Fiber-optic Filter Research Articles

Performance analysis of a photonic crystal fiber polarization filter filled with different materials.

A compact square photonic crystal fiber polarization filter with high performance is proposed. Two larger holes filled with different metal and fluid are designed to break the strict structure symmetry and forming high birefringence. Four small pores are designed to provide a wider channel for the coupling between defect mode and core mode. Its filtering and coupling characteristics are analyzed by the full vector finite element method. In addition, the properties of PCF filled with different materials are compared and discussed. Different metal materials have different dielectric constants, different optical damping, interband transitions, molecular structure, and physicochemical properties, which make their transmission modes and coupling strength different. The results show that the performance of a PCF filter filled with gold and liquid is the best, which is very suitable for an adjustable PCF polarization filter. The calculation results show that the extinction ratio of the designed filter can reach 5383 dB for a device length of 3 mm; the unwanted fiber loss can reach 2073 dB/cm; and the applicable bandwidth of 2000 nm covers almost the whole communication band. The proposed polarization filter shows large unwanted loss, high extinction ratio, wide bandwidth and coordination, which make it a good candidate for excellent optical fiber filter devices.

Multiwavelength synchronously Q-switched Erbium-doped fiber laser based on the adjustment of the free spectral range of an intracavity tapered-fiber filter

All-fiber multiwavelength Q-switched (MWQS) lasers are of huge interest because of their emergent and well-known scientific and technological applications. Passive all-fiber MWQS lasers require a saturable absorber to generate Q-switched pulses and an optical filter to seed the multiwavelength regime. New trends in all-fiber MWQS lasers demand new devices to explore innovative configurations and capabilities in this kind of lasers. In this sense, we report on the experimental demonstration of a multiwavelength synchronously Q-switched Erbium-doped fiber laser (QSEDFL). This laser achieves dual and triple wavelength lasing around 1530 nm with interchangeable wavelength separation. A shorth piece of Tm:Ho co-doped fiber is the saturable absorber. An intracavity tapered optical fiber filter in a double-pass configuration allows the versatile process of wavelength filtering, enabling the adjustment of wavelength lasing separation between 1.7 nm, 2.1 nm, and 2.5 nm with synchronized pulses of each wavelength component. This proposal offers a new route to all-fiber multiwavelength synchronously Q-switched laser with potential applications for WDM systems and all-fiber sensors.

A Fiber-Attached Coupler for Transmission Bandpass Whispering Gallery Mode Resonator

A fiber attached coupler for transmission bandpass whispering gallery mode (WGM) resonator is proposed and experimentally demonstrated. The coupler fabricated by femtosecond laser ablation consists of a pair of curved waveguides with a curvature radius of 50 μm, by which the WGM field is excited and collected through evanescent field coupling, respectively. As a proof of concept, a polymer microsphere functioning as the WGM cavity is embedded into a femtosecond laser ablated hole between the two curved waveguides. A passband with a full width of 0.15 nm at half maximum is observed when the microsphere is surrounded by air, verifying the feasibility of the proposed coupler for constructing a WGM cavity-based transmission narrow bandpass optical fiber filter. Benefitting from the relatively high thermo-optical coefficient, the passband of a packaged transmission bandpass WGM resonator can be thermo-optically tuned with a sensitivity of 446.6 pm/°C.

СОЗДАНИЕ ИНТЕГРИРОВАННОЙ СИСТЕМЫ ДЛЯ МОНИТОРИНГА ТЕХНИЧЕСКОГО СОСТОЯНИЯ ВЫСОКОКАЧЕСТВЕННЫХ ВЕРТОЛЕТНЫХ БЛОКОВ НА ОСНОВЕ ВОЛОКОННО-ОПТИЧЕСКОЙ ТЕХНОЛОГИИ

This article draws attention to the difficulties in developing an integrated approach, especially the evaluation and evaluation of the main helicopter technology. Fiber optic technology is a technology that allows you to create a unified system. This allows the measurement of various physical parameters such as vibration, distortion, temperature, volume and other parameters, given the magnitude of optical fiber science. RMB can be integrated into production, which is an important factor in the amount of RMB related to the design and manufacture of helicopters. The test results, the test bench, and the rotor of the helicopter and light using optical fiber transmission in the Prague fiber optic filter emphasize the importance of developing technology to track the helicopter's use of optical fiber. Other embodiments of the use of optical transmission systems that use fiber-optic technology, such as cable warning of explosives and helicopter damage as well as system weight and transitions. The conduction system monitors air technology.

