An intelligent grasper to provide real-time force feedback to shorten the learning curve in laparoscopic training.

BACKGROUND: A lack of force feedback in laparoscopic surgery often leads to a steep learning curve to the novices and traditional training system equipped with force feedback need a high educational cost. This study aimed to use a laparoscopic grasper providing force feedback in laparoscopic training which can assist in controlling of gripping forces and improve the learning processing of the novices. METHODS: Firstly, we conducted a pre-experiment to verify the role of force feedback in gripping operations and establish the safe gripping force threshold for the tasks. Following this, we proceeded with a four-week training program. Unlike the novices without feedback (Group A2), the novices receiving feedback (Group B2) underwent training that included force feedback. Finally, we completed a follow-up period without providing force feedback to assess the training effect under different conditions. Real-time force parameters were recorded and compared. RESULTS: In the pre-experiment, we set the gripping force threshold for the tasks based on the experienced surgeons' performance. This is reasonable as the experienced surgeons have obtained adequate skill of handling grasper. The thresholds for task 1, 2, and 3 were set as 0.731 N, 1.203 N and 0.938 N, respectively. With force feedback, the gripping force applied by the novices with feedback (Group B1) was lower than that of the novices without feedback (Group A1) (p < 0.005). During the training period, the Group B2 takes 6 trails to achieve gripping force of 0.635 N, which is lower than the threshold line, whereas the Group A2 needs 11 trails, meaning that the learning curve of Group B2 was significantly shorter than that of Group A2. Additionally, during the follow-up period, there was no significant decline in force learning, and Group B2 demonstrated better control of gripping operations. The training with force feedback received positive evaluations. CONCLUSION: Our study shows that using a grasper providing force feedback in laparoscopic training can help to control the gripping force and shorten the learning curve. It is anticipated that the laparoscopic grasper equipped with FBG sensor is promising to provide force feedback during laparoscopic training, which ultimately shows great potential in laparoscopic surgery.

Convolutional-neural-network-based versus vision-transformer-based SNR estimation for visible light communication networks.

Visible light communication (VLC) has emerged as a promising technology for future sixth-generation (6 G) communications. Estimating and predicting the impairments, such as turbulence and free space signal scattering, can help to construct flexible and adaptive VLC networks. However, the monitoring of impairments of VLC is still in its infancy. In this Letter, we experimentally demonstrate a deep-neural-network-based signal-to-noise ratio (SNR) estimation scheme for VLC networks. A vision transformer (ViT) is first utilized and compared with the conventional scheme based on a convolutional neural network (CNN). Experimental results show that the ViT-based scheme exhibits robust performance in SNR estimation for VLC networks compared to the CNN-based scheme. Specifically, the ViT-based scheme can achieve accuracies of 76%, 63.33%, 45.33%, and 37.67% for 2-quadrature amplitude modulation (2QAM), 4QAM, 8QAM, and 16QAM, respectively, against 65%, 57.67%, 41.67%, and 34.33% for the CNN-based scheme. Additionally, data augmentation has been employed for achieving enhanced SNR estimation accuracies of 95%, 79.67%, 58.33%, and 50.33% for 2QAM, 4QAM, 8QAM, and 16QAM, respectively. The effect of the SNR step size of a contour stellar image dataset on the SNR estimation accuracy is also studied.

Simultaneous measurement of axial strain and lateral stress based on cascaded interference structure.

To solve the cross-sensitivity problem in the dual-parameter optical fiber system, a new type of sensor based on cascaded interference structure is proposed without cross-sensitivity. The design consists of a Michelson interferometer and a Sagnac interferometer based on a high-birefringence suspended core fiber segment. After calculating by the analogous Fast Fourier Transformation (FFT) and filtering by FFT filter, the spectrum of the sensor responds linearly to the change of axial strain and lateral stress. The sensitivity to lateral stress is 3.13 nm/(kPa) in the range from 0 to 1200 Pa and the axial strain is 1.846e-4 (nm·µÉ›)-1 from 0 to 4000 µÉ›. The capability of the proposed sensor for dual-parameter sensing is also experimentally demonstrated. The precision rate for dual-parameter sensing is as high as 66.7%, reflecting the sensor's usability for simultaneous measurement of axial strain and lateral stress.

