Bidirectional Fiber Research Articles

Single-frequency all-polarization-maintaining ytterbium-doped bidirectional fiber laser.

We reported an all-polarization-maintaining single-frequency ytterbium-doped bidirectional fiber laser for the first time, to the best of our knowledge. Single-frequency operation was achieved by a stable dynamic grating in the active fiber of a proper length owing to the bidirectional operation of the laser. The fiber laser possesses a linewidth of 7.43 kHz, a slope efficiency of 47.9%, and a great long-term stability.

Investigation of a tunable and switchable multi-wavelength bidirectional Brillouin-erbium fiber ring laser

A multi-wavelength bidirectional Brillouin-erbium fiber ring laser with switchable Brillouin frequency spacing (BFS) is proposed and experimentally demonstrated. In the presented Brillouin-erbium ring laser, including an optical amplifier and a highly nonlinear fiber, and without any optical isolator, due to Rayleigh scattering, stimulated Brillouin scattering, and cascaded four-wave mixing initiated successively by the Brillouin pump (BP) light, the odd- and even-order Stokes lines are generated and circulate in the opposite direction in the ring cavity. The BP light and Stokes-induced Rayleigh backscattering light also simultaneously circulate in the ring cavity. Only by adjusting BP power, the gain competition between Brillouin based Stokes and cavity modes’ oscillation can be controlled, the laser output can be conveniently switched between single BFS and odd- or even-order double BFS. In addition, under the certain BP power conditions, the proposed multi-wavelength Brillouin-erbium fiber laser also can realize switchable odd- or even-order Stokes generation and Stokes generation with single BFS, with an increasing wavelength number in turn, only by simply adjusting pump power of the erbium-doped fiber amplifier. Stability and wavelength tunability of the proposed multi-wavelength bidirectional Brillouin-erbium fiber ring laser are also investigated, respectively.

Effect of fiber orientation on tensile strength of thin composites

In the current study, bi-directional Carbon Fiber Fabric has been used to fabricate the polymeric composite. The polymer composites were manufactured using the Vacuum Assisted Resin Transfer Molding (VARTM) process. The mechanical properties of fiber reinforced composite parts are highly influenced by fiber orientation. The aim of this paper is to study the effect of fiber orientation ontensile strength. The mode of failure were observed of the tested samples. Effect of fiber orientation can be seen on mode of failure of the laminates.

Fabrication and characteristics of hybrid glass fiber/Prosopis Juliflora reinforced epoxy composite

A wide range of favorable properties like high strength to weight ratio, low cost and durability is leading to a wide range of applications for Polymer Composite such as aviation, automobile, defense and marine. Thefocus of this paper is to improve the strength of the Glass Fiber Reinforced Plastic with the help of Prosopis Juliflora (A plant known as Seemai Karuvelam in Tamil) reduced into powder form. The work done in the project is an attempt to fabricate a hybrid composite using bi-directional Glass Fiber sheet with the Prosopis Juliflora powder of different weight percentage 0% 3%, 6% and 9% impregnated along with the matrix in between the sheets by hand layup technique. The fabricated composites are cut according to ASTM standards in order to determine the mechanical properties such as tensile strength, compressive strength and Impact strength. The hybrid composite with 6% Prosopis Juliflora is found to have superior mechanical properties as compared to glass fiber reinforced composite. The hybrid composite with 6% Prosopis Juliflora is then subjected to hardness and chemical test and compared with Glass fiber reinforced composite.

The effect of unidirectional pre-load on tensile characteristics of E-glass fiber and epoxy composite

The aim of this paper is to study the effects of low intensity pre-load approach on the tensile properties of fiber glass with epoxy composite. The loads had been applied on the bi-directional (0°–90°) fiber mats at its ends within the period of preparing the composite, until these sheets reach solidification state at room temperature. The fiber volume fraction was 10% from that composite, three samples of pre-loads had manufactured with three intensity of pre-loads as (5, 8 and 10 N) respectively. A control sample had prepared to comparison with pre-loaded ones. The effect of pre-load appears as increasing in maximum strength, percentage elongation and rupture strength by percent ratios (38.5%), (45.57%) and (106.2%) respectively by comparing with control samples. All pervious properties have reached their maximum values at per-load value of (10 N).

