Poly Fiber Research Articles

Polished Fiber as a Promising Element for Coupling with a Microresonator with a Whispering Gallery Mode

Polished Fiber as a Promising Element for Coupling with a Microresonator with a Whispering Gallery Mode

A high sensitivity refractive index sensor based on microstructure fiber with simple structure and SPR effect

A novel dual-side polished photonic crystal fiber (PCF) based surface plasmon resonance (SPR) polarization filtering and refractive index (RI) sensor is presented in this paper. The cladding of PCF was composed of eight air holes and the outer surface was dual-sided polished and coated with gold film. Finite element method (FEM) was used for the simulation and design of the proposed sensor. Simulation results showed that sensor performance was better in analytes ranging from 1.33 to 1.42 RI. The wavelength and amplitude sensitivities at resonance wavelengths of 1269 and 995 nm were 27400 nm/RIU and −100.43 RIU−1 for an analyte of 1.42 and 1.41 RI, respectively, along with a spectral resolution of 3.64×10−6 RIU. Maximum loss of 52806 dB/m was obtained for an analyte of 1.41 RI towards Y-Polarization (Y-P). An extinction ratio of −105.374 dB was obtained using a fiber transferring length of 2 mm to achieve better polarization filtering effects. The proposed sensor is made of same size air holes which is easy to fabricate, cost effective, and shows better sensitivity and polarization filtering effects than several other sensors. It is expected that the sensor is suitable for wide RI detection range and capable of providing excellent polarization effect. The proposed sensor can be used for various applications including environmental detection, chemical sensing, biosensors, and pharmaceutical inspection.

High-performance Fabry-Perot fiber optic sensors from one-step laser side-polished platforms

A facile one-step non-contact process was developed for preparing the substrates for Fabry-Perot-based side-polished optical fiber sensors. A carbon dioxide (CO2) laser cladding removal technique was used to control the profile of the polished fiber surface and to introduce two reflective cavities. The substrates were characterized for a range of cavity lengths and their thermal response was studied. This device added a degree of freedom to the design of optical fiber based Fabry-Perot sensors and its potential was demonstrated by coating the substrate with polydimethylsiloxane (PDMS). The resulting sensors had a three-order of magnitude increase in sensitivity when compared to the substrate. The polished flat surface provided a route for the integration of novel materials for sensing applications, particularly those where polarization control was vital for light-matter interaction, for example, low dimensional materials such as graphene or MXene. The inherent simplicity, mechanical stability, and scalability of this approach are important steps for the realization of practical devices of this type.

Research on high sensitivity optical fiber sensing method for simultaneous measurement of seawater velocity and temperature

Aiming at the need of high sensitivity flow velocity and temperature sensor in ocean research, an optical fiber sensor for the simultaneous measurement of seawater velocity and temperature was proposed by coupling a reflective Panda fiber polarization interferometer with a hollow cylindrical cantilever, which combining the stress sensitivity of Panda fiber and optical vernier effect to achieve simultaneous measurement and sensitization of flow velocity and temperature. Firstly, the theoretical formulas of velocity sensitivity and temperature sensitivity were obtained by theoretical derivation and finite element simulation. Secondly, a velocity and temperature measurement system was established experimentally, and the maximum velocity sensitivity was –233.86 nm/(m/s) at 0.42 m/s with the mean relative error compared with the theoretical sensitivity was 3.8 %, the maximum temperature sensitivity was −14.5 nm/(°C) with the mean relative error compared with the theoretical sensitivity was 8 %. Finally, nine different sets of seawater velocity and temperature were measured using the sensitivity matrix and compared with the Acoustic Doppler Velocimetry and Conductivity-Temperature-Depth meter, the mean relative error of velocity and temperature measurement results were 2.8 % and 2 %, respectively. The optical fiber sensor based on the cantilever is expected to play an important role in the field of ocean flow field measurement because of high sensitivity and the ability to measure velocity and temperature simultaneously.

