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VI Systems' 850 nm VCSEL reaches 40 Gbit/s

High-speed single laser could provide a cheaper solution than parallel optics for fibre-optic cabling in data centres

VI-Systems GmbH a leader in optical components for high-speed optical data networks announces the immediate availability of 850 nm-range optical components suitable for 40 Gb/s error free data transmission.

The 40G vertical cavity surface emitting lasers (VCSELs) and PIN photodetectors are presently available as chips and as multimode fiber-coupled modules.

“High speed optical components are of extreme importance for the future development of local and storage area networks, as well as for applications in optical fiber cables for industrial and consumer applications,” notes Nikolay Ledentsov, CEO of VI-Systems.

Electrical interfaces for serial transmission at speeds beyond 10 Gb/s are being standardized for a variety of applications including for example (with an expected data-rate, and implementation date if known): Fibre Channel FC16G (17 Gb/s, 2009); Infiniband (20 Gb/s, 2011); FC32G (34 Gb/s, 2012); CEI-25 (25 and 28 Gb/s), USB 4.0 (expected to be 20-60 Gb/s), and many others. Within this range the maximum copper link length is limited by only a few centimeters to meters, depending on the particular transmission speed and the form factor of the cables used. Consequently, one must apply fiber optics to extend the link length to the required distance typically within 0.1-100 meters. The optical transceiver should preferably be capable of operating at the same or higher transmission speed. Nikolay Ledentsov adds: “Going to parallel optical links starting from a higher serial speed electrical interface using time division demultiplexing is certainly not a good idea. This would require twice the number of CMOS drivers and amplifiers, and, most importantly, integrated circuits for demultiplexing and multiplexing at both the transmitting and the receiving ends of the link. The latter is prohibitively power-consuming and complex.”

In addition to matching the ever growing high serial transmission speed of electrical interfaces (a 4-fold increase in speed each 5 years that is roughly a Moore’s Law for data communications) that is primarily driven by an increase in microprocessor bandwidth and silicon scaling, there are crucial advantages for medium speed applications that also employ optical transmitters and receivers, for example at 5 and 10 Gb/s. First, a much shorter rise time of the transmitter enables a much longer transmission distance before the neighboring signals merge due to the fiber’s intrinsic modal and wavelength dispersions. Furthermore, ultrahigh-speed components are advantageous because of their capacitance, which is much lower than the capacitance typically found in traditional devices. Consequently, the power dissipation of the modulator and trans-impedance amplifier integrated circuits (ICs) can be dramatically reduced. It is the CMOS IC power consumption which defines the power dissipation of the transceiver module and, consequently, its form factor. Modern parallel optical links based on fiber ribbons or polymer waveguides require 24 channels per single transceiver (12 for transmit and 12 for receive), and thus the issue of power dissipation is of particular importance.

The company’s CTO James Lott adds; “Making available optical components that are suitable for high speed transmission and that operate at moderate current densities of 10 kA/cm2 or less has always been quite a challenge. Our most recent tests on multimode fiber transmission links equipped with VIS devices at both ends, have resulted in error free transmission at up to 40 Gb/s and are limited only by the overall BERT measurement system. The time needed for a rectangular signal to rise from the 20% to the 80% level after passing through all the components of the optical link test system including the VCSEL is 15 to 16 ps. We have determined that the deconvoluted VCSEL rise time is a mere 9 ps or less. Moreover it is particularly important to underline that there is essentially no temperature dependence in our VCSEL’s rise time up to a fixed substrate temperature of 100oC. Thus, our components are not only suitable for high-speed systems design and evaluation, and for scientific research, but also for the development of practical fiber optic systems capable of optical data transmission rates of up to 40 Gb/s and likely, at even higher rates.”

Vitaly Shchukin, Chief Scientific Officer of the company says; “Advancement in science and technology is limitless. We are happy to bring these unique prototype transmitters and detectors to our customers and partners. Meanwhile, we are already half-way towards our next strategic goal; achieving 60 to 100 GHz -3dB optical bandwidth via vertical integration of the VCSEL and modulator sections. The reflectance of the top Bragg mirror is electro-optically modulated, the Bragg mirror thus acting as a chopper for the continuous emission from the VCSEL section. Further remarkable reduction in power consumption and cost of the high-speed transmitter using either a VCSEL or a resonant-cavity LED will become possible. Optical modulation with a -3dB bandwidth beyond 30 GHz and up to 100oC has already been demonstrated.”

VI Systems GmbH strongly appreciates support from the Technical University of Berlin, the A. F. Ioffe Institute, and the Scientific-Educational Center of the Russian Academy of Sciences, the latter two both in St. Petersburg and whose participation was enabled by means of research contracts from VI-Systems GmbH. Support from the public-funded projects VISIT (an EU 7th Framework Program), HiTrans (an Investitionsbank Berlin – IBB managed program) and ViSiON (via the German Ministry for Education and Research - BMBF) is also gratefully acknowledged.

About VI-Systems:
Originally spun-out of the Technical University of Berlin and the A. F. Ioffe Physico-Technical Institute in St. Petersburg, Russia, VI-Systems GmbH offers laser and photodetector semiconductor chips and modules for applications in optical data communications and related consumer markets.

Contact VI Systems GmbH
Prof. Dr. Nikolay Ledentsov
Chief Executive Officer and Geschäftsführer
Hardenbergstr. 7
10623 Berlin
phone: +49 30 30 831 43 43
fax: +49 30 30 831 43 59
email: nikolay.ledentsov@v-i-systems.com
web: www.v-i-systems.com

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