What’s Your Best Bet for Link Loss Measurement Uncertainties?
Optical time-domain reflectometers (OTDRs) are widely used to characterize elements on a fiber link, such as connectors and splices, because they can measure attenuation (signal loss), link loss reflectance and location for each element.
However, many operators question the degree of uncertainty of the link loss measurements obtained by an OTDR as opposed to that of a traditional light source power meter (LSPM). Which test equipment is more accurate? What best practices can be implemented to mitigate the degree of measurement uncertainty in each device?
Above all, it’s important to understand that there are a wide variety of theoretical and real-life loss-measurement uncertainties that are caused by LSPMs and OTDRs. Here is an overview:
| Theoretical Uncertainties | Real-life Uncertainties | |
| LSPM | Light source instability Light source wavelength Multimode launch conditions Mating reproducibility Reference connector repeatability |
Source drift after referencing Reference test jumper Presence of couplers in optical test sets (OLTS) |
| OTDR | Different loss uncertainty definitions Launch and receive test cord fiber geometry |
OTDR trace noise Weak backscattering signal after strong reflectance Quality of trace analysis and event detection robustness |
Among other specific guidelines, the team came up with five easy steps that can help you comparing both testing methods:
LS power reference
Loss measurement for LSPM
Test other devices under test (DUTs)
iOLM Insertion Loss (IL) measurement
Test other DUTs
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