Abstract: A compounded light-focusing optical element is configured to focus light, and the compounded light-focusing optical element includes a body having a first, flat, end face and a second, curved end face, the second, curved end face being opposite to the first, flat end face, and plural optical fibers extending through the body, from the first, flat end face to the second, curved end face. The plural optical fibers are fused to each other to form the body, and end faces of the plural optical fibers, corresponding to the second, curved end face, are pointing in different directions.

Abstract: The subject matter of this specification can be embodied in, among other things, a method for removing intermodal distortion that includes receiving a collection of distorted backscattered Rayleigh signals from a collection of modes of an optical fiber, where the collection of distorted backscattered Rayleigh signals are distorted by an intermodal coupling among the collection of modes, receiving a collection of distortion parameters that are descriptive of distortion effects of the intermodal coupling, and determining an undistorted backscattered Rayleigh signal based on the collection of distorted backscattered Rayleigh signals and the collection of distortion parameters.

Abstract: A system and methods for monitoring internal corrosion in a compromised pipe are provided. An exemplary includes applying a reinforcement layer on an outer surface of a pipe over a defect detected in an internal surface of the pipe. A testing fiber Bragg grating (FBG) detector is mounted on the outer surface of the pipe over the defect. A reference FBG detector is mounted on the outer surface of the pipe. A difference in hoop strain between the testing FBG detector and the reference FBG detector is monitored to identify variations in wall thickness over the defect.

Abstract: A method for monitoring pipeline integrity is provided. The method includes obtaining, using at least one hardware processor, acoustic signal captured by at least one optical fiber arranged along a pipeline. The method includes inputting, using the at least one hardware processor, the acoustic signal to a machine learning model. The machine learning model is trained to execute a first analysis on a first representation of the acoustic signal and a second analysis on a second representation of the acoustic signal, the first analysis being independent to the second analysis. An output of the trained machine learning model is at least one of a first result based on the first analysis or a second result based on the second analysis. The method includes determining, using the at least one hardware processor, an indication of pipeline integrity based on the at least one of the first result or the second result.

Abstract: An integrated system for detecting a red palm weevil (RPW), farm fire, and soil moisture includes an optical fiber configured to be extending to a tree, and a distributed acoustic sensor (DAS) box connected to the optical fiber. The DAS box is configured to process first to third different optical signals reflected from the optical fiber, to determine a presence of the RPW from the first optical signal, a temperature at a location along the optical fiber from the second optical signals, and a moisture at a location around the tree from the third optical signal.

Abstract: A fiber optic distributed acoustic sensing (DAS) system for detecting a red palm weevil (RPW) includes an optical fiber configured to be wrapped around a tree and a DAS box connected to the optical fiber. The DAS box includes a processing unit that is configured to receive a filtered Rayleigh signal reflected by the optical fiber, and run the filtered Rayleigh signal through a neural network system to determine a presence of the RPW in the tree.

Abstract: A method for determining tree infestation includes placing an optical fiber around a trunk of a tree; recording with a distributed acoustic sensor (DAS) box a Rayleigh signal reflected from the tree, along the optical fiber; processing the Rayleigh signal to obtain a processed signal; calculating a signal-to-noise ratio (SNR) of the processed signal for the tree; and comparing the SNR to a threshold value and counting an alarm if the SNR is larger than the threshold value. The SNR is defined as a ratio between (1) a maximum value of a processed signal and (2) a minimum value of the processed signal.

Abstract: The subject matter of this specification can be embodied in, among other things, a method for removing intermodal distortion that includes receiving a collection of distorted backscattered Rayleigh signals from a collection of modes of an optical fiber, where the collection of distorted backscattered Rayleigh signals are distorted by an intermodal coupling among the collection of modes, receiving a collection of distortion parameters that are descriptive of distortion effects of the intermodal coupling, and determining an undistorted backscattered Rayleigh signal based on the collection of distorted backscattered Rayleigh signals and the collection of distortion parameters.

Abstract: The subject matter of this specification can be embodied in, among other things, a method for removing intermodal distortion that includes receiving a collection of distorted backscattered Rayleigh signals from a collection of modes of an optical fiber, where the collection of distorted backscattered Rayleigh signals are distorted by an intermodal coupling among the collection of modes, receiving a collection of distortion parameters that are descriptive of distortion effects of the intermodal coupling, and determining an undistorted backscattered Rayleigh signal based on the collection of distorted backscattered Rayleigh signals and the collection of distortion parameters.

Abstract: A hybrid sensing-communication system includes a multicore optical fiber that includes first and second cores, a first communication device optically coupled to a first end of the first core of the multicore optical fiber, a second communication device optically coupled to a second end of the first core of the multicore optical fiber, a first sensing device optically coupled to a first end of the second core of the multicore optical fiber, and a second sensing device optically coupled to a second end of the second core of the multicore optical fiber. The first and second communication devices exclusively exchange communication data along the first core, the first and second sensing devices exclusively exchange sensing data along the second core, and the communication data is different from the sensing data.

