Poly Fiber Research Articles

Algorithm Optimization for Rockfalls Alarm System Based on Fiber Polarization Sensing

Algorithm Optimization for Rockfalls Alarm System Based on Fiber Polarization Sensing

Discrete frequency-bin entanglement generation via cascaded second-order nonlinear processes in Sagnac interferometer.

Discrete frequency-bin entanglement is an essential resource for applications in quantum information processing. In this Letter, we propose and demonstrate a scheme to generate discrete frequency-bin entanglement with a single piece of periodically poled lithium niobate waveguide in a modified Sagnac interferometer. Correlated two-photon states in both directions of the Sagnac interferometer are generated through cascaded second-order optical nonlinear processes. A relative phase difference between the two states is introduced by changing the polarization state of pump light, thus manipulating the two-photon state at the output of the Sagnac interferometer. The generated two-photon state is sent into a fiber polarization splitter, and then a pure discrete frequency-bin entangled two-photon state is obtained by setting the pump light. The frequency entanglement property is measured by a spatial quantum beating with a visibility of 96.0±6.1%. The density matrix is further obtained with a fidelity of 98.0±3.0% to the ideal state. Our demonstration provides a promising method for the generation of pure discrete frequency-bin entanglement at the telecom band, which is desired in quantum photonics.

A THz fiber polarization splitter based on anti-resonant hollow-core fiber with the asymmetric dual-suspended cores

In this paper a novel THz fiber polarization splitter based on anti-resonant hollow-core fiber with asymmetric dual-suspended cores has been proposed. For the proposed polarization splitter, the ultra-low confinement loss and great polarization splitting performance in the THz band can be achieved, which benefits from the good combination of anti-resonance mechanism with refractive index guidance mechanism. In order to confine the THz wave well in the central large air hole, 8 sets of anti-resonance rings are introduced into the cladding of the fiber. Moreover, the asymmetric dual-suspended cores are used to control the polarization state of the guiding light for enhancing the polarization splitting effect, which exists in the central large air hole of anti-resonant hollow-core fiber. One of the dual cores is designed with a symmetrical structure to reduce the birefringence effect. The other core is designed with an asymmetric structure to increase that in the THz band. The numerical simulations results show that the THz polarization splitter with a length of 0.37 cm is realized in the operating band around 1 THz by optimizing the geometric structure of the dual-suspended-core fiber, and the confinement losses of both x and y polarization modes are lower than 6 × 10−3 dB/cm. Furthermore, the working bandwidth at the center frequency of 1 THz can reach ∼0.06 THz, and the extinction ratio is better than 20 dB. The proposed THz polarization splitter has the characteristics of special short length, low loss and broad bandwidth. In conclusion, it has some potential applications of polarization devices in the field of optical fiber sensing and optical fiber communications.

Handling mode and polarization in fiber by fs-laser inscribed (de)multiplexer and silicon switch array

The emergence of dynamic optical switching has opened up new perspectives for lightening the ever growing load on the electrical switches and routers, to meet the increasing demand on high-speed and flexible data processing and management in fiber-optic communications. Despite diversity schemes of optical switching in the single-mode regime, multi-mode switching of the hybrid fiber and chip system enabled by photonic integrated circuits, especially for the fiber-chip-fiber system, is still an outstanding challenge. Here, we propose and demonstrate the mode and polarization transmission and switching fiber-chip-fiber system with few-mode fibers (FMFs), including the FMF links for mode- and polarization-division multiplexing data transmission, the femtosecond (fs)-laser inscribed 3-dimensional (3D) photonic lantern silica chip for (de)multiplexing and coupling between FMFs and chip, and the topology-optimized N × N non-blocking 2-dimensional (2D) silicon switch array chip for switching and routing. Using 30-Gbaud quadrature phase-shift keying signals on wavelength-division multiplexing (WDM) channels, the WDM-compatible hybrid mode/polarization transmission, switching and routing system with FMFs, fs-laser inscribed silica (de)multiplexing chip and silicon switch array chip are demonstrated in the experiment with favorable operation performance. The demonstration may open the door for developing robust multi-dimensional optical data processing in fiber-optic communication systems with versatile fibers and chips.

