Silicon Photonics: Fundamentals and Devices

12.5 Applications of AWGs

AWGs perform four basic functions, namely, multiplexer, demultiplexer, passive waveguide router, and add-drop multiplexer used in WDM networks. In addition, they are also used in producing multiwavelength lasers and as tunable elements in photoreceivers. Some of these applications are now described in this section [8–11, 22].

12.5.1 Demultiplexers and Multiplexers

Figure 12.2 illustrates how an AWG can be used as a basic demultiplexer. The multichannel signals are fed to one of the input waveguides via a single fiber. Signals having different wavelengths are focused onto different output waveguides. Separation of the different wavelength components, which is the basic function of the demux, is automatically performed by the AWG. In order to achieve multiplexing, different signals are fed to different input guides of the AWG, all of which are then focused into a single output waveguide as may be visualized if Figure 12.2 and Figure 12.3 are arranged in reverse sense. It may be mentioned at this stage that an integrated four-channel waveguide multiplexer was constructed by some workers by using three MZIs. However, when the number of input wavelengths increases, this type of design involves a larger number of MZIs leading to a complex, oversized structure. The use of a single AWG solves this problem. The number of wavelengths multiplexed currently by AWGs exceeds 1000.

12.5.2 Wavelength Routers

Wavelength routers are essential components in WDM networks. ...