Active optical flex module for ultra-short distance data applications

In this paper, we present active optical flex module aimed for mobile device applications. The module utilizes flexible optical waveguides on electrical printed circuit board for data links between high-speed interface devices, such as application processor-to-camera or display module. In this study, flexible and rigid-flex optical electrical circuit boards are used in product emulator designed for in-device optical data links with aggregate data rate up to 120 Gbps (12-ch × 10 Gbps). This paper describes design and fabrication of OE-R/F HDI engine boards with flexible optical interconnect FPCs (OE-FPC); optical coupling methods; chip embedding and assembly procedures; optical engines with 850-nm vertical cavity surface emitting lasers, photo-detectors, and multichannel integrated ICs. Characterization results are given on optical waveguides, I/O couplers, transceiver units, thermal simulations and on selected life-time performance and reliability tests. Low-loss acrylate-based waveguides (~0.0 5dB/cm at 850 nm) are used for OFPCs. Efficient light in/out coupling structures including integrated and embedded 45° mirrors are characterized to meet the target link budget of 10-15 dB at 5-10 Gbps data rate with bit-error-rate (BER) of 10-12. With the chip set used in the test vehicle, the power consumption is approx. 1350 mW for the bi-directional 12-channel 10 Gbit/s/ch optical link (Tx+Rx). This is 112.5 mW per link or 11.25 mW/Gbit/s/link. Bending loss measurements shows that the optical slide flex can be bent down to 2 mm with insignificant increase in loss. Repeatable folding tests indicate of high bend endurance and stability. These results show that our active optical flex module could replace electrical slide or hinge flex and provide high-speed data links free of electromagnetic noise inside typical mobile device configurations.