German startup VI Systems claims to have produced the first single vertical-cavity surface-emitting laser (VCSEL) to achieve error-free 40 Gbit/s data transmission through multimode fibre.
Chief executive officer Nikolay Ledentsov presented 20 Gbit/s performance data at the Photonics West event held in San Jose, California, last week.
However, since VI Systems' presentation topics were submitted, the company has boosted the modulation speed of its quantum dot lasers by a factor of two, according to Ledentsov.
"Now we have 40 Gbit/s serial transmission over multimode fiber using our VCSEL and our PIN photodetector module," he said.
The record-breaking, 850 nm devices were produced using the same lithography masks as the 20 Gbit/s VCSELs, but with a modified epitaxial structure.
The design uses InAs quantum dots in a GaAs quantum well, embedded into an AlGaAs matrix to overcome the issues preventing conventional quantum well VCSELs reaching such high speeds.
Quantum dot-based devices suppress lateral carrier diffusion, reducing defect formation and growth that leads to failure in quantum well VCSELs.
Lasers that exploit quantum dots also benefit from low threshold currents and the 40 Gbit/s VCSEL is no exception, operating at just 10 kA/cm2.
Ledentsov points out that the higher modulation rates VI Systems' devices offer are called for by a number of emerging technological standards for data transmission.
"The 17 Gbit/s Fibre Channel FC16G standard is to be released by the end of 2009," he explained. This will be followed by the 22 Gbit/s serial speed Infiniband standard in 2011 and the 34 Gbit/s Fibre Channel standard in 2012.
These are standards for metre-length distances, currently served by transmitting data over copper wires. However the modulation speeds demanded by the latest standards look set to require optical links for anything more than a few centimetres.
"There is no way to go without optics. There is no way copper can do this," Ledentsov said.
While there are currently technologies that achieve 40 Gbit/s by using as many as 12 transmitters and 12 receivers, it's clear that replacing this with just one of each is preferable. "Serial transmission is the lowest cost, lowest power consumption solution," Ledentsov asserted.
VI Systems is currently taking orders for products based on the 20 Gbit/s technology it presented at Photonics West.
The company operates a fabless model, with its MBE-grown devices produced by foundries, and processing and characterization performed by the Technical University of Berlin.
• QD Laser, Inc, the Japanese quantum dot Fabry-Perot (FP) laser producer has gained ¥700 million ($7.8 million) to enhance its production capabilities and R&D activities.
The venture funding round was led by Mizuho Capital with Tokyo Leasing joining as a new investor, and founders Fujitsu and Mitsui also participating.