In situ monitoring of ocean chlorophyll via laser-induced fluorescence backscattering through an optical fiber.

The first seagoing test of a prototype laser/fiber-optic system for in situ detection of ocean chlorophyll fluorescence is described. Radiation at 488 nm originating from a shipboard argon laser was transmitted through 20 of 200-microm core optical fiber to the distal tip mounted on the microstructure profiler, the Rapid Sampling Vertical Profiler. The backscattered fluorescence emission signal was collected through the same fiber and processed on board ship. A series of measurements indicated that (1) successful isolation of shipinduced vibrations could be achieved using our optical bench framework to maintain optical alignments; (2) ambient chlorophyll concentrations could be detected in situ; (3) a Raman scattering signal from water could also be detected and should provide an internal standard against which chlorophyll fluorescence may be calibrated.