Phase-front-modulation sensor

A sensor comprising:

• at least one optical waveguide configured to emit light in a direction;
• and
• an optical reflector optically coupled to the at least one optical waveguide, the optical reflector configured to reflect at least a portion of the light, the optical reflector comprising:
• a first portion of the optical reflector configured to reflect a first portion of the light back to the at least one optical waveguide;
• and
• a second portion of the optical reflector configured to reflect a second portion of the light back to the at least one optical waveguide, the second portion of the optical reflector responsive to a perturbation by moving relative to the first portion of the optical reflector, the reflected second portion of the light differing in phase from the reflected first portion of the light by a phase difference that is not substantially equal to an integer multiple of 7C when the second portion of the optical reflector is in an equilibrium position in absence of the perturbation.