A system configured to monitor a plurality of zones of an aircraft, the system comprising: a line replaceable unit comprising: first and second connectors in optical communication; and an optical fiber extending between the first and second connectors, the optical fiber with first and second ends, wherein the first end of the optical fiber is connected to the first connector, wherein the optical fiber comprises: a first plurality of fiber Bragg gratings disposed in the optical fiber; and a plurality of calibration fiber Bragg gratings located in a pattern that provides information related to a first calibration value of the line replaceable unit based upon a center wavelength of each of the first plurality of fiber Bragg gratings; a first interrogator connected to the line replaceable unit at the first end of the optical fiber, wherein the first interrogator is configured to provide a first optical signal to the optical fiber and to receive a first optical response signal from the optical fiber; and a controller operatively connected to the first interrogator and configured to determine the first calibration value of the line replaceable unit based on the first optical response signal; wherein the first plurality of fiber Bragg gratings comprises a plurality of overheat fiber Bragg gratings disposed in the optical fiber; characterised in that: the plurality of calibration fiber Bragg gratings are configured to indicate the first calibration value based upon center wavelengths of the plurality of overheat fiber Bragg gratings. a line replaceable unit comprising: first and second connectors in optical communication; and an optical fiber extending between the first and second connectors, the optical fiber with first and second ends, wherein the first end of the optical fiber is connected to the first connector, wherein the optical fiber comprises: a first plurality of fiber Bragg gratings disposed in the optical fiber; and a plurality of calibration fiber Bragg gratings located in a pattern that provides information related to a first calibration value of the line replaceable unit based upon a center wavelength of each of the first plurality of fiber Bragg gratings; first and second connectors in optical communication; and an optical fiber extending between the first and second connectors, the optical fiber with first and second ends, wherein the first end of the optical fiber is connected to the first connector, wherein the optical fiber comprises: a first plurality of fiber Bragg gratings disposed in the optical fiber; and a plurality of calibration fiber Bragg gratings located in a pattern that provides information related to a first calibration value of the line replaceable unit based upon a center wavelength of each of the first plurality of fiber Bragg gratings; a first plurality of fiber Bragg gratings disposed in the optical fiber; and a plurality of calibration fiber Bragg gratings located in a pattern that provides information related to a first calibration value of the line replaceable unit based upon a center wavelength of each of the first plurality of fiber Bragg gratings; a first interrogator connected to the line replaceable unit at the first end of the optical fiber, wherein the first interrogator is configured to provide a first optical signal to the optical fiber and to receive a first optical response signal from the optical fiber; and a controller operatively connected to the first interrogator and configured to determine the first calibration value of the line replaceable unit based on the first optical response signal; wherein the first plurality of fiber Bragg gratings comprises a plurality of overheat fiber Bragg gratings disposed in the optical fiber;