Rahmat Talib

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.

Students paperwork tracking system (SPATRASE)

This paper focused on a system for tracking the status of the paperwork using the Near Field Communication (NFC) technology and mobile apps. Student paperwork tracking system or known as SPATRASE was developed to ease the user to track the location status of the paperwork. The current problem faced by the user is the process of approval paperwork takes around a month or more. The process took around a month to get full approval from the department because of many procedures that need to be done. Nevertheless, the user cannot know the location status of the paperwork immediately because of the inefficient manual system. The submitter needs to call the student affairs department to get the information about the location status of the paperwork. Thus, this project was purposed as an alternative to solve the waiting time of the paperwork location status. The prototype of this system involved the hardware and software. The project consists of NFC tags, RFID Reader, and mobile apps. At each checkpoint, the RFID...

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...

Analysis and design of optimal demultiplexer based on Mach-Zehnder interferometer for CWDM application

Optimal design of planar circuit demultiplexer based on Mach-Zehnder interferometers and their cascaded forms are presented. A demultiplexer is designed for each two and four channels (wavelengths) respectively for coarse wavelength division multiplexing (CWDM) application which follows ITU-T G.694.2 standard. Optimized demultiplexer should have high transmission to get high power efficiency and low cross talk to avoid signal degradation. An analytical equation is presented to calculate the length difference (DeltaL) between the two arms of a Mach-Zehnder interferometer to produce different phase shift. Based on the length difference (DeltaL) calculation, Mach-Zehnder interferometer for different wavelengths is designed. Directional coupler is analyzed in such a way that it can split the power equally. Coupled mode theory (CMT) and beam propagation method (BPM) is used as an analytical and numerical method respectively. Performance comparisons in terms of transmission, cross talk and 3 dB bandwidth are implemented for the demultiplexer. Transmission (dB) as high as -0.74 dB and cross talk as low as -21.06 dB have been obtained for four channel demultiplexer at wavelength, lambda = 1470 nm. A 3 dB bandwidth of 14nm has been recorded as well, which satisfies the requirement set by ITU-T G.694.2 which is 20 nm. Qualitative agreement between beam propagation method (BPM) and calculation based on coupled mode theory (CMT) has been achieved for each two and four channels demultiplexer respectively.