The main impediments for long distance signal transmission in the fibre optic system, especially the radio over fibre (RoF) system, are the chromatic dispersion and signal power attenuation. Additionally, the power consumption in the laser diode and optical amplifiers affect the signal transmission costs; however, it is lower than in a wireless system. Therefore, decreasing the power consumption and chromatic dispersion and increasing the data bit rate in RoF are the demands for present and future fibre optic system technology. In order to increase the signal transmission distance and improve the frequency spectrum, we study in this paper a mobile Worldwide Interoperability for Microwave Access (WiMAX) signal transmission over RoF via a triple symmetrical dispersion system. The combination of three different fibres - single mode fibre (SMF), dispersion compensating fibre (DCF) and chirped fibre Bragg grating (CFBG) - is used to transmit a 120Mbps mobile WiMAX scalable Orthogonal Frequency Division Multiple Access (OFDMA) signal with 3.5GHz carrier frequency and 20MHz bandwidth over a RoF system. To compensate the dispersion, the SMF and DCF are employed and specifically the high reflector CFBG is applied to reduce signal power loss. In our study, the WIMAX signal is transmitted through a triple symmetrical dispersion system consisting of 2xDCF (20 km) and 2xSMF (100 km) connected to SMF (24 km) and CFBG. Simulation results clearly indicate that the limited signal transmission length and data bit rate in the RoF system, caused by fibre attenuation and chromatic dispersion, can be overcome by the combination of SMF, DCF and CFBG. The transmission distance in the fibre is extended to 792 Km, SNR and OSNR are highly satisfactory; simultaneously the power consumption is decreased.
Table of Contents
I. Introduction
II. Related Work
III. Theory and Analyses
IV. System Discription of WiMAX over RoF
V. Result and Discussion
VI. Conclusion
Research Objectives and Core Topics
This paper aims to increase the transmission distance of WiMAX signals over Radio over Fibre (RoF) systems while simultaneously reducing power consumption and maintaining signal quality. The research addresses the challenges of chromatic dispersion and attenuation in optical fibre by employing a triple symmetrical dispersion compensation method involving Single Mode Fibre (SMF), Dispersion Compensating Fibre (DCF), and Chirped Fibre Bragg Grating (CFBG).
- Analysis of chromatic dispersion in fibre optic communication systems.
- Implementation of a triple symmetrical dispersion compensation configuration (SMF, DCF, CFBG).
- Performance evaluation of WiMAX-OFDMA signal transmission over extended distances (792 km).
- Optimization of CFBG chirp length to enhance Optical Signal-to-Noise Ratio (OSNR).
- Investigation of system power budget and spectral efficiency in RoF environments.
Excerpt from the Book
III. THEORY AND ANALYSES
Dispersion is a highly important factor due to the effect on the bit rate. There are three types of dispersions: material dispersion, also known as chromatic dispersion, is caused by the fact that the refractive index of the fibre medium varies as a function of wavelengths, waveguide dispersion depends on geometrical characteristics like shape, design and chemical composition of the fibre core and finally, intermodal dispersion, which is related to the fact that the light is not transmitted as a single beam [18].
Accordingly, chromatic dispersion emerges because of variable frequency components and also signals at differing wavelengths move at different velocities due to the refractive index. It has the following units of measurement: ps/nm/km, where nm is the spectral width of the pulse, ps refers to the time spread of the pulse and km refers to the fibre length. The chromatic dispersion of SMF is 16 ps/ nm/km at 1550 nm and 17ps/nm/km at 1552nm, and can be expressed as follows [19]:
Summary of Chapters
I. Introduction: This chapter introduces the growing demand for mobile WiMAX and explains the benefits of using Radio over Fibre (RoF) systems to overcome signal transmission limitations caused by attenuation and chromatic dispersion.
II. Related Work: This section reviews existing research on RoF technology, EVM measurements in fibre links, and various transport systems designed to improve bit error rates (BER) over long-distance fibre spans.
III. Theory and Analyses: This chapter details the physical principles of fibre dispersion, categorizing it into material, waveguide, and intermodal dispersion, while providing mathematical expressions for calculating transmission distance limitations.
IV. System Discription of WiMAX over RoF: This section describes the proposed simulation setup, including the use of an MZM modulator, the integration of SMF/DCF/CFBG components, and the specific parameters for the 120 Mbps mobile WiMAX-OFDMA signal.
V. Result and Discussion: This chapter presents the simulation outcomes, demonstrating that the triple symmetrical dispersion compensation method successfully extends the transmission distance to 792 km with satisfactory SNR and OSNR.
VI. Conclusion: This chapter summarizes the study, confirming that the proposed method effectively controls chromatic dispersion and power consumption, achieving a significant increase in transmission distance for broadband WiMAX systems.
Keywords
Worldwide Interoperability for Microwave Access, WiMAX, Radio over Fibre, RoF, Dispersion Compensating Fibre, DCF, Chirped Fibre Bragg Grating, CFBG, Single Mode Fibre, SMF, Chromatic Dispersion, OFDMA, Signal Transmission, OSNR, SNR
Frequently Asked Questions
What is the primary focus of this research?
The research focuses on optimizing the transmission of WiMAX-OFDMA signals over long-distance Radio over Fibre (RoF) systems by mitigating signal distortion and power loss.
What are the main impediments to long-distance signal transmission in RoF?
The main impediments are chromatic dispersion and signal power attenuation, which limit the data bit rate and the reachable transmission distance.
What is the core objective of the proposed system?
The primary objective is to increase the signal transmission distance to 792 km while improving the frequency spectrum and maintaining low power consumption.
Which components are used for dispersion compensation?
The study utilizes a combination of Single Mode Fibre (SMF), Dispersion Compensating Fibre (DCF), and Chirped Fibre Bragg Grating (CFBG) to compensate for accumulated dispersion.
What is covered in the main section of the paper?
The main section covers the theoretical basis of light dispersion, the design of the RoF system setup, and a detailed discussion of simulation results regarding OSNR, power levels, and constellation diagrams.
What characterizes the work through its keywords?
The work is characterized by terms related to optical communication technology, specifically WiMAX integration, fibre optic dispersion management, and system performance metrics like OSNR and SNR.
How does the CFBG configuration influence performance?
The configuration of the CFBG chirp length directly influences the OSNR; simulation results show that a shorter chirp length (10mm) yields better signal quality compared to longer chirp lengths.
What role does the Mach Zehnder Modulator (MZM) play in this setup?
The MZM is critical for converting the electrical WiMAX radio signal into an optical signal that can be injected into the fibre optic medium.
Why is the result after 792 km considered "highly satisfactory"?
The result is considered satisfactory because the system successfully maintained stable signal transmission over an extreme distance of 792 km with good SNR values, proving the effectiveness of the triple symmetrical compensation method.
- Quote paper
- Mazin Al Noor (Author), Jonathan Loo (Author), Richard Comley (Author), 2011, Extended Mobile WiMAX Signal Transmission over RoF viaTriple Symmetrical Dispersion System SMF, DCF and CFBG, Munich, GRIN Verlag, https://www.hausarbeiten.de/document/195645