Research on Flexural Properties and Flexural Toughness Evaluation Method of Steel Fiber Reinforced Cementitious Composites under Polar Low Temperatures

In this research, five groups of steel fiber reinforced cementitious composite (SFRCC) with different fiber volume content (0%, 0.5%, 1.0% 1.5%, and 2.0%) were designed to perform four-point flexural tests on beam specimens to study the effects of polar temperature (20, 0, −25, −50, −75, and −100°C) and fiber volume content on the flexural properties. The flexural toughness index and load holding capacity index were calculated based on the load–displacement curve, and the enhancement and toughening mechanisms of SFRCC by low temperature and steel fibers were analyzed in conjunction with experimental observations. The results of the proposed flexural toughness evaluation method show that the flexural toughness of SFRCC can significantly improve than that of ambient temperature when the temperature is lower than 0°C. With the decrease in temperature, the flexural property of SFRCC increases first and then decreases, and the temperature point of this transition is around −50–−75°C. The flexural property enhancement effect of 1.0% fiber volume content SFRCC is more significant in low temperatures according to the flexural toughness index and load holding capacity index. The conclusion can provide a reference for the application of SFRCC in cryogenic engineering, as well as a simple and quantifier evaluation method for flexural toughness is proposed.

Coherence-tailorable vector fiber source

Apart from the polarization and spatial mode, the degree of coherence (DoC), as a new degree of freedom (DoF), has actuated the control of structured optical fields beyond into a higher dimension. However, the control of DoC mainly focuses on the spatial coherence, and so far, there are no reports on the modulation of temporal coherence of the structured light. Here, a temporal coherence-tailorable vector fiber source is proposed and experimentally demonstrated. With a two-mode long-period fiber grating and polarization control, switchable transverse-mode outputs including azimuthally polarized mode TE01 and radially polarized mode TM01 are performed in an all-fiber compact regime. Benefitting from a tunable superfluorescent fiber source as the illumination of spatial mode control, the temporal coherence and the operating wavelength of vector beams can be simultaneously modulated. This work may not only advance a considerable protocol for creating and manipulating high-dimensional vectorial optical field, but also open up a promising avenue for potential applications in optical communication, high-resolution imaging, and particle trapping.

A grating-modified broadband D-type photonic crystal fiber polarization filter

In this paper, a D-type grating-modified broadband photonic crystal fiber polarization filter based on surface plasmon resonance is proposed. The asymmetric design of D-type photonic crystal fiber is helpful to achieve single-mode polarization filtering, and grating can increase the coupling between the core mode and the SPP mode and thus increase the constraint loss. From our simulation results, it can be seen that the applicable bandwidth range can easily reach 1 μm. At the communication wavelength of 1750 nm, the calculated constraint losses of x-polarized and y-polarized core modes are 4.2526 dB cm−1 and 1491.8 dB cm−1, respectively, and the crosstalk is up to 1292 dB. The proposed grating-modified of photonic crystal fiber has achieved good filtering effect in the near-infrared band, and even extended to the mid-infrared band.

Prescriptive method for fiber polarization compensation in two bases.

Single-mode optical fibers exhibit a small but non-negligible birefringence that induces random polarization rotations during light propagation. In classical interferometry these rotations give rise to polarization-induced fading of the interferometric visibility, and in fiber-based polarimetric sensors as well as quantum optics experiments, they scramble the information encoded in the polarization state. Correcting these undesired rotations is consequently an important part of many experiments and applications employing optical fibers. In this Lab Note we review an efficient method for fully compensating fiber polarization rotations for general input states. This method was not originally devised by us, but does, to the best of our knowledge, not appear in the literature, and our interactions with the community have indicated that it is not well known.

Degradable side-by-side fiber of poly(butylene succinate-co-terephthalate)/poly(L-lactic acid) with half-wrinkled surfaces and fully crimped structures

Melt composite spinning was utilized to successfully produce the degradable side-by-side fibers employing poly(butylene succinate-co-terephthalate) (PBST) and poly(L-lactic acid) (PLLA). The structures, elasticity during recycling, and biodegradability of fibers were investigated. The findings reveal that the fibers contain entirely crimped structures and intriguing half-wrinkled surfaces, similar to half rings aligned along the fiber axis. After five cycles, the crimp elastic ratio can reach 96.3 % ± 1.7 %. After nine days, the mass loss can reach 17.50 wt% deteriorated.

