Torsion Sensor Research Articles

Helical Long-Period Grating Through a Commercial CO2 Laser Fiber Processing Machine for Torsion Sensor Applications

Helical Long-Period Grating Through a Commercial CO₂ Laser Fiber Processing Machine for Torsion Sensor Applications

Optical Fiber Surface Plasmon Resonance Torsion Sensor Based on Threaded Structure

Optical Fiber Surface Plasmon Resonance Torsion Sensor Based on Threaded Structure

Compact Torsion Sensor With High Sensitivity Using Angle-Offset Long Period Grating Inscribed in Multicore Fiber

Compact Torsion Sensor With High Sensitivity Using Angle-Offset Long Period Grating Inscribed in Multicore Fiber

High sensitivity and directional recognition torsion sensor based on rotating distributed slot long-period fiber grating

In this paper, a rotationally distributed slot type long period fiber grating torsion sensor is proposed. The sensor employs CO2 laser to etch grooves on the fiber surface in a structure helically distributed slot around the fiber axis, which breaks the circular symmetry of the fiber and introduces a residual twisting force, thus introducing a large amount of elliptical birefringence. By investigating the effect of different periods on the torsional sensitivity, the torsional sensitivity is effectively improved. The experimental results indicate that the torsion sensitivity of the sensor is up to 0.42 nm/(rad/m) in the measurement range of −13.08 rad/m to 13.08 rad/m, which is 10 times more sensitive than that of the traditional torsion sensor, and the direction of torsion can be detected. The temperature characteristics of the sensor are also investigated, and the temperature sensitivity in the detection range of 30 °C to 120 °C is 76 pm/°C, with a temperature crosstalk of 0.18(rad/m)/°C. This sensor provides a new solution for LPFG torsion sensing enhancement, which can be used in the field of engineering structure monitoring with high torsion sensitivity requirements.

Accuracy compensation method for 2D curve reconstruction of torsional FBG shape sensor of scraper conveyor

The straightness perception of scraper conveyor is a technology that helps to achieve intelligent operation of coal mine working faces. However, there is a problem of accuracy degradation caused by sensor torsion based on fiber Bragg grating (FBG) shape sensing technology. This paper proposes an accuracy compensation method based on torsion angle, and verifies the effectiveness of accuracy compensation through simulation and experimental research. Experimental tests have shown that when the torsion angle of the sensing substrate is 10° and 20°, the end accuracy of the reconstructed curve after accuracy compensation is increased by 2.77% and 1.93% compared to before compensation, respectively. This study indicates that compensation based on the torsion angle can significantly improve the accuracy of two-dimensional (2D) curve reconstruction, and it has broad engineering application prospects in fields such as straightness perception of scraper conveyors and monitoring of underwater pipelines.

Anti-crosstalk fiber-optic directional torsion sensor via intensity-modulated Lyot filter

In this paper, a fiber-optic directional torsion sensor based on the intensity modulated Lyot filter is completed to alleviate the crosstalk from ambient temperature and axial strain. The transmission is analyzed and compared with the varied twisted length. The experimental results show that the torsion response of 1.18 dB/° can be achieved by the 45° incident angle and 10-cm twisted length, with tiny wavelength shift (∼0.012 nm/°) and minimum range of π-phase jumping. Meanwhile, the crosstalk is well compressed within 0.006°/με and 0.23°/°C owing to ultralow axial-strain and temperature responses. In addition, an in-field test is performed electrically and the detection limit of 0.08° is witnessed experimentally.

Torsion and bending sensing based on the specklegrams from a coupled few-mode multi-core fiber

A novel optical torsion and bending dual-parameter sensor based on the detection of a coupled few-mode multi-core fiber (FM-MCF) specklegrams is proposed and experimentally demonstrated. A 3-mm-long multimode fiber (MMF) is used to couple the light from the injection single mode fiber into all cores of the FM-MCF, and thus the fiber structure is formed by the ultra-short MMF and FM-MCF. The specklegrams of the FM-MCF can be detected and segmented to infer the change of the FM-MCF. The torsion angle of 0-360° of the FM-MCF can be determined accurately by detecting the overall rotation angles of the specklegrams. And since the modes in each core of the FM-MCF are strongly coupled and the mode interference is highly sensitive to external disturbance, bending sensing based on the analysis of sub-specklegrams from each outer core is verified within the curvature range of 2.57–12.83 m−1 with the help of deep learning. Furthermore, based on a dual-output layer classification network, the capability of the sensor for torsion and bending sensing simultaneously is tested. The recognition accuracy for 36 combinations of 4 torsion angles and 9 bending states are 100% and 97.12%, respectively. The sensor here proposed has the advantages of low cost, simple structure, ease of interrogation and good accuracy.

