Hi

I'm using the 86142B to measure the percentage of power from a laser within a between 930-950 nm. I use the wavelength markers to get that power between 930 and 950 then divide that by the total integrated power. We also save the total spectrum to csv. The percent of in-band power from the two OSA values is different than what we get when we sum up the spectrum points in excel. Any ideas as to what I could be missing?

I'm using the 86142B to measure the percentage of power from a laser within a between 930-950 nm. I use the wavelength markers to get that power between 930 and 950 then divide that by the total integrated power. We also save the total spectrum to csv. The percent of in-band power from the two OSA values is different than what we get when we sum up the spectrum points in excel. Any ideas as to what I could be missing?

A possible source of the difference could be that the integrated power function is normalizing the power at each trace point by the ratio of the trace point spacing to the effective resolution bandwidth.

Since you are looking at the ratio between two such calculations, that normalization might be canceling out in your result. But if spectra are compared that used different spacing or resolution bandwidth, that would also have an effect.

The spacing is determined by the scan range and the number of trace points, which is 1001 by default. So a different scan range will change the trace point spacing.

Since you're looking at a laser with such a wide spectrum, I guess this may be a Fabry Perot laser with multiple lines.

I think that in this case you want to be sure that the trace point spacing is smaller than the resolution bandwidth, so that the individual lines are not interpreted as a power density extending over a wider interval.

The internal application for Source Measurement of FP lasers might also be useful for you.

Mike