Experimental investigation of mechanical properties of GLARE composite with different layup sequences

Fuel consumption in aircraft predominantly depends on its payload. Hence there is a need for improvement in materials that have less weight and exhibit better mechanical properties. Fibre Metal Laminate (FML) is a new and reliable material used currently in many of the aircraft’s structural parts. It is a combination of metal and polymer composite layers. The combination of metal and composite layers exhibits better mechanical strength than the individual constituents. GLARE (Glass Laminate Aluminum Reinforced Epoxy) is a type of FML used in aircraft structures predominantly for weight reduction and improved mechanical properties. The Present investigation describes the mechanical properties of the hybrid composite using aluminum alloy, bi-directional e-glass fibre and epoxy resin with different layup sequences. Tensile and flexural tests of GLARE composites were conducted to study the mechanical properties for different layup sequences. The tests were conducted using Hydraulic Universal Tester Machine as per standards. It was observed that a specimen of 3/4 layup sequence exhibited better tensile and flexural strength than a specimen of 5/4 layup sequence.

Investigation of effect of hybridization and layering patterns on mechanical properties of banana and kenaf fibers reinforced epoxy biocomposite

This paper presents the Experimental evaluation of Tensile Strength, Flexural Strength and Impact Strength of Raw Banana-Kenaf fibers reinforced Epoxy Biocomposite. Non-woven banana-kenaf laminated composites fabricated by hand lay-up process by arranging fibers in different layering sequences. In the hybridization of banana and kenaf fibers alternate layers (Banana-Kenaf-Banana-Kenaf) as well as cumulative layers (Banana-Banana-Kenaf-Kenaf) are maintained. Results show that unidirectional banana fiber composite has better mechanical properties than bidirectional banana fiber composite. Furthermore it is found that unidirectional banana fiber laminate has more tensile strength than unidirectional banana-kenaf hybrid laminate. Whereas Flexural and Impact strengths of unidirectional banana-kenaf hybrid composite is more than that of unidirectional banana fiber laminate. Less costly, biodegradable, eco-friendly, non-toxic, skin-harmless, reusable, recyclable are the advantages of natural fibers over synthetic fibers. Such composites are used in the fields of manufacturing, space flight, automotive manufacturing and packaging.

Performance Enhancement of SCM/WDM-RoF-XGPON System for Bidirectional Transmission With Square Root Module

The 10-Gigabit Passive Optical Network (GPON), also known as (XGPON), is a key technology for the next generation of optical fibre communication systems that can improve reliability data rate. However, the increment in the transmission distance and data rate will lead to increased dispersion. This paper proposes a model based on the Sub-Carrier Multiplexing/Wavelength Division Multiplexing-Radio over Fibre-10-Gigabit Passive Optical Network system (SCM/WDM-RoF-XGPON) for Radio Frequency (RF) using a conventional Optical Network Unit (ONU) with the Square Root Module (SRM) on the side of the receiver. It is connected to a central office Optical Line Terminal (OLT) via an access network for multi-channel optical fibre transfers with a distance of 80 km and at 10 Gbps data rate. The Optisystem 15 simulation software is used to evaluate the proposed system based on the Bit Error Rate (BER), Quality factor (Q-factor) and eye diagram. The proposed system of bidirectional fibre links uses 1270 nm and 1577 nm wavelengths for uplink and downlink transmissions, respectively. The performance is further enhanced by using SRM to compensate for the square law characteristics, making it suitable for broadband services. Due to the utilisation of SRM in the architecture, the reported results reveal a double enhancement in successful transition performance at an optical fibre length of 80 km distance. The BER displayed significant improvement (less than 1.00E-09) with SRM at 80 km; however, without SRM and at 50 km, the BER is less than 1.00E-09. Investigations have presented an enhancement in the Q-factor's effectiveness with the use of SRM, which helps to increase the XGPON length. When the length of the fibre is 80 km, the Q-factor is 6 with SRM, while it is 3.7 without SRM.

Enhancing fracture toughness of laminated composite by chopped-fiber reinforcement

Abstract Inter-laminar fracture toughness of glass fiber composites is improved by reinforcing slender fillers into the matrix system. The chopped glass fibers of 16 µm diameter and 600 mm average length are embedded into the epoxy system up to 4% volume fraction. The wet layup technique is employed to fabricate laminates by stacking 16 layers of 450 GSM bidirectional fiber cloth. Double cantilever beam specimens are prepared and ASTM D5528-13 standards are followed to conduct Mode-I fracture tests. While reinforcements show no influence on the crack initiation toughness (GIi) of the laminates, both steady state and maximum energy release rates (GIc and GImax, respectively) are observed to increase with increasing filler volume fraction. The enhancement in fracture characteristics is attributed to the fiber bridging and fiber pullout, occur during crack propagation. Unlike neat epoxy and 2% reinforcement cases, in which the steady-state crack propagation regime is distinct, rapidly falling GI value upon reaching the peak load indicates a catastrophic failure in 4% filler reinforced laminate.