Switchable dual-wavelength erbium-doped fiber laser based on the broadband filtering performance of tapered long period fiber gratings

In this paper, a switchable, dual-wavelength erbium-doped fiber laser, based on the broadband filtering performance of a tapered long-period fiber grating, is experimentally demonstrated. The lasing emission can be built up in sets of dual-wavelengths in the entire C-band, with variable and controllable separation between laser lines from 6.75 nm to 35 nm when the optical fiber filter structure is gradually bent.

Broadband tunable single-longitudinal-mode erbium-doped fiber ring laser based on a microfiber knot resonator.

We propose and demonstrate a broadband tunable single-longitudinal-mode (SLM) erbium-doped fiber laser based on a microfiber knot resonator (MKR). The MKR is made from a double-ended fiber taper and employed for SLM filtering based on the Vernier effect. An unpumped erbium-doped fiber is used in the fiber laser cavity to suppress mode-hopping for a stabilized SLM laser operation. When combined with an optical fiber filter, widely tunable SLM laser generation is achieved. The proposed SLM laser can be tuned from 1545 to 1565 nm with a high side-mode suppression ratio of about 55 dB and a high stability.

Fiber Twist-based Wavelength Tunability in Tapered Optical Fiber Filters

This work demonstrates the tunability of tapered single mode fiber (SMF) and tapered polarization maintaining fiber (PMF) filters based on fiber twisting method. One end of the tapered fiber was twisted from 0o until 100o using the Vytran Fiber Processing System. Observation on the spectral output shows that the fiber twisting technique is a viable option to impart tunability in tapered fibers with total shift of 15 and 10 nm, respectively for SMF and PMF. Better tunability is observed in the SMF filter due to its simple physical structure and more straightforward interferometry effect but a significantly higher extinction ratio is observed for the PMF filter. Both filters exhibited region of linear wavelength shift with corresponding R2 values of 0.9924 and 0.9294 for SMF and PMF. The simplicity and reliability of the filter may pave the way for the development of a practical and compact tunable all-fiber filter for laser systems.

Simulation study of signal gain optimization based on hybrid composition techniques for high-speed optically dense multiplexed systems

Abstract This study created a 13 Gb/s transmission speed per 300 channel dense wavelength division multiplexing system based on hybrid optical fiber amplifiers and filter techniques to enhance signal gain. The filter techniques used here included a hybrid optical amplifier, a gain flattening filter (GFF), a Fabry–Perot filter, a fiber Bragg grating (FBG), and glass composition technique. The techniques were combined to optimize signal gain as follows: the study began with an erbium-doped fiber amplifier (EDFA), added a Raman amplifier, added GFF, added fiber Bragg grating, added glass composition, and finally achieved a hybrid-modified model after adding Fabry–Perot filter. The signal gain was optimized with the hybrid-modified model via the different operating parameters of the EDFA. The proposed model also showed a better performance (30–40 dB greater) than the previous model (Mahran O, Aly MH. Performance characteristics of dual-pumped hybrid EDFA/Raman optical amplifier. OSA – Applied Optics Jan 2016;55:22–6) after changing the values of the signal wavelength, the EDFA, and the length of the Raman amplifier.

New simulation and analysis fiber Bragg grating: narrow bandwidth without side lobes

The purpose of this paper is to simulate and analyze the spectral characteristics of the fiber Bragg grating (FBG) to obtain narrow bandwidth and minimization side lobes in reflectivity. Fiber Bragg grating has made a big revolution in telecommunication systems. The existence of fiber Bragg grating is needed when an optical fiber amplifier and filter are used. They can be used as band reject filter or band pass filter for optical devices. The model equations of the cascaded uniform fiber Bragg grating and different cascaded apodization functions such as, Hamming apodized fiber Bragg grating, Barthan apodized fiber Bragg grating, Nuttal apodized fiber Bragg grating, Sinc apodized fiber Bragg grating and Proposed apodized fiber Bragg grating are numerically handled and processed via specially cast software to achieve maximum Reflectivity, narrow bandwidth without side lobes.