Enhancing Compatibility and Mechanical Properties of Natural Rubber Composites

Pure natural rubber (NR) exhibits low mechanical properties, necessitating the incorporation of additives like vulcanizing agents and fillers. Carbon black and silica, conventional fillers, are relatively expensive and not environmentally friendly. This study explores using Oil Palm Empty Fruit Bunch (OPEFB) fiber as an affordable, abundant, and biodegradable alternative filler for NR. However, compatibility issues arise between the nonpolar NR and the polar OPEFB fiber. A latex-starch hybrid coupling agent (CA (NR-St)) was added to the composite formulation to address this. NR, OPEFB fiber, and the coupling agent were mixed using an open roll mill with a 10 phr OPEFB filler loading and coupling agent concentrations of 0, 1, 2, and 3 phr. Fourier-transform infrared spectroscopy (FTIR), rheology, and mechanical property tests revealed that the coupling agent improved the compatibility between NR and OPEFB fibers, as evidenced by increased tensile strength and stiffness. The composite with 3-phr coupling agent exhibited the best performance with tensile strength and stiffness values of 25.6 MPa and 3.7 MPa, respectively. This increase in mechanical properties has the potential to act as a catalyst for increasing the use of renewable materials in the rubber industrial sector, especially the automotive industry.

High-Loss Dual-Channel Broadband Photonic-Crystal Fiber Polarization Filter Based on Surface Plasmon Resonance

High-Loss Dual-Channel Broadband Photonic-Crystal Fiber Polarization Filter Based on Surface Plasmon Resonance

Design of high-performance photonic crystal fiber polarization filter by Grey Wolf Optimizer with convolutional neural network

In this paper, a D-shaped photonic crystal fiber polarization filter is optimized using a novel machine learning framework. The framework incorporates the Grey Wolf Optimizer (GWO) and convolutional neural network (CNN) to optimize the optical fiber structure parameters. The designed CNN accurately classifies optical fiber modes, while the GWO selects complex fiber structure parameters. The fitness function conducts multi-objective optimization on the confinement loss and resonance wavelength of the polarization filter. The simulation results show the y-direction confinement loss of the optimized polarization filter is 1111.51 dB/cm at a wavelength of 1.55 µm. At a fiber length of 1000 µm, the crosstalk on the communication band reaches 965.3 dB, with a bandwidth exceeding 1000 µm. Numerical analysis demonstrates that the performance of the designed PCF filter is better than that of the original and also have showed the superiority of the proposed framework, which is a promising avenue for designing other photonic devices.

Radiation-induced attenuation of hollow-core photonic bandgap fiber for space applications

Radiation-Induced Attenuation (RIA) is a crucial parameter for the applications of fiber optic gyroscopes in space environments. Under the irradiation of a 60Co source with a radiation rate of 10 rad/s and a total radiation dose of 138 krad, we make real-time measurements of RIA and evaluate the recovery process of homemade 19-cell HC-PBGF and commercial PPMF. Experimental results demonstrate that there is only a 0.45 dB/km loss increment for the RIA of homemade HC-PBGF at the wavelength of 1550 nm, which is only about 1/27 of that of the PPMF. After the radiation source is turned off, the loss of HC-PBGF returns to the initial level before radiation in the tenth hour, but the RIA of PPMF has only a 20% recovery on the seventh day. We first theoretically investigate the kinetics and phenomenological equation of RIA in the Hollow-Core Photonic Band-Gap Fiber (HC-PBGF) and commercial Panda Polarization Maintaining Fiber (PPMF) in the γ-rays environment. Theoretical results proved that the initial defect concentration and RIA increase rate of HC-PBGF are only 1/3 and 1/6 of that of the PPMF. This proves that HC-PBGF can significantly reduce the RIA and exhibits a strong capacity of irradiation resistance, which is of great significance to promote fiber optic gyroscopes for space applications.

Design of a photonic crystal fiber polarization beam splitter with simple structure and ultra-wide bandwidth

A novel polarization beam splitter (PBS) based on dual-core photonic crystal fiber (DC-PCF) is proposed in this work. The proposed DC-PCF PBS contains two kinds of lattices and three kinds of air holes to form the asymmetrical elliptic dual-core structure. By using the full-vector finite element method, the propagation characteristics of the proposed DC-PCF PBS are investigated. The simulation results show that the bandwidth of the proposed DC-PCF PBS can reach to 340 nm, which covers the S + C + L + U communication bands, the shortest splitting length is 1.97 mm, and the maximum extinction ratio appears near wavelength 1550 nm. Moreover, the insertion loss of the proposed DC-PCF PBS is very low. It is believed that the proposed DC-PCF PBS has important applications in the field of all-optical communication and network.

