Home networks based on graded-index plastic optical fiber (GI-POFs) can have high data transmission rates in the gigabits/second range. Conventional fibers for these networks are based on poly(methylmethacrylate) (PMMA), which has a transmission peak at 650 nm and a much lower transmission at 670–680 nm. However, vertical-cavity surface-emitting lasers (VCSELs) emitting at 650 nm are lower in power and less thermally stable than those emitting in the 670–680 nm range. Now, researchers at Keio University (Kawasaki and Yokohama, Japan) have developed a GI-POF based on polystyrene, which has higher transmission at the longer wavelengths, allowing use of the more-optimum VCSELs.
The preform was fabricated via the rod-in-tube method and drawn down to core and cladding diameters of 400 and 700 μm, respectively. The measured refractive-index profile (red line) closely fits an approximation fit to a power law with an exponent of 3.3. One requirement for a home GI-POF system is that the fiber attenuation be less than 200 dB/km. The polystyrene fiber has a low loss of 166–193 dB/km at 670–680 nm wavelengths, much lower than the approximately 270 dB/km for a PMMA fiber. Tests showed a bandwidth for a 50 m stretch of polystyrene fiber at 670–680 nm to be 4.4 GHz. In addition, the fiber material is a commodity resin and thus very inexpensive. Contact Yasuhiro Koike at [email protected].
