Ring Filter Research Articles

A New Class of Highly-Miniaturized Reconfigurable UWB Filters for Multi-Band Multi-Standard Transceiver Architectures

Modern wireless communication systems typically employ multiple frequency bands for several standards. A new class of miniaturized ring filters with tuning capability is introduced for this purpose. The proposed filter structure is based on a single multi-mode resonator with variable section impedances in microstrip technology. The bandwidth of the filter can be significantly extended to cover the whole ultra wideband (UWB) frequency range with high adjustability. Moreover, a tunable bandnotch is introduced within the filter response, which can be arbitrarily placed according to the required application. Varactor and PIN diodes are also utilized to facilitate a high tuning capability throughout the different filter characteristics with respect to bandwidth, center frequency, and bandnotch frequency. Based on the symmetry of the filter, even-odd mode analysis is applied to investigate the different filter design characteristics. In addition, a comprehensive transmission line model is investigated within this paper which showed excellent agreements with full-wave simulations and measurements. The implemented UWB filter is investigated with respect to its frequency-domain characteristics and group delay response. The realized filter has a fractional bandwidth of more than 119% with a low group delay. All measured results are in a very good agreement with analysis and simulations. The overall filter dimensions, including housing, do not exceed 25 mm $\times 25$ mm.

Design of dual ring wavelength filters for WDM applications

Wavelength division multiplexing plays a prime role in an optical communication due to its advantages such as easy network expansion, longer span lengths etc. In this work, photonic crystal based filters with the dual rings are proposed which act as band pass filters (BPF) and channel drop filter (CDF) that has found a massive applications in C and L-bands used for wavelength selection and noise filtering at erbium doped fiber amplifiers and dense wavelength division multiplexing operation. These filters are formulated on the square lattice with crystal rods of silicon material of refractive index 3.4 which are perforated on an air of refractive index 1. Dual ring double filters (band pass filter and channel drop filter) on single layout possess passing and dropping band of wavelengths in two distinct arrangements with entire band quality factors of 92.09523 & 505.263 and 124.85019 & 456.8633 for the pass and drop filters of initial setup and amended setup respectively. These filters have the high-quality factor with broad and narrow bandwidths of 16.8nm & 3.04nm and 12.85nm & 3.3927nm. Transmission spectra and band gap of the desired filters is analyzed using Optiwave software suite. Two dual ring filters incorporated on a single layout comprises the size of 15×11μm which can also be used in the integrated photonic chips for the ultra-compact unification of devices.

Localized in situ cladding annealing for post-fabrication trimming of silicon photonic integrated circuits.

We report the use of localized annealing via in situ heaters to induce a semi-permanent change in the refractive index of the cladding in ring resonator filters. When compared to other methods for post-fabrication trimming, this method has the advantage that no additional equipment, other than a supply of electrical power, is necessary to cause the index change. Two cladding materials were used: hydrogen silsesquioxane (HSQ) for samples that were externally annealed, and PECVD oxide for samples that were annealed with in situ heaters. The resonant wavelengths could be adjusted by as much as 3.0 nm and 1.7 nm for the HSQ and PECVD cladded filters, respectively. The trimming of a 5 channel, single ring filter bank, and a single, double ring filter is demonstrated.

Dual-tunable multiferroic active ring filter for microwave photonic oscillators

A theoretical model of a microwave active ring filter based on a ferrite-ferroelectric layered structure serving as a waveguide for spin-electromagnetic waves is developed. An experimental prototype of the device is fabricated and characterized. The device is implemented as an active-ring resonator with a microwave amplifier and a ferrite-ferroelectric delay line. The resonance properties of this system are studied theoretically and experimentally. The results show dual control of central frequency of the filter with magnetic and electric fields. An effective Q-factor of 50 000 and tuning by 5 MHz with an electric field are achieved at 8 GHz.

Stable and switchable single-longitudinal-mode dual-wavelength erbium-doped fiber laser based on a fiber ring filter

A switchable dual-wavelength and single-longitudinal-mode (SLM) erbium-doped fiber laser (EDFL) based on a fiber ring filter (FRF) is proposed and demonstrated through a detailed experimental verification. In the design, the simple linear-cavity EDFL is composed of one 976-nm laser diode (LD), one fiber loop mirror (FLM), two cascaded fiber Bragg gratings (FBGs), and an EDF. To improve the laser stability, the FRF is spliced into a specially designed EDFL, which is fabricated from an EDF and two couplers with splitting ratios of 50:50 and 30:70, respectively. Both single- and dual-wavelength lasers can be realized by adjusting the variable attenuator (VA) between the two FBGs. In the proposed EDFL, the 1540-nm laser and the 1545-nm laser, respectively, incur laser-frequency shifts at room temperature of less than 3 pm and 2 pm over a period of 60min. The single-wavelength 1540- and 1545-nm lasers show single-longitudinal-mode (SLM) operation within the frequency range of 0–500MHz, as measured by the delayed self-heterodyne method using a 50-km single-mode fiber, and the 3-dB linewidths of the output of two lasers are about 2.8kHz and 2.5kHz, respectively.

