Small Size Fiber Optic Modules Based on Plastic Packaging Technology for Gigabit Speed Video Link Applications

Abstract

We have developed small size fiber optic modules based on plastic packaging technologies for PCS fiber systems. The transmitter contains a vertical-cavity surface emitting laser (VCSEL) operating at 850nm wavelength, an electronics driver chip, and some passive components. The package is a low cost leadframe style for through-hole or surface mounting (SMT). The SMT fiber optic transmitter is compatible with a reflow soldering process in an infra-red oven of 250/spl deg/C peak temperature. With a specially designed heat shield the prototype shows a stable optical alignment performance before and after the reflow soldering. The output power of the transmitter is limited to 0.7mW to meet eye-safety class I requirements. The transmitter has an integrated coupling optics to provide loose alignment tolerances of /spl plusmn/70 /spl mu/m in lateral axis for a working distance of 500/spl mu/m to PCS optical fibers. The optical coupling power from the transmitter to the PCS fiber has a variation within 1dB over the wide ambient temperature range from -40/spl deg/C to +105/spl deg/C. This enables the usage of very low cost plastic molded connector ferrules. The receiver module contains a high speed MSM photodetector. The special design of the MSM photodetector enables high speed operation up to 3.2Gb/s in combination with a large active area for easy alignment. With two pairs of the fiber optic modules, we demonstrate a 1Gb/s video transmission over up to 15m of polymer cladded silica (PCS) optical fiber. The video link consists of a camera with an electrical S800 LVDS interface and a high resolution monitor. A pair of fiber optic cable connects the two ports replacing and extending the regular electrical cable. In contrast to the electrical cable the optical fiber is thin, light weight, and highly flexible. The high power budget margin of the link allows three in-line connectors for the 10-15m link length. For other applications a longer link length is feasible using higher bandwidth optical fiber. The VCSEL based fiber optic transmitter module has passed 3000 hours of high temperature operating life test at an operating ambient temperature of +105/spl deg/C. The FOTs have also passed 1000 cycles of temperature cycling from -40/spl deg/C to +125/spl deg/C according to automotive requirements. The modules have passed electrostatic discharge tests at levels up to /spl plusmn/4000V under human body model and /spl plusmn/400V for machine model with no significant change in optical output power. The applications include automotive and industrial video links, home networks, and real-time surveillance systems.