Abstract
In a recent paper, we presented the influence of sinusoidal nonlinearities
in the wavelength sweeping speed on the performance of an absolute distance
interferometry setup. Nonlinearities in an optical frequency modulation
system are generally the source of degradation in performance. The interest
of this study comes from the experimental observation of the good behavior
of an absolute distance measurement system with the presence of sinusoidal
nonlinearities in the wavelength sweeping speed obtained from an external
cavity laser diode (ECLD). This paper presents experimental results obtained
with a custom ECLD based on a Littman–Metcalf setup. We link the
sinusoidal nonlinear sweep to some mechanical properties of the cavity. The
main source of these nonlinearities comes from the digitization of the
piezoelectric transducer excitation. Different types of excitation like
super-Gaussian and ramp, including or not sinusoidal modulations, were
implemented and analyzed. By this way, we are able to reduce the spectral
width by a factor 3 without adding linearization electronics such as a
servo-loop control on injection current or nonuniform samplers, and our
system achieves a $3 \times 10^{- 6}$ relative uncertainty on distance measurement with a number of
samples reduced by a factor 8.
© 2009 IEEE
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