All-fiber single-cavity dual-comb for coherent anti-Stokes Raman scattering spectroscopy based on spectral focusing

We report an all-fiber free-running bidirectional dual-comb laser system for coherent anti-Stokes Raman scattering spectroscopy based on spectral focusing. The mode-locked oscillator is a bidirectional ring-cavity erbium fiber laser running at a repetition rate of ∼114MHz. One output of the bidirectional laser is wavelength-shifted from 1560 to 1060 nm via supercontinuum generation for use as the pump source. We have been able to record the Raman spectra of various samples such as polystyrene, olive oil, polymethyl methacrylate (PMMA), and polyethylene in the C-H stretching window. We believe that this all-fiber laser design has promising potential for coherent Raman spectroscopy and also label-free imaging for a variety of practical applications.

Numerical investigation of VARTM process using finite volume method

VARTM (Vacuum Assisted Resin Transfer Molding) is considered as a superior and simple method with respect to the manufacturing of sound composite parts due to the low setting up cost and consistency of the product obtained. The primary objective of the work is to propose an efficient method of numerical modeling to simulate the VARTM process and to validate with the experimental results. In numerical modeling, a control volume of specified dimensions that take the place of mold cavity in the experimental setup is defined, and the bi-directional E-glass fiber preform is assumed to be a porous structure. The experimentally obtained permeability value for different compaction pressures considered is given as an input to the numerical analysis and the completion time of the process is forecasted. For 1-Dimensional flow development, the proposed VARTM numerical simulation can be applied to mold cavities of complex geometries and the process completion time can thus be assured before the gelation time of the mixture.

Improvement of solid particle erosion resistance of helicopter rotor blade with hybrid composite shield

In the present study, the solid particle erosion behavior of polyurethane (PU) tape (3M-8663) material, bidirectional carbon fiber reinforced epoxy (CF/EP) and glass fiber reinforced epoxy (GF/EP) composites has been characterized experimentally and numerically. In the experimental part, steady-state erosion rates of aforementioned materials have been evaluated at different impact angles (20°, 30°, 45°, 60°, and 90°) and different impact velocities (70, 110, 150, and 190 m/s), and compared with those of stainless steel (SS304) and pure nickel materials (Ni) which are commonly used for erosion shield of helicopter rotor blades. Tests were conducted at room temperature using silica (SiC) particles (average diameter of 175 µm) as an erodent. Erosion behaviors on the shield surface of the same materials were investigated numerically under different impact velocities (110, 150, 190, and 230 m/s) for a pitch angle of 0°. Numerical erosion simulations were realized with commercial ANSYS-Fluent software using the finite volume method, an erosion model, and a discrete phase method with the Eulerian-Lagrangian approach. The experimental results showed that the GF/EP and the CF/EP composites indicated the maximum erosion rate at the impact angles ranged from 60° to 90°, whereas the PU tape material exhibited the maximum erosion rate at the impact angle of 30°. The results also showed that the PU tape surface clearly provided much better erosion resistance than the GF/EP and CF/EP composite surfaces, and the hybrid erosion shield having the PU/SS304 surface significantly improved the erosion resistance of the helicopter rotor blade up to the impact velocity of 150 m/s. A good agreement was also observed between the experimental and the numerical results.

Investigation on factors influencing flatness of a bidirectional SOA-based multiwavelength fiber laser

We investigate the flatness of the output spectrum in two multiwavelength fiber lasers (MWFLs) using two different configurations, unidirectional and bidirectional semiconductor optical amplifiers (SOAs). The most significant finding is the large variance in flatness values between the configurations where the unidirectional SOA is at 6.54 dB and the bidirectional SOA is at 1.45 dB. This is due to the lower total power and incomplete counter propagation in the cavity. The best SOA-based MWFL using a bidirectional SOA can generate 215 spectral lines within 5 dB uniformity. The multiwavelength spectrum is flat with a broad range, about 20 nm, owing to the property of spectral reshaping by the bidirectional amplification process in the SOA as well as complete counter propagation. Apart from the bidirectional SOA, the intensity-dependent loss (IDL) mechanism also contributes to the multiwavelength spectrum flatness. The adjustment of the half-wave plate (HWP) in the polarization controller (PC) affects the wavelength range and optical signal-to-noise ratio (OSNR). The MWFL shows excellent power stability, with the highest power deviation being only 0.95 dB.

