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13Development of Improved Spectral Characteristics of Fiber-Optic Communication
Systems
Z. Khakimov, B.N.Rakhimov Tashkent University of Information Technologies (Tashkent, Uzbekistan)
Abstract - Research and development of methods of regeneration of optical signals for restoration of their spectral characteristics and strengthening's of intensity by means of AOTF.
Keywords - Fiber-optical systems of transfer (FOST), an optical fiber, superficial - acoustic wave and acousto-optic tunable filter (AOTF)
In recent years, there is an urgent need to conduct extensive research and development of practical methods for the regeneration of optical signals Fiber-optical systems of transfer (FOST) using acousto-optic filter (AOF). It is known that due to the loss fiber optic strongly distorted spectral characteristics, the signal weakens and decreases the transmission speed.
This article is devoted to investigation of the possibilities for improving the parameters of fiber-optical communication lines (FOCL), expanding their potential, increasing the speed and quality of information transmission, increasing the capacity to fundamental limits, testing and application of FOST and FOCL in radio systems.
The need to improve the spectral characteristics of the real FOCL becomes particularly relevant at the present time. Therefore, research on methods and apparatus for measuring and improving them, using modern technology and elements, in particular by using acousto-optic tunable filters (AOTF) has the practical importance of scientific and [1-2].
These analyzes showed that the acousto-optic tunable filter has the following characteristics:
1) The wide tuning range (200 nm);
2) Narrow band;
3) Fast switching time;
4) Most importantly, the ability to switch between any numbers of channels (operating at different frequencies) is simultaneously and independently. The lightweight set-up and amplifiers;
5) The ideal selectivity.
In addition, the use of frequency amplifiers
acousto-optic tunable filters, having a substantially rectangular amplitude-frequency characteristic, provide the ideal selectivity, good dimensions and weight and provide easy tuning and adjustment of amplifiers [3].
It was thus established that the most promising are AOTF that improve the spectral characteristics of the emitted signal. To conduct research needed to develop a specialized stand (Fig.1).
In this Fig. 1 the following elements are used:
1 - fiber optic transmitter GaAsInP based semiconductor laser X = 1,55 mm [4];
2 - crystal semiconductor laser;
3 - power supply for the laser and for amplifier of a running wave(ARW);
4 - single-mode optical fiber;
5 - microlens;
6 - singlemode connectors;
7 - crystal on the ARW coated silicon monoxide SiO;
8 - an acousto-optic tunable filter (AOTF);
9 - Strengthening-modulator block;
10 - RF coaxial cable;
11 - spectrograph;
12 - the computer;
13 - potentiometer adjustment mode mixing four frequencies;
14 - power supply for the amplifier modulator unit.
Application at this stand surface acoustic filter electrodes interdigitated configuration obtained by means of electron beam lithography, the optical waveguide with a width of 7 microns and a length of 20 mm allows the crystal to receive mode conversion to 97% and filtering to obtain the wavelength of the laser radiation 1 3 and 1.55 microns.
As a result of experimental studies on this stand following results were obtained [5]:
In Fig. 2. Bringing the original demonstration optical spectrum obtained at the input, ie, diffractometer is connected to a traveling-wave amplifier.
Fig. 1. Functional diagram of the stand with AOTF
Fig. 2. Source optical spectrum
From this spectrum shows that at a pump current 68 mA and 18 ° C. This temperature range with good approximation paints a picture of the optical spectrum of the real signal FOCL with an optical wavelength division multiplexing. We can assume that in this there are seven FOCL single-frequency laser transmitters, spaced at intervals of 2 nm in the wavelength range of 1550-1562 nm. Note that the spectral brightness at wavelengths 1552 and 1554 nm is practically zero. In real FOCL this may mean that the information is transmitted laser transmitters operating at these wavelengths is lost.
The intensity of the spectral line at a wavelength of 1560 nm, substantially less than that of the remaining spectral lines. It can be expected that further spreading of the signal in real FOCL through a cascade of several optical amplifiers information transmitted at this wavelength will either be significantly distorted at the reception, or just lost. Spectral irregularity in this case is 6.46 dB.
In Fig. 3. - Shows the optical spectrum when the amplifier and modulator blocks.
1,0
-j-1-
1550 1560 ;
Fig. 3. Optical spectrum with the included amplifier and modulator blocks
Spectral irregularity lines on this spectrum are 4.67 dB [6]. A comparison of the source of the optical spectrum (Fig. 2) and the outcome (Figure 3), we can conclude about the effectiveness of the stand for the regeneration of the optical signal linearization circuit and pass the spectral characteristics of a FOCL with an optical wavelength division multiplexing.
Designed stand can also be used to test a new generation of optical amplifiers, in particular EDFA, and acousto-optic tunable filters, and research the operation of fiber-optic communication systems with optical wavelength division multiplexing, including the modeling of optical signals FOST, exacerbating the optical signals and alignment through passage the spectral characteristics and the implementation of FOST switch one or multiple spectral channels.
Thus, the possibility of effective use of the stand for the regeneration of the optical signal linearization circuit and pass the spectral characteristics of FOCL with an optical wavelength division multiplexing.
REFERENCES
[1] Davronbek D.A, Hakeem Z.T Prospects for the use of SAW filters in modern telecommunications systems / / Fan va-talimda Ahborot communication tehnologiyalari. The Republic of the conference ilmy Amalie maruzalar tuples. 6-7 April 2006, J. Tashkent, 2006.-pp. 37-38.-II - vol
[2] Khakims Z.T. Features AOPF / / Ahborot-communication tehnologiyalari - graduate student, Master Islands iqtidorli TALABALAR ilmy -techniques konferentsiyasi maruzalar tuples. 4-5 March 2008, J. Tashkent, 2008.-p. 133.
[3] Z.T Khakims. Systematization and analysis of acousto-optic tunable filters / Fan va-talimda Ahborot communication tehnalogiyalari - doctoral student, graduate student, tadqiqotchilar, undergraduate Islands iqtidorli talabalarning Republic ilmy technician konferentsiyasi maqolalar typlami. 25-26 th March 2010. - Tashkent, 2010.-pp.33-37.
[4] Kamardin A.I., Radjabov T.D., Sharudo A.V., Formation of Erbium implanted layers in quartz glass, International Colloguium Plasma Processes, CIP -2003, Antibes, France, pp. 1.24/ 2003.
[5] Hakimov Z.T., Davronbekov D.A. Equalization of spectral characterist of optical signals by acousto-optic filters. 2007 Third IEEE/IFIP International Conference in Central Asia on Internet. The Next Generation of Mobile, Wireless and Optical Communications Networks.
]6] T.D.Razhabov, D.A.Davronbekov, Z.T.Hakimov. Spectral characteristics of optical signals using PLAYBACK AOPF / / Infokommunikatsii: Network-Technology-Solution. - Tashkent, 2008. - № 1 (5). -pp. 3-7.
Z. Khakimov, B.N.Rakhimov
Tashkent University of Information Technologies (Tashkent, Uzbekistan) Department of Radio Communication Devices and Systems.
