Abstract: The present invention relates to a system for distributed acoustic sensing in a marine environment surrounding a repeater along a fibre-optic submarine communications cable. The system includes at least one distributed acoustic sensing (DAS) unit. Each DAS unit further includes a light source that is configured to transmit outgoing light in at least one fibre-optic sensing cable that is located in the marine environment and a receiver configured to receive reflected light that includes at least one optical property influenced by an acoustic disturbance in the marine environment. Each DAS unit further includes an optical multiplexer for multiplexing optical signals onto the fibre-optic submarine communications cable via the repeater where the optical signals carry information on the at least influenced optical property. A method for distributed acoustic sensing in the marine environment is also disclosed.

Abstract: Described herein is a fibre optic sensing method and system for generating a dynamic digital representation of a plurality of objects and associated zones in a geographic area. In general, the disclosed method and system comprises (a) generating a zone feature dataset, including identifying and classifying the associated zones in the area, each zone being classified into a zone type based on static and/or quasi-static zone features and having at least two object-sensed conditions; (b) generating an object tracking dataset, including tracking signals of at least some of the plurality of objects in the geographic area using a distributed fibre optic sensing network, and processing the tracking signals to obtain object-specific tracking data; (c) generating an event dataset, including using the tracking data to determine when the conditions of the zones are changing; digitizing and storing the changed conditions of the zones; and (d) rendering a dynamic representation of the conditions of the zones.

Abstract: An acoustic system and method is disclosed for providing spatial and temporal classification of a range of different types of sound producing targets in a geographical area. The system includes an optical signal transmitter arrangement for repeatedly transmitting, at multiple instants, interrogating optical signals into each of one or more optical fibres distributed across the geographical area and forming at least part of an installed fibre-optic communications network. An optical signal detector arrangement receives, during an observation period following each of the multiple instants, returning optical signals scattered in a distributed manner over distance along the one or more of optical fibres.

Abstract: Described herein is a method and system for distributed fibre optic sensing in particular across multiple fibre optic ports with multiple corresponding fibre optic paths.

Abstract: The present invention relates to a system for distributed acoustic sensing in a marine environment surrounding a repeater along a fibre-optic submarine communications cable. The system comprises at least one distributed acoustic sensing (DAS) unit. Each DAS unit further comprises a light source that is configured to transmit outgoing light in at least one fibre-optic sensing cable that is located in the marine environment and a receiver configured to receive reflected light that includes at least one optical property influenced by an acoustic disturbance in the marine environment. Each DAS unit further comprises an optical multiplexer for multiplexing optical signals onto the fibre-optic submarine communications cable via the repeater where the optical signals carry information on the at least influenced optical property. A method for distributed acoustic sensing in the marine environment is also disclosed.

Abstract: An acoustic system and method is disclosed for providing spatial and temporal classification of a range of different types of sound producing targets in a geographical area. The system includes an optical signal transmitter arrangement for repeatedly transmitting, at multiple instants, interrogating optical signals into each of one or more optical fibres distributed across the geographical area and forming at least part of an installed fibre-optic communications network. An optical signal detector arrangement receives, during an observation period following each of the multiple instants, returning optical signals scattered in a distributed manner over distance along the one or more of optical fibres.

Abstract: Described herein is a method and system of distributed acoustic sensing, such as in an urban or metropolitan area involving a dedicated and established fibre optic communications network including a data centre. In general, the disclosed method and system includes the steps of (a) selecting an optical fibre cable installation having a path extending across a selected geographical area, the optical fibre cable installation including a bundle of optical fibres and forming part of a fibre-optic communications network, (b) determining characteristics associated with the optical fibre and/or the selected optical fibre installation, (c) transmitting outgoing light in the optical fibre, (d) receiving reflected light back scattered along the optical fibre, and (e) based on the reflected light and the determined characteristics, generating an alert signal representative of an acoustic event. The disclosed method and system is thereby configured to detect acoustic events near or within the selected geographical area.

Abstract: Described herein is a method and system of distributed acoustic sensing, such as in an urban or metropolitan area involving a dedicated and established fibre optic communications network including a data centre. In general, the disclosed method and system includes the steps of (a) selecting an optical fibre cable installation having a path extending across a selected geographical area, the optical fibre cable installation including a bundle of optical fibres and forming part of a fibre-optic communications network, (b) determining characteristics associated with the optical fibre and/or the selected optical fibre installation, (c) transmitting outgoing light in the optical fibre, (d) receiving reflected light back scattered along the optical fibre, and (e) based on the reflected light and the determined characteristics, generating an alert signal representative of an acoustic event. The disclosed method and system may be useful in the detection of acoustic events near or within the selected geographical area.

Abstract: The present invention is to a method of adapting optical rare-earth-doped waveguide (10) having a plurality of transverse propagation modes, such that in use, signal gains of non-fundamental modes of the waveguide are attenuated relative to a signal gain of a fundamental mode of the waveguide. The waveguide (10) has a light-guiding region (45) defined by a refractive index-modifying dopant, such as Ge, which has a thermal diffusion coefficient at temperature T in the waveguide greater than a thermal diffusion coefficient of the rare-earth dopant at temperature T. The method comprises heating the waveguide (10) at the temperature T such that a concentration profile of the refractive index-modifying dopant becomes broader than a concentration profile of the rare-earth dopant.

Abstract: The present invention provides a method and apparatus for obtaining a measure of the chromatic dispersion of a fibre bragg grating, the method comprising: disposing the grating in a reflection arm of an interferometer; inputting probe laser light into the interferometer; stepping the wavelength of the light across the reflection bandwidth of the grating, while at each step modulating the wavelength by a wavelength modulation less than the size of the respective step, and thereby producing a resulting phase modulation; and demodulating the phase modulation and determining therefrom a measure of the chromatic dispersion.

Abstract: The present invention is to a method of adapting optical rare-earth-doped waveguide (10) having a plurality of transverse propagation modes, such that in use, signal gains of non-fundamental modes of the waveguide are attenuated relative to a signal gain of a fundamental mode of the waveguide. The waveguide (10) has a light-guiding region (45) defined by a refractive index-modifying dopant, such as Ge, which has a thermal diffusion coefficient at temperature T in the waveguide greater than a thermal diffusion coefficient of the rare-earth dopant at temperature T. The method comprises heating the waveguide (10) at the temperature T such that a concentration profile of the refractive index-modifying dopant becomes broader than a concentration profile of the rare-earth dopant.