Showing papers on "Single-mode optical fiber published in 2022"
TL;DR: In this paper , a 3D achromatic diffractive metalens on the end face of a single-mode fiber was designed and nanoprinted to perform in-focus focusing across the entire near-infrared telecommunication wavelength band ranging from 1.25 to 1.65 µm.
Abstract: Abstract Dispersion engineering is essential to the performance of most modern optical systems including fiber-optic devices. Even though the chromatic dispersion of a meter-scale single-mode fiber used for endoscopic applications is negligible, optical lenses located on the fiber end face for optical focusing and imaging suffer from strong chromatic aberration. Here we present the design and nanoprinting of a 3D achromatic diffractive metalens on the end face of a single-mode fiber, capable of performing achromatic and polarization-insensitive focusing across the entire near-infrared telecommunication wavelength band ranging from 1.25 to 1.65 µm. This represents the whole single-mode domain of commercially used fibers. The unlocked height degree of freedom in a 3D nanopillar meta-atom largely increases the upper bound of the time-bandwidth product of an achromatic metalens up to 21.34, leading to a wide group delay modulation range spanning from −8 to 14 fs. Furthermore, we demonstrate the use of our compact and flexible achromatic metafiber for fiber-optic confocal imaging, capable of creating in-focus sharp images under broadband light illumination. These results may unleash the full potential of fiber meta-optics for widespread applications including hyperspectral endoscopic imaging, femtosecond laser-assisted treatment, deep tissue imaging, wavelength-multiplexing fiber-optic communications, fiber sensing, and fiber lasers.
35 citations
TL;DR: In this article, three novel refractive index (RI) sensors based on one, two, and three H-shaped cavities (HCs) and metal-insulator-metal (MIM) waveguides are proposed.
25 citations
TL;DR: In this article , a single-mode hollow-core nested anti-resonant nodeless fiber with 0.74 dB km−1 loss was used to deliver 1 kW of near-diffraction-limited continuous-wave laser light over a 1 km distance, with a total throughput efficiency of ~80%.
Abstract: High-power laser delivery with near-diffraction-limited beam quality is typically limited to tens of metres distances by nonlinearity-induced spectral broadening inside the glass core of delivery fibres. Anti-resonant hollow-core fibres offer not only orders-of-magnitude lower nonlinearity but also loss and modal purity comparable to conventional beam-delivery fibres. Using a single-mode hollow-core nested anti-resonant nodeless fibre with 0.74 dB km−1 loss, we demonstrate the delivery of 1 kW of near-diffraction-limited continuous-wave laser light over a 1 km distance, with a total throughput efficiency of ~80%. From simulations, a further improvement in transmitted power or length of more than one order of magnitude should be possible in such air-filled fibres, and considerably more if the core is evacuated. This paves the way to multi-kilometre, kilowatt-scale power delivery that is potentially useful not only for future manufacturing and subsurface drilling but also for new scientific possibilities in sensing, particle acceleration and gravitational wave detection. Microstructured optical fibre is shown to be able transmit high-power laser light over long distances with high throughput efficiency.
24 citations
01 Jan 2022
TL;DR: In this article , a single-mode eccentric-core D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor is proposed and comprehensively investigated based on Finite Element Method (FEM).
Abstract: A single-mode eccentric-core D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor is proposed and comprehensively investigated based on Finite Element Method (FEM). The critical properties of the sensor such as single mode regimes, beam spot size, and confinement losses are all tailored for more practical network-integrable PCF SPR sensor with high coupling efficiency using commonly used single-mode optical fibers. The sensor has analyte Refractive-Index (RI) detection range between 1.330 and 1.420 with maximum sensitivity of 21200 nm/Refractive-Index-Unit (RIU), maximum Figure-of-Merit (FOM) of 294 RIU−1, maximum resolution of 4.72 × 10-6 RIU for analyte refractive index change of 0.005 with the finest Full-Width at Half-Maximum (FWHM) of 29 nm, and a maximum confinement loss of 14 dB/cm. The sensor exhibits high linear response at low analyte RI regime between analyte index 1.330 and 1.370. The proposed sensor design can be fabricated using comparatively simpler stack-and-draw method which is based solely on standard circular glass capillaries and solid rods.
