Wedge-shaped Fiber Research Articles

Comparative study of lab-on-fiber vector magnetic field sensor based on multimode and few-mode fiber

A kind of reflective vector magnetic field sensor with wedge-shaped fiber tip based on surface plasmon resonance (SPR) and magnetic fluid (MF) has been fabricated and investigated. Multimode fiber (MMF) and few-mode fiber (FMF) were grinded and polished to get the wedge-shaped fiber tip, which was then plated with nanoscale gold film for exciting SPR. The as-fabricated tip was immersed in MF, which was used as the magnetic field sensitive material. Experimental results show that the magnetic field intensity and direction sensitivities of the magnetic field sensors based on MMF and FMF are 2317 pm/mT, 497 pm/° and 6776 pm/mT, 2313 pm/° respectively, which proves that the proposed sensor based on wedge-shaped fiber tip has great potential for realizing lab-on-fiber devices and applications.

Ultrahigh-performance vector magnetic field sensor with wedge-shaped fiber tip based on surface plasmon resonance and magnetic fluid

Abstract A novel fiber-optic vector magnetic field sensor and its sensing quality dependent of fabrication method has been proposed and investigated. The proposed sensor has two surfaces on the tip of a multimode fiber, which is used as the sensing probe. By plating different thickness of gold film on the surfaces, surface plasmon resonance (SPR) can be generated and the signal can be reflected by the surfaces as well. Meanwhile, magnetic fluid (MF) as the magnetic field sensitive material is packed around the sensing probe. The experimental results prove that the response of MF to external magnetic field can be used to sense magnetic field intensity and direction via monitoring the dip wavelength of SPR. The obtained refractive index (RI) sensitivities are 2105 nm/RIU (RI range: 1.332–1.365) and 6692 nm/RIU (RI range: 1.372–1.411), magnetic field intensity sensitivities are 11.67 nm/mT (0°), and −0.47 nm/mT (90°). Besides, the proposed sensing probe is ultracompact and the footprint is extremely small (the length of sensing part is only 615 μm), which is very helpful for magnetic field detection in narrow space and gradient field.

Dual-channel temperature-compensated vector magnetic field sensor based on lab-on-a-fiber-tip.

Fiber-optic magnetic field sensors based on magnetic fluid (MF) is encountering with thermal effects and demand for vectorization for several years. A common solution is to use axially processed fiber cascaded with fiber Bragg grating (FBG). However, the length of such sensors is usually in centimeter-level, which restricts the sensing applications in narrow space and gradient field cases. In this work, we present an ultracompact reflection-type dual-channel sensor for vector magnetic field (Channel 1, referred as CH1) and temperature (Channel 2, referred as CH2) monitoring, which is composed of a pair of gold-plated wedge-shaped multimode fiber (MMF) tip and gold-plated multimode-no-core fiber (MNF) tip. The surface plasmon resonance (SPR) effect was adopted. The two sensor probes are coated with magnetic-field-sensitive MF and temperature-sensitive polydimethylsiloxane (PDMS), respectively. The issue of vector magnetic field and temperature cross-sensitivity is tactfully resolved. Importantly, the proposed sensing probes are ultracompact and the spatial resolution is extremely small (615 µm for CH1 based on wedge-shaped fiber tip and 2 mm for CH2 based on MNF), which is very helpful for narrow space and gradient magnetic field detection. The obtained magnetic field intensity sensitivities are 1.10 nm/mT (90° direction) and -0.26 nm/mT (0° direction), and temperature sensitivity is -3.12 nm/°C.

Influence of Bubble Deformation on the Signal Characteristics Generated Using an Optical Fiber Gas-liquid Two-Phase Flow Sensor.

The use of optical fiber probe in two-phase flow measurements is very frequently encountered, especially in the applications of chemical engineering and petroleum industries. In this work, the influence of bubble piercing signals caused by bubble deformation is studied experimentally using a laboratory-prepared wedge-shaped fiber probe in a lab-scale gas–liquid flow generator. A three-dimensional simulation model is established to study the influence of bubble deformation on the piercing signals. A theoretical analysis of the characteristics of the pre-signal influenced by the bubble deformations is undertaken for a wide range of different modeled bubble shapes. Combining the experimental and simulation results, a promising analytical method to estimate the bubble shapes by analyzing the characteristics of pre-signals is proposed. The results of this investigation demonstrate that it is possible to estimate the bubble shapes before the fiber probe contacts the bubble surface. The method developed in this investigation is therefore highly promising for reducing errors caused by deformation during the probe piercing process.

Investigation of the characteristics of a fiber-optic gas-liquid two-phase flow sensor.

