High-accuracy angle detection for ultra-wide-field-of-view acquisition in wireless optical links

Abstract

A novel scheme to deploy a point-to-multipoint optical wire- less communication network is proposed. The master node provides hemispherical field-of-view FOV acquisition via a fisheye lens to achieve the automatic establishment of optical links with user nodes. We present an effective distortion-correcting algorithm based on two-ary piecewise bicubic spline interpolation to correct the large optical distor- tions of the fisheye lens. Using this algorithm, the angles of the incident beams are accurately calculated according to the laser spot position on the CCD charge-coupled device sensor with the maximum error of 0.027 deg. In addition, the strong background radiation from such an ultrawide FOV also leads to significant degradation of the angle detec- tion accuracy under the condition of weak received optical power. A Voigt anomalous dispersion optical filter with ultra-narrow-pass bandwidth is adopted to resist the background radiation. The numerical simulation results show that the total angle detection error caused by the optical distortion and the background radiation is within 0.06 deg. Considering the extra gimbal pointing error and the angle-of-arrival fluctuations due to atmospheric turbulence, the pointing error of the master node is less than 0.079 deg, which meets the high-accuracy requirement of pointing for the automatic optical link establishment. © 2008 Society of Photo-Optical