Fiber Polishing Research Articles

Aspects of Influencing Factors in the Polishing of Plastic Optical Fibers

The interaction between the X-ray beam and the scintillating core of the optical fiber creates photons. The generated photons propagate through the fiber until the fiber end where they are captured by a solid state photon sensitive detector. This very sensitive detector converts generated photons into a low-level electronic signal that is amplified for later processing. For industrial, medical domains or for detection of contraband objects in custom control, flexible detectors can be built using 1 mm plastic scintillating optical fiber. The paper presents aspects related to the influencing factors of the optical fiber polishing process. Experiments related to the influencing factors of optical fiber polishing were performed. The results related to the influencing factors for cutting the optical fiber are presented. A proposal for plastic fiber cutting tool was given. The results related to factor of influence for polishing of plastic scintillating fiber were presented. In conclusion a possible technology for plastic scintillating fiber with 1 mm diameter is described.

Fiber optics-based surface enhanced Raman Spectroscopy sensors for rapid multiplex detection of foodborne pathogens in raw poultry

AbstractA new high-sensitivity, low-cost, Surface Enhanced Raman Spectroscopy (SERS) sensor allows for the rapid multiplex detection of foodborne pathogens in raw poultry. Self-assembled microspheres are used to pattern a hexagonal close-packed array of nanoantennas onto a side-polished multimode fiber core. Each microsphere focuses UV radiation to a photonic nanojet within a layer of photoresist on the fiber which allows the nanoantenna geometry to be controlled. Optimizing the geometry for the excitation layer generates electric field concentrations− referred to as a hotspot− within the analyte, thereby maximizing the Raman signal and improving the signal-to-noise ratio. The side polished configuration with a larger surface area has significantly better performance than the SERS sensor on the fiber tip. The use of additive manufacturing for the fiber polishing jigs as well as the sample testing compartment simplifies the sensor development and testing. Experimental results demonstrate a sensitivity range of 0.4–0.5 cells/ml achieved using raw chicken rinsates spiked with Salmonella typhimurium. Additionally, the sensor demonstrated its capability for multiplex and specific detection of Salmonella and E. coli O157:H7 with an optimal detection time of 10 min. The new sensor addresses a major global foodborne pathogen that poses significant public health concerns and can be readily adapted for the detection of other bacterial and viral pathogens such as E. coli O157:H7, Campylobacter, Listeria, and avian influenza and in other food products, e.g., dairy, beef, and produce, as well as clinical applications.

Vector magnetic field sensor based on coreless D-shaped fiber and magnetic fluid.

A vector magnetic field sensor based on a ferrofluid-encapsulated coreless D-shaped fiber is proposed and demonstrated. The core of the singlemode fiber (SMF) is completely removed by fiber polishing technology, and the remaining part transformed into a multimode interference (MMI) waveguide. The exposed side-polishing plane enable the evanescent field to interact with surrounding magnetic fluid (MF). Relying on the non-circularly symmetric geometry of the coreless D-shaped fiber and the MF refractive index modulation by the orientation and intensity of the applied magnetic field, vector magnetic field sensing is achieved. The magnetic field response characteristics of the coreless D-shaped fibers with different residual thicknesses (RTs) are investigated. The experimental results show that a reduced RT yields enhanced sensitivity, and the magnetic field intensity sensitivity reaches -0.231 nm/mT and -0.483 dB/mT at a RT of 42.7 µm. The developed coreless D-shaped fiber sensor exclusively utilizes SMF, thereby offering a cost-effective scheme for the fabrication of vector magnetic field sensors.

Plastic Fiber Low Light Measurement Method

Paper describe researches performed to develop a method for checking the light transmission through plastic scintillating fiber. Such fibers are used in different industrial or research application but for our purpose are main components of a flexible detector. Such detector use photon scintillating signals read by higly sensitive detectors and special measures taken to get such sensitivity. We present in paper a method and algorithm developed for measurement of light transmission through plastic fiber when signals are at level of nW. We develop a stand to implement and verify this method. We use fibers with connectors at each fiber end. Fibers are previously polished at each end in order to allows to pass the signal through surface with low losses. Using the stand we perform measurements to analyse the feasibility of method. We present the results that demonstrate the feasibility of method. We succeed to measure signals at level of nW using special measures. Our results shows that method and stand can be used to measure low level signals through fibers. Using this method, it is possible to check the quality of plastic fiber polishing. A fiber with end surface well-polished allows to pass the signal at such low level (nW).

