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The importance of uniformity to demultiplexer device fabrication for Pof based small world communication.

Introduction

Multimode optical fiber is sold every day with a specification list that includes a bandwidth value measured in MHz*km. Although multimode fiber is sold on a per kilometer basis, the desired manufacturing length is much greater than 1 km. Add to these facts that the application window for multimode fiber is generally less than 1 km, and it becomes clear that the fiber manufacturer does not measure the fiber length that will actually be deployed. Therefore, some work is required to ensure that the bandwidth measurement in the manufacturing plant will relate to the bandwidth of the fiber deployed in optical communication systems (Johnson, 2001). Instead of the bandwidth and length there is another parameter need to be concerned in Multimode communication which is the uniformity. Uniformity is define as how well the signal is distributed to the number of output port at specific wavelength. The Bandwidth.Length (BW.L) will determine the achievable distance of single optical fiber or POF but the uniformity will determine the achievable distance of optical communication when the devices are installed along the optical fiber. Nowadays many POF devices have been designed and fabricated to extend the application of POF communication. The parameters of uniformity is one of parameter used to evaluate the device performance (Ehsan, 2010; Mohammad Syuhaimi Ab-Rahman, 2011). In WDM-POF system, many transmitters with different lights colour to carry single information. For example, red light with 650nm wavelength modulated with Ethernet signal while blue, green, and yellow lights carry image information, radio frequency (RF), and television signal, respectively. As shown is Figure 1, Wavelength Division Multiplexer is the first passive device required in WDM-POF system and it functions to combines optical signals from multiple different single-wavelength end devices onto a single fiber.

Conceptually, the same device can also perform the reverse process with the same WDM techniques, in which the data stream with multiple wavelengths decomposed into multiple single wavelength data streams. The reverse process is called as de-multiplexing.

[FIGURE 1 OMITTED]

In general, POF splitter Conceptually, POF splitter has similar function, operates to couple or combine several optical data pulse as a single coupled signal. Hence, the development of wavelength division multiplexer based on POF splitter is possible.

The handmade 1xN POF splitter is an optical device, which ended by N number of POF ports, while the other side ended by one POF port. Like other typical splitter, it is also possible to work bidirectional, whereby it works from the N ports into 1 port (for coupling signal purpose), or vice versa (for splitting signals purpose). As an example, optical 1x4 splitter developed by the jointing of four PMMA POFs. Other specification for the design, the input POF is designed and fabricated to be fused taper-twisted shape. This shape enables coupling four individual optical pulse input. Each inputs and output is connected with POF connecter as shown in Figure 2 (Mohammad Syuhaimi Ab-Rahman, 2011; Mohammad Syuhaimi Ab-Rahman, 2010; Mohammad Syuhaimi Ab-Rahman, 2009).

[FIGURE 2 OMITTED]

For the filter design which able to eliminate unwanted signal and select the wavelength of the system as desired as shown in Figure 3.

[FIGURE 3 OMITTED]

Insertion Loss and Splitting Ratio Graph:

An optical splitter has two important parameters which are insertion loss and uniformity. Insertion loss is the loss of signal power resulting from the insertion of a device in a transmission line or optical fiber and is usually expressed in decibels (dB).

If the power transmitted to the load before insertion is PT and the power received by the load after insertion is PR, then the insertion loss in dB is given by,

10[Log.sub.10] [P.sub.T]/[P.sub.R] (1)

The insertion loss includes the coupler splitting loss and excess loss and is the most useful parameter for system design. The maximum and minimum insertion loss is the upper and lower limit, respectively, of the insertion loss of the coupler and applies over the entire wavelength range specified in the bandpass. The typical insertion loss is the expected value of the insertion loss measured at the specified center wavelength. Multimode couplers are measured with an equilibrium mode fill.

Uniformity is a measure on how evenly power is distributed between the output ports of the coupler. Uniformity applies to couplers with a nominally equal coupling ratio and is defined as the difference between the highest and lowest insertion loss between all of the coupler output ports, expressed in dB.

Figure 4 shows the characterization of POF splitters that have been made by machine and hand. The result shows the commercial machine made device has a good value in insertion loss but poor in the uniformity. As compare to our proposed device, the both parameters which are insertion loss and uniformity is promising. Many technique used mold and thin film technology to develop POF devices. The performance commercialized device is totally depending to the fabrication process in which the technique normally not allowed for the improvement of uniformity. With our solution the parameter such as temperature, strain force and number of twisting is the control parameter and can be interchange to achieve high performance device.

The device with excellent uniformity can be extended to perform as demultiplexer after joint together with optical filter. Here the filter is used at the end edge of fiber and the colur of the filter technically will determine the exact color of signal passing through. Figure 5 shows the two conditions of demultiplexer fabrication by using uniform (a) and not uniform (b) optical splitter. The demultiplexer based on not uniform optical splitter has failed and could not performed the demultiplexer. The fabricated device are not secured with crosstalk in which the filter play an important role to reduce leakages. The details of this mechanism is shown in Figure 5.

