With light, but without the fiber

British scientists have started work on a new wireless communication system not using ubiquitous radio waves but laser light. The new technology, as usual, has been originally focused on military applications, but it can be quickly implemented in the civilian sector where the demand for broadband solutions is enormous. Until then, however, the scientists have to complete a series of tests. At the moment, they are carrying on research on the transmission of audio signals from drones to a receiving station. As a sample they use the well-known AC/DC song - "Highway to Hell".

Such drones are to use laser communications

 

 

The main problem of unmanned military aircraft (combat or espionage) is the limited range of operation. To increase the range, engineers gradually reduce the weight of the machines, using lighter components and weapons, which translates into a reduction in fuel consumption of their engines and possibility of longer missions.

EADS researchers led by Yoann Thueux are aimed to introduce a new wireless communication system called Dazzle. Comparatively heavy radio equipment is to be replaced by an optoelectronic device reflecting and modulating the laser light emitted from a control station. So, the principle is simple - the laser beam directed at the flying drone is reflected by the machine back to the the station, together with data from sensors and cameras, and the information is received and processed by the station.

The technology is relatively cheap and provides very efficient data transmission, even at data rates up to 1Gbps. What's more - eavesdropping or monitoring of the transmitted data is not possible, which is extremely important for military applications. Currently, the range of the laser link is limited to about 2 km, but it is probably only a temporary inconvenience.

Research on this technology has been ongoing for some time. In 2008, Hani J. Kbashi from the University in Baghdad published a study on theoretical principles, basic calculations and practical solutions for laser equipment for wireless transmission using Intensity Modulation with Direct Detection (IM/ DD). The EADS project is carried out in parallel and employs the same transmission method.

In the near future, wireless optical transmission may revolutionize the market for multimedia services. Extremely broadband characteristics and easy implementation are the factors that can decide on the popularity of this technology. Maybe, in a short time the light will dominate not only in the cable infrastructure but also in wireless systems.

Multimode or single-mode fiber?

In recent years, due to the wide use of fiber optic technology for data transmission, the market has experienced large declines in prices of optical cables and devices, so they have become accessible to many users. They often consider which kind of the cables and equipment will be optimal for their applications, multimode or single-mode?

The best solution is to compare the total prices of the materials and devices for a particular application. Let's think of a 100 Mbps fiber-optic link. This task can be carried out with the use of a pair of media converters. In the case of using multimode fibers, it can be L10021, with range up to 2 km (requires two fibers). Similar pair of media converters for a link with two single-mode fibers is L11041.

Chart showing comparison of costs of fiber optic links based on multimode and single-mode fibers,
taking into account the prices of the mentioned active devices

The pair of media converters for multimode cables costs ca. 20% less than that of the single-mode equivalent. However, due to lower prices of single-mode cables, the difference in total costs is compensated even in the case of comparatively short links (50 meters). The comparison is based on the prices of universal cables with 4 fibers, L7644 and L7354.

The conclusion is that installations based on multimode fibers are cheaper only in the case of very short links, but generally the difference is no so large. Due to larger potential of single-mode fibers, the choice of single-mode solutions is more prospective. Multimode fibers should only be used for very short links, in server rooms etc. Single-mode fibers are basically the only reasonable solution for data transmission over greater distances.