JDS Uniphase SWS15100, Руководство пользователя

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Reference – 221
How the SWS Calculates Values
A value of n indicates an integer; a value of x indicates a real number.
Threshold Power
Threshold power is set by the user. All calculations are performed at x dB, or the equivalent
fraction, below the baseline or the peak, or x dB, or the equivalent fraction, above the baseline or
the peak, as specified by the user. The baseline is computed by repeatedly averaging the signal.
Wavelength at the Minimum
The wavelength at the minimum in the signal is found by searching for the absolute minimum
signal, if the signal has a minimum. The user specifies whether the signal has a minimum or a
maximum.
Minimum Power
The minimum power value is the value of the absolute minimum signal levels, regardless of the
noise.
Wavelength at the Maximum
The wavelength at the maximum in the signal is found by searching for the absolute maximum
signal, if the signal has a maximum. The user specifies whether the signal has a minimum or a
maximum.
Maximum Power
The maximum power value is the value of the absolute maximum signal levels, regardless of the
noise.
Center Wavelength using a Threshold Relative to the Baseline
The SWS calculates center wavelength using the following procedure:
1. Find the specified peak (minimum or maximum) signal level. Store the wavelength at which
the level occurs.
2. Find the average baseline of the signal. Other levels are defined relative to average baseline.
3. At a power level x dB from the average baseline (Step 2), find the shorter wavelength (
λ
L
)
nearest to the signal. The wavelength is determined by finding two data points, one to the left
of the wavelength at which the signal crosses x dB, and one to the right of that wavelength.
The wavelength (
λ
L
) corresponding to x dB is interpolated from these two data points. The
search is begun, starting outward (left) from the peak position.
4. At the same level (x dB from the baseline), find the longer wavelength (
λ
R
) nearest to the
signal, as in Step 3. The search is begun, moving outward (right) from the peak position.
5. Compute the center wavelength (CW) as the mean of the two, (
λ
R
+
λ
L
)/2.
6. Find the two data points of the signal nearest the CW.
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