[FIGURE 5 OMITTED]

Result and Discussion

It is stated that splitting ratio of the developed 1xN splitter was not totally homogenous. In WDMPOF system, the homogeneity concerned as essential criteria for POF splitter as optical multiplexer in coupling multiple optical signals.

The handmade 1xN splitter has been formed based on left side of fused bundle as the prototype has lower loss in leftward light propagation. Final analysis shows that efficiency of 1xN POF splitter output has splitting ratio 25:16:31:28 % and 2.41 dB of minimum optical loss. Hence, the obtained result reveals that handmade 1xN POF splitter has great potential to be employed as an economical wavelength division multiplexer because it able to couple several different wavelengths with few main advantages that are low optical loss and low-cost. The fabricated demultiplexer based on the uniform optical splitter which operates at two wavelength is shown in Figure 6. The device enable to split two different wavelengths (green and red) with high intensity (low loss) and less crosstalk.

[FIGURE 6 OMITTED]

Reference

Ehsan, A.A. and M.K. Abd-Rahman, 2010. Acrylic-based Y-Branch Plastic Optical Fiber Attenuator. IEEE International Conference on Photonics., ICP2010-66.

Johnson, C.P., 2001. Characterizing Bandwidth/Length Uniformity in High Speed Data Communication Multimode Optcal Fiber. Lasers and Electro-Optics Society, 2001. LEOS 2001. The 14th Annual Meeting of the IEEE. pp: 863-864

Mohammad Syuhaimi Ab-Rahman, Mohd Hazwan Harun, Hadiguna, Kasmiran Jumari., 2011. The Second Generation Low Cost Fused taper (LFT) Splitters Based on POF Technology. Journal of Scientific and Industrial Research. Accepted for publication

Mohd Syuhaimi, Ab-Rahman, Hadi Guna and Mohd Hawan Harun., 2010. Fabrikasi dan Pencirian Pencerai Optik 112 Buatan Tangan Berprestasi Tinggi Berasaskan Gentian Optik Plastik diperbuat daripada Polimetil Metakrilat. Sains Malaysiana. 39(3): 459-466

Mohammad Syuhaimi, Ab-Rahman, Hadi Guna, Mohd Hazwan Harun, Mohd Saiful Dzulkefly Zan and Kasmiran Jumari., 2010. Home-Made Optical 1x12 Fused-Taper-Twisted Polymer Optical Fiber Splitters for Small World Communication. Journal of Applied Sciences Research., 6(12): 2212-2218.

Mohammad Syuhaimi, Ab-Rahman, Hadi Guna, Mohd Hazwan Harun, Saiful Dzulkefly Zan and Kasmiran Jumari., 2009. Cost-effective Fabrication of Self-made 1x12 POF-Based Optical Splitters for Automotive Application. American Journal of Engineering and Applied Science. 2(2): 252-259.

Mohd Hadi, Guna Safnal, Mohammad Syuhaimi Ab-Rahman, Mohd Hazwan Harun. 2009. Fabrication and Characterization of Optical 1x12 Fused-Taper-Twisted Polymer Optical Fiber Splitters. Journal of Optical Communication, JOC (German)., 30(1): 16-19.

Corresponding Author: Mohammad Syuhaimi Ab-Rahman, Institute of Space Science (ANGKASA) Universiti Kebangsaan Malaysia 43600 UKM Bangi, Selangor, Malaysia.

(2) Mohammad Syuhaimi Ab-Rahman, (1) Hadiguna and (1) Hazwan Harun

(1) Spectrum Technology Research Group (SPECTECH) Department of Electrical, Electronics and Systems Engineering Faculty of Engineering and Built Environment Malaysia.

(2) Institute of Space Science (ANGKASA) Universiti Kebangsaan Malaysia 43600 UKM Bangi, Selangor, Malaysia.
Fig. 4: Two different fabrication techniques for optical splitter
development. The machine made device is good in insertion loss but
the handmade device has better in uniformity and loss. Thus it
can be use for further fabrication of demultiplexer device.

                                              hand-   hand-   hand-
         comercial   comercial   comercial    made    made    made
             1           2           3         1       2       3

Port 1    -0.09        -2.25       -0.58      -9.99   -7.70   -7.72
Port 2    -6.78        -5.67       -5.52     -10.46   -7.21   -9.48
Port 3    -6.66        -6.74       -6.80     -10.81   -8.90   -9.00
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Article Details
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Title Annotation:Original Article
Author:Ab-Rahman, Mohammad Syuhaimi; Hadiguna; Harun, Hazwan
Publication:Advances in Natural and Applied Sciences
Article Type:Technical report
Geographic Code:9MALA
Date:Apr 1, 2011
Words:1518
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