From point-to-point WDM transmission to the WDM photonic layer

With today's explosion of on-line services and the anticipated emergence of broadband services, traffic demand will grow quickly, requiring a huge increase in transmission capacity. Wavelength-division multiplexing (WDM) is receiving considerable attention from network operators as an efficient and cost-effective solution to provide high-capacity point-to-point transmission on their already installed fibre plant. An even more compelling case for the introduction of WDM, beyond transmission capacity expansion, is the potential for building a flexible photonic network layer, complementary to the existing transport layer. In this photonic overlay, optical add/drop multiplexers (OADM) and cross-connects (OXCN) will route optical channels, identified by their wavelength, directly. Finally, remaining issues, such as network management and standardization, will be addressed.