OneChip Photonics targets the data centre with its PICs
OneChip Photonics is developing integrated optical components for the IEEE 40GBASE-LR4 and 100GBASE-LR4 interface standards.
The company believes its photonic integrated circuits (PICs) will more than halve the cost of the 40 and 100 Gigabit 10km-reach interfaces, enough for LR4 to cost-competitively address shorter reach applications in the data centre.
"I think we can cut the price [of LR4 modules] by half or better”
Andy Weirich, OneChip Photonics
The products mark an expansion of the Canadian startup's offerings. Until now OneChip has concentrated on bringing PIC-based passive optical network (PON) transceivers to market.
LR4 PICs
The startup is developing separate LR4 transmitter and receiver PICs. The 40 and 100GBASE-LR4 receivers are due in the third quarter of 2012, while the transmitters are expected by the year end.
The 40GBASE-LR4 receiver comprises a wavelength demultiplexer - a 4-channel arrayed waveguide grating (AWG) - and four photo-detectors operating around 1300nm. A spot-size converter - an integrated lens - couples the receiver's waveguide's mode field to the connecting fibre.
"[Data centre operators] are saying that they are having to significantly bend out of shape their data centre architecture to accommodate even 300m reaches”
The 40GBASE-LR4 transmitter PIC comprises four directly-modulated distributed feedback (DFB) lasers while the 100GBASE-LR4 use four electro-absorption modulator DFB lasers. Different lasers for the two PICs are required since the four wavelengths at 100 Gig, also around 1300nm, are more tightly spaced: 5nm versus 20nm. "They are much closer together than the 40 Gig version,” says Andy Weirich, OneChip Photonics' vice president of product line management.
Another consequence of the wider wavelength spacings is that the 40 Gig transmitter uses four discrete lasers. “Because the 40 Gig wavelengths are much further apart, putting all the lasers on the one die is problematic," says Weirich. The 40GBASE-LR4 design thus uses five indium phosphide components: four lasers and the AWG, while the 40GBASE-LR4 receiver and the two 100GBASE-LR4 devices are all monolithic PICs.
Both LR4 transmitter designs also include monitor photo-diodes for laser control
Lower size and cost
OneChip says the resulting PICs are tiny, measuring less than 3mm in length. “We think the PICs will enable the packaging of LR4 in a QSFP,” says Weirich. 40GBASE-LR4 products already exists in the QSFP form factor but the 100GBASE-LR4 uses a CFP module.
The startup expects module makers to use its receiver chips once they become available rather than wait for the receiver-transmitter PIC pair. "Reducing the size of one half the solution is possibly good enough to fit the whole hybrid design - the PIC for the receive and discretes for the transmit - into a QSFP,” says Weirich.
The PICs are expected to reduce significantly the cost of LR4 modules. "I think we can cut the price by half or better,” says Weirich. “Right now the LR4 is far too expensive to be used for data centre interconnect.” OneChip expects its LR4 PICs to be cost-competitive with the 2km reach 10x10 MSA interface.
Meanwhile, short-reach 40 and 100 Gig interfaces use VCSEL technology and multi-mode fibre to address 100m reach requirements. In larger data centres this reach is limiting. Extended reach - 300-400m - multimode interfaces have emerged but so far these are at 40 Gig only.
"[Data centre operators] are saying that they are having to significantly bend out of shape their data centre architecture to accommodate even 300m reaches,” says Weirich. “They really want more than that.”
OneChip believes interfaces distances of 200m-2km is underserved and it is this market opportunity that it is seeking to address with its LR4 designs.
Roadmap
Will OneChip integrate the design further to product a single PIC LR4 transceiver?
"It can be put into one chip but it is not clear that there is an economic advantage,” says Weirich. Indeed one PIC might even be more costly than the two-PIC chipset.
Another factor is that at 100 Gig, the 25Gbps electronics present a considerable signal integrity design challenge. “It is very important to keep the electronics very close to the photo-detectors and the modulators,” he says. “That becomes more difficult if you put it all on the one chip.” The fabrication yield of a larger single PIC would also be reduced, impacting cost.
OneChip, meanwhile, has started limited production of its PON optical network unit (ONU) transceivers based on its EPON and GPON PICs. The company's EPON transceivers are becoming generally available while the GPON transceivers are due in two months’ time.
