N. A. Cholan

Size Reduction and Multiband Characteristic Using Koch Fractal Dipole

The Koch fractal dipole antenna is designed, simulated and fabricated for operating at 900MHz frequency band. By using Koch fractal antenna mathematic equation and some consideration, the desired resonant frequencies can be achieved. The designed antenna is started with developing microstrip dipole antenna for the same frequency operation. The size of Koch fractal dipole is reduced around 40% compactness compared to microstrip dipole. A multiband characteristic is investigated until third iteration with identication angle, thetas = 60deg trace width, W = 1mm and fabricate onto FR-4 substrate using SMA connector

Enhanced multiwavelength generation in Brillouin fiber laser with pump noise suppression technique

A new multiwavelength Brillouin fiber laser (BFL) that provides a large number of Stokes lines with improved optical signal-to-noise ratio has been proposed and demonstrated. The BFL cavity is only formed by a nonlinear fiber loop mirror (NOLM) with 500 m long highly nonlinear fiber (HNLF). The BFL with improved performance is based on the suppression of the Brillouin pump noise floor utilizing a narrow tunable bandpass filter. The generation of Stokes lines covering up to a 33.67 nm wavelength range is achieved by setting the Brillouin pump signal within the HNLFs zero dispersion wavelength and with power of 250 mW. This is owing to the combination of the stimulated Brillouin scattering and four-wave mixing effect in the NOLM structure.

Comparison of detection techniques in optical CDMA access network for point to multipoint configuration

In this paper, we are proposing a detection scheme known as spectral direct detection technique implemented with fiber bragg grating (FBG) act as encoder/decoder. This FBG based is used to encode and decode the spectral amplitude coding namely modified double weight (MDW) code in optical code division multiple access (OCDMA). This code is used due to its flexibility where its weight can be any even number that greater than two. Moreover, it can maintain the cross-correlation parameter equal to one. The performance of spectral direct detection technique against AND-subtraction technique which is both implemented with FBG based encoder/decoder is compared via simulation in downstream and upstream access network at point to multipoint (P2MP) configuration. The simulation will be carried out using OptiSystem version 6.0 and the performance is characterized through bit error rate (BER) and power received at various bit rate.

Analysis and design of micro-ring resonator as an add drop filter for Coarse Wavelength Division Multiplexing (CWDM) application

An optimal micro-ring resonator with laterally coupled waveguides is presented in this paper. The proposed resonator is optimized to work as an add-drop filter for coarse wavelength division-multiplexing (CWDM) system which follows ITU-T G.694.2 standard. Optimized micro-ring resonator should have wide free spectral range (FSR) and high quality factor (Q) to accommodate many channels and high extinction ratio (ER) to avoid crosstalk. From the 3D structure rib waveguide, we converted it to the effective 2D structure. By using the excitation pulse as an input signal, this resonator was simulated at CWDM wavelength 1.55 mum. With 0.2 mum wide ring waveguide cavities and by varying radius of microring, we found out that the optimal radius for the resonator is 4.5 mum which can have Q in several hundred and free spectral range of 30 nm. Based on this optimal radius, the resonator was simulated with various width of waveguide to get the optimized performance. With width of waveguide 0.35 mum, the FSR can be as wide as 30 nm and Q of nearly 1550.

Performance of the optical spectrum CDMA systems in FTTH access network

Double Weight (DW) code is presented here to support fiber-to-the-home (FTTH) access network in point-to-multipoint (P2MP) applications. This code with basic fixed weight of 2 possess ideal cross correlation properties, that are important characteristics in spectral encoding OCDMA system since these can eliminate multiple user interference and can reduce noise. The performance of DW code against Hadamard code is compared through simulation by using OptiSystem version 2.2. The performances were characterized through bit error rate (BER) against number of user for two network designs. One is without erbium doped fiber amplifier (EDFA) and another one is with the EDFA for P2MP network. It is found that DW code is better than Hadamard code for all simulation results at bit rates of 622 Mbps, 1.25 Gbps and 2.5 Gbps.

Multiwavelength Fiber Laser based on Bidirectional Lyot Filter in Conjunction with Intensity Dependent Loss Mechanism

With the rapid growth of communications via the Internet, the need for an effective firewall system which has not badly affect the overall network performances has been increased. In this paper, a Field Programmable Gate Array (FPGA) -based firewall system with high performance has been implemented using Network FPGA (NetFPGA) with Xilinx Kintex-7 XC7K325T FPGA. Based on NetFPGA reference router project, a NetFPGA-based firewall system was implemented. The hardware module performs rule matching operation using content addressable memory (CAM) for higher speed data processing. To evaluate system performance, throughput, latency, and memory utilization were measured for different cases using different tools, also the number of rules that an incoming packet is subjected to was varied to get more readings using both software and hardware features. The results showed that the designed firewall system provides better performance than traditional firewalls. System throughput was doubled times of the one with Linux-Iptables firewalls.

