Standard polymer optical fibres (POFs) are used in various fields of applications. As a medium for communication systems, polymer materials offer many advantages in comparison with copper or glass [1,2]. They feature lower weight and the non-existing susceptibility to any kind of electromagnetic interference. Compared with glass fibres (GOF), POFs feature easy and economical processing and are more flexible for optical connections. For these reasons POFs are applied for short-distance communication in the automotive sector and replace copper step by step. Another sector where POFs are applied for communication is in the house and are established there for PC-Data, VoIP and IP-TV, so called "Triple Play". All these applications mentioned before have high demand on bandwidth. Standard communication via POF is limited in bandwidth, because only one wavelength is used to carry information over the fibre. The only way to increase bandwidth is to change the bit rate. Hence new ways have to research to break through this limitation. One promising attempt is to use wavelength division multiplexing (WDM), which is widely used in long distance GOF systems: instead of one wavelength many wavelengths carry information over one single fibre[3,4]. For that reason there are two new ways to advanced data capacity: first the optical bandwidth and second the channel density. Therefore in WDM the product of these three values deter-mine the data capacity. So WDM over POF has the power to break through this limitation. For the use of this technique two more new elements have to be introduced in the communication system: first a multiplexer (MUX) to combine all carried wavelength in one fibre and second a Demultiplexer (DEMUX), which separates the light in its monochromatic parts. There are several demultiplexers available on the market, which are afflicted with certain disadvantages and therefore not applicable to use them in the mentioned applications. Hence a new demultiplexer with new fabrication technology is needed to satisfy the demands. The design and the development of the demultiplexer will be shown in detail. The development is done by means of an optical simulation program. This is a fast and inexpensive way to obtain satisfying results. The MUX/DEMUX device separates the monochromatic parts of light by means of a high dispersive grating on a mirror. The shape of the mirror and the parameters of the grating have to be developed and optimized in several steps to meet the demands. These process steps will be presented. One of the last steps is to produce the device in injection moulding technology. Thus it can be manufactured in high quantities for low price and so it is ready for use in mass market.