Analysis of measuring distance error caused by thermal fluctuation and development of error reduction technique for frequency-modulated continuous-wave method

To improve the robustness of frequency-modulated continuous-wave (FMCW) distance measurement systems, we clarified the effect of temperature changes in the surroundings. In particular, the temperature change causes a phase change between the slow-axis and fast-axis polarization of the optical fiber, which in turn causes a distance error. Numerical analysis using a model of the phase state of polarization revealed that a distance gain error occurs in the reference fiber interference unit and a distance offset error occurs in the measurement fiber interference unit of the FMCW distance measurement system. We propose two measurement-error reduction methods that suppress the phase change in polarization in accordance with the characteristics of each interference unit. Experimental evaluations showed that the measurement errors were reduced from 5 μm to 1 μm and the temperature robustness of the system was improved.

Hollow-Core Antiresonant Chalcogenide Fiber Polarization Filter Operating at 3 μm Wavelength Based on Surface Plasmon Resonance

Hollow-Core Antiresonant Chalcogenide Fiber Polarization Filter Operating at 3 μm Wavelength Based on Surface Plasmon Resonance

Fiber optic temperature and strain sensor using dual Mach-Zehnder interferometers.

A fiber optic temperature and strain sensor using dual Mach-Zehnder interferometers (MZIs) is proposed. The dual MZIs were fabricated by fusion splicing of two different fibers between two single-mode fibers. The two fibers of thin-core fiber and small-cladding polarization maintaining fiber were fusion spliced with a core offset. As the responses of the two MZIs are different in terms of temperature and strain, simultaneous temperature and strain measurement were experimentally validated by selecting two resonant dips in the transmission spectrum to construct a matrix. Experimental results show that the proposed sensors had the maximum temperature sensitivity of 66.67pm/°C and the maximum strain sensitivity of -2.0p m/µε. The minimum discriminated temperature and strain of the two proposed sensors were 0.20°C and 0.71µε, and 0.33°C and 0.69µε, respectively. The proposed sensor has promising application prospects due to the merits of ease of fabrication, low costs, and good resolution.

Bright and Polarized Fiber In-Line Single-Photon Source Based on Plasmon-Enhanced Emission into Nanofiber Guided Modes

We demonstrate a bright and polarized fiber in-line single-photon source based on plasmon-enhanced emission of colloidal single quantum dots into an optical nanofiber. We show that emission properties of single quantum dots can be strongly enhanced in the presence of single gold nanorods leading to a bright and strongly polarized single-photon emission. The single photons are efficiently coupled to guided modes of the nanofiber and eventually to a single-mode optical fiber. The brightness (fiber-coupled photon count rate) of the single-photon source is estimated to be $12.2\ifmmode\pm\else\textpm\fi{}0.6$ MHz, with high single-photon purity [${g}^{2}(0)=0.20\ifmmode\pm\else\textpm\fi{}0.04$] and degree of polarization as high as 94--97 %. The polarized and fiber-coupled single photons can be implemented for potential applications in quantum photonics.

Silicon-based decoder for polarization-encoding quantum key distribution

Silicon-based polarization-encoding quantum key distribution (QKD) has been widely studied, owing to its low cost and robustness. However, prior studies have utilized off-chip devices to demodulate the quantum states or perform polarization compensation, given the difficulty of fabricating polarized independent components on the chip. In this paper we propose a fully chip-based decoder for polarization-encoding QKD. The chip realizes a polarization state analyzer and compensates for the BB84 protocol without requiring additional hardware. It is based on a polarization-to-path conversion method that uses a polarization splitter-rotator. The chip was fabricated using a standard silicon photonics foundry; it has a compact design and is suitable for mass production. In the experimental stability test, an average quantum bit error rate of 0.59% was achieved through continuous operation for 10 h without any polarization feedback. Furthermore, using the developed feedback algorithm, the chip enabled the automatic compensation of the fiber polarization drift, which was emulated by a random fiber polarization scrambler. In the case of the QKD demonstration, we obtained a finite-key secret rate of 240 bps over a fiber spool of 100 km. This study represents an important step toward the integrated, practical, and large-scale deployment of QKD systems.

