WCA March 2018

Lumps and neckdowns are detected by determining the change of light intensity on the sensors. By comparing the amount of light on the first with the second sensor, false detection can be prevented, and thus a reliable detection of faults can be ensured. For example, an optical fibre with a lump runs through the gauge head. Logically, at the position of a lump the optical fibre is bigger. This reduces the amount of light that illuminates the first sensor. At that moment the second sensor still measures the amount of light of the perfect fibre. The differential signal of the two sensors triggers the lump alarm. In combination with a processor system and monitor, all data of the connected gauge heads and lump detectors is processed and visualised numerically and graphically. A special module ensures the continuous control of the diameter by controlling the drawing speed. Alternatively, a hot or cold gauge head is used for controlling (before or after cooling). All measuring devices are equipped with Wi-Fi (WLAN) or with a network interface to enable a network of several lines and even to connect complete production facilities. Furthermore, due to the intelligent recording and analysis of production data, optical fibre manufacturers are able to produce more efficiently and with reproducible quality. High-quality optical fibres that comply with specifications can easily be further processed to optical fibre cables in tight buffering and loose tube lines. Also in these production processes, measuring and control technologies are used for quality control. This assures a perfect fit of optical fibre cables when they are finally installed in subsea cables. Conclusion The integration of measuring, control and testing technology in the optical fibre drawing process ensures a constant high quality of optical fibres. At different production stages, gauge heads and processor systems measure, monitor and control the entire drawing process and thus increase the efficiency of production. With the integration of network interfaces in the technologies, optical fibre manufacturers are able to reproduce quality and to network their manufacturing locations. References [1] http://www.researchandmarkets.com/reports/3807789/global-fiber- optic-connectors-market-2016-2020

Before the acrylate layers are applied onto the fibre during the coating process, the exact measurement of the optical fibre temperature is important. In order to achieve an optimal bonding of the coating and the fibre, the temperature of the fibre should be stable and between 40°C and 75°C. Manufacturers use the inert gas helium for cooling. The amount of helium flow that is used is calculated by means of experience. Often manufacturers use a higher helium flow than necessary to ensure that the fibre is not too hot for the coating. However, helium is a very expensive gas and, therefore, manufacturers of optical fibres want to reduce the usage to a minimum. At this position, a gauge head measures precisely the temperature of the optical fibre after cooling. With the information about the fibre temperature, the optical fibre manufacturer can control the exact amount of helium flow that is needed. To ensure an optimum optical fibre temperature and thus highest process stability during the entire fibre drawing process, the temperature should be measured not only at the hot end, but also at the cold end. After the fibre has received the coating and has gone through the UV curing process, a further laser gauge head measures again the diameter of the optical fibre. After the coating, the diameter usually measures about 250µm. The coating diameter gauge can also provide an online measurement of the eccentricity of the coating with respect to the cladding, the so-called concentricity evaluation (CCE) measurement. The principle is based on the evaluation of the symmetry of the intensity signal captured by the gauge. Perfect symmetry means perfect concentricity and leads to a minimum measurement result. Increased asymmetry leads to an increase of the measurement value, so closed loop control integration is possible. For other scenarios, tolerance levels for warning and alarm outputs can be arbitrarily defined. In addition to diameter, tension, airline, CCE and temperature measurement, lump detectors are used for a continuous quality control in drawing towers. After the coating and at the end of the drawing process, a three-axis testing device reliably detects lumps with a length of 500µm. Due to the growing quality requirements on the optical fibre market, there is even a need for devices with a 100 per cent detection rate for faults starting at a length of 50µm on the optical fibre surface. This performance is achieved by increasing the measurement rate ten times. At the same time, the use of six measuring axes eliminates the shadow regions of the three-axis approach. Lumps and neckdowns are categorised and analysed in regard to height, length, amount and position. The lump detectors feature a double sensor technology which ensures high detection reliability. This technology includes a light source and two light sensors (“double”) arranged in a fixed short distance from each other.

Sikora AG Bruchweide 2 28307 Bremen, Germany Tel : +49 421 48900 0 Fax : +49 421 48900 90 Email : sales@sikora.net Website : www.sikora.net

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Wire & Cable ASIA – March/April 2018