Feedback loop design and experimental testing for integrated optics with micro-mechanical tuning

Abstract

I designed a capacitive sensor with feedback control for precision tuning of a MEMS controlled wavelength-selective switch. The implementation is based upon a customized feedback loop with a PID controller. The positional stability of the bridge can be controlled to within 0.5 [Angstroms], and the tuner has a time constant of 1 gs for the desired 5V actuation voltages. I created a realistic noise model for the capacitive sensor circuit and its controller, and added this to the noise models already developed for the device. Using these models, the parameters of the system can easily be changed to model device performance under varying conditions and device iterations. I also developed an equipment test set-up for accurately measuring the optical properties, both spectral and temporal, of these devices. The apparatus can be modified slightly to be used in testing of other integrated optoelectronic devices. The procedure for aligning lensed fibers to integrated waveguides and optimizing light throughput is described, and some test device values are presented.