Kingfisher KI23400 Series, Руководство по эксплуатации и техническому обслуживанию

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ACCURACY CONSIDERATIONS
KI23400/KI27400 UM-2 -
61 -
Accuracy Considerations
Keep optical connectors clean and in good condition. Always clean
and inspect connector tips before mating.
Use test-quality leads with a similar fiber type to the system under test.
This is particularly important for multimode systems. If all else is well,
test lead repeatability is often the limiting factor in test accuracy.
When testing to an acceptance standard, it is important to adhere
carefully to requirements, test methods, patch lead verification and
referencing methods (1 ,2, 3 lead etc) specified in the standard.
To reduce the effect of polarisation changes, the fiber system should
be neat, coiled and physically stable.
In multimode systems, modal noise and general uncertainty are often
worse than in single mode systems. Optimum measurement
repeatability is obtained by using of a mandrel wrap close to a source.
Please visit www.kingfisherfiber.com to see our comprehensive
Application Notes written to support instrument users.
Power Meter
Using an APC connector at the power meter interface reduces line
reflections and so improves measurement stability, particularly in
laser-based systems. This is important when measuring small
connector losses.
Responsivity of InGaAs detectors may be very λ sensitive at 850 nm,
resulting in poor absolute accuracy and excessive sensitivity to source
λ drift during warm up. At this λ , Si or Ge detectors are preferable.
Refer to responsivity graph.
Responsivity of Ge detectors may be very λ sensitive at 1550 nm and
above, resulting in poor absolute accuracy and excessive sensitivity
to source
λ drift during warm up. At these λ , InGaAs detectors are
preferable. Refer to responsivity graph.
For best absolute power testing accuracy, the meter calibration λ
should be set close to the measured λ . Note that λ uncertainty of test
sources may be 30 nm, in which case it is not possible to set the meter
λ with great accuracy.
For high precision use, power meters provide better accuracy when
measuring a non-coherent source such as an LED. So, for best
accuracy when testing small losses on single mode patch leads etc,
an LED source may be preferred.
High power (attenuated) meters tend to suffer overall reduced
accuracy. Kingfisher high power meters use a multi-technology
attenuating element to reduce the adverse effects of reflections and λ
sensitivity.
At levels below about -45 dBm, spurious readings can be caused by
stray light leaking into fiber and patch cables. This can be a problem
with extended range linearity measurements.
Ge power meters have limited linearity, sensitivity and accuracy
compared to all other types.