  It is difficult for free space optical communication to be applied in mobile
communication due to the obstruction of obstacles in the environment, which is
expected to be solved by reconfigurable intelligent surface technology. The
reconfigurable intelligent surface is a new type of digital coding
meta-materials, which can reflect, compute and program electromagnetic and
optical waves in real time. We purpose a controllable multi-branch wireless
optical communication system based on the optical reconfigurable intelligent
surface technology. By setting up multiple optical reconfigurable intelligent
surface in the environment, multiple artificial channels are built to improve
system performance and to reduce the outage probability. Three factors
affecting channel coefficients are investigated in this paper, which are beam
jitter, jitter of the reconfigurable intelligent surface and the probability of
obstruction. Based on the model, we derive the closed-form probability density
function of channel coefficients, the asymptotic system's average bit error
rate and outage probability for systems with single and multiple branches. It
is revealed that the probability density function contains an impulse function,
which causes irreducible error rate and outage probability floors. Numerical
results indicate that compared with free-space optical communication systems
with single direct path, the performance of the multi-branch system is improved
and the outage probability is reduced.
