The Wavemeter Jr. utilizes a scanning Michelson interferometer to determine the absolute wavelength of a test laser by referencing the number of interference fringes generated to the scan displacement measured by a calibrated Moiré scale. The result is absolute wavelength measurement to an accuracy of ± 100 ppm (± 0.1 nm at 1000 nm).

    When we opened the case, we removed the diode and circuit board that count the fringes from the interferometer.  A piece of paper was put in its place and the optics of the input (from the fibre optic cable that was transmitting our laser light to the Wavemeter Jr.) were adjusted until fringes were clearly visible on the paper.

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