WA-1150 and WA-1650 Wavemeter Operating Manual
4 Theory of Operation & Calibration
4-2
(09042-M-00 Rev C) EXFO Burleigh Products Group Inc.
WA-1150 is better than 0.5 parts per million. The absolute accuracy of the reference
laser wavelength used in the WA-1650 is better than 0.1 parts per million.
Wavelength accuracy also depends on the alignment of the reference laser beam and the
input laser beam in the Michelson interferometer. Fiber-optic input coupling and stable
optomechanical design ensure that the interferometer alignment does not change
significantly with time and environmental conditions.
At the time of manufacturing, the wavelength accuracy of each WA-1150/1650 is
verified with an accurately known laser source, such as a Distributed Feedback (DFB)
diode laser locked to the R(3) band of acetylene (
12
C
2
H
2
). The center of this absorption
line has been characterized to 196,832.341 GHz ± 150 KHz by K. Nakagawa et al. in
"Accurate optical frequency atlas of the 1.5m bands of acetylene," JOSA, B, 13, 2708
(1996) using an absorption line of rubidium as the reference standard.
Power Accuracy
The WA-1150/1650 internal power meter is designed with excellent linearity over the
full specified power range. Correction for the responsiveness of the power detector also
ensures that good power measurement flatness is achieved over the operating wavelength
range.
With the complete spectrum normalized to the total power measurement, the power in
each spectral peak is computed from the integrated intensity under that peak relative to
the average local baseline.
The internal power meter in every WA-1150/1650 is calibrated at the time of
manufacturing using a high-precision power meter that is regularly certified accurate
traceable to NIST.
Calibration
The recommended calibration interval is one year.
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