Core Multimode Research Articles

Multichannel Directional Recognition SPR Curvature Sensor Based on D-Type Double-Clad Multimode Fiber

A fiber surface plasmon resonance (SPR) curvature sensor has the advantage of being insensitive to axial strain and temperature, but there are still difficulties in multichannel cascade and curvature direction identification. In this article, a multichannel directional recognition SPR curvature sensor based on D-type double-clad multimode fiber was proposed. The asymmetric structure of D-type multimode fiber can well realize directional curvature sensing. When the light in the multimode core leaks to the silica clad, due to the existence of plastic clad, it can still continue to transmit. When the refractive index of UV curable adhesive coated in different sensing areas is different, wavelength-division multiplexing multichannel sensing can be realized. When the sensing probe is bent to be convex, the maximum intensity sensitivity is 0.0057 a.u./m−1, the resonance wavelength is redshift, and the wavelength sensitivity is 0.6114 nm/m−1. When the sensor probe is bent to be concave, the maximum intensity sensitivity is 0.0043 a.u./m−1, the wavelength is blueshift, and its highest sensitivity is 0.5831 nm/m−1. In addition, this article also realizes a three-channel directional recognition SPR curvature sensor based on a D-type double-clad multimode fiber, which provides a new scheme for multichannel directional curvature measurement.

A photonic crystal fiber broadband mode converter with highly fitting propagation constant

In this paper, we propose a broadband mode converter based on photonic crystal fiber (PCF) starting from the method of propagation constant height fitting. Using the finite element method and the beam propagation method, three typical mode converters in the S + C + L range, LP01 to LP11, LP01 to LP21, and LP01 to LP31, are calculated. Numerical results show that the mode coupling efficiency of this mode converter is over 90% and the mode extinction ratio is over 10 dB. This converter can realize pattern multiplexing in a cascade manner. On this basis, we propose a multi-core mode multiplexer structure. On the premise of sacrificing some performance, three modes can be reused at the same time. Mode converters of PCF structure can be fabricated by PCF post-processing technology. It is expected to become an important part of the future mode division multiplexing (MDM) optical communication system.

High-energy Q-switched 16-core tapered rod-type fiber laser system.

High-energy Q-switched master oscillator power amplifier systems based on rod-type 4 × 4 multicore fibers are demonstrated, achieving energy up to 49 mJ in ns-class pulses. A tapered fiber geometry is tested that maintains low mode order in large multimode output cores, improving beam quality in comparison to a similar fiber with no taper. The tapered fiber design can be scaled both in the number of amplifying cores and in the dimensions of the cores themselves, providing a potential route toward joule-class fiber lasers systems.

Do-it-yourself three-dimensional large core multimode fiber splitters through a consumer-grade 3D printer

We report the design, fabrication and characterization of 3D large core (1 mm) multimode fiber splitters using a low-cost stereolithography 3D printer. The results were accomplished for symmetrical 1 × 2 and 1 × 4 splitters, where the angle between the output arms was varied from 10 to 180°, showing good uniformity between the splitting ratios. Asymmetrical 1 × 2 splitters were also studied to achieve different splitting ratios. This was done by fixing one arm at a specific angle, while varying the other. Results were quite satisfactory, paving the way for simple and customizable manufacturing of passive optical elements.

Four wave mixing in multimode hollow core waveguides with a two-color pump for the thorium nuclear clock

Four wave mixing in multimode hollow core waveguides with a two-color pump for the thorium nuclear clock

Radioluminescence Response of Ce-, Cu-, and Gd-Doped Silica Glasses for Dosimetry of Pulsed Electron Beams.

Radiation-induced emission of doped sol-gel silica glass samples was investigated under a pulsed 20-MeV electron beam. The studied samples were drawn rods doped with cerium, copper, or gadolinium ions, which were connected to multimode pure-silica core fibers to transport the induced luminescence from the irradiation area to a signal readout system. The luminescence pulses in the samples induced by the electron bunches were studied as a function of deposited dose per electron bunch. All the investigated samples were found to have a linear response in terms of luminescence as a function of electron bunch sizes between Gy/bunch and Gy/bunch. The presented results show that these types of doped silica rods can be used for monitoring a pulsed electron beam, as well as to evaluate the dose deposited by the individual electron bunches. The electron accelerator used in the experiment was a medical type used for radiation therapy treatments, and these silica rod samples show high potential for dosimetry in radiotherapy contexts.

