Researchers at NASA’s Langley Research Center were recently alarmed when they discovered how Radio Frequency Interference (RFI) and Electromagnetic Interference (EMI) affect flight navigation and communication systems.
They found that wide band signals could suddenly silence radios and lead radio navigation systems to give erroneous readings. Distance measuring systems, for example, common equipment on airplanes, are influenced by RFI and EMI, which causes distance readings to be off by miles.
Devices and systems that EMI affects include motor drives, IGBT power circuits, SCR trigger circuits, power contactors, AC/DC power inverters, and power distribution systems. These devices radiate large electric and magnetic fields creating noisy conditions. The central problem is the traditional use of copper cables that act like antenna that pick up stray electromagnetic fields.
Langley researchers are now replacing copper with Polymer Optical Fiber (POF) in industrial RS-485 and fast ethernet communication installations. POF made from glass and plastic are dielectric and do not pick up EMI fields.
Resistance to the use of POF has centered around cost concerns and a greater familiarity with copper. In fact, copper wiring is now more expensive than POF and harder to deal with as copper often requires grounding rules to avoid ground-loop interference and termination resistors to avoid reflections.
POF installations are in general simpler and easier than copper installations although there is a learning curve. Today, vendors offer connectorless and crimpless connectors to make termination simpler and also provide snap together cables and equipment that reduce labor costs and installation errors.
Finally, fiber transmits data significantly faster over longer distances, has a smaller diameter and weight, uses less power, is better for data and illumination transmission, and provides less signal degradation than copper cables.
