ose functions in the optical layer gives carriers a flexible way to reconfigure their networks for the same or even lower deployment and operation costs. The optical core uses OXCs to manage high-speed traffic, while traditional SONET equipment moves to the edge to manage the lower-speed interfaces and protocol mixes. Also, non-SONET equipment such as GbE switches, 10 GbE switches, and Resilient Packet Ring (RPR) devices can be supported by the optical core. First-generation (1G) crossconnects had optical inputs and outputs, but used an electronic switching matrix in between. Here, in order to switch the wavelengths, the crossconnect converts optical signals to electrical signals Chapter 2 and then converts them back to optical signals. This O-E-O conversion makes the switching process inefficient and expensive. Second-generation (2G) crossconnects have the capability of switching wavelengths without an electrical conversion (O-O). There are a number of advantages to using OXCs: All-optical crossconnects have a simpler design than O-E-O devices. The number of devices and interfaces used for O-E-O conversion is eliminated from the all-optical crossconnect. This speeds up network upgrades because various elements and interfaces do not have to be adjusted to accommodate new speeds and feeds of the system. It is easier to operate the network with an O-O device because of the automation and remote control functions available. Testing and provisioning can be performed on the entire network from a single location. Three primary technologies have been developed to build all-optical crossconnects: 1. Micro-Electro Mechanical Systems (MEMS) 2. Bubble technology 3. Liquid crystal technology Micro-Electronic Mechanical Systems (MEMS) MEMS technology is used in wavelength switching and OXCs. MEMS devices are based on the mechanical positioning of very small mirrors that direct wavelength signals between input and output ports. These compact devices are silicon wafers with a matrix of moveable mirrors. When switching output po