The company has yet to decide whether it will make its own LR4 optical modules. For now OneChip is solely an LR4 component supplier.
Further reading:
See OFC/ NFOEC 2012 highlights, the Kotura story in the Optical Engines section
Photonic integration specialist OneChip tackles PON
Briefing: PON
Part 1: Monolithic integrated transceivers
OneChip Photonics is moving to volume production of PON transceivers based on its photonic integrated circuit (PIC) design. The company believes that its transceivers can achieve a 20% price advantage.
"We will be able to sell [our integrated PON transceivers] at a 20% price differential when we reach high volumes"
Andy Weirich, OneChip Photonics
OneChip Photonics has already provided transceiver engineering samples to prospective customers and will start the qualification process with some customers this month. It expects to start delivering limited quantities of its optical transceivers in the next quarter.
The company's primary products are Ethernet PON (EPON) and Gigabit PON (GPON) transceivers. But it is also considering selling a bi-directional optical sub-assembly (BOSA), a component of its transceivers, to those system providers that want to attach the BOSA directly to the printed circuit board (PCB) in their optical network units (ONUs).
"The BOSA is the sub-assembly that contains all the optics, usually the TIA [trans-impedance amplifier] and sometimes the laser driver," says Andy Weirich, OneChip Photonics' vice president of product line management.
The company will roll out its Ethernet PON (EPON) ONU transceivers in the second quarter of 2012, followed by GPON ONU transceivers in the third quarter.
PON Technologies
EPON operates at 1.25 Gigabit-per-second (Gbps) upstream and downstream. OneChip had planned to develop a 2.5Gbps EPON variant which, says OneChip, has been standardised by the China Communications Standards Association (CCSA). But the company has abandoned the design since volumes have been extremely small and there have been no deployments in China.
GPON is a 2.5Gbps downstream/ 1.25Gbps upstream technology. The main differences between GPON and EPON transceiver optical components are the requirement of the ONU's receiver optics and circuitry, and the laser type, says Weirich. GPON's Class B+ specification, used for nearly all the GPON deployments, calls for a 28-29dB sensitivity. This is a more demanding specification requirement to meet than EPON's. GPON also calls for a Distributed Feedback (DFB) laser, whereas an EPON ONU may use either a Fabry-Perot laser or a DFB laser.
OneChip uses the same DFB for GPON and EPON ONUs. Where the PIC designs differ is the receiver assembly where GPON requires amplification. This, says Weirich, is achieved using either an avalanche photodiode (APD) or a semiconductor optical amplifier (SOA).
OneChip will start with an APD but will progress to an SOA. Once it integrates an SOA as part of the PIC, a simpler, cheaper photo-detector can be used.
Weirich admits that it has taken OneChip longer than it expected to develop its monolithically-integrated design.
Part of the challenge has been the issue of packaging the PIC. "Because of our integrated approach and non-alignment-requiring assembly, we have had to solve a few more technology problems," he says. "Our suppliers have had a challenge with some of those issues, and it has taken a couple of iterations to solve."
OneChip says that the good news is that the price erosion of EPON transceivers has slowed down in the last two years. So while Weirich admits the market is more competitive now, what is promising is that volumes have continued to grow.
"There is no sign of saturation happening either in the EPON or GPON markets," he says. And OneChip believes it can compete on price. "What we are saying is that we will be able to sell [our monolithically integrated PON transceivers) at a 20% price differential when we reach high volumes." That is because the monolithic design is simpler and the optical components that make up the design are cheaper, says the company.
10G EPON and XGPON
OneChip believes the end of 2012 will be when 10G EPON volumes start to ramp. "10G EPON is a significantly larger market than 10G GPON [XGPON]," says Weirich, pointing out that some of the largest operators such as China Telecom have backed 10G EPON.
With 10G EPON there are two flavours: the asymmetric (10Gbps downstream and 1.25Gbps upstream) and the symmetric (10Gbps bidirectional) versions.
For an asymmetric 10Gbps ONU transceiver, the laser does not need to change but the optics and electronics at the receiver do, because of the 10Gbps receive signal and because operators want 28-29dB optical link budgets so that 10G EPON can run on the same fibre plant as EPON. "This is an order of magnitude more difficult from a sensitivity perspective than for EPON," says Weirich.
