second fiber portion and configured to split light from the second fiber portion toward the second polarization-phase conjugation device and toward the coupler, wherein the first splitter-coupler is further configured to combine light reflected by the first polarization-phase conjugation device through the first fiber portion with light reflected by the second polarization-phase conjugation device through the second fiber portion, and to direct the combined light toward the first detector; a third fiber portion defining an insensitive portion of the sensor and having a distal end configured to receive light from the coupler and a proximal end configured to direct light from the coupler toward the second detector, wherein a distal end of the third fiber portion is positioned adjacent the respective distal ends of the first fiber portion and the second fiber portion and the proximal end of the third fiber portion is positioned adjacent the respective proximal ends of the first fiber portion and the second fiber portion, wherein the sensor is configured to estimate a location of a disturbance to the sensitive portion of the sensor from a first optical signal detected by the first detector and a second optical signal detected by the second detector. a first fiber portion and a second fiber portion defining a sensitive portion of the sensor, each extending between respective proximal and distal ends; a first splitter-coupler positioned adjacent the proximal ends of the first fiber portion and the second fiber portion and configured to split incoming light between the first fiber portion and the second fiber portion; a first detector and a second detector; characterized by a coupler positioned adjacent the respective distal ends of the first fiber portion and the second fiber portion; a first polarization-phase conjugation device configured to conjugate a polarization phase of incident light corresponding to the first fiber portion and a second polarization-phase conjugation device configured to conjugate a polarization phase of incident light corresponding to the second fiber portion; a second splitter-coupler positioned adjacent the distal end of the first fiber portion and configured to split light from the first fiber portion toward the first polarization-phase conjugation device and toward the coupler; a third splitter-coupler positioned adjacent the distal end of the second fiber portion and configured to split light from the second fiber portion toward the second polarization-phase conjugation device and toward the coupler, wherein the first splitter-coupler is further configured to combine light reflected by the first polarization-phase conjugation device through the first fiber portion with light reflected by the second polarization-phase conjugation device through the second fiber portion, and to direct the combined light toward the first detector; a third fiber portion defining an insensitive portion of the sensor and having a distal end configured to receive light from the coupler and a proximal end configured to direct light from the coupler toward the second detector, wherein a distal end of the third fiber portion is positioned adjacent the respective distal ends of the first fiber portion and the second fiber portion and the proximal end of the third fiber portion is positioned adjacent the respective proximal ends of the first fiber portion and the second fiber portion, wherein the sensor is configured to estimate a location of a disturbance to the sensitive portion of the sensor from a first optical signal detected by the first detector and a second optical signal detected by the second detector.