Fiber optic protection against solar panel theft

Comnet fiber optic protection
Comnet fiber optic protection

The production of electric power by photovoltaic solar panels has been steadily expanding in recent years and many systems of panels have been installed everywhere, on roofs and open fields especially. As a consequence of the value and increasing demand of these devices, theft has become an issue, and in spite of some initial protection by CCTV cameras this has so far shown to be ineffective at protecting these high value targets. To protect these installations a simple and reliable fiber optic based protection system has been developed. The schematic seen below in figure 1 shows the basic operation of the applied protection. The ComNet FDC1/2 fiber optic cable break detectors are usually installed in a control room, however they can also be installed in an external anti-tamper protected cabinet as the units are rated to operate under extensive temperatures up to +750C and support a wide DC voltage input. These units also feature ComNet’s exclusive lifetime warranty.

From the unit a fiber optic protective loop is connected, the first end of the dielectric fiber optic cable is connected to the optical transmitter output and the second end to the optical receiver input. Usually the fiber optic cable, housing one single fiber, either singlemode or multimode depending on the distance to cover, has the diameter of 2-2.8mm and includes the tight fiber 0.9mm and a layer of aramidic yarn for mechanical protection, under the external coating which is made of compounds suitable for outdoor installation. Using fiber optic cable in this way offers a cost effective solution without the possibility of the cable being bypassed by use of a jumper as would be possible with a copper cable. The optic connection is made by ST type terminating connectors at the two ends of the cable, coupled to the ST bulkhead adapters of the optical transmitter output and of the optical receiver input. The optical cable is woven through the metal frame of solar panels prior to being connected to the FDC1/2 unit, in such a way that the panel cannot be removed without breaking the optical cable. The FDC1/2 unit constantly monitors the status of the attached fiber optic cable and can trigger an alarm relay output in less than 0.5ms of a cable break or tamper being detected. The relay output can be configured as a normally open or normally closed contact for maximum flexibility. The result of this protection is that by a limited investment it is possible to protect a much larger investment in the complete solar panel power generating system. Additional cost savings can be made by using the FDC2 series which can monitor two independent fiber optic protection loops in a single device allowing for maximum equipment density.


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