以光濾波器實現光學等化改善高速光傳輸系統

• Main Author: 張仲傑
• Format: Thesis
• Language: Chinese
• Published: 2018
• Subjects: 光學等化;直調雷射;雷射啁啾;四階震幅調變訊號;啁啾管理; Optical equalization;Directly-modulated laser;Laser chirp;Four level pulse amplitude modulation;chirp management; DML
• Online Access: http://ir.lib.ntust.edu.tw/handle/987654321/72700; http://ir.lib.ntust.edu.tw/bitstream/987654321/72700/1/index.html

國立臺灣科技大學電子工程系 學位：碩士 指導教授：李三良 本論文提出使用直調雷射以及繞射光柵濾波器之特性，來改善頻率響應不足之光纖傳輸系統，利用直調雷射所產生的頻率調變，在經過濾波器後轉變為振幅調變，藉此可達到提升明滅比並改善頻率響應。也可藉由頻譜響應的相位變化與光纖色散交互作用，來提升光纖傳輸距離。 本論文探討使用頻寬不足的直調雷射結合光濾波器來超頻傳輸高速訊號之可行性，使用波長分別為1.3及1.5微米且原為傳輸10 Gb/s 訊號的雷射，希望能達到傳輸25 Gb/s 以上訊號速率的功效，並討論使用不同調變方式的改善效果。首先藉由光學模擬軟體來模擬一高速光纖傳輸系統，再藉由加上光濾波器作為等化器來觀察此系統的效能變化，再以實驗來驗證。最後再討論將濾波器放於傳送端或接收端分別作類似於傳送端等化或接收端等化之可行性。 我們實現使用頻寬為14GHz之直調雷射搭配頻譜整形濾波器傳輸32 Gb/s的非歸零碼訊號及28 Gbaud/s的四階振幅調變訊號，明顯改善眼圖及誤碼率，並提高頻率響應約3 GHz，同時驗證了傳送端或接收端的等化皆為可行的。 We proposed a scheme to improve the transmission performance by using a diffraction grating filter for an optical transmission system with directly modulated lasers (DML) of insufficient bandwidth. The diffraction grating filter is used as a reshaping filter to convert the inherently frequency modulation (FM) associated with the amplitude modulation (AM) signals and then increase the high-frequency responses. The use of optical reshaping filter can provide three merits: extinction ratio (ER) improvement, extension of transmission distance of DML, and improvement of the frequency response of transmission system. This work investigates the feasibility of combining a directly modulated laser of insufficient frequency response with optical reshaping filter to transmit high-speed signals. The investigation is conducted for the wavelength of 1.3 μm and 1.5 μm. An commercial software is used to simulate the DML-based high-speed optical transmission system, and then observe the performance enhancement after adding an optical filter, which acts as an optical equalizer from the FM-to-AM conversion. The performance enhancement is also verified by experimental measurements. We verify that the effect of placing the optical filter at the transmit end or the receive end leads to the same performance enhancement. We realized the use of a directly modulated laser with 14-GHz bandwidth and a diffraction grating optical equalization filter to transmit 32 Gb/s NRZ and 28 Gbaud/s PAM-4 signals. The eye diagram and bit error rate are improved by using the optical equalizer. The increase in 3dB bandwidth by about 3GHz is demonstrated.