21 citations
TL;DR: In this paper, a single-mode eccentric-core D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor is proposed and comprehensively investigated based on Finite Element Method (FEM).
Abstract: A single-mode eccentric-core D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor is proposed and comprehensively investigated based on Finite Element Method (FEM). The critical properties of the sensor such as single mode regimes, beam spot size, and confinement losses are all tailored for more practical network-integrable PCF SPR sensor with high coupling efficiency using commonly used single-mode optical fibers. The sensor has analyte Refractive-Index (RI) detection range between 1.330 and 1.420 with maximum sensitivity of 21200 nm/Refractive-Index-Unit (RIU), maximum Figure-of-Merit (FOM) of 294 RIU−1, maximum resolution of 4.72 × 10-6 RIU for analyte refractive index change of 0.005 with the finest Full-Width at Half-Maximum (FWHM) of 29 nm, and a maximum confinement loss of 14 dB/cm. The sensor exhibits high linear response at low analyte RI regime between analyte index 1.330 and 1.370. The proposed sensor design can be fabricated using comparatively simpler stack-and-draw method which is based solely on standard circular glass capillaries and solid rods.
21 citations
TL;DR: In this article , the authors report on HCF interconnections with the lowest-ever insertion losses (0.10 dB for HCF to standard single-mode fiber and 0.13 dB for HCF to itself in the 1.5 µm waveband) and in a pluggable means.
Abstract: To go beyond the fundamental limits imposed by latency, nonlinearity, and laser damage threshold in silica glass fibers, the hollow-core fiber (HCF) technique has been intensively investigated for decades. Recent breakthroughs in ultralow-loss HCF clearly imply that long-haul applications of HCF in communications and lasers are going to appear. Nevertheless, up to now, the HCF technique as a whole is still hampered by the limited length of a single span and the lack of HCF-based functional devices. To resolve these two issues, it is of importance to develop ultralow-loss and plug-and-play HCF interconnections. In this work, we report on HCF interconnections with the lowest-ever insertion losses (0.10 dB for HCF to standard single-mode fiber (SMF) and 0.13 dB for HCF to itself in the 1.5 µm waveband) and in a pluggable means. Two fiber mode-field adapters, one based on a graded-index multi-mode fiber (GIF) and the other utilizing a thermally expanded core (TEC) SMF, have been tested and compared. An extra insertion loss arising from imperfect refractive index distribution in a commercial GIF is observed. Our HCF interconnections also realize a back-reflection of <-35 dB over a 100 nm bandwidth as well as other critical metrics in favor of practical applications. Our technique is viable for any type of HCF.
17 citations
TL;DR: In this paper, a dual-layer polymer microcap based on different refractive index (RI) films was used to segment a single Cu/TiO2 coated micro-cone on single mode fiber (SMF) end facet for producing a sensing spectrum with two separated SPR dips.
Abstract: It is a challenging and valuable work to realize the simultaneous sensing of two or more parameters at the end of optical fiber. In this paper, we implemented an ultra compact dual-channel surface plasmon resonance (SPR) sensor on fiber-optic end facet. A dual-layer polymer microcap based on different refractive index (RI) films was used to segment a single Cu/TiO2 coated micro-cone on single mode fiber (SMF) end facet for producing a sensing spectrum with two separated SPR dips. The SPR dip (channel-II) generated by Polydimethylsiloxane (PDMS) microcap can reach high sensitivity temperature measurement of 2.935 nm/°C in the range of 30–70 °C, and the SPR dip (channel-I) generated by polyvinyl alcohol (PVA) microcap can achieve high sensitivity humidity measurement of 1.08 nm/%RH in the range of 20%RH-70%RH. Finally, the simultaneous detection of humidity and temperature can be realized by the matrix established by channel-I and channel-II. This is a simple, effective and reproducible micro laboratory on optical fiber end facet for dual parameter sensing.
12 citations
TL;DR: In this paper , the structural performance analysis of a single/double/quadruple tapered optical fiber (TOF) structure based on singlemode fiber (SMF) and multi-mode fiber(MMF) is discussed.