Multimodal intervention improves core symptoms in preschool children with attention-deficit/hyperactivity disorder

I tested the effect of a psychobehavioral intervention combined with electroencephalographic (EEG) biofeedback on the core symptoms of preschool children with attention-deficit/hyperactivity disorder (ADHD). Participants were 42 preschool children with attention-deficit, hyperactive-impulsive, or compound-type ADHD. They were randomly divided into the control group, a psychobehavioral intervention group, an EEG biofeedback intervention group, or a psychobehavioral + EEG biofeedback intervention group (i. e., comprehensive). After 4 months of intervention, I assessed (a) attention concentration time and (b) impulsivity and hyperactivity scores using Conners Parent Symptom Questionnaire. Results show that the multimodal intervention significantly improved participants' concentration time and behavioral hyperactive-impulsive symptoms. The multimodal (vs. single-modal) intervention was more effective in improving core symptoms. My results provide a reference for related research and practical application.

Large core multimode fiber with high bandwidth and high connector tolerance for broadband short distance communications

We propose a large core multimode fiber with 100-µm core diameter for short distance communication that is compatible with existing transceivers designed for 50-µm diameter core multimode fibers. The fiber exhibits a bandwidth that is over four times higher than the 50-µm OM4 fiber, low bending loss, and large connector offset tolerance. We have studied the bandwidth capability through both detailed modeling and experiments. A prototype fiber was fabricated, and it achieves 24 GHz km peak modal bandwidth in the 850 nm window, and the wavelength window with bandwidth above 5 GHz km is more than 100 nm. The bending losses of the fiber measured at 850 and 1300 nm with an encircled flux launch condition exceed the requirements for bending insensitive multimode fibers. The fiber has much higher connector offset tolerance compared to conventional 50-µm diameter core fibers as has been exhibited by modeling and experimental study. The additional loss caused by up to 10-µm connector offset is only 0.3 dB. Transmission experiments using 25 G SR and 100 G shortwave wavelength division multiplexing transceivers over such a fiber show error-free performance over 500 and 300 m, respectively. The proposed large core multimode fiber can address versatile needs in short distance communication including the bandwidth for high data rate transmission and a wide wavelength window for wavelength multiplexed transmission. The large connector tolerance and low bending loss can also enable low cost, compact connectivity solutions with passive alignment and ease of handling.

Ammonia Gas Sensor Based on Graphene Oxide-Coated Mach-Zehnder Interferometer with Hybrid Fiber Structure.

A graphene oxide-coated in-fiber Mach-Zehnder interferometer (MZI) formed with a multimode fiber-thin core fiber-multimode fiber (MMF-TCF-MMF) is proposed and experimentally demonstrated for ammonia gas (NH3) sensing. The MZI structure is composed of two segments of MMF of length 2 mm, with a flame-tapered TCF between them as the sensing arm. The MMFs act as mode couplers to split and recombine light owing to the core diameter mismatch with the other fibers. A tapered TCF is formed by the flame melting taper method, resulting in evanescent wave leakage. A layer of graphene oxide (GO) is applied to the tapered region of the TCF to achieve gas adsorption. The sensor operates on the principle of changing the effective refractive index of the cladding mode of a fiber through changing the conductivity of the GO coating by adsorbed NH3 molecules, which gives rise to a phase shift and shows as the resonant dip shifts in the transmission spectrum. So the concentration of the ammonia gas can be obtained by measuring the dip shift. A wavelength-shift sensitivity of 4.97 pm/ppm with a linear fit coefficient of 98.9% is achieved for ammonia gas concentrations in the range of 0 to 151 ppm. In addition, we performed a repetitive dynamic response test on the sensor by charging/releasing NH3 at concentration of 200 ppm and a relative humidity test in a relative humidity range of 35% to 70%, which demonstrates the reusability and stability of the sensor.

