MOGlabs FZW600, Руководство пользователя

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4. Operation
4.1 Fringe identification and optimisation
The host software includes a prominent display of the interference
fringes used to compute the laser wavelength. Understanding the
fringe structure is important in ensuring that the wavelength mea-
surement is accurate. The two primary causes of reduced measure-
ment reliability are laser multi-moding, and poor spatial profile of
the light emitted by the fibre.
The presence of multiple frequency components during a measure-
ment can change the structure of the interference pattern and cause
the measurement to fail. Typically this is evident by the presence of
secondary peaks in the fringes, a significant widening of the peak
widths, and/or a significant reduction in the amplitude of the fringes
compared to the background level (Figure 4.1). Multimode behavi-
our may be evident in only one of the etalons (Figure 4.2) so it is
important to periodically verify the fringe shape.
Figure 4.1:
Examples of fringes measured with a single-mode laser (left)
and multimode laser (right). The presence of secondary peaks and re-
duction in contrast indicate the laser is not single-mode.
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