Flat Dispersion Characteristics Research Articles

Influence of Temperature And Concentration of Ethanol on Properties of Borosilicate Glass Photonic Crystal Fiber Infiltrated by Water – Ethanol Mixture

In this paper, we present a numerical simulation of the properties of a photonic crystal fiber (PCF) made of borosilicate glass infiltrated by the water-ethanol mixture. We examine the influence of temperature and ethanol concentration for the refractive index, dispersion properties, effective mode area and confinement loss of the fundamental mode by a Lumerical simulation method. We also calculate the fundamental mode of the fiber infiltrated with a water-ethanol mixture with the concentration range of ethanol from 0% to 100% in the temperature range from 10°C to boiling point of ethanol. The results show that all fibers infiltrated with water-ethanol mixture have flat dispersion characteristics in the infrared range above 1.32. The best flatness exists for pure ethanol. Furthermore, it is possible to shift the zero-dispersion wavelength and modify fundamental properties of PCFs by both temperature and concentration of ethanol. The results obtained are important because of that we not only use their reasonable parameters for the design and manufacture but also use them in nonlinear phenomena and nonlinear applications of fibers as supercontinuum generation.

A Scalable THz Photonic Crystal Fiber With Partially-Slotted Core That Exhibits Improved Birefringence and Reduced Loss

A photonic crystal fiber (PCF) based on high resistivity silicon is reported that exhibits high birefringence, low loss, and flat dispersion characteristics across a wide bandwidth in the THz regime. Except for the center region, which remains the background dielectric, its core is occupied by a set of rectangular air slots. The material and configuration lead to high birefringence and low loss. The simulation results, which include the material losses, indicate that a birefringence value of 0.82 and a total loss of 0.011 cm−1, including the effective material loss and confinement losses, are achieved at 1.0 THz. These values are a factor of ten times higher and four times lower, respectively, than many recent designs. The numerical analyses also demonstrate that the reported PCF can be scaled to any desired portion of the THz regime, while maintaining a similar birefringence, simply by changing the lattice constant. This “scalable” characteristic is shown to be applicable to other PCF designs. It could facilitate a novel way of testing THz fibers, i.e., it suggests that one only needs to test the preform to validate the performance of the fiber at higher frequencies. This outcome would significantly reduce the design complexity and the costs of PCF testing.

Near-zero dispersion flattened, low-loss porous-core waveguide design for terahertz signal transmission

We demonstrate a photonic crystal fiber with near-zero flattened dispersion, ultralower effective material loss (EML), and negligible confinement loss for a broad spectrum range. The use of cyclic olefin copolymer Topas with improved core confinement significantly reduces the loss characteristics and the use of higher air filling fraction results in flat dispersion characteristics. The properties such as dispersion, EML, confinement loss, modal effective area, and single-mode operation of the fiber have been investigated using the full-vector finite element method with the perfectly matched layer absorbing boundary conditions. The practical implementation of the proposed fiber is achievable with existing fabrication techniques as only circular-shaped air holes have been used to design the waveguide. Thus, it is expected that the proposed terahertz waveguide can potentially be used for flexible and efficient transmission of terahertz waves.

A solid silica core based non-linear hybrid PCF with low confinement loss

This paper aims to analyze solid silica core based Photonic Crystal Fibre (PCF). The proposed structures consists of three inner layers of hexagonal shaped air holes and four outer layers of circular shaped holes and compare it with oval shaped structure. The broadband dispersion compensation and confinement loss covering the O, E, S, C and L bands and observed zero and negative dispersion in O and E band also very low confinement loss in all bands. The diameter of air holes is varied to generate flattened dispersion characteristics for the hybrid cladding PCF structure. Our purpose is to attain high non-linearity along with low confinement loss of two layered photonic crystal fibre for different air fill fraction d/Λ (0.65–0.95) values. Also, it is shown that the non-linear coefficient magnifies with the decreasing wavelength in PCF and the confinement losses are less than 0.001dB/km in the O-E-S-C-L wavelength range from (1.2 to 1.6) μm.

