Low Attenuation Loss Research Articles

Residual dispersion compensation photonic crystal fiber based on simulated annealing algorithm and Livelink data interaction

An octagonal photonic crystal fiber (O-PCF) structure with equal air hole diameter of the cladding is proposed for residual dispersion compensation, and a high refractive index material SF57 is introduced in the core region to make it have the advantages of high negative dispersion, low attenuation loss, low fabrication difficulty. Due to the symmetric structure, no additional polarization control is required in the dispersion compensation process, which further reduces the production cost. Using Livelink data interaction not only accelerates the modeling of O-PCF, but also enables the effective refractive index of HE11 to be unattended continuously searched. Furthermore, simulated annealing algorithm is used to reverse design the structural parameters of cladding air hole diameter and central solid hole diameter. The results show that, based on the simulated annealing algorithm interacting with Livelink data, the optimize efficiency, design accuracy and dispersion characteristics are improved. The ultra-flat high negative dispersion O-PCF can be reverse designed in the S + C + L and S + C + L + U bands which shows the average dispersion of −847.34 ps/(nm·km) and −752.90 ps/(nm·km) with the absolute dispersion of only ±7.25 ps/(nm·km) and ±10.28 ps/(nm·km), respectively. The designed RDCF is tolerant to ±1% and ±2% variation of the central solid hole diameter and the cladding air hole diameter during fabrication, respectively. The combination of simulated annealing algorithm and Livelink data interaction provides an efficient method for reverse design of PCF.

A Novel Chirped Bragg Grating Based Spectral Domain Delay Generator

Light dispersion and chirping of spectral lines of a broadband light source is major issue with spectral domain optical coherence tomography. We designed a novel spectral delay line using multimode interference coupler and chirp Bragg grating. We considered the waveguide material as S-1813 polymer. Light from the broad-band light source is first dispersed then delayed in time. The bunches of delayed spectra produce chirping. The design ensures that the bandwidth of each bunch is about 30nm linewidth at a central wavelength of 1.55µm, corresponding to a coherence length of 15µm. The design is optimized for maximum dispersion with (i) minimum possible number of Bragg gratings and (ii) low attenuation and radiative losses. Tolerance measurements for differential refractive index also reported.

Bend losses in flexible polyurethane antiresonant terahertz waveguides.

One important shortcoming of terahertz technology is the relative absence of convenient, flexible, and reconfigurable waveguides with low attenuation and small bend losses. While recent years have been marked by remarkable progress in lowering the impact of material losses using hollow-core guidance, such waveguides often have centimeter-scale diameter and are therefore not flexible. Here we experimentally and numerically investigate antiresonant dielectric waveguides made of thermoplastic polyurethane, a commonly used dielectric with a low Young's modulus. The hollow-core nature of antiresonant fibers leads to low transmission losses using simple structures, whereas the low Young's modulus of polyurethane makes them extremely flexible. The structures presented enable millimeter-wave manipulation in the same spirit as conventional (visible- and near-IR-) optical fibers, i.e. conveniently and reconfigurably, despite their centimeter-thick diameter. We investigate two canonical antiresonant geometries formed by one- and six-tubes, experimentally comparing their transmission, bend losses and mode profiles. The waveguides under investigation have loss below 1 dB/cm in their sub-THz transmission bands, increasing by 1 dB/cm for a bend radius of about 10 cm. We find that the six-tube waveguide outperforms its one-tube counterpart for smaller bend radii (here: 10cm); for larger bend radii, coupling to cladding tube modes can lead to a drop in transmission at specific frequencies in the six-tube waveguide that does not occur in the one-tube waveguide.

Dielectric Resonator Negative Group Delay Circuit

AbstractThis study investigates an innovative theory on design of dielectric resonator (DR) based negative group delay (NGD) microwave circuit. The NGD circuit is mainly constituted by a cylindrical bulk of DR as a coupling element with a microstrip line. The developed theory is analytically established from the S‐parameters modeling of this innovative DR NGD topology. The NGD analysis and synthesis equations are formulated by considering the key parameters of the DR NGD cell. The NGD existence condition as a function of the DR and microstrip line parameters is also introduced. The behavioral response of the bandpass NGD function is verified with different designed proof‐of‐concepts (POCs). The developed NGD DR topology was validated with original circuit design by commercial simulations and experimentations with insertion and reflection losses lower than 4 and 10 dB, respectively. The POC prototypes operate with low attenuation losses in mono band and dual bands up to 10 GHz. Single NGD cells with DR coupled with “I” and “U” shape microstrip lines operating at different central frequencies were designed and implemented. Then, dual‐band NGD circuits operating at approximately 2.5 and 5 GHz were also tested. The possibility to widen the NGD bandwidth with double DR NGD circuits was investigated.

