  This paper explores a new paradigm of optical integrated sensing and
communication (O-ISAC). Our investigation reveals that optical communication
and optical sensing are two inherently complementary technologies. On the one
hand, optical communication provides the necessary illumination for optical
sensing. On the other hand, optical sensing provides environmental information
for optical communication. These insights form the foundation of a
directionless integrated system, which constitutes the first phase of O-ISAC.
We further put forth the concept of optical beamforming using the collimating
lens, whereby the light emitted by optical sources is concentrated onto the
target device. This greatly improves communication rate and sensing accuracy,
thanks to remarkably increased light intensity. Simulation results confirm the
significant performance gains of our O-ISAC system over a separated sensing and
communication system. With the collimating lens, the light intensity arrived at
the target object is increased from 1.09% to 78.06%. The sensing accuracy and
communication BER are improved by 62.06dB and 65.52dB, respectively.