New refractive index profiles of dispersion-flattened highly nonlinear fibers for future all-optical signal processing in wdm optical networks

In this paper, we demonstrate new dissimilar refractive index profiles for highly nonlinear ultra-flattened dispersion fibers with noteworthy effective area $$(A_\mathrm{eff})$$(Aeff) for future optical signal processing. The newly proposed fibers named from Type 1 to Type 5 have a flattened dispersion over S, C, L and U bands. Predominantly, few-mode HNL-UFF fiber of Type 3 yields dispersion-flattened characteristics over a range of 250 nm of optical communication spectrum with a mere 0.2 ps/nm km variation in dispersion and a dispersion slope of $$0.0057\hbox { ps}/\hbox {nm}^{2}$$0.0057ps/nm2 km due to the contribution of higher-order modes to the dispersion characteristics of the fiber. Moreover, it has a moderate nonlinear coefficient of $$8.03\hbox { W}^{-1}\,\hbox {km}^{-1}$$8.03W-1km-1. By modifying the refractive index profile of Type 3 fiber, Type 4 and Type 5 fibers are obtained in order to ensure single-mode operation, while the zero flattened dispersion characteristics of the fiber are compromised. Among the newly proposed fibers, Type 4 fiber offers a very low ITU-T cutoff wavelength of $$1.33~\upmu \hbox {m}$$1.33μm, whereas in the case of Type 5 fiber it is $$1.38~\upmu \hbox {m}$$1.38μm. Moreover, Type 4 and Type 5 fibers have good nonlinear coefficients of $$12.26\hbox { W}^{-1}\,\hbox {km}^{-1}$$12.26W-1km-1 and $$11.45\hbox { W}^{-1}\,\hbox {km}^{-1}$$11.45W-1km-1, respectively. By virtue of the proposed optimized index profile, an insensitive behavior toward bending is displayed by Type 3, Type 4 and Type 5 fibers. In addition, Type 4 fiber provides a better splice loss of 0.25 dB.

Optimization of Si slot waveguide using approximate semi-analytical method.

The optimization of a slot waveguide for any specific application requires a study of the modal characteristics for a wide range of design parameters. Rigorous numerical methods, such as the finite element method (FEM), are time consuming and require a large amount of memory. In this paper, a simple semi-analytical method is used to analyze silicon slot waveguides and to optimize the performance of the waveguide for maximum power confinement in the slot, minimum effective mode area of the slot and to obtain flat dispersion characteristics. The results obtained by the present method agree well with the rigorous numerical results.

一种高双折射高负平坦色散压缩型光子晶体光纤

A squeezed high birefringence Photonic Crystal Fiber (PCF) with high negative flattened dispersion characteristics was proposed. In order to obtain the high birefringence characteristics, the cladding of PCF was made of squeezed triangular lattice and elliptical air holes. In order to improve the flexibility of controlling the dispersion, the core of PCF was added into a small defect air hole. The birefringence and dispersion characteristics were analyzed by super lattice method. The simulation results show that the designed PCF offers ultra flattened negative dispersion (-6677 psnm-1km-1) in a broad range of wavelengths from 1.3 m to 1.8 m, the birefringence can be reached the magnitude of 10-2 and the high birefringence can be reached 2.2110-2 at 1.55 m. Based on the high negative dispersion and high birefringence characteristic, PCF will be widely used in optical transmission system and optical fiber sensing.

Highly nonlinear enhanced-core photonic crystal fiber with low dispersion for wavelength conversion based on four-wave mixing

In this paper, a new structure of highly nonlinear low dispersion photonic crystal fiber (HNPCF) by elliptical concentration of GeO2 in the PCF core has been proposed. Using finite difference time domain (FDTD) method, we have analyzed the dispersion properties and effective mode area in the HN-PCF. Simulative results show that the dispersion variation is within ±0.65 ps/(nm·km) in C-band, especially 0.24 ps/(nm·km) in 1.55 μm wavelength. Effective area and nonlinear coefficient are 1.764 μm2 and 72.6W−1·km−1 respectively at 1.55 μm wavelength. The proposed PCF demonstrates high nonlinear coefficient, ultra small effective mode area and nearly-zero flattened dispersion characteristics over Cband, which can have important application in all-optical wavelength conversion based on four wave mixing (FWM).

