An acoustic sensor that uses an optical fiber and has a high directivity is provided. An acoustic sensor includes a sensing part and an interrogator. The sensing part has a sensing element composed of an optical fiber. The interrogator is connected to the sensing part, sends a pulse light P to the sensing part, and detects an acoustic wave sensed by the sensing part based on a reflected return light from the sensing part. The sensing element is composed of the optical fiber folded in such a way that it reciprocates a plurality of number of times along a directivity direction in which directional sensitivity is exhibited.

To apply an optical amplification repeater device to optical fiber sensing to lengthen a sensing range, as well as to enable compatibility with an optical communication system a cable system that uses a cable for optical fiber communication and optical fiber sensing of an environment surrounding the cable, wherein: the optical fiber communication is bidirectional communication using optical fiber pairs which are pairs of the optical fiber; in an optical fiber, a first wavelength band and a second wavelength band are different from each other; an optical amplification unit included in the optical amplification repeater device includes a first amplifier and a second amplifier that amplify rays of light in mutually opposing directions; and each of the communication optical signal, the probe light, and the backscattering light is amplified by at least either the first amplifier or the second amplifier.

Apparatus, systems, and techniques for extending distributed acoustic sensing (DAS) range in undersea optical cables over multiple spans, as well as providing span-specific DAS information, are provided.

An optical fiber sensing system according to the present disclosure includes an optical fiber (10A) configured to detect a vibration in underground, an acquisition unit (21) configured to acquire, from the optical fiber (10A), an optical signal on which the vibration detected by the optical fiber (10A) is superimposed, and an identifying unit (22) configured to identify a suspicious action in the underground based on a vibration pattern included in the optical signal acquired by the acquisition unit (21).

A device for coupling a sensor to a fiber optic cable including at least one optical fiber, the device may include an activation unit couplable to a known coupling location along the fiber optic cable and configured to: receive an analog sensor output signal from the sensor and change one or more properties of at least one of: one or more optical wave propagating through the at least one optical fiber and the at least one optical fiber, with respect to the analog output signal, while maintaining at least a portion of a spectral content of the analog sensor output signal during at least a portion of time.

A fluid properties sensing system includes an optical sensor which generates a sensor signal based on received laser light, a light source which transmits laser light through a transmitting fiber to a sensor head, a receiver that detects a portion of the laser light from a receiving fiber through an evanescent field of the transmitting fiber when the laser light radiates through a transmitting fiber wall of the transmitting fiber and interacts with a fluid medium at an interface of the sensor and the fluid medium, and a processor. The fibers are coupled at one end through the evanescent field to form the sensor head disposed in a flow field and to interact with the fluid medium. The processor identifies a change in the sensor signal based on a detected portion of the laser light resulting from an interaction of the sensor head with the fluid medium.

A method of detecting one or more events comprises determining a plurality of temperature features from a temperature sensing signal, using the plurality of temperature features in an event detection model, and determining the presence or absence of the one or more events at one or more locations based on an output from the event detection model.

A testing procedure including a data collection procedure and a contrastive learning-based approach, for establishing a profile for utility poles surveyed in an embedding space. Unique properties of utility poles are preserved in a low-dimensional feature vector. Similarities between pairs of samples collected at the same or different poles is reflected by the Euclidean distance between the pole embeddings. During data collection—variabilities of excitation signals are manually introduced, e.g. impact strength, impact locations, impact time ambiguity, data collecting location ambiguity on a DFOS/DAS optical sensor fiber/cable. Data so collected provides a learned model learned complete information about a utility pole and is more robust with respect to uncontrollable factors during operation. A model training procedure that effectively extracts a utility pole intrinsic properties (e.g., structure integrity, dimensions, structure variety) and remote extrinsic influence (e.g., excitation strength, weather conditions, road traffic), without knowing the ground truth of these factors. The only identifying label required is an ID of any tested poles, which is readily available. The model is trained adaptively—end-to-end—is advantageously easy-to-implement on modern deep learning frameworks such as PyTorch.

A sensor (10) comprises a waveguide (20) having a longitudinal axis and an end face (21), the waveguide (20) comprising a Bragg grating (23). The sensor comprises at least one reflector (24) on the end face (21) of the waveguide (20). An optical resonator (25) is formed by the Bragg grating (23), the at least one reflector (24), and an inner portion of the optical resonator (25) between the Bragg grating (23) and the at least one reflector (24). The inner portion of the optical resonator (25) extends within a portion of the waveguide (20). The sensor (10) comprises a detector (32) configured to detect at least one spectral characteristic of the optical resonator (25) or a change of at least one spectral characteristic of the optical resonator (25).

An optical sensing system for detecting fiber events along an optical cable under test (CUT) having forward and feedback fibers and multiple pairs of optical couplers interconnected along the forward and feedback fibers in a ladder topology. An optical transmitter generates an optical probing signal for a forward fiber, wherein the couplers along the forward fiber provide tapped portions of the probing signal to the couplers along a feedback fiber to form a combined optical feedback signal in the feedback fiber. A reference coupler is connected between the transmitter and the forward fiber to tap an optical reference signal from the probing signal, and a feedback coupler is connected to combine the reference signal and the feedback signal. An optical receiver receives and processes the combined reference and feedback signals from the feedback coupler to detect fiber events along the CUT.