Laser Institute of Shandong Academy of Science

Qilu University of Technology

Qilu University of Technology(shandong Academy of Sciences)

Laser Institute of Shandong Academy of Sciences

Chang Wang

Jiasheng Ni

Chen Wang

Chang Li

Bing Cao

Ying Shang

Yingying Wang

Sheng Huang

Wenan Zhao

Xiaohui Liu

Long Ma

Yanbin Wu

Gangding Peng

Wen'an Zhao

Shaodong Jiang

Qingchao Zhao

Faxiang Zhang

Yang Liu

Zhiqiang Song

Jian Guo

Haifeng Qi

Weitao Wang

Xiaolei Zhang

Hui Li

An EHz ultrafast modulated pulse scanning laser and a distributed fiber sensing system. A plurality of phase-shift gratings are engraved on a doped fiber, the phase-shift gratings having different central window wavelengths and a wavelength interval between the adjacent central window wavelengths being a preset fixed value. When a pump light emitted by a pump laser source is coupled by a wavelength division multiplexer and enters the doped fiber, a single-mode narrow-linewidth laser light having multiple wavelengths with a wavelength interval being a preset fixed value can be generated, by using the phase-shift gratings graved on the doped fiber. The ultrafast modulation is completed by using a time-domain control method based on an EOM. An internally frequency converted pulse light formed by splicing pulse lights whose frequencies linearly increase is obtained, thus forming the EHz ultrafast modulation of a distributed feedback fiber laser. In this way, a coherence length of an output laser light is increased while a frequency of the laser light is remained.

EHz ultrafast modulated pulse scanning laser and distributed fiber sensing system

An optical fiber inclination measurement apparatus and a differential inclination measurement system are provided, which is related to the field of monitoring technology. The apparatus includes a supporting mechanism with a base and a base frame, a swinging mechanism with a pendulum, a cycloid, and a first reflective film is disposed on the pendulum. The measurement mechanism includes a first optical fiber, and an end surface of the first optical fiber is disposed opposite to the first reflective film. During an earthquake generating process, a landform changes and the pendulum swings, resulting in changes in displacement. The end surface of the first optical fiber together with the first reflective film form a Fabry-Perot cavity. The cavity length of the Fabry-Perot cavity changes before and after the landform deforms, and an angle of inclination is equal to a value obtained by dividing the cavity length variation of the Fabry-Perot cavity by the pendulum length.

Optical fiber inclination measurement apparatus and differential inclination measurement system

The present application discloses a fiber distributed acoustic sensing system, including a forward pump source, a wavelength division multiplexer, an active phase-shifted grating array, a backward pump source, and a data demodulation and processing device. The active phase-shifted grating array includes several active phase-shifted gratings engraved on a same fiber, each active phase-shifted grating having a same excitation light wavelength. The active phase-shifted grating array is configured to receive a forward pump pulse and a backward pump light pulse incident from the backward pump source, so that a forward excitation light and a backward excitation light are generated in each active phase-shifted grating, and two adjacent active phase-shifted gratings are enabled to generate excitation light self interference within a same pulse duration. The data demodulation and processing device is configured to perform interference detection on a fiber phase between two adjacent active phase-shifted gratings to detect an acoustic signal acted on the fiber. According to the system in the present application, the passive reflected light interference is replaced with active excitation light interference, thus the excitation light signal has great strength and high stability, and environmental adaptability is high.

Fiber distributed acoustic sensing system

A high-performance distributed fiber sensing system based on EHz ultrafast pulse scanning. During testing of a disturbance signal, an internally frequency converted pulse light emitted by an EHz ultrafast pulse scanning laser enters a sensing fiber after passing through a circulator, and a backward Rayleigh scattering signal transmitted by the sensing fiber enters an unbalanced Michelson interferometer after passing through a coupler. By designing an arm length difference between two interference arms, interferences sequentially occur for the backward Rayleigh scattering light at a position where lengths of two adjacent arms differ. A signal received after passing through the unbalanced Michelson interferometer includes a phase difference signal caused by an external disturbance signal in the sensing fiber. Finally, variations of the phase difference signal over time are demodulated by using a phase demodulation unit, so that a dynamic measurement of the disturbance signal in the sensing fiber may be performed.

