Optical fiber sensing based on changes in laser emission wavelength

A sensor comprising:

• a light emitter capable of producing stimulated emission, the light emitter comprising a laser diode having multiple longitudinal modes;
• an optical fiber comprising at least one fiber Bragg grating, a first end of the optical fiber optically coupled to a first emitting end of the light emitter, the fiber Bragg grating located at a measurement region of the optical fiber away from the first end, a change in wavelength of the laser emission in the optical fiber being induced by a change in peak reflectivity of the fiber Bragg grating, the change in the peak reflectivity occurring in response to an environmental change at the measurement region;
• and
• an optical detector coupled to the optical fiber or the light emitter, the optical detector detecting the change in the wavelength wherein the change in the wavelength comprises a discrete change in the wavelength due to mode hopping, the change in the wavelength indicative of the environmental change.