A fully engineered QSFP AOC using solderable 4-channel optical transceiver modules

We report a solderable 4-channel VCSEL-based optical transceiver module perfect for high-volume production of QSFP AOCs. The 4-channel module can be simply mounted on a PCB together with other electronics components through a solder reflow process. We fabricated a PCBA in compliance with the standard of QSFP edge connector. The PCBA has an MCU written with a firmware included with a look-up table to control the optical module over the operating temperate range. Integrating the PCB assembly into a die-cast housing, we fabricated fully engineered QSFP AOC. As we tested a BER characteristic for 14-Gb/s ×4-channel operation, the QSFP AOC has a total jitter margin of 0.5 U.I., and achieve a BER of <;10^-15.

I. Introduction

The volume demand of quad small form-factor pluggable (QSFP) active optical cables (AOCs) [1] has been growing especially for a lot of optical 40-Gb/s paths used in edge routers and network switches in data centers. At the same time, a lower price for QSFP AOCs has been demanded to exploit their applicable domains in actual systems. QSFP cable suppliers generally support both copper cables and AOCs which exist together in data center applications. A ratio of the used amount depends upon the required specifications of bit rate and transmission distance. The ratio of choosing AOCs has been increasing because the required bit rate is becoming higher continuously. Accordingly, an available distance of copper cables is becoming shorter. To quickly ramp up the volume production of AOCs in a cost effective fashion, we developed a 14-Gb/s × 4-channel solderable optical transceiver module which can be mounted on a printed circuit board (PCB) together with electronic components by a surface mounting technology (SMT) machine. A PCB assembly (PCBA) can be fabricated through a simple solder-reflow process suitable for high-volume production. The 4-channel transceiver module shares several piece parts of the 12-channel optical modules which have been in high-volume production [2]. Consequently, low prices of the shared piece parts contribute reducing the total cost. In this report, we describe the 14-Gb/s × 4-channel solderable optical transceiver module design and the performance together with reliability test results based on Telcordia-GR-468-CORE. We also describe a solder-reflow process for a QSFP-compliant PCBA using the parallel optical module. We actually fabricated PCBAs through the described solder-reflow process. The PCBAs were tested with a commercially-available QSFP development kit and then built-in a QSFP AOC. We report the performance of the fully engineered QSFP AOC.