Power-scalable phase-compensating fiber-array transceiver for laser communications through the atmosphere

Abstract

We report laboratory experiments demonstrating a phase-compensating 70-mm-diameter aperture transceiver that comprises a hexagonally close-packed array of seven 23-mm-diameter fiber collimator subapertures. Other than the collimators, the transceiver uses only fiber optics, connected as a master oscillator-multiple amplifier. The master oscillator is a fiber-coupled 1.5-µm diode laser, which is split and fed to 1-W fiber amplifiers before it exits the collimators. To obtain a phase-coherent far field we control each subaperture's phase by adjusting the current to its amplifier's pump diodes in a multidither arrangement, maximizing the signal at the receiver. We achieve a diffraction-limited coherent beam combination in the far field that produces 1.4 W of power in the main lobe, in agreement with theory.