Epiwafer foundry and substrate maker IQE plc of Cardiff, Wales, UK says that researchers working on the European Commission funded Vertically Integrated Systems for Information Transfer (VISIT) program (for which IQE produces wafers) have demonstrated high-reliability vertical-cavity surface-emitting laser (VCSEL) devices operating at record data rates of up to 40Gb/s, which is four times faster than the current single-channel (serial) data rate used in commercial systems.
VISIT is an EU-funded program with the remit to focus on strategic, high-value photonic components and subsystems for scalable economic broadband access and local-area networks. The central objective of the program, which started in October 2008, is the research, development, test and exploitation of system-enabling optical transmitters having a completely novel design and/or largely improved functionality compared to current technology.
The directly modulated VCSEL devices fabricated on material grown by IQE in Cardiff operate at 850nm, which is the current standard wavelength for optical fiber applications used in short-reach data communication and storage-area networks.
The new technology increases data throughput by up to 400 times the speed of current copper Ethernet systems and four times that of the latest optical technologies. The VISIT researchers demonstrated VCSELs operating at data rates of up to 30Gb/s at 85˚C, and up to 40Gb/s at 25˚C with bit-error ratios of less than 10E-12 which, for many data communication applications, is considered ‘error-free’.
The VCSELs also demonstrated temperature stability in the linear region of the light power versus current characteristic with a sub-25µW/˚C change in emission power for operation below 6mA at temperatures of 20-100˚C. The peak output power exceeded 8mW for multi-mode operation and up to 4mW 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 10kA/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 40Gb/s packaged VCSELs, complete with an OM3 fiber pigtail and a high-frequency electrical V-connector for ease of system-level optical link testing and development.
The prototype VCSELs fabricated using new device processing techniques and device geometries on wafers produced by IQE’s optoelectronic facility in Cardiff operated reliably at 40Gb/s in initial tests, making them suitable for optical interconnectors as well as for optical fiber networks for high-data-rate applications such as data centers.
The next development stage under the VISIT program will focus on final directly modulated VCSEL benchmarking and design and processing refinement, including device designs for reliability and manufacturability. The team will also work on further improvements in the packaging and testing of optical transmitter subassemblies.
VISIT is funded by the European Commission Framework 7 Programme, with Dr Michael Hohenbichler as project officer. It is led by professor Dieter Bimberg of the Technical University of Berlin (Germany), and also includes the following project partners: IQE (UK), Intel Performance Learning Solutions Ltd (Ireland), VI Systems GmbH (Germany), Chalmers University of Technology (Sweden), The University of Cambridge (UK), University College Cork via the Tyndall National Institute (Ireland), Riber S.A. (France), and the A.F. Ioffe Physical-Technical Institute of the Russian Academy of Sciences (Russia).