WDM filtering and packaging technologies using planar lightwave circuits

Recently developed technologies for PLC filtering and packaging are presented, with the focus on athermalization and a scheme for highly-reliable coupling between PLCs and fiber. Changes in the center wavelength λ_c of most PLC devices, such as AWGs and PLC Bragg gratings, are produced by the temperature dependence of the refractive index and the thermal expansion coefficient of materials. There are two approaches to the athermalization of a PLC. One is to introduce strain to the PLC in such a way that the overall effect is cancelled out. The other approach is to introduce a compensating material along the optical path. We have also developed a technique for fusion splicing between a PLC and fiber.