In booth 1127 at OFC/NFOEC 2013 in Anaheim, CA, USA (19-21 March), OneChip Photonics Inc of Ottawa, Canada, which designs optical chips and transceivers based on monolithic photonic integrated circuits (PICs) fabricated in indium phosphide (InP), has announced a family of PIC-based 100Gbps optical interconnect solutions, enabling transceiver makers to produce high-speed, low-power and small-size modules for data-center interconnect (DCI) applications.
The new family builds on the PIC-based receiver chips that OneChip announced, and made available for partner testing, in May 2012.
OneChip says that its fully integrated 100Gbps solutions provide advantages over solutions based on silicon photonics, discrete components and vertical-cavity surface-emitting lasers (VCSELs).
“OneChip can provide transceiver and system manufacturers with the integrated solutions that they need to meet their cost, power, size and speed requirements, without all of the problems inherent with silicon photonics solutions,” says CEO Jim Hjartarson.
“Integration of optics and electronics on one chip holds strong promise for providing low-power, cost-effective 100Gbps interface modules for data-center applications,” comments Vladimir Kozlov, founder & CEO of optical communications market research firm LightCounting. “These attributes will be important in this high-volume market. In fact, this market is only going to be high volume if low-power and low-cost products are available,” he adds.
According to LightCounting, 100 Gigabit Ethernet transceiver sales are expected to rise at a compound annual growth rate (CAGR) of 36% from $144m in 2012 to almost $700m in 2017.
Integrated solutions needed to meet cost, power & size requirements in data center
System integrators want to drive costs down to the point where 100Gbps solutions are as cost-effective to implement as 10Gbps solutions are currently, says OneChip. At the moment, 100GBASE-LR4 implementations are far too expensive to be useful in data-center interconnect applications.
Further, transceiver providers want to fit 100Gbps solutions into QSFP (quad small-form-factor pluggable) modules, as QSFPs represent the smallest form factor for packaged transceivers, but they must dissipate only 3.5W of power or less.
The only way to meet the cost, power and size requirements, for DCI applications, is through tightly integrated chipsets and sub-assemblies, says OneChip.
OneChip monolithically integrates all of the optical functions required for an optical transceiver into a single InP-based chip. All of the chip’s active components - distributed feedback (DFB) laser, electro-absorption modulator (EAM), and waveguide photodetector (WPD) - and passive components - including wavelength-division multiplexing (WDM) combiner, splitter and spot-size converter (SSC) - are, uniquely, integrated in one epitaxial growth step - without re-growth or post-growth modification of the epitaxial material.
OneChip claims that these Multi-Guide Vertical Integration (MGVI)-based PICs enable numerous cost, power and size advantages over competing solutions based on silicon photonics, discrete components and VCSELs.
OneChip’s PIC-based 100G solutions vs silicon photonics, discrete components and VCSELs
Because silicon cannot lase or detect in the required spectral range (1300nm), silicon photonics providers must add materials that can, for example, bond III-V semiconductors (for lasing) or epitaxially overgrow germanium (for detection) on top of silicon.
Thus, silicon photonics chips cannot be manufactured simply by using standard CMOS (complementary metal oxide semiconductor) materials and processes, OneChip says. This also makes adding photonics capability to advanced sub-micron silicon process nodes cost prohibitive, it adds. These drawbacks prevent silicon photonics solutions from achieving the cost and size requirements - and the ability to manufacture in volume through standard electronics foundries – that are needed in data-center interconnect applications, the firm reckons.
In contrast, OneChip’s single-growth MGVI platform eliminates the need for multiple epitaxial regrowth steps, in which material from the previous growth step(s) that is selectively etched out must be replaced with another material regrowth step(s). OneChip can hence partner with standard, high-volume InP electronics foundries to fabricate its PIC-based solutions, improving economies of scale. Simultaneously with the new product launch, OneChip has also announced foundry relationships with IQE and Global Communication Semiconductors (GCS).
Further, OneChip says that its MGVI platform in InP is based on the same process that inherently produces the best and fastest heterojunction bipolar transistors (HBTs) used in radio-frequency integrated circuits (RFICs). It can hence also integrate electronics, such as transimpedance amplifiers (TIAs) and modulator drivers, within a commercially available and volume-scalable process. The aim of silicon photonics to leverage high-volume electronic chip production, while combining photonics and electronics on the same substrate, is ironically best realized in InP, the firm reckons.
These advantages also hold true when comparing OneChip’s 100Gbps solutions with solutions based on discrete components and VCSELs, it adds.
For example, the drawbacks of VCSEL-based solutions are that they cannot accommodate wavelength-division multiplexing (WDM), are difficult to couple with single-mode fibers, and become expensive when made to address long-wavelength interconnect applications, says OneChip.
The firm’s InP-based PIC technology enables it to multiplex multiple lasers together and produce chip and module solutions that support standard communications wavelengths – e.g in the 1310nm window - cost effectively.
OneChip says that its regrowth-free, PIC-based InP technology has proven successful in the cost-sensitive, high-volume PON market, as its PIC-based PON transceivers and bi-directional optical sub-assemblies (BOSAs) are already being deployed by the world’s largest PON system providers.
Now, OneChip is extending this technology to the high-volume DCI market, which requires 100Gbps+ solutions with higher interface density and longer reach than those within the reach of currently deployed systems in 0.85μm and multi-mode fibers. The DCI market also requires lower cost and power consumption than the solutions offered by the traditional telecom component vendors.
OneChip says that it is currently working with partners to optimally package its 100G and 40G PICs for specific applications.
The firm is also developing PIC-based 100GE PSM4 TROSAs (transmitter-receiver optical sub-assemblies) for DCI applications.
