120 Gb/s-level VCSEL array optical subassembly using passive alignment technique

Abstract

Our suggested VCSEL array optical subassembly (OSA) for 120 Gb/s-level parallel optical interconnect modules was composed of a 12 channel VCSEL array chip, a SiOB, two silicon spacers, and a molded microlens with accurate guide pin holes. For high speed operation above 10 Gb/s per a channel, we carefully designed transmission lines on the SiOB. The results of the transmission lines were measured as large bandwidth more than 26 GHz and low channel crosstalk less than -30 dB. And, to achieve high coupling efficiency, the planar-convex microlens was adopted. The average coupling efficiency coupled to 62.5 mum multi-mode fiber (MMF) ribbon was approximately 85%, the value of which means nothing but material loss itself. In this paper, the fabrication process of the VCSEL OSA is emphasized on low cost packaging. In particular, a suggested passive alignment technique is described in detail to align both the VCSEL and the microlens array. An accurate assembly in this work was carried out through vision alignment using 2-sight camera of a precise pick-and-place machine, Suss MicroTec TRIAD 05 flip-chip bonder. To evaluate the DC and AC characteristics of the completely fabricated VCSEL array OSA, we measured optical output powers (L-I-V curve) and 4.25 Gb/s, 6 Gb/s, 10.31 Gb/s eye-diagrams on condition of setting-up with MT ferrule terminated 12 channel 62.5 mum MMF and a G-S-G probe. We successfully demonstrated high speed and high efficient VCSEL array OSA with clear 10.31 Gb/s eye diagrams and low coupling loss.