Phasar devices for WDM networks

The rapid growth in demand for bandwidth in telecommunication links created by the increase in Internet and high-speed data traffic and the speed limitation of single wavelength links has resulted in an increase in the deployment of wavelength division multiplexing (WDM) techniques in advanced lightwave systems. In WDM, the fiber bandwidth is easily accessed in the wavelength domain and it is possible to perform functions such as switching and routing. WDM can employ existing intensity modulation-direct detection systems and offers the advantage of being protocol and bit-rate independent. A typical WDM link is shown. Various techniques (fiber based gratings, bulk gratings, thin film, arrayed waveguide gratings) exist to fabricate the wavelength multiplexers and demultiplexers which are needed to combine the signals at the transmitter side and separate the distinct signals at the terminal end. Arrayed waveguide gratings (PHASARs) made by planar fabrication techniques are a particularly attractive approach to devices with high port counts, narrow channel spacing and low cost; moreover they are highly versatile components which can be integrated into wavelength selective switches such as add/drop multiplexers (ADM) and optical crossconnects (OXC).