Introduction

This chapter provides a general high-level overview of the status of near-earth laser communications technology developments and future research opportunities. Lasercom allows the data to be sent at multiple gigabits/second (Gb/s) in a burst mode for a short contact time. A challenge is that both lasercom host platforms are moving and have dynamic characteristics. Fluctuations of laser intensity at the receiver are partially caused by atmospheric refractive index fluctuations. Wavelength diversity relies on laser beams of unequal wavelengths experiencing different disturbances as they pass through air masses with varying indices of refraction. A lasercom instrument is comprised of telescope(s), lasers, imager(s), detectors, and beam directors. Highly efficient flight laser transmitters capable of multi-Gb/s bandwidth modulation at moderate average power levels and with high spatial beam quality are required for near-earth laser telecommunications in the direct-detection mode. The chapter also presents an overview of the key concepts discussed in this book.