Optimal SMF packing in photonic lanterns: comparing theoretical topology to practical packing arrangements

Photonic lanterns (PLs) rely on a close packed arrangement of single-mode fibers (SMFs), which are tapered and fused into one multimode core. Topologically optimal circle packing arrangements have been well studied. Using this, we fabricate PLs with 19 and 37 SMFs showing tightly packed, ordered arrangements with packing densities of 95% and 99% of theoretically achievable values, with mean adjacent core separations of 1.03 and 1.08 fiber diameters, respectively. We demonstrate that topological circle packing data is a good predictor for optimal PL parameters.

Radiation Effects on Pure-Silica Multimode Optical Fibers in the Visible and Near-Infrared Domains: Influence of OH Groups

Signal transmission over optical fibers in the ultraviolet to near-infrared domains remains very challenging due to their high intrinsic losses. In radiation-rich environments, this is made even more difficult due to the radiation-induced attenuation (RIA) phenomenon. We investigated here how the number of hydroxyl groups (OH) present in multi-mode (MM) pure-silica core (PSC) optical fibers influences the RIA levels and kinetics. For this, we tested three different fiber samples: one “wet”, one “dry” and one with an intermediate “medium” OH content. The RIA of the three samples was measured in the 400–900 nm (~3 eV to ~1.4 eV) spectral range during and after an X-ray irradiation at a dose rate of 6 Gy(SiO2) s−1 up to a total accumulated dose of 300 kGy(SiO2). Furthermore, we evaluated the H2-pre-loading efficiency in the medium OH sample to permanently improve both its intrinsic losses and radiation response in the visible domain. Finally, the spectral decomposition of the various RIA responses allows us to better understand the basic mechanisms related to the point defects causing the excess of optical losses. Particularly, it reveals the relationship between the initial OH groups content and the generation of non-bridging oxygen hole centers (NBOHCs). Moreover, the presence of hydroxyl groups also affects the contribution from other intrinsic defects such as the self-trapped holes (STHs) to the RIA in this spectral domain.

Dynamic Characteristics of Accelerator-Driven Subcritical Reactor With Self-Adapting Multi-Mode Core Few-Group Constants

In this study, the dynamic characteristics of accelerator-driven subcritical reactor (ADSR) under beam transients with high heterogeneity of neutron flux in time-space are investigated. Multi-mode core few-group constants are generated by three kinds of neutron fluxes: steady state of ADSR, λ-eigenvalue fundamental wave, and α-eigenvalue fundamental wave. The proposed few-group constants overcome the limitation of single few-group constant generated by two-step method that cannot consider the variation in neutron flux density and neutron energy spectrum with time and space. Compared to the existing few-group constants generated by two-step method under different operating conditions, the self-adapting multi-mode core few-group constants exhibit higher accuracy in the case of following two modes: steady-state mode of ADSR in the starting process and λ-eigenvalue mode in the beam trip condition. Overall, this research provides useful insights on neutron kinetics and can boost the development of ADSRs.

Programmable phase-change metasurfaces on waveguides for multimode photonic convolutional neural network

Neuromorphic photonics has recently emerged as a promising hardware accelerator, with significant potential speed and energy advantages over digital electronics for machine learning algorithms, such as neural networks of various types. Integrated photonic networks are particularly powerful in performing analog computing of matrix-vector multiplication (MVM) as they afford unparalleled speed and bandwidth density for data transmission. Incorporating nonvolatile phase-change materials in integrated photonic devices enables indispensable programming and in-memory computing capabilities for on-chip optical computing. Here, we demonstrate a multimode photonic computing core consisting of an array of programable mode converters based on on-waveguide metasurfaces made of phase-change materials. The programmable converters utilize the refractive index change of the phase-change material Ge2Sb2Te5 during phase transition to control the waveguide spatial modes with a very high precision of up to 64 levels in modal contrast. This contrast is used to represent the matrix elements, with 6-bit resolution and both positive and negative values, to perform MVM computation in neural network algorithms. We demonstrate a prototypical optical convolutional neural network that can perform image processing and recognition tasks with high accuracy. With a broad operation bandwidth and a compact device footprint, the demonstrated multimode photonic core is promising toward large-scale photonic neural networks with ultrahigh computation throughputs.

