European researchers demonstrate reliability of VCSEL vertical laser devices at 40 Gbit/s
The European Commission funded Vertically Integrated Systems for Information Transfer (VISIT) programme started in 2008 to research, development, test and exploitation of system-enabling optical transmitters with novel designs or largely improved functionality.
The directly modulated VCSEL devices fabricated on material grown by IQE at its Cardiff facility operate at 850nm for short-reach fibre data communication and storage area networks. The VISIT researchers demonstrated VCSEL devices operating at data rates of up to 30 Gbit/s at 85˚C, and up to 40 Gbit/s at 25˚C with bit error ratios of less than 10E-12.
The VCSEL devices also demonstrated high temperature stability in the linear region of the light power versus current characteristic with a less than 25µW/˚C change in emission power for operation below 6 mA at temperatures between 20 to 100˚C. The peak output power exceeded 8 mW for multi-mode operation and up to 4 mW for single mode operation, all with differential slope efficiencies exceeding 70% at up to 40˚C.
Multi-mode VCSEL device operation was demonstrated at current densities well below 10 kA/cm2 which is a critical factor in determining device reliability. This is expected to greatly improve with the further development of single-mode VCSELs.
The VISIT team has also produced the first 40 Gbit/s packaged VCSELs, complete with an OM3 fibre pigtail and a high frequency electrical V-connector for ease of system-level optical link testing and development.
The next development stage under the VISIT programme will focus on final directly modulated VCSEL benchmarking and design and processing refinement including device designs for reliability and manufacturability. The VISIT team will also work on further improvements in the packaging and testing of optical transmitter subassemblies.
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