  We present a comprehensive study of the periodic variations observed in OGLE
I-band light curves of SMC Be/X-ray binaries, discovering new optical
periodicities in 9 systems. We find that these periodicities derive from a
number of mechanisms, notably disturbance of the decretion disk on the orbital
period of the system, and aliased non-radial pulsations. We develop metrics
that allow these mechanisms to be distinguished on the basis of the shape of
the folded optical light curve, and use these metrics to categorise the
periodicities present in \sim 50 SMC binary systems. We conclude that extreme
care must be taken in the interpretation of the OGLE light curves since only
around 30% of the periodicities present can be unambiguously attributed to
orbital periods.
