Atmospheric aberration mitigation and transmitter power scaling using a coherent fiber array

We describe our concept for a power scalable transmitter with built in high-speed (>1 kHz) atmospheric aberration correction capability also. We have demonstrated this concept in the laboratory using seven 1 W fiber amplifiers for the transmitter and phase locked them with a simple and robust method to give spatially coherent output at the receiver. We report the near and far field of the transmitter beam shapes and automatic small angle steering capability for the transmitter beam to follow the slight motions of the receiver. The airborne laser link platform presents difficult engineering problems. The system must be simple, light and rugged, yet provide sufficient power for high-bandwidth communications. The solution we propose naturally fits this application. Phased fiber arrays are a recognized simple solution to power scaling. The inclusion of the corrections of the fiber phase, atmospheric path aberrations, and steering in the same feedback loop is particularly elegant. The proposed transmitter requires substantially less power than an uncorrected transmitter to achieve same link margin, and uses COTS fiber components. Our transmitter can be scaled in power to 100 W and beyond and can correct even turbulence-induced aberrations because of its high-speed response capability.