PLASTIC FIBER

Plastic optical fibre (POF for short) looks like a nylon rope, and is transparent to visible light. It is typically made of Polymethil Metacrilate (PMMA) as the core material, and a fluorinated polymer as the cladding material. Light travels inside the core of a plastic optical fibre; the cladding is the external ‘cover' that generates the guiding effect which forces the light to follow the path of the fibre.

Plastic fiber works like a common optical fiber, but there are some significant differences.



Light Propagation and POF structure




SIZE
PMMA-based POF has a typical outer diameter of 1000µm (i.e. 8 times larger than glass fibre), and a core diameter of 980µm. To obtain a cable, plastic fiber is covered with a 2.2mm-diameter jacket. The material commonly used for jacketing is a high-density PoliEthylene (PE-HD).



Due to its small size, immunity to RF noise and its insulating characteristics, plastic fiber cable fits into conduits, in compliance with international standards (EIA/TIA 569, CENELEC EN 50174-2).







BANDWIDTH
Plastic fiber is transparent at wavelenghts that falls within the visible spectrum. As shown in the picture below, there are three transmission windows, which match the minimum attenuation: 525 nm (green), 575 nm (amber), 650 nm (red).

Plastic fiber spectral attenuation


The most commonly used LEDs and photodiodes work with red light. Luceat is the only company using green light, which allows to reach 400m (1,300 ft) repeater-less transmission.



RELIABILITY
Glass optical fiber is transparent to infrared: devices use infrared lasers, whose output must be perfectly aligned with the fiber's core. Plastic fiber, on the other hand, is transparent to visible light and, thanks to its large core size, works with red or green light LEDs, even in the event of connector misalignement or in the presence of strong vibrations. For this reason plastic fiber is widely used in modern cars.



ELECTRICAL INSULATION
Plastic fiber doesn't conduct current and can be used in flammable or explosive environments, without using EX-D conduits or expensive antideflagration cables.



RESILIENCY
LPlastic fiber tolerates bending radii inferior to 20mm, works from -40°C to +85°C and is guaranteed for a million bending cycles. Plastic fiber doesn't oxidize, withstands humidity and salted atmosphere and warantees link's reliability and more than 20 years of working.
See a case history.


When should plastic fiber be used ?
Why should I use POF?