There is demand for the 10G symmetric EPON but it is much lower than the asymmetric version primarily due to cost. "The ONU transceiver with its 10 Gbps laser and photo-detector is quite a bit more costly," says Weirich, complicating the PON's business case.
OneChip says it has a 10G EPON in its product roadmap, but it has not yet made any announcements or made any demonstrations to customers.
Challenges
OneChip is not aware of any other company developing a monolithic integrated design for PON transceivers, in part due to the challenge. It has to be made cheaply enough to compete with the traditional TO-can design. The key is to develop low-cost integration techniques and processes right at the start of the PIC design, he says.
The company says that it is also exploring using its PIC technology to address data centre connectivity.
OneChip Photonics at a glance
OneChip employs some 80 staff and is headquartered in Ottawa, Canada, where it has a 4,000 sq. ft. cleanroom. The start-up also has a regional office in Shenzhen, China which includes a test lab to serve regional customers.
The company is primarily a transceiver supplier and its main target customers are the tier-one system vendors that supply OLT and ONU equipment. "When you think of the big three players in China, Huawei, ZTE and Fiberhome would be among those we are targeting," says Steve Bauer, vice president of marketing and communications, as well as players such as Alcatel-Lucent and Motorola. As mentioned, the company is also considering selling its BOSA design to ONU makers.
In May 2011 the company received $18M in its latest round of funding. "We are transitioning from product development to becoming operationally ready to manufacture in volume," says Bauer.
Fabrinet and Sanmina-SCI are two contract manufacturers that the company is using for transceiver testing and assembly while it has partnerships with several other fabs for supply of wafers, wafer fabrication and silicon optical benches.
OneChip solution for Fibre-To-The-Home
Jim Hjartarson, CEO of OneChip PhotonicsAn interview with Jim Hjartarson, CEO of OneChip Photonics
Q. In March 2009, OneChip raised $19.5m. How difficult is it nowadays for an optical component firm to receive venture capital funding?
A. Clearly, the venture capital community, given the current macroeconomic environment, is being selective about the new investments it makes in the technology market in general, and photonics in particular. However, if you can demonstrate that you have a unique approach to a problem that has not yet been solved, and that there is a large, untapped market opportunity, VCs will be interested in your value proposition.
Q. What is it about your company's business plan that secured the investment?
A. We believe OneChip Photonics has three fundamental advantages that resulted in our securing our initial two rounds of funding, which totaled $19.5 million:
- A truly breakthrough approach and technology that will remove the cost and performance barriers that have been impeding the ubiquitous deployment of Fiber-to-the-Home (FTTH) and enable new business and consumer broadband applications.
- A large, untapped market opportunity. Ovum estimates that the FTTx optical transceiver market will grow from $387 million by the end of 2009 to $594 million by the end of 2013. OneChip also is poised to introduce photonics integration into other high-volume business and consumer markets, where our breakthrough photonic integrated circuit (PIC) technology can reduce costs and improve performance. These markets could be orders of magnitude larger than the FTTx optical transceiver market.
- A seasoned and successful management team. OneChip has attracted top talent – from industry leading companies such as MetroPhotonics, Bookham, Catena Networks, Fiberxon, Nortel and Teknovus – who have successful track records of designing, manufacturing, marketing and selling transceivers, PICs and mass-market broadband access solutions.
Q. The passive optical networking (PON) transceiver market faces considerable pricing pressures. Companies use TO cans and manual labour or more sophisticated hybrid integration where the laser and photodetectors are dropped onto a common platform to meet various PON transceiver specifications. Why is OneChip pursuing indium phosphide-based monolithic integration and why will such an approach be cheaper than a hybrid platform that can address several PON standards?
A. Most current FTTH transceiver providers base their transceivers on either discrete optics or planar lightwave circuit (PLC) designs. These designs offer low levels of integration and require assembly from multiple parts. There is little technical differentiation among them. Rather, vendors must compete on the basis of who can assemble the parts in a slightly cheaper fashion. And there is little opportunity to further reduce such costs.
While more integrated than fully discrete optics-based designs, PLC designs still require discrete active components and the assembly of as many as 10 parts. Great care must be taken, during the manufacturing process, to align all parts of the transceiver correctly. And while packaging can be non-hermetic, these parts can fall out of alignment through thermal or mechanical stress. PLC designs also have proven to be an expensive alternative. For all of these reasons, the PON system vendors with which OneChip has engaged have indicated that they are not interested in deploying PLC-based designs.
