Developing power-over-fiber communications cable

Sometimes total electrical isolation is a good thing - and that's the idea behind a power-over-fibre (PoF) communications cable being developed by engineers at Sandia National Laboratories.

Titus Appel, left, and Steve Sanderson of Sandia National Laboratories' mobility analysis and technical assessment division display a first-generation power-over-fiber cable that converts a signal from electrical-to-optical-to-electrical, thus emulating an electrical cable in total isolation.

It's common to isolate communications between systems or devices by using fiber optic cables, said Steve Sanderson of Sandia's mobility analysis and technical assessment division. But when power also is required, sending it down a copper wire can at times be a safety issue, and substituting it with battery power may not be suitable or practical, he said.

Sanderson, Titus Appel and Walter Wrye, a former Sandia intern, are co-inventors of a hybrid cable design that uses fibre to send and regulate optical power to the communications electronics integral to the cable. A patent is pending on the design.

The developers envision their cable replacing existing copper cables in applications related to safety, such as security, explosives, explosion-proof devices, aviation and medical devices.
 
''The PoF cable has power limitations,'' Sanderson said. ''It's not to be construed as a means to power your house, for example, or handle the high speeds of a computer network.
''But because there are growing needs of low-power sensor/control applications related to safety, having convenient optically generated power available is a tremendous benefit.''

The PoF cable ends resemble a typical copper electrical cable with pin and socket connectors. However, optical interface circuits integrated into the connector housing, called a backshell, provide fiber optic transmission of both data communications and optical power.

To conserve energy, optical power is delivered only on demand, Sanderson said.
 
''The key issue here is to maintain total electrical isolation from any stray electrical energy and high-voltage electrical surges caused by such things as lightning strikes,'' he said.