22 February 2018 Compensation of third-order intermodulation distortion of electro-optic modulator by using frequency chirp modulation
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Proceedings Volume 10528, Optical Components and Materials XV; 1052819 (2018) https://doi.org/10.1117/12.2286824
Event: SPIE OPTO, 2018, San Francisco, California, United States
Abstract
A new electro-optic modulator for compensating the nonlinear distortion is proposed. The third-order intermodulation distortion (IMD3) in receiver output is optically suppressed by the frequency-chirp modulation in the dual-parallel Mach-Zehnder modulator (DPMZM) structure. All of optical branches of the DPMZM are symmetric. The performance was analyzed by numerical calculations.

First, we made an experiment to confirm the performance using a DPMZM with a microwave hybrid coupler for applying 10GHz two-tone signals to each electrode of the DPMZM. The chirp parameters of two Mach-Zehnder modulators (MZMs) of the DPMZM were set to opposite signs to each other, +1 and −1. It is seen from the experiment that the intensity ratio of IMD3 to signal in the receiver output was less than −58dB at modulation indices below 0.55 (0.175π) rad and that the minimum of the ratio was less than −80dB at around 0.5 (0.16π) rad. In contrast, for a conventional single-MZM the ratio was less than −27dB below 0.55rad modulation indices. These experimental results agreed well with the calculation ones.

Next, we designed and fabricated the modulator of the single-chip structure and the single-input operation for smallsizing and simple operation. The microwave rat-race circuit (RR), which operates as a 180° hybrid coupler, was designed on a Lithium Niobate (LN) substrate at 10GHz and was integrated with modulation electrodes of the DPMZM. The RR and modulation electrodes were formed with a gold thin film pattern at a time. The IMD3 suppression operation was confirmed for the fabricated modulator as well.
Conference Presentation
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yuta Kashiwagi, Yuta Kashiwagi, Kosuke Takase, Kosuke Takase, Tadashi Kawai, Tadashi Kawai, Akira Enokihara, Akira Enokihara, Naokatsu Yamamoto, Naokatsu Yamamoto, Tetsuya Kawanishi, Tetsuya Kawanishi, } "Compensation of third-order intermodulation distortion of electro-optic modulator by using frequency chirp modulation", Proc. SPIE 10528, Optical Components and Materials XV, 1052819 (22 February 2018); doi: 10.1117/12.2286824; https://doi.org/10.1117/12.2286824
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