RONJA

RONJA (Reasonable Optical Near Joint Access) is a free-space optical communication system originating in the Czech Republic, developed by Karel Kulhavý of Twibright Labs. It transmits data wirelessly using beams of light. Ronja can be used to create a 10 Mbit/s full duplex Ethernet point-to-point link. It has been estimated that 1000 to 2000 links have been built worldwide

The range of the basic configuration is 1.4 km (0.87 mi). The device consists of a receiver and transmitter pipe (optical head) mounted on a sturdy adjustable holder. Two coaxial cables are used to connect the rooftop installation with a protocol translator installed in the house near a computer or switch. The range can be extended to 1.9 km (1.2 mi) by doubling or tripling the transmitter pipe.

Building instructions, blueprints, and schematics are published under the GNU Free Documentation Licence. Only free software tools are used in the development. The author calls this level of freedom "User Controlled Technology". Ronja is a project of Twibright Labs.

The building instructions are written with an inexperienced builder in mind. Basic operations like drilling, soldering etc., are explained. Several techniques - drilling templates, detailed checks after soldering, testing procedures - are employed to minimize errors at critical places and help to speed up work. Printed circuit boards are downloadable ready for manufacture, with instructions for the fabhouse. People with no previous experience with building electronics have reported on the mailing list that the device ran on the first try.

Around 153 installations worldwide have been registered into a gallery.

By definition, clear visibility between the transmitter and receiver is essential. If the beam is obscured in any way, the link will stop working. Typically, problems may occur during conditions of snow or dense fog.

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