Torsion Sensor Based on Helical Long-Period Grating Inscribed in the Etched Double Cladding Fiber

Torsion Sensor Based on Helical Long-Period Grating Inscribed in the Etched Double Cladding Fiber

Novel Torsion Sensor Based on the Interaction Between Modal Interference and Polarization Interference

Novel Torsion Sensor Based on the Interaction Between Modal Interference and Polarization Interference

Thermally stable vector torsion sensing based on cascaded long-period fiber gratings in two-mode fiber

We demonstrated a torsion sensor based on an in-fiber Mach-Zehnder interferometer (MZI), which consists of two identical cascaded long-period fiber gratings (CLPFGs) inscribed in two-mode fiber (TMF) by high-frequency CO2 laser. The transmission and mode coupling performances, as well as the spectral properties have been proved theoretically and experimentally. The proposed TMF-CLPFGs could not only be used as an efficient multi-wavelength LP01-LP11 mode converter, but also achieve the vector torsion measurements. As the twist induced, the proposed TMF-CLPFGs present vector torsion ability through the intensity of interference dips varying. The torsion sensitivity of TMF-CLPFGs with spacing length 1 cm can reach −1.07 dB/(rad/m) in counterclockwise direction and 0.9 dB/(rad/m) in clockwise direction. Moreover, the temperature sensitivity of TMF-CLPFGs was measured to be 0.055 dB/°C, which could be negligible to torsion measurement. Therefore, the proposed TMF-CLPFGs could be potential in few-mode fiber-based communication systems and sensing fields.

Strain-insensitive micro torsion and temperature sensor based on a helical taper seven-core fiber structure.

We propose a multimode interference-based optical fiber NHTSN sensor with a helical taper for simultaneous measurement of micro torsion and temperature. The sensor consists of single mode fiber (SMF), no-core fiber (NCF), and seven-core fiber (SCF). A helical taper is fabricated in the SCF using a flame heater, forming the SMF-NCF-Helical Taper SCF-NCF-SMF (NHTSN) structure. Theoretical analysis and experimental results demonstrate that the introduction of helical taper not only imparts directionality to the torsion measurement, but also results in a significant improvement in torsion sensitivity due to the increased inter-mode optical path difference (OPD) and enhanced inter-mode coupling. In the experiment, the torsion sensitivity of the NHTSN sensor reaches -1.255 nm/(rad/m) in the twist rate (TR) range of -3.931 rad/m to 3.931 rad/m, which is a 9-fold improvement over the original structure. Further reduction of the helical taper diameter increases the sensitivity to -1.690 nm/(rad/m). In addition, the sensor has a temperature sensitivity of up to 97 pm/°C from 20 °C to 90 °C, and simultaneous measurement of torsion and temperature is attainable through a dual-parameter measurement matrix. The NHTSN sensor possesses advantages of compact size, high sensitivity, good linearity, and strain-independence, endowing it with potential applications in structural health monitoring (SHM) and engineering machinery.

A Stable and Highly Sensitive Directional Torsion Sensor Based on a Helical Double Cladding Microstructured Multicore Fiber

A Stable and Highly Sensitive Directional Torsion Sensor Based on a Helical Double Cladding Microstructured Multicore Fiber

Using machine learning to enlarge the measurement range and promote the compactness of the optical fiber torsion sensor based on the Sagnac interferometer

The support vector regression (SVR) algorithm is presented to demodulate the torsion angle of an optical fiber torsion sensor based on the Sagnac interferometer with the panda fiber. Experimental results demonstrate that with the aid of SVR algorithm, the information in the transmission spectrum of the sensor can be used fully to realize the regression prediction of the directional torsion angle. The full torsion angle ranges from −360° to 360° can be predicted with a mean absolute error (MAE) of 2.24° and determination coefficient (R2) of 0.9996. The impact of the angle sampling interval and wavelength resolution of the spectrometer on the prediction accuracy of the directional torsion angle and the suitability of the SVR algorithm for compact optical fiber sensor and other optical fiber torsion sensors based on the Sagnac interferometer are discussed. Moreover, the multi-objective SVR algorithm is used to eliminate the interference of strain during torsion angle measurement. The SVR algorithm can efficiently enlarge the measurement range of the torsion angle and break through the challenge of demodulating sensing signal for compact fiber torsion sensor. Compared to the prediction accuracy of common machine learning algorithms of artificial neural network (ANN) algorithm, random forest (RF) algorithm, and K-nearest neighbor (KNN) algorithm, the SVR algorithm has the advantages of higher measurement accuracy and shorter testing time.

