MICROMECHANICAL FIBEROPTIC ATTENUATOR WITH 3 MU-S RESPONSE

Optomechanical fiber-optic attenuators are bulky and slow. The mechani cal antireflection switch (MARS) modulator offers a high-speed alterna tive for applications including dynamic gain control in fiber amplifie rs, This paper describes a compact electrically controlled variable at tenuator using a micromechanical device where electrostatic deflection of a silicon nitride quarter-wave dielectric layer suspended over a s ilicon substrate creates a variable reflectivity mirror. This device i s packaged with two fibers in one ceramic ferrule placed in contact wi th a gradient index (GRIN) collimation lens, so that the input light r eflects from the modulator in the collimated beam plane and couples in to the output fiber. Using a 300 mu m diameter MARS attenuator and a 5 00 mu m diameter collimation lens, the total insertion loss at 1550 nm was 3.0 dB with no applied voltage, increasing to 31 dB at 35.2 V, Th e polarization dependent loss was less than 0.06 dB, Full attenuation with more than 100 mW input power produced no damage. The response tim e was 2.8 mu s to move from maximum to minimum transmission and 1.1 mu s to return to maximum transmission.