Investigation on the Dependence of Directional Torsion Measurement on Multimode Fiber Geometry

The torsion measurement and torsion direction discrimination characteristics of a multimode fiber (MMF) geometry in a singlemode-multimode-singlemode (SMS) fiber structure are investigated theoretically and experimentally. Three different geometries of MMFs, including circular symmetric MMF, axisymmetric MMF, and asymmetric MMF were fabricated based on a fiber polishing technique. The torsion response characteristics of a MMF depends on the birefringence within the MMF, as birefringence is related to the twist rate of the fiber. The experimental results demonstrate that the unpolished MMF with a circular asymmetric refractive index (RI) distribution has no wavelength response to torsion, and the single-side polished MMF with an axisymmetric RI distribution can measure torsion, but it does not have the ability to discriminate torsion direction. It is found that an MMF section with two polished surfaces at an angle to each other results in a departure from the symmetrical RI distribution, which introduces elliptical birefringence into the MMF. As a result, directional torsion measurement is achieved with sensitivities of 0.162 nm/(rad/m) clockwise and -0.139 nm/(rad/m) counterclockwise. The MMF geometry presented provides a new approach to torsion direction discrimination and shows good application potential in practical torsion vector measurement.

High-temperature resistant, all-fiber miniature interferometer

Herein, a novel high-temperature resistant, miniature all-fiber interferometer is experimentally demonstrated. This interferometer can be formed by an angled fiber without any additional components, which is fabricated by a simple one-step fiber polishing, thus, this angled-fiber based miniature interferometer can serve as a direct sensing probe. The qualitative relationship between fiber interferometer’s visibility and fiber angle is calculated by using the coupled mode theory, and this interferometer is experimentally demonstrated, and then, the temperature response and high-temperature resistance of a 39° angled-fiber based interferometer is investigated. The experimental results show that the sensitivity of this 39° angled-fiber interferometer is 13.7 pm/°C in the range of 500–1000 °C. Besides, the high-temperature resistance reveals that this all-fiber interferometer excellent high-temperature survivability while the temperature is up to 1000 °C.

A Fiber Ring Laser Sensor with a Side Polished Evanescent Enhanced Fiber for Highly Sensitive Temperature Measurement.

We demonstrate a highly sensitive and practical fiber-based temperature sensor system. The sensor is constructed based on a fiber ring laser (FRL) as well as a side-polished fiber filled with isopropanol. The laser cavity of the sensing part fiber is polished by the wheel fiber polishing system with residual thickness (RT) is selected to detect the temperature in the FRL. Thanks to the high thermo-optic coefficient of isopropanol, the sensitivity of the proposed temperature sensor could be effectively improved by filling isopropanol in the cost-less side polished single mode fiber. Refractive index (RI) of isopropanol changes with the surrounding temperature variation allowing high-sensitivity temperature sensing. Experimental results demonstrate that the side polished fiber can efficiently excite high-order cladding modes which enhance the modular interference increase the interaction between the evanescent wave and the isopropanol. Besides, the results show that the sensitivity can be as high as 2 nm/°C in the temperature range of 25–35 °C.

Side-Polished DBR Fiber Laser with Enhanced Sensitivity for Axial Force and Refractive Index Measurement

A highly sensitive optical fiber sensor for the measurement of axial force and refractive index (RI) is presented. The optical sensor consists of a distributed Bragg reflector (DBR) based fiber laser, the laser cavity of the DBR is polished to D-shape by the wheel fiber polishing system. Birefringence has been introduced with side polishing of the fiber, and then, it is utilized for sensing applications. The working principle of the device is based on the principle of the change in beat frequency of the two orthogonal polarization modes of the DBR fiber laser with external perturbations. In this work, it has been shown that the dual polarization beat frequency can be used for RI-based measurement applications along with the measurement of the axial force. The sensitivity of the DBR fiber laser sensor with change in axial force is enhanced significantly with side polishing. Such a device is robust, simple in fabrication and most importantly low-cost interrogation techniques can be used for the detection purpose. A resolution of 5.6014 × 10–8 N has been achieved in case of recognition of axial force and 1.9259 × 10–5 RIU is the observable detection limit for the RI based measurement.