Simulation-Based Optical Threshold Component Design for Mitigating Four-Wave Mixing Effects in WDM Radio Over Fiber Systems

AbstractThe gigantic demand on high bandwidth and capacity has triggered the need to use the radio over optical fiber (RoF) systems. RoF systems offer several attractive features such as low attenuation loss, large bandwidth, less interference, etc., which can improve the communication system reliability and achieve high data rates. However, the RoF system suffers from linear and nonlinear fiber impairments, which result in signal distortion. Several solutions have been proposed to overcome linear impairments; on the other hand, the nonlinear impairments issue is still a challenging problem in RoF communication systems. Four-wave mixing (FWM) is the most dominating nonlinear impairments that impacts the performance of optical fiber communication systems and the RoF systems as well. In this article, we present a strategy to mitigate the FWM effect in wavelength division multiplexing (WDM) RoF systems. Specifically, we study the effect of FWM under high transmit power levels over long transmission distances. This proposed strategy aligns the optical and radio link parameters to alleviate the FWM effects. To achieve this objective, the impact of WDM RoF system parameters such as wavelength ($\lambda_i$), transmitted power, etc., on system performance is investigated. The main performance metrics are the total signal-to-noise ratio (SNR), optical SNR (OSNR), Q-factor, and bit error rate (BER). Given these metrics, our proposed strategy defines an optical threshold level that applies to the optical threshold component to get rid of the undesired signals generated by the FWM effect.

Implementing IoT in Underwater Communication using Li-Fi

Internet of Things (IoT) is attracting more research interest as a result of increased interaction of human with underwater world. IoT technology using Light fidelity (Li-Fi) module plays a vital role in Environmental monitoring, underwater exploration, underwater Disaster management and underwater military Applications. In this paper, we implement IoT in underwater communication using Li-Fi module. However Implementing Li-Fi module in underwater pose grand challenges due to the unique features of underwater channel and acoustic systems. We comprehensively investigate these unique features and finally possible solutions are provided. Simulations are done using MATLAB software to find which color of light emitting diode (LED) is suitable for underwater Communication. It is found that Blue – Cyan-Green Spectral range of wavelength 490nm to 560nm is suitable for underwater communication. We obtain low absorption, scattering and attenuation loss in the Blue – CyanGreen Spectral range. An application was developed for the fisherman to identify number and variety of fishes available in particular location.

Function of second cladding layer in hollow core tube lattice fibers

Modes attenuation of the tube lattice fiber (TLF) is characterized by D/λ, where D is the core diameter and λ is the wavelength. Hence, the TLF is structured with a large core to ensure a low attenuation loss. A small core, on the other hand, facilitates the gas-filled TLF applications, but at the expense of the increased mode attenuation. We show that adding a second cladding layer to the conventional one layer TLF (1TLF) can resolve the contradicting requirements. The mode attenuation of TLF with two cladding layers (2TLF) is less influenced by the D/λ value as compared to 1TLF, thus realizing a low loss small core TLF. Furthermore, we found that adding the second layer brings another advantage to a bending performance. With a determined core size, D, a 1TLF with smaller capillary hole size, d, experiences less bending loss. However, the reduced d increases the confinement loss that counteracts the bending loss improvement. This confliction is substantially alleviated in 2TLF thanks to the second cladding layer. Theoretical investigations and experimental demonstrations are presented to evidence the important role of the second cladding ring in the TLF, which has been overlooked in prior studies.

Experimental investigation on mass flow rate measurements using fibre Bragg grating sensors

Flow measurement and control of cryogens is one of the major requirements of systems such as superconductor magnets for fusion reactors, MRI magnets etc. They can act as an early diagnostic tool for detection of any faults and ensure correct distribution of cooling load while also accessing thermal performance of the devices. Fibre Bragg Grating (FBG) sensors provide compact and accurate measurement systems which have added advantages such as immunity towards electrical and magnetic interference, low attenuation losses and remote sensing. This paper summarizes the initial experimental investigations and calibration of a novel FBG based mass flow meter. This design utilizes the viscous drag due to the flow to induce a bending strain on the fibre. The strain experienced by the fibre will be proportional to the flowrate and can be measured in terms of Bragg wavelength shift. The flowmeter is initially tested at atmospheric conditions using helium. The results are summarized and the performance parameters of the sensor are estimated. The results were also compared to a numerical model and further results for liquid helium is also reported. An overall sensitivity of 29 pm.(g.s-1)-1 was obtained for a helium flow, with a resolution of 0.2 g.s-1. A hysteresis error of 8 pm was also observed during load-unload cycles. The sensor is suitable for further tests using cryogens.