Abstract: This paper primarily discusses the structural performance analysis of a single/double/quadruple tapered optical fiber (TOF) structure based on single-mode fiber (SMF) and multi-mode fiber (MMF). Furthermore, the TOF's performance, including its diameter distribution, transmitted intensity, and reproducibility, is also evaluated. According to the experimental results, it can be concluded that the quadruple TOF structure based on SMF has a higher density of evanescent waves (EWs) on the surface of the tapered area, which is essential for the fabrication of high-sensitivity optical fiber sensors. The structure proposed in this article is feasible, and it can be used for optical fiber sensing while offering significant practical and promising applications as well.
12 citations
TL;DR: In this paper , a spliceless all-fiber amplifier for high-power laser systems is presented, where all optical components are directly integrated in a single Yb$^{3+}$-doped 3C fiber.
Abstract: Specialty fibers such as chirally-coupled-core fibers show a high potential for further power scaling of single-frequency fiber amplifiers. For the first time, we demonstrate a spliceless all-fiber amplifier, where all optical components are directly integrated in a single Yb$^{3+}$-doped 3C-fiber. Such a spliceless laser design enables a compact and robust architecture using specialty fibers, while maintaining excellent beam properties. At an output power of 336 W operating at 1064 nm, a fundamental mode content of 90.4% at a polarization extinction ratio above 13 dB was measured without any impact of transverse mode instabilities or other parasitic effects. This work emphasizes the field of applications of 3C-fibers in high-power laser systems.
10 citations
TL;DR: In this paper , a single-mode fiber curvature sensor based on surface plasmon resonance (SPR) was designed and fabricated, and a 50 nm gold film was coated outside the cladding, and the evanescent field after bending contacts the gold film to cause SPR.
Abstract: A fiber surface plasmon resonance (SPR) sensor is widely used in high-sensitivity refractive index measurement, but there is less research on curvature measurement. In this paper, a single-mode fiber curvature sensor based on SPR is designed and fabricated. By employing bending, the transmitted light in the fiber core leaks into the cladding. A 50 nm gold film is coated outside the cladding, and the evanescent field of the cladding after bending contacts the gold film to cause SPR. When the curvature changes, the coupled cladding mode and intensity are different; that is, the SPR incident angle and evanescent field intensity are different, so as to realize the dual parameters of SPR resonance wavelength and depth of the resonance valley changing with curvature. By experiments, the influence of different cutoff wavelengths of single-mode fiber on the performance of the sensor is studied. The testing results indicate that with the decrease in cutoff wavelength of the single-mode fiber, the valley depth sensitivity of the sensor increases, and the half height width (FWHM) decreases. When the cutoff wavelength of the single-mode fiber is 630 nm, the valley depth sensitivity of the sensor is 0.0088a.u/m-1, the wavelength sensitivity is 0.26nm/m-1, and the average FWHM is only 21 nm. The proposed single-mode fiber curvature sensor based on SPR has a narrow FWHM and an opening threshold. It can also realize no opening threshold by introducing a coreless fiber, which provides a new solution, to the best of our knowledge, for the diversified detection of fiber SPR sensors.
9 citations
TL;DR: In this article , a novel infinity 3D printing technique is explored to fabricate continuous few-meter-long low-loss near-zero dispersion suspended-core polypropylene fibers for application in terahertz (THz) communications.
Abstract: In this work, a novel infinity 3D printing technique is explored to fabricate continuous few-meter-long low-loss near-zero dispersion suspended-core polypropylene fibers for application in terahertz (THz) communications. Particular attention is paid to process parameter optimization for 3D printing with low-loss polypropylene plastic. Three microstructured THz fibers were 3D printed using the standard and infinity 3D printers, and an in-depth theoretical and experimental comparison between the fibers was carried out. Transmission losses (by power) of 4.79 dB/m, 17.34 dB/m, and 11.13 dB/m are experimentally demonstrated for the three fibers operating at 128 GHz. Signal transmission with bit error rate (BER) far below the forward error correction limit (10-3) for the corresponding three fiber types of lengths of 2 m, 0.75 m, and 1.6 m are observed, and an error-free transmission is realized at the bit rates up to 5.2 Gbps. THz imaging of the fiber near-field is used to visualize modal distributions and study optimal fiber excitation conditions. The ability to shield the fundamental mode from the environment, mechanical robustness, and ease of handling of thus developed effectively single-mode high optical performance fibers make them excellent candidates for upcoming fiber-assisted THz communications. Additionally, novel fused deposition modeling (FDM)-based infinity printing technique allows continuous fabrication of unlimited in length fibers of complex transverse geometries using advanced thermoplastic composites, which, in our opinion, is poised to become a key fabrication technique for advanced terahertz fiber manufacturing.