Design and numerical analysis of a novel dual-polarized refractive index sensor based on D-shaped photonic crystal fiber

This paper presents a novel dual-polarized refractive index sensor based on D-shaped photonic crystal fiber. Unlike the traditional D-shaped structures, we use a micro-opening of the deposited gold film as microfluidic channel to excite the surface plasmon resonance (SPR) mode. The fiber consists of two layers of circular pores arranged in an octagonal lattice structure. By optimizing the structural parameters of the fiber, the proposed sensor detection range: the refractive index of the analyte changes from 1.26 to 1.36. Numerical simulation based on the finite element method shows that the average sensitivities in the x- and y- polarization modes are 1182 nm RIU−1 and 5736 nm RIU−1, respectively. When the refractive index of the analyte to be measured is 1.36, the highest sensitivity of the x and y polarization directions is 1298 nm RIU−1 and 11 039 nm RIU−1, respectively. Among them, the resonance wavelength and the resonance intensity increase with the refractive index of the sample to be tested. In addition, we further analyzed the effects of microfluidic channel size, deposited gold film thickness, sensing region length and the overall structure of the fiber (polishing depth, inner cladding pore size, etc) on sensor transmission characteristics.

Single fiber dual-functionality optical tweezers based on graded-index multimode fiber

We propose and demonstrate single fiber dual-functionality optical tweezers based on a graded-index multimode fiber. By using the multi-angle fiber grinding and polishing technology, we fabricate the multimode fiber tip to be a special tapered shape, contributing to focus the outgoing beam with a large intensity gradient for the first functionality—three-dimensional contactless trapping of a microparticle. By adjusting the radial direction offset between the lead-in single mode fiber and the graded-index multimode fiber, we perform the second functionality—axial shift of the trapped microparticle with respect to the fiber tip without need of moving the fiber probe itself. It is convenient for practical applications. The theoretical and experimental results about the relationship between the radial offset and the equilibrium positions of the microparticle have the good consistency. Tailoring the trap and axial shift of the microparticle based on the graded-index multimode fiber provides convenient avenues for fiber optical tweezers applied in practical researches.

Dual-channel surface plasmon resonance refractive index sensor based on modified hetero-core structure fiber

We propose and demonstrate a novel dual-channel SPR refractive index sensor based on hetero-core structure fiber. For the traditional hetero-core structure fiber SPR sensor, the resonance wavelength range is unchangeable. We solve this issue by polishing the traditional hetero-core structure fiber as circular truncated cone shape. By this method, we can adjust the resonance wavelength range flexible by changing fiber polishing angle. With increasing of fiber polishing angle, the resonance wavelength range will red-shift. When fiber polishing angle is 14°, and refractive index range is from 1.333 to 1.385, the resonance wavelength range is from 754 nm to 965 nm, which is away from that of the traditional hetero-core structure fiber SPR sensor (600 nm to 700 nm). Therefore, we realize dual-channel sensing by wavelength division multiplexing technology. The sensitivity of two channels are 1980.77 nm/RIU and 4057.69 nm/RIU respectively. In addition, the resonance wavelength and sensitivity of the sensor have a well consistency no matter which working way we adopt. The proposed dual-channel SPR sensor has important applications for multiple analytes detection.

High-precision micro-displacement optical-fiber sensor based on surface plasmon resonance.

We propose and demonstrate a novel optical-fiber micro-displacement sensor based on surface plasmon resonance (SPR) by fabricating a Kretschmann configuration on graded-index multimode fiber (GIMMF). We employ a single-mode fiber to change the radial position of the incident beam as the displacement. In the GIMMF, the angle between the light beam and fiber axis, which is closely related to the resonance angle, is changed by the displacement; thus, the resonance wavelength of the fiber SPR shifts. This micro-displacement fiber sensor has a wide detection range of 0-25μm, a high sensitivity with maximum up to 10.32nm/μm, and a nanometer resolution with minimum to 2nm, which transcends almost all of other optical-fiber micro-displacement sensors. In addition, we also research that increasing the fiber polishing angle or medium refractive index can improve the sensitivity. This micro-displacement sensor will have a great significance in many industrial applications and provide a neoteric, rapid, and accurate optical measurement method in micro-displacement.