Ultra-compact wavelength-tunable quantum-dot laser with silicon-photonics double ring filter

Compact, wavelength-tunable light sources are desired for the enhancement of information communication technology and bio-imaging applications. We propose a compact, wavelength-tunable laser diode with a wide wavelength-tunable range around 1230 nm consisting of a quantum-dot optical amplifier and a silicon photonic tunable filter. High-quality InAs quantum dots grown with the sandwiched sub-nano separator technique were used as the optical gain medium. The wavelength-tunable filter was constructed with ring resonators fabricated using silicon photonics. The single-mode laser oscillation was demonstrated with a 28.5-nm wavelength-tunable range.

Technical and economic viability of a compact, partially submersed black water treatment system for floating residences

Riverine populations in the Amazon lack appropriate sanitation technologies due to the challenges imposed by the várzea (floodplain) environment. This compromises their health and the quality of the environment in which they live. This study aims to verify the technical and economic viability of a black water treatment using a septic tank + anaerobic filter (bamboo rings, crushed stone, brick fragments) with locally available components, of small volume and which is partially submersed. The system's pollutant removal efficiency was considered using analyses of pH, temperature, biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrogen, ammonium and phosphorus. Economic viability was calculated using the costs of the systems, compared with the value of a standard residence and family income of residents of the Mamirauá and Amanã Reserves. BOD removal efficiency was similar for the media filter tested (average 77%). COD load removal was between 67 and 83%. Nitrogen and phosphorus concentrations remained high in relation to legal standards, with 59 and 96 mg L−1 of phosphorus for the brick fragment filters, and 230 and 379 mg L−1 of nitrogen for the crushed stone and bamboo ring filters, respectively. The cost for the system was US$ 1,000, about 5% of the cost of a standard residence. The three filter configurations were similar in terms of organic material removal. The technology proved viable in terms of efficiency and cost as it is an accessible option for the várzea environment.

Microstrip Diplexer Constructed With New Types of Dual-Mode Ring Filters

-A microstrip diplexer consisting of two new types of ring filters is presented in this letter. The proposed ring filter is able to move one of transmission zeros closer to its passband corner by connecting the feeding capacitors at the different locations of the resonant ring. Thus, a diplexer implemented by connecting two kinds of ring filters with different feeding features can achieve the required isolation for the small channel separation. Then an open-stub is added at the common input port of the channel filters to achieve the required input matching at the two passbands of the diplexer. A diplexer prototype with two passbands at 1.75 GHz and 1.85 GHz with a channel separation 40 MHz was fabricated. The measured insertion losses in the pass bands are all less than 2.1 dB. The isolation between the two channels is greater than 20 dB and the input return losses of the three ports are about 20 dB.

Realce de candidatos a nódulo pulmonar en radiografías de tórax por medio de filtros de convergencia

Este artículo presenta el desarrollo de una herramienta de software para el realce de áreas sospechosas de nódulos pulmonares en radiografías de tórax. Los nódulos pulmonares son lesiones que se encuentran dentro de la regíon pulmonar y son los primeros indicadores de la presencia de un tumor cancerígeno en este órgano. En primera instancia, se implementa un método de segmentación automático. Luego, para el realce de los candidatos, se usan filtros de convergencia que evalúan el grado en el que converge el área circundante al píxel de interés, asumiendo que los posibles candidatos a nódulos presentan forma circular. En este trabajo se implementan cuatro filtros de convergencia: Moneda, Iris, Anillo Adaptativo y Banda Deslizante. Los filtros de moneda y de anillo adaptativo obtuvieron mejores resultados en cuanto a detección y número de candidatos por imagen. Al aplicar la técnica de resta contralateral junto con los filtros basados en características geométricas tales como área, redondez y excentricidad, se logró disminuir el número de candidatos.

A switchable dual-wavelength erbium-doped fiber laser based on saturable absorber and active optical fiber ring filter

A dual-wavelength erbium-doped fiber laser (EDFL) with outstanding stability is presented. In the fiber laser system, two nested active optical fiber ring filters are configured to improve the comb spectrum performance, a saturable absorber is employed to form a gain grating for both filtering and frequency stabilizing, two cascaded fiber Bragg gratings (FBGs) are utilized to achieve dual-wavelength output, and a variable attenuator is arranged to adjust output power. Experimental results illustrate that the peak wavelength drift is less than 3 pm, and a good linear relationship between output power and pump power is realized.