Mode conversion based on tilted-few-mode fiber assisted by dual arc waveguide for mode-division multiplexing system

In this paper, mode conversion based on tilted few-mode fiber assisted by the dual arc waveguide is reported. A multilayer core multimode fiber (MC-MMF) is used to model the device due to their low bending loss, high precession in mode confinement and ease of fabrication during manufacturing. In this report, an optimized 12°-tilted MC-MMF was used at the device input to provide perfect alignments with the arc waveguides and minimize radiation loss. A horizontal fiber of the same properties is connected at the output to collect the converted mode. This was achieved by making proper alignment between the core layers of the two fibers and the arc bends. Mode conversions of LP11-LP01, LP02-LP11, and LP21-LP01 were achieved with the conversion efficiency of 89.6 %, 91.2 %, and 94.34 %, respectively. The proposed conversion device indicates potential application in mode-division multiplexing communication.

Building a robust and scalable lentiviral vector purification platform

Background & Aim Lentiviral vectors (LVV) are common vehicles of genetic delivery for cell and gene therapies. LVV commercial manufacturing is costly and downstream processing (DSP) is a primary driver for the high costs due to challenges in maintaining viral infectivity. Additionally, these processes are not standardized across the industry and have poor process definition, resulting in large batch-to-batch variability, limited robustness, performance, and scalability. In collaboration with CCRM, the GE Fast Trak Centre for Advanced Therapeutic Cell Technologies (CATCT) has developed a DSP platform that can process LVV from multiple upstream systems; suspension and serum-free cultures from both stable producer and transient-transfection modalities. The different characteristics of these systems (transient vs. inducible, cell viability and density at harvest, amount of host cell contaminants, etc.) showcase the compatibility of our process with various upstream sources. Our semi-closed, single-use, single-day, room temperature LVV purification process yields infectious recoveries and contaminant clearances that are on par with current industry standards, while maintaining robustness and scalability. Methods, Results & Conclusion The final full process consists of nucleic acid digestion inside the bioreactor, clarification using filtration, ultrafiltration and diafiltration using tangential flow filtration, chromatography with multi-modal Capto™ Core 700, an optional secondary concentration, and finally 0.2 µm sterile filtration. Overall infectious titre recoveries and final concentrations of 13.7% ± 6.2% and 5.2E7 TU/mL (stable) and 30.8% ± 2.4% and 1.4E8 TU/mL (transient) have been achieved, with a ≥ 2-log removal of host cell protein and DNA in both. Additionally, a 25 L pilot run was completed with similar results, demonstrating the scalability of the process. Supported by continual gains of process knowledge and understanding, we have built a robust, consistent, and scalable LVV purification platform.

A fiber modal adapter for upgrading 850 nm multimode fiber links to 1310 nm single-mode transmission

Abstract We propose a simple and compact adapter using specially designed modal conditioning single-mode fiber for fundamental mode transmission through multimode fiber. The modal conditioning single-mode fiber has a mode field diameter at 1310 nm roughly matching that of the fundamental mode of the 50-μm core multimode fibers. The fiber is designed for integration in a compact adapter due to its low fiber cutoff wavelength. The adapters are attached to both the input and output ends of the multimode fiber to form a link suitable for single-mode transmission. The detailed characteristics of the link such as insertion loss and multi-path interference are measured. Using the adapters, we demonstrate error-free transmission over 1-km multimode fiber using a 100G CWDM4 transceiver, which carries 4 × 25 Gb/s transmission at four wavelengths around 1310 nm. The proposed SMF adapter not only enables newly deployed multimode fiber to be future proof for higher data rate SM transmission, but also offers an upgrade solution for legacy OM2 installations which otherwise cannot support higher data rate and in some cases are very costly to replace.

