The performance of high speed WDM lightwave systems will be enhanced by tunable filters in a number of different applications including reconfigurable add/drop multiplexers, dynamic gain flatteners and adjustable dispersion compensators. This paper describes an emerging class of tunable filters based on thermally tuned fiber grating. The devices use uniform and tapered distributed thin film heaters deposited onto the outer surface of the fiber. Current flowing though the films generates resistive heating at rates that vary with the thickness of the film, where tapers in the thickness produce controllable temperature gradients along the fiber. The paper reviews some of the basic characteristics of these devices as well as describing devices that use multiple electrodes for independent tuning of chirp and central wavelength, as well as dynamic chirping of long-period grating devices. We also consider the performance of these devices in systems tests at 10 and 20Gbit/s.
© 1999 Optical Society of AmericaPDF Article