| Summary: | 碩士 === 國立中山大學 === 光電工程學系研究所 === 97 === In this paper, a distributed Electroabsorption Modulator (EAM) monolithically integrated with Semiconductor Optical Amplifier (SOA) is analyzed. Using the distributed effects on the optical modulation and amplification, several advantages have been found in this work, such as high-speed modulation, microwave performance, low nose properties, and low chirp, which is quite fitted to the requirements of optical fiber communications.
EAMs have been widely used due to high-speed, high extinction ratio, the compactness, and the capability of integration. However, due to the highly loaded capacitance in the waveguide, EAMs generally suffer from high microwave reflection and thus low modulation efficiency during high-speed modulation. By the distributed structure, SOA-integrated EAMs can not only enhance the impedance match by adopting distributed high impedance transmission line (HITL), but also offer optical gain. By the optical processing scheme of re-amplification and re-modulation, it also has been found that the extra amplified spontaneous emission (ASE) noise coming from SOA can be reduced to get lower noise figure (NF). Appling the saturation on SOA, the positive frequency chirp of EAM can be compensated to give overall low chirp. By the distributed structure, chirp compensation has been realized by this characterization.
In this work, the distributed EAM-SOA scheme and the traditional single section EAM-SOA scheme are used for comparison, higher speed and lower NF are observed in distributed scheme. Due to impedance matching improvement in distributed scheme, a -3dB bandwidth of higher than 40GHz and 40Gbit/s data transmission is achieved, while a 15GHz of -3dB bandwidth is obtained in single device. Also, in 10Gbit/s data transmission, a 3dB lower of power penalty occurs in distributed scheme, while the lower NF is the mainly dominating mechanism.
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