Multiwavelength fiber laser in four mode fiber

Multiwavelength fiber laser is a nonlinear phenomenon that has a great potential for optical communication system. A stable triple-wavelength fiber laser in four mode fiber had been demonstrated experimentally by employing Sagnac filter in a simple close loop laser cavity. The Sagnac loop filter configuration was constructed using a 2 m of polarization maintaining fiber (PMF), a 3 dB coupler and a polarization controller. The laser is able to sustain triple-wavelength laser generation at 13.1 dBm output power of Erbium-Doped Fiber Amplifier (EDFA) as all laser wavelengths produced less than 0.25 nm fluctuation for over 20 min of unstoppable lasing operation. This laser configuration also has flexibility to perform single, dual and triple wavelength laser by controlling the EDFA output power

The Effect of Plasma-Treated Boron Nitride on Partial Discharge Characteristics of LDPE

Power supply reliability is a key factor in a country economic stability. It is contributed by the reliable power distributor via transmission lines, overhead or underground cables. However, the power cables and accessories are always exposed to pre-breakdown phenomena known as partial discharges (PD) which commonly occur in microvoids, defects or protrusions inside the insulation. To improve the performance of the cable insulation against PD, nanofillers are added into the insulating materials. However, to achieve superior performance of PD resistance, the nanofillers must be homogeneously dispersed into the polymer matrices with tightly bonded interfacial zones. Therefore, this could be achieved by employing method of surface functionalization by using cold atmospheric plasma to strengthen the filler/polymer interfaces. In view of foregoing, this study investigated the effects of surface treated boron nitride (BN) nanoparticles in Low Density Polyethylene (LDPE) on the PD characteristics by following CIGRE Method II at 7 kVrms applied voltage. The phase resolved PD characteristics were performed. The results revealed that by treating the nanofillers with cold plasma, the PD resistance of LDPE were highly achieved compared with the untreated BN nanofillers

The Influence of Nonlinearity Properties in Generating Octave-spanning Light

An efficient system for nonlinear parameter characterization in Highly Nonlinear Fiber (HNLF) is described using four wave mixing (FWM) technique, the FWM plays an important role in enhancing the spectrum development in most cases. The Nonlinear parameters like zero-dispersion wavelength (ZDW), chromatic dispersion (CD) and the non-linear coefficient of HNLF were successfully investigated using this technique. The results of this technique have been almost identical to factory specifications. By FWM technique, a CD at 1550 nm slope is obtained from 0.007 ps.nm-2km-1, ZDW of 1531 nm and nonlinear parameters of 10.7 W-1km-1

Antimicrobial activities of marine fungi from Malaysia

Copyright 2011 Elsevier B.V., All rights reserved.Peer reviewedPublisher PD

Analyzing the relationship between self-confidence in mathematics and students' characteristics using multinomial logistic regression

This study investigates the relationship between self-confidence and achievement among Malaysian students using multinomial logistic regression and the data are from TIMSS 2007. Although, in general, Malaysian students had low self-confidence in learning mathematics, their performance in mathematics at the international level is higher as compared to some countries with high level of self-confidence. This study also found that, besides mathematics achievement, there are four other factors that separate the level of self-confidence among Malaysian students. These factors are gender of students, students' aspiration, use of computer for school work, having teachers who want students to do their best

Degeneration of four wave mixing in 500 m step index two mode fiber

Four wave mixing (FWM) in two-mode fiber was experimentally demonstrated at 24.7 dBm of output Erbium doped fiber amplifier (EDFA). The 0.5 km two mode fiber in laser cavity enhances the performance of four wave mixing by suppressing the homogenous broadening effect in erbium-doped fiber and perform a stable oscillation. At output EDFA approaches to 24.7 dBm, FWM is generated and the increasing of output EDFA induced the optical signal to noise ratio (OSNR) of all laser peaks

Electrical Capacitance Tomography (ECT): an improved sensitivity distribution using two-differential excitation technique

In this study, we propose the use of the two-differential potential excitation technique in an Electrical Capacitance Tomography (ECT) system to improve: (1) the non-uniform sensitivity distribution caused by the non-uniform potential distribution in the central area; and (2) the nonlinear relation between capacitance and material permittivity. A simulation of a 16-segmented ECT system is developed using COMSOL Multiphysics to observe the changes of the inter-electrodes capacitances and the permittivity of the dielectric material when two differential excitation potentials are injected. Generated phantoms and measured values are presented. An experiment using the real system is also carried out to verify the simulations results. By using this technique, it was shown that the relationship between the capacitances measured from inter-electrodes and the permittivity became more linear. In addition, potential distribution is increased in the central area indicating an increase in the sensitivity distribution in the central area. The use of this technique increases the level of detected signals and improves the SNR (signal-to-noise ratio) as compared to those achieved using standard single-voltage source methods

Three Level Thoracolumbar Spondylectomy for Recurrent Giant Cell Tumour of the Spine: A Case Report

Giant cell tumour (GCT) is a benign tumour but can be locally aggressive and with the potential to metastasise especially to the lungs. Successful treatments have been reported for long bone lesions; however, optimal surgical and medical treatment for spinal and sacral lesions are not well established. In treating spinal GCTs, the aim is to achieve complete tumour excision, restore spinal stability and decompress the neural tissues. The ideal surgical procedure is an en bloc spondylectomy or vertebrectomy, where all tumour cells are removed as recurrence is closely related to the extent of initial surgical excision. However, such a surgery has a high complication rate, such as dura tear and massive blood loss. We report a patient with a missed pathological fracture of T12 treated initially with a posterior subtraction osteotomy, who had recurrence three years after the index surgery and subsequently underwent a three level vertebrectomy and posterior spinal fusion

5G coupler design for intelligent transportation system (ITS) application

Aiming to achieve 3-dB coupling, operating in fifth generation (5G) technologies, this paper introduces a new design of tight coupling coupler that will be operated in 5G technologies. Two stubs and two slots have been implemented into the 3-dB coupler design in order to achieve impedance matching between the ports and to give better coupling performances, respectively. Moreover, a study on the stubs' and slots' effects towards the S31 of the 3-dB coupler has also been presented in this paper. The proposed coupler is designed on Rogers RO4003C substrate. The simulation results and the analytical study on the stubs and slots implementation show that both stubs and slots affect the performance of the coupling coefficient

Passively mode-locked fiber laser by utilizing TTG film on a D-shaped fiber as a saturable absorber

In this paper, we propose a mode-locked fiberlaser by utilizing single layer Trivial Transfer Graphene film (TTGF) as a saturable absorber (SA). The SA was deposited on the top of a side-polished D-shaped fiber. The SA was then integrated in the ring cavity configuration, with a clockwise light propagation. Three distinctive 2 m erbium doped fibers (EDFs) those are Metro-Gain15 EDF, Iso-Gain6 EDF and Iso-Gain12 EDF were used as gain media, interchangeable in the experiment. From the results, the Metro-Gain15 EDF gives the most proficient gain medium on generating a passively mode-locked fiber laser. The Metro-Gain15 Erbium doped mode-locked Laser was successfully producing ultrashort pulse with 8 nm spectral band-width, 13 MHz of repetition rate and 915 fs pulse duration. These outcomes demonstrated that TTGF deposited on the D-shaped fiber is a suitable component as an SA to produce a stable output passively mode-locked fiber laser for many optical fiber applications