Center Wavelength Using A Threshold Relative To The Peak; Power At The Center Wavelength; Bandwidth - JDS Uniphase SWS15100 User Manual

7. Get the power at each of these points.
8. Interpolate to find the power at the center wavelength from these points.

Center Wavelength using a Threshold Relative to the Peak

The SWS calculates center wavelength using the following procedure:
1. Find the specified peak signal level. Store the wavelength at which the level occurs.
2. At a power level x dB from the peak found in Step 1, find the shorter wavelength (λ
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 ) corresponding to x dB is interpolated from these two data points. The search
L
is begun, starting outward (left) from the peak position.
3. At the same level (x dB from the peak), find the longer wavelength (λ
as in Step 2. The search is begun, moving outward (right) from the peak position.
4. Compute the center wavelength (CW) as the mean of the two, (λ
5. Find the two data points of the signal nearest the CW.
6. Get the power at each of these points.
7. Interpolate to find the power at the center wavelength from these points.

Power at the Center Wavelength

The power at the data sample nearest the center wavelength is reported as the power at the
center wavelength.

Bandwidth

Finding Bandwidth using a Threshold Relative to the Baseline
The algorithm used by the SWS to find the bandwidth is:
1. Find the specified peak signal level. Store the wavelength at which this occurs.
2. Find the average baseline of the signal, relative to which other levels are defined.
3. At a power level x dB from the baseline found in Step 2, find the shorter wavelength ( λ
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 ) corresponding to x dB is interpolated from these two data points. The
L
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
signal, as in Step 3. The search is begun, moving outward (right) from the peak position.
222 – Reference
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