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Definition of Terms 7
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Definition of Terms
Wavelength Range refers to the allowable wavelength range of the
optical input signal.
Absolute accuracy indicates the maximum wavelength
error over the allowed environmental conditions. The
wavelength accuracy is based on fundamental physical
constants, which are absolute standards not requiring
traceability to artifacts kept at national standards labo-
ratories. Two He-Ne gas lasers are used. First, there is
an internal 632.991 nm-vacuum (473.6127 THz) refer-
ence laser
a
. To verify absolute wavelength accuracy, an
external laser is measured during manufacturing at
1523.488 nm, or 196.7804 THz
b
.
Differential Accuracy indicates the maximum wave-
length error in measuring the wavelength difference
between two signals that are simultaneously present.
Minimum Resolvable Separation indicates the mini-
mum wavelength separation of two laser lines required
to measure each wavelength simultaneously. Two laser
lines closer in wavelength than the minimum resolvable
separation are not resolved and one average wavelength
is displayed.
Display Resolution indicates the minimum incremen-
tal change in displayed wavelength.
Amplitude
Calibration Accuracy
indicates the maximum power
calibration error at the specified wavelengths over the
allowed environmental conditions. The amplitude cali-
bration accuracy is traceable to a National Institute of
Standards and Technology (NIST) calibrated optical
power meter. NIST is the national standards laboratory
of the United States.
a. Obarski, G. E. 1990. “Wavelength Measurement System for Opti-
cal Fiber Communications” NIST Technical Note 1336 (Febru-
ary): 18. Take the average of the two frequencies straddling gain
center.
b. D. A. Jennings, F. R. Peterson, and K. M. Evenson. 1979. “Fre-
quency measurement of the 260-THz (1.15 micron) He-Ne laser”
Optics Letters Vol. 4, No. 5 (May): 129-130.