High-performance distributed fiber sensing system based on EHz ultrafast pulse scanning

The present invention provides an event positioning method, device and application in a distributed fiber vibration monitoring system. When a location at which an event occurs in a sensing fiber is to be positioned, an interference field signal having a maximum optical power is obtained by comparing optical powers of respective interference field signals corresponding to backward Rayleigh scattering lights that are generated when a pulse light is transmitted in the sensing fiber. Subsequently, a sensing location of the interference field signal having the maximum optical power is calculated. Finally, the location at which the event occurs in the sensing fiber is determined, according to the sensing location and a location distribution pattern of the event. According to the positioning method provided in the present invention, by screening the interference field signals and then calculating the event location, the spatial resolution is not determined merely by the pulse width of the optical signal. Therefore, the location positioning of the event can be more accurate, thereby improving an accuracy of the spatial resolution.

Event positioning method, device and application in distributed fiber vibration monitoring system

An optical fiber flow sensor, including: a housing, an elastic component, an optical fiber detection component, a floating element, and a fixed sealing joint. The elastic component includes a first and second elastic members that are symmetrical and are disposed in a closely fitted manner, with fitting surfaces of the first and the second elastic members being respectively provided with a corresponding seating groove. The optical fiber detection component is disposed in the seating grooves, and both ends of the optical fiber detection component are welded in the seating grooves via a glass solder. The elastic component is enclosed in the housing, and one end of the housing is fixed at the fixed sealing joint. The optical fiber detection component is sealed within the elastic component so as to avoid direct contact with an external fluid, and prevent damage by corrosion, hydrogen loss, or the like. The optical fiber detection component is welded to the elastic component via a glass solder, thereby avoiding a high-temperature creep deformation of the glue and thermal mismatch.

Optical fiber flow sensor

An optical fiber distributed monitoring system and method is provided. The system includes a laser device, an acousto-optic modulator, a phase matching interferometer, a photoelectric detector and a phase demodulation module. After entering the phase matching interferometer, the Rayleigh backscattering light containing parameter information output from the sensing optical fiber enters the two arms of the phase matching interferometer respectively, and the light of the two arms of the phase matching interferometer is phase-modulated by the first modulation wave and the second modulation wave, respectively and then interfere with each other to generate interference light. The photoelectric detector converts a light signal into an electric signal, and the phase demodulation module processes the electric signal based on the Hilbert algorithm to obtain the parameter change of the environment under test.

Optical fiber distributed monitoring system and method

Provided are a temperature sensor and an active phase-shifted grating-based temperature sensing system, relating to a fiber sensing technical field. The temperature sensor comprises a pump laser, a wavelength division multiplexer, an optical detector and an active phase-shifted fiber grating with &#x3c0; phase shift. Pump light emitted by the pump laser enters the active phase-shifted fiber grating through the wavelength division multiplexer. The active phase-shifted fiber grating absorbs the pump light and emits laser light, which travels back through the wavelength division multiplexer and enters the optical detector. The optical detector measures output power of the active phase-shifted fiber grating, to analyze the power to obtain ambient temperature of the active phase-shifted fiber grating. Compared with wavelength demodulation based fiber grating sensors, this temperature sensor can obtain ambient temperature of the active phase-shifted fiber grating solely by analyzing output power of the active phase-shifted fiber grating measured by the optical detector.

Temperature sensor and temperature sensing system based on active phase-shifted fibre grating

Provided is a fiber optic acoustic wave detection system, pertaining to the fiber optic sensing technical field. The system comprises a power output apparatus, a backward Rayleigh scattering principle-based first distributed sensing apparatus, a backward weak optical fiber grating reflection principle-based second distributed sensing apparatus, and a third distributed sensing apparatus. The first distributed sensing apparatus and the second distributed sensing apparatus are connected with the power output apparatus, respectively. The first distributed sensing apparatus and the second distributed sensing apparatus are connected with the third distributed sensing apparatus, respectively. Compared with conventional approaches, the signal contrast and sensitivity of the detection system are greatly improved by combining the backward Rayleigh scattered signal in the first distributed sensing apparatus with the backward weak optical fiber grating reflected signal in the second distributed sensing apparatus, and the detection system detection bandwidth is significantly widened by the third distributed sensing apparatus.

Fiber optic acoustic wave detection system

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Jinan, China

Chang Wang