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Fabrication and assembly automation of TERabit optical transceivers based on InP EML arrays and a Polymer Host platform for optical InterConnects up to 2 km and beyond

Periodic Reporting for period 2 - TERIPHIC (Fabrication and assembly automation of TERabit optical transceivers based on InP EML arrays and a Polymer Host platform for optical InterConnects up to 2 km and beyond)

Reporting period: 2020-07-01 to 2021-12-31

The capability to provide Terabit capacity and the possibility for high-volume production at low cost are the two main requirements that rule the development of next generation optical modules for datacom applications. The 400GbE standards have been approved recently, however the efforts for developing the next optical modules providing Terabit capacity have already started. TERIPHIC is an Innovation Action project aiming to develop a new generation of pluggable and mid-board transceiver modules with capacities from 800Gb/s up to 1.6 Tb/s, and the required custom hardware for automating the assembly process, thus enabling mass-producible, next generation interfaces inside DC switches.

Figure 1 (left) presents the optical engine that sits at the heart of the transceiver, and is based on the hybrid integration (edge coupling) of the EML/PD arrays with a polymer motherboard. (right) the edge-coupling process of an EML array to PolyBoard using the custom gripper tool

To do that, TERIPHIC will simplify the design of the transceivers by reducing the number of interfaces to be integrated and will develop the necessary hardware for the automation of the assembly process. To achieve the first, TERIPHIC will combine arrays of multi-functional components such as InP EMLs and high speed InP PDs with a low-cost polymer motherboard that will also perform MUX/DEMUX functionalities. To achieve the latter, TERIPHIC will modify commercial photonic assembly machines, by building custom gripper arms. The result will be Terabit transceiver modules which cost less than 1 €/Gbps.
The main technical achievements during the first period of TERIPHIC can be summarized as follows:

WP2: System design and definition of integration and packaging engine
The system requirements for intra-DC interconnects and application scenarios of TERIPHIC transceivers have been defined and have been translated into component specifications. The transceiver module designs have been produced and the packaging processes have been defined. Updated simulations studies were carried out to assess the system performance. Preliminary experiments using test equipment were realized.

WP3: Development of components and integration engine for Terabit optical subassemblies (Fig. 3)
The second generation of photonic components including 8-fold EML and PD arrays, 8-ch AWG polymer motherboards have been fabricated. The EMLs achieved approx. 40 GHz 3-d bandwidth, the PDs approx. 50 GHz making them appropriate for 56 GBaud PAM-4 operation. The custom gripper tool for automatically assembling up to 8-fold EML/PD arrays to PolyBoards has been developed and is installed at HHI’s assembly machine. Four 400Gb/s TOSA/ROSA have been assembled and 800Gb/s TOSA/ROSAs are in the making. 4-ch and 8-ch FlexLines with pitch adaptation have been developed and a proof-of-concept flip-chip fixation method developed.

WP4: Development of InP-DHBT linear driver arrays and selection of BiCMOS electronics
400G DSP chips have been selected to be integrated on the 400G transceivers. Moreover, state of the art 5nm 800G DSP platform, that has only recently hit the market, has been secured and will power the 800G and 1.6T TERIPHIC transceivers.
Two generations of quad InP-DHBT linear driver (Fig. 3) arrays have been developed, capable of 64GBaud PAM-4 operation, with <0.8W/channel power consumption, achieving 30% reduction in the. footprint of the 2nd gen. drivers compared to the 1st gen.

WP5: Packaging of TERIPHIC modules
The design work of the transceiver PCBs, including layouting and mechanical designs has progressed and is available for all modules. Packaging processes for the TERIPHIC pluggable and mid-board modules have been defined, considering the all the technical issues that were brought along with the innovations. The performance of the assembly process of FlexLines is being evaluated. TERIPHIC’s most complex module, the 1.6T will accommodate two 800G DSP chips and four quad InP-DHBT linear driver arrays.

WP6: System integration, testing and performance evaluation
The experimental testbeds at lab settings and at the system vendor and network operator settings are setup and available. The TERIPHIC pluggable and mid-board transceiver modules will be tested at lab settings with test equipment, and then in intra-DC settings for shorter reach links up to 2km and in inter-DC network settings for longer links up to 10 km. An evaluation board comprising a 4-ch TOSA/ROSA and a 400G DSP chip is being assembled as a precursor to module 1, to verify the potential of the TERIPHIC concept. Modulation tests with EML arrays on chip subcarriers have been realized showing good large signal performance up to 53 Gbaud.

WP7: Dissemination and exploitation activities, roadmaps and manufacturability studies
Individual exploitation and business plans for each partner were generated and are continuously updated. Six publications acknowledging TERIPHIC have been submitted to prestigious journals and conferences. Dissemination activities through the website, social media, the promotion video and workshop presentations, are progressing well and visibility is increasing. Technoeconomic analysis have been carried out. Market surveys and technology roadmaps are analyzed to ensure the project targets remain relevant and impactful after the project end. IPR in relevant topics are tracked and evaluated.
TERIPHIC has developed state of the art components, that were up to now used primarily for research, and adjusting them so they are compatible with product development practices. The TRL of the components increased, providing a direct exploitation path. 8-fold EML arrays with > 40 GHz bandwidth and 8-fold PD arrays with >50 GHz bandwidth, suitable for 53Gbaud PAM-4 operation have been developed. InP-DHBT linear drivers have been designed and fabricated, capable of 64Gbaud PAM-4 operation and <0.8W/channel power consumption, perfectly suited for next generation PAM-4 optical interfaces. At the system level, TERIPHIC has development the components and assembly processes that will allow the demonstration of mass producible and thus low-cost Terabit transceivers reaching the <1 €/Gbps threshold. What is more, TERIPHIC transceivers can potentially reduce by 50 % the power consumption of DCs by providing 800Gb/s capacity at the same power consumption of 400GbE interfaces.
Fabricated polymer FlexLines with pitch adaptation that allows flexibility in the interconnection
Microphotograph of quad InP-DHBT linear driver array
TERIPHIC 400Gb/s optical engine and close-up of the edge-coupling process