TL;DR: In this paper , the authors discussed the application of singlemode fiber and multimode fiber to the fabrication of a sensor structure based on the hetero-core optical fiber structure and showed that the SMSMS structure generates more evanescent waves that penetrate deeper into the sensing probe, increasing its sensitivity.
Abstract: The paper discusses the application of single-mode fiber (SMF) and multimode fiber (MMF) to the fabrication of a sensor structure based on the hetero-core optical fiber structure. The proposed structures are SMF-MMF-SMF (SMS), MMF-SMF-MMF (MSM), and SMF-MMF-SMF-MMF-SMF (SMSMS). The transmitted intensity of the probe is used to estimate the strength of the evanescent field. The results indicate that the SMSMS structure generates more evanescent waves that penetrate deeper into the sensing probe, increasing its sensitivity. As a result, the SMSMS structure has enormous development potential in the field of sensing.
TL;DR: An all-fiber Mach-Zehnder interferometer (MZI) using ring core few-mode fiber (RC-FMF) for curvature sensing is proposed and experimentally demonstrated as discussed by the authors .
Abstract: An all-fiber Mach-Zehnder interferometer (MZI) using ring core few-mode fiber (RC-FMF) for curvature sensing is proposed and experimentally demonstrated. The MZI was fabricated by splicing a segment of RC-FMF between two pieces of single-mode fiber (SMF). With the benefit of a RC of the central axis of the RC-FMF, the sensor is more sensitive to curvature compared to other fiber sensors based on ordinary SMF or FMF. Curvature measurement can be achieved by monitoring the wavelength shift of interference dips. Experimental results have shown that the sensitivity of curvature sensing can reach up to -4.370nm/m-1, within the range of 1.199-1.549m-1. Also, the temperature sensing characteristics of the sensor are measured, and the maximum temperature sensitivity is 57.6 pm/°C, ranging from 25°C to 45°C. The proposed MZI sensor has excellent potential for curvature measurement of building structural health monitoring, bridge engineering, and more.
TL;DR: In this paper , the first spectral linewidth measurement at kHz resolution of high-power single-frequency fiber lasers using a heterodyne technique was reported, and it was shown that these lasers can operate at a few kHz spectral linwidth.
Abstract: There have been several demonstrations of single-frequency single-mode ytterbium-doped fiber lasers operating at a few hundred watts of power. A narrow spectral linewidth of these lasers is critical for many applications but has never been properly measured before at high powers. In this work, we report the first spectral linewidth measurement at kHz resolution of high-power single-frequency fiber lasers using a heterodyne technique and can confirm that these lasers can indeed operate at a few kHz spectral linewidth. Furthermore, we have improved the power from single-frequency single-mode all-solid photonic bandgap fiber lasers to 500 W using an improved photonic bandgap fiber.
TL;DR: In this paper , the authors performed extended numerical studies to maximize the overall photon coupling efficiency of fiber-coupled quantum dot single-photon sources emitting in the near-infrared and telecom regime.
Abstract: We perform extended numerical studies to maximize the overall photon coupling efficiency of fiber-coupled quantum dot single-photon sources emitting in the near-infrared and telecom regime. Using the finite element method, we optimize the photon extraction and fiber-coupling efficiency of quantum dot single-photon sources based on micromesas, microlenses, circular Bragg grating cavities and micropillars. The numerical simulations which consider the entire system consisting of the quantum dot source itself, the coupling lens, and the single-mode fiber yield overall photon coupling efficiencies of up to 83%. Our work provides objectified comparability of different fiber-coupled single-photon sources and proposes optimized geometries for the realization of practical and highly efficient quantum dot single-photon sources.
TL;DR: In this paper , an algorithm, instantaneous optical frequency resampling (IOFR), was proposed to eliminate the nonlinearity of the laser source and used to obtain calibrated reference and measurement signals that were used for temperature demodulation.
