Huawei takes WDM outdoor for fronthaul fibre connectivity

It's a world first for fronthaul, but we're not sure why yet.

Huawei has claimed the launch of the “world’s first fully outdoor WDM unit”, designed to carry CPRI services between remote radios and centralised or cloud-based baseband units.

Huawei believes there will be requirement for WDM-based fibre fronthaul  due to CPRI’s intensive consumption of optical fibre resources, and the lower reliability and the lack of “supervisory measures” for managing fibres.

A Huawei release claimed:
“The outdoor Huawei WDM product replaces optical fibre  connections with WDM technology. This results in a pair of optical fibres able to withstand more than 100 pairs of CPRI services. Also, the Huawei product reduces network investment and shortens service deployment time, providing a highly reliable network by using a unique delay compensation technology. The product also supports remote performance monitoring and uses a network management system to precisely locate faults. To ensure it is suitable for outdoor use it has a compatible design, supporting 614 Mbit/s to 9.8 Gbit/s (CPRI1-CPRI7) service on the client side. This specific design provides a product suitable for covering high-density and large-capacity metropolitan areas.”

TMN asked Huawei on 5 May what they meant by a world first for outdoor WDM fronthaul. Unfortunately they have not been able to answer us – yet – so we can’t be sure what they are claiming as a world first.

An industry source at another vendor that is also targetting the fronthaul WDM opportunity was less than impressed, providing the following notes:

“This is nothing new for fronthaul. They use industrial temp pluggable optics in the radio head and temperature-hardened CWDM filters deployed in an outdoor enclosure. More a question of selecting the right component than developing a product. The other end on the baseband unit side typically resides in controlled environment.

“I don’t believe that Huawei developed an outdoor version of a specific transponder for an active solution. Too costly for this application. A workaround could be working with [third party] companies, deploying existing gear mounted in one of their enclosures.”

Note: Positing WDM for fronthaul is nothing new. In fact, many think it’s essential for C-RAN economics. For example, this post imagines you are connecting 3 RRHs  in a network with two bands. In this case each (20MHz, 2×2) RRH will require the CPRI capacity of 2.4576 Gbps. Multiply that by three RRHs and then by two bands and you are looking at 14.7456Gbps. If each RRH uses one fibre link, each cell site would need six links, but with WDM equipment installed between the BBU in and RRHs, you can provide CPRI service over just one fibre connection.

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