Performance of axially loaded reinforced concrete rectangular columns strengthened with GFRP strips

Abstract Sticking of glass fibre cloth around a column using epoxy resin is one of the solutions for column strengthening. This paper details a study on short reinforced concrete (RC) rectangular columns having rounded edges with axial load strengthened using bi-directional Glass Fiber Reinforced Polymer (GFRP) cloth glued with epoxy resin. The results obtained, indicate a notable increase in axial load capacity of RC rectangular column when wrapped with GFRP fabric around the column and stick with epoxy resin as glue. Wrapping completely around the column with strips is better than wrapping with single continuous fabric. Considering the width of strip, strips having more width are giving finer results than narrow width strips. When strips of two or more layers are wrapped, then staggering of strips is even better than sticking one strip merely on another. The axial load capacity is increased by the use of two layers of GFRP strips and sticking three layers of GFRP strips showed a decrease in the axial load capacity.

The Longitudinal and Transverse Tensile Properties of Unidirectional and Bidirectional Bamboo Fiber Reinforced Composites

Alkali treatment on bamboo fibers were reported to improve the interface strength with epoxy resin as formed to a composite. In order to reduce the process time of alkali treatment, bamboo fibers were treated in alkali with different concentrations under the room temperature. The alkali treatment process for the bamboo fibers, which results in a higher tensile strength, was used for the subsequent studies. Unidirectional and bidirectional BF preforms were constructed in our laboratory. The unidirectional (UD) and bidirectional (BD) BF/EP composites were fabricated using the bamboo fibers treated with the selected BF alkali treatment process. Tensile properties were measured in both the longitudinal and transverse directions for the UD and BD BF/EP composites with different fiber volume fractions. The UD BF/EP composite has good reinforcement effect in the fiber direction and the tensile strength is compatible to the reported results. However, the transverse strength of UD composites is weaker than the pure epoxy. For BD BF/EP composites, tensile strengths in both the longitudinal and transverse directions all show some improvement as compared to the pure epoxy.

Hydrothermally grown ZnO NSs on Bi-Directional woven carbon fiber and effect of synthesis parameters on morphology

ZnO nanostructures on woven carbon fiber have been developed by hydrothermal technique under varying conditions of the process parameters. The impact of process parameters such as pH and molar concentration of precursor solution, growth duration and growth temperature on morphology and dimensions of ZnO nanostructures has been analyzed by Field Emission Gun-Scanning Electron Microscope, Energy Dispersive Spectroscopy (EDS) and UV-VIS-NIR spectroscopy. Different ZnO nanostructures of nanopallets-like, nanoflowers-like and nanoflakes-like were achieved at pH > 7 but nanorods-like and nanowires-like morphology were achieved at low pH. In addition, the impact of the chemical reactions, seeding and the growth process on ZnO nanostructures on woven carbon fibers has been discussed in the present work.

Carbon nanotube mode-locked fiber lasers: recent progress and perspectives

Abstract Carbon nanotubes (CNTs) possess remarkable nonlinear optical properties; a particular application is to function as a mode locker used in ultrafast fiber lasers to produce ultrashort optical pulses. Various types of CNT saturable absorbers (SAs) and ultrafast fiber lasers have been demonstrated. In this review, typical fabrication process and development of CNT SAs are discussed and we highlight the recent investigation and progress of state-of-the-art ultrafast fiber lasers covering GHz, bidirectional ultrafast fiber lasers, vectorial mode fiber lasers, comb systems, and mode-locking dynamics. Our perspectives of ultrafast fiber lasers based on CNT SAs are given finally.

Experimental and numerical study of composite sandwich panels for lightweight structural design