A long-range hybrid THz plasmonic waveguide with low attenuation loss

Numerical solutions are obtained for the proposed novel hybrid terahertz plasmonic waveguide structure, namely the silicon metal silicon (SMS) waveguide. It is shown that the SMS waveguide can overcome the diffraction limit while still maintaining a sizeable propagation length. The geometric dependence of the mode characteristics of this structure is analyzed in detail, showing strong confinement and low loss with propagation lengths exceeding 14mm at normalized mode areas of 1.72×10−2. By using the FEM method (Comsol), the guiding properties of the hybrid terahertz surface plasmon polariton (HTSPP) waveguide are numerically analyzed at the THz frequency, and a combination of double-structured comparisons of the best features of the terahertz plasmonic waveguide is made. Depending on the height used and how the mode confinement is measured, various modal designs, such as double microwire structures, are developed. The structures indicate that we verified the possibility of low attenuation loss of hybrid THz plasmonics propagation. The effective mode area Aeff, energy distribution, and propagation length Lp versus height for waveguides with Si microwire and SiO2 are shown. The numerical calculation results reveal a potential for use in applications such as optical force in trapping and transporting biomolecules, and in high-density integrated circuits.

Novel biocompatible and resorbable UV-transparent phosphate glass based optical fiber

In this paper the first glass based resorbable optical fiber is manufactured and characterized, showing values of attenuation loss from one to two orders of magnitude lower than the polymeric based bioresorbable devices reported in literature. The fiber behaves as a single-mode waveguide at the lower limit of the first biological window (1300 nm) and as a multi-mode waveguide in the visible region (630 nm). Highly transparent calcium-phosphate glasses (PGs) are proposed as a new class of materials for biomedical optics, managing to combine for the first time in a vitreous material solubility in aqueous media, transparency in the near UV region, low intrinsic attenuation loss and thermal stability during fiber drawing. In-vitro tests in physiological conditions show dissolution kinetics of glass fibers in about a month.

Review Compact Microwave Filter for Harmonic Rejection

An investigation of the several different techniques and method have been suggested in the design of compact microwave filters for the realization of high performance output micromachined microstrip low pass filters and highest attenuation loss is presented in this paper. It is shown that the basis for much fundamental microwave filter theory lies in the real of lumped-element filters, which lumped elements suffers for not suitable use in high frequency, because wavelength will decrease to short and the only distributed elements can practically well and the lumped elements circuit and work efficiently at low frequency or vice versa wavelength of distributed elements become too larger. In this paper, a review of numerous methods of design compact microstrip filters that have been offered over the last years is proposed, including a discussion of topologies and the structures used to make compactness size of microwave filters.

SC-type multi-core optical-fiber connectors using a pressurization spring

Prototype standard-connector (SC)-type physical-contact connectors were designed and fabricated for a seven-core fiber. The ferrule in the connector has a capillary inserted into a pipe, which fits into a flange with freedom to slide. After the capillary (with the seven-core fiber) and the flange are aligned and adhered, a pressurization spring is used to press fit the flange to a plug frame in a housing. Several prototype connectors have been used to achieve a low attenuation (less than 0.5 dB) and high return loss (40 dB or more). These coupling characteristics indicate that these SC-type physical-contact connectors will be one of the key devices for achieving space division multiplexing (SDM).

Efficient four-wave mixing in an ultra-highly nonlinear suspended-core chalcogenide As_38Se_62 fiber

We report a chalcogenide suspended-core fiber with ultra-high nonlinearity and low attenuation loss. The glass composition is As(38)Se(62).With a core diameter as small as 1.13 µm, a record Kerr nonlinearity of 46,000 W(-1) km(-1) is demonstrated with attenuation loss of 0.9 dB/m. Four-wave mixing is experimented by using a 1m-long chalcogenide fiber for 10 GHz and 42.7 GHz signals. Four-wave mixing efficiencies of -5.6 dB at 10 GHz and -17.5 dB at 42.7 GHz are obtained. We also observed higher orders of four-wave mixing for both repetition rates.

Investigation on multi-core fibers with large Aeff and low micro bending loss

To realize large effective area (Aeff) multi-core fibers (MCFs), the design to suppress the cross-talk and the influence of the cladding diameter on the micro bending loss were investigated. As a result, the MCFs with large Aeff over 100 μm(2) and low micro bending loss were successfully fabricated. The results indicate the importance of fiber design to realize large Aeff MCFs including fiber diameters, which largely affect the micro bending loss property. Additionally, MCF with large Aeff, low attenuation loss and suppressed cross-talk was successfully realized by optimizing the fiber design. The cross-talk properties could be estimated by the simulation based on the coupling power theory taking the influences of the longitudinal fluctuation of core diameter into account.