Abstract: A compounded light-focusing optical element is configured to focus light, and the compounded light-focusing optical element includes a body having a first, flat, end face and a second, curved end face, the second, curved end face being opposite to the first, flat end face, and plural optical fibers extending through the body, from the first, flat end face to the second, curved end face. The plural optical fibers are fused to each other to form the body, and end faces of the plural optical fibers, corresponding to the second, curved end face, are pointing in different directions.

Abstract: An optical fiber distributed acoustic sensor (DAS) system for detecting a red palm weevil and/or its larvae inside a tree. The system includes an optical fiber that is configured to be placed next to a tree; and a DAS box optically connected to the optical fiber and configured to receive a reflected light from the optical fiber. The DAS box includes electronics that extracts from the reflected light a frequency in a range of [400 Hz, 4 kHz], and sends a message indicating a presence of the red palm weevil and/or its larvae inside the tree.

Abstract: The subject matter of this specification can be embodied in, among other things, a method for remotely sensing vibration includes transmitting a collection of optical pulses through an optical fiber at a predetermined frequency, detecting a collection of backscattered Rayleigh traces from the optical fiber based on a vibration of the optical fiber at a vibration frequency at a location along the optical fiber, determining a normalized differential trace based on the collection of Rayleigh traces, determining, based on the normalized differential trace, the location in the optical fiber of the vibration, and determining, based on the raw Rayleigh traces, the vibration frequency.

Abstract: A fiber optic distributed acoustic sensing (DAS) system for detecting a red palm weevil (RPW) includes an optical fiber configured to be wrapped around a tree and a DAS box connected to the optical fiber. The DAS box includes a processing unit that is configured to receive a filtered Rayleigh signal reflected by the optical fiber, and run the filtered Rayleigh signal through a neural network system to determine a presence of the RPW in the tree.

Abstract: A hybrid sensing-communication system includes a multicore optical fiber that includes first and second cores, a first communication device optically coupled to a first end of the first core of the multicore optical fiber, a second communication device optically coupled to a second end of the first core of the multicore optical fiber, a first sensing device optically coupled to a first end of the second core of the multicore optical fiber, and a second sensing device optically coupled to a second end of the second core of the multicore optical fiber. The first and second communication devices exclusively exchange communication data along the first core, the first and second sensing devices exclusively exchange sensing data along the second core, and the communication data is different from the sensing data.

Abstract: Systems and methods include a method for overcoming optical time domain reflectometry (OTDR) dead zone limitations by using a few-mode fiber (FMF). Optical pulses are transmitted by a transmitter of an OTDR system through a mode MUX/DEMUX into an FMF. Light signals directed by the FMF in a backward direction through the mode MUX/DEMUX are received by the OTDR system through N single-mode fiber (SMF) ports corresponding to N modes in the FMF. Light signals from N?1 dead-zone-free SMF ports are collected by the OTDR system. Losses are measured and faults are located in the FMF based at least on the light signals.

Abstract: A method for determining tree infestation includes placing an optical fiber around a trunk of a tree; recording with a distributed acoustic sensor (DAS) box a Rayleigh signal reflected from the tree, along the optical fiber; processing the Rayleigh signal to obtain a processed signal; calculating a signal-to-noise ratio (SNR) of the processed signal for the tree; and comparing the SNR to a threshold value and counting an alarm if the SNR is larger than the threshold value. The SNR is defined as a ratio between (1) a maximum value of a processed signal and (2) a minimum value of the processed signal.

Abstract: An integrated system for detecting a red palm weevil (RPW), farm fire, and soil moisture includes an optical fiber configured to be extending to a tree, and a distributed acoustic sensor (DAS) box connected to the optical fiber. The DAS box is configured to process first to third different optical signals reflected from the optical fiber, to determine a presence of the RPW from the first optical signal, a temperature at a location along the optical fiber from the second optical signals, and a moisture at a location around the tree from the third optical signal.

Abstract: The subject matter of this specification can be embodied in, among other things, a method that includes separating, from a few mode optical fiber, a collection of backscattered Rayleigh signals based on a vibration of the few mode optical fiber at a vibration frequency at a first location along the few mode optical fiber, separating, from the few mode optical fiber, a collection of backscattered Stokes Raman signals and Anti-Stokes Raman signals based on a temperature of the few mode optical fiber at a second location along the few mode optical fiber, detecting the separated Rayleigh signals and Raman signals, determining, based on detecting the collection of backscattered Rayleigh traces, at least one of the first location, the vibration frequency, and an amplitude of the vibration, and determining, based on the detecting the collection of backscattered Raman signals, the temperature at the second location.

Abstract: Systems and methods include a method for overcoming optical time domain reflectometry (OTDR) dead zone limitations by using a few-mode fiber (FMF). Optical pulses are transmitted by a transmitter of an OTDR system through a mode MUX/DEMUX into an FMF. Light signals directed by the FMF in a backward direction through the mode MUX/DEMUX are received by the OTDR system through N single-mode fiber (SMF) ports corresponding to N modes in the FMF. Light signals from N?1 dead-zone-free SMF ports are collected by the OTDR system. Losses are measured and faults are located in the FMF based at least on the light signals.