| Summary: | 碩士 === 國立交通大學 === 光電工程學系 === 101 === For the purpose to effectively reduce the cost of optical communication system, directly modulation will be better than external modulation. Most of the case for directly modulation is to modulate the laser bias current directly or to use the Electro-Absorption Modulator to modulate the laser light. In baseband communication, usable band-width is not only decided by laser gain curve, but devices’ characteristics, and the transmission distance. On the other hand, for increasing spectral efficiency, we use orthogonal frequency division multiplexing (OFDM) to modulate the signals. However, the interference between subcarriers to subcarriers, subcarriers to optical carrier, will be a main project to the directly modulated-base band optical communication system. Therefore, we use advanced digital signal processing and iterative detection techniques to compensate the interference-induced noise at receiver port. By the way, multi-band signal subcarrier allocation can avoid the energy loss due to power fading and further increase the spectral efficiency.
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