A compact, integrated acoustic localization and communications array includes an air-backed transmit element having a first end on which an end cap is disposed, and a second end configured to be mounted to a mounting surface. A volumetric acoustic array including a plurality of receiver elements that is electrically integrated to the transmit element. The localization and communications array is configured to transmit, via the transmit element, and receive, via the plurality of the receiver elements, an acoustic signal having a frequency in the range of 10 kHz to 50 kHz. Each of the plurality of receiver elements are spaced apart from the end cap at least a distance. The distance is greater than ¼ of a wavelength associated with the frequency transmitted and received by the localization and communications array, and is not equal to an odd multiple of ¼ of the wavelength.

A sensing and transmitting system and method of using same, including a plurality of acoustically transmitting sensor (ATS) devices having a sensor, a housing, and a transmitter that, together, converts a physical quantity of the fluid body into a responsive signal measurable over long distances underwater by a central receiving node. The node having a receiver or receiver array, a controller and typically a logger. The signals sent by the ATS are modulated according to the sensor's measured parameter and in a manner known to and decodable by the node. This system may further have an autonomous node and the modulated signals of the plurality of ATS may influence the behaviour of the node.

A free node to be deployed underwater for omnidirectional energy and data harvesting includes a housing that forms a sealed chamber; a wavelength-changing layer attached to an outside of the housing and configured to receive a first optical signal having a first wavelength range and to emit a second optical signal having a second wavelength range, different from the first wavelength range, wherein the first optical signal includes encoded data; a flexible solar cell wrapped around the housing, the flexible solar cell being configured to receive the second optical signal and generate an electrical signal; an energy storage module located in the chamber and configured to store electrical energy associated with the electrical signal; and a decoder located in the chamber and configured to receive the electrical signal and decode the encoded data. The first wavelength range is ultraviolet light and the second wavelength range is visible or infrared light.

A free node to be deployed underwater for omnidirectional energy and data harvesting includes a housing that forms a sealed chamber; a wavelength-changing layer attached to an outside of the housing and configured to receive a first optical signal having a first wavelength range and to emit a second optical signal having a second wavelength range, different from the first wavelength range, wherein the first optical signal includes encoded data; a flexible solar cell wrapped around the housing, the flexible solar cell being configured to receive the second optical signal and generate an electrical signal; an energy storage module located in the chamber and configured to store electrical energy associated with the electrical signal; and a decoder located in the chamber and configured to receive the electrical signal and decode the encoded data. The first wavelength range is ultraviolet light and the second wavelength range is visible or infrared light.

A submersible inspection drone used for inspection of liquid cooled electrical transformers can include a number of separate cameras for imaging the internal structure of the transformer. The submersible can be configured to communicate to a base station using a wireless transmitter and receiver. The cameras on the submersible can be fixed in place and can be either static or motion picture cameras. The submersible can include an input/output selector capable of switching between the camera images, either through commanded action of a user or through computer based switching. In one form the input/output selector is a multiplexer. The base station can be configured to display images from the cameras one at a time, or can include a number of separate viewing portals in which real time images are displayed. The base station can include a demultiplexer synchronized to the multiplexer of the submersible.

A submersible inspection drone used for inspection of liquid cooled electrical transformers can include a number of separate cameras for imaging the internal structure of the transformer. The submersible can be configured to communicate to a base station using a wireless transmitter and receiver. The cameras on the submersible can be fixed in place and can be either static or motion picture cameras. The submersible can include an input/output selector capable of switching between the camera images, either through commanded action of a user or through computer based switching. In one form the input/output selector is a multiplexer. The base station can be configured to display images from the cameras one at a time, or can include a number of separate viewing portals in which real time images are displayed. The base station can include a demultiplexer synchronized to the multiplexer of the submersible.

The present disclosure provides a method for optimizing a protograph-based LDPC code over an underwater acoustic (UAW) channel. The traditional protograph-based LDPC code over an UAW channel does not consider performance in an error floor region. The method first determines parameters such as a protograph-based LDPC code length, a basic protograph, a target decoding threshold, a threshold adjustment factor, and an ACE check parameter. The protograph is optimized, and the method constructs a parity check matrix by using a UAW channel-based PEG/ACE hybrid algorithm, performs ACE check on the parity check matrix, and calculates a decoding threshold for the matrix passing the check. If the decoding threshold is within a range of an iterative decoding threshold, the parity check matrix is a final optimized matrix. Otherwise, the method continues to optimize the protograph until a parity check matrix passing the check is obtained.

The present disclosure provides a method for optimizing a protograph-based LDPC code over an underwater acoustic (UAW) channel. The traditional protograph-based LDPC code over an UAW channel does not consider performance in an error floor region. The method first determines parameters such as a protograph-based LDPC code length, a basic protograph, a target decoding threshold, a threshold adjustment factor, and an ACE check parameter. The protograph is optimized, and the method constructs a parity check matrix by using a UAW channel-based PEG/ACE hybrid algorithm, performs ACE check on the parity check matrix, and calculates a decoding threshold for the matrix passing the check. If the decoding threshold is within a range of an iterative decoding threshold, the parity check matrix is a final optimized matrix. Otherwise, the method continues to optimize the protograph until a parity check matrix passing the check is obtained.

An underwater optical communication system (100) is provided with a first optical communication device (1) that includes a first filter (12), a second optical communication device (2) that includes a second filter (22) and performs bi-directional optical communication with the first optical communication device. The first filter is configured to selectively transmit light of a predetermined wavelength band including a second wavelength (41) but not including a first wavelength (40). The second filter is configured to selectively transmit light of a predetermined wavelength band including the first wavelength but not including the second wavelength.

An underwater optical communication system (100) is provided with a first optical communication device (1) that includes a first filter (12), a second optical communication device (2) that includes a second filter (22) and performs bi-directional optical communication with the first optical communication device. The first filter is configured to selectively transmit light of a predetermined wavelength band including a second wavelength (41) but not including a first wavelength (40). The second filter is configured to selectively transmit light of a predetermined wavelength band including the first wavelength but not including the second wavelength.