Marvell kickstarts the 800G coherent pluggable era

Marvell has become the first company to provide an 800-gigabit coherent digital signal processor (DSP) for use in pluggable optical modules.

The 5nm CMOS Orion chip supports a symbol rate of over 130 gigabaud (GBd), more than double that of the coherent DSPs for the OIF's 400ZR standard and 400ZR+.

Meanwhile, a CFP2-DCO pluggable module using the Orion can transmit a 400-gigabit data payload over 2,000km using the quadrature phase-shift keying (QPSK) modulation scheme.

The Orion DSP announcement is timely, given how this year will be the first when coherent pluggables exceed embedded coherent module port shipments.

This is the year coherent pluggable modules exceed embedded coherent port shipments. Source: LightCounting

"We strongly believe that pluggable coherent modules will cover most network use cases, including carrier and cloud data centre interconnect," says Samuel Liu, senior director of coherent DSP marketing at Marvell.

Marvell also announced its third-generation ColorZ pluggable module for hyperscalers to link equipment between data centres. The Orion-based ColorZ 800-gigabit module supports the OIF's 800ZR standard and 800ZR+.

Fifth-generation DSP

The Orion chip is a fifth-generation design yet Marvell's first. First ClariPhy and then Inphi developed the previous four generations.

A decade of progress. Source: Marvell, Gazettabyte

Inphi bought ClariPhy for $275 million in 2016, gaining the first two generation devices: the 40nm CMOS 40-gigabit LightSpeed chip and a 28nm CMOS 100- and 200-gigabit Lightspeed-II coherent DSP products. The 28nm CMOS DSP is now coming to the end of its life, says Liu.

Inphi added two more coherent DSPs before Marvell bought the company in 2021 for $10 billion. Inphi's first DSP was the 16nm CMOS M200. Until then, Acacia (now Cisco-owned) had been the sole merchant company supplying coherent DSPs for CFP2-DCOs pluggable modules.

Inphi then delivered the 7nm 400-gigabit Canopus for the 400ZR market, followed a year later by the Deneb DSP that supports several 400-gigabit standards. These include 400ZR, 400ZR+, and standards such as OpenZR+, which also has 100-, 200-, and 300-gigabit line rates and supports the OpenROADM MSA specifications. "The cash cow [for Marvell] is [the] 7nm [DSPs]," says Liu.

The Inphi team's first task after the acquisition was to convince Marvell's CEO and its chief financial officer to make the most significant investment in a coherent DSP. Developing Orion cost between $100M-300M.

"We have been quiet for the last two years, not making any coherent DSP announcements," says Liu. "This [the Orion] is the one."

Marvell views being first to market with a 130GBd-plus generation coherent DSP as critical given how pluggables, including the QSFP-DD and the OSFP form factors, account for over half of all coherent ports shipped.

"It is very significant to be first to market with an 800ZR plug and DSP," says Jimmy Yu, vice president at market research firm Dell'Oro Group. "I expect Cisco/Acacia to have one available in 2024. So, for now, Marvell is the only supplier of this product."

Yu notes that vendors such as Ciena and Infinera have had 800 Gigabit-per-second (Gbps) coherent available for some time, but they are for metro and long-haul networks and use embedded line cards.

Use cases

The Orion DSP addresses hyperscalers' and telecom operators' coherent needs. The DSP also implements various coherent standards to ensure that the vendors' pluggable modules work with each other.

Liu says a DSP's highest speed is what always gets the focus, but the Orion also supports lower line rates such as 600, 400 and 200Gbps for longer spans.

The baud rate, modulation scheme, and the probabilistic constellation shaping (PCS) technique are control levers that can be varied depending on the application. For example, 800ZR uses a symbol rate of only 118GBd and the 16-QAM modulation scheme to achieve the 120km specification while minimising power consumption. When performance is essential, such as sending 400Gbps over 2,000km, the highest baud rate of 130GBd is used along with QPSK modulation.

Source: Marvell

China is one market where Marvell's current 7nm CFP2-DCOs are used to transport wavelengths at 100Gbps and 200Gbps.

Using the Orion for 200-gigabit wavelengths delivers an extra 1dB (decibel) of optical signal-to-noise ratio performance. The additional 1dB benefits the end user, says Liu: they can increase the engineering margin or extend the transmission distance. Meanwhile, probabilistic constellation shaping is used when spectral efficiency is essential, such as fitting a transmission within a 100GHz-width channel.

Liu notes that the leading Chinese telecom operators are open to using coherent pluggables to help reduce costs. In contrast, large telcos in North America and Europe use pluggables for their regional networks. Still, they prefer embedded coherent modems from leading systems vendors for long-haul distances greater than 1,000km.

Marvell believes the optical performance enabled by its 130GBd-plus 800-gigabit pluggable module will change this. However, all the leading system vendors have all announced their latest generation embedded coherent modems with baud rates of 130GBd to 150GBd, while Ciena's 200GBd 1.6-terabit WaveLogic 6 coherent modem will be available next year.

The advent of 800-gigabit coherent will also promote IP over DWDM. 400ZR+ is already enabling the addition of coherent modules directly to IP routers for metro and metro regional applications. An 800ZR and 800ZR+ in a pluggable module will continue this trend beyond 400 gigabit to 800 gigabits.

The advent of an 800-gigabit pluggable also benefits the hyperscalers as they upgrade their data centre switches from 12.8 terabits to 25.6 and 51.2 terabits. The hyperscalers already use 400ZR and ZR+ modules, and 800-gigabit modules, which is the next obvious step. Liu says this will serve the market for the next four years.

Fujitsu Optical Components, InnoLight, and Lumentum are three module makers that all endorsed the Orion DSP announcement.

ColorZ 800 module 

In addition to selling its coherent DSPs to pluggable module and equipment makers, Marvell will sell to the hyperscalers its latest ColorZ module for data centre interconnect.

Marvell's first-generation product was the 100-gigabit coherent ColorZ in 2016 and in 2021 it produced its 400ZR ColorZ. Now, it is offering an 800-gigabit version - ColorZ 800 - to address 800ZR and 800ZR+, which include OpenZR+ and support for lower speeds that extend the reach to metro regional and beyond.

Functional blocks of a coherent module using the Orion DSP. Source: Marvell

"We are first to market on this module, and it is now sampling," says Josef Berger, associate vice president of marketing optics at Marvell.

Marvell addressing its module for the hyperscaler market rather than telecoms makes sense, says Yu, as it is the most significant opportunity.

"Most communications service providers' interest is in having optical plugs with longer reach performance," says Dell'Oro's Yu. "So, they are more interested in ZR+ optical variants with high launch power of 0dBm or greater."

Marvell notes a 30 per cent cost and power consumption reduction for each generation of ColorZ pluggable coherent module.

Liu concludes by saying that designing the Orion DSP was challenging. It is a highly complicated chip comprising over a billion logic gates. An early test chip of the Orion was used as part of a Lumentum demonstration at the OFC show in March.

The ColorZ 800 module will start being sampled this quarter.

What follows the Orion will likely be a 1.6-terabit DSP operating at 240GBd. The OIF has already begun defining the next 1.6T ZR standard.