Range Gating of Photons Multiply Scattered in a Stratified Ocean

Abstract

The applicability of digital correlators to LIDAR is investigated for the special case of a subsurface lidar probing optical depth of the water column in the ocean. The correlator is assumed to operate in the signal averaging mode. For generality a bi-static configuration is analyzed which has advantages under lowest light level conditions. Multiple scattering in the ocean is simulated by a Monte Carlo method. Analysis is included to derive the number density of photons arriving at the detector and the expected arrival time distribution in relation to the lidar pulse energy. Optical depth is obtained by logarithmic display of the correlator channel contents. It is concluded that actual experiments should be possible with existing fast digital correlators and pulsed dye lasers of 1 mJ pulse energy or less.