Nokia today announced its fifth-generation WaveFabric Elements optical portfolio, which is capable of 400 Gb/s line speeds. While the company's competition — namely Ciena, Infinera, and Huawei — already announced, trialed, and in some cases even deployed 800 Gb/s optics, Nokia is doubling down on 400 Gb/s line speeds.

Kyle Hollasch, director of product marketing for Nokia's optical networking division, argues that 400 Gb/s optics are the sweet spot because they can be deployed practically anywhere in the network and still deliver near-peak performance regardless of whether they are used for long-haul, metro, or data center interconnect.

"It's not about having the most powerful, awesome [digital signal processor], it's about having DSPs that are tailored to the application at hand," he said. Hollasch added that while Nokia certainly could have done 800 Gb/s optics, the market simply isn't ready for it.

Nokia's latest generation of WaveFabric Elements includes two DSPs, the high-performance "super-coherent" PSE-Vs, and the "compact" low-power PSE-Vc.

The PSE-Vs DSP boasts support for 90-gigabaud transmission, thus allowing for 60% greater reach and 40% lower power consumption for an overall 15% improvement in spectral efficiency over the previous generation.

Meanwhile, Nokia's smaller PSE-Vc is can be tuned from 100 Gb/s to 400 Gb/s depending on the distance required. The lower the line rate, the farther the transmission can be spent.

The new DSPs pair with the Coherent Silicon Transmit and Receive (CSTAR) portfolio of silicon photonics chips, which Nokia acquired with the purchase of Elenion Technologies earlier this year.

Elenion Technologies "are experts in silicon photonics technology as applied to optical front ends or modulators," said Hollasch, adding that these modulators are essentially the engines of the transceivers.

Both Nokia's new DSPs and optical engine will be available in the 400G QSFP-DD pluggable form factor, which is popular for use in data center interconnect applications, as well as in the larger, CFP2-DCO form factor commonly used for multi-haul.

Nokia's fifth-generation DSPs will begin shipping in the fourth quarter of 2020, while the company's CSTAR silicon photonics chips already shipping to industry partners.

The launch comes at a time when Nokia's competition in the optical space has moved well beyond 400 Gb/s optics to 600 Gb/s and even 800 Gb/s offerings.

Ciena announced the availability of its own 800 Gb/s-capable transceiver, WaveLogic 5 Extreme, in early March. That same month, Infinera announced the successful trial of an 800 Gb/s single-wave transmission over a 950-kilometer production network.