Coherent Extrinsic Fiber-Optic Sensors

Theoretical and practical details of free space and fiber-optic interferometry are discussed. Numerical simulation of a fiber sensor employing fiber that is both linearly and circularly birefringent is used to illustrate how fiber effects cause signal fading--and how these effects can be compensated for. Experimental techniques useful in heterodyne signal processing and fiber sensor construction are outlined. Several coherent remote sensing probes are discussed. Stable, high sensitivity remote sensors capable of electric field measurements of 1 V/m, magnetic field measurements less than 3 nT, and GaAs birefringence mapping are illustrated. Finally, a free space heterodyne interferometer is used to probe surface slope characteristics of samples.