Experimental study of an elliptical-core photonic bandgap fiber with thin core wall and high aspect ratio and its birefringence characteristics

We fabricate an elliptical hollow-core photonic bandgap fiber (EC-PBGF) with a core-wall thickness of 65 nm and an aspect ratio of 1.4. The core is expanded by applying positive pressure in the hollow-core region during the fiber-drawing process. Both the reduction of core-wall thickness and the increase of aspect ratio result in the enhancement of optical properties in terms of a low attenuation loss and group birefringence. The minimum loss and group birefringence of the fabricated EC-PBGF2 are measured to be 0.1 dB/m and 0.012, respectively.

Seven-core multicore fiber transmissions for passive optical network

We design and fabricate a novel multicore fiber (MCF), with seven cores arranged in a hexagonal array. The fiber properties of MCF including low crosstalk, attenuation and splice loss are described. A new tapered MCF connector (TMC), showing ultra-low crosstalk and losses, is also designed and fabricated for coupling the individual signals in-and-out of the MCF. We further propose a novel network configuration using parallel transmissions with the MCF and TMC for passive optical network (PON). To the best of our knowledge, we demonstrate the first bi-directional parallel transmissions of 1310 nm and 1490 nm signals over 11.3-km of seven-core MCF with 64-way splitter for PON.

Structure and properties of Ti4+-ureasil organic-inorganic hybrids

Hybrid planar waveguides were prepared from Ti4+-acetylacetone (acac)-Ureasil sols deposited on glass substrates. Structural features have been investigated by spectroscopic measurements (Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Raman scattering) and Small Angle X-ray Scattering (SAXS). Addition of Ti4+-acac to the ureasil (Ti:Si molar ratio 1:1) leads to the formation of bonds between the Ti complex and the siloxane groups, whereas further addition of Ti4+ (Ti:Si molar ratio 5:1) leads to the additional formation of titanium-rich nanoclusters. The optical parameters of the waveguides such as refractive index, thickness, propagating modes and attenuation coefficient were measured at 632.8, 543.5 and 1550 nm by the prism coupling technique. The refractive index can be tuned by the Ti4+ relative content. The few microns thick planar waveguides support well confined propagating modes with low attenuation loss for all compositions.

Magnetooptic effects in surface-plasmon-polaritons slab waveguides

This paper analyzes the magnetooptic (MO) effects in surface plasmon polaritons (SPP) propagating in thin metallic layers as a function of the metal thickness. Two different configurations are analyzed: a ferromagnetic metal surrounded by nonmagnetic dielectrics and a nonmagnetic metal bounded by ferromagnetic dielectrics. Depending on the configuration and the thickness of the metallic layer, waveguides with very low attenuation losses and high MO effects can be obtained. These configurations could be used to design MO active devices in SPP-based optics.

Effects of the Weak Absorption Tail on the Transmission Loss of Ge-Sb-Se Optical Fibers

Selenide glass optical fibers were fabricated for Ge30Sb10Se58S2 and Ge20Sb10Se70 glasses. Their transmission loss has been measured and compared with the theoretical attenuation loss that was calculated taking into account the electronic transition absorption, Rayleigh scattering, and multiphonon absorption. A low attenuation loss of the Ge20Sb10Se70 glass composition in 1.2–1.7 μm range has been expected due to its high optical band gap energy compared with the Ge30Sb10Se58S2 glass. However, the measured attenuation loss of the Ge30Sb10Se58S2 glass fiber was ∼13 dB/m at 1.5 μm while Ge20Sb10Se70 glass showed ∼82 dB/m. An enhanced weak absorption tail due to the localized states of the Ge20Sb10Se70 glass was responsible for this behavior. Structural defects are related to the localized states and discussed for the present glass compositions.

Optical Properties of Perfluorocyclobutane Aryl Ether Polymers for Polymer Photonic Devices

New thermoplastic PFCB aryl ether monomers, 1,5-bis(trifluorovinyloxy)naphthalene (TFVON) and 1,4-bis(trifluorovinyloxy)benzene (TFVOB), were synthesized, and homopolymers, PTFVON and PTFVOB, and a copolymer, TFVON-co-TFVOB, were successfully prepared from them by 2π + 2π cyclopolymerization. The C−H vibrational absorption of the monomer was investigated by IR and near-IR spectrum analysis. The optical properties of the polymers in the form of plastic optical fibers and thin films were examined. The absorptions corresponding to fundamental and overtones of C−H vibrations in PFCB monomers were greatly reduced due to the presence of the fluorine substituents, which could lead to low attenuation loss of the resulting polymers in the near-IR region. Polymerization conditions such as temperature and time significantly affected the optical loss values of the polymers as well as their molecular weights and thermal properties. We prepared plastic optical fibers of the PFCB polymers, and optical windows were obser...