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Proceedings Paper

Compensation of third-order intermodulation distortion of electro-optic modulator by using frequency chirp modulation
Author(s): Yuta Kashiwagi; Kosuke Takase; Tadashi Kawai; Akira Enokihara; Naokatsu Yamamoto; Tetsuya Kawanishi
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Paper 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.

Paper Details

Date Published: 22 February 2018
PDF: 9 pages
Proc. SPIE 10528, Optical Components and Materials XV, 1052819 (22 February 2018); doi: 10.1117/12.2286824
Show Author Affiliations
Yuta Kashiwagi, Univ. of Hyogo (Japan)
Kosuke Takase, Univ. of Hyogo (Japan)
Tadashi Kawai, Univ. of Hyogo (Japan)
Akira Enokihara, Univ. of Hyogo (Japan)
Naokatsu Yamamoto, National Institute of Information and Communications Technology (Japan)
Tetsuya Kawanishi, National Institute of Information and Communications Technology (Japan)
Waseda Univ. (Japan)

Published in SPIE Proceedings Vol. 10528:
Optical Components and Materials XV
Shibin Jiang; Michel J. F. Digonnet, Editor(s)

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