Stable and tunable narrow-linewidth erbium-doped fibre laser based on polarization-maintaining fibre ring filter and PM-FBG

A tunable, narrow-linewidth, ring-cavity, erbium-doped fibre laser (EDFL) incorporating a polarization-maintaining fibre ring filter (PMF-FRF) and a polarization-maintaining fibre Bragg grating (PM-FBG) was designed and used in experiments. In the proposed configuration, the PM-FBG was used as a wavelength selector and the PMF-FRF was fabricated by a 3 dB coupler and a 2 m polarization-maintaining fibre. In order to constrain the mode hopping, a 1 m long segment of erbium-doped fibre was inserted between the circulator and the PM-FBG as a saturable absorber. Based on these enhancements, the side-mode suppression was improved and a stable and tunable single-wavelength laser was achieved within the tuning scope of 1534.36–1535.07 nm by adjusting the polarization controller. In the tunable scope, each wavelength space was ≤0.1 nm, the maximum power drift was ≤0.35 dB, and the 3 dB linewidth was ≤0.15 nm. In the experiment, dual- and triple-wavelength laser emissions were also realized by modifying the polarization condition of the cavity. Over a 20 min monitoring period at room temperature, the wavelength shift and power fluctuation of the single-wavelength emission were ≤0.01 nm and 0.11 dB respectively, while wavelength shift and power fluctuation of the dual-wavelength emission of 1534.39 and 1535.07 nm were ≤0.02 nm and 0.7 dB respectively.

RGB Image Reconstruction Using Two-Separated Band Reject Filters

Noises like impulse or Gaussian noise could be easily removed and recovered in the spatial domain by applying mean or median convolution. Structural noise, like periodic has a global degradation effect. This degradation is looking like bars that cover the image. This paper developed a new approach that detect the degradation; recover it; and hence reconstruct the original color image. The two dimensions discrete Fourier Transform is applied to isolate, block, and replace some particular frequencies (degradation bands) using auto detection and recovery procedure, it applies two separated band reject filters to avoid blocking the true bands like what is resulted in Ring filter. It tries locating the periodic noise (two spikes) and the four degraded lines using a powerful searching algorithm in the frequency domain. Unlike, Ring and Notch filter, the Two-Circle method is smart enough to predict the size of the spike, so a suitable band rejected filter should be selected to replace only degraded bands with approximation values instead of zeros. The Peak Signal to Noise Ratio (PSNR) vs. periodic frequency relation is applied to find the quality of measurements of the reconstructed and cleaned colored image. So, the quality of three methods is calculated and compared. All testing results show that the two separated band reject filters method satisfied maximum dB results and minimum frequency change to the steady state values than other two methods. Normal 0 false false false EN-AU X-NONE AR-SA /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:Times New Roman; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

Reconfigurable ring filter with controllable frequency response.

Reconfigurable ring filter based on single-side-access ring topology is presented. Using capacitive tuning elements, the electrical length of the ring can be manipulated to shift the nominal center frequency to a desired position. A synthesis is developed to determine the values of the capacitive elements. To show the advantage of the synthesis, it is applied to the reconfigurable filter design using RF lumped capacitors. The concept is further explored by introducing varactor-diodes to continuously tune the center frequency of the ring filter. For demonstration, two prototypes of reconfigurable ring filters are realized using microstrip technology, simulated, and measured to validate the proposed concept. The reconfigured filter using lumped elements is successfully reconfigured from 2 GHz to 984.4 MHz and miniaturized by 71% compared to the filter directly designed at the same reconfigured frequency, while, for the filter using varactor-diodes, the frequency is chosen from 1.10 GHz to 1.38 GHz spreading over 280 MHz frequency range. Both designs are found to be compact with acceptable insertion loss and high selectivity.

Design and Analysis of Dual-Mode Double-Ring Resonator for Dual-Band Bandpass Filter Applications

In this paper, two types of miniaturized dual-mode bandpass filters (BPF), a single-ring (SR) resonator, and a double-ring (DR) resonator are developed. By applying the capacitive-coupling technique to a dual-mode ring filter, a technique is proposed to miniaturize the dual-mode double-ring filter. An adjustable dual-band bandpass filter is achieved by developing a ring resonator where the two modes are capacitively coupled. Control of the filter center frequency is determined by the diameter of the ring and by the rings annular width. Filter coupling amount can also be adjusted by disturbance (perturbation) of an open stub attached to the annular disc. Proposed filters explore both single- and double-ring architectures. A single-ring resonator acting as a dual bandpass filter to allow 3.8 GHz and 7.8 GHz single is developed. A double-ring resonator to allow 2.05 GHz and 3.9 GHz signals is also developed. The ring resonators are fabricated on RO-4003 substrate, with relative dielectric constant of 3.38, thickness of 0.8 mm, and dielectric loss tangent of 0.0025. Results indicate the filters can be applied in the communications field.

