Investigation of reflective semiconductor based, wavelength division multiplexed, passive optical network

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Dr. Gerhátné Udvary Eszter
Department of Broadband Infocommunications and Electromagnetic Theory

Nowadays the importance of the optical networks in telecommunications systems is more and more important. Since the '70s, when people first managed to use optical fibers for telecommunication purposes, the maximum achievable bit rate in optical networks is substantial increases.

The technologies, which are currently used, are standardized. However it is important for further development direction, choosing the right technology, the optimal design of network topology and structure.

New solutions for a simplified networks is using Wavelength Division Multiplexing passive optical networks (WDM PON), which are able to adapt to the increased volume of traffic. This technology is a good solution for power distribution problems, which occur in the Time Division Multiplexing PON (TDM PON). The reserve wavelengths are negligible in WDM PON, if we use colorless transmitters in the Optical Network Units (ONU).

The reflective semiconductor optical amplifiers (RSOA) fulfill most of the requirements to realize a low-cost colorless transceiver for WDM PONs: they can be operated at any wavelength, exhibit very low polarization dependency and can be directly modulated, they have optical amplification. The RSOA's biggest drawback is the limited modulation bandwidth.

During my thesis, I learned about wavelength passive optical networks, I analyzed their advantages, disadvantages. I studied the reflective semiconductor optical amplifier structure and behavior, and how to use the RSOA as an intensity modulator.

With simulations I proved that phase modulation can be converted in amplitude

modulation by using proper optical filters, and whit this conversation we can increase the modulation bandwidth of the system. I also made measurements to prove this theory.


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