Fiber optic pressure and/or vibration detector

A fiber optic pressure/vibration sensor for measuring pressure variations due to acoustic waves or the like and/or measuring vibrations of a body under test is described. The sensor includes a light source, a multimode single optical fiber for transmission of light from the light source from one end thereof to a fiber optic probe having a reflector at the other end of the optic fiber. The movement of the reflector under the influence of impinge acoustic waves or the vibrations of a body under test modulates of the light. The reflected light is carried by the same single optical fiber to a fiber optic couple which sends the reflected light through another coupled optical fiber on to a photodetector to generate and measure the electrical signals produced due to the pressure variations or vibrations of the body under test.