Ultrasensitive cascaded in-line Fabry-Perot refractometers based on a C-shaped fiber and the Vernier effect.

We propose and experimentally demonstrate a fiber refractometer based on a C-shaped fiber and the Vernier effect. The sensor is fabricated by cascading a single mode fiber (SMF) pigtail together with a C-shaped fiber segment and another SMF segment. Thus, the C-shaped fiber would constitute an open cavity (sensing cavity) in which test analytes could be filled, while the SMF segment would constitute another reference cavity. Due to the similar optical path length of these two cavities, the Vernier effect would be activated, thus forming spectral envelops in the reflection spectrum of the sensor. Variations in the refractive index (RI) of analytes would result in the shifts of the spectral envelops. Both theoretical calculations and experiments are carried out in the characterization of the sensor measuring liquid and gaseous analytes. The experimental sensitivity of the sensor is found to be ∼37238 nm/RIU for gas RI measurement. The proposed sensor features the advantages such as ease of fabrication, extremely high sensitivity, capability of sensing of both gaseous and liquid analytes, small footprint, and good mechanical strength. Compared to other existing Vernier effect-based fiber refractometers typically fabricated using PCFs, the proposed sensor would allow analytes to have much easier and quicker access to the sensor probe.

Simultaneous Measurement of Temperature and Pressure Based on Fabry-Perot Interferometry for Marine Monitoring.

The temperature and pressure of seawater are of great importance to investigate the environmental evolution for the research of ocean science. With this regard, we proposed and experimentally demonstrated a seawater temperature and pressure sensor realized by a polyimide (PI) tube-based Fabry-Perot interferometer (FPI) together with a fiber Bragg grating (FBG). Benefiting from the higher thermo-optical coefficient and larger elasticity of polymer than the fused silica fiber, the sensitivity of the sensor is largely improved. The FBG is used to compensate the cross effect of the temperature. The measured temperature and pressure sensitivities of the sensor are 18.910 nm/°C and -35.605 nm/MPa, respectively. Furthermore, the temperature and pressure information measured by the sensor can be achieved simultaneously using the sensitivity matrix method. In addition, the proposed sensor has advantages of easy fabrication, compact size, as well as capability of multiplexing and long-distance measurement, making it competitive and promising during the marine monitoring.

Simultaneous measurement of salinity and temperature using a Sagnac interferometer based on concatenated polarization-maintaining fiber tapers.

A Sagnac loop interferometer based on concatenated polarization-maintaining fiber (PMF) tapers is proposed for simultaneous measurement of seawater salinity and temperature. The influences of the distance between the PMF tapers as well as fiber taper diameter on sensor performance have been investigated. Experimental results indicate that the fabricated sensor with a distance of 3 cm between adjacent fiber tapers possesses the salinity and temperature sensitivities of 0.367 nm/% and -0.728nm/∘C, respectively, and the taper waist diameter of 20 µm would help to improve salinity sensitivity in comparison with a sensor of 30 µm in diameter. The proposed Sagnac loop interferometer based on concatenated PMF tapers is expected to find potential applications in the measurement of seawater salinity.

High-Speed Handling Robot with Bionic End-Effector for Large Glass Substrate in Clean Environment.

The development of "large display, high performance and low cost" in the FPD industry demands glass substrates to be "larger and thinner". Therefore, the requirements of handling robots are developing in the direction of large scale, high speed, and high precision. This paper presents a novel construction of a glass substrate handling robot, which has a 2.5 m/s travelling speed. It innovatively adopts bionic end-suction technology to grasp the glass substrate more firmly. The structure design is divided into the following three parts: a travel track, a robot body, and an end-effector. The manipulator can be smoothly and rapidly extended by adjusting the transmission ratio of the reducer to 1:2:1, using only one motor to drive two sections of the arm. This robot can transfer two pieces of glass substrate at one time, and improves the working efficiency. The kinematic and dynamic models of the robot are built based on the DH coordinate. Through the positioning accuracy experiment and vibration experiment of the end-effector, it is found that the robot has high precision during handling. The robots developed in this study can be used in large-scale glass substrate handling.

Two semicircular-hole fiber in a Sagnac loop for simultaneous discrimination of torsion, strain and temperature.

