Poly Fiber Research Articles

Review on the performances, foaming and injection molding simulation of natural fiber composites

AbstractRecently, natural fiber becomes an alternative to the synthetic fiber for the composites used in aerospace, automotive, sports, packaging and so on, due to its inherent characteristics like biodegradablity, renewablity, high‐specific strength and specific modulus. However, there are still many challenges in the fabrication of the natural fiber composites, including the poor compatibility between the nonpolar matrix and the polar natural fiber, relatively high‐moisture absorption and low‐thermal resistance of natural fibers, etc. Moreover, when manufacturing this type composite, the processing conditions, fiber loading and inherent properties of fiber not only affect the mechanical properties, but also cause products defects, such as warpage, volume shrinkage and weld lines, which needs a rapid numerical design for the mold and manufacturing parameters. Therefore, the properties of natural fiber composites have been widely investigated to satisfy the increasing demand in different applications. This paper intends to review the mechanical properties, flammability, durability, foaming behaviors and numerical simulation of injection molding process of natural fiber composites.

Polarization Multiplexed Optical OFDM System With a Beat Interference Cancellation Receiver

A novel beat interference cancellation receiver (BICR) is proposed to cancel the signal-signal beat interference (SSBI) for polarization division multiplexed (PDM) optical orthogonal frequency division multiplexing (OOFDM) system, where two single sideband (SSB) OOFDM signals are polarization multiplexed along with their offset optical carriers (OCs) located at opposite sides. At receiver, the PDM SSB-OOFDM signal is equally power split into four beams with one or two OCs filtered out, and then fed into two balanced photodiode pairs for recovering the RF-OFDM signals with SSBI cancellation. The PDM SSB-OOFDM system is insensitive to fiber polarization mode dispersion since the proposed BICR is implemented without polarization-sensitive devices. Moreover, the spectral efficiency is greatly improved because of PDM and the small guard band since the SSBIs are eliminated. The proposed BICR scheme is validated with a simulation link of 112 Gbps 16-QAM PDM SSB-OOFDM signals. After 120km SSMF transmission, the EVM keeps below forward error correction limit of 16.3%.

Tunable Multi-Wavelength Bright-Dark and Dark-Bright Pulse Pairs Fiber Lasers

We have experimentally demonstrated tunable multi-wavelength bright-dark and dark-bright pulse pairs in an all normal dispersion Yb-doped fiber laser (YDFL) with a long cavity configuration. By carefully adjusting the pump power and the polarization state, bright-dark pulse pairs could be converted into dark-bright pulse pairs at the same wavelength. The comb filter provided by the tapered fiber facilitated the formation of the multi-wavelength pulses. And the wavelength-tunable for both bright-dark pulse pairs and dark-bright pulse pairs could be achieved by using a tapered fiber and rotatable polarization controller in the cavity to control the cavity losses. The tunable ranges were 14 nm and 4 nm with wavelength spacings of ~3.5 nm and ~3.7 nm for dual-wavelength pulse pairs and triple-wavelength pulse pairs, respectively.

Toward the Copolymerization of Propylene with Polar Comonomers.