Switchable and tunable multi-wavelength fiber ring laser employing a cascaded fiber filter

• We propose a novel cascaded hybrid fiber filter. • A switchable and tunable multi-wavelength fiber laser. • This laser has excellent robustness because of no core-offset splicing point. • This laser operates more stably compare to the previous similar works. A switchable and tunable multi-wavelength fiber laser based on cascaded hybrid fiber filter (CHFF) is proposed and demonstrated. The CHFF is composed of a single ellipsoid hybrid structure optical fiber filter (SE-HSOFF) and a Sagnac loop interferometer. Here the SE-HSOFF consists of single mode fiber (SMF)-few mode fiber (FMF)-SMF, and there is an ellipsoidal structure fabricated by SMF-FMF. It has the function of realizing the switchability of fiber laser. The Sagnac loop interferometer incorporated with a segment of polarization maintaining fiber (PMF) is used as a tuning component. By adjusting the state of polarization controller (PC), the laser can operate in single-, dual-, triple- and quadruple-wavelength laser states, and the lasing wavelength can be tuned by about 10 nm when it operates in dual-wavelength state. The optical signal to noise ratio (OSNR) is larger than 30.0 dB. This laser has excellent robustness because there is no core-offset splicing point and operates very stably in every output state at room temperature.

Compact fiber-optic spectroscopic design and its validation in atmospheric water vapor Raman lidar

Spectroscopic systems with compact structure, high reliability, and high stability will push forward the application of lidar in the meteorological and environmental fields as well as space-based and space-borne lidar. Recently, we have successfully designed and verified a new robust fiber-optic spectroscopic Raman lidar for atmospheric water vapor measurements. The compact fiber-optic Raman spectroscopic design was proposed with a cascaded fiber Fabry–Perot filter and a fiber broadband filter, which features an all-fiber-connection structure and a high-spectral-resolution spectrum. These fiber-optic filters have been successfully fabricated in the visible region and matched each other in individual all-fiber Raman channels. The performance of the all-fiber spectroscopic system is measured experimentally, and it is demonstrated that the spectral output from the individual fiber Raman channel provides a bandwidth of 3–4 nm, a central wavelength of 660 nm or 606.7 nm, and an efficient rejection rate of more than > 10 7 , and it can thus achieve the extraction of vibrational Raman scattering signals from water vapor and from nitrogen molecules in lidar returns and simultaneously reject elastic scattering signals. Furthermore, the fiber-optic spectroscopic Raman lidar was developed at Xi’an University of Technology in Xi’an, China (34.233°N, 108.911°E), and preliminary exploration was carried out for water vapor measurements. Two measurement examples are analyzed to validate the lidar performance and the retrieved water vapor mixing ratio profiles, and its comparisons with Weather Research and Forecasting (WRF) model data also verified the correctness of the lidar data. Despite the limitation of low coupling efficiency by a single-mode optical fiber, atmospheric water vapor measurements up to 700 m were achieved during nighttime under conditions of a 150 mJ laser pulse energy, a 600 mm telescope, and a 5 min integration time. The results validated the concept of all-fiber spectroscopic design and its feasibility for atmospheric water vapor measurements by Raman lidar. The compact fiber-structure characteristics and excellent optical properties provide a new solution to the new spectroscopic technique for operational applications of lidar and space-borne lidar.

Chalcogenide Optical Fiber Components -INVITED

This talk features recent achievements of the Nonlinear Photonics Group at McGill University towards the fabrication of chalcogenide-based optical fiber components such as nonlinear gain fibers, optical fiber couplers, filters, and saturable absorbers.