Composite sandwich panels are commonly considered as lightweight materials for structural design in many applications including automotive, aerospace and defence systems. These panels must be developed and validated for its mechanical strength characteristics under different loading conditions before deploying them for the practical application. Hence, the present paper deals with the experimental and numerical studies on composite sandwich panels subjected to quasi-static edgewise and flatwise compression loads. The composite face sheet was developed using 2 × 2 bi-directional 200GSM twill carbon fibre with hot cure benzoxazine resin. Sandwich panels were made using the developed composite face sheets with aluminium honeycomb core. The developed composite face sheets were tested for tensile and flexural conditions and the sandwich panels for edgewise and flatwise compression loads. Three samples for each of these tests were conducted in Shimadzu UTM with 50 kN capacity machine. A consistent load-displacement profile and the failure pattern were observed for all the samples tested in each test category. It is noted from these tests that the composite face sheets exhibited an ultimate tensile strength of 444 MPa and a flexural strength of 842 MPa which is pretty to close to the epoxy based composites used in the aerospace applications; sandwich panels showed an edgewise compressive strength of 610 MPa and flatwise compressive strength of 3.5 MPa. Tensile test coupons initially had undergone certain delamination before failure and failed close to the specimen holding end. Flexural test specimens were shown delamination of only one layer at the loading face. However, the specimen was well intact together even after failure. Bending mode of failure was noted during edgewise compression test of the sandwich; severe delamination was seen in the tension side of the sandwich whereas a line-folding crack with failure was exhibited at the mid-plane of the specimen. In case of flatwise compression, no evident of damage was observed in the sandwich structure. The second part of the paper describes the numerical simulations of these test cases including tensile, flexural, edgewise compression and flatwise compression using an explicit finite element solver viz. LS-DYNA. Material type 22 and 26 was selected to define the material behaviour of composites and honeycomb respectively. The delamination was modelled using *CONTACT_AUTOMATIC_SURFACE_SURFACE_TIEBREAK card with option 9 that works under B-K linear fracture mechanics law to define the normal and shear failure of cracks. The numerical results were found to match well with experimental observations for the individual coupons as well as the sandwich samples. Therefore, it is concluded from this study that the developed LS-DYNA simulation methodology can be used as a tool for composite sandwich panels based lightweight structural design.

Pulse-onset dynamics in a bidirectional mode-locked fibre laser via instabilities

Real-time observation of the emergence of coherent structures from noise via instabilities is of particular interest across disciplines ranging from biology to astrophysics. In the context of photonics, ultrafast fibre lasers provide an ideal test-bed for experimental observation of dynamical instabilities and generation of coherent structures of ultrashort pulses. Here we present experimentally obtained switch-on dynamics of counter-propagating ultrashort pulses in a bidirectional mode-locked fibre laser with delayed pulse formation via Q-switched and modulation instabilities, pronounced central wavelength drift, with the multiple-pulse formation. We define a localisation parameter using the round-trip resolved autocorrelation function to quantify the extent of the pulse formation, indicating an energy interchange between coherent features and background radiation. Furthermore, we report the formation of synchronised and unsynchronised dispersion waves. Our results reveal the complexity of the establishment of coherent features and their interaction with background radiation, contributing further towards the understanding of nonlinear systems in general.

Production and characterization of bamboo and sisal fiber reinforced hybrid composite for interior automotive body application

Composite materials have high strength to weight ratio with low density and high stiffness to weight, high strength ratios, and high fatigue strength to weight ratio compared to traditional engineering materials making them find wide applications in structural constructions. When the lightweight composite materials which are made of lightweight natural fibres are used in automotive application, the fuel economy of the vehicle improves reducing the related harmful emissions. The aim of this research is to develop and characterize the performance of sisal and bamboo reinforced polyester hybrid composite (BSFRHC) with different fibre orientation of sisal and unidirectional (UD) bamboo fibre. Next, BSFRHC was fabricated with 20% total fibre volume fraction. Of this total fibre volume, the composite is fabricated in 3:1 bamboo to sisal fibre ratio using hand lay-up technique. Then tensile, compressive, impact and flexural tests were carried out. In general, it is concluded that as varying fiber orientation, the tensile strength varies. The higher tensile strength is observed with 0° fibre orientation of bamboo/sisal fiber reinforced hybrid composite. From compressive strength of the hybrid composite reinforced with bamboo/sisal fibre, it is observed that the 0°-fibre orientation composite is exhibiting higher compressive strength than 90° fibre orientation composite and bidirectional (0°/90°) fibre orientation composite. Unidirectional 90° fibre orientation was found to have a higher tensile and flexural strength whereas unidirectional 90° and bidirectional (0°/90°) fibre orientation nearly have the same value of tensile strength, whereas bidirectional (0°/90°) was found to be having higher flexural strength than unidirectional 90° fibre orientation. Impact analysis of vehicle internal door panel made of BSFRHC was done using ANSYS Software. Furthermore, it is found that the bamboo and sisal fibre reinforced hybrid composite in unidirectional 0° has the potential to be used for automotive interior part application.