Camera is running with light as electricity

First purely optically operated camera network presented

The video camera (left) is connected to a PC via a fiber optic cable. The camera does not need a battery, nor does it need to be connected to the mains. © Karlsruhe Institute of Technology
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A camera network that works with light instead of electricity and uses a minimum of energy has now been developed by researchers at the University of Karlsruhe. The innovation is supplied with power via fiber optic cables and is of particular interest for applications in safety technology.

At first glance, one might think that it is a normal video camera that delivers 15 color images per second in VGA resolution (640 x 480 pixels). At second glance, however, you can see that the self-made video camera is powered neither by a battery nor a battery and no power cable. The only thing that connects the camera to the base station is a 200 meter long, hair-thin fiber optic cable that can transmit multiple signals simultaneously at different wavelengths. One wavelength is used to power the camera; the other wavelength is for data communication and is used to return the image signal to the base station.

Light as a carrier of data and energy

The camera is a true power-saving miracle: it only needs 100 milliwatts, so that CMOS sensor, electronics and transmit laser can deliver the video data stream of 100 megabits per second to the base station. This happens at the wavelength 1310 nanometers. With a 400 mW strong light signal of wavelength 810 nanometers, however, the video camera is the required energy supplied; a photodiode converts the light into electricity. Both data channels are bundled in a 62.5 micron standard multimode fiber. At the base station, a computer receives the image signal and transmits the images to the Internet.

The development of the purely optically operated camera network was a real team effort, as Professor Leuthold of the University of Karlsruhe explains. The Institute for Information Processing Technology contributed electronics under the direction of Professor Becker. The highly sensitive photodiode for converting the laser light into electrical energy was developed at the Fraunhofer Institute for Solar Energy Systems in Freiburg, and the Institute for High Frequency Technology and Quantum Electronics headed by Professor Leuthold and Professor Wolfgang Freude was responsible for optical communication technology.

The team recently presented the innovation at the "European Conference on Optical Communications" (ECOC) in Berlin in front of about 1, 200 scientists and engineers from 60 countries. Organized annually in changing locations, the conference is Europe's largest on optical communications and is considered one of the two major conferences in the field. Only selected works, which represent the newest state of the art, are admitted for the presentation. display

Hair-thin glass fibers are enough

As Leuthold points out, the light-supplied camera network is of particular interest for applications in security technology, especially if video cameras are to be installed subsequently in rooms. "Instead of tearing up the walls to lay power cables, you only need to install hair-thin fiber optic cables that are no longer visible with paint overshadowed." The optical power supply is also particularly suitable for use in environments with strong electromagnetic fields or danger of explosion.

(Karlsruhe Institute of Technology, 22.10.2007 - NPO)