| Summary: | 碩士 === 國立臺北科技大學 === 光電工程系研究所 === 95 === Wavelength-division-multiplexing (WDM) transport system can transmit many signals in single fiber, so have benefits like capacity upgrade and network flexibility, especially for Radio-on-Fiber (ROF) transport system and Passive Optical Network (PON) applications. Hybrid WDM transport system that uses different wavelengths to transmit AM-VSB analog video, 64/256-QAM digital passband and OC-48/OC-192 digital baseband signals is very useful for an optically amplified fiber network providing CATV, internet and telecommunication services. Current WDM transport systems are composed of distributed feedback (DFB) laser diodes and erbium-doped fiber amplifiers (EDFAs) throughout the single mode fiber (SMF) link. In this thesis, we exhibit several different ways to build the WDM transport systems and improve systems’ transmission performance.
First, a cost-effective architecture is proposed for deployment in WDM transport systems, as demonstrated by the vertical cavity surface emitting lasers (VCSELs) and semiconductor optical amplifier (SOA) with external light injection technique. VCSEL is gradually used to replace DFB laser diodes for the 1.55μm wavelength window in lightwave transport systems, because it’s with a single mode with narrow linewidth and low cost. Amplify the optical signal by use SOA to replace EDFA, and use the external light injection technique to reduce the SOA-induced distortion and crosstalk.
Second, we use amplified spontaneous emission (ASE) light source and WDM demultiplexer (DEMUX) to demonstrate radio-on-DWDM transport system. The ASE light source, which is supplied by EDFA output light source. The ASE light source can be efficiently divided into many channels by using DEMUX or optical bandpass filters (OBPFs). Therefore, the ASE source can be changed into a similar DFB laser diode characteristic by using the OBPF. In addition, employs LEAF to replace the SMF as the transmission medium.
Third, we proposed a radio-on-DWDM transport system based on injection-locked Fabry-Perot (FP) LDs. Multiple longitudinal FP LD exhibits a wide spectrum spread. This wavelength spread will cause higher intensity noise and higher fiber dispersion-induced nonlinear distortions. When an FP LD is injection-locked, its multiple longitudinal modes will be changed into a similar single longitudinal mode characteristic, thus it can be utilized as a cheap light source in radio-on-DWDM architecture.
Finally, we proposed and demonstrated a potentially cost-effective hybrid WDM transport system based on mutually injection-locked FP LDs. By mutual injection between two FP LDs, we realized a broadband light source with flatness and multimode output spectrum. This proposed hybrid WDM transport system used two wavelengths (modes) for AM-VSB video signal, one for 256-QAM digital passband and one for OC-48 digital baseband signals.
Since our proposed WDM transport system does not use multiple expensive DFB LDs, it reveals a prominent one with simpler and more economic advantages than that of traditional hybrid WDM transport systems.
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