Abstract: Distributed temperature sensing up to 600°C at a fiber length of 100.75 m based on optical frequency domain reflectometry (OFDR) was demonstrated using a standard single-mode fiber (SMF) without any treatment. The spatial resolution was 2.5 mm. An algorithm, instantaneous optical frequency resampling (IOFR), to eliminate the nonlinearity of the laser source was proposed and used to obtain calibrated reference and measurement signals that were used for temperature demodulation. Moreover, the temperature response stability of the annealed SMF was better than that of un-annealed SMF, where the temperature sensitivity was 1.96 GHz/°C at 600°C.
TL;DR: In this article , the authors proposed a unique combination of a microlens and a pillar on the facet of a single-mode fiber to achieve high coupling efficiency with a test sample of a SiPh chip.
Abstract: Silicon photonics technology has attracted considerable attention these days. However, the low coupling efficiency due to the difference in spot size between silicon photonic (SiPh) chips and single-mode fibers (SMFs) remains a challenging issue. We have already proposed a unique combination of a microlens and a pillar on the facet of SMF. However, the pillar may have difficulty in keeping a single mode for a signal beam of 1. 55 μm wavelength due to air cladding. In this study, we clarified the length of the pillar that can support the single mode through simulations and experiments. By the optimum designing, the spot size as the same level as the SiPh chip was obtained. We could show that our coupling device provides high coupling efficiency with a test sample of SiPh chip, and this device also can be applied to multi-core fibers.
TL;DR: In this paper , Y-branched circular core single-mode/few-mode polymer optical waveguides are designed and fabricated using the Mosquito method, where a liquid core monomer is dispensed into another liquid cladding monomer while the needle scans along the path of the wiring patterns.
Abstract: In this paper, Y-branched circular core single-mode/few-mode polymer optical waveguides are designed and fabricated using the Mosquito method we have developed. They comprise a low loss multiplexing (MUX) device for mode division multiplexing. In the Mosquito method, since a liquid core monomer is dispensed into another liquid cladding monomer while the needle scans along the path of the wiring patterns, it was difficult to form in-plane core crossings and core branches. In this paper, to form single-mode/few-mode Y-branched cores, we apply a unicursal needle-scan path for the Y-branch structure with the Mosquito method. For MUX device applications, cores satisfying the single-mode condition are successfully formed on the two-port side while the one-port side has a few-mode core.
01 Mar 2022
TL;DR: In this article , a hybrid linearization algorithm combining the multi-constraint iteration and linear equalization is proposed for PAM-4 signal transmission over 100-km SSMF in IM/DD optical transmission system with one single-ended photodiode.
Abstract: We propose a hybrid linearization algorithm combining the multi-constraint iteration and linear equalization. We experimentally demonstrate a 112-Gb/s PAM-4 signal transmission over 100-km SSMF in IM/DD optical transmission system with one single-ended photodiode.
TL;DR: In this paper , a temperature sensor of singlemode-no-core singlemode (SNCS) fiber structure coated with polydimethylsiloxane (PDMS) is proposed and investigated.
TL;DR: In this article , a fiber Mach Zehnder (MZ) interferometer based on sawtooth structure was proposed, which not only has the ability of bending sensing and bending direction recognition, but also can be applied to multi parameter sensing.
Abstract: In this paper, a fiber Mach Zehnder (MZ) interferometer based on sawtooth structure was proposed. It not only has the ability of bending sensing and bending direction recognition, but also can be applied to multi parameter sensing. Here we established the fiber hetero core structure with single mode fiber-multimode fiber-single mode fiber (MSM), and then fabricated the sawtooth structure on the single mode fiber in the middle by CO 2 laser. Since part of the cladding on the single-mode fiber was removed, the fiber core was no longer at the neutral plane. When the sensor is bent in the 0° direction or 180° direction, the effective refractive index and optical path length of the core mode will increase or decrease, resulting in the increase or decrease of the optical path difference between the core mode and the cladding mode. And then the interference wavelength will show a red shift or blue shift, so as to realize the curvature sensing with bending direction recognition. Meanwhile, due to the local stress of the sawtooth structure in the bending, the sensitivity of the bending sensor is improved. The testing results indicate that the sensitivity of 0° bending and 180° bending are −15.16 nm/m −1 and 8.32 nm/m −1 with the curvature range of 0–1 m −1 . Moreover, the sawtooth structure sensor has excellent performance in strain, temperature and torsion sensing. The torsional sensitivity of the sensor reaches −0.30 nm/(rad/m) with torsional range of 0–13.96 rad/m, the temperature sensitivity reaches 58.90 pm/°C, and the strain sensitivity reaches −3.62 pm/μϵ. In strain sensing, there are some interference valleys insensitive to strain, which can realize the simultaneous measurement of other parameters and strain.
