Plastic Optical Fiber (POF)

Plastic optical fiber (POF) has always been "lurking in the background" in fiber optics; a specialty fiber useful for illumination and low speed short data links.



Most POF is large core step-index multimode fiber with a typical diameter of 1 mm, mostly core with a thin cladding. This large core size makes it easy to couple light from LED sources and connectors do not need to be high precision. As a result, typical connector costs are 10-20% as much as for glass fibers and termination may be as easy as cutting with a razor blade and no or minimal polishing. Being plastic, its also rugged and easy to install without fear of damage.

From an optical standpoint, conventional POF is much lower in performance than glass fiber - higher attenuation and lower bandwidth. It has a typical loss of 0.15-0.2 dB per meter at 650 nm and its bandwidth is limited by its large NA and step-index profile. However, it is adequate for running short links, such as inside of instruments or within a room for desktop connections up to 50 meters. And of course in automobiles, where it has gained a foothold with the new MOST and Flexray networks.

But recent developments in POF technology have led to low NA POF and graded index POF that offer higher bandwidth and graded-index POF (GI-POF) that combines the higher bandwidth of graded-index fiber with the low cost of POF. Current designs of GI-POF offer up to 2 Ghz bandwidth at distances of 100 meters, but manufacturing problems have hampered its adoption. Recent developments in a new laser (VCSEL of vertical cavity surface emitting laser) promise extremely low cost, high power, high speed transmitters.

POF's low cost, easy termination (use a razor blade) and inexpensive transmitters and receivers make it ideal for many consumer applications. If you have consumer audio equipment or a modern TV, it likely has a digital optical port that uses POF. The fact that these links so widely used indicates how inexpensive a POF link can be.

POF is popular as digital links in industrial machinery like robots where distances are short and speeeds are low. Its flexibility is also good for applications like robotic arms used in assembly.

POF is also used in automotive applications. MOST is a standard widely used for high bandwidth automotive multimedia applications and Flexray is used in critical timing applications like airbag deployment.

But the majority of applications for POF are for lighting. It can be used to remotely illuminate objects that are sensitive to strong light or heat from traditional light sources, making it popular for museum lighting of small delicate objects. POF is also popular for lighting in areas that are electrically dangerous like swimming pools. Another popular application is creating starfield ceilings.