Ultra-broadband small-size dual-core photonic crystal fiber polarization splitter based on silver coating

We have proposed a novel silver-coated ultra-broadband small-size dual-core photonic crystal fiber (DC-PCF) polarization splitter which achieves a short length, high extinction ratio (ER) and ultra-wide bandwidth at the commonly used communication wavelength band. Finite element method-based numerical simulation is applied to carry out a thorough investigation for wavelength from 1 to 2 μm. According to the simulation results, the coupling qualities of the proposed structure can be improved by resonant coupling between the core guide mode and the surface plasmon polarization (SPP) exciton mode. By analyzing the change of ER with varying wavelength, the ER value of this work are achieved as 67.4 and 67.1 dB when the wavelength are 1.14 and 1.57 μm, respectively. The final splitting length (LS) is 17.17 μm. To the best of our knowledge, it is difficult to achieve in all previous studies. With a splitting bandwidth of 900 nm (1.0–1.9 μm) and the ER value of −50.1 dB at 1.55 μm, the E + S + C + L + U communication bands are completely covered. The proposed model has excellent beam-splitting performance, such as ultra-short LS, ultra-wide splitting bandwidth and good tolerance performance, with potential applications in optical fiber communications or fiber laser devices.

Effects of thickness and roughness on plasmonic characteristics of gold thin films deposited on polished optical fiber

The thickness and roughness of metal layers substantially affect the performance of surface plasmon resonance (SPR)-based sensors. The deposition methods, control parameters, and substrate characteristics influence the layer thickness and roughness. This study investigates the SPR characteristics of a polished optical fiber surface coated with gold (Au) metal of different thicknesses. The Au layer is deposited via the thermal evaporation method, and its thickness is varied by controlling the deposition time (3–6 min). A proportionality relationship between thickness and deposition time is observed. Island-shaped structures in gold (Au) morphology are formed due to low adhesion to the substrate. The shape of this island creates gaps in the layer, causing scattering. In addition, the roughness on the gold surface triggers the Localized Surface Plasmon Resonance (LSPR) phenomenon. As a result, the measured dielectric characteristics differ from the reference. The SPR curve calculation simulation was carried out based on reference optical parameters and measurement results by an ellipsometer, which were then compared with experiments. The obtained results show that the substrate roughness, morphology, and thickness of the Au layer play an essential role in determining the characteristics of the SPR curve in a fiber optic plasmonic sensor. As a result, in basic experiments, the sample with an Au thickness of 27.37 nm (deposition time = 3 min) shows better characteristics (half-maximum full width, minimum transmittance, and resonance wavelength) compared with the sample with an Au thickness of 53.97 nm (deposition time = 4 min), Although 53.97 nm is the optimal thickness from the simulation using reference optical parameters (smooth substrate surface and smooth gold layer).

Fabrication and multiphysics numerical investigations of carbon fiber structural batteries

The structural battery (SB) that uses carbon fibers as anodes is a lightweight composite material battery integrating load bearing and energy storage. However, during usage, diffusion-induced stress may result in structural failure and a reduction in the battery capacity. In this paper, a laminated structural battery (LSB) was fabricated using carbon fiber cloth as an anode and collector and successfully powered LEDs. Then, based on this laminated structure, a multiphysics field model based on electrochemical-mechanical coupling is established for the analysis of complicated diffusion-induced stresses in carbon fibers. Following this model, researchers investigate the electro-chemo-mechanical behaviors and influencing factors of the SB and compare them with those of the lithium-ion battery (LIB). The results show that diffusion polarization in carbon fibers is aggravated by their lower diffusion coefficient, larger radius, and higher discharge rate; in both types of batteries, there is a higher tensile diffusion stress and a higher probability of failure at the surface of the anode active material than in the interior; a more uniform distribution of diffusion-induced stress on the surface of fibers at different locations; when discharging at a high rate, the SB capacity hardly reduces, and the high strength and relatively low diffusion-induced stress in the carbon fiber make it much safer, showing excellent electrochemical performance and resistance to failure due to diffusion-induced stress. This study demonstrates the feasibility of the fabrication and safety of carbon fiber structural batteries, which may potentially offer recommendations for the fabrication and use of novel SBs.

Monitoring Reinforced Concrete Structures Using Iron Thin Film Coated Optical Fibre Sensors

Structural health monitoring (SHM) of reinforced concrete structures (RCS) is crucial for mitigating the consequences of their deterioration. By identifying and addressing the issues early, SHM helps reduce environmental impact, safeguard lives, and enhance economic resilience. Rebar corrosion is a leading cause of early RCS decay and optical fibre sensors (OFS) have been employed for its monitoring. Reflection optrodes using optical fibres where the tip is coated with iron (Fe) thin films offer a robust, longlasting and straightforward solution. This study investigates the tracking of spectral changes during the Fe thin film corrosion, which has been neglected in the literature, in favour of tracking reflection changes from thin film spalling. A multimode fibre tip, coated with a thin Fe layer embedded in concrete, allows spectral changes to be observed during corrosion. A 100 nm thick Fe film was deposited using radio frequency magnetron sputtering on polished fibre tips. Corrosion was induced by applying salted water drops and allowing the fibre tip to dry. Corrosion monitoring was successful for both air-exposed and cementembedded tips, with results compared to reflection simulations of Fe, Fe2O3, and Fe3O4 thin films. This study supports monitoring at different wavelengths, enhancing robustness, cost-effectiveness and earlier detection.

