Chapter 9 - Planar Lightwave Devices for WDM

Abstract

Optical waveguiding provides efficient interactions in lasers and modulators and novel functionality in waveguide grating routers and the Bragg gratings. These elements are often linked together with waveguides. An overview of photonic integrated circuits that are used in the Wavelength–Division Multiplexed (WDM) optical networks has been provided in the chapter. The main strengths of these integrated devices are the ability to have long interaction lengths, their compact size, their low insertion loss, and, most importantly, their large-volume manufacturability. The chapter also describes a large number of innovative planar devices such as the dynamic gain equalizer, the wavelength selective cross connect, the wavelength add or drop, the dynamic dispersion compensator, and the multifrequency laser. The various waveguide materials—including silica, lithium niobate, semiconductor, and polymer—are also compared. It is noted that the refractive index of silica matches with that of the fiber and the propagation loss is also very low, thus, making silica highly durable and ideal for the fiberoptic systems.