Helically Twisted Microstructured Polymer Optical Fiber and Its Application as a Torsion and Strain Sensor

Helically Twisted Microstructured Polymer Optical Fiber and Its Application as a Torsion and Strain Sensor

Piezoelectric PZT film-driven resonant torsional MEMS electric field sensor

Piezoelectric PZT film-driven resonant torsional MEMS electric field sensor

Artificial-neural-network-assisted distributed directional optical fiber torsion sensor with the SSAF-based Sagnac interferometer

Artificial-neural-network-assisted distributed directional optical fiber torsion sensor with the SSAF-based Sagnac interferometer

High-Sensitivity LPFG Torsion Sensor Based on Indirect Torsion Slot

High-Sensitivity LPFG Torsion Sensor Based on Indirect Torsion Slot

A highly sensitive torsion sensor based on upright-inverted alternating triangular prism structure on the single-multi-single mode fiber

In this paper, a novel torsion sensor based on Mach-zehnder interferometer (MZI) is proposed and demonstrated. The proposed sensor is fabricated by the single-mode fiber (SMF) and multi-mode fiber (MMF) shear splicing, further employing CO2 laser to modulate the MMF surface into triangular prism form. And compare the number of different triangular prism pairs structure on torsion sensitivity. By increasing the number of triangular prism pairs effectively improve the torsion sensitivity. The experimental results show that in the range of 0–9.617 rad/m, the highest sensitivity fiber sensor can be obtained with a sensitivity of 3.3133 nm/(rad/m). Meanwhile, the temperature characteristic of the sensor is investigated, which presents a sensitivity of 21.67 pm/℃ in the range from 30 ℃ to 100 ℃. Therefore, the temperature crosstalk is 0.0065 (rad/m)/℃, which results in a low temperature crosstalk. In addition, the structure also has the advantages of low cost and simple manufacturing process.

High sensitivity torsion sensing MZI based on exciting the separation mode of graded index fiber

Fiber interferometric sensor can be used to measure torsion, and Mach–Zehnder interferometer (MZI) structured torsion sensor is convenient for practical applications, but the measurement sensitivity is low and needs to be improved. The off-axis light transmitted in the graded index fiber is highly susceptible to torsional modulation, which leads to a significantly higher response compared to the fundamental mode transmitted along the axis. As a result, the off-axis light is referred to as the “separation mode” because its transmission trajectory is separated from the fundamental mode. In this paper, we constructed a torsion sensing MZI using a graded index fiber, excited the separation mode to interfere with the fundamental mode to improve sensing sensitivity, designed four steps of sensitization in sequence, and proved the feasibility of the scheme through experimental. After four steps of sensitization, the sensitivity of the sensor gradually improves, with the highest torsion sensitivity of 4 nm/(rad/m) and −4.1 nm/(rad/m) in positive and negative directions, respectively. The linearity is good within the measurement range of −2.5 rad/m to 2.5 rad/m. The proposed torsion MZI sensitization scheme is novel, and with a high sensitivity torsion MZI, which will play an important role in the field of intelligent monitoring and control.

Highly sensitive torsion sensor based on helical eccentric dual-core fiber Michelson interferometer

An optical fiber torsion sensor was academically put forward and experimentally demonstrated by applying a Michelson interferometer (MI) based on a helical eccentric dual core fiber (HEDCF). The sensor consists of an eccentric dual core fiber (EDCF), a taper, and a helical structure based on the EDCF. Since there is a large interval between a centric core and an eccentric core of the EDCF, the helical structure can greatly improve the torsion sensitivity of the sensor. When the twisting direction is consistent with the pre-twisting direction, the optical path difference (OPD) of MI negative increases during the twisting process, and the spectral resonance wavelength shifts blue. Experimental results show that the greater the degree of helical addition, the higher the torsional sensitivity. The torsion sensitivity can reach as high as −7.01 nm/(rad/m) in clockwise (CW) direction in the range of 0–9.595 rad/m. Moreover, the satisfactory sensitivity, stable structure and small temperature crosstalk, let it a valuable select in torsion sensing domain, and is promising to be useful for broad applications across engineering fields.