Bi-directional optical communication at 10 Gb/s on FR4 PCB using reflow solderable SMT transceiver

We report the development of 10 Gbps bi-directional optical data communications on FR4 PCB to realize opto-electronic circuit board (OECB). The work includes the design, fabrication and high-speed performance of a 10 Gbps surface mount optical transceiver module that can be reflow soldered, developing efficient optical coupling methods using precise injection molded lenses and studying their attachment methods to the optical source and receiver, realizing efficient optical coupling between transmitter and receiver subsystems for a multi mode epoxy waveguide on the PCB and developing a test vehicle. The compact and highly integrated SMT optical transceiver module in multilayer LTCC substrate consists of optical devices like VCSEL and PIN photo diode and the electrical circuits like VCSEL driver, trans impedance amplifier (TiA) and limiting amplifier (LA). The module contains a cavity, in which the electrical, optical devices and passives are mounted using passive attachment methods, a recess to house a lens and locator holes to align the lens with the VCSEL and PIN. The lens is an injection molded epoxy lens with biconvex elements for both transmitter and receiver integrated as a single element to improve the coupling between the source and the waveguide on the PCB. The module is designed to relax the assembly tolerances of optical elements so that normal conventional electronic assembly process can be used. Solder bumps are formed on the bottom layer of the LTCC to convert the module into a cavity down SMT package. The waveguides are made of high temperature epoxy material and are attached to the PCB using adhesive material. The 45deg mirrors are formed through laser ablation process. The module is reflow soldered using conventional reflow oven. The opto-electronic circuit board (OECB) is performance evaluated and performance results are presented.