Polyolefins are produced in vast amounts and are found in so many consumer products that the two most commonly produced forms, polyethylene (PE) and polypropylene (PP), fall into the rather sparse category of molecules that are likely to be known by people worldwide, regardless of their occupation. Although widespread, the further upgrading of their properties (mechanical, physical, aesthetic, etc.) through the formation of composites with other materials, such as polar polymers, fibers, or talc, is of huge interest to manufacturers. To improve the affinity of polyolefins toward these materials, the inclusion of polar functionalities into the polymer chain is essential. The incorporation of a functional group to trigger controlled polymer degradation is also an emerging area of interest. Currently practiced methods for the incorporation of polar functionalities, such as post-polymerization functionalization, are limited by the number of compatible polar monomers: for example, grafting maleic anhydride is currently the sole method for practical functionalization of PP. In contrast, the incorporation of fundamental polar comonomers into PE and PP chains via coordination insertion polymerization offers good control, making it a highly sought-after process. Early transition metal catalysts (which are commonly used for the production of PE and PP) display poor tolerance toward the functional groups within polar comonomers, limiting their use to less-practical derivatives. As late transition metal catalysts are less-oxophilic and thus more tolerant to polar functionalities, they are ideal candidates for these reactions. This Account focuses on the copolymerization of propylene with polar comonomers, which remains underdeveloped as compared to the corresponding reaction using ethylene. We begin with the challenges associated with the regio- and stereoselective insertion of propylene, which is a particular problem for late transition metal systems because of their propensity to undergo chain walking processes. To overcome this issue, we have investigated a range of metal/ligand combinations. We first discuss attempts with group 4 and 8 metal catalysts and their limitations as background, and then focus on the copolymerization of propylene with methyl acrylate (MA) using Pd/imidazolidine-quinolinolate (IzQO) and Pd/phosphine-sulfonate (PS) precatalysts. Each generated regioregular polymer, but while the system featuring an IzQO ligand did not display any stereocontrol, that using the chiral PS ligand did. A further difference was found in the insertion mode of MA: the Pd/IzQO system inserted in a 1,2 fashion, while in the Pd/PS system a 2,1 insertion was observed. We then move onto recent results from our lab using Pd/PS and Pd/bisphosphine monoxide (BPMO) precatalysts for the copolymerization of propylene with allyl comonomers. These P-stereogeneic precatalysts generated the highest isotacticity values reported to date using late transition metal catalysts. This section closes with our work using Earth-abundant nickel catalysts for the reaction, which would be especially desired for industrial applications: a Ni/phosphine phenolate (PO) precatalyst yielded regioregular polypropylene with the incorporation of some allyl monomers into the main polymer chain. The installation of a chiral menthyl substituent on the phosphine allowed for moderate stereoselectivity to be achieved, though the applicable polar monomers currently remain limited. The Account concludes with a discussion of the factors that affect the insertion mode of propylene and polar comonomers in copolymerization reactions, beginning with our recent computational study, and finishing with work from ourselves and others covering both comonomer and precatalyst steric and electronic profiles with reference to the observed regioselectivity.

Laser Written Glass Interposer for Fiber Coupling to Silicon Photonic Integrated Circuits

Recent advancements in photonic-electronic integration push towards denser multichannel fiber to silicon photonic chip coupling solutions. However, current packaging schemes based on suitably polished fiber arrays do not provide sufficient scalability. Alternatively, lithographically-patterned fused silica glass interposers have been proposed, allowing for the integration of fanout waveguides between a dense array of on-chip silicon waveguides and a cleaved fiber ribbon. In this paper, we propose the use of femtosecond laser inscription for the fabrication of the fused silica glass interposer, allowing for a monolithic integration of waveguides and V-grooves for fiber alignment. The waveguides obtained by Femtosecond Laser Direct Writing (FLDW) have a propagation loss of 0.88 dB/cm at 1550 nm. The mode-field diameter is 12.8 ± 0.4 μm, allowing for a coupling loss of 1.24 ± 0.32 dB when coupling to a standard single mode optical fiber, passively aligned to the fused silica waveguide by insertion in a V-groove created by Femtosecond Laser Irradiation followed by Chemical Etching (FLICE). The average surface roughness of the etched waveguide facet is 160 ± 5 nm. Scattering loss when coupling to fiber is reduced by use of an index-matching adhesive for fiber fixation. A polished out-of-plane coupling mirror at an angle of 41.5° injects the light into standard grating couplers, providing a quasi-planar fiber-to-chip package. The excess loss of the proposed solution is limited to 2 dB per interface, including mirror, waveguide and fiber coupling losses.

