Application Note 4 Reliable Operation of LSProbe 1.2 Field Probes
2 Fiber Failure Mechanism
LUMILOOP’s statistics show that more than three quarters of the field probes that are
turned-in for analysis have fiber issues caused by improper handling.
For transparency, LUMILOOP creates a detailed report for every returned field probe, con-
taining failure analysis and corrective measures. Fig. 2 shows images taken out of a typical
repair report. In the shown case, the user had plugged the optical fibers frequently without
cleaning. Additionally, the sacrificial cables had been removed by mistake. Consequently,
both faces of an FC fiber connector pair, which carries the optical power for the field probe,
suffered a burn-in defect.
(a) Field Probe - FC before / after cleaning
(b) Field Probe - ST before / after cleaning
(c) Extension cable - FC before / after cleaning
(d) Extension cable - ST before / after cleaning
Figure 2: Example for contaminated FC (power) and ST (data) fiber connectors
As suggested by the name, burn-in defects are caused by excessive heating, leading to crack-
ing and/or melting of the fiber core where two fibers interface. A sound optical fiber inter-
face introduces less than 0.5 dB of attenuation. Contamination, e.g. by dust particles, will
result in a higher attenuation, and thus a significant fraction of the optical power to be
converted into heat.
= x 1000
Figure 3: Power density comparison: 1 Watt fiber core vs. 1 Kilowatt hot plate
November 23, 2020
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