Sprint is increasing the capacity of the high-speed fiber links that connect large areas of its network as part of a modernization project that includes the rollout of LTE in conjunction with the decommissioning of its iDEN network.

The operator said Wednesday that it hired Ciena to upgrade its optical backbone network to 40 Gbps and 100 Gbps and that it plans to conduct trials of 400 Gbps links next year. The speeds don’t refer to the total capacity of the fiber-optic cable, but rather the speed of each individual strand.

The new gear will allow Sprint's network to better handle increasing data traffic, a critical ability as it moves to LTE.

"This upgrade allows us to be prepared for the improved speeds we are offering with the LTE network and be able to handle the low-latency applications supporting video and voice over LTE and CDMA," a Sprint spokeswoman said in an email.

Customers in areas with the backbone upgrades will experience faster network speeds. Sprint expects to get gains of "anywhere between 2.5 and 10x capacity and speed improvements and significant improvement in data performance," she said.

Ciena won't be ripping up and replacing fiber that's already in the ground. Instead, it will upgrade the equipment on the end of Sprint's fiber lines to transmit at higher speeds using new signaling technology on its 6500 Packet-Optical platform.

“We’re increasing the capacity that can be carried down the fiber without increasing the fiber itself,” Tom Mock, Ciena’s senior vice president of corporate marketing, said in an interview.

Sprint's current backbone network is a combination of 10 Gbps and 40 Gbps, depending on the location. The new technology will upgrade its fiber nodes to either 40 Gbps or 100 Gbps.

Sprint is already in the process of upgrading its backhaul network, the links between cell towers and switching stations, to Ethernet and microwave, its executives said at a spring conference.

Sprint is still in the planning phase of its 400 Gbps field trails for next year and could not specify how widespread the test run would be. Mock said he couldn't speak directly to Sprint's forthcoming trials but said "most people, when they look to deploy 400 Gbps, will pick a fairly challenging route," such as one several hundreds of miles in distance, like Kansas City to Chicago or Denver to San Francisco.

The deployment is being done as an overlay to its existing optical network "to minimize disruption to our customers" and will eventually replace all the fiber nodes in its network with Ciena's 6500 platform. Ciena first began supplying equipment to Sprint in 1998.