Plastic Optical Fiber (POF) is a unique member of the optical fiber family. POF is made of Poly Methyl Methacrylate (PMMA), with a large core diameter (~1 mm) and high numerical aperture (NA 0.3 – 0.5).
The following figure shows a comparison of a typical POF geometry compared to another well known optical fiber, the Multi Mode Glass Optical Fiber (MM-GOF). It is easy to appreciate the huge core diameter (20x) as well as the relativelly thin clad of POF compared to MM-GOF.
Advantages of POF
Thanks to its huge core diameter, POF is immune to misalignments and strong vibrations, and can be installed in rugged industrial and automotive environments without any loss of communication capacity. POF is ideally suited for deployment either by a professional installer or a do-it-yourself installer using basic tools, such as a pair of scissors or a cutter, and inexpensive plastic connectors.
An optical transmission media, POF is completely immune to electrical noise. For example, existing copper wire installations will not interfere with data passing through POF lines, so POF can be installed anywhere next to electrical cabling. POF and its connectors and optoelectronics are low cost consumer parts that enable installers to save on cable costs and installation, as well as testing and maintenance time.
Widely used in over 20 million cars for infotainment networks, POF is part of the automotive standard, MOST©(Media Oriented Systems Transport) for high-speed data transmission in car networks.
The Evolution of POF
POF has been used in low-speed (from one to hundreds Mbps) and short-distance applications (less than 100 meters), as it is a low bandwidth-length product (~40MHz x 100m for standard SI-POF NA 0.5) with high attenuation (~180 dB/Km for red light sources).
On the figure we can see as an example the 3dB bandwidth (MHz) vs. length (m) and bandwidth product (MHz x 100m) vs. length (m)(POF Eska GH4001, Red LED UMD NA 0.5, 650 nm, Δλ=30 nm)
As a data transmission media, POF shows a high chromatic and modal dispersion due to its important Differential Mode Delay (DMD) and Differential Mode Attenuation (DMA). Furthermore, the large area photo-diodes required for coupling the light into the fiber have a limited bandwidth.
The figure shows a typical attenuation (dB) vs. length (m) and attenuation per length (dB/m) vs. length (m) characteristics. (POF Eska GH4001, Red LED UMD NA 0.5, 650 nm, Δλ=30 nm)
The least expensive and most popular POF in the market is the standard SI-POF NA 0.5, with low-NA SI-POF (NA 0.3) available for higher data-rates. Recently PMMA GI-POF has been launched into the market with a bandwidth-length product near to 1 GHz x 100m. PMMA has several attenuation windows that enable it to be used with different visible light sources that go from the blue to red, and a wide variety of devices like Light Emitting Diodes (LED) or Laser Diodes (LD).
A plot of typical attenuation profile vs. wavelength and transmission windows for standard SI-POF NA 0.5 and GI-POF (OM-Giga) is shown in the figure