Nov 29, 2023

Connecting Last-Mile Customers at 100 Gbps Leveraging High-Launch-Power Coherent Pluggable Optics

On an on-going basis, service providers – including middle-mile providers – strive to identify cost-effective, environment-friendly solutions to connect last-mile customers at data rates between 1 and 100 Gbps (as well as for rates of hundreds of Mbps).

Efficient solutions have already been identified for connecting last-mile customers at 1 Gbps and 10 Gbps. A large number of deployments leverage standard-based pluggable optics that can be installed in switches and routers to achieve this. Examples of these pluggable optics are 1 Gbps and 10 Gbps DWDM optics that can support distances up to 80 km over metro fiber.

Similar pluggable-based solutions that connect last-mile customers to middle-mile providers at 100 Gbps exist for shorter distances, typically under 30 km. For longer distances, one commonly deployed solution consists of provisioning the 100 Gbps service between the middle- and last-mile providers via a pair of data center interconnect devices (DCI).

While these solutions work well for most deployments, in some cases delivering 100 Gbps connectivity to customers using DCI hardware can be an over-provisioned solution, given that such hardware can in some cases be capable of 400+ Gbps connectivity. This can result in unoptimized power consumption and higher capital and operations expenses.

A New Solution for Metro Deployments

However, a new set of solutions is emerging for delivering 100 Gbps connectivity to last-mile providers in a more efficient manner. These solutions leverage high-launch-power (i.e. high-transmit-power) coherent pluggable optics that can be installed in switches, routers, and small factor space- and power-optimized optical shelves. The latest generation of high-launch-power coherent pluggable optics compliant with the OpenZR+ Multi-Source Agreement (MSA) can deliver 100 Gbps connectivity over an unamplified metro segment up to 80 km – and beyond if the metro fiber is low-loss.

The high-transmit-power capability of these OpenZR+ optics is the key in making this solution very attractive for the 80 km metro use case in a power consumption envelope that does not exceed 25W per optic. In addition, these new high launch power OpenZR+ based solutions come with advanced, standard-based error correction techniques built into the optic’s hardware, virtually guaranteeing error-free performance end-to-end.

"High-launch-power OpenZR+ has been gaining adoption among service providers at high data rates, closer to 400 Gbps,” said Sana Bellamine, Vice President of Engineering at the CENIC California Middle-Mile Broadband Initiative, LLC dba GoldenStateNet. “They can also be an efficient solution for an important set of use cases when deployed at 100 Gbps where high-launch-power OpenZR+ optics can support longer fiber spans and therefore can be an efficient solution for delivering 100 Gbps connectivity to customers over metro fiber.”

Bellamine added, “While this solution has not yet been widely adopted in metro deployments, we anticipate that it will very likely gain adoption among service providers in the coming year.”

The current generation of high-launch-power coherent OpenZR+ compliant optics from many vendors require that the terminating device hosting the high-launch-power coherent pluggable optic have QSFP-DD form factor ports. However, the majority of last-mile providers have not upgraded their border equipment to have QSFP-DD ports and can only support QSFP-28 form factor ports. In these cases, an external small factor optical shelf with a QSFP-DD port terminating the fiber facing the middle mile provider, and a QSFP-28 handoff port to the last mile provider can be used as a solution, eliminating the need for the last mile provider to upgrade their border equipment.

Learn More at our Annual Conference

If you’d like to learn more about this and other topics of interest and chat with CENIC engineers about the latest network technology, be sure to join us in Monterey, California next March 25-27th for The Right Connection, a conference created by and for the CENIC community. Early bird registration is now open, so be sure to register and book your rooms under a special discounted rate!

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