With business services and wireless backhaul needing an increasing amount of bandwidth, scalability is a requirement for any technology used to provide them. Although talked about for a number of years, WDM PON is ready for primetime and can be used to deliver 40 separate wavelengths at varying and increasing levels of bandwidth, said Rob Adams, Transmode VP of product management.
"Because you are rolling out an entire wavelength to the customer, there is infinite expandability for the future," Adams said. "You can deploy 1 Gbps (for example), and then when the demand is for more, you can add a higher rate of laser to get a higher rate of service out to the customer. You don't have to throw out the infrastructure."
Alternative technologies include PON and CWDM. With the former, fiber is pushed to the customer, but what you see is what you get, so to speak. "You can (build out) 10 Gig and divvy it up to 32 subscribers, but you are (then) limited to 10 Gig. You only get 10 Gig amongst all those subscribers. This is too limiting," Adams said, noting that with the next generation of LTE, cell towers could each require a gig. "(With LTE advanced) 10 Gig PON will only service 10 towers."
CWDM allows for only 16 separate wavelengths, each of which requires a separate laser. WDM PON, on the other hand, only uses one injection lock laser for all 40 wavelengths. Each wavelength has a seed light of a different color. It shines down the transmission fiber and tells the laser to lock to a specific frequency.
The installation of the seed lights makes the initial setup cost of WDM PON more expensive than CWDM. However, a WDM PON system with at least four to six customers beats out a similar CWDM system in terms of cost efficiency due to the cost of lasers, Adams said. "With WDM PON, the cost of providing each individual customer service is about a third of the cost compared to CWDM."
Other advantages to WDM include the ability to run one fiber to a remote point and then branch off to individual customers. "Instead of running fiber from the central office to each business (customer), with WDM PON you can run a single fiber out 10 km (for example). Then where the (cost of installing) fiber is cheaper, you can run fiber out to the (business) parks," Adams said, noting that this reduces infrastructure costs.
Currently in the United States, deployments of WDM PON have been mostly on the telco side, but Transmode has at least one MSO ready to test.
"Pretty much every MSO we have talked to is still taking," Adams said. "They have an interest. They see the problem that we built this to solve. The rate business services and backhaul (need bandwidth) is climbing faster than they can keep up with. They need to push fiber, but also (to) have a technology that is scalable and will not cap off in a year or two."
Monta Monaco Hernon is a free-lance writer. She can be reached at [email protected].