reliable and feasible technology for more than one gigabit over standard SI-POF

WHAT IS PLASTIC OPTICAL FIBER (POF)?

GOF

The fibers commonly used for communications are the Glass Optical Fibers (GOF). These fibers are well suited for data transmission due to their characteristics of very high bandwidth and very low attenuation.

The are two kinds of GOF:  Single Mode (SM) GOF and Multi Mode (MM) GOF.

SM-GOF are characterized by only one mode of the light is excited and their refractive index remains constant in the core, hence they are Step-Index (SI) fibers. The SM-GOF have a very small core with diameter of 8 micrometers (μm) and a cladding with a diameter of 125 μm. These fibers are used for high speed data transmission over very long distances links (kilometers).

MM-GOF have a higher core diameter of 50 μm, so they can transmit several modes. In order to reduce the differential modal delay and provide a high bandwidth they are manufactured with a graded distribution of the refractive index along the core. Therefore, these fibers are Graded-Index (GI) fibers. The main application is the interconnection in data-centers, office-LAN, massive data storage, etc.

Since GOF have a very small diameter and low numerical aperture (NA), which relates with the maximum acceptance angle of light, its installation requires of special and expensive connectors, tools and skilled installers.

POF

On the other hand we have Plastic Optical Fiber (POF), based on Poly Methyl Methacrylate (PMMA), with a large core diameter (~1 mm) and high numerical aperture (NA 0.3 - 0.5). POF can be deployed by a professional or do-it-yourself installer using basic tools, such as a scissor, and inexpensive plastic connectors. It is immune to misalignment and strong vibrations, so it can be installed for industrial and automotive environments without loss of communication capacity.

Because it is optical, POF is completely immune to electrical noise. That means existing copper wiring will not interfere with data passing through POF so it can even be installed next to electrical cabling. POF, connectors, and optoelectronics are low-cost consumer parts which is ideal for installers who save on cable costs and installation, testing and maintenance time.

POF has been widely used in over 20 million cars for infotainment networks, it is the global standard for high speed in-car networks - Media Oriented Systems Transport (MOST).

These fibers have been used in low performance (from 1 to hundreds Mbps) and short distance applications (less than 100 meters), because they have a low bandwidth-length product (~40MHz x 100m for standard SI-POF NA 0.5) and a high attenuation (~150 dB/Km at a wavelength of 650 nm).

As communication medium, POF shows a high chromatic dispersion and very high modal dispersion due to its important Differential Mode Delay (DMD) and Differential Mode Attenuation (DMA). Furthermore, the large area photo-diodes required for coupling with the fiber have a limited bandwidth.

The cheapest and most used POF is the standard SI-POF with NA 0.5. However, there are also low-NA SI-POF (NA 0.3) for higher data-rates, and recently PMMA GI-POF has been manufactured, with a bandwidth-length product near to 1 GHz x 100m.

PMMA has several attenuation windows that enable POF to be used with different visible light sources from blue to red Light Emitting Diodes (LED) or red Lasers Diodes (LD).

Ⓒ2010 Knowledge Development for POF S.A.