At the 2013 SPIE Photonics West conference in San Francisco (5-7 February), VI Systems GmbH of Berlin, Germany (a fabless spin-off of the Technical University of Berlin and the A. F. Ioffe Physico-Technical Institute in St Petersburg, Russia) and the Department of Electrical and Computer Engineering of the University of Illinois at Urbana-Champaign (UIUC) said that they have jointly demonstrated a novel single-mode photonic crystal vertical-cavity surface-emitting laser (VCSEL) suitable for error-free 25Gb/s data transmission over 1km of multi-mode fiber at very low received optical power.
The photonic crystal (PC) VCSEL is manufactured from a proprietary VI System’s wafer that was processed at the UIUC with a defined photolithographic pattern of holes in the top mirror layers, allowing high modulation bandwidth at a low current density. The process results in single-mode emission of the VCSEL at a wavelength of 850nm. Single-mode operation of the laser leads to a reduced chromatic dispersion and therefore expands the transmission distance, as was confirmed by measurements at the Technical University of Berlin (TU Berlin).
Operating at a low current density of 5.4kA /cm2, the PC VCSEL enables -3dB bandwidth of 18GHz. At TU Berlin’s Department of Solid State Physics, error-free optical data transmission at 25Gb/s over 1km of OM4 multi-mode fiber has been realized at very low received power of only 70μW, using a high-speed photoreceiver module from VI Systems.
VI Systems says that single-mode VCSELs extend reach over multi-mode fiber by eliminating the impact of chromatic dispersion of glass at 850nm wavelength, which is particularly important for ultrahigh transmission bit rates within the next generation of datacom and computercom standards.
Target applications are data transmission inside large data-centers, supercomputer clusters and racks of telecom equipment at ultrahigh bit data rates. The firm says that 1km transmission at very low received power allows cost-and energy-efficient 850nm VCSEL-based links to be extended to longer reach, saving space, cost and energy consumption.