TL;DR: In this article , a flexible, endoscopic, and minimally invasive coherent anti-Raman Stokes scattering (CARS) measurement method for single-cell application, employing a tapered optical fiber probe.
Abstract: Abstract We proposed and demonstrated a flexible, endoscopic, and minimally invasive coherent anti-Raman Stokes scattering (CARS) measurement method for single-cell application, employing a tapered optical fiber probe. A few-mode fiber (FMF), whose generated four-wave mixing band is out of CARS signals, was selected to fabricate tapered optical fiber probes, deliver CARS excitation pulses, and collect CARS signals. The adiabatic tapered fiber probe with a diameter of 11.61 μm can focus CARS excitation lights without mismatch at the focal point. The measurements for proof-of-concept were made with methanol, ethanol, cyclohexane, and acetone injected into simulated cells. The experimental results show that the tapered optical fiber probe can detect carbon-hydrogen (C–H) bond-rich substances and their concentration. To our best knowledge, this optical fiber probe provides the minimum size among probes for detecting CARS signals. These results pave the way for minimally invasive live-cell detection in the future.
TL;DR: In this article , an in-fiber Mach-Zehnder interferometer is proposed for the discrimination of strain and temperature, which is based on two cascaded standard single mode fibers using three peanut tapers fabricated by simple splicing.
Abstract: Abstract An in-fiber Mach-Zehnder interferometer is proposed for the discrimination of strain and temperature. The sensor is based on two cascaded standard single mode fibers using three peanut tapers fabricated by simple splicing. The cascaded structure excites more frequency components, which induce four sets of interference dips in the transmission spectrum. One set of the spectrum dips have different sensitivities to temperature and strain from those of the other three. The sensor can discriminate strain and temperature by monitoring the wavelength shifts of two spectrum dips. Repeated experiments are taken both for strain and temperature increasing and decreasing scenarios. Experimental results show that Dip 1 has an average strain sensitivity of −0.911 pm/µε and an average temperature sensitivity of 49.98 pm/°C. The strain sensitivity for Dip 2 is negligible and its average temperature sensitivity is 60.52 pm/°C The strain and temperature resolutions are ±3.82 µε and ±0.33 °C.
TL;DR: In this article, a simple structure composed of an ordinary singlemode fiber (SMF) and a section of multimode fiber (MMF) with a fiberbragg grating was designed to realize the dual-parameter sensing of micro bending and temperature simultaneously.
TL;DR: In this article , a highly efficient fiber-interfacing photonic device that directly launches single photons from quantum dots into a standard FC/PCconnectorized singlemode fiber is demonstrated.
Abstract: Incorporating solid‐state quantum emitters into optical fiber networks enables the long‐distance transmission of quantum information and the remote connection of distributed quantum nodes. However, interfacing quantum emitters with fiber optics encounters several challenges, including low coupling efficiency and delicate configuration. In this study, a highly efficient fiber‐interfacing photonic device that directly launches single photons from quantum dots into a standard FC/PC‐connectorized single‐mode fiber is demonstrated. Optimally designed photonic structures based on hole gratings produce an ultra‐narrow directional beam that matches the small numerical aperture of a single‐mode fiber. A pick‐and‐place technique precisely integrates a single miniaturized device into the core of the fiber. This approach realizes a plug‐and‐play single‐photon device that does not require optical alignment and thus guarantees long‐term stability. The results represent a major step toward practical and reliable transmission of quantum light across a fiber network.
