10Gbps multi-mode waveguide for optical interconnect

In this paper, high-speed multi-mode waveguide array is proposed. As a core material, a polymer called SU-8 is used. The index of SU-8 at a wavelength of 850 nm is 1.58. It is highly transparent for wavelengths > 800 nm, has shown heat resistance to temperature > 200 degrees Celsius and it is chemically and mechanically stable [Downey et al., 1993], so it is most suited for optical interconnect applications. In order to reduce the coupling loss of the system, the dimensions of waveguides are taken to be 50 × 50 μm². The SU-8 is spin-coated on the glass substrate. By varying the spin speed, the height of the layer can be varied from 10 to 60 μm. The layer is pre-baked at 95 degrees Celsius to evaporate the solvent. Then after pre-heating, the film is exposed to UV-light with a mask. Following the UV-exposure, the film is post-baked at a temperature of again 95 degrees Celsius. In this post exposure baking step the cross-linking of the polymer takes place in all exposed areas. The SU-8 film is developed in RER 600 (PGMEA). Next, the defined structures are exposed to UV-light and hard-baked at 150 degrees Celsius [Downey et al., 1993], Finally, the embedded waveguides are covered by cladding layer and measured by 850 nm LD. The measurements demonstrate robust 10 Gbps data transmission exceeding 50 mm using a new high-speed 50 μm multimode planar waveguide circuit (PLC). This indicates that experiments driving VCSEL-based 850 nm LD optical links 231-1 PRBS signal at speeds up to 10 Gbps. The results can be used to broaden the component specification range for 10 Gigabit optical interconnects applications.