OneChip Photonics is taking a new approach with its breakthrough PIC technology. OneChip is monolithically integrating all the functions required for an optical transceiver onto a single, indium phosphide (InP)-based chip. All active AND passive components of the chip – including the distributed-feedback (DFB) laser, optically pre-amplified detector (OPAD), wavelength splitter (WS), spot-size converter (SSC), and various elements of passive waveguide circuitry – are, uniquely, integrated in one epitaxial growth step, without re-growth or post-growth modification of the epitaxial material.
With respect to transmit performance, OneChip’s single-frequency DFB lasers will offer a superior performance – much more suitable for longer-reach and higher bit-rate applications – than competing Fabry-Perot (FP) lasers. With respect to receive performance, OneChip’s optically pre-amplified detectordesign is a higher gain-bandwidth solution than competing avalanche photodiode (APD) solutions. It also is a lower-cost solution, as it does not require a high-voltage power source.
OneChip’smonolithic photonic integrated circuits (PICs) have the smallest footprint on the market, the optical parts are aligned for life, and the parts are highly robust (resistant to vibration and other outside elements). Further, OneChip’s PICs are designed for automated mounting on a silicon optical bench, without requiring active alignment, using industry-standard, automated assembly processes – resulting in high yields of good devices.
Utilizing automated production processes, OneChip can maintain the highest production scalability (easily ramping up and down) in the industry and respond rapidly to customer needs. Standard production processes also mean reliable supplies to customers, at the lowest prices on the market.
Q. Several companies have explored integrated PON solutions and have either dismissed the idea or have come to market with impressive integrated designs only to ultimately fail (e.g. Xponent Photonics).Why are you confident OneChip will fare better?
As noted earlier, PLC designs developed by vendors such as Xponent are not fully integrated. PLC designs still require discrete active components and the assembly of as many as 10 parts, using a glass substrate. This results in poor yields and high costs.
OneChip is taking a fundamentally different approach. We are the only company in the optical access market that is monolithically integrating all the active and passive functions required for an optical transceiver onto a single, indium phosphide (InP)-based chip. This enables us to achieve low cost, high performance, high yields and high quality.
OneChip is one of only a few companies with new core intellectual property and advanced technology in the optical transceiver business that can sustain a competitive advantage over other optical component providers, which rely on conventional technology and assembly processes. Carriers and system providers recognize that an approach, which would eliminate assembly from multiple parts, is needed to lower the cost and improve the performance of transceivers, Optical Network Terminals (ONTs) and Optical Line Terminals (OLTs) in optical access networks. We believe OneChip’s fully integrated technology can help unleash the potential of FTTH and other mass-market optical communications applications.
Q. If integrated PON is a good idea why, in OneChip’s opinion, have silicon photonics startups so far ignored this market?
A. “Silicon photonics” designs face the inherent limitation that a laser cannot be implemented in silicon. Therefore, separate optical and electrical devices must be grown with different processes and then assembled together. With as many as 10 parts having to be interconnected on a ceramic substrate, the alignment, tuning and reliability issues can significantly add costs and reduce yields.
In addition, system providers and service providers need to be cognizant of the inherent performance limitations with transceivers built from discrete parts. While short-reach EPON transceivers already have been optimized down to below a U.S. $15 price, these implementations can only meet low-end performance requirements. Networks would require a switch to more costly transceivers to support longer-range EPON, 2.5G EPON, GPON or 10G PON. Because most service providers are looking to reap the payback benefits of their investments in fiber installations/retrofits over the shortest possible timeframes, it doesn’t make sense to risk adding the high cost of a forklift changeover of transceiver technology at some point during the payback period.
Q. PON with its high volumes has always been viewed as the first likely market for photonic integrated circuits (PICs). What will be the second?
A. OneChip recognizes that optical communications is becoming economically and technologically mandatory in areas outside of traditional telecommunications, such as optical interconnections in data centers and other short to ultra-short reach broadband optical networks. OneChip is poised to introduce photonics integration into these and other high-volume business and consumer markets, where our PIC technology can reduce costs and improve performance.
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