ABSTRACT
This chapter focuses on the progress of planar lightwave circuit (PLC) type devices with advanced functions developed for the photonic networks. It describes silica-based PLC fabrication techniques and device characteristics of arrayed waveguide gratings (AWG) and thermo-optic PLC switches (TO PLC-SW), followed by a detailed description of polymer-based PLCs, such as Y-branch PLC-SWs and TO tunable filters. Silica-based PLCs have excellent physical and chemical stability and good compatibility with optical fibers. Silica-based optical waveguides are fabricated on silicon substrates. The first step is to use flame hydrolysis deposition to deposit two successive glass particle layers that serve as the under cladding and the core. The AWG multi/demultiplexer is one of the most successful optical filters, and is a key component of photonic networks. Silica-based TO PLC-SW unit can be made by a combination of a Mach–Zehnder interferometer consisting of two 3-dB directional couplers and two waveguide arms equipped with a thin film heater, which operates as a TO phase shifter.
