WCA November 2014

Technology news

1m kilometres of optical fibre cables in the ocean

There is a risk during production of the preform that air is being trapped and which, when drawn, becomes stretched air pockets, so called airlines. These airlines damage the quality of the optical fibre and, therefore, must be detected. Sikora has developed the FiberLaser 6003 Airline. With 2,500 measurements per second, this device reliably detects airlines in the fibre with a diameter from 0.5µm. 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 between 40°C and 75°C. Manufacturers use the inert gas helium for cooling. Often manufacturers use more helium than necessary to ensure that the fibre is not too hot for the coating. At this position, Sikora offers the Fiber Laser 6003 Temp, which measures precisely and reliably the temperature of the optical fibre after cooling. With the information about the fibre temperature, the optical fibre manufacturer can use the exact amount of helium that is needed. After the fibre has received the coating and has gone through the UV drying process, a further Fiber Laser 6003 again measures the diameter. After the coating, the diameter usually measures about 250µm. In addition to diameter measurement, lump detectors are used for a continuous quality control in drawing towers. After the coating and at the end of the drawing process, the 3-axis Fiber Lump 6003 reliably measures lumps with a length of 500µm. Due to the growing quality requirements on the optical fibre market, Sikora also offers the Fiber Lump 6003 Micro. The device detects faults from a length of 50µm on the optical fibre surface up to 100 per cent. This performance is achieved by the use of six measuring axes. Sikora AG – Germany Website : www.sikora.net

WHETHER emails, making phone calls, watching television or being online, it is more than likely that the data is being transferred via the international subsea cable network. More than one million kilometres of optical fibre cables are laid in subsea cables in the oceans. Therefore, subsea cables are the main carriers of the international data transfer. The transferred amount of data can be sometimes up to 1 terabit per second, which exceeds the performance of communication satellites. Subsea cables often lie in great water depths of several thousand metres and have to be especially robust as well as built to a high quality standard, due to the extensive technical maintenance. Damages that, for instance, occur because of breakdowns due to contaminated material, can be very costly. For this reason, manufacturers of subsea cables have extremely high demands on the cable production. The aim is to produce long cable lengths of high quality whenever possible in one piece to avoid joints under water, which are prone to disturbances. The demand on quality starts at the production process of optical fibres, which are built into a subsea cable for data communication. Every fault found during production of optical fibres which, therefore, does not reach the customer, contributes to the reliability of the product. For this reason, the continuous quality control of the optical fibre is ensured during production of the fibre in the drawing tower by the use of innovative measuring and control technologies at different production stages. During the fibre drawing process, Sikora measuring devices, in connection with display and control devices, are used in different positions to control the optical fibre parameters. Typically, a first gauge head, the Fiber Laser 6003, is installed below the draw sending

❍ The Fiber Laser 6003 measures the diameter of the optical fibre in the drawing tower

furnace to measure the diameter and position of the uncoated fibre. The gauge head calculates the tension from the vibration of the fibre with fast fourier transformation (FFT). The single values of the fibre position are graphically visualised by the processor system Fiber Ecocontrol in the form of a scatter plot and are available by Ethernet. The laser measuring process ensures a measuring accuracy of 0.05µm at a repeatability of 0.02µm. 2,500 measurements per second, with high single value precision and a short exposure time of 1.2µs, guarantee constant accuracy at the highest level. A second laser-gauge head measures the cold diameter of the optical fibre and the spinning after cooling and before coating. A control is performed either by the hot or cold gauge head. Additional devices also detect airlines in the optical fibre and give information about the temperature of the optical fibre.

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Wire & Cable ASIA – November/December 2014