A method for transmitting signals in a subsea environment includes determining that a quality of an acoustic signal is below a threshold. The acoustic signal travels from a first device, through water in the subsea environment, to a second device. A parameter of the first device, the second device, or both is then adjusted to improve the quality of the acoustic signal when the quality of the acoustic signal is below the threshold.

A method for transmitting signals in a subsea environment includes determining that a quality of an acoustic signal is below a threshold. The acoustic signal travels from a first device, through water in the subsea environment, to a second device. A parameter of the first device, the second device, or both is then adjusted to improve the quality of the acoustic signal when the quality of the acoustic signal is below the threshold.

In order to readily carry out communication between terminal stations, a submarine optical communication system includes a first terminal station including a first monitoring means for monitoring the signal quality of dummy light a first dummy light source that outputs dummy light to the second terminal station, and a first light transmitting means for transmitting an optical signal to the second terminal station, the optical signal including a first signal quality of the dummy light; and the second terminal station including a second dummy light source that outputs dummy light to the first monitoring means, a second monitoring means for monitoring the signal quality of the dummy light, and a light receiving means for receiving the optical signal.

A low-computation underwater acoustic wake-up method based on a multi-carrier signal is provided. A multi-carrier signal corresponding to communication nodes is constructed, absolute values of the multi-carrier signal in a window at a receiver are summed for signal arrival detection, and then frequency points of the multi-carrier signal are detected many times by using the real fast Fourier transform to realize wake-up detection. The method is suitable for accurate wake-up at any distance within a maximum communication distance of two underwater acoustic nodes, has a small amount of calculation, and is suitable for low-power single-chip microcomputers. The modem can be in a low-power sleep state for a long time.

An underwater communications system may include a first device and a second device being movable relative to one another. The first device may include a first laser transmitter configured to generate a first laser beam having a selectable spatiotemporal beam shape from among a plurality thereof, and a first controller coupled to the first laser transmitter and configured to select a spatiotemporal beam shape for the first laser beam from among the spatiotemporal beam shapes. The second device may include a second laser receiver configured to receive the first laser beam, and a second controller coupled to the second laser receiver.

An underwater communications system may include a first device and a second device being movable relative to one another. The first device may include a first laser transmitter configured to generate a first laser beam having a selectable spatiotemporal beam shape from among a plurality thereof, and a first controller coupled to the first laser transmitter and configured to select a spatiotemporal beam shape for the first laser beam from among the spatiotemporal beam shapes. The second device may include a second laser receiver configured to receive the first laser beam, and a second controller coupled to the second laser receiver.

Aspects of the present disclosure include methods for communication using a MIMO channel, such as an acoustic channel for underwater communication. An acoustic receiver may receive a signal comprising information encoded in at least one transmitted symbol. Using a two-layer iterative process, the at least one transmitted symbol is estimated. The first layer of the two-layer process uses iterative exchanges of soft-decisions between an adaptive turbo equalizer and a MAP decoder. The second layer of the two-layer process uses a data-reuse procedure that adapts an equalizer vector of both a feedforward filter and a serial interference cancellation filter of the adaptive turbo equalizer using a posteriori soft decisions of the at least one transmitted symbol. After a plurality of iterations, a hard decision of the bits encoded on the at least one transmitted symbol is output from the MAP decoder.

Aspects of the present disclosure include methods for communication using a MIMO channel, such as an acoustic channel for underwater communication. An acoustic receiver may receive a signal comprising information encoded in at least one transmitted symbol. Using a two-layer iterative process, the at least one transmitted symbol is estimated. The first layer of the two-layer process uses iterative exchanges of soft-decisions between an adaptive turbo equalizer and a MAP decoder. The second layer of the two-layer process uses a data-reuse procedure that adapts an equalizer vector of both a feedforward filter and a serial interference cancellation filter of the adaptive turbo equalizer using a posteriori soft decisions of the at least one transmitted symbol. After a plurality of iterations, a hard decision of the bits encoded on the at least one transmitted symbol is output from the MAP decoder.

Disclosed is an optical window cleaning device, including: a cleaning brush; and a wiper arm. The wiper arm includes a first link, a torsion mechanism, a second link and a wiper arm drive system. A second end of the first link is hinged to a first end of the second link. The cleaning brush is hinged to a first end of the first link, a rotation trajectory of the cleaning brush and a rotation trajectory of a hinge joint between the second end of the first link and the first end of the second link are both located in a first plane. A rotation trajectory of the second link and the rotation trajectory of the hinge joint are located in the first plane. The torsion mechanism provides the first link and the second link with a force that rotates the first link relative to the second link.

A communication system (1) comprising a first and a second underwater wearable device to be worn by a swimmer at mutually distant locations is disclosed herein. The communication system is configured to derive information pertaining to the swimmer from properties of a version of the acoustic signal transmitted from a first communication module of the first underwater wearable device to a second communication module of the second underwater wearable device.