Coherent pluggable optics at 400G and beyond bring new cost and performance benefits to network operators and introduce a host of new options for network architectures and applications. But there is a lot to plan for and consider. Decisions must be made on data rates, form factors and power profiles. Architecture decisions must also be made: Adopt integrated optics in routers (IP over DWDM) or stick with separate DWDM and IP layers? Within DWDM systems, should operators go with pluggable or embedded optics?

To understand the future of high speed coherent optics, Heavy Reading launched the Coherent Optics Market Leadership Program with industry partners Ciena, Effect Photonics, Infinera and Ribbon. The 2022 project was based on a global network operator survey, conducted in August, that attracted 87 qualified responses.

This is the second installment of four blogs highlighting the key findings from the 2022 Coherent Optics Survey. It focuses on metro architectures and applications as the coherent pluggable era begins.

Integration and separation

400G+ coherent optics include embedded and pluggable forms and can be used across multiple system types, such as in traditional DWDM systems or integrated directly into switches/routers. Historically, this has been called IPoDWDM. More recently, suppliers have been using other terms, including routed optical networking and coherent routing. Looking to 2024, in aggregate, the survey data shows 61% deployed in traditional DWDM versus 39% integrated into switches/routers. Within DWDM systems, operators expect an even mix of 400G+ in metro and regional/long-haul.

Given the early stage of the market evolution and the telecom audience surveyed (as opposed to hyperscalers), the results are a strong endorsement for IPoDWDM. Expectations may prove too optimistic, but the intentions of network operators cannot be ignored. Colt Technology Services, Arelion (formerly Telia Carrier) and Windstream are three significant operators that are early public champions of the architecture, but nearly every operator Heavy Reading speaks with is investigating IPoDWDM at some level.

Figure 1: By the end of 2024, how do you see the distribution of 400G+ coherent optics in your network for various applications? n=80
Source: Heavy Reading, 2022

A broad role for coherent pluggables

Pluggable coherent optics are a prerequisite for IPoDWDM at 400G. It is sometimes overlooked that 400G+ coherent pluggables are not limited to IPoDWDM but are also important to traditional DWDM systems. On average, operators surveyed expect 400G+ coherent pluggable optics to account for the majority of optics in DWDM systems by the end of 2024. The survey data shows a relative split of 58%/42%, favoring coherent pluggables over embedded (proprietary) optics. For all but the highest performance of applications, the future of optics is becoming pluggable, and it includes multi-vendor interoperability.

Figure 2: By the end of 2024, how do you see the relative use of 400G+ coherent optics used in DWDM systems? n=78
Source: Heavy Reading, 2022

Paying for performance

Compared to coherent pluggables, embedded optics provide higher performance, including greater reach and higher spectral efficiency. For this reason, long-haul networks will be based almost exclusively on embedded optics for the foreseeable future. But embedded optics will continue to play a significant role in metro networks as well, even as pluggable optics gain share (as evidenced by the mix in the above figure).

Higher performance does not come free. For any given data rate, embedded optics are more costly than their pluggable counterparts. As noted, in long-haul networks, embedded optics are the only option. But in most metro applications, operators will have a choice between the two. A key question is: How much of a premium are operators willing to pay for the added performance of embedded optics in the metro?

Heavy Reading survey data indicates that a majority of operators are willing to pay a cost premium of up to 20% for embedded optics performance. Specifically, 45% of respondents identify a 10–20% premium as reasonable, and 18% expect a premium of less than 10%.

Figure 3: For DWDM systems in metro applications, what premium is acceptable for solutions that use embedded optics to maximize spectral efficiency versus pluggable optics? n=87
Source: Heavy Reading, 2022

Coherent pluggable optics are set to make a significant mark on metro optical networks as an enabler of new IPoDWDM architectures and as an alternative to traditionally embedded optics in metro DWDM systems. As is typically the case in telecom, the future of optics is not one-size-fits-all, but rather, a mix of options. Traditional DWDM networks will be deployed even as IPoDWDM gains favor. Pluggable optics will proliferate, but embedded optics will continue to play an essential role for high performance applications, even in the metro.

Looking for more information?

Coherent Optics: 100G, 400G and Beyond

— Sterling Perrin, Senior Principal Analyst, Optical Networking & Transport, Heavy Reading

This blog is sponsored by Ribbon.