A laboratory-prepared wedge-shaped fiber probe using step-index multimode plastic optical fiber was described and tested in a lab-scale gas-liquid flow generator. A three-dimensional model was established in order to fully simulate the process of bubble piercing by the optical fiber probe. A theoretical analysis of the luminous intensity distribution of the light transmission in the process of bubble piercing was undertaken under conditions of different relative positions between the fiber probe and the bubble axis. Using this analytical method, it was possible to accurately define the range of the central region of the bubble where the presignal appeared.

Quasi-Axial GRIN Lens Implemented in Wedge-Shaped Fiber Coupling With InP-Based PLC

A 3-D equivalent rectangle approximation staircase concatenation method to analyze the optical mode evolution in a wedge-shaped fiber (WSF) is proposed in this paper. A scheme with an axial gradient-index (AGRIN) lens between the WSF and InP-based planar lightwave circuit (PLC) chip, yielding higher transmission efficiency than those with two cascaded lenses and one radial GRIN lenses, by 2.282 and 7.816 dB, respectively, is devised and experimentally demonstrated. The WSF-AGRIN-PLC-single-mode fiber coupling linkage supplies a preferable solution for solving the problem of index mismatching in fiber-to-InP-based PLC assembly to achieve a high-efficiency connection.

Single lens photometric machine vision with 3D imaging for fiber-to-chip coupling

A single lens photometric machine vision (SLPMV) optical microbench is presented and built for fiber-to-chip coupling. By a rotation mechanics in SLPMV, the multi-view-camera can scan the various surface status of the chips coupled. To realize 3D imaging more explicitly, the modified photometric stereo algorithm is proposed through acquiring the images of weak saturation, matching the scanning illuminative angles, and rectifying rectangularly the original images. The reconstructed images have had similar qualities as those obtained by scanning electron microscopy and have unveiled the detailed information obscured in the 2D images. For the InP-based optical waveguide chip coupled with wedge-shaped fiber, the insertion loss tested on the SLPMV is 3 dB less than one on the conventional testing station. The SLPMV could serve as a more cost-effective and compact scientific observation instrumentation in imaging informatics than commercial ones.

Equivalent rectangle approximation-staircase concatenation method for wedge shaped fiber

Wedge shaped fiber (WSF) is the key component to acquire high coupling efficiency between input/output ports of planar lightwave circuit chips and fiber arrays. It is very important to analyze the mode spot and the mode field evolution of the lightwave propagating in WSF using numerical simulation tools. A three_dimensional equivalent rectangle approximation-staircase concatenation method (ERA-SCM) is proposed to fractionize the wedged tip of WSF along the propagating direction and introduce rectangular waveguide approximation so that effective index of the segmentations is obtained and SCM analysis model is established. Lightwave propagation and mode field evolution is analyzed by ERA-SCM and compared with finite difference-beam propagation method (FD-BPM), showing that the former is more precise to solve mode field evolution for asymmetric fiber and waveguide structures. The measurement of the output optical spot verifies the ERA-SCM simulation error is within 1.9%, while that for FD-BPM method is 4.5%. Thus, ERA-SCM is an effective method for analyzing asymmetric fiber and waveguide structures.

Hybrid-effect transmission enhancement induced by oblique illumination in nano-ridge waveguide

In a nano-ridge waveguide under oblique illumination, we demonstrated transmission enhancement resulting from a hybrid effect between propagation modes and surface plasmon wave. The measured near-field intensity with 44-degree illumination was 1.6 times higher than that illuminated with normal incident light. Consequently, a wedge-shaped fiber probe was proposed to serve as a compact near-field light source.

Fabrication of a Wedge-shaped Fiber Endface by a Self-centering Technique

We describe a technique for the fabrication of a wedge on the fiber endface, intended for high efficiency laser-to-fiber coupling. An important feature of this technique is that it is self-centering with respect to the fiber core, so that the core/clad concentricity error is uninfluential. As an application, we report experimental data on pig-tailing of a 980-nm pump laser.

Efficient power coupling from a 980-nm, broad-area laser to a single-mode fiber using a wedge-shaped fiber endface

A theoretical and experimental study of an efficient technique for coupling a broad-area laser to a single-mode fiber without the use of bulk optical components was carried out. The technique uses a wedge-shaped fiber endface to approximate a cylindrical lens action to correct for the phase mismatch between the curved laser beam wavefront and the planar fiber beam. A theoretical formula for the coupling efficiency in the absence of both angular and transverse misalignments is derived. By optimizing the wedge angle and the axial separation between the laser facet and the fiber endface, a maximum coupling efficiency of 47%, compared to 20% for the square endface, achieved, resulting in 15.2 mW of power in the single-mode fiber. The fabrication process consists of a simple polishing procedure requiring a wedge-shaped polishing tool and is highly reproducible.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>