Ultrasensitive Strain Sensor Based on Core-Bending Long Period Fiber Grating

In this letter, a novel core-bending long period fiber grating (CB-LPFG) based on symmetrical polished fiber plane is designed and experimentally testified. By employing methods of CO2-laser polishing and oxyhydrogen flame heating, periodic bending cores are achieved on a symmetrical polished plane. Due to the reduction of the cladding and the bent core, the sensitivity of the structure is strongly enhanced. Experimental results present that the highest strain sensitivity of CB-LPFG with 7 periods reaches -0.846 nm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> . To the best of our knowledge, is firstly increasing the strain sensitivity of fiber sensor based on single-wavelength demodulation to nm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> level. Meanwhile, the temperature sensitivity of CB-LPFG is 236 pm/°C with dynamic range of 30- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$130~^{\circ }\text{C}$ </tex-math></inline-formula> . Consequently, the proposed sensor is expected to offer significant potential to detect micro-deformation more precisely.

Efficient second-harmonic generation through cascaded optically poled fibers.

We report the experimental demonstration of efficient second-harmonic generation by splicing optically poled fiber segments. A device made from five segments each 20cm-long exhibits, at a fundamental average power of 4.2mW, a maximum increase of 5.5 in the conversion efficiency with respect to a single 20cm poled fiber, corresponding to a conversion efficiency of 5.4%. For any considered fundamental power, the conversion efficiency at the output of a five-segment device is larger than the efficiency of a single poled fiber having the same length.

Fast characterization of in-plane fiber orientation at the surface of paper sheets through image analysis

The in-plane fiber orientation distribution has a decisive impact on paper mechanical and dimensional properties (e.g., tensile stiffness, hygroexpansion). It is usually estimated offline through relatively expensive bench instrumentation such as diffusion-based optical methods and ultrasonic devices. In this work we present an alternative methodology that is fast, portable, inexpensive and able to provide the complete surface polar fiber orientation profile. The proposed technology combines an image acquisition setup, consisting of a digital camera with a low angle illumination system, with the gradient-segmentation method (GSM), a robust image analysis algorithm. This camera-GSM methodology presented high internal consistency, accurately identifying the angles of samples subjected to known rotations at the imaging step. The methodology also produced comparable results to the TSO (tensile stiffness orientation) technique, used as reference. The methodology is easily transferable to plant operation, including for the online assessment of fiber orientation.

Polarization and Torsion Insensitive Fiber Bragg Grating Written in Polarization Maintaining ZEBRA Fiber With Artificial Anisotropy

We present first fiber Bragg grating (FBG) inscribed in polarization maintaining (PM) optical fiber with artificially anisotropic core achieved by an appropriate distribution of discrete germanium-doped areas in nanoscale. We proved that this FBG reveals unique properties. Its single-resonance spectral shape, strain and temperature sensitivities are similar to that for grating written in cylindrically symmetrical optical fiber, which indicates that it behaves as the grating fabricated in a non-PM fiber, whereas it is written in the fiber that preserves the orthogonal polarization components of the mode. Moreover, due to the relatively low birefringence of the fiber, the FBG is insensitive to the excited polarization state and twist, and only a negligible shift of the spectrum is noticeable with no changes in its shape. Thus, FBG inscribed in ZEBRA fiber is a kind of hybrid structure that can be used for all-fiber lasers that generate polarized wave, as well as for polarization fiber sensors and components with spectral insensitivity to random or intentional twist.

Cyclic Freezing Effect on Silver Nanoparticle Adsorption on Polished Collagen Fiber

Cyclic Freezing Effect on Silver Nanoparticle Adsorption on Polished Collagen Fiber

Spectral Broadening Suppressed by a Gain-Enhanced Fiber in Polarization Maintaining High-Power Systems

A gain-enhanced 10/125 μm polarization-maintaining Yb-doped fiber (PMYDF), with the cladding absorption of 7.5 dB/m at 976 nm, for narrow linewidth linearly polarized fiber oscillator or amplifiers is presented. By utilizing the gain-enhanced PMYDF in an all-fiber laser oscillator, an output power of 123 W is achieved with applying appropriate bending strategies and thermal management, corresponding to the slope efficiency of 86.7%. By applying the gain-enhanced PMYDF in seed, an increase of 34% in the longitudinal mode interval is effectively achieved compared to the commercial PMYDF, while the number of longitudinal modes is only 75%. According to the main oscillation power amplification (MOPA) system, the total amount of spectral broadening applying the seed with the gain-enhanced PMYDF are only 67%, 64% and 54% of applying the seed with the commercial PMYDF, corresponding to co-pumping, bi-pumping and counter-pumping schemes, respectively.