A method of measuring the state or condition of spatially spaced apart machine parts subject to wear and emitting an acoustic signature. The method includes: (a) optically sensing the acoustic properties of the machine parts subject to wear, and deriving sensed signals there from, (b) dividing the sensed signals into a first series of corresponding spatial segments along the spaced apart machine parts and, for each spatial segment, dividing the sensed signal into a temporal segment recording the acoustic properties for the spatial segment over an extended time period; (c) dividing each temporal segment into a series of sub-segments and frequency domain transforming the sub-segments into corresponding frequency domain sub-segments; (d) combining the frequency domain sub-segments within a spatial segment, to produce a corresponding lower noise level combined frequency domain sub segment; and (e) determining the fundamental frequency of the emitted acoustic signatures present in the combined frequency domain sub segment, and associated harmonics.

A system and method are provided for distributed acoustic sensing in a multimode optical fiber. The system includes a transmitter for simultaneously propagating a sequence of M light pulses through the multimode optical fiber using a spatial mode selected from a set of N spatial modes provided by a spatial mode selector for the transmitter that is coupled to an input to the multimode optical fiber, with M and N being respective integers greater than one. The system further includes a receiver for receiving the sequence of M light pulses at an output of the multimode optical fiber and detecting an environmental perturbation in the multimode optical fiber based on an evaluation of a propagation of the sequence of M light pulses through the multimode optical fiber.

A system and method are provided for distributed acoustic sensing in a multicore optical fiber. The system includes a transmitter for simultaneously propagating a sequence of M light pulses through the multicore optical fiber using a spatial mode selected from a set of N spatial modes provided by a spatial mode selector for the transmitter that is coupled to an input to the multicore optical fiber, with M and N being respective integers greater than one. The system further includes a receiver for receiving the sequence of M light pulses at an output of the multicore optical fiber and detecting an environmental perturbation in the multicore optical fiber based on an evaluation of a propagation of the sequence of M light pulses through the multicore optical fiber.

Provided are methods and apparatuses for testing imaging devices, which can include a testing apparatus a testing apparatus including a test chamber; a device receptacle inside the test chamber for holding a device under test; a target receptacle inside the test chamber for holding an optical target within a field of view of the device under test; a temperature controller configured to adjust a temperature proximate to the device receptacle; and an air curtain controller configured to generate an air curtain inside the test chamber between a location of the device receptacle and a location of the target receptacle, the air curtain thermally isolating the device receptacle from the target receptacle.

A high-durability and long-scale-distance fiber grating sensor and a manufacturing method therefor, which relate to the technical field of fiber grating sensors. A fiber grating is disposed on the middle segment of a commercial optical fiber. A bushing, a woven fiber jacket layer, and a packaging structure are disposed on the periphery of the commercial optical fiber. The commercial optical fiber and the bushing therebetween are fixed by using fixing points in the bushing. Anchoring segments are disposed between the fixing points in the bushing and the woven fiber jacket layer. Two ends of the commercial optical fiber are sequentially connected to optical fibers on the anchoring segments and connecting optical fibers. Tail ends of the connecting optical fibers are connected to a transmission cable by using connecting flanges. By using the apparatus and the manufacturing method, the applicability and the durability of application of the fiber grating sensor in the civil traffic engineering field are improved, thereby providing a stable and reliable apparatus for long-time detection and sound monitoring of large engineering structures in the civil traffic engineering field.

Various embodiments may provide a strain-sensing apparatus configured to be attached to a micrometeoroid and orbital debris (MMOD) shielding layer and data collection equipment in communication with the strain-sensing apparatus configured to detect an occurrence, a time, a location, and/or a severity of a MMOD strike on the MMOD shielding layer. The various embodiments may enable detection and/or location of potentially harmful MMOD strikes on both human occupied and unmanned spacecraft.

An apparatus for measuring state variables with at least one fiber-optic sensor, containing at least one optical coupler, at least one filter element and at least one photoelectric converter, where the optical coupler, the filter element and the photoelectric converter are integrated on a substrate, and the filter element contains at least one Bragg grating which is designed to supply the light portion reflected by the Bragg grating to the photoelectric converter.

Disclosed embodiments include a distributed nondestructive inspection method and system for slickline cable structural defect and mechanical strength degradation inspection. One method may include transmitting a light pulse along an optical fiber embedded in a slickline cable. A reflected light signal is received from the optical fiber in response to the local strain induced refractive index variation. Defects and mechanical strength degradation may be determined by time-dependent time-domain and frequency-domain data analyses of the dynamic strain signals and power spectral density variation as a function of time and cable location.

A measuring method for detecting a mechanical force acting on an object using a fiber optic sensor unit is disclosed. At least one measuring channel has a sensor fiber with a fiber Bragg grating embedded in the sensor fiber with a Bragg wavelength and a sensor detection element. The sensor fiber is fixed to the object in the area of the sensor FBG. The method includes coupling light from a light source into the sensor fiber and detecting the light reflected and/or transmitted by the sensor FBG by the sensor detection element. The light source has a wavelength-dependent intensity distribution with an edge. A wavelength change in the Bragg wavelength of the sensor FBG is determined by evaluating a measurement signal which has an intensity change in the detected light intensity of the entire light reflected by the sensor FBG and/or of the entire light transmitted by the sensor FBG.

A method, system, and computer program product for determining a core-to-ferrule offset of a ferrule for a fiber optic connector. A reference ferrule is physically aligned with a core imager by positioning the reference ferrule so that edges of the reference ferrule in a plurality of profile images are aligned with fiducial markers in the images. The reference ferrule is incrementally rotated about its longitudinal center access, a core image captured at each rotational angle, and a reference core-to-ferrule offset determined based on the core images. A test ferrule is physically aligned with the core imager by positioning the test ferrule so that edges of the test ferule are aligned with the edges of the reference ferrule in a plurality of profile images. The core-to-ferrule offset of the test ferrule is then determined based on an offset between the test and reference cores in a composite core image.