Abu Bakar Mohammad

Recent Progress in Optical Chemical Sensors

Optical chemical sensors have promoted escalating interest in the determination of various pollutants in the environment, which are creating toxicity and may cause serious health problems. This review paper focuses particularly on the recent progress and developments in this field; the working principles and basic classes of optical chemical sensors have been briefly described.

A survey on access technologies for broadband optical and wireless networks

The bandwidth demand of telecommunication network is growing rapidly due to the increasing number of technology-intelligent end-users. The emerging optical and wireless access networks are continuously competing with each other to provide these requirements for the end-users. The optical access networks provide huge data rate and long-distance link, but it is less ubiquitous. The wireless access networks provide flexible and ubiquitous communication with a low deployment cost. However, its deployment scalability is limited by the spectrum and range limitations. The hybrid wireless optical broadband access network (WOBAN) is a powerful combination of optical backhaul and wireless front-end to contribute to a good scalability, cost effective and flexible communication system. This paper reviews the key enabling access technologies and progress advancements of these networks. The emerging optical and wireless access technologies are also presented and compared.

Analytical modeling for determination of pull-in voltage for an electrostatic actuated MEMS cantilever beam

A new analytical model has been developed for determining the pull-in voltage of an electrostatic actuated microelectromechanical system (MEMS) cantilever beam. The model takes into account the beam curvature caused by residual stress or stress gradient in the beam material. It can be used to model straight, curled and beam with mixture of straight and curled sections. Modeling result has been compared with published work of other researchers as well as with experimental measurement of this work and is found to be accurate.

MMI-MZI Polymer Thermo-Optic Switch With a High Refractive Index Contrast

The 2 x 2 MMI-MZI polymer thermo-optic switch in a high refractive index contrast (0.102) with a new structure design is realized. The fabrication was done using standard fabrication techniques such as coating, photolithography, and dry etching. A crosstalk level of dB has been achieved. Meanwhile, the extinction ratio of 28.6 dB has been achieved in this device. The polarization-dependent loss of 0.3 dB was measured at 1550 nm wavelength. In terms of wavelength dependency, the device shows a good performance within C-band wavelength with vacillation of the insertion loss value around 0.88 dB. The power consumption of 1.85 mW was measured to change the state of the switch from the cross to bar state. The measured switching time was 0.7 ms.

Recent development on time and wavelength-division multiplexed passive optical network (TWDM-PON) for next-generation passive optical network stage 2 (NG-PON2)

The second stage of next-generation passive optical network (NG-PON2) based on time and wavelength division multiplexed passive optical network (TWDM-PON) was proposed by a telecommunication group research to enhance the performance of broadband access networks. TWDM-PON was selected as the best candidate for NG-PON2 solution because of its ability to support the NG-PON2 requirements, such as enhanced bandwidth capacity, 40Gb/s, and coexistence with previously existing generations without any change to optical distribution network (ODN). This paper reviewed the recent progress carried out on a TWDM-PON system configuration, with emphasis on tunable transmitter and receiver optical network unit (ONU) in terms of the amount of tuning range reported in exploiting the wavelength plan provided with cost efficiency. The speed of data rate transmitted on the downstream and upstream links between optical line terminal (OLT) and ONU with the way of stacking approach in NG-PON2 is reviewed. In addition, the power system budget is reviewed to determine the number of users allocated with the system with each transmission allowed.

Review on system architectures for the millimeter-wave generation techniques for RoF communication link

Generation of millimeter-wave (mm-wave) signal for radio over fiber (RoF) currently being investigated and studied by many researchers due to the demand of the mm-wave band for future communication system mostly in wireless local area networks (WLANs) applications. RoF is a system where high microwave frequency signals are delivered through optical fiber between the central station (CS) and the base stations (BSs). The use of optical fiber for signal distribution in mm-wave radio communication systems has been widely investigated, since they provide high bandwidths and small cell sizes (picocell). They also offer the potential for the low cost infrastructure needed to develop broadband mobile services. This paper will explain the whole picture of RoF technology followed by RoF link configurations where radio frequency (RF) signal can be transmitted directly over fiber either at the RF or intermediate frequency (IF) signals. The review mainly focuses on the mm-wave generation techniques for radio over fiber including: optical heterodyning, external modulation, optical transceiver, and up- and down-conversion.

Multimode interference optical splitter based on photodefinable benzocyclobutene (BCB 4024-40) polymer

1×2 and 1×3 planar optical splitters based on Benzocyclobutene (BCB 4024-40) polymeric material are demonstrated for the first time. The devices are designed based on symmetric interference and fabricated on BK7 glass substrates with a thin layer of SiO2 as cover. A cost-effective chemical etching technique is used in the fabrication process to take advantage of the photosensitivity of the polymer. The waveguide loss was measured using the cutback method to be 3.5 dB/cm. The splitting uniformity is better than 0.02 and 1.5 dB at 1550-nm optical wavelength for the 1×2 and 1×3 splitters, respectively.

HBT Optoelectronic Mixer Design for Radio over Fiber System

Radio over fiber (RoF) system is the solution for the providing highly reliable communication service. This system is characterized by having both a fiber optic link and free-space radio path to exploit the synergy of two complementary technologies; the broadband mobile wireless access and fixed optical access. Optoelectronic mixing is required in RoF systems to detect the RF modulated optical signal and perform frequency up-conversion. In this work, three-terminal InP/InGaAs HBT with optical access has been used as the optoelectronic mixer (OEM) for front-end RoF optical receiver configuration. Thus in this configuration, the photodetection and frequency conversion can be achieved in p-i-n photodiode and HBT device, which considerably simplify the conventional method. The RoF OEM was successfully simulated using a nonlinear microwave simulator to perform harmonics balance analysis, which represented actual photodetection model and nonlinear dynamic optoelectronic mixing behavior. In this paper we reported the - 5.2 dB maximum internal mixing efficiency for 400 MHz IF modulated signal to 3.4 GHz upconverted RF signal with LO power is -2dBm, and that agreed with conventional theoretical analysis. In this article, the theory of operation, the device structure of the RoF OEM and its characteristic will be presented.

Polymeric Optical Splitter Based on Multimode Interference Mechanism

A 1 times 2 and 1 times 3 planar optical splitter based on BenzoCyclobutene (BCB 4024-40) polymeric material is proposed. The device is designed based on symmetric interference mechanism, utilizing a BK7 glass as a substrate and thin layer of SiO2 as a cover. Simulation results show that the splitting uniformity is better than 0.5 dB at 1550 nm optical wavelength.

A space dilated lightwave network - a new approach

The space dilation concept for reducing crosstalk in Ti:LiNBO/sub 3/, directional coupler-based photonic switches operating at a single wavelength is applied using a new approach. A novel switch architecture is proposed for unicast nonblocking photonic switching networks to fully exploit the advantages of this method. Some properties of the switch architecture are derived and analyzed. The performance of the switch is also discussed and compared with other well-known network architectures.