  The analysis of beamstrahlung radiation, emitted from a beam of charged
particles due to the electromagnetic interaction with a second beam of charged
particles, provides a diagnostic tool that can be used to monitor beam-beam
collisions in a $e^{+}e^{-}$ storage ring. In this paper we show that the
beamstrahlung time profile is related to the timing of the collisions and the
length of the beams, and how its measurement can be used to monitor and
optimize collisions at the interaction point of the SuperKEKB collider. To
measure the time dependence of beamstrahlung, we describe a method based on
nonlinear frequency mixing in a nonlinear crystal of beamstrahlung radiation
with photons from a pulsed laser. We demonstrate that the method allows to
measure and optimize the relative timing and length of the colliding bunches
with 1% accuracy.