Switchable multi-wavelength fiber laser based on hybrid structure optical fiber filter

A switchable multi-wavelength fiber laser based on a novel hybrid structure optical fiber filter (HSOFF) is proposed and demonstrated. The HSOFF is consisted of single mode fiber (SMF)-few mode fiber (FMF) with two ellipsoidal structures and FMF-SMF with a core-offset splicing point. Two ellipsoidal structures can effectively excite the high-order modes, then the high-order modes interfere with fundamental mode at the core-offset splicing point. It can be demonstrated that the HSOFF has the comb filter property with the maximum extinction ratio is more than 13 dB while the insert loss is only 9.95 dB. Using HSOFF in proposed laser system, a switchable multi-wavelength fiber laser with stable dual-, triple- and quadruple wavelength lasers can be obtained by adjusting the state of polarization controller, at the same time the lasing wavelength locations also can be switched. The optical signal to noise ratio (OSNR) is larger than 30.68 dB, and this laser exhibits the excellent stability at room temperature.

Design of single-polarization single-mode photonic crystal fiber filter with four small holes near the core based on second-order and third-order surface plasmon polariton modes

A single-mode single-polarization photonic crystal fiber (SMSP-PCF) filter at the wavelengths of 1.125 and 1.31 μm based on surface plasmon resonance is proposed and studied by the finite element method. Numerical results indicate that compared with the filter with the same size of holes near the core, the filter with four small holes near the core makes its extinction ratio (ER) at the wavelengths of 1.125 and 1.31 μm twice as large. That is, when the fiber length is 500 μm, the ER at 1.125 μm increases from 33.43 to 58.62 dB, and the ER at 1.31 μm increases from 129.41 to 244.85 dB. Furthermore, the designed SMSP-PCF filter also has a good structural tolerance. The proposed optical fiber filter has excellent performance of compact structure, high ER and good structural tolerance, and can be used in an integrated communication transmission system.

Fiber loop mirror based single-platform multifunctional Michelson–Gires–Tournois filter

Abstract A single platform multifunctional fiber optic filter is presented. The filter is based on a Michelson–Gires–Tournois Interferometric (MGTI) structure, which makes use of high dynamic range fiber loop mirrors (FLM) for the tunability of the required reflectance. Path length control is another degree of freedom which provide the multifunctionality in the optical transfer function of the filter. The optical filter can be configured to suppress optical side bands, shape the amplitude of optical combs, or perform spectral slicing for signal processing. Rectangular pass-band transfer functions (TF) with tunable center frequency (tens of GHz) and tunable frequency bandwidth (BW) with side lobe suppression of more than 20 dB and ripple of 99%) and optical paths can change the TF to notch type with 250 MHz bandwidth. Further reflectance modification (

Fiber-optic filter fluorometer for emission detection of Protoporphyrin IX and its direct precursors – A preliminary study for improved Photodynamic Therapy applications

Abstract In this work we present first results of a laboratory manufactured filter-fluorometer to study differences in intensity and position of the main peaks of three porphyrins that appear during the Heme-Synthesis. Porphyrins play a major role in Photodynamic Therapy (PDT) for cancer treatment. Within the Heme-Synthesis, Porphyrins such as Protoporphyrin IX (PPIX) and its two precursors Coproporphyrin III (CPIII) and Uroporphyrin III (UPIII) represent photochemical agents that can interact with light to show fluorescence or generate Reactive Oxygen Species (ROS) to destroy cells. A major problem that arises is determining the ideal time slot to begin treatment after drug application. Our work is meant to show a way to solve this problem by looking at concentration changes of precursors appearing in Heme-Synthesis and using these changes to predict the occurence of PPIX inside the mitochondria.

Highly Stable, Tapered Fiber Filter-Assisted, Multiwavelength Q-Switched Er-Doped Fiber Laser Based on Tm-Ho Fiber as a Saturable Absorber

A multiwavelength Q-switched erbium-doped fiber ring laser based on a section of Tm-Ho codoped fiber as a saturable absorber, assisted by a tapered optical fiber filter to stabilize the lasing performance is reported. The tapered fiber structure acts as a comb filter that allows us simultaneous lasing wavelengths at 1529.69, 1531.74, and 1533.48 nm with high stability. By adjusting the pump power, optical pulses with repetition rates from 10.46 to 61.8 kHz were obtained. The maximum average output power was 27.61 mW, while 496.34 nJ for the maximum pulse energy. The fiber laser exhibits a power deviation of ± 0.376 dB, an OSNR of 54 dB, and a spectral width of lasing lines of 0.06 nm, with stable multiwavelength lasing.

