Parameters Of Photonic Crystal Fiber Research Articles

Predicting different losses of photonic crystal fibers in material and hetero-core domain

In order to develop the effective transmission in photonic crystal fiber (PCF), the (realizable fiber i.e.,) losses arising from bending as well as splicing are very vital issues. We report here macrobending loss of PCFs in different material composites. Further, we make comprehensive numerical analysis related to splice loss issues arising from joining PCF with PCF and single mode fiber as well. We additionally investigate dependence of all these losses with respect to structural parameters of PCF. Hetero core systems are found to yield lower losses as compared to their identical counterpart. The numerical estimates reported here will provide a base for engineering effective communication guides in the context of material and hybrid core domain.

Effects of structure parameters on the sensor performance of photonic crystal fiber

A simple and compact sensor based on a photonic crystal fiber (PCF) for the in-situ detection of fluorescence signals with high sensitivity is demonstrated. Several different kinds of PCF probes are studied. The effect of PCF parameters on sensitivity and the guiding mechanisms are analyzed, and the performance of PCF probes is experimentally evaluated by measuring the fluorescence signal of Cy3 dye. In addition, the detection sensitivity of the hollow-core PCF probe and the flat-tippedmulti-mode fiber probe is compared. The experimental results show that the hollow-core PCF probe provides a greater than five-fold increase in detection sensitivity compared with direct measurements by a flat-tippedmulti-mode fiber probe, which shows its potential for wide applications to in-situ detection in the medical, forensic, biological, geological, and environmental fields with high sensitivity.

Numerical analysis of ultrabroadband polarization splitter based on gold-filled dual-core photonic crystal fiber

An ultrabroadband polarization splitter based on gold-filled dual-core photonic crystal fiber (PCF) has been proposed. The resonance strength of the surface plasmon mode and polarization-splitter characteristics are studied by changing the positions and amount of gold wires and the structural parameters of PCF through simulation based on finite element method. The polarization splitter can provide extinction ratio lower than −20dB with a bandwidth of 400nm covering almost all communication bands (O, E, S, C, L and U bands).

Confinement loss in hexagonal lattice photonic crystal fibers

In this paper, confinement loss in hexagonal lattice photonic crystal fibers (PCFs) has been investigated. Using finite difference frequency domain (FDFD) method with perfectly matched layers (PMLs) boundary conditions, the effect of air holes deformation and also changing the design parameters of PCFs on the confinement loss theoretically studied. We realized that by increasing relative holes size, air filling fraction increased, imaginary part of effective index decreased and therefore the confinement loss reduces. We also realized that by increasing the number of holes rings, confinement loss reduces dramatically. We also have shown that the confinement loss of hexagonal lattice PCFs are sensitive to the shape and size of deformed air-hole. Furthermore, we theoretically proposed an ultra-low confinement loss PCF with a nearly zero confinement loss and a total loss lower than 0.3dB/km over C-band and particularly 0.116dB/km in 1.55μm wavelength.

Optimization design of high-sensitivity temperature sensor based on Bragg grating in liquid-filled photonic crystal fibers

A high-sensitivity temperature sensor based on fiber Bragg gratings (FBGs) in liquid-filled photonic crystal fibers (PCFs) is proposed. PCF is designed using the full-vector finite-element method. To achieve the maximum difference of the core-mode effective index of PCF as the temperature change, the structural parameters of PCF are optimized via genetic algorithms. The calculated Bragg wavelength shift (BWS) value of FBGs in liquid-filled PCF is 263 pm/°C as the temperature changes from −15°C to 65°C.

Characteristics of tuneable optical filters using optical ring resonator with PCF resonance loop

A theoretical analysis of a tuneable optical filter is presented by proposing an optical ring resonator (ORR) using photonic crystal fiber (PCF) as the resonance loop. The influences of the characteristic parameters of the PCF on the filter response have been analyzed under steady-state condition of the ORR. It is shown that the tuneability of the filter is mainly achieved by changing the modulation frequency of the light signal applied to the resonator. The analyses have shown that the sharpness and the depth of the filter response are controlled by parameters such as amplitude modulation index of applied field, the coupling coefficient of the ORR, and hole-spacing and air-filling ratio of the PCF, respectively. When transmission coefficient of the loop approaches the coupling coefficient, the filter response enhances sharply with PCF parameters. The depth and the full-width at half-maximum (FWHM) of the response strongly depend on the number of field circulations in the resonator loop. With the proposed tuneability scheme for optical filter, we achieved an FWHM of ~1.55 nm. The obtained results may be utilized in designing optical add/drop filters used in WDM communication systems.