Stable dual-wavelength laser incorporating polarization-maintaining erbium-doped fiber

A stable dual-wavelength erbium-doped fiber laser is proposed and experimentally demonstrated. The mode competition in the gain medium was suppressed by enhancing the polarization hole burning mechanism through incorporation of polarization maintaining erbium-doped fiber and nonlinear polarization rotation. The fiber laser displayed high stability with lasing side-mode suppression ratios of 60.69 and 60.57 dB. Additionally, the negligible peak power fluctuation of 0.01 dB was achieved at 1557.17 and 1560.19 nm with both peak powers of 0.23 mW and 3-dB bandwidth of 0.028 and 0.025 nm, respectively. These findings provide insights for an enhanced seed laser source design for remote dual-wavelength fiber laser applications.

Efficient photonic crystal fiber polarization splitters composed of gallium arsenide and nematic liquid crystals

Two photonic crystal fiber (PCF) polarization beam splitters (PBSs) featuring ultra-short length and ultra-high extinction ratios at wavelengths of 1.31 [Formula: see text]m and 1.55 [Formula: see text]m are designed and investigated. Non-silicon materials, such as gallium arsenide (GaAs) and nematic liquid crystal (NLC), are incorporated into the structure to ensure operation of the splitters in the communication bandwidth. Based on the full-vector finite element method (FEM), numerical simulation is carried out to optimize the structural parameters systematically. Specifically, for the splitter operating at 1.31 [Formula: see text]m, the optimal optical fiber length, extinction ratio, and bandwidth are 27.87234 [Formula: see text]m, [Formula: see text] dB, and 152 nm, respectively. In comparison, the optimal fiber length, extinction ratio, and bandwidth of the splitter at the wavelength of 1.55 [Formula: see text]m are 15.59356 [Formula: see text]m, [Formula: see text] dB, and 200 nm, respectively. The results reveal that the splitters have great potential in environmental monitoring, biochemical detection, and optical communication.

Broadband silicon core photonics crystal fiber polarization filter based on surface plasmon resonance effect

In this article, a panda-like silicon core based photonics crystal fiber was proposed and applied onto a polarization filter. Au film coating surrounding the air holes acted as a plasmonic active metal. Using the Finite element method, the quality of the proposed fiber was investigated, including confinement loss and extinction ratio. By adjusting the length of the proposed fiber, the applicable operating wavelength region could reach up to 1μm easily. Thus when the length increased to 6 mm, the wavelength band covered fiber communication band was also obtained. As a result, the proposed silicon core photonics crystal fiber achieved a good filtering effect in the near-infrared, even extending to mid-infrared. Moreover, the proposed fiber device can easily integrate with the existing optical fiber communication and sensing system.

A modified dual-core THz fiber polarization splitter with four subwavelength tubes

We propose a terahertz polarization splitter based on suspended dual-core fiber. Each core of the fiber is formed with two adherent subwavelength polymer tubes, which is helpful for a high modal birefringence. Due to the difference of coupling length between x and y polarizations, the proposed splitter can completely separate two orthogonal polarization modes at a specific splitting length. A 1.184 cm long splitter can be obtained at a center frequency of 1 THz. Meanwhile, the low insertion loss of 0.6 dB, the bandwidth of 0.05 THz and the extinction ratio better than −10 dB can be supplied. Moreover, an efficient design rule for the proposed splitter is demonstrated aiming to high extinction ratio at any desired operation frequency. The proposed terahertz polarization splitter has some potential applications in all-optical networks in THz systems.

