Sn-Ag-Cu-solder-reflow-capable 10-Gb/s × 4-channel very thin high-density parallel-optical modules

In recent years, optical interconnects are attracting attention to achieve high-speed signal transmission in high-end routers, high-end servers, and high performance computing systems. In rack-to-rack applications, AOCs that have the same electrical interface as conventional electrical cables have been equipped in actual systems especially. On the other hand, board-to-board applications have been expected as the next-generation high-density optical interconnects supported by high-density mounting of parallel-optical modules nearby LSI. In order to meet both of demands, we developed 10-Gb/s × 4-channel parallel-optical modules that are capable to be mounted by Sn-Ag-Cu-solder-reflow process which is the most popular for handling other SMDs. The size of fabricated modules is as small as 12mm × 7.2mm × 1.5mm. We paid attention to minimize the thickness to realize a simple heat dissipation structure together with other SMDs. We achieved a very low height as same as 1.5mm in total. We tested transmission characteristics and achieved error-free transmission in back-to-back, OM2 of 100 m and OM3 of 100 m where a power-penalty is estimated to 1dB. Through experiments of transmitting all 4 channels simultaneously, we clarified that the modules have a sufficient jitter margin in all channel. And we verified Sn-Ag-Cu reflow temperature resistance of the modules based on JIS standard whose peak temperature is as high as 250°C (i.e., JIS C 60068-2-58). We evaluated output power variation in TX module and sensitivity variation in RX modules before and after test. Both optical power variation and sensitivity variation are less than ±10%. We also fabricated a small PCB whose edge is compliant with a standard QSFP+ connector and TX and RX modules are mounted a PCB through Sn-Ag-Cu-solder-reflow process. We performed primary reliability tests of temperature cycling, mechanical shock and vibration tests based on the specified conditions in Telcordia GR-468-CORE. As results, optical power and input sensitivity deviation are less than ±10% and transmission characteristics have no degradation in all tests.