Example 10: tested, light in the cold

Light in the cold - igus® Gradient glass fibre cable in a deep-freeze test

The igus® gradient fibre optic cable type CFLG.G has already become the standard in countless crane applications for the reliable transmission of large amounts of data in bus systems at high speeds over long distances. is insensitive to electromagnetic compatibility load and resistant to harsh environmental influences, making it suitable for use together with power supply cables in very long travel distances.

But what about crane systems in regions with extremely low temperatures? Is the maximum possible cable length of several hundred metres reduced by increased attenuation at low temperatures, or does the cable break at extreme temperatures of -40 °C, for example?

The sensitive glass fibres are routed in a gel-filled cavity. How does the gel behave under highly dynamic conditions and what happens when it is switched on again after long periods of inactivity? There were no precise statements on this topic in relevant specialist publications, and little was known about the temperature properties of the gel in particular, so it is part of the igus® philosophy to determine reliable data for applications in e-chain® using our own tests.
A refrigerated container, in which continuous temperatures of -40 °C can be generated, was set up in the igus® test laboratory especially for this task and equipped with a test structure for long travel distances of up to 7 m, a speed of 1.6 m/s and an acceleration of up to 6 m/s2.
The igus® gradient fibre optic cable CFLG.6G.50/125.TC was tested. The cable was tested with a length of approx. 15 m as a loop in a igus® e-chain system® 3500.125.200.0 with a radius of 200 mm.

Different, extreme temperature curves were used to simulate the environmental influences, in particular when cooling down from plus degrees to -40 °C in a very short time during standstill and then restarting the movement.

Even under these operating conditions, the attenuation of the cable should not exceed 3 dB at a wavelength of 850 nm. The maximum attenuation after one million double strokes, which corresponds to approx. 7000 kilometres of running performance, is still well below 3 dB.

The measurements illustrated in the graph show that pronounced temperature fluctuations in combination with the continuous movement in the e-chain® have only a minor effect on the attenuation of the CFLG.6G.TC cable. The recognisably high initial attenuation is due to the connectors used and also reflects reality here, as in practice 90% of automation work is carried out with pluggable fibre optic cables.

The test with the igus®® cable clearly shows that only realistic and very costly tests can provide clarity about the service life of cables.