EoW January 2014

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Technical article
January 2014 77
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.
2 New coating
material
2.1 Material properties
The newly developed mid-temperature
coating is a UV curable urethane acrylate.
A 75-micron thick film cured at 1 J/cm2
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.
▲ ▲ Figure 3: Weight loss of new coating on single coat fibre at 150°C, 180°C and 200°C
▲
▲ Figure 4: Comparison of weight loss of fibre with new and commercial coating at isothermal aging at 180°C
Weight loss, % New (°C) Commercial (°C)
5 329 310
10 366 334
20 402 358
▲ ▲ 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
Coating weight loss, %
Exposure time, hours
Coating weight loss, %
Delta attn at 1550mm,dB/km
200 micron newmaterial fibre strength at 150°C and 180°C
Exposure time, hours
Single coat newmaterial (200 micron) fibre coating
weight loss at 150°C, 180°C and 200°C
New
Commercial
Exposure time, hours