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IR Imaging Bundles Made fr om Chalcogenide Glass Fibers 193

fiber, unclad. However, even though the measured tensile strength
for C2 is 122,000 psi, when multiplied by the core area in inches, the
force to break becomes only a few ounces. This fact is illustrated in
Fig. 8.9 which shows force to break as a function of core diameter for
C1, C2, and silicate fiber. The same treatment is applied to silica fibers
which are about 6 times stronger. Even silica fiber at a core diameter
of 100 µm (0.004 in) breaks at less than 10 lb. The calculated force to
break for different diameters of C2 fiber is as follows:

200-µm core = 6.1 lb
150-µm core = 3.4 lb
100-µm core = 1.5 lb
75-µm core = 0.86 lb (28 oz)
50-µm core = 0.38 lb (12 oz)

Breakage during ribbon drawing would be a serious problem,
one we could not tolerate especially while drawing 10-m ribbons.
Unclad 50-µm core fiber could be drawn on the 10-m drum but not
without risking severe fiber breakage. Each time breakage occurred,
the partial ribbon would have to be removed and a new ribbon layer
started. An analysis by Gary Wiese of Panoptics showed that MTF
performance by the bundle in the infrared was insensitive to fiber

Breaking force for glass fiber as a function of core diameter
60
C1 Fiber
C2 Fiber
50
Silicate
Breaking force (lb) 30
40

20

10

0
0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01
Core diameter (in)
FIGURE 8.9 Breaking force in tension for C1, C2, and silicate fi ber as a function of
fi ber core diameter.