Innovative Fiber Bragg Grating Sensors for Highly Demanding Applications: Considerations, Concepts, and Designs

Measurement of physical parameters using mechanical transducers is an important part of fiber optical sensing. Fiber Bragg grating (FBG)-based sensors with dedicated transducers can be designed to measure different physical parameters and can operate in extremely harsh environments. This makes the FBG sensor very suitable for special...

Fiber based hydrophones for ultra-high energy neutrino detection

It is a well studied process [1, 2] that energy deposition of cosmic ray particles in water that generate thermo-acoustic signals. Hydrophones of sufficient sensitivity could measure this signal and provide a means of detecting ultra-high energetic cosmic neutrinos. We investigate optical fiber-based hydrophone technology that could potentially...

Effect of towed array stability on instantaneous localization of marine mammals

Reliable localization of marine mammals using towed arrays is often required for mitigation, population density estimates, and bioacoustics research. The accuracy of the range estimates using towed arrays is often not well quantified. Triangulation methods using multiple hydrophones allow for fast range estimates but are sensitive to the species...

Passive diver detection and localization using hydrophones suspended under a boom

A boom is a line of floats that constitutes a physical barrier for providing abovewater stopping power. However, it does not provide any situation awareness. In order to overcome this shortcoming, an integrated “booms and sensors” solution using passive sonar was conceived and tested experimentally by suspending hydrophones under a boom. The...

Validation of finite element computations for the quantitative prediction of underwater noise from impact pile driving

The acoustic radiation from a pile being driven into the sediment by a sequence of hammer strikes is studied with a linear, axisymmetric, structural acoustic frequency domain finite element model. Each hammer strike results in an impulsive sound that is emitted from the pile and then propagated in the shallow water waveguide. Measurements from...

Adaptive Port-Starboard Beamforming of Triplet Sonar Arrays

Abstract—For a low-frequency active sonar (LFAS) with a triplet receiver array, it is not clear in advance which signal processing techniques optimize its performance. Here, several advanced beamformers are analyzed theoretically, and the results are compared to experimental data obtained in sea trials. Triplet arrays are single line arrays with...

Experimental comparison of bearing estimation techniques for short passive towed sonar arrays

Although Low Frequency Active Sonar (LFAS) is considered one of the best means of detection and localization of a submarine in shallow water, the use of an active system is not always possible for tactical reasons. It is therefore interesting to include a passive mode in these systems by using the receiving array as a passive array. However,...

A Two-Stage Method for Determining the Position and Corresponding Precision of Marine Mammal Sounds; 2004BU1-OT

Today there is a concern that man-made sounds, such as that from sonar experiments, seismic operations and oil rigs, affect marine mammals. Detection and localisation of marine mammals will definitely support measures to reduce the possible detrimental effects. This paper presents a two-stage localisation method, which is applied to data...

Shape and Doppler correction for a towed sonar array

Anti Submarine Warfare (ASW) is more and more focused toward shallow water environments. Many complications have come up for ASW sonar performance as a result of this. The problem that is tackled in this article is the performance loss due to the shape and motion of the sonar during a maneuver. Standard beamforming in towed sonar arrays is based...

Analysis of shallow-water experimental acoustic data including a comparison with a broad-band normal-mode-propagation model

Channel temporal variability, resulting from fluctuations in oceanographic parameters, is an important issue for reliable communications in shallow-water-long-range acoustic propagation. As part of an acoustic model validation exercise, audio-band acoustic data and oceanographic data were collected from shallow waters off the West Coast of...

Shallow-water acoustic communication with high bit rate BPSK signals

BPSK signals have been defined for transmission through a shallow-water acoustic communication channel. The signals were accompanied by two displaced carriers to facilitate carrier recovery. To correct for the adverse effects of time spreading, a pseudo-random learning sequence was transmitted ahead of the communication signal. The signal...

An environmental Assessment in the Strait of Sicily: Measurement and Analysis Techniques for Determining Bottom and Oceanographic Properties

In October 1997, the EnVerse 97 shallow-water acoustic experiments were jointly conducted by SACLANT Centre, TNO-FEL, and DERA off the coast of Sicily, Italy. The primary goal of the experiments was to determine the sea-bed properties through inversion of acoustic data. Using a towed source, the inversion method is tested at different source...