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Comnet SkyLaser

by Benchmark

Connectivity remains one of the developing areas in security system design, and increasingly installers and integrators are looking for increased flexibility when implementing a system topology. While wireless has traditionally used for last-mile scenarios, the potential from such systems is increasing all the time. ComNet now offers SkyLaser, which delivers enhanced performance for those seeking 1Gbps links.

What is it?
Many systems can utilise symmetrical 1Gbps Ethernet signals over copper or optical fibre, forming the backbone of networked video surveillance systems. The approach typically requires redundant networks in case any failure in the topology results in a total system failure.

With wireless networks, the creation of high speed symmetrical links is not that simple. There are inherent problems with sending high bandwidth electromagnetic signals wirelessly, and many microwave systems will not support more than 400Mbps of symmetrical data. Add to that latency and variability, plus the feasibility of building redundant networks from microwave based technology, and the solution can become very expensive.

As a result, the company has launched a Free Space Optical (FSO) range to provide high bandwidth wireless connectivity enabling networks to be built in a similar way to cabled solutions. The result is the SkyLaser range.

How does it work?
The SkyLaser system is claimed to deliver the bandwidth of fibre optics with the simplicity of installation associated with wireless products. The system does not require any licences and represents a credible alternative to leased lines. Performance is enhanced as the units are immune to RF interference. There are two versions with differing ranges: 600 metres and 1500 metres.

Laser light from a transmitter is sent to a receiving unit and the link is created. By having transmitting and receiving (transceiver) devices at both ends, a duplex link can be supported, and a 1Gbps symmetrical Ethernet channel is operational through the air. The Lasers are VCSEL (vertical cavity surface emitting laser), offering high optical power levels, efficient operation and high reliability. The products operate at 850nm, and so are eye-safe.

As the laser signal propagates through the air the beam diverges, and so at distances beyond 200 metres the laser signals have effectively overlapped, providing redundancy in the system with respect to the transmitting optics. Signals are received though an aperture in the centre of the front window and focused to the photodiode.

What about alignment?
The divergence of light makes link alignment easier at longer lengths as the received signals cover an area that the receiving unit simply needs to be within. At shorter distances it may be that the Lasers have not diverged, so a single Laser from the source would be used to align with the receiving aperture at the remote end.

Physical alignment is made through a sighting scope supplied with every device, with success being achieved by simply positioning the crosshairs of the sighting scope on to the front window of the far end device. A LED bar graph display shows the alignment quality and integral stepper motors can be used for fine tuning. No Fresnel zone is created, so links can run in close proximity to solid objects without noise being introduced.


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