Since the beginning of February, Smartoptics has been participating in a research project whose mission is to develop new optical wireless technology solutions for 100Gbps data transmission in the air. The project is run by RISE Acreo, a Swedish research institute within electronics, optics and communication technologies, in cooperation with Norwegian Polewall, a provider of low-cost point-to-point optical wireless links.

In a trial set-up at Acreo’s research facilities in Kista outside of Stockholm, Smartoptics’ recently launched DCP-101 100G transponder is used together with CFP transceivers to create a 100 Gbps DWDM signal. But rather than relying on physical fiber for transmitting the DWDM signal between sites, a connection is created through the air using Polewall’s optical wireless technology.

“Smartoptics is generally recognized as offering a very flexible platform for optical networking, with applications for all types of scenarios. 100Gbps connectivity through the air has not been demonstrated before this trial, at least not with commercially available products. We are proud to be part of that milestone together with Acreo and Polewall,” explains Fredrik Larsson, Optical Transmission Specialist at Smartoptics.

New opportunities for high-capacity connectivity with airborne DWDM

“As one of Europe’s top research institutes, Acreo continuously looks for new ICT solutions that address both existing and future demands and that help create sustainable growth in industry and society. This project, which explores new ways to provide optical connectivity through the air, is exactly in line with this mission,” explains Evgeny Vanin, Senior Scientist at RISE Acreo.

The international interest in optical wireless communication systems, commonly also referred to as free-space optical communication, is growing quickly. While the basic technologies have been available for quite some time, solutions have traditionally relied on high-power lasers, intended for medium- to long-range applications, to transmit signals. Because of this, both the price and physical size of the solutions have prevented mass market deployment.

“In recent years, we have seen remarkable advances in terms of price reductions in the component market. This is now opening up for short- to medium-range optical wireless communication applications at lower power and far lower cost,” explains Vanin.

The initial scope: secure airport communication

The initial objective of the research project is to develop and demonstrate solutions for reliable, secure and fast data connectivity between aircrafts and ground terminals at airports. Due to, both, practical and safety concerns, data transmission is restricted while the airplane is airborne. The bulk of data transfer for information like cockpit flight data and entertainment system content must take place during the short on-ground window, requiring high transfer speeds.

“Through the trials, we have succeeded in showing that our solution for wireless optical networking meets all the requirements for energy efficiency, reliability, security, and bandwidth demanded by airlines, airport owners and authorities” explains Vanin.

Other applications for free-space optical solutions

But the interest in optical wireless solutions doesn’t just stop at airport communication. Free-space optical solutions could be deployed in a wide range of scenarios where fixed fiber is not considered an option due to complexity or cost. The nonintrusive optical wireless solution also provides the perfect fit for other locations where radio wave pollution is prohibited, such as in hospitals and industrial facilities.

“The solution can be used to provide wireless optical connectivity to our homes, as an alternative to fixed fiber. Creating a free-space optical communication link for high-speed internet access over distances up to 250 meters will provide significant cost savings compared to deploying traditional fiber to the home. In this way, wireless optical solutions can be used to significantly increase the number of households that will actually gain access to the high-capacity broadband fiber network,” concludes Jan Eide, founder and CEO at Polewall.

Technical facts

100Gbps connectivity has been tested, both in the 1300 nm band and in the 1550 nm band, using an incoherent 4x25Gbps and coherent DP-QPSK signals, respectively.

Over a 40 meter FSO link the transmission in the 1550 nm band has been verified at 9 dB loss thanks to the Polewall Pole sway compensation system.

The system design has been optimized for signal transmission at 1550nm. The total estimated power budget of the coherent 100Gbps FSO link in this band is 40dB. This means that the system is estimated to reach 250m in the worst imaginable weather conditions with sick fog leading to optical attenuation of 100 dB/km.

Even in the 1300 nm band, far from the optimum design wavelength, the total power budget of the 100Gbps FSO link is 28dB. This means that the system is estimated to reach 100 m with 1300nm signals in the sick fog conditions typical for Europe.

Transmission latency is below 4 μs, which allows the solution to truly act as an invisible fiber in the air.