Nearly zero dispersion-flattened photonic crystal fiber with fluorine-doped three-fold symmetry core

A novel design of a photonic crystal fiber is presented. A nearly zero dispersion regime of operation has been achieved by using a three-fold symmetry core, which is improved by the avoidance of high-index doping in a central region. The core consists of pure silica surrounded by three fluorine-doped regions and three airholes. It can be confirmed by the numerical simulations using the finite difference frequency domain method that flattened dispersion characteristics upon wavelength over the range of 1250 to 1700 nm can be achieved in an optical fiber. Further, the potential fiber geometry imperfections caused some concern. Finally, the presented fiber design is compared to selected fiber designs with a dispersion close to zero.

Design of highly-nonlinear horizontal slot waveguide with low and flat dispersion

We present an optimum design of highly-nonlinear horizontal slot waveguides consisting of silicon and silicon nanocrystals with flat dispersion characteristics. Results from numerical simulations show that the nonlinear coefficient of 6600W−1m−1 at 1550-nm wavelength and the dispersion values between −150 and 150ps/nm/km in the S, C, and L bands can be achieved. In addition, when we limit the operating bandwidth to C-band, the most tolerant slot height is 20nm for the 10nm fabrication errors of waveguide width and high-index region height.

Performance of Distributed Fiber Raman Amplifier Based on Hybrid Cladding Photonic Crystal Fiber

This article presents a feasibility study for using a hybrid cladding photonic crystal fiber as a distributed fiber Raman amplifier based transmission link with negligible confinement losses and flattened dispersion characteristics. The simulation results clearly indicate that a bit error rate of 10−9 can be maintained at the end of a (4 × 170)-km distributed fiber Raman amplifier link operating with 40 Gbps and 0.6 dBm transmit power if 20 dBm of pump power is used for each span.

Distortionless large-ratio stretcher for ultra-short pulses using photonic crystal fiber

A large-ratio stretcher for ultra-short pulses is proposed based on photonic crystal fiber (PCF). Through proper design of the PCF structure, we obtain over 300-nm wavelength range with flattened dispersion characteristics. Analysis indicates that 1-km of such fiber can broaden over 10,000 times for ultra-short pulses with <100-fs pulse-width. Distortion due to dispersion and nonlinearity is negligible.

A Novel Defected Elliptical Pore Photonic Crystal Fiber with Ultra-Flattened Dispersion and Low Confinement Losses

This paper reports a novel design in Photonic Crystal Fibers (PCFs) with nearly zero ultra-flattened dispersion characteristics. We describe the chromatic dispersion controllability taking non-uniform air hole structures into consideration. Through optimizing non-uniform air hole structures, the ultra-flattened zero dispersion PCFs can be efficiently designed. We show numerically that the proposed non-uniform air cladding structures successfully archive flat dispersion characteristics as well as extremely low confinement losses. As an example, the proposed PCF with flattened dispersion of ±0.27 ps/(nm·km) from 1.5 μm to 1.8 μm wavelength with confinement losses of less than 10 -11 dB/m. Finally, we point out that full controllability of the chromatic dispersion and confinement losses, along with the fabrication technique, are the main advantages of the proposed PCF structure.

Theoretical realization of holey fiber with flat chromatic dispersion and large mode area: an intriguing defected approach

We present a novel design approach for realizing holey fibers (HFs) with flat dispersion characteristics and large mode area based on the existence of an artificially defected air-hole ring in the cladding, and on the inclusion of additional defected air holes in the core of the fiber. This unique type of HF can be used for achieving remarkable flat dispersion characteristics as well as a large mode area, which are particularly useful for high-speed data transmission. The validation of the proposed design is done by adopting an efficient full-vectorial finite element method for optical characterization of HFs. The proposed fiber can be employed in reconfigurable optical transmission systems for performing wavelength division multiplexing operation. Typical characteristics of the proposed HF are a flattened dispersion of 6.3 +/- 0.5 ps/km/nm from 1.45 to 1.65 microm and an effective mode area as large as 100 microm2 in the same frequency range.

Modified design of photonic crystal fibers with flattened dispersion

We present a modified method to design photonic crystal fibers with flattened dispersion characteristics. By replacing the circular air-holes of the first central ring with elliptic air-holes, we observe a more flattened dispersion curve. Plane-wave expansion (PWE) method is used to analyze the dispersion property in a high-index core PCF. The simulation results are presented, and ultra-low and ultra-flattened dispersion curves over wide wavelength range are demonstrated.