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.