  Integrated sensing and communication (ISAC) is viewed as a crucial component
of future mobile networks and has gained much interest in both academia and
industry. Similar to the emergence of radio-frequency (RF) ISAC, the
integration of free space optical communication and optical sensing yields
optical ISAC (O-ISAC), which is regarded as a powerful complement to its RF
counterpart. In this article, we first introduce the generalized system
structure of O-ISAC, and then elaborate on three advantages of O-ISAC, i.e.,
increasing communication rate, enhancing sensing precision, and reducing
interference. Next, waveform design and resource allocation of O-ISAC are
discussed based on pulsed waveform, constant-modulus waveform, and
multi-carrier waveform. Furthermore, we put forward future trends and
challenges of O-ISAC, which are expected to provide some valuable directions
for future research.
