2. Plastic optical fiber (POF) is a low-cost alternative to standard fiber optic

Question

2. Plastic optical fiber (POF) is a low-cost alternative to standard fiber optic cable. The core is made of either Poly(methyl methacrylate) or Polystyrene and the cladding is usually made of silicone resin. Typically POFs have a large core size, making them easy and cheap to connectorize and couple to laser diodes but they have a low bandwidth-distance product and high attenuation. a. The refractive indices of Polystyrene and silicon resin are about 1.59 and 1.46, respectively. Find the critical angle and numerical aperture of a POF made with these materials. How do these values compare with conventional fiber? b. Search the web and find typical values for the bandwidth-distance product and attenuation of step index plastic optical fiber. How do they compare with typical values for standard multimode fiber? c. Search the web and find a typical cost for 100 ft. of plastic optical fiber and compare it to the cost of conventional fiber. (If you get a cost for connectorized fiber, indicate what kind of connector you picked.)

Explanation / Answer

First of all refractive index of core is always greater than cladding.

Let x be the critical angle. Then

sin x = 1.46/1.59

sin x = 0.91823899371

So,

x = 66.66997763254980514584277813232 (Critical Angle)

NA = ref ind (core) * cos x

NA = 1.59 * cos (66.66997763254980514584277813232)

NA = 1.59 * 0.3960267041885516341346873937889

NA = 0.62968245965979709827415295612435

In coventional optical fiber critical angle is around 60-75.

Average cost of optical fiber. Fiber Cost = 5,000 ft at $5.87 per foot

Cost of plastic fiber = around $90 per 100 ft.

PMMA-POF has shown a bandwidth-distance product of. 0.5 GHz km at the 650 nm wavelength.

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