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90 PCB007 MAGAZINE I JANUARY 2021 bandwidth to 76.8 Tb/s. The organic OE Mod- ule is seen in Figure 12d [11] . IBM's OE Module progression is detailed in Figure 12. The goal is EXABIT computing (1015 bytes/sec) and on the short term from 2008 to 2012, the progress for the Optochip from 240 Gb/s to 480 Gb/s. The second step uses the OPCB with the polymer waveguides and the third step includes direct optical connections to the OE Module. Which brings us back to where we are to- day. A look back at Figure 3 shows the pro- gression from 2008 to the current architecture of the P775 supercomputer. The optical inter- connects go directly to the processor module and use a 48 channel times 4 (48x4) operat- ing at 12.5 Gb/s. These are supplied by Ava- go and, soon, others. This allows the nearly 540,000 optical channel connections required for the system. BLUE WATER will require over 5 million optical connections. The optical connections and cables are seen in Figure 13. This 192-channel flexible waveguide is an optical backplane operating at 850 nm and 12.5 Gb/s. The flex material is polyimide with 12 WGs per tail with 250 nm pitch. The fabrication of the Optocard flex cables and rigid waveguides was conducted by End- icott Interconnect Technologies (EIT) of Bing- hampton, New York [12] . These were fabricated by direct deposition of the waveguide mate- rial (Dow Chemical XP-5202A) onto a hybrid PCB substrate of Upilex polyimide with a lay- er of resin-coated copper (RCC) laminated on both sides and to a frame. The copper is etched away to leave the resin bonded to the Upilex. This resin improves the adhesion of the wave- Figure 12: (12a) Structure, (12b) performance (bandwidth limits) of 'chip-module-board' structure, which is only 12.6 Tb/s for today's structure. What is needed is a more miniaturized structure proposed in (12c), using optical TX and Rx along with waveguides (OE Modules) and optical bussing on the PCBs. This raises the bandwidth to 76.8 Tb/s. (12d) The organic OE Module.