Experimental assessment of SU-8 optical waveguides buried in plastic substrate for optical interconnections.

Abstract

Multimode polymer waveguides have been developed to create low-cost, high-speed on-board optical interconnects. Buried optical waveguides made from SU-8 in a polymethyl methacrylate polymer (PMMA) substrate covered with a thin PMMA sheet are a low-cost option for electro-optical interconnects. The propagation losses for a 600 μm×600 μm straight waveguide were 1.96, 1.32, and 1.39 dB/cm, respectively, at three different wavelengths (850, 1310, and 1550nm). The bending loss for a 15mm bending radius is as high as 6 dB/cm. Transition and radiation losses dominate overall loss when the bending radius is less than 30mm. The waveguide was excited using a multimode 850nm VCSEL transmitter and detected using butt-coupled and lens-coupled receivers. The coupling loss was about 1dB for the butt-coupling technique and 2dB for lens coupling. The response bandwidth and the group delay of direct modulated (IF) signal were independent of the channel waveguide for communication speeds up to more than 3GHz. This technique is viable for low-cost, short-length buried optical waveguides.