Fiber-optic evanescent field modulator using a magnetic fluid as the cladding

Abstract

A kind of fiber-optic modulation-depth-tunable modulator is developed in this paper. In this modulator, a magnetic fluid is used as the cladding of the drawn fiber, which attenuates the evanescent field when the light is guided in the fiber. Because the attenuation depends on the strength of the applied external magnetic field, the emergent light intensity from the fiber is modulated with the change of the magnetic field strength. The response times, i.e., the span for the light intensity to reach the final steady value from the time when the magnetic field is turned on or off, are evaluated quantitatively.