This advanced service, also known as narrowcast, is expected to become a significant portion of the revenue stream for cable operators, but networks carrying the video services must be engineered in a way that is both cost-effective and operationally efficient. WDM has traditionally been a powerful tool to move large amounts of aggregate traffic from point to point in long haul and metro networks, making the most efficient use of existing fiber assets.

Today, Cable operators are using WDM to split fiber nodes (node segmentation) in order to provide more bandwidth and more services to the home and at the same time provide secure and reliable fiber connections for use in commercial services, all on the existing network. DWDM also permits operators to multiplex different services on a single fiber by using different wavelengths.

This allows scarce fibers to be used efficiently. For example, applications like telephony, data networking, and VOD can all be transported via a single fiber, in which case, each application has a dedicated wavelength. However, a DWDM-based HFC access network must be able to deliver these services at costs dramatically less than backbone or even metro-based DWDM networks.

Also, the HFC cable plant needs to support a combination of analog and digital broadcast, VOD unicast, voice (VoIP or TDM), and high speed data. In the case of analog broadcast, one of the critical requirements is the use of externally modulated narrow linewidth lasers to reduce dispersion-induced, second-order distortion. The narrow linewidths afforded by externally modulated transmission allow for distortion-free transmission over distances in excess of 100 km. Peleton’s MCLA products are particularly suited for these applications where low cost mixed analog-digital modulation format are required.