Computation of Parameters for Dispersion Compensating Photonic Crystal Fiber Using a Novel Approach

In this article, an efficient compact two dimensional finite-difference frequency-domain (2-D FDFD) method has been used to model photonic Crystal fiber (PCF). Different values of dispersion coefficient can be obtained by changing fiber parameters using FDFD method. Since for each one of these parameters there exists a different value for dispersion coefficient, selection of optimal point will be a time consuming process. Here, first of all, we calculate parameter K, which is the key factor to design dispersion compensated fibers, so the design process will be faster and easier. The optimal value for K parameter is around 301.8 nm for transmission line fibers. So, it is enough to sketch both dispersion curve and K parameter versus PCF parameters, in a single coordinate system. Proper parameters will be obtained by analyzing the curves.

Tailoring Of Flattened Dispersion In Triangular-Lattice Photonic Crystal Fiber

The interest of researchers and engineers in several laboratories, since the1980s, has been attracted by the ability to structure materials on the scale of the optical wavelength, a fraction of micrometers or less, in order to develop new optical medium, known as photonic crystals . Photonic crystals rely on a regular morphological microstructure of air-holes, incorporated into the material, which radically alters its optical properties. In Photonic Crystal Fiber (PCF) it is possible to realize flat dispersion over a wide wavelength range that cannot be realized with a conventional singlemode fiber. In PCFs, the dispersion can be controlled and tailored with unprecedented freedom. In fact, due to the high refractive index difference between silica and air, and to the flexibility of changing airhole sizes and patterns, the waveguide contribution to the dispersion parameter can be significantly changed, thus obtaining unusual position of the zero dispersion wavelength, as well as particular values of the dispersion curve slope. In particular, by manipulating the air- hole radius or the lattice period of the micro structured cladding, it is possible to control the zero-dispersion wavelength, which can be tuned over a very wide range, or the dispersion curves, which can be engineered to be ultra flattened. In this paper the geometric parameters of triangular PCF have been properly changed to optimize the dispersion compensation over a wide wavelength range.

Correspondence Between Effective Mode Area and Dispersion Variations in Defected Core Photonic Crystal Fibers

In the present paper, the impact of defect insertion in the core area of a large core HF7 fiber on the effective mode area and chromatic dispersion characteristics is investigated to enhance the performance parameters of photonic crystal fibers (PCF). The obtained results meet the requirements of the wideband high-speed optical transmission systems. A novel method for increasing the effective mode area of PCFs without increasing the hole pitch is presented that is based on the mode field distribution modification by defect insertion. Furthermore, it is shown that the dispersion curve is predictable from the effective mode area variations in response to changing the defect parameters. Based on the aforementioned characteristics, the first fully systematic procedure to design a large mode area, dispersion flattened, low-loss and single-mode PCF is presented and employed to design a defected core fiber with chromatic dispersion of 2.9 ± 0.5 ps/(km·nm) in the S + C + L communication band with effective mode area larger than 80 μm2 in the same wavelength range with excellent loss and single-modeness properties.

Transmission Characteristics of Tuneable Optical Filters Using Optical Ring Resonator with PCF Resonance Loop

A theoretical analysis of a tuneable optical filter is presented by proposing an optical ring resonator (ORR) using photonic crystal fiber (PCF) as the resonance loop. The influences of the characteristic parameters of the PCF on the filter response have been analyzed under steady-state condition of the ORR. It is shown that the tuneability of the filter is mainly achieved by changing the modulation frequency of the light signal applied to the resonator. The analyses have shown that the sharpness and the depth of the filter response are controlled by parameters such as amplitude modulation index of applied field, the coupling coefficient of the ORR, and hole-spacing and air-filling ratio of the PCF, respectively. When transmission coefficient of the loop approaches the coupling coefficient, the filter response enhances sharply with PCF parameters. The depth and the full-width half-maximum (FWHM) of the response strongly depends on the number of field circulations in the resonator loop. With the proposed tuneability scheme for optical filter, we achieved an FWHM of ~1.55 nm. The obtained results may be utilized in designing optical add/drop filters used in WDM communication systems.

