An optical cable (31) includes: a stress wave detection optical cable (30) having an optical fiber (7) and a plurality of first steel wires (8) which are helically wound so as to surround the optical fiber (7) and which are surrounded by a flexible material (9); and second steel wires (32) different from the first steel wires (8). The stress wave detection optical cable (30) and the plurality of second steel wires (32) are helically wound to form one annular body as a whole, and a winding angle (α) of the stress wave detection optical cable (30) with respect to the axis is determined by a property value prescribed by Lamé constants of the flexible material (9).

An optical fiber sensing system according to the present disclosure includes a receiving unit (21) configured to receive an optical signal from an optical fiber (10) for sensing, an identifying unit (22) configured to identify an occurrence of an event and a type of the event that has occurred based on a vibration pattern included in the optical signal, an acquiring unit (23) configured to acquire a detection condition pertaining to a period corresponding to the type of the event identified by the identifying unit (22), and a determining unit (24) configured to determine that the event identified by the identifying unit (22) is an anomaly if the detection condition is satisfied.

A light receiver outputs a log indicating at least one of an operating status of a multiple optical axis photoelectric sensor and an environment surrounding the multiple optical axis photoelectric sensor, at the time of an output being turned off.

A light receiver outputs a log indicating at least one of an operating status of a multiple optical axis photoelectric sensor and an environment surrounding the multiple optical axis photoelectric sensor, at the time of an output being turned off.

A method (400) of determining blade tip deflection characteristics is applied to moving rotor blades (R.sub.1, R.sub.2) in a turbomachine (10) comprising a housing and rotor including a shaft with the rotor blades attached thereto and at least one proximity probe (202). The method (400) includes measuring ((402) a proximity signal caused by a presence of a proximate tip of a moving rotor blade (R.sub.1) and calculating (404) by a control module (212) a shaft Instantaneous Angular Position (IAP) as a function of time, and performing (410) an order tracking process which includes expressing (412) the measured proximity signal in the angular domain and resampling (414) the expressed proximity signal to render it equidistant in the angular domain. The method (400) includes performing (416) a pulse localisation process which includes filtering (418) the proximity signal yielding a complex-valued response, expressing (420) the complex-valued response in terms of a local amplitude and phase, and calculating (422) local phase shifts between each expressed signal and a reference signal.

A method (400) of determining blade tip deflection characteristics is applied to moving rotor blades (R.sub.1, R.sub.2) in a turbomachine (10) comprising a housing and rotor including a shaft with the rotor blades attached thereto and at least one proximity probe (202). The method (400) includes measuring ((402) a proximity signal caused by a presence of a proximate tip of a moving rotor blade (R.sub.1) and calculating (404) by a control module (212) a shaft Instantaneous Angular Position (IAP) as a function of time, and performing (410) an order tracking process which includes expressing (412) the measured proximity signal in the angular domain and resampling (414) the expressed proximity signal to render it equidistant in the angular domain. The method (400) includes performing (416) a pulse localisation process which includes filtering (418) the proximity signal yielding a complex-valued response, expressing (420) the complex-valued response in terms of a local amplitude and phase, and calculating (422) local phase shifts between each expressed signal and a reference signal.

An accelerometer structure, a method for preparing the accelerometer structure and an acceleration measurement method are provided. The accelerometer structure includes a substrate having a groove structure, a test mass, a plurality of nano-tethers, and a nano-photonic-crystal measurement unit. The test mass, nano-tethers, and the nano-photonic-crystal measurement unit are suspended above the groove structure. A nano-photonic-crystal resonant cavity is formed in the nano-photonic-crystal measurement unit, and an acceleration of the test mass is characterized by a resonant frequency of the nano-photonic-crystal resonant cavity. The present disclosure provides a photoelasticity-based opto-micromechanical accelerometer structure, which uses a cavity resonance tension sensor in a nano-photonic-crystal cavity to measure a tension of the nano-photonic-crystal resonant cavity. The tension is concentrated in the nano-photonic-crystal resonant cavity, which makes the measurement of the tension more accurate and the resolution higher. Photoelastic-optomechanical coupling is also increased due to the nano-photonic-crystal resonant cavity.

An accelerometer structure, a method for preparing the accelerometer structure and an acceleration measurement method are provided. The accelerometer structure includes a substrate having a groove structure, a test mass, a plurality of nano-tethers, and a nano-photonic-crystal measurement unit. The test mass, nano-tethers, and the nano-photonic-crystal measurement unit are suspended above the groove structure. A nano-photonic-crystal resonant cavity is formed in the nano-photonic-crystal measurement unit, and an acceleration of the test mass is characterized by a resonant frequency of the nano-photonic-crystal resonant cavity. The present disclosure provides a photoelasticity-based opto-micromechanical accelerometer structure, which uses a cavity resonance tension sensor in a nano-photonic-crystal cavity to measure a tension of the nano-photonic-crystal resonant cavity. The tension is concentrated in the nano-photonic-crystal resonant cavity, which makes the measurement of the tension more accurate and the resolution higher. Photoelastic-optomechanical coupling is also increased due to the nano-photonic-crystal resonant cavity.

There is described a method for interrogating optical fiber comprising fiber Bragg gratings (“FBGs”), using an optical fiber interrogator. The method comprises (a) generating an initial light pulse from phase coherent light emitted from a light source, wherein the initial light pulse is generated by modulating the intensity of the light; (b) splitting the initial light pulse into a pair of light pulses; (c) causing one of the light pulses to be delayed relative to the other of the light pulses; (d) transmitting the light pulses along the optical fiber; (e) receiving reflections of the light pulses off the FBGs; and (f) determining whether an optical path length between the FBGs has changed from an interference pattern resulting from the reflections of the light pulses.

A system for continuously monitoring at least one machine including a plurality of magnetic sensors synchronously sensing magnetic fields emitted by at least one machine, the plurality of magnetic sensors sensing the magnetic fields along a corresponding plurality of channels and outputting magnetic field emission signals corresponding to the magnetic fields, a signal analyzer receiving at least a portion of the magnetic field emission signals and performing analysis of the magnetic field emission signals, the signal analyzer providing an output based on the analysis, the output including at least an indication of a condition of the at least one machine and a control module receiving the indication of the condition and initiating at least one of a repair event on the at least one machine, an adjustment to a maintenance schedule of the at least one machine and an adjustment to an operating parameter of the at least one machine based on the indication, whereby efficacy of the at least one machine is improved.