Muhammad Abdul Goffar Khan

Optimum design of a dispersion managed photonic crystal fiber for nonlinear optics applications in telecom systems

This paper presents an optimum design for highly nonlinear dispersion managed photonic crystal fibers. The APSS version 2.3 software is used as the simulation tool. According to simulation, an eight-ringed photonic crystal fiber can be designed with a high nonlinear coefficient at 1550 nm of the order 36.5 W-1km-1 with simultaneously flatter dispersion characteristics and low confinement losses. This fiber also assumes a high birefringence and has a modest number of design parameters.

Improvement of speech enhancement techniques for robust speaker identification in noise

This paper presents an approach of speech enhancement techniques to improve the performance of the robust speaker identification under noisy environments. Start-end points detection, silence part removal, frame segmentation and windowing technique have been used to pre-process and wiener filter has been used to remove the silence parts from the speech utterances. To extract the features from the speech various speech parameterization techniques that is LPC, LPCC, RCC, MFCC, ΔMFCC and ΔΔMFCC have been simulated. Finally, to measure the performance of the proposed speech enhancement techniques, genetic algorithm has been used as a classifier for the noise robust automated speaker identification system and various experiments have performed on genetic algorithm to select the optimum parameters. According to the NOIZEOUS speech database, the highest identification rate of 70.31 [%] for text-dependent and of 61.26 [%] for text-independent speaker identification system have been achieved.

Chromatic Dispersion Properties of A Decagonal Photonic Crystal Fiber

This paper presents dispersion characteristics of a decagonal photonic crystal fiber (D-PCF) for the first time. The finite difference method (FDM) with an anisotropic perfectly matched boundary layer (PML) is used to investigate the chromatic dispersion characteristics. It is shown through numerical simulation results that D-PCFs can be used as a dispersion compensating fiber for their high negative dispersion slope characteristic. The dependency of chromatic dispersion with pitch, wavelength and air-hole diameters are also presented. Moreover, dispersion properties of D-PCF have been compared with that of the octagonal PCF (O-PCF) and hexagonal PCF (H-PCF), respectively.

Design of a Duobinary encoder and decoder circuits for communication systems

This paper presents microcontroller based schematic circuit design of a complete duobinary encoder (duobinary code from binary bit) and duobinary decoder (binary from duobinary code) for data communication system. Binary code having two levels of bit sequence 1 and 0. On the other side Duobinary (DB) is a three-level code having 1, 0 and −1 levels. Using duobinary transmission instead of binary transmission, it can improve the system performance, bandwidth efficiency of output signal.

Microprocessor based temperature monitoring and control system using fuzzy logic controller

A closed loop control system incorporating fuzzy logic has been developed for a class of maintenances of temperature of a heating chamber. A unique fuzzy logic controller (FLC) structure with an efficient realization and a small rule base that can be easily implemented in existing industrial controllers was proposed. The performance of this system has been measured in various environmental conditions such as compensating for thermo mass changes in the system, dealing with unknown and variable delays, operating at different temperature setpoints without retuning, etc. It is achieved by implementing, in FLC, a classical control strategy and an adaptation mechanism to compensate for the dynamic changes in the system. This paper deals with the detail issue for the improvement of microprocessor based design and implementations of the heating chamber temperature maintenances on practical demand and finally focuses the performance of this system to other environmental conditions in various systems.

Design and analysis of a new photonic crystal fiber for fiber based sensor applications

This monograph explores a new photonic crystal fiber (PCF) design on triangular lattice (TL) pattern for tailoring ultra flat chromatic dispersion near-zero level with high birefringence. The guiding properties of the TL-PCF are defined by applying anisotropic perfectly matched layer (PML) absorbing boundary in the finite element method (FEM). Our proposed TL-PCF is suitable for the application of highly birefringent fiber and fiber based sensors as the design offers high birefringence of 0.006±0.002 and ultra flattened near zero level dispersion of 0±2 ps.nm-1.km-1 for the bandwidth of 1.25 to 1.7 μm. The covering bands are O+E+S+C+L+U in the infrared (IF) region for the 2nd and 3rd windows.

Transmission Characteristics of Circular Ring PCF and Octagonal PCF: A Comparison

This paper presents the chromatic dispersion, effective area and confinement loss in circular ring photonic crystal fibers (CPCFs) in comparison to the octagonal PCFs (OPCFs). The finite difference method (FDM) with perfectly matched boundary layers (PML) is used to analyze the dispersion and leakage properties. It has been shown through numerical simulation results that, for the same parameters CPCFs have lower chromatic dispersion and relatively larger effective area than that of the octagonal PCFs with the same propagation loss.

Management of residual dispersion of an optical transmission system using octagonal photonic crystal fiber

Abstract. An octagonal photonic crystal fiber (O-PCF) for numerical structure design and analysis of some particular properties are presented in this paper. The proposed design is suitable for residual dispersion compensation (RDC) with polarization maintaining (PM) applications as it offers extremely high-negative flattened average chromatic dispersion (DT) and absolute dispersion variation (ΔD) of around −(708±10)  ps nm−1 km−1 and average high birefringence (B) of the order 10−2 for the wavelength limits of 1.46 to 1.67  μm (bandwidth of 210 nm that covers S+C+L+U bands in the infrared region of the optical third window). In addition, it exhibits very low confinement loss of 10−3.5 to 10−2.5  dB/m for that bandwidth. Moreover, to evaluate the sensitivity of the fiber properties (DT and B) during fabrication, ±0.02  μm variation in the optimum parameters is also studied.

Design of a dispersion flattened germanium doped silica modified hexagonal photonic crystal fiber with ultra low confinement losses

This paper presents an optimum design for dispersion managed photonic crystal fibers with low confinement losses. The COMSOL multi-physics 4.2 software is used as the simulation tool. According to simulation, a five-ringed modified hexagonal photonic crystal fiber (MH-PCF) having germanium (Ge) doped silica core can be designed with a low confinement loss at 1550 nm of the order 1.026×10-14 dB/km with simultaneously nearly-zero ultra-flattened chromatic dispersion of 0 ± 0.35 ps/nm/km in a wavelength range of 1.30 to 1.65 μm as well as large effective area in a wide range of wavelengths. The fiber having a modest number of design parameters is suitable for wavelength division multiplexing (WDM) system.

Dispersion Tolerance of Various Photonic Crystal Fibers

Chromatic dispersion characteristics of optical fibers with near zero magnitude and slope is very important for such applications as optical transmission systems, dispersion compensation, and nonlinear optics. Theoretically-designed dispersion characteristics require a tolerance of ±2% to ensure reasonable dispersion accuracy during the fabrication process. This article describes dispersion accuracy of various photonic crystal fibers due to changes in dimension of the first ring of air-holes, as it is mostly responsible for the slope characteristics of the dispersion curves. It is demonstrated that for identical design parameters octagonal photonic crystal fibers can assume better dispersion accuracy in comparison to other configurations, such as hexagonal photonic crystal fibers, square photonic crystal fibers, and decagonal photonic crystal fibers in a 1.20 to 1.70 µm wavelength. Dispersion tolerance due to the dimension of the first ring of an optimized octagonal photonic crystal fiber is also investigated. It is found that the optimized octagonal fiber can also assume promising dispersion tolerance to dimension of the first ring with ultra-flattened characteristics in the 1.20 to 1.70 µm wavelength range.