13.2. WAVELENGTH-SWITCHING SUBSYSTEMS
Dense wavelength division multiplexing (DWDM) is now widely used in transport networks around the world to carry multiple wavelengths on a single fiber. A typical DWDM transmission system may support up to 96 wavelengths, each with a data rate of up to 2.5 or 10 Gbps. At present, these wavelengths usually undergo optical-electrical-optical (OEO) conversions at intermediate switching points along their end-to-end paths. In addition to being expensive, OEO conversions introduce bit-rate and protocol dependencies that require equipment to be replaced each time the bit rate or protocol of a wavelength changes .
By switching wavelengths purely in the optical domain, all-optical switches obviate the need for costly OEO conversions, and provide bit-rate and protocol independence . This allows service providers to introduce new services and signal formats transparently without forklift upgrades of existing equipment. All-optical switching also promises to reduce operational costs, improve network utilization, enable rapid service provisioning, and improve protection and restoration capabilities .
As the capacity of DWDM transmission systems continues to advance, the most critical element in the widespread deployment of wavelength-routed all-optical networks is the development of efficient wavelength-switching technologies and architectures. Two main types of MEMS optical switches have been proposed and thoroughly covered in previous research: ...