Interaction of whispering gallery modes in integrated optical microring or microdisk circuits: hybrid coupled mode theory model

Whispering gallery modes supported by open circular dielectric cavities are embedded into a nonparametric two-dimensional frequency domain hybrid coupled mode theory framework. Regular aggregates of these cavities, including straight access channels, are investigated. The model enables convenient studies of the guided wave scattering process, the response of the circuit to guided wave excitation. Transmission resonances can be characterized directly in terms of resonance frequency and linewidth by computing supermodes of the entire composite circuits, comprising both cavities and bus waveguides. Examples of single ring and disk filters, a coupled-resonator optical waveguide, and a three-cavity photonic molecule in a reflector configuration allow the approach to be assessed.

A tunable polymer waveguide ring filter fabricated with UV-based soft imprint technique

Photonic integrated components with tunability, low power consumption and low fabrication cost are of considerable interest for optical communications and optical signal processing systems. Based on the high thermo-optic coefficient of polymer material, we demonstrate a tunable integrated waveguide ring filter with a novel but very simple UV-based soft imprint technique. By properly incorporating a Mach–Zencher interferometer (MZI), the tunability of the ring filter's coupling states and resonant wavelength are realized flexibly by the micro-heaters. The tuning efficiency of resonant wavelength is 8.2pm/mW within one free spectrum range of the ring filter.

AN EFFECTIVE FRAMEWORK FOR AUTOMATIC SEGMENTATION OF HARD EXUDATES IN FUNDUS IMAGES

In this paper, we propose an effective framework to automatically segment hard exudates (HEs) in fundus images. Our framework is based on a coarse-to-fine strategy, as we first get a coarse result allowed of some negative samples, then eliminate the negative samples step by step. In our framework, we make the most of the multi-channel information by employing a boosted soft segmentation algorithm. Additionally, we develop a multi-scale background subtraction method to obtain the coarse segmentation result. After subtracting the optical disc (OD) region from the coarse result, the HEs are extracted by a SVM classifier. The main contributions of this paper are: (1) propose an efficient and robust framework for automatic HEs segmentation; (2) present a boosted soft segmentation algorithm to combine multi-channel information; (3) employ a double ring filter to segment and adjust the OD region. We perform our experiments on the pubic DIARETDB1 dateset, which consists of 89 fundus images. The performance of our algorithm is assessed on both lesion-based criterion and image-based criterion. Our experimental results show that the proposed algorithm is very effective and robust.

Speckle correlometry method for evaluating the transport scattering coefficient of a randomly inhomogeneous medium

We propose a method for evaluating the transport scattering coefficient of a randomly inhomogeneous medium, which is based on a correlation analysis of the intensity of laser radiation backscattered from the moving medium. The method employs a localized source of radiation (laser beam focused on the surface of medium) and makes use of the spatial filtration of detected scattered radiation in the image plane of the optical system with the aid of a programmed ring filter.

Transient analysis of static and dynamic responses for a single ring-resonator-based WDM add/drop filter array

This paper has analyzed the static and dynamic characteristics of a single ring-resonator-based optical WDM add/drop filter. The analysis has shown that the coupling coefficient of the coupler between a feeding waveguide and ring waveguide greatly influences the dynamic characteristics of a ring filter. Another determining factor was one round trip time of beam in a ring waveguide. Also, coupling coefficient has had influence on static on-chip losses in both thru and add/drop operation in a ring-resonator filter array. Considering both static and dynamic characteristics, a suitable range of coupling coefficients exists. Also, sideband rejection ratio of single ring resonator based WDM filter was investigated. Our method can provide a guide for the design and realization of a single ring-resonator based WDM add/drop filter.

Time-domain and frequency-domain modeling of nonlinear optical components at the circuit-level using a node-based approach

We present a tool that aids in the modeling of optical circuits, both in the frequency and in the time domain. The tool is based on the definition of a node, which can have both an instantaneous input-output relation and different state variables (e.g., temperature and carrier density) and differential equations for these states. Furthermore, each node has access to part of its input history, allowing the creation of delay lines or digital filters. Additionally, a node can contain subnodes, allowing the creation of hierarchical networks. This tool can be used in numerous applications such as frequency-domain analysis of optical ring filters, time-domain analysis of optical amplifiers, microdisks, and microcavities. Although we mainly use this tool to model optical circuits, it can also be used to model other classes of dynamical systems, such as electrical circuits and neural networks.