SAN DIEGO -- OFC 2018 -- China Telecom believes it will need to deploy more than 2 million 5G-enabled basestations across China to provide its current and anticipated customer base with next generation mobile broadband services, an executive from the operator's research department told a packed plenary session here at OFC this week.

Chengliang Zhang, vice president of China Telecom Beijing Research Institute, said the operator has already launched 5G demos in six cities and plans commercial trials in 2019, with large scale commercial rollout set for the following year. The major 5G network investment period will be 2020 to 2025 but investments will continue for many years after that, noted Zhang.

The operator, which currently boasts 255 million mobile and 135 million fixed broadband customers, will be offering its 5G services using spectrum in the 3.5 GHz or higher frequency band, and, as a result, will need to build out a more dense radio access network to account for the resulting shorter reach. China Telecom currently estimates it may need to deploy more than 2 million 5G-enabled basestations (compared with the 1.16 million 4G LTE-enabled basestations it currently operates), with each basestation requiring fronthaul transport links of up to 25 Gbit/s which will then feed into mid-haul and backhaul links with up to 100 Gbit/s of capacity.

As a result, China Telecom is currently planning and building out a new optical transport network -- coupled with the deployment of edge computing capabilities -- with three separate and distinct projects for its backbone, metro and fiber access networks. The key requirements are greater capacity, lower latency and very high-precision synchronization, especially for services that need to be coordinated across multiple basestations.

Zhang told the optical specialists here at OFC that further innovation is required in the optical transport sector to meet the needs of operators needing to support the anticipated traffic volumes of the 5G era. The 4G era is challenging enough: Zhang noted that volume of mobile data traffic running over its current network each day (on average) stands at 19,000 Tbytes, up by 400% compared with 2016.

So what's needed? A 5G-optimized version of OTN, for one, which would enable small-sized OTN devices and latency as low as just 1 microsecond. China Telecom proposed a specification called M-OTN at a recent ITU-T meeting to try to get industry specifications developed for such needs.

China Telecom isn't just relying on the traditional standards bodies, though. It is one of the members of the NGOF (the Next Generation Optical transport network Forum), which was formed in China in late 2017. That group, which counts Broadcom, Fiberhome, Finisar, Huawei, Lumentum, Nokia, ZTE and China Unicom (but not China Mobile) amongst its members, is aiming to accelerate the speed of innovation in the optical market.

In addition, China Telecom also wants enhancements to current ROADM (reconfigurable optical add-drop multiplexer) designs to enable twice as many "degrees" of switching (from 20 to 40) to support large-scale, fully meshed backbone networks, and to improve the contentionless capabilities of ROADMs, which are currently too complicated, according to Zhang.

It's not surprising that the 5G era optical transport requirements of network operators are highlighted at an optical event such as OFC, but it's something that needs greater attention beyond specialist events and conferences as without greatly improved, and more dense, optical infrastructure in place, all the 5G hopes and dreams of the service providers outlined at events such as MWC will come to nothing. Optical is a critical part of the 5G puzzle.

— Ray Le Maistre, Editor-in-Chief, Light Reading