Q&A: Explaining POET’s Game-changing Optical Interposer Breakthrough

December 15th, 2020

With mass commercialization on the horizon, POET Technologies President and General Manager Vivek Rajgarhia spoke with Canadian journalist Adrian Brijbassi about the company's groundbreaking innovations. In the first part of their interview, Rajgarhia explained why POETs progress is poised to dramatically improve the optoelectronics world, creating cost savings and superior engineering results for the fiber-optics semiconductor industry. 

POET's innovations will include products assembled and tested at Super Photonics, its joint-venture subsidiary formed in partnership with China-based Xiamen Sanan Integrated Circuit — the worlds largest semiconductor wafer manufacturer. On December 3, 2020, POET announced the tapeout of its Multi-Product Wafer Mask Set, a significant achievement that Rajgarhia says marked a first for his 30-plus-year career in the optical communications industry, which included work at MACOM, OpNext (now Lumentum), JDS Uniphase and Lucent.

Also participating in the discussion were Edward Cornejo, an optical industry veteran who joined POET as Vice-President of Product Marketing and Business Development, and Chief Financial Officer Thomas Mika.

Q: What does the tapeout of the Multi-Product Wafer Mask Set mean to you?

Rajgarhia: We have basically crossed the chasm of technology development and moving to product development. We have a product road map of real products that we will make and send to customers, which is what we shared at our annual general meeting, and have been sharing and announcing those products as they come to fruition. So what this multi-product tapeout really means, and it is exciting, is we have taped out different interposer chips that will go into these products that are on our road map.

This multi-product tapeout ultimately will provide us with the different configurations of chips that we will use to make a final product for customer sampling.

Q: I am assuming in your career you have done a number of these tapeouts. 

Rajgarhia: Having been part of many of these companies that have launched several of these products, you're dealing with a similar customer base, and thats one of the things that is exciting for me. 

What POET is doing is a game-changer of how fiber-optics semiconductor technology is being developed. Fiber optics has been a boutique industry. It has been boutique because of the challenges of aligning the light — this very narrow light beam that has to go through very narrow fiber-optics openings. It is very difficult to manufacture and scale at the cost points that have been in use in the industry. What weve done at POET is make the fiber-optic semiconductor manufacturing scale at low cost. We can do very high-speed connections, which is where the industry is going because of the high demand for data bandwidth in these mega-data centers.

Q: In terms of this particular tapeout, can you give a sense of where it would rank — and maybe that's not the right wording — or your level of excitement compared to previous tapeouts you have been a part of. How big of a deal is this one for you?

Rajgarhia: Its difficult to rank one over another after so many years in the industry. In todays world, where optics is becoming a part of our day-to-day lives — whether it is in datacenters (that host video streaming, social media platforms, mobile apps, etc.), autonomous driving, sensing, or 5G — it is much more ingrained in our day-to-day life than what it has been in the past, because of the need to transmit data signals at such high speed. So from that standpoint it is, again, a game-changer because the optical interposer is solving the problem of scale and cost. 

The mix of products that will result from the tapeout of the Multi-Product Wafer Mask Set are for very high speed; such as next generation networks like 400 gigabits, where 400 gigabits per second is needed, or 400 billion bits travelling per second, if you can fathom that. So what we have done provides for that, which for me, is a first in my career. It validates all our technology we've been working on. 

Q: With the tapeout, what does that mean for the progress toward commercialization? The company has stated that it is going into the product-launch phase and the timelines are roughly six to nine months before a final product gets out the door. Does that mean from an engineering perspective the heavy lifting is over in terms of commercialization efforts?

Rajgarhia: So, the heavy lifting is never over. [laughing]

But it changes. I can tell you the heavy lifting of validating the platform is over. We have the different elements and features of the platform validated. We have how we're going to connect lasers to waveguides, how we are going to connect the interposer to the outside world. All that validation has been done. If I can compare it to an electrical vehicle, where the chemistry of the battery is the science. Without that nothing happens. But once you do the chemistry of the battery, you need to package it, and then you need to make a vehicle, even as a demo, so you can demonstrate the battery is usable. You need to show that it holds so much charge, it can run so much distance, and all of those other benefits in order to make the chemistry of the battery meaningful to the consumer.

Here, we have done the heavy lifting of validating the optical interposer and the elements of it that show how those elements will connect together, as well as validated how the interposer will be used in the system of a customer. So when customers get the product, they can use it. 

We have partnered with customers and we have been working with them, learning from their engagement so that we can really fine tune. Now what we're doing is changing the configuration for different applications. We still have to qualify that, but the cycle times are shorter.

Q: In trying to understand how that relationship with customers works, is it a matter of them saying,
We want this,and then your team configures it to their specifications or are they working in lockstep with you to get where they want the technology to go?

