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FAQs - Frequently Asked Questions

What kind of pulsed measurement is possible and what is the accuracy?

Spectral width:
The shorter a laser pulse is, the broader the spectral width of this laser. Laser pulses shorter than 100 ps can only be measured by the D option (Diffraction grating).

The accuracy of the wavelength meter is determined by the length of the longest interferometer inside the optical unit. The longer the interferometer, the smaller the spectral width of the laser has to be; if the laser is broader than the "free spectral range" of the interferometer, the interferences vanishes and no signal can be analyzed.
The type of lasers that can be used for each model can be found in the datasheet, page 4, Technical Data, line: Fizeau-interferometers: The maximum bandwidth is the upper limit for the spectral width of lasers that can be measured for each interferometer.
For each model (except WS-5) there's a so called "wide-line" mode available. In this measurement mode the longest interferometer will be ignored for the calculation. The WS-7 in wideline mode for instance is able to measure lasers with a maximum spectral width of 15 GHz. In normal mode, lasers with a spectral width < 4 GHz may be measured.
One more important point, we can only measure at a maximum of a factor of 3-5 better than the laser-width. So if the laser is 10 GHz broad, the best accuracy, you can expect is 2 GHz (Using an Ultimate by having only 10 GHz broad laser sources doesn’t make sense).