Electrospun fibers of poly (vinyl alcohol): zinc acetate (PVA:AcZn) and further ZnO production: evaluation of PVA:AcZn ratio and annealing temperature effects on ZnO structure

The effects of the poly (vinyl alcohol): zinc acetate (PVA:AcZn) mass ratio on the morphology and structure of the precursor electrospun fibers as well as the calcination conditions on the morphology and chemical and physical structure of the as-obtained zinc oxide (ZnO) nanofibers are deeply discussed in this work. Initially, precursor nanofibers were obtained through electrospinning, a simple and accessible process for the production of materials in nano- and sub-micrometric scales, of aqueous solution of poly (vinyl alcohol) (PVA) and zinc acetate (AcZn) in the mass ratios PVA:AcZn 1:0.5, 1:1, and 1:2. In the sequence, the precursor nanofibers were calcined (500, 600, and 700 °C, for 2 h in atmospheric air) to obtain the ZnO fibers. The precursor PVA:AcZn and the ZnO fibers were characterized through Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), X-ray diffractometry (XRD), X-ray scattering spectroscopy (EDS), Raman spectroscopy, and scanning electron microscopy (SEM). The set of results indicates that the ZnO fibers with the best characteristics (homogeneity in morphology, smaller average diameter, organization of the crystalline structure, among others) were obtained using mass ratio of PVA:AcZn 1:1 and calcination at 600 °C for 2 h in atmospheric air.

Ultra-short and dual-core photonic crystal fiber polarization splitter composed of metal and gallium arsenide

Two ultra-short polarization beam splitters (PBSs) based on surface plasma resonance (SPR) are designed for wavelengths of 1.31 and 1.55 μm. The center of the PCF has an oval hole filled with gold and the first layer of the air holes around the core is filled with the nematic liquid crystal (NLC) to enhance birefringence. In this work, the full vector finite element method is used to optimize the structural parameters. Two sets of parameters with extinction ratios of 114.02 and 111.86dB and lengths of 14.52328 and 11.02418μm are designed at wavelengths of 1.31 and 1.55 μm respectively. The results reveal that the beam splitters with broadband and short fiber length have important prospects in communication applications.

Au-nanoshells modified surface field enhanced LRSPR biosensor with low LOD for highly sensitive hIgG sensing

A high sensitivity side polished fiber long-range surface plasmon resonance (LRSPR) biosensor with electronic field enhanced through surface modified with Au-nanoshells is proposed to detect human immunoglobulin G (hIgG). LRSPR which has high penetration depth and long propagation distance can effectively detect biomacromolecules. The plasmon coupling effect between the Au-nanoshells and Au-film can enhance the electric field intensity on the surface of the sensor, which makes the proposed sensor structure have a lower limit of detection (LOD) and higher sensitivity. The experimental results show that the sensitivity as well as LOD of side-polished-fiber (SPF)/dielectric-matching-layer (DML)/Au-film/Au-nanoshells sensor is 1.84 nm/(µg/mL) and 0.20 µg/mL, which indicates better responses to hIgG with a concentration range of 1–40 µg/ml compared with the SPF/DML/Au-film sensor. The LRSPR sensor modified by Au-nanoshells was used to detect chicken serum samples and the calculated recovery is 107.62%, showing good practicality and superior self-referenced function. The biosensor has the advantages of small volume, high sensitivity and long-distance detection, and has good practicability in the field of biochemical sensing.

Wavelength Switchable Multi-Wavelength Erbium-Doped Fiber Laser Based on Polarization-Dependent Loss Modulation

We propose and demonstrate a novel and simple wavelength switchable multi-wavelength erbium-doped fiber (EDF) laser based on polarization-dependent loss (PDL) modulation with cascaded fiber Bragg gratings (FBGs) as the wavelength comb filter. PDL is generated and controlled by different polarization angles between the polarization state of each lasing line and the optical fiber polarizer in the laser cavity. The PDL modulation balances the difference between the total loss and the wavelength-dependent lasing gain. The relations among gain, loss, and laser output power under different PDL conditions are numerically analyzed on the basis of a simplified Giles model in an EDF laser system. Results show that multi-wavelength lasing lines can be built up by properly tuning the PDLs in different wavelengths. The amount of lasing lines can be switched by changing the PDL intensity in a certain wavelength. In an experiment, the PDL in that certain wavelength is modulated by utilizing four polarization controllable elements, each of which includes an FBG and a corresponding polarization controller (PC). One PC is used to control the polarization state of the reflected lasing line on the center wavelength of the FBG. A four-wavelength individually switchable EDF laser system is demonstrated by utilizing this wavelength switchable method, in which the switching operation for the single-, dual-, triple-, and four-wavelength laser output is verified. The experimental results are consistent with the theoretical results. All wavelength switching operations are conveniently controlled by merely adjusting the PCs. This simple structure and flexible wavelength switchable operations show that this multi-wavelength EDF laser has great potential in practical applications.

