LightCounting, a market research institute in the optical communications industry, recently released its latest report: Priorities of Service Providers for DWDM Networks of the Future. After conducting more than 20 interviews with leading telecom operators and cloud computing companies in Europe, Japan, North America and China over the past six months, LightCounting believes that WDM networks will trend towards higher data transmission rates, wider spectrums, and more flexibility and automation. It also predicts that backbone networks and metro networks will be upgraded to 400G, and 100G/200G and OXC/ROADM will be widely deployed on metro access networks. LightCounting further highlights that the IP over DWDM solution using 400G ZR/ZR+ still faces many challenges in operator scenarios.

With the large-scale deployment of FTTx and 5G, operators need to continuously upgrade WDM transmission systems to cope with traffic growth. In the next three to five years, FTTx networks will be upgraded from 10G PON to 50G PON, and 5G bearer networks will be upgraded from 10G to 100G. Network traffic is also becoming more localized. According to operator statistics, 90% of network traffic does not reach the backbone network, and traffic is growing faster on the metro network than on the backbone network. LightCounting predicts that the annual growth rate of metro network traffic is between 25% and 40%, while that of long-haul backbone networks is only between 5% and 15%. Therefore, operators prefer investing in the WDM systems of metro and access networks.

LightCounting believes that single-wavelength acceleration can effectively reduce per-bit costs and power consumption. In metro access networks, 100G/200G will replace 10G as the mainstream rate. Metro core and long-haul backbone networks will be upgraded to 400G. However, the demand for 100G/200G ports will continue over the next five years. The latest 400G modulators and receivers will work at a baud rate of 130G, which requires WDM transmission systems to provide a wider spectrum. And in order to do that, we must use a WDM system with flexible grid channel spacing and extend the available spectrum of fibers to the L band.

In addition, the cost of adding optical fibers to the backbone network is high, and it is easier to deploy optical fibers on the metro network and access network. Therefore, the future evolution directions of the two types of WDM networks are quite different. LightCounting believes that metro and access WDM systems will remain in the C band and reduce per-bit costs and power consumption by using simple pluggable optical modules. Backbone WDM networks will continue to use built-in unpluggable high-speed optical modules on boards, and extend the available spectrum of optical fibers to the C+L band and even to the S band in the future.

Currently, operators’ metro WDM networks mainly use ring and mesh topologies, the complexity of these networks will increase significantly over the next five years. According to LightCounting, deploying ROADM can greatly improve the flexibility of WDM networks, while the deployment of OXC would act as a fortifier. OXC can combine all functions of ROADM with the optical backplane, greatly simplifying fiber connections between ROADM boards and strengthening network automation. In addition, because OXC and ROADM can keep network traffic transmitted and switched in the optical network, a large number of optical-to-electrical conversion components are not required. In this way, device costs, power consumption, and network latency can be reduced. Decreasing latency is especially important for metro networks because metro networks connect cloud data centers with end users. Reducing network latency can improve the end user experience.

According to LightCounting’s survey results, there has been a trend of deploying ROADM on entire networks. Verizon is one of the first operators to deploy ROADM on metro networks. Therefore, optical communication technology vendors and device vendors should also keep up with the trend. For example, Huawei recently launched a new metro WDM solution, which uses OXC, and is specially designed for metro networks and access networks. OXC is developed based on a chip-level integrated optical device, which can reduce product costs while still maintaining functionality. OXC can significantly reduce the connection latency between end users and cloud data centers, and makes one-hop to the cloud possible.

LightCounting also analyzed the technical features, advantages, and disadvantages of 400G ZR/ZR+ and IP over DWDM. LightCounting pointed out that 400G ZR/ZR+ is only a standard for 400G coherent modules and is generally used in short-distance interconnection scenarios of large cloud data centers such as Google, Meta, and Microsoft. However, there are still many challenges in applying 400G ZR/ZR+ modules to operators’ IP over DWDM scenarios, such as optical-layer network management and higher power consumption. In addition, 400G ZR/ZR+ modules have limitations on heat dissipation and optical performance. The higher the module rate, the higher the power consumption of the analog chips used by the module, including the oDSP SerDes, modulator, driver, and coherent receiver. Therefore, for operators, it is still uncertain as to whether such modules will see a smooth evolution to 800G and 1.6T in the future.

In the report, LightCounting also revealed its talks with British Telecom (BT). BT believes that the IP over DWDM solution using ZR/ZR+ is favorable only in router hop-by-hop networking, however, the cost of this networking is much higher than that of the ROADM optical-layer one-hop networking as traffic grows. After ROADM is introduced, traditional 400G transponders have more advantages than 400G IP over DWDM. Therefore, ROADM+traditional 400G transponders will still be the first choice for operators. BT believes that in the IP over DWDM solution, adding more routers is the most expensive part of network upgrades and expanding the optical layer is often the most cost-effective solution for enabling new services.

For more details on the LightCounting report, visit https://www.lightcounting.com/resource/29/resourceFile/Priorities %20of %20Service %20Providers %20for %20DWDM %20Networks %20of %20the %20Future.pdf