Laser control for intensity otdr using phase-modulated light

An apparatus comprising:

• an optical sensor comprising a laser and a laser controller;
• wherein the optical sensor is configured to split light from the laser into probe light and reference light, to modulate the probe light, to couple modulated probe light into an optical fiber line, and to make measurements on a superposition of the reference light and light returned to the optical sensor by, at least in part, backscattering from the optical fiber line;
• wherein the optical sensor is further configured to estimate a backscattering intensity profile based on said measurements, the backscattering intensity profile representing a set of backscattering intensity values pertaining to a set of longitudinal sections of the optical fiber line, wherein each of the backscattering intensity values represents an intensity of light backscattered from a respective longitudinal section of the optical fiber line;
• and
• wherein the laser controller is configured to adjust a wavelength of the laser based at least in part on mismatch between at least a portion of the backscattering intensity profile and a reference profile.