Coherence sensing of time-addressed optical-fiber sensors illuminated by a multimode laser diode

A reflective array of optical-fiber sensors multiplexed in time and with their status read using coherence sensing associated with directly modulated multimode laser-diode illumination is investigated. Sensor sensitivity as determined by primary noise sources is evaluated and numerical results are presented. The concept is demonstrated with two all-fiber Michelson interferometers and applied to the measurement of periodic and quasi-static parameters. It is shown that the effect of feedback light into the laser cavity on the level of the system noise floor is negligible, making unnecessary the use of source optical isolation.