| Summary: | 碩士 === 國立臺灣科技大學 === 光電工程研究所 === 100 === In this thesis, a low-cost automatic injection-locking control system is presented. A vertical cavity surface-emitting laser(VSCEL),which is directly modulated with DVB-T signals, is adopted as an injection source. Using this injection source, a Fébry-Perot laser diode (FP-LD) is injection-locked and is directly modulated with 1.25Gbps NRZ data for upstream transmission. Considering the variation of the injection-locked wavelength of FP-LD, we study an injection-locking control system in a more cost efficient way. In part A , we randomly pick two FP-LDs at the same time, and use a tunable laser as an injection source. Firstly, we focus on the injections on the eleven relative modes of FP-LD at 24.4oC. It is found that when the side mode suppression ratio(SMSR) is above 36dB, the mode power reach the highest value. Secondly, as the injection wavelength changes by 0.01nm, we measure the SMSR and mode optical power of the optical spectrum. From our study of the injection factures, it found that the features of the variations of SMSR and mode power are different as the wavelength increased or decreased. In part B, similar study are made of replacing the tunable laser by a VCSEL. Two kinds of experiments were performed. The first one was performed at several temperatures, staring from 22.8oC to 24.8oC with an increment of 0.1oC. We measure the SMSR and mode power. The second experiment is at a fixed temperature of 25oC for the VCSEL. We change the temperature of FP-LD by a temperature controller. In the experiment, similar conclusion is reached. The injection locking features are different as the wavelength increased or decreased. Finally, using the above mode-locking characteristics, we design a low-cost automatic injection-locking system. As the wavelength of the injection source drift, the control system responds by sensing the output light power of the FP-LD. Then, a correction signal was send to the temperature controlling circuit to vary the wavelength of the FP-LD,until the mode-locking condition are achieved.
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