Chainflex cables

Example 5: tested!Dispersion and attenuationPlastic fiber-optic cables in Energy Chains ®Plastic fiber-optic cables have been introduced for datatransmission in industrial applications due to their excellentinterference-proof properties against electro-magnetic fieldsand further advantages such as the possibility of reducingdimensions and weights. The application as flexible linklines particularly in Energy supply chains places highdemands on plastic fiber-optic cables.The most important characteristic values of a fiber-opticcable are dispersion and attenuation. Dispersion is the termused to describe the scattering of the travel time of the signalin the fiber-optic cable. In plastic fiber-optic cables this isessentially caused by the mode dispersion, which arisesfrom the different travel times of individual light beams.Dispersion determines important transmission propertiessuch as bandwidth, cut-off frequency or maximum bit rate.Significant changes in dispersion could not be ascertainedin any of the investigations carried out.The industrial application of igus Chainflex ® -lines with plasticfiber-optic cables in supply chains for example is thereforeunproblematic with regard to changes in dispersion.The second important characteristic property, attenuation,determines the maximum possible length of a transmissionpath.The attenuation of a plastic fiber, like that of the glass fiber,is also strongly dependent on the wavelength of the lightused. For this reason all the investigations were carried outwith a wavelength of 666nm.Depending on the output of the transmitter and the sensitivityof the receiver the operator has a certain "attenuationbudget" available for the complete transmission pathincluding all junction and transition regions. This attenuationbudget (typical value approx. 20dB) must not be exceededif a secure transmission of the data is to be guaranteed.For this reason it is of great interest to the user to knowwhether and to what extent increases in attenuation are tobe expected for his particular application so that these canbe taken into account in the compilation of his own attenuationbudget.In addition to continuous bending stress, which is typicalfor operation in an Energy chain, further mechanical stressesthat can occur during installation or operation must be takeninto account. Thus, for example, relatively large tensile forcescan occur when integrating the line into an Energy chain.The fixing of the lines at the ends of the energy chain usingcable clamps leads to permanent transverse loads.The test of the behaviour under transverse load is carriedout following DIN VDE 0472, Part 223. Since the cableclamps only exercise pressure in an area covering a fewcentimetres, increases in attenuation are relatively low.Attenuation under tensile load depends to a great extentof course on the composition of the line. Lines with integratedcopper conductors or strain relief elements do notreveal a noticeable increase in attenuation until very muchgreater tensile forces are applied than is the case with purefiber-optic cables.32