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1

Asymmetric Y-branch plastic optical fiber coupler

Ehsan A. A., Shaari S.

Optica Applicata

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2011

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Vol. 41, nr 4

807--816

EN

An acrylic-based asymmetric Y-branch plastic optical fiber (POF) coupler has been developed. The optical device is based on a Y-branch coupler design with a middle high index contrast waveguide taper and open space region for output fiber displacement. The middle waveguide taper is constructed on the acrylic block itself without using any additional optical waveguiding medium injected into the engraved taper region. The waveguide taper allows light rays to propagate by total internal reflection and this is achieved by having the material surrounding the waveguide taper to be of a lower refractive index (RI) than that of acrylic (RI of acrylic is 1.49). The area surrounding the waveguide taper has been designed in such a way that it is surrounded by an open air with an RI of 1.0. The high index contrast structure enables large splitting angle and shorter device length. Input and output POFs are inserted into this device structure in such a way that they are passively aligned to the middle waveguide taper structure. A simple attenuation technique based on lateral displacement of two fibers has been proposed and presented for the non-symmetrical coupling ratios. Numerical analysis has been made on the lateral displacement of the output fibers which shows that the device is able to generate non-symmetrical coupling ratios. A simple relationship between the coupling ratios and output fiber separation has been obtained. Device modeling has been performed using non-sequential ray tracing technique on the Y-branch coupler performing as a simple 3 dB coupler with excess loss of 1.83 dB and a coupling ratio of 50:50. The non-symmetrical coupling ratios of the device have been simulated by varying the lateral displacement of one output fiber from 0.1 mm to 4.4 mm. The results for the coupling ratios against the fiber displacement have been obtained and show how the device can be operated as an asymmetric Y-branch POF coupler.

2

Optical CDMA system parameters limitations for AND subtraction detection scheme under enhanced double weight (EDW) code based on simulation experiment

Hmud I. S., Hasoon F. N., Shaari S.

Optica Applicata

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2010

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Vol. 40, nr 3

669--676

EN

The work in this paper is a simulation experiment performed by a computer program to determine the OCDMA system parameters limitations. The system was built up with LED light source in the transmitter with filters to construct the code where the receiver is constructed based on AND-subtraction detection scheme. The system was designed to be compatible with the enhanced double weight (EDW) code, passive optical network (PON), P2P network connection and fiber to the home (FTTH) topology. Five system parameters were considered in this work: the number of users, the transmission distance, the bitrate, the chip spacing and the transmitted power. Optisys 6.0 software program was used as a simulator; the simulator considered the entire practical effects in the system, like nonlinearities, attenuation in the fiber and dispersion. This paper shows that for sufficient system performance parameters (BER ? 1×10–9, Q ? 6) the system can stand for the maximum number of 3 users, the maximum distance of 21 km and the minimum chip spacing of 0.2. The system also shows that it cannot work for any number of users or any distance without the amplifier.

3

AND-subtraction detection modified SNR equation for optical CDMA systems in PON applications

Hmud I. S., Hasoon F. N., Hatim F. A., Zahid A. Z. G., Shaari S.

Optica Applicata

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2010

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Vol. 40, nr 1

49--55

EN

In this paper, AND-subtraction detection scheme compatible with OCDMA system and EDW code was simulated. The aim of the simulation is to adjust the AND-subtraction detection SNR equation for better accuracy in passive optical network (PON) applications. The simulation is performed by (optisys 06) software. The software considered the entire possible practical effects during implementation, such as dispersion, nonlinear effect of the fiber and attenuation of the fiber. The simulation results compared to the analytical results were based on SNR and BER mathematical equations. The comparison shows that the analytical equation should be modified so that the received power (Psr) be more accurate for PON applications.

4

The study of the good polishing method for polymer SU-8 waveguide

Ab-Rahman M. S., Ab-Aziz F., Azura N. A., Arif M., Zan S. D., Mustaza S. M., Ehsan A. A., Shaari S.

Optica Applicata

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2009

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Vol. 39, nr 3

459-465

EN

This research focused on polish characteristic of polymer based waveguides. The aim of the research was to show how polishing parameters affect the cut length of the end surface of SU-8 polymer on silicon and to detemine the best parameters for polishing SU-8 polymer. Then, four samples were used for characterizing the polishing of polymer. Each sample was polished with the same rotation and sandpaper size but with different rotational speed. The experiment result shows that the best rotational speed for polishing polymer SU-8 sample on silicon is 200 rpm.