TL;DR: In this paper , the shape sensor's performance when using a superelastic substrate with a small diameter instead of a substrate with dominating bending stiffness is investigated, and a generalized model is also designed for characterizing this type of flexible FBG-based shape sensor.
Abstract: Minimally invasive surgical procedures have become the preferable option, as the recovery period and the risk of infections are significantly lower than traditional surgeries. However, the main challenge in using flexible tools for minimal surgical interventions is the lack of precise feedback on their shape and tip position inside the patient's body. Shape sensors based on fiber Bragg gratings (FBGs) can provide accurate shape information depending on their design. One of the most common configurations in FBG-based shape sensors is to attach three single-mode optical fibers with arrays of FBGs in a triangular fashion around a substrate. Usually, the selected substrates dominate the bending stiffness of the sensor probe, as they have a larger diameter and show less flexibility compared to the optical fibers. Although sensors with this configuration can accurately estimate the shape, they cannot be implemented in flexible endoscopes where large deflections are expected. This paper investigates the shape sensor's performance when using a superelastic substrate with a small diameter instead of a substrate with dominating bending stiffness. A generalized model is also designed for characterizing this type of flexible FBG-based shape sensor. Moreover, we evaluated the sensor in single and multi-bend deformations using two shape reconstruction methods.
27 May 2022
TL;DR: In this article , a fiber acoustic sensor based on a single-mode-multimode-single-mode (SMS) fiber structure was demonstrated. But, the performance of the fiber sensor system was limited to a wide range of vibration frequencies from 10 Hz to 400 kHz.
Abstract: In this paper, we demonstrated a fiber acoustic sensor based on a single-mode–multimode–single-mode (SMS) fiber structure. The SMS fiber structure consists of a multimode fiber (MMF) sandwiched between two single-mode fibers (SMFs). Whenever the MMF fiber experiences vibration disturbances, the fiber experiences tensile and compressive strains. By demodulating the vibration-induced intensity fluctuations, the vibrations signals can be quantified. Through employing several SMS sensors in parallel and connecting, and controlling by an optical switch, quasi-distributed sensing can be realized. The proposed sensor system is demonstrated in a laboratory environment and has the capability of detecting a wide range of vibration frequencies from 10 Hz to 400 kHz. In addition, the fiber sensor system is field-tested, where several SMS fiber sensors are mounted on 8.5” diameter steel pipe and excite acoustic emissions based on a magnetostrictive guided wave collar system. The proposed highly sensitive fiber sensor can be potentially used in practical applications of pipeline health condition monitoring.
TL;DR: In this article , a large-measurement-range fiber curvature sensor based on Michelson interferometer is proposed and investigated, which is fabricated by sandwiching a bitaper between a singlemode fiber (SMF) and a piece of multimode fiber (MMF).
TL;DR: In this paper , a waist-enlarged bitaper structure on the interference arm of a single mode-multimode-single mode (SMS) interferometer (MZI) was developed.
Abstract: A Mach–Zehnder fiber optic sensor with high refractive index response sensitivity was developed. By fabricating a waist-enlarged bitaper structure on the interference arm of a single mode–multimode–single mode (SMS) Mach–Zehnder interferometer (MZI), the spectral contrast and response sensitivity were improved. Subsequently, the response sensitivity was further improved by etching the interference arm. When a beam of light was introduced into the sensor, due to the structural mismatch between the multimode fiber and the normal transmission light, the difference between the low-order mode and the high-order mode was generated in the fiber core and the fiber cladding. In the process of transmission in the sensing arm, due to the different refractive indices of the core and cladding, the optical path difference of the high-order mode and the low-order mode was different, which eventually generated interference fringes. The experimentally measured response sensitivity of SMS MZI in the range of 1.351 RIU to 1.402 RIU is 57.623 nm/RIU; the response sensitivity of a single mode–multimode–bitaper–multimode–single mode (SMBMS) MZI is 61.607 nm/RIU; and the response sensitivity of the etched SMBMS (ESMBMS) MZI is 287.65 nm/RIU. The response sensitivity of the new ESMBMS MZI is three times higher than that of the original SMS MZI. The sensor has the characteristics of compact structure, high sensitivity, easy manufacture, and a wide range of refractive index measurements, and can be used in food processing, pharmaceutical manufacturing and other fields.