It’s time to add a new passive optical network (PON) spec to the broadband glossary. CableLabs has issued the architecture specification for coherent PON (CPON), which is expected to deliver up to 100 Gbps peak capacity, exceeding any of today’s PON standards.
Equipment supporting the standard is expected to be available in about five years, said Curtis Knittle, vice president of wired technologies for CableLabs, in an interview with Telecompetitor. Seventeen vendors and 14 service providers are participating in the CPON working group, according to a CableLabs blog post.
CPON will use coherent optic technology currently found primarily in point-to-point long-haul applications and between data centers. But as with all PON technology, CPON will be a point-to-multipoint offering.
“We’re now seeing capacity in the access network reach a point where coherent . . . is the best option when you consider capacity and the distance that needs to be covered,” said Knittle.
As the CableLabs blog post explains, current PON standards from both the ITU and the IEEE rely on intensity-modulation direct-detect (IM-DD) technology, which is approaching limits in terms of capacity and network reach.
In comparison, “coherent allows more bits per symbol,” explained Knittle.
Coherent technology never made its way into the access network before because it was too expensive. But according to Knittle, service providers should be able to justify the cost, thanks to increased scale and technology advancements.
One consideration is that the PON can become an “infrastructure play” and begin to play a role in aggregation as well as access, Knittle said.
Traditionally, point-to-point fiber links have been used for aggregating remote PHY and remote OLT devices and the like. But Knittle sees both CPON and 50G PON potentially being used for aggregation.
Another advantage of CPON will be extended reach, according to CableLabs. CPON is expected to cover distances of up to 80 kilometers.
As Knittle explained, “We can go four times farther than traditional PON with the same split ratio or you can split it 16 times more if you keep the same distance.”
Telecompetitor originally spoke with Knittle and with CableLabs CEO Phil McKinney about CPON in early 2022. At that time, McKinney noted that the extended distance that CPON will support should make it well suited for deployment in rural areas.
Updated to clarify that CPON is expected to deliver up to 100 Gbps peak capacity and to clarify a comment from Knittle about CPON costs.
