Multicore fiber 4 TX + 4 RX optical transceiver based on holey SiGe IC

A novel optical transceiver with 4 transmitter plus 4 receiver channels designed for coupling to multicore multimode fiber has been fabricated and characterized. The transceiver is based on the holey Optochip concept where 4-channel VCSEL and photodiode arrays are flip-chip attached to a single-chip SiGe IC using AuSn solder. Optical vias (holes) are fabricated into the SiGe IC to enable optical access to the conventional topside emitting 850-nm optoelectronic arrays. The optoelectronic arrays are arranged in a quad-VCSEL and quad-photodiode configuration where the 4 devices are on a 2 × 2 array on a dense 50-μm pitch. The transceiver module is completed by flip-chip soldering the Optochip onto a 8 mm × 8 mm high-speed high-density organic carrier. Optical access through the backside of the IC is provided through 2 optical vias. Electrical I/O is supplied through BGA pads on 0.8 mm pitch at the bottom of the module. High-speed characterization was carried out between 2 modules soldered to test cards, a transmitter (TX) and a receiver (RX) module. Each of the 4 optical outputs from the TX Optochip was coupled into a MMF and directed to individual photodiodes in the RX module. Eye-diagrams were measured for TX outputs as well as TX-to-RX links at data rates 20 Gb/s to 42 Gb/s. The 4 optical links operate error free up to 40 Gb/s, achieving a record data rate for multimode parallel optical transceivers.