To Fabricate Bragg Grating on D-Shaped Optical Fibre by Micro-Pressing Method

In this paper, we proposed a method to fabricate a D-shaped optical fiber of Bragg surface grating filter component by D-shaped fiber polishing along with photolithography、holographic interference lithography technologies and micro-molding process. The optical fiber was side-polished until it reaches the core of fiber. The master Bragg grating was first fabricated on the positive photoresister by using the holography interference lithography, then the patterned resist was used as a mother mold to transfer the pattern onto a hard polydimethylsiloxane (hPDMS)/ polydimethylsiloxane (PDMS) mold. The gratings pattern on hPDMS/PDMS was then transferred onto the UV polymer on the surface of a D-shaped fiber using a UV replication process. The transmission spectra of the resulting gratings were measured, with test results showing the transmission dip of -17dB , and 3-dB-transmission bandwidth of 9nm.

Using Micro-Pressing Method to Fabricate Bragg Grating on D-Shaped Optical Fiber

In this paper, we proposed a method to fabricate a D-shaped optical fiber of Bragg surface grating filter component by D-shaped fiber polishing along with photolithography、holographic interference lithography technologies and micro-molding process. The optical fiber was side-polished until it reaches the core of fiber. The master Bragg grating was first fabricated on the positive photoresister by using the holography interference lithography, then the patterned resist was used as a mother mold to transfer the pattern onto a hard polydimethylsiloxane (hPDMS)/ polydimethylsiloxane (PDMS) mold. The gratings pattern on hPDMS/PDMS was then transferred onto the UV polymer on the surface of a D-shaped fiber using a UV replication process. The transmission spectra of the resulting gratings were measured, with test results showing the transmission dip of -17dB , and 3-dB-transmission bandwidth of 9nm.

Optical fiber polishing automation with on-line force sensing

This study proposes a bare fiber polishing control strategy and force sensing mechanism to improve the performance of fiber polishing in optical communication. By analyzing the force and problems encountered during polishing, this study successfully measured the force with the required precision. Finally, the experimental results demonstrate a yield improvement from 20% to 80%, for a fiber tip offset within 1.5 μm.

Influences of polishing on return loss of optical fiber connectors

With Al2O3 and SiO2 as polishing medium, under different polishing conditions, e.g. with different polishing pressure, polishing time and polishing fluid, the influences of polishing treatment on the return loss of optical fiber connectors were investigated. The return loss of optical fiber connectors is 32–38 dB before polishing. The results show that dry polishing (i.e. no polishing fluid) with Al2O3 has less influence on return loss of optical fiber connectors, while dry polishing with SiO2 reduces return loss to about 20 dB because of the end-face of optical fiber contaminated. The wet polishing(i.e. using distilled water as polishing fluid) with Al2O3 or SiO2 can increase return loss to 45–50 dB, but wet polishing with Al2O3 may produce optical fiber undercut depth of 80–140 nm. Wet polishing with SiO2 should be preferentially selected for optical fiber connectors and polishing time should be controlled within 20–30 s.

보현산천문대 고분산 에셀 분광기(BOES)의 광섬유 부분 제작과 설치

We present the detailed description on the fiber techniques adopted in the BOES: the design concepts and manufacturing of the v grooves, the procedures of the fiber polishing, adhering of the fibers to the v grooves, and the axis alignment of the fiber input and exit. The high efficiency and throughput of the BOES imply that the adopted fiber arts and the other optical components were well designed and properly treated. We learned that the relatively low efficiency of the 80 micron fiber comparing with the 200 and 300 micron fibers comes from the seeing and the guiding effects not from the poor fiber handling.

Effects of process parameter variations on the removal rate in chemical mechanical polishing of 4H-SiC

The effects of temperature, slurry pH, applied pressure, and polishing rotation rate on the material removal rate during chemical mechanical polishing (CMP) of 4H-silicon carbide wafers using colloidal silica slurry and polyurethane/polyester fiber polishing pads have been studied. Measured removal rates varied from around 100 A/hr to nearly 2500 A/hr depending on the values of the various parameters. The amount of material removed was determined by measuring the wafer mass before and after polishing. Variations in temperature and slurry pH did not produce significant changes in the measured removal rates. Higher polishing pressures resulted in increased material removal rates from 200 to 500 A/hr but also produced excessive polishing pad damage. Variations in pad rotational speeds produced the largest changes in material removal rates, from around 200 to around 2000 A/hr for rotational speeds between 60 and 180 rpm, but the variations were non-linear and somewhat inconsistent. This CMP formula is shown to consistently produce damage free surfaces but the optimum removal rate is slow.