SAN JOSE — Electronic and optical components are destined to merge, but the annual OFC event revived the debate over whether silicon photonics (SiP) or indium phosphide (InP) is the best path.
An academic researcher helping to develop a foundry ecosystem for photonics in Europe made the case for InP in a keynote. But several analysts said that SiP will more likely be the winner.
All sides agree that rising needs for more bandwidth will drive to new optoelectronic interfaces within the next five years. They could be needed as soon as two generations after the 400G systems that were widely shown on the OFC show floor this year and are expected to ship in volume by 2019.
The 25.6-Tbits/s switch chips emerging around 2020 will need optical interfaces, authors of a book on silicon photonics predicted last year. On-board optics may be required as early as 2021, said networking veteran, Andreas Bechtolshiem , in a recent talk calling for an 800G Ethernet standard, perhaps the last to use discrete optical modules.
InP is a superior technology for the integration, especially for the core laser light source, but it needs to embrace high-volume silicon techniques to lower costs to the level of SiP, said Meint K. Smit in an OFC keynote.
Smit, an InP expert at Eindhoven University of Technology, is leading a European program that has made 350 InP devices to date. They include commercial products from multiple companies, such as 180- and 320-Gbit/s wavelength-division multiplexing transmitters.
The program brings together foundries, tool makers and photonics designers. It has created validated libraries of optical components and InP process design kits, enabling test devices on multi-project wafers — and it is pushing for a move from 4- to 6-in. wafers.
However, Smit admits that SiP has lower costs given supporters such as Intel with access to large 8-in. wafer fabs. “It’s a complex picture, and there’s no single solution for all … [In the end], InP with silicon electronics and SiP may work together,” he said.
Smit showed stats (above) from one market watcher, predicting that InP volumes will outpace SiP, but other analysts disagreed.
“The leading companies — Luxtera, Intel, Mellanox, and Cisco — are all on SiP, so there is a lot more money going into SiP than InP,” said Jag Bolaria, a senior analyst with the Linley Group.
Last year, Intel announced its first 100-Gbit/s SiP transceivers after more than a decade of lab work. Equipment makers Ciena and Juniper Networks made acquisitions to bring silicon photonics know-how in-house, and Acacia Communications, a maker of coherent transceivers based on silicon photonics, had a successful IPO.
By contrast, Smart Photonics in Eindhoven is showing some good links between InP process design rules and EDA with its partner, Phoenix Software, said Loring Wirbel, another Linley analyst and longtime comms expert. “InP has its role, for example, in placement of DWDM modulators and photodetectors, but there's no wholesale replacement of InP for SiP going on.”
In a sign of the diverse paths to photonics, he noted a research paper from Luxtera on a single chip made in a Globalfoundries 45-nm Silicon-on-Insulator CMOS process packing a RISC V core and 800 optical devices.
Overall, much of the focus at this year’s OFC was on relatively short-reach optics using 56G serdes to drive 200- and 400-Gbit Ethernet systems for big data centers, Wirbel said. “The show seemed lively, given the sagging state of many end markets … long-haul and undersea markets are flat,” he added.
In another keynote, a Google executive called for 10x improvements in capacity and 2x reductions in cost to server data centers in which bandwidth requirements are doubling nearly every two years. Nevertheless, many companies in the sector are reporting mid-single-digit growth rates.
Data centers and service providers still have widely varying requirements in optical networks, said Loudon Blair, a senior director of corporate strategy at long-haul specialist, Ciena. Blair, who also chairs the OFC steering committee, said that programmability is one rising theme at the event.
“The conference is upbeat, optimistic, with probably a higher turnout than in recent years,” he said. “We’re hearing more about smarter devices controlled by software, APIs, software-defined networks, open-source, and even big-data analytics over optical networks.”
— Rick Merritt, Silicon Valley Bureau Chief, EE Times
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