Lumentum's optical circuit switch for AI data centres

Part 3: Data Centre Switching

The resurgence of optical circuit switches for use in data centres is gaining momentum, driven by artificial intelligence (AI) workloads that require scalable connectivity.

Peter Roorda

Lumentum is one of several companies that showcased an optical circuit switch at the OFC event in San Francisco in March.

Lumentum's R300 switch connects optically the 300 input ports to any of the 300 output ports. The optical circuit switch uses micro-electro-mechanical systems (MEMS), tiny mirrors that move electrostatically, to direct light from an input port to one of the 300 output ports.

The R300 addresses the network needs of AI data centres, helping link large numbers of AI accelerator chips such as graphics processor units (GPUs).

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Tomahawk 6: The industry’s first 100-terabit switch chip

Part 2: Data Centre Switching

Peter Del Vecchio, product manager for the Tomahawk switch family at Broadcom, outlines the role of the company’s latest Tomahawk 6 Ethernet switch chip in AI data centres.

Peter Del Vecchio

Broadcom is now shipping samples of its Tomahawk 6, the industry’s first 102.4-terabit-per-second (Tbps) Ethernet switch chip.

The chip highlights AI's impact on Ethernet networking switch chip design since Broadcom launched its current leading device, the 51.2-terabit Tomahawk 5.

The Tomahawk 6 is more evolutionary, rather than a complete change, notes Del Vecchio.

The design doubles bandwidth and includes enhanced networking features to support AI scale-up and scale-out networks.

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OFC 2025: industry reflections

Gazettabyte is asking industry figures for their thoughts after attending the recent 50th-anniversary OFC show in San Francisco. Here are the first contributions from Huawei’s Maxim Kuschnerov, NLM Photonics' Brad Booth, LightCounting’s Vladimir Kozlov, and Jürgen Hatheier, Chief Technology Officer, International, at Ciena.

Source: Shutterstock

Maxim Kuschnerov, Director of R&D, Huawei

The excitement of last year's Nvidia’s Blackwell graphics processing unit (GPU) announcement has worn off, and there was a slight hangover at OFC from the market frenzy then.

The 224 gigabit-per-second (Gbps) opto-electronic signalling is reaching mainstream in the data centre. The last remaining question is how far VCSELs will go—30 m or perhaps even further. The clear focus of classical Ethernet data centre optics for scale-out architectures is on the step to 448Gbps-per-lane signalling, and it was great to see many feasibility demonstrations of optical signalling showing that PAM-4 and PAM-6 modulation schemes will be doable.

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OFC 2025: reflecting on the busiest optics show in years

Adtran's Gareth Spence interviews Omdia's Daryl Inniss (left) and the editor of Gazettabyte, live from the conference hall at OFC 2025. 

The discussion covers the hot topics of the show and where the industry is headed next. Click here.

Nokia picks Infinera to boost its optical networking arm

Nokia has announced its intention to buy optical networking specialist Infinera for $2.3 billion. 

The motivation for the Infinera acquisition is scale, said Nokia CEO Pekka Lundmark, during an analyst call detailing the announcement. 

Jimmy Yu, Dell'Oro Group

Optical networking is how communications service providers and hyperscalers cope with the exponential traffic growth. 

Continual innovation is required to reduce the cost and power consumed to transport such traffic. For a systems vendor, having scale helps meet these aims.

Optical networking wasn't always central to Nokia's strategy. In 2013, Nokia sold its optical networking arm to Marlin Equity Partners, which became Coriant.

Now, Nokia wants to be a leading optical networking vendor by acquiring Infinera, a company that bought Coriant in 2018.   

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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.

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Taking a unique angle to platform design

• A novel design based on a vertical line card shortens the trace length between an ASIC and pluggable modules.
• Reducing the trace length improves signal integrity while maintaining the merits of using pluggables.
• Using the vertical line card design will extend for at least two more generations the use of pluggables with Ethernet switches.

The travelling salesperson problem involves working out the shortest route on a round-trip to multiple cities. It's a well-known complex optimisation problem.

Chris Cole

Systems engineers face their own complex optimisation problem just sending an electrical signal between two points, connecting an Ethernet switch chip to a pluggable optical module, for example.

Sending the high-speed signal over the link with sufficient fidelity for its recovery requires considerable electronic engineering design skills. And with each generation of electrical signalling, link distances are getting shorter.

In a paper presented at the recent ECOC show, held in Basel, consultant Chris Cole, working with Yamaichi Electronics, outlined a novel design that shortens the distance between an Ethernet switch chip and the front-panel optics.

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