EoW January 2014

Technical article

primary experimental method to track coating stability and to test optical fibre parameters: attenuation and mechanical strength. Dynamic thermo gravimetric analysis (TGA) and isothermal TGA are used to compare different coating materials, estimate coating material lifetime based on coating weight loss, and to define the best coating system for a specific application. Corning Incorporated has evaluated a new optical fibre coating material for mid-temperature applications. The coating is a UV-cured acrylate type material. This material should preserve long-term optical fibre performance for bare and cabled fibre. The new coating delivers a high coating adhesion to glass, which is highly desirable in some mid-temperature optical fibre applications for better handle ability and optical performance. The newly developed mid-temperature coating is a UV curable urethane acrylate. A 75-micron thick film cured at 1 J/cm 2 with Fusion D-bulb was measured by a Seiko Simultaneous TG/DTA220 in air at a heating rate of 10°C/min. Figure 1 compares the weight loss vs temperature of the new material to a commercially available coating. The TGA of the two coatings diverge at 290°C with the new coating showing a smaller weight loss and, therefore, a higher thermal stability. The temperature at selected weight loss is listed in Table 1 . 2.2 Optical fibre samples Single-mode fibre samples were drawn with a glass cladding outer diameter (OD) of 125 μm and new material single coat OD of 200 μm. Draw conditions (draw speed and UV lamp settings) were selected to deliver a standard degree of cure of the coating materials. This coating design allows direct com- parison with commercially available Corning mid-temperature fibres with a single coat design and coating OD of 200 μm. 2.3 TGA tests A dynamic TGA test was conducted in air, and the fibre specimen weight change was measured at different heating rates in a temperature range between room temperature and 600-700°C. 2 New coating material 2.1 Material properties

Single coat newmaterial (200 micron) fibre coating weight loss at 150°C, 180°C and 200°C

Coating weight loss, %

Exposure time, hours

▲ ▲ Figure 3 : Weight loss of new coating on single coat fibre at 150°C, 180°C and 200°C

New Commercial

Coating weight loss, % Delta attn at 1550mm,dB/km

Exposure time, hours

▲ ▲ Figure 4 : Comparison of weight loss of fibre with new and commercial coating at isothermal aging at 180°C

200 micron newmaterial fibre strength at 150°C and 180°C

Exposure time, hours

▲ ▲ Figure 5 : Attenuation test for newmaterial single coat optical fibre samples at 150°C, 180°C and 200°C

▼ ▼ Table 1 : The temperatures at weight loss of 5, 10 and 20% between new and commercial coating

Weight loss, %

New (°C)

Commercial (°C)

5

329 366 402

310 334 358

10 20

77

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January 2014