Low-dispersion high-birefringence effect of squeezed hexagonal lattice elliptical hole photonic crystal fiber

A new type of photonic crystal fiber for realizing the effect of low dispersion high birefringence is proposed. The fiber is composed of a solid silica core and a cladding with squeezed-hexagonal-lattice elliptical air-hole along the fiber length. Dispersion and birefringence are investigated simultaneously by using the full vectorial plane wave method. Simulations indicate that the wavelength for realizing low-dispersion high-birefringence can be controlled by artificially choosing the structure parameters of photonic crystal fiber, such as the hexagonal lattice squeezing ratio, the relative air hole spacing and the air hole ellipticity. The optimal and feasible parameters of the fiber with low-dispersion high-birefringence are given, with the result of the total dispersion being within ±5 ps·nm-1km-1 over an ultra broad wavelength range from 1360 to 1670 nm and the corresponding high birefringence being about 15×10-2 at 1550 nm.

Design of compact long-period gratings imprinted in optimized photonic crystal fibers

To imprint a long-period grating (LPG) in a photonic crystal fiber (PCF) with an optimum response, first the parameters of the PCF should be optimized. In this paper, by using a semi-analytical enhanced improved vectorial effective index method, the optimized PCF parameters are determined by dividing the single-mode operation of the PCF into two regions in terms of air-hole spacing Λ (Λ>3 μm and Λ≤3 μm). For each region appropriate expressions are suggested to evaluate the PCF parameters. By calculating the effective refractive index difference between the optimized core and cladding of the PCF under a phase-matching condition, the optimum grating period in terms of the PCF parameters is obtained.

Design of low-loss single-polarization single-mode photonic-crystal fiber based on polymer

A new structure for single-polarization single-mode photonic-crystal fiber is proposed and numerically analyzed by using a full vector finite element method with anisotropic perfectly matched layers. The cutoff wavelength of two linearly polarized states can be controlled artificially by varying the structure parameters of photonic crystal fiber. The confinement loss are also numerically calculated and optimized at 650 nm communication wavelength of polymer optical fiber. From the numerical results it is confirmed that the proposed fiber is low-loss single-polarization single-mode photonic-crystal fiber within the wavelength range from 0.63 to 0.73 µm, where only the slow-axis mode exists and the confinement loss is less than 0.05 dB m−1.

Ultrabroadband photon pair preparation by spontaneous four-wave mixing in a dispersion-engineered optical fiber

We present a study of the spectral properties of photon pairs generated through the process of spontaneous four-wave mixing (SFWM) in single mode fiber. Our analysis assumes narrowband pumps, which are allowed to be frequency degenerate or nondegenerate. Based on this analysis, we derive conditions on the pump frequencies and on the fiber dispersion parameters which guarantee the generation of ultrabroadband photon pairs. Such photon pairs are characterized by (i) a very large degree of entanglement, and (ii) a very high degree of temporal synchronization between the signal and idler photons. Through a numerical exercise, we find that the use of photonic crystal fiber (PCF) facilitates the fulfilment of the conditions for ultrabroadband photon pair generation; in particular, the spectral region in which emission occurs can be adjusted to particular needs through an appropriate choice of the PCF parameters. In addition, we present a quantum interference effect, resulting from indistinguishable pathways to the same outcome, which can occur when pumping a SFWM source with multiple spectral lines.

Study of the sensitivity of gas sensing by use of index-guiding photonic crystal fibers

We demonstrate an absorption transmission spectrum of CH(4) in a 16.9 cm long index-guiding photonic crystal fiber (PCF) fabricated in our laboratory. One of the main factors to improve the sensitivity is to increase the fraction of power in PCF cladding air holes. We study the fraction of power in PCF cladding air holes as a function of the index-guiding PCF parameters. We found that a PCF with small spacing and a large air-filling ratio has a higher fraction of power in its cladding air holes. At the same time the mode area in this PCF is small and would generate strong nonlinear effects in the fiber. If we use a PCF in which the core is formed by missing seven air holes, it is immediately obvious that the PCF used as a sensor has higher sensitivity and a larger mode area.

Loss analysis of single‐mode fiber/photonic‐crystal fiber splice

AbstractThe connection loss between single‐mode fiber and photonic crystal fiber (PCF) is analyzed by using a full‐vector finite‐element method. PCF parameters for achieving low loss connection (for example, less than 0.5 dB) are reported. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 378–380, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11387