Numerical analysis of signal recycling in multiwavelength Brillouin-erbium fiber laser

The incorporation of signal recycling in a multi-wavelength Brillouin-erbium fiber laser (MBEFL) is studied numerically in this work. The Brillouin pump (BP)/Stokes lines are solved numerically for both the incident and reflected BP/Stokes signal. The simulation results suggest that the number of Stokes lines is optimized when the BP power is set at 2.5 and 3 mW for 300 mW pump power. Disappearance of competition with self-lasing cavity modes and depletion of excited erbium ions are factors that contribute to the optimized BP value.

FILTSoft: A computational tool for microstrip planar filter design

Filters are key component of any communication system to control spectrum and suppress interferences. Designing a filter involves long process as well as good understanding of the basic hardware technology. Hence this paper introduces an automated design tool based on Matlab-GUI, called the FILTSoft (acronym for Filter Design Software) to ease the process. FILTSoft is a user friendly filter design tool to aid, guide and expedite calculations from lumped elements level to microstrip structure. Users just have to provide the required filter specifications as well as the material description. FILTSoft will calculate and display the lumped element details, the planar filter structure, and the expected filter’s response. An example of a lowpass filter design was calculated using FILTSoft and the results were validated through prototype measurement for comparison purposes.Filters are key component of any communication system to control spectrum and suppress interferences. Designing a filter involves long process as well as good understanding of the basic hardware technology. Hence this paper introduces an automated design tool based on Matlab-GUI, called the FILTSoft (acronym for Filter Design Software) to ease the process. FILTSoft is a user friendly filter design tool to aid, guide and expedite calculations from lumped elements level to microstrip structure. Users just have to provide the required filter specifications as well as the material description. FILTSoft will calculate and display the lumped element details, the planar filter structure, and the expected filter’s response. An example of a lowpass filter design was calculated using FILTSoft and the results were validated through prototype measurement for comparison purposes.

The influence of dispersion slope to the higher-order dispersion coefficients for highly-nonlinear fibers

The highly-nonlinear fiber is the ideal gain medium for many applications particularly because its dispersion can be easily engineered. However, the modification of the fiber dispersion will affect the higher-order dispersion coefficients. Hence, this paper investigates the effect of highly-nonlinear dispersion-shifted fiber dispersion profile on the higher-order dispersion coefficients which are the fourth-order and sixth-order dispersion coefficients. The dispersion profile was modified by varying the slope at zero-dispersion wavelength. The fourth-order dispersion coefficient exhibits changes from positive to negative value as the slope at zero-dispersion wavelength is getting higher. Meanwhile, sixth-order dispersion coefficient remains with the positive value even though it shows the reduction as the slope is increased, however it will eventually become negative when the dispersion is high enough. In short, the values of both fourth-order and sixth-order dispersion coefficients at zero-dispersion wavelength decrease when the slope increases.At the request of all authors of the paper, an updated version of this article was published on 13 October 2017. The original version supplied to AIP Publishing had an incorrect affiliation for R. Talib. The affiliation for R. Talib was changed from 3Shiraz University of Technology to 1Universiti Tun Hussein Onn Malaysia. This has been corrected in the updated and re-published version.The highly-nonlinear fiber is the ideal gain medium for many applications particularly because its dispersion can be easily engineered. However, the modification of the fiber dispersion will affect the higher-order dispersion coefficients. Hence, this paper investigates the effect of highly-nonlinear dispersion-shifted fiber dispersion profile on the higher-order dispersion coefficients which are the fourth-order and sixth-order dispersion coefficients. The dispersion profile was modified by varying the slope at zero-dispersion wavelength. The fourth-order dispersion coefficient exhibits changes from positive to negative value as the slope at zero-dispersion wavelength is getting higher. Meanwhile, sixth-order dispersion coefficient remains with the positive value even though it shows the reduction as the slope is increased, however it will eventually become negative when the dispersion is high enough. In s...

Self-seeded four-wave mixing cascades utilizing fiber Bragg grating

Utilizing fiber Bragg grating (FBG), we demonstrate self-seeded four-wave mixing (FWM) cascades. Larger FWM cascades are produced at higher erbium-doped fiber amplifier (EDFA) output power using a simple scheme. Six channels are generated at the EDFA output power of 252.35 mW. The separation gap of selective dual wavelength is designed at 1.6 nm, following to the wavelength separation of the FBGs used.