Rajgarhia: It is working in lockstep.

Without naming customers, because I cannot because of confidentiality agreements, but as an example, we have this customer who says, Okay, you have this interposer, it looks very cool and neat, but we have this challenge. We need to put it in this small space where such an engine has never been put but it seems like you could do it. But can you validate that it will still perform and you can shrink it and make it in the size we need and can you connect it to the input/output ports?So that confidence was there from them that we could do it. 

We started working and trying to peel the onion to find exactly where the connections would go and what is the best architecture. Those are the things we've been working very, very closely with the customers on. It's a partnership, at the end of the day.

Q: When you completed that work of putting that engine in a place where it had never been, what was their reaction and your reaction? Did it work?

Rajgarhia: We have done the technical feasibility. We did different simulations and analysis. We have not sampled a final product to the customer but that will be done shortly, in the next quarter. But we validated how the heat will move out and how it will get attached in the system, and all those things.

Q: I wanted to focus in on one product or aspect of the MPW that was mentioned in the press release and that's the 100G CWDM4 optical engine. From what I was able to see there are several 100G CWDM4 products out there in the market. How does POET
s 100G CWDM4 differentiate itself from what already exists?

Rajgarhia: 100G CWDM4 has been around for a few years now. The market is growing. The requirement by data-center companies to use more and more of this component in their systems, or in their network, is increasing. It is tied to revenue generation for them, for companies that provide cloud services. They need to reduce the cost of transmitting one bit within their data centers. Otherwise, their business case struggles. 

In order to lower their cost, they have a requirement for reducing the cost of the transceiver module that provides the transmission of the data. So, the vendors are challenged to reduce the cost of the transceivers they sell to the data-center companies. What we are doing, we are not substituting the full module because we are a supplier to the makers of the transceiver module, but we are reducing the cost for our module customers who will use our 100G CWDM4 optical engine, which is a part of the complete transceiver they sell to the data-center companies. 

With our industry background, we do know what the cost structures are, and we know we can reduce that cost for our module customers by roughly 25%-30%.

So where they are not making any margin, they start making margin. As well as in the future when the prices keep needing to go down, we provide a path to that cost reduction. We believe we can supply to many of these module manufacturers and they can have a viable business model by using our optical engines.

Q: What do you expect the market for your 100G CWDM4 will be?

Rajgarhia: So 100G CWDM4 is a particular form factor for 100G single-mode optics, so it is very defined. We will hit the market with that, but a significant market opportunity for us is really at higher speeds. 100G is the lowest speed we are working on. It goes to 400 gigabits, which we are working on, like 400G FR4 engines, and then in the future our platform is applicable to the next generation when the speeds go to 800-gigabit and terabit speeds, what is called co-packaged optics, where you have to package the optical connection very close to the ASIC chip to manage the heat and power. And our interposer platform is very feasible for that work.

Edward Cornejo: I wanted to jump in and say something about the 100G CWDM4, as well. Before joining POET, I spent several years working with a large end customer on a CWDM4 module from beginning to end, and one of the biggest challenges we had was scaling. One of the reasons why they worked with us was because we had semiconductor capabilities and we could scale the ICs [integrated circuits] but scaling the module is very capital intensive. 

The alignments that people do, the equipment they use, all of it is very, very expensive, and the results are difficult to repeat. Its not very consistent.

One of the things our system at POET does is eliminate all of that, because we do it passively using semiconductor bonding equipment and process rather than actively aligning light. So we can scale. Especially CWDM4, where there are multimillions of modules shipping now in the industry. When you talk about scale, I know from my previous job how much money I spent on a factory that supplies you with 30,000 of those modules a month. That was a lot of money. 

Rajgarhia: What Ed just mentioned is critical. The cost goes hand in hand with the ability to scale.

Larger cloud companies are building data centers, gosh, let me say one a month, I dont know if thats entirely accurate, but many of them are building several data centers every year, because data centers are a revenue factory for them. If they get restricted in building any more, they are losing business.

For them, having a supply-chain partner that can manage the supply and scale, it is very important to them. Its one of the values we offer.

Q: You mentioned co-packaged optics. Do you anticipate your technology will quicken the adoption of that innovation?

Rajgarhia: Yeah, as far as adoption on a mass scale, we do believe what we are doing will quicken that, after it is validated. I believe firmly the POET optical interposer platform will speed up co-packaged optics in getting to the level of cost, scale and performance that is needed.

Part 2: How
HugeWill POET Be
The second part of the interview focuses on why Vivek Rajgarhia believes the company will have a day-to-day impact” on everyones life.

Note: Author Adrian Brijbassi has previously written about POET Technologies for the Globe & Mail and has since become an investor in the company.

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