FS22DI
MEASURING EXAMPLES
30
4.3.2
Broken Connector
It may also occur that the interrogator adapter sleeve breaks. In this case, when an opti
cal connector is inserted, it will not get proper alignment and measurements will be com
promised. A broken sleeve will look as shown in
.
Fig. 4.9
Broken connectors
To solve this problem you should contact HBK FiberSensing.
4.3.3
Reflective Fiber Ending
Even when all connections have been performed correctly, it may occur that the interroga
tor does not find any sensor on an array. One of the reasons may be the excess of
reflected light saturating the detectors.
When a fiber is perfectly cut (Fig. 4.10 on the left) a large amount of light is reflected right
back into the core of the fiber in such an angle that it gets guided back heading to the
interrogator detectors. When this occurs, an index matching gel or an angled termination
must be used. If these are unavailable, the tip of the fiber can be smashed with a metallic
tool. This will destroy the perfect geometry (
on the right) and the light that is
reflected at the surface will take random directions ending up outside the core.
Reflective Fiber Ending
Refractive Fiber Ending
Fig. 4.10
Refraction and reflection at fiber end
4.3.4
Cut Fiber
When the fiber, for any reason, is broken between two sensors in series, the sensors that
are after the fault may disappear from the optical spectrum and may not be detected.