Double-side polished fiber for generation of mode-locked fiber lasers

A double-side polished fiber (DSPF) is fabricated for the passive generation of mode-locked pulses in an optical fiber ring cavity. The DSPF is made using a modified wheel polishing technique and coated with a cobalt oxide (Co3O4) solution as a saturable absorber (SA) to induce mode-locked operation by evanescent field interaction. The laser uses a thulium-holmium-doped fiber (THDF) for lasing in the two-micron region, with a mode-locked output having a pulse width of 1.44 ps. The repetition rate of the pulses is 11.8 MHz with a relatively high optical-signal-to-noise ratio value of 56 dB. This work demonstrates the fabrication method of the DSPF that would have potential applications as a SA for generating high power ultrafast lasers.

A dual-core fiber for tunable polarization splitters in the terahertz regime

We present a new scheme of dual-core THz fiber for tunable polarization splitter based on the mode coupling theory. Each elliptical polymer core is modified with two elliptical air holes, which is helpful for high modal birefringence and low transmission loss. Due to different coupling lengths for x and y polarizations, the two orthogonal polarizations can be easily separated in an appropriate transmission length. Characteristics of the proposed fiber are discussed numerically in detail, including modal birefringence, effective material absorption loss, coupling and splitting length, transmission loss, extinction ratio, tunability. For the THz polarization splitters, 0.865 cm splitting length is numerically demonstrated at the operation frequency of 1 THz. An efficient tuning method is provided that the operation frequency can be tuned by the applied pressure. This tuning method extends the operation frequency bandwidth from 0.9 to 1 THz in the fixed splitting length. This proposed pressure-tuning THz fiber polarization splitter has potential applications in the field of on-chip integrated THz polarization devices and in-fiber integrated optical devices.

Surface plasmon enhanced polarization filter of high birefringence photonic crystal fiber with a partial core based on filled silver nanowire

Abstract A novel kind of near-infrared communication window of photonic crystal fiber (PCF) polarization filter based on filled silver nanowire is proposed in this paper. The silver nanowire is selectively filled in a air hole of the cladding, and the performance of this PCF is analyzed by changing the diameter d2 of the near-core small air holes by finite element method (FEM). It is found that the confinement loss of x-polarization is 10738.726 dB/m, and that of y-polarization is 272.2325 dB/m at the resonance wavelength of 1.24 μm when the diameter d2 = 0.3 μm. Furthermore, when the fiber length is 1 mm, the crosstalks of x and y-polarization are −90.9 dB and 85 dB at the resonance wavelength of 1.24 μm and 1.32 μm, respectively. Thus, it can well realize the function of polarization filtering in two communication bands.

Terahertz photonic crystal fiber polarization rotator

Polarization control of terahertz (THz) waves is highly required due to their immense practical applications. Most of the THz polarization rotators in the literature depend on the transmission or reflection from metamaterials or all-dielectric metasurfaces. There is also a lack of THz polarization handling waveguides due to the material absorption in this frequency regime. In this paper, a THz photonic crystal fiber (PCF) polarization rotator (PR) is introduced and analyzed for the first time to the best of our knowledge. The suggested PCF-PR has an asymmetric porous core to decrease the material losses and increase the hybridness of the two polarized modes. Therefore, high polarization conversion ratio of 80.7% is achieved with a good crosstalk of − 18.9 d B at a frequency of 1 THz along a device length of 7.9 mm. Further, the operating frequency has a tolerance of f = 1 ± 0.1 T H z where the crosstalk is still better than − 15 d B .

