Friday, August 12, 2011

Power over Fiber

The term power over fiber or photonic power implies that the optical power is generated from electric power with a laser diode and at the end converted back to electrical power for some electronic device. That conversion can be done with a photovoltaic cell, i.e., a semiconductor device based on a material such as gallium arsenide, indium phosphide, or indium gallium arsenide. A typical system contains a laser diode emitting a few watts of optical power, a multimode fiber of a few hundred meters length, and a photovoltaic cell with an active area of several square millimeters.
Glass fibers (or possibly plastic fibers), being electrically insulating, can be installed where high electric voltages exists. For example, a fiber can transmit power for a current transducer in a high-voltage transmission line. Such current sensors can replace bulky transformer systems.
The insulating property is also useful when a device (e.g. some radio signal receiver) is connected to an antenna, which could be hit by lightning. There is then no risk that the lightning is transmitted via the cable.
Optical delivery of power avoids any sensitivity to strong magnetic fields (e.g. in magnetic resonance imaging) and to electromagnetic interference. Conversely, no electromagnetic radiation can be emitted, which might disturb other devices.
There is no risk that explosive materials (e.g. in a fuel tank of an airplane) can be ignited, as could occur e.g. via an electric spark.
In a system for optical fiber communications, there may be spare fibers which can be used for transmitting power when an electrical connection does not exist.
A fiber can have a far lower weight than an electrical cable, and may tolerate higher temperatures.
The same fiber may be used to send back data e.g. from a sensor, using some other wavelength channel.

Therefore, a number of applications can be envisaged in areas such as industrial sensors, aerospace, and optical communications.

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