The applications of optical solution as long-link interconnect formed the backbone of data transfer system in the past decades. However, the implementation of this solution in the short-link interconnects still has some obstacles including higher production cost and complex integration. This obstacle needs to be solved as an electrical interconnect application has reached the limit in data speed and needed a replacement technology immediately. The use of polymer for optical waveguide material is believed to reduce the production cost while maintaining the performance. The polymer waveguide combined with the 45° mirror coupler can provide a more straightforward integration process. In this study, a low-cost SU-8 polymer waveguide combines with NOA-61 as waveguide cladding show a decent performance with a propagation loss of 0.75 dB and excess loss of 2.616 dB. Mirror coupling loss is also measured at 1.496 dB average for all channel. The fabricated waveguide is confirmed to successfully transmit light signal at a speed of 2.5 Gb/s per channel.

The applications of optical solution as long-link interconnect formed the backbone of data transfer system in the past decades. However, the implementation of this solution in the short-link interconnects still has some obstacles including higher production cost and complex integration. This obstacle needs to be solved as an electrical interconnect application has reached the limit in data speed and needed a replacement technology immediately. The use of polymer for optical waveguide material is believed to reduce the production cost while maintaining the performance. The polymer waveguide combined with the 45° mirror coupler can provide a more straightforward integration process. In this study, a low-cost SU-8 polymer waveguide combines with NOA-61 as waveguide cladding show a decent performance with a propagation loss of 0.75 dB and excess loss of 2.616 dB. Mirror coupling loss is also measured at 1.496 dB average for all channel. The fabricated waveguide is confirmed to successfully transmit light signal at a speed of 2.5 Gb/s per channel.

C. Croupe, "Future of video content: Evolution toward 2020," Nokia-Bell Labs, Jun. 2015. [Online]. Available: http://www.nokia-sbell.com/Default.aspx? tabid=351&ArticleID=4721.
[2] Z. Li, I. Shubin, and X. Zhou, "Optical interconnects: recent advances and future challenges," Optics Express, vol. 23, no. 3, pp. 3717-3720, Feb. 2015.
[3] R. Dangel et al., "Optical interconnects for board level applications," in SPIE OPTO: Integrated Optoelectronic Devices, San Jose, California, vol. 7219, Feb. 2009, pp. 1-7
[4] J. Chen, "Polymer waveguide based optical interconnects for high-speed on-board communications," PhD Thesis, Department of Engineering, University of Cambridge, Cambridge, UK, Jun. 2016.
[5] W. J. Lee, S. H. Hwang, J. W. Lim, C. H. Cho, G. W. Kim, and B. S. Rho, "Optical interconnection module integrated on a flexible optical/electrical hybrid printed circuit board," in 2009 59th Electronic Components and Technology Conference, San Diego, California, May 2009, pp. 1802-1805
[6] C. Xu, "Simulation of silicon photonics," in Synopsys Rsoft Silicon Photonics Workshop, San Diego, California, Sep. 2016, p. 42
[7] F. X. Chang et al., "High-speed Light Peak optical link for high energy applications," Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, vol. 765, pp. 69-73, Nov. 2014.
[8] K. Sang-Taek et al., "Flip-chip ready 850 nm VCSEL with BCB planarization for optical interconnects," in OECC/ACOFT 2008 - Joint Conference of the Opto-Electronics and Communications Conference and the Australian Conference on Optical Fibre Technology, Sydney, Australia, Jul. 2008, pp. 1-2
[9] W. A. Vis, "Polymer materials, processes, and structures for optical turning in 3D glass photonic interposers," PhD Thesis, School of Materials Science and Engineering, Georgia Institute of Technology, May 2016.
[10] J. M. Senior, Optical fiber communications principles and practice, 3th ed. Essex, England: Prentice Hall, 2009.
[11] H. H. Hamid, T. Fickenscher, and D. V. Thiel, "Experimental assessment of SU-8 optical waveguides buried in plastic substrate for optical interconnections," Applied Optics, vol. 54, no. 22, pp. 6623-6631, Aug. 2015.
[12] W. Moeller, W. Heitmann, and M. Reich, "OTDR calibration for attenuation measurement," in ECO4 (The Hague '91), The Hague, Netherlands, vol. 1504, Sep. 1991, pp. 47-54
[13] C. Choi et al., "Flexible optical waveguide film with 45-degree micromirror couplers for hybrid E/O integration or parallel optical interconnection," in Integrated Optoelectronic Devices San Jose, CA, vol. 5358, Jun. 2004, pp. 122-126
[14] J.-J. Kim and J.-S. Kim, "Polymeric multimode waveguide arrays for one- and two-dimensional optical interconnects," in Optical Science and Technology, the SPIE 49th Annual Meeting, Denver, Colorado, vol. 5517, Aug. 2004, pp. 141-151
[15] A. Marinins et al., "Thermal reflow engineered cylindrical polymer waveguides for optical interconnects," IEEE Photonics Technology Letters, vol. 30, no. 5, pp. 447-450, Jan. 2018.
