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Optical simulation software based on the ray tracing method offers easy and fast results in imaging optics. This method
can also be applied in other fields of light propagation. In fiber optics BPM software is usually used to research the
guidance of light in the inner fiber. This is suitable for fibers with small core diameters such as single mode or multi
mode glass fibers. For short distance communications polymer optical fibers (POFs) are gradually gaining in importance.
This kind of fiber offers a larger core diameter, e.g. the step index POF features a core diameter of 980 μm.
Consequently, POFs have a large number of modes (<3 million modes) and BPM is not suitable anymore. Instead, ray
tracing could be used. This simulation method is not only applicable for the fiber itself but also for the key components
of a complete POF network, e.g. couplers or other key-elements of the transmission line. In this paper a demultiplexer
designed and developed by means of ray tracing is presented. Compared to the classical optical design, requirements for
optimal design differ particularly with regard to minimize the insertion loss. In other words, the complete light has to be
transmitted to guarantee a good transmission. The basis of the presented key element is a wavelength division multiplex
device using a Rowland spectrometer set-up. In this approach the input fiber carries multiple wavelengths, which will be
divided into multiple output fibers that transmit only one wavelength. To adapt the basic set-up to POF, the guidance of
light in this element has to be changed fundamentally. Here, a monolithic approach is presented with a blazed grating
using an aspheric mirror to minimize most of the aberrations. In the simulations the POF is represented by an area light
source, while the grating is analyzed for different orders and the highest possible efficiency. In general, the element
should be designed in a way that it can be produced with a mass production technology like injection molding and hot
embossing in order to offer a reasonable price less than 10 EUR. The paper will give an introduction to POF, its
application arrays, and will step by step describe the development of the demultiplexer by means of ray tracing
simulations.
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