A description is given of the design, operation, and test over a 2-km path (roundtrip) of a continuous wave, coherent laser array receiver that uses two independent aperture–receivers whose intermediate frequencies are electro-optically co-phased in real time and then added as a proposed way to overcome effective aperture limitations imposed by atmospheric turbulence and to mitigate signal fading associated with atmospheric turbulence and speckle effects. The experiment resulted in a mean carrier-to-noise ratio increase of 1.8, which is within 1% of the theoretical predictions, when the two signals were phase locked, versus no increase without phase locking. Further, the carrier fading strength, or normalized carrier-to-noise ratio variance, was reduced by a factor of 0.53, which is within 2% of the theoretical prediction. The bandwidth of the electro-optic phase-locked loop was measured to be of the order of 600 Hz, which is adequate to compensate for atmospheric refractive turbulence fluctuations.
© 1996 Optical Society of America
Original Manuscript: July 14, 1995
Revised Manuscript: February 27, 1996
Published: October 20, 1996
Philip Gatt, Thomas P. Costello, Dean A. Heimmermann, Diana C. Castellanos, Arthur R. Weeks, and C. Martin Stickley, "Coherent optical array receivers for the mitigation of atmospheric turbulence and speckle effects," Appl. Opt. 35, 5999-6009 (1996)