AuNPs/GO Coated U-Shape Polished SMF Based Localized SPR Sensor for Musta’mal Water Identification

Potential of hybrid gold nanoparticles/graphene oxide (AuNPs/GO) coated single mode fiber (SMF) sensor by exploiting localized surface plasmon resonance (LSPR) effect for Musta’mal water identification was studied. Three structure shapes of fiber optics such as straight-shape, loop-shape and u-shape had been prepared. Three layers of AuNPs with 50 nm in diameter were drop-casted onto the partially unclad polished single mode fiber (SMF) to observe the maximum sensitivity of LSPR. To enhance the LSPR effect, one layer of GO was deposited on top of the AuNPs layer. Two optical light sources with least attenuation (1310 nm and 1550 nm) were employed to study the optical power output as the sensor immersed in different type of water samples. The u-shape SMF portrayed the maximum output power about 24.2 dBm at 1550 nm wavelength. According to the analysis, the deployment of 1550 nm laser wavelength resulted in better sensitivity with 23.2% improvement compared to 1310 nm wavelength. Apparently, the LSPR phenomenon created by AuNPs/GO able to enhance the plasmonic signal up to 51.9% than the uncoated SMF. The thinnest diameter of SMF’s cladding, d=0.1195 mm with U-shape structure exhibited the highest power different of 1.10 dBm, in which suggested the best sensing performance. In conclusion, the optimization of AuNPs/GO u-shape polished SMF resulted in the maximum sensitivity with value of S=72.7 dBm/RIU for Musta'mal water identification.

High resolution curvature sensor based on enhanced backscattering in side polished optic fiber

A high-resolution curvature sensor based on enhanced backscattering in side polished optic fiber is proposed and experimentally investigated. Directional curvature sensor fabrication procession and operating principle are introduced. A push–pull structure with 2 side polished curvature sensors sticking on opposite sides of an elastic beam is used to enhance sensitivity and responsive linearity. Experiments are carried out by high accuracy relative intensity (RI) measurement system based on modified pulse self-referencing technology. Experimental results show that curvature sensor can achieve a sensitivity of 15.21 dB/m−1 in the curvature range of −0.48–0.48 m−1, and the curvature resolution is as low as 2 × 10−5m−1.

Passively Q-switched and mode-locking fiber laser based on Sb2S3 saturable absorber

Stable mode-locking pulses were obtained in an erbium-doped fiber laser (EDFL) by using antimony sulfide (Sb2S3) as saturable absorber (SA). The Sb2S3-SA fabricated with the optical deposition method was connected to a ring cavity of EDFL for Q-switching and mode-locking, respectively. When the configuration of the fiber cavity is compact with a cavity length of 5 m, Q-switched pulses were generated with repetition frequency from 60.6 kHz to 69.9 kHz by tuning the pump power. Moreover, when additional single-mode fiber (SMF) was inserted into the cavity, self-started mode-locking with ps pulses was obtained. For further investigating the performance of the SA in mode-locking, an inline fiber polarizer was inserted into the compact cavity to achieve hybrid mode-locking operation generating pulses with pulse widths of fs and a fundamental frequency of 29.2 MHz with a signal-to-noise ratio (SNR) of 76 dB. The experimental results indicate that the Sb2S3 material has great application prospects in ultrafast optics due to its excellent optical properties.

Double nested dual-core negative curvature fiber polarization beam splitter

In this paper, a polarization beam splitter（PBS） based on double nested dual-core negative-curvature fiber (DNHC-NCF) is designed. Two hollow cores are constructed by eight double nested cladding tubes arranged at certain angles. The influences of structural parameters on the performances of the DNHC-NCF PBS have been studied by using the finite element method (FEM). According to the simulation results, the structure of the proposed DNHC-NCF PBS is optimized. The final results indicate that the length of the proposed DNHC-NCF PBS is 1.38 cm and the extinction ratio (ER) is less than −20 dB in the wavelength range of 1.48–1.80 µm (320 nm, covers S + C + L + U bands). Besides, the higher order mode extinction ratio (HOMER) in the wavelength range of 1.3–1.71 µm is greater than 100, showing good single-mode characteristic as well. It is believed that the proposed double nested dual-core negative curvature fiber polarization beam splitter will have important applications in the fields of optical communication system.