Deep learning parallel computing and evaluation for embedded system clustering architecture processor

In the era of intelligence, the processing of a large amount of information and various intelligent applications need to rely on embedded devices. This trend has made machine learning algorithms play an increasingly important role. High-performance embedded computing is an effective means to solve the lack of computing power of embedded devices. Aiming at the problem that the calculation amount of new intelligent embedded applications based on machine learning technology is higher, the computing power of traditional embedded systems is difficult to meet their needs, this paper studies the parallel optimization and implementation techniques of convolutional neural networks in Parallella platform. The parallel optimization strategy of convolutional neural network on the clustering architecture processor of heterogeneous multi-core system is given. Then the high-performance implementation of convolutional neural network on Parallella platform is studied, and the function of convolutional neural network system is implemented. A set of performance evaluation methods for embedded parallel processors is proposed. From the application point of S698P, the eCos operating system is selected as the platform. The single-core mode and multi-core mode are compared on the simulator GRSIM, and the parallel performance evaluation is given. Experiments have shown that the efficiency of deep learning tasks is significantly improved compared to traditional parallel methods.

Effects of pore structure on surfactant/polymer flooding-based enhanced oil recovery in conglomerate reservoirs

To understand the displacement characteristics and remaining oil displacement process by the surfactant/polymer (SP) flooding in cores with different pore structures, the effects of pore structure on the enhanced oil recovery of SP flooding was investigated at the pore, core and field scales through conducting experiments on natural core samples with three typical types of pore structures. First, the in-situ nuclear magnetic resonance core flooding test was carried out to capture the remaining oil variation features in the water flooding and SP flooding through these three types of cores. Subsequently, at the core scale, displacement characteristics and performances of water flooding and SP flooding in these three types of cores were evaluated based on the full-size core flooding tests. Finally, at the field scale, production characteristics of SP flooding in the bimodal sandstone reservoir and multimodal conglomerate reservoir were compared using the actual field production data. The results show: as the pore structure gets more and more complex, the water flooding performance gets poorer, but the incremental recovery factor by SP flooding gets higher; the SP flooding can enhance the producing degree of oil in 1–3 μm pores in the unimodal and bimodal core samples, while it produces largely oil in medium and large pores more than 3 μm in pore radius in the multimodal core sample. The core flooding test using full-size core sample demonstrates that the injection of SP solution can significantly raise up the displacement pressure of the multimodal core sample, and greatly enhance recovery factor by emulsifying the remaining oil and enlarging swept volume. Compared with the sandstone reservoir, the multimodal conglomerate reservoir is more prone to channeling. With proper profile control treatments to efficiently enlarge the microscopic and macroscopic swept volumes, SP flooding in the conglomerate reservoir can contribute to lower water cuts and longer effective durations.

Ultrahigh temperature and strain hybrid integrated sensor system based on Raman and femtosecond FBG inscription in a multimode gold-coated fiber.

In this paper, a novel approach for hybrid systems combining Raman distributed sensors with fiber Bragg grating (FBG) sensors to carry out distributed and quasi-distributed temperature/strain measurements was proposed and experimentally demonstrated. Three FBGs were inscribed by the point-by-point technique in a simple setup for type I femtosecond inscription in a pure silica core multimode gold-coated fiber. Employing a single fiber, temperatures up to 600 °C and strains up to 4144 μɛ approximately were measured simultaneously and without interferences between both distributed and point measurements. Moreover, a new calibration technique was implemented to calibrate the distributed temperature system using the FBG measurements as reference.

Study of crystalline defect induced optical scattering loss inside photonic waveguides in UV-visible spectral wavelengths using volume current method.

In this work, we study the crystalline defect induced optical scattering loss inside photonic waveguide. Volume current method is implemented with a close form of dyadic Green's function derived. More specifically, threading dislocation induced scattering loss inside AlN waveguides in UV-visible spectrum wavelengths are studied since this material is intrinsically accompanied with high densities of dislocations (typically on order of 108-1010cm-2). The results from this study reveal that threading dislocations contribute significant amount of scattering loss when material is not MOCVD grown. Additionally, the scattering loss is strongly dependent on polarization and waveguide geometries: TM modes exhibit higher scattering loss compared with TE modes, and the multimode large core waveguides are more susceptible to threading dislocations compared with single mode waveguides and high-aspect-ratio waveguides. Conclusions from this work can be supported by several recently published investigations on III-N based photonic devices. The model derived from this work can also be easily altered to fit other material systems with other types of crystalline defects.