Solc-Like Tunable Birefringent Fiber Filter Based on Elliptical-Core Spun Fiber

A novel tunable all-fiber birefringent filter based on elliptical-core spun fiber (ECSF) is presented. It is the first time to build a discrete model of spun fiber by using Jones matrix analysis. The transmission characteristics of proposed filter are studied and discussed in detail, while a generalized formulation to express the transmissivity of the birefringent filter is derived. On this basis, the effect factors of filter characteristic are deeply analyzed and simulated. Compared with the conventional fiber-optic Solc filter, the proposal is easy fabricated and implemented with low loss. By utilizing appropriate length and parameters of the ECSF, a narrowband and high-extinction ratio periodic optical filter is realized. The proposed filter also can be finely tuned covering one free spectral range, which has potential applications for fiber sensing and flexible multi-wavelength fiber laser.

Heat and mass transfer analysis in natural convection flow of nanofluid over a vertical cone with chemical reaction

PurposeIn recent years, nanofluids are being widely used in many thermal systems because of their higher thermal conductivity and heat transfer rate. The higher thermal conductivity depends on many parameters such as size, shape and volume and the Brownian motion and thermophoresis of added nanoparticles. The purpose of this paper is to analyze the influence of the Brownian motion and thermophoresis on natural convection heat and mass transfer boundary layer flow of nanofluids over a vertical cone with radiation.Design/methodology/approachUsing similarity variables, the non-linear partial differential equations, which represent momentum, energy and diffusion, are transformed into ordinary differential equations. The transformed conservation equations are solved numerically subject to the boundary conditions by using versatile, extensively validated, variational finite-element method.FindingsThe sway of significant parameters such as magnetic field (M), buoyancy ratio parameter (Nr), Brownian motion parameter (Nb), thermophoresis parameter (Nt), thermal radiation (R), Lewis number (Le) and chemical reaction parameter (Cr) on velocity, temperature and concentration evaluation in the boundary layer region is examined in detail. The results are compared with previously published work and are found to be in agreement. The velocity distributions are reduced, while temperature and concentration profiles elevate with a higher (M). With the improving values of (R), the velocity and temperature sketches improve, while concentration distributions are lowered in the boundary layer region. The temperature and concentration profiles are elevated in the boundary layer region for higher values of (Nt). With the increasing values of (Nb), temperature profiles are enhanced, whereas concentration profiles get depreciated in the flow region.Social implicationsIn recent years, it has been found that magneto-nanofluids are significant in many areas of science and technology. It has applications in optical modulators, magnetooptical wavelength filters, tunable optical fiber filters and optical switches. Magnetic nanoparticles are especially useful in biomedicine, sink float separation, cancer therapy, etc. Specific biomedical applications involving nanofluids include hyperthermia, magnetic cell separation, drug delivery and contrast enhancement in magnetic resonance imaging.Originality/valueTo the best of the authors’ knowledge, no studies have assessed the impact of the two slip effects, namely, Brownian motion and thermophoresis, on the natural convection of electrically conducted heat and mass transfer to the nanofluid boundary layer flow over a vertical cone in the presence of radiation and chemical reaction; therefore, this problem has been addressed in this study. Comparison of the results of this study’s with those of previously published work was found to be in good agreement.

A simple and compact fluorescence detection system for capillary electrophoresis and its application to food analysis

A novel fluorescence detection system for CE was described and evaluated. Two miniature laser pointers were used as the excitation source. A Y-style optical fiber was used to transmit the excitation light and a four-branch optical fiber was used to collect the fluorescence. The optical fiber and optical filter were imported into a photomultiplier tube without any extra fixing device. A simplified PDMS detection cell was designed with guide channels through which the optical fibers were easily aligned to the detection window of separation capillary. According to different requirements, laser pointers and different filters were selected by simple switching and replacement. The fluorescence from four different directions was collected at the same detecting point. Thus, the sensitivity was enhanced without peak broadening. The fluorescence detection system was simple, compact, low-cost, and highly sensitive, with its functionality demonstrated by the separation and determination of red dyes and fluorescent whitening agents. The detection limit of rhodamine 6G was 7.7 nM (S/N = 3). The system was further applied to determine illegal food dyes. The CE system is potentially eligible for food safety analysis.