[16] C. Yi-Ming et al., "10Gbps multi-mode waveguide for optical interconnect," in Proceedings Electronic Components and Technology, 2005. ECTC '05., Lake Buena Vista, FL, vol. 2, Jun. 2005, pp. 1739-1743
[17] S. S. Zakariyah et al., "Fabrication of polymer waveguides by laser ablation using a 355 nm wavelength Nd:YAG laser," Journal of Lightwave Technology, vol. 29, no. 23, pp. 3566-3576, Oct. 2011.
[18] E. Zgraggen et al., "Laser direct writing of single-mode polysiloxane optical waveguides and devices," Journal of Lightwave Technology, vol. 32, no. 17, pp. 3036-3042, Jul. 2014.
[19] L. Wang, X. Wang, W. Jiang, J. Choi, H. Bi, and R. Chen, "45° polymer-based total internal reflection coupling mirrors for fully embedded intraboard guided wave optical interconnects," Applied Physics Letters, vol. 87, no. 14, pp. 1-3, Aug. 2005.
[20] C. Summitt, S. Wang, S. Namnabat, L. Johnson, T. Milster, and Y. Takashima, "Fast fabrication of polymer out-of-plane optical coupler by gray-scale lithography," Optics Express, vol. 25, no. 15, pp. 17960-17970, Jul. 2017.
[21] R. Singhal, M. N. Satyanarayan, and S. Pal, "Fabrication of monomode channel waveguides in photosensitive polymer on optical adhesive," Optical Engineering, vol. 50, pp. 1-3, Sep. 2011.
[22] MicroChem, "Datasheet : SU-8 2000 Permanent Epoxy Negative Photoresist," Feb. 2012. [Online]. Available: http://microchem.com/pdf/SU-82000Data Sheet2025thru2075Ver4.pdf.
[23] Norland Products, "Datasheet : Norland Optical Adhesive 61," May 2018. [Online]. Available: https://www.norlandprod.com/adhesives/noa61pg2.html.
[24] S.-H. Hsu, C.-Y. Tsou, C.-M. Wang, and S.-C. Tseng, "10 Gb/s optical interconnection on flexible optical waveguide in electronic printed circuit board," Optics and Photonics Journal, vol. 03, no. 02, pp. 252-255, Jun. 2013.
[25] C. I. Estevez, D. Guidotti, and G. K. Chang, "A novel lightwave device integration and coupling process for optical interconnects," in 2009 59th Electronic Components and Technology Conference, San Diego, California, May 2009, pp. 1859-1864
[26] J. Yao et al., "Optical interlayer coupling design for optical interconnects based on mirror enhanced grating couplers," in 2012 Optical Interconnects Conference, Santa Fe, NM, May 2012, pp. 27-28
[27] K. Joon-Sung and K. Jang-Joo, "Stacked polymeric multimode waveguide arrays for two-dimensional optical interconnects," Journal of Lightwave Technology, vol. 22, no. 3, pp. 840-844, Mar. 2004.
[28] A. L. Glebov, M. G. Lee, and K. Yokouchi, "10+ Gb/s board-level optical interconnects: fabrication, assembly, and testing," in SPIE Photonics Europe, Strasbourg, France, vol. 6185, Apr. 2006, pp. 1-12
[29] N. Hendrickx, J. V. Erps, H. Thienpont, and P. V. Daele, "Out-of-plane coupling structures for optical printed circuit boards," in OFC/NFOEC 2008 - 2008 Conference on Optical Fiber Communication/National Fiber Optic Engineers Conference, San Jose, California, Feb. 2008, pp. 1-3
[30] T. Matsushima, K. Tanaka, T. Nakashiba, Y. Yagyu, and M. Kubo, "Development of micro-mirrors in optical-electric printed wiring boards using excimer laser," in Lasers and Applications in Science and Engineering, San Jose, California, vol. 6459, Mar. 2007, pp. 1-8
[31] I. K. Cho, W. J. Lee, M. Y. Jeong, and H. H. Park, "Optical module using polymer waveguide with integrated reflector mirrors," IEEE Photonics Technology Letters, vol. 20, no. 6, pp. 410-412, Mar. 2008.
[32] J. V. Erps, N. Hendrickx, E. Bosman, P. V. Daele, C. Debaes, and H. Thienpont, "Design and fabrication of embedded micro-mirror inserts for out-of-plane coupling in PCB-level optical interconnections," in SPIE Photonics Europe, Brussels, Belgium, vol. 7716, May 2010, pp. 1-10
[33] C. Choi, "Thin-film vcsel and optical interconnection layer fabrications for fully embedded board level optical interconnects," PhD Thesis, Electrical and Computer Engineering, The University of Texas at Austin, Dec. 2003.
[34] S. Tomoaki and T. Atsushi, "Flexible opto-electronic circuit board for in-device interconnection," in 2008 58th Electronic Components and Technology Conference, Lake Buena Vista, FL, May 2008, pp. 261-267
[35] L. Wang, X. Wang, J. Choi, D. Hass, J. Magera, and R. T. Chen, "Low-loss thermally stable waveguide with 45° micromirrors fabricated by soft molding for fully embedded board-level optical interconnects," in Integrated Optoelectronic Devices 2005, San Jose, California, vol. 5731, Mar. 2005, pp. 87-93