Effect of alkali-treated bamboo fibers on the properties of asphalt mixture

ABSTRACT Bamboo fiber is a natural fiber that is ecologically beneficial and one of the best materials to replace lignin fiber for roads, which is still difficult to utilize properly in asphalt mixtures owing to its poor adherence, dispersion, and hydrophilicity. Previous research has discovered that alkali treatment, as an effective treatment approach, may effectively lower the hydrophilicity of plant fibers and improve their compatibility with the matrix. As a result, it is vital to investigate the effect of alkali treatment on bamboo fibers used in asphalt mixtures. The composition and microstructure of bamboo fibers treated with alkali were investigated using SEM and FTIR methods, while the adhesion between the bamboo fiber and asphalt before and after alkali treatment was tested using the fiber pull-out test. In addition, the dispersion rate of bamboo fibers in asphalt mixture was determined by developing a connection equation using the Schellenberg binder drainage test. The performance of bamboo fiber asphalt mixtures was then evaluated using rutting tests, beam bending tests, immersion Marshall tests, freeze-thaw splitting tests, and cyclic fatigue testing. The results showed that the alkali treatment successfully eliminated impurities in the outer layer of the bamboo fibers and reduced their hydrophilicity, which enhanced the asphalt-bamboo fiber interactions as well as the asphalt mixture’s water damage resistance, specifically manifested as the residual stability of ABM was enhanced by 7.8% and the splitting tensile strength of ABM was raised by 12.2%. Furthermore, the surface polarity of the bamboo fibers was reduced, which weakened the agglomeration phenomenon and increases the dispersion rate of bamboo fibers in the mixture by 9%, efficiently improving the low-temperature cracking resistance and fatigue performance of asphalt mixtures.

Passively mode-locked fiber lasers dynamic behavior by multimode fiber polarization controller

Passively mode locked fiber lasers (PML-FLs) can produce a variety of phenomena due to the nonlinear effects. With the introduction of the nonlinear polarization rotation (NPR) and a multimode fiber polarization controller (MMF-PC), we observed nonlinear effects in our erbium-doped mode-locked fiber laser, such as the evolution of the soliton bunch to dissipates soliton resonance (DSR) pulses. In the evolution of the soliton bunch to DSR pulses, the soliton square bunch and the multi-longitudinal mode oscillation also appeared in our experiment with the increasing the pump power. To illustrate the importance of MMF-PC, a control experiment is conducted by replacing the MMF-PC with a single mode fiber PC (SMF-PC). The experimental results indicate that the MMF-PC are crucial for the evolution of soliton pairs to DSR pulses and the generation of soliton pairs. The NPR mode-locked structure is used to achieve dual-wavelength filtering, its strength-dependent non-uniform loss can effectively suppress the mode competition in the gain fibers. The MMF-PC in the mode-locked structure adds a polarization burned hole effect inside the resonator. We achieved dual-wavelength mode locking by adjusting the PC to control the birefringence and loss in the resonator.

Switchable and tunable orthogonal single-polarization dual wavelength SLM fiber laser based on parity-time symmetric system and PM-FBG

A dual-wavelength narrow linewidth orthogonal single polarization fiber laser based on a parity-time (PT) symmetric system is proposed and demonstrated, which achieves the function of tunable and switchable wavelength, and single longitudinal mode (SLM) operation. The PT symmetric system composes of a single physical loop, which includes two polarization controllers (PCs) and a polarization beam splitter (PBS). By modulating PCs to match gain, loss and coupling coefficient, the switchable wavelength and stable SLM laser output have been achieved. Through stretching the polarization maintaining fiber Bragg grating (PM-FBG), the wavelength adjustment range from 1549 nm to 1551 nm is obtained. In the process of tuning, the full width at half maxima (FWHM) linewidths and polarization states at each wavelength have been measured and keep basically stable. The measured FWHM linewidths are less than 13.66 kHz and 11.89 kHz. Further, the stable orthogonal single polarization state has been realized. The degree of polarization (DOP) at each wavelength exceeds 97% and basically remains unchanged during 20 min.