We report a highly sensitive twist sensor based on a Sagnac interferometer constructed with a new type of optical fiber which contains an elliptical core and two large semicircular-holes, where the slow axis of the core orthogonal to the air-holes has a large sensitivity towards twist-induced birefringent changes. The novel fiber structure results in a highest twist sensitivity of 5.01 nm/° at a chosen dip over the range from 370°-400°. The resonance dips in the interference pattern respond with different rates in the wavelength shifts in the presence of physical parameters permitting to experimentally distinguish directional torsion, axial strain and temperature.

Sensitive Mach-Zehnder interferometric sensor based on a grapefruit microstructured fiber by lateral offset splicing.

A novel inline Mach-Zehnder interferometric (MZI) sensor based on a homemade grapefruit microstructured fiber (GMF) was proposed and experimentally demonstrated. The sensing unit consists of a short segment of a GMF sandwiched between two single mode fibers using lateral offset splicing. The fabrication of the GMF and the GMF-based MZI sensor was introduced. Mode analysis of the GMF and theoretical simulation of the proposed MZI sensor were investigated and matched well with experimental results. The sensing performance of the MZI sensor for temperature and strain was tested. The strain and temperature sensitivity are 1.97pm/µÉ› and 37pm/°C, respectively. The compact size, low cost and high sensitivity makes the MZI sensor a good candidate for sensing application.

Resurgent regenerated fiber Bragg gratings and thermal annealing techniques for ultra-high temperature sensing beyond 1400°C.

We report for the first time the resurgence of regenerated fiber Bragg gratings (RFBGs) useful for ultra-high temperature measurements exceeding 1400 °C. A detailed study of the dynamics associated with grating regeneration in six-hole microstructured optical fibers (SHMOFs) and single mode fibers (SMFs) was conducted. Rapid heating and rapid cooling techniques appeared to have a significant impact on the thermal sustainability of the RFBGs in both types of optical fibers reaching temperature regimes exceeding 1400 °C. The presence of air holes sheds new light in understanding the thermal response of RFBGs and the stresses associated with them, which governs the variation in the Bragg wavelength.

All-optical fiber filter based on an FBG inscribed in a silica/silicone composite fiber.

An all-optical tunable filter based on a fiber Bragg grating (FBG) inscribed in a self-heated silica/silicone composite fiber is demonstrated. A thin silicone film is coated inside the suspended core fiber), which acts as the silicone cladding. A periodic refractive index modulation is inscribed in the silicone cladding by UV irradiation. Silicone is an organic material whose optical properties are different than silica, which leads to interesting applications. The high thermo-optic properties are studied and applied here. A 1550 nm pump laser is utilized to heat the silicone grating where a wavelength shift is observed for the gratings when subjected to different pump powers. Experimental results indicate a wavelength tuning coefficient of -0.128nm/mW with a response time of 0.5 s to obtain a wavelength shift of 1 nm under periodic pump light. The new design of this miniature all-optical filter is cost-effective and can potentially be adhered in optical fiber sensing and communication systems.

The impact of sedation on quality metrics of colonoscopy: a single-center experience of 48,838 procedures.

PURPOSE: Investigation of the role of sedation during colonoscopy is meaningful as the advantages of colonoscopy performing with sedation are still controversial. METHODS: Medical records of patients who underwent colonoscopy in our institution were retrospectively analyzed. The sedation rate, adenoma detection rate (ADR), polyp detection rate (PDR), cecal intubation rate (CIR), iatrogenic colonic perforation rate (ICP) were calculated. RESULTS: A total of 48,838 colonoscopies (24,498 in males) dated from July 2007 to February 2017 were analyzed. The median age was 50 years (range 16-85 years). An overall sedation rate was 80.38%. The PDR was 26.77%, and was not statistically different between colonoscopy with or without sedation (26.67% vs 27.22, p = 0.474). ADR was 12.9% regardless of applying sedation or not (13.0% vs 12.44%, p = 0.337). The CIR was 87.42% in all examinations with an adjusted CIR of 90.34%, and was higher when performed with sedation than without sedation (88.92% vs 80.64%, p < 0.0001). Five cases (0.01%) of ICP were reported, all of which occurred in patients under sedation. CONCLUSIONS: The use of sedation is associated with increased CIR, but ADR and PDR remain unchanged with or without sedation. However, perforation rate, albeit very low, is significantly higher in sedated patients.