Microstructural Changes during Degradation of Biobased Poly(4-hydroxybutyrate) Sutures.

Fibers of poly(4-hydroxybutyrate) (P4HB) have been submitted to both hydrolytic and enzymatic degradation media in order to generate samples with different types and degrees of chain breakage. Random chain hydrolysis is clearly enhanced by varying temperatures from 37 to 55 °C and is slightly dependent on the pH of the medium. Enzymatic attack is a surface erosion process with significant solubilization as a consequence of a preferent stepwise degradation. Small angle X-ray diffraction studies revealed a peculiar supramolecular structure with two different types of lamellar stacks. These were caused by the distinct shear stresses that the core and the shell of the fiber suffered during the severe annealing process. External lamellae were characterized by surfaces tilted 45° with respect to the stretching direction and a higher thickness, while the inner lamellae were more imperfect and had their surfaces perpendicularly oriented to the fiber axis. In all cases, WAXD data indicated that the chain molecular axis was aligned with the fiber axis and molecules were arranged according to a single orthorhombic structure. A gradual change of the microstructure was observed as a function of the progress of hydrolysis while changes were not evident under an enzymatic attack. Hydrolysis mainly affected the inner lamellar stacks as revealed by the direct SAXS patterns and the analysis of correlation functions. Both lamellar crystalline and amorphous thicknesses slightly increased as well as the electronic contrast between amorphous and crystalline regions. Thermal treatments of samples exposed to the hydrolytic media revealed microstructural changes caused by degradation, with the inner lamellae being those that melted faster.

Numerical analysis of DP-MZI–SI comb filter improvement using polarisation-maintaining fibre

In this paper, we present a numerical analysis of a novel comb filter in a double-pass Mach–Zehnder interferometer and a Sagnac interferometer (DP-MZI–SI) configuration and verify it by partial experimental demonstration. The proposed filter comprises an in-line fibre polarisation controller (PC), positioned in one arm of the Mach–Zehnder interferometer, and a polarisation-maintaining fibre (PMF) with a three-component fibre-coil PC in the Sagnac loop. The transmission of the DP-MZI–SI filter was determined using the Jones matrix of each component. This filter allows control of the free spectral range (Δλ) via two alternative modes of operation: by changing the length of the PMF or by increasing the arm length of the filter. In addition, the contrast of the interference fringes and their position can be controlled by adjusting the PCs. The possibility to generate stable patterns with narrow fringe separation was also demonstrated. Simulation results for the DP-MZI–SI filter were validated through experimental measurements. The experimental and numerical results agreed closely in terms of both Δλ and fringe visibility. The proposed DP-MZI–SI filter has characteristics suitable for application to tunable multi-wavelength and switchable fibre laser development, as well as to optical sensors, communication systems, and microwave generation.

A Novel Ultra-Broadband Polarization Filter Based on a Microstructured Optical Fiber with a Gold-Coated Air Hole.

In this paper, a pentagonal microstructured optical fiber polarization filter by utilizing a surface plasmon resonance effect is proposed. The characteristics of the mode-coupling and filtering of the filter are studied by making use of the full-vector finite element method. The performance of the filter is greatly affected by the structure parameters. The losses of Y and X polarization of the fiber core are 665.97 and 0.17 dB/cm at 1.55 μm, respectively, and the loss ratio is 3917.47. This shows that the filter has a greater loss ratio. Moreover, both the extinction ratio and tolerance are also researched, which shows that the proposed filter has a wider filtering bandwidth and better fabrication tolerance. The designed filter has an important role in wavelength-division multiplexing (WDM) and coherent optical fiber communication systems.