Laser Communications Fine Tracker

Project Goal: Remove the error from an emulated satellite laser communication so that 90% or more of the maximum power of the signal is received.

Satellites communicate through ultra high and super high radio frequencies, which are between 10 and 100 times slower than laser communications. However, calibration systems for laser communications are slow and time consuming, so they cannot accurately track low earth orbiting satellites. A faster system that can better catch the beam would make significantly more data available from each stream.

This design has two sub-systems, mounted to a standard optical table. An error emulator, which replicates the real-error in a satellite communication signal, uses a piezoelectric mirror to induce jitter in an F/6.8 1550nm continuous-wave laser signal replicating a 0.5m telescope. The second subsystem, a laser tracker, which stabilizes the beam and removes error from the signal, focuses it onto an optical fiber that feeds to a power detector.

A fast-steering mirror in a closed-loop configuration with a position sensing detector maintains the beam's position on the optical fiber. With this system, 90% of the maximum incident beam power on the optical fiber is autonomously maintained.