Two-dimensional vector accelerometer based on Bragg gratings inscribed in a multi-core fiber.

We propose and demonstrate a novel orientation-sensitive two-dimensional accelerometer based on fiber Bragg gratings inscribed in a multi-core fiber. Through monitoring of the wavelength shifts of three of the seven cores, including the central core and two outer cores which are not aligned in a straight line, information on vibration orientation as well as acceleration can be obtained simultaneously. Performance of the proposed accelerometer in terms of frequency, acceleration and vibration orientation are experimentally investigated. The designed two-dimensional accelerometer is capable of obtaining all these three parameters simultaneously. A sensitivity which is strongly dependent on the orientation is achieved, with a best orientation accuracy of 0.127° over a range of 0-180°. Moreover, the resonance frequency and the sensitivity can be optimized through adjusting the length and weight of the free-fiber. The ease of fabrication as well as the versatility of the proposed sensor makes it potentially useful in dynamic monitoring for industrial applications.

Single-ring suspended fiber for Bragg grating based hydrostatic pressure sensing.

We present a novel optical fiber composed of a suspended core, a supporting ring and an outer ring. To establish a large holey region, a germanium-doped core is suspended by a silica ring and the entire structure is enclosed by another silica ring. By monitoring the Bragg wavelength shift of an FBG written in such a fiber with an air filling fraction of 65%, a hydrostatic pressure sensitivity of -43.6 pm/MPa was achieved experimentally. The high-pressure sensitivity is in good agreement with the numerically calculated value of ~40 pm/MPa. Due to the significant impact of the fiber core suspended in the large holey region inside the fiber, the pressure sensitivity improved by approximately eleven times compared to a Bragg grating inscribed in a standard single-mode fiber. To the best of our knowledge, it is the highest pressure sensitivity obtained for a FBG-based sensor experimentally, when compared to other FBG-based pressure sensors reported up to date. The large air hole region and the suspended core in the center of the fiber not only make the proposed fiber sensor a good candidate for pressure measurements, especially in the oil industry where space is at a premium, but also allow the detection of substances, by exploiting interaction of light with liquids or gases.

Novel accelerometer realized by a polarization-maintaining photonic crystal fiber for railway monitoring applications.

In this paper, we present a novel accelerometer based on the Sagnac interferometer configuration using a polarization-maintaining photonic crystal fiber (PM-PCF), which has a sensitivity of ~8 pm/G, and a resonant frequency exceeding 2.5 kHz. The proposed accelerometer is capable of functioning with a constant sensitivity in a large frequency range from 0 to 1 kHz which is much wider than many FBG-based accelerometers. Experimental results obtained from a field test in railway monitoring, demonstrate a broader frequency range for the proposed accelerometer compared to that of the FBG based accelerometer and is comparable to the conventional piezoelectric sensor. The abrupt change in the acceleration measured by the sensor aids in locating any defect or crack present on the railway track. To the best of our knowledge, this is the first demonstration of an accelerometer based on a fiber interferometer aimed for the railway industry. The proposed accelerometer operating at high accelerations (>40 G) and capable of functioning at a broad frequency range, shows significant potential in being used in applications which require detection of strong and fast vibrations, especially in structural health monitoring of trains and railway tracks in real time.

Ring-core fiber with negative curvature structure supporting orbital angular momentum modes.

Compared to glass walls with a positive curvature, those with a negative curvature have been proven to have stronger confinement of light. Therefore, we change the multi-layered air holes in a photonic crystal fiber into several negative curvature tubes. As a result, the confinement medium is shifted from a low-index cladding material into a special structure. The theoretical analysis shows that each vector eigenmode has a corresponding threshold value for the outer tube thickness. It means that we can confine the target modes and filter the unnecessary modes by shifting the outer tube thickness. After substantial investigation on this fiber, we obtain the appropriate values for each structural parameter and then fabricate this negative curvature ring-core fiber under the guidance of the simulation results. Firstly, we draw the central cane under vacuum condition, then stack the cane and six capillaries to form the preform, and finally draw the ring-core fiber by using vacuumization method. The fiber test experiment indicates that the fiber length should be at least 15 m∼20 m to form the donut facula, and the tested losses of OAM+1,1, OAM+2,1, OAM+3,1, and OAM+4,1 are 0.30 dB/m, 0.36 dB/m, 0.37 dB/m, and 0.42 dB/m, respectively.

