Low-loss 4 × 2 channels polymer optical waveguide with circular graded-index cores for high-density integration on printed circuit boards

For high-speed and high-density optical interconnections on boards, we propose and demonstrate a novel parallel polymer waveguide with circular cores in which parabolic graded refractive index (GI) profiles are formed. This new waveguide exhibits very low loss (0.029 dB/cm at 850 nm) and high bandwidth (83 Gbps/ch for 1 m) due to the GI profile. We also theoretically and experimentally demonstrate the possibility of higher-density integration of waveguides by allowing for the tolerance for the misalignment between VCSELs and waveguides, compared with the SI waveguides. In addition, we demonstrate that the GI cores can dramatically decrease the inter-channel crosstalk.