ILX Lightwave FPM-8200, User Manual

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FR O N T PA N E L O P E R A T I O N
Operating Guidelines
01_10 FPM-8200
19
C H A P T E R
2
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Understanding the Calibration Certificate
Your FPM-8200 is supplied with a certificate for NIST traceable calibration from
ILX Lightwave's NVLAP
Æ
certified NIST traceable laboratory. This certificate
contains very useful information. The following discussion explains the meaning of
the information on your calibration certificate.
Photodetector Responsivity
The FPM-8200 Fiber Optic Meter is a stable low noise current meter with a
photodetector. Factory calibration is a process of recording detector current while
varying wavelength. The result is a table of detector responses every 10
nanometers, in mA per mW. When you connect input light, the FPM-8200
measures detector current, then uses the wavelength setting to look up the
conversion factor on the calibration table. Interpolation algorithms are used for
wavelengths between these calibration points. Note also:
• The highest detector current (greatest sensitivity) is at the longer wavelengths normally used
for telecom work.
• Changes in detector response are significant enough that the meter must know the
wavelength in order to properly display optical power.
• Detector response is less at shorter wavelengths.