Fabry-Perot cavity-based contact force sensor with high precision and a broad operational range.

A novel, compact, and robust contact force sensor based on a micro-length single-mode fiber (SMF) incorporated in a cleaved micro-air cavity (MAC) is proposed. The fabrication process involves splicing of the SMF with a hollow-core fiber (HCF) followed by cleaving of the MAC and insertion of a SMF into the MAC. The force sensing mechanism is based on the movement of the micro-SMF inside the cleaved MAC. The total length of the probe varies between 300 and 500 µm, making it bend proof. Due to the all-silica-based structure, the sensing capability of the probe is demonstrated for a low (0-1000 mN), as well as a high range of force (1-10 N) measurements. The optimized structure shows a maximum force sensitivity of 14.2 pm/mN with a negligible temperature dependence of 0.4 pm/°C. The performance of the sensor is verified using an FEM-based software. The proposed probe has a linear response, negligible hysteresis, and repeatability error, making it suitable for biomedical sensing and robotic applications.

Torsion sensor based on inter-core mode coupling in seven-core fiber.

We proposed a novel torsion sensor based on inter-core mode coupling in seven-core fiber (SCF). The torsion sensor is fabricated by tapering a commercially available SCF spliced with two single mode fibers. Waist diameter and length of the taper structure were experimentally optimized to achieve good transmission spectrum. Based on this structure, the torsion measurement was conducted, and the experimental results demonstrated that the transmission spectrum shows a red shift with the fiber twist. The torsion sensitivity increases with the twisting angle, which can achieve as high as 1.00 nm/°. The direction of wavelength shift was observed to be opposite when twisting the tapered SCF in clockwise and counter-clockwise direction, demonstrating its capability to discriminate the rotation orientation. Moreover, all the measurements were repeated in attempts to confirm its stable performance as well as high accuracy. Mode coupling dynamics and theory of optical anisotropy in twisted fiber are adopted to discuss the sensitivity performance, which agrees well with experimental results. The novel torsion sensor could provide a promising candidate for the applications requiring accurate rotation.

Robust in-fiber spatial interferometer using multicore fiber for vibration detection.

We report the demonstration of a novel in-fiber spatially integrated Michelson interferometer based on weakly coupled multicore fiber (MCF) for vibration sensing. The compact interferometer is constructed by using two separate cores of the MCF, where the fiber end is cleaved in order to generate strong Fresnel reflection, and independent light coupling between the cores of MCF and the single mode fibers (SMFs) is enabled by the fan-in coupler. Vibration gives rise to differential strain variation between cores which results in the modification of phase difference of the interferometer. A narrow linewidth laser is employed, in order to interrogate the phase change induced reflection power variation. Vibration event can be identified and the vibration frequency can be retrieved by processing the measured reflection power with fast Fourier transform (FFT). Broad vibration frequency response range up to 12 kHz (limited by the cut-off frequency of the voltage driver of the vibration source) has been achieved. Performance of the sensor has been shown to be independent of the selection of different core pairs, where the MCF is wound to a piezoelectric transducer (PZT). The proposed in-fiber integrated spatial interferometer does not require any special processing of the fiber (e.g., tapering, splicing, and so forth). The unique sensor structure provides some extraordinary merits, including ultra-compact size, high mechanical strength, high sensitivity and temperature insensitivity.

Highly sensitive miniature fluidic flowmeter based on an FBG heated by Co2+-doped fiber.

In this paper, we present a miniature fluidic flow sensor based on a short fiber Bragg grating inscribed in a single mode fiber and heated by Co2+-doped multimode fibers. The proposed flow sensor was employed to measure the flow rates of oil and water, showing good sensitivity of 0.339 nm/(m/s) and 0.578 nm/(m/s) for water and oil, flowing at v = 0.2 m/s. The sensitivity can be increased with higher laser power launched to the Co2+-doped multimode fibers. A small flow rate of 0.005 m/s and 0.002 m/s can be distinguished for a particular phase of water or oil, respectively, at a certain laser power (i.e. ~1.43W). The flow sensor can measure volume speed up to 30 L/min, which is limited by the test rig. The experimental results show that the sensor can discriminate slight variation of flow rates as small as 0.002m/s.