Comcast checking out hollowcore fiber

April 21, 2022
The U.S. Tier 1 cable MSO says it has already demonstrated the fiber’s ability to support coherent transmission, data rates from 10G to 400G, and single-fiber bidirectional operation.

Comcast says it has deployed a 40-km route with hollowcore fiber (in a hybrid cable alongside conventional fiber) from Lumenisity in Philadelphia and has begun evaluating its performance. The U.S. Tier 1 cable MSO says it has already demonstrated the fiber’s ability to support coherent transmission, data rates from 10G to 400G, and single-fiber bidirectional operation.

The 40 km is the longest publicized deployment by an ISP; BT deployed a 10-km testbed (see “BT testing hollowcore fiber for 5G support”), while a 7-km link with euNetworks is Lumenisity’s longest announced commercial deployment (see “euNetworks deploys more hollowcore fiber cable”). Hollowcore fiber’s utility traditionally has been hampered by reach limitations from poor attenuation performance. However, Lumenisity believes its nested anti-resonant nodeless fiber (NANF; see "Startup Lumenisity unveils hollowcore fiber cables for DWDM applications, new funding") provides a pathway toward a solution to such problems. In fact, the company has announced a second generation of its fiber, called DNANF (with “D” for “double”), that the company asserts will offer lower loss in the O-Band and comparable or better loss in the C-Band than standard single-mode fiber. Lumenisity expects to offer such fiber within its CoreSmart cables toward the end of this year.

Comcast’s link uses the existing generation of NANF, and the route’s 40 km is enough to get the attention of Elad Nafshi, executive vice president and chief network officer at Comcast Cable. “Forty kilometers, that’s starting to be real,” he told Lightwave. While he declined to speculate about potential future deployments, Nafshi noted that hollowcore fiber links could benefit customers seeking the lowest latency possible or where latency concerns previously have limited the distance between network elements. Sources at BT had mentioned similar attributes in describing the rationale for their investigations of hollowcore fiber.

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