Measurements of transmissions fluctuations for three long ranges in the deep ocean

Abstract

Pulse-like signals were transmitted continuously between a moored source and a fixed bottom-mounted receiver located 700 m below the deep sound channel axis. The source was deployed at three ranges: 210, 412, and 563 km. A second mooring measured temperature fluctuations caused by internal waves and source mooring motion was also measured. The duration of the transmitted pulse was approximately 9 ms (4 cycles of 459-Hz carrier). Several distinct RR arrivals have travel time consistent with ray theory predictions. Statistics of fluctuations for the individual paths and the combined multipath are computed and compared with predictions of the theory of scattering from internal waves. Those fluctuations associated with travel time (Phase pulse-to-pulse coherence, etc.) are consistent with a priori model predictions. Statistics of intensity fluctuations for all paths are typical of saturated multipath interference, a result difficult to reconcile with model prediction even when ambiguities in the computation of the defraction parameter are taken into account.