Electro-optic Modulator for Compensating the Third Order Intermodulation Distortion by Optical Interference

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K06392
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Electron device/Electronic equipment
• Research Institution: University of Hyogo
• Principal Investigator: Enokihara Akira 兵庫県立大学, 工学研究科, 教授 (10514383)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 電気光学変調器 / 非線形 / ３次相互変調歪み / 波長チャープ / ニオブ酸リチウム

Outline of Final Research Achievements

Mach-Zehnder modulators (MZMs) can operate in high-speed modulation and are generally used for optical communication systems. However, MZMs theoretically make nonlinear responses. Distortions induced by the nonlinearity may become a serious problem. The third-order intermodulation distortion (IMD3) cannot be removed by frequency filters. The IMD3 may affect the system performance. In this research, a new optical compensation method of the nonlinear distortion in electro-optic modulators was proposed. The IMD3 are optically suppressed by using two MZMs operating with frequency chirp modulation and its performance was successfully confirmed. We designed and fabricated the modulator with the single-chip structure and the single-input operation by integrating the two MZMs with the microwave power divider circuit. The IMD3 compensation operation was experimentally confirmed. The IMD3 component could be suppressed by more than 20 dB compared to the conventional MZM.

Free Research Field

マイクロ波フォトニクス

Academic Significance and Societal Importance of the Research Achievements

本提案は、光変調器の波長チャープと歪み発生の関係を詳細に検討し、従来からの課題であった非線形歪補償に適用した。また、それを実際の素子構造に落とし込み、さらに、信号分配回路を集積化した光変調器を実際に作製した。動作原理の検証だけでなく、単体で動作する素子を実際に作製して動作実証を行うことによって、想定できなかった問題点が明らかになり、より実用性の有効性の高い研究成果となった。従来、単一チップ構成で単一入力で動作する歪み補償光変調器の報告は見当たらず、本光変調器は、実用性が高く、産業上の意義も大きいものと思われ、将来の光伝送システムで重要な素子となる可能性がある。