A 50Gb/s PAM-4 Bi-Directional Plastic Waveguide Link with Carrier Synchronization Using PI-Based Costas Loop. - Ha-Il Song; Hanho Choi; Jun Young Yoo; Hyosup Won; Cheong Min Lee; Huxian Jin; Tai Young Kim; Woohyun Kwon; Kyoohyun Lim; Konan Kwon; Chang-Ahn Kim; Taeho Kim; et al. (ISSCC, 2022)