Compensation of third-order intermodulation distortion of electro-optic modulator by using frequency chirp modulation

Yuta Kashiwagi, Kosuke Takase, Tadashi Kawai, Akira Enokihara, Naokatsu Yamamoto, Tetsuya Kawanishi

Research output: Chapter in Book/Report/Conference proceedingConference contribution


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 (0.175 €) 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.

Original languageEnglish
Title of host publicationOptical Components and Materials XV
EditorsMichel J. F. Digonnet, Shibin Jiang
ISBN (Electronic)9781510615410
Publication statusPublished - 2018
EventOptical Components and Materials XV 2018 - San Francisco, United States
Duration: 2018 Jan 292018 Jan 31

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


OtherOptical Components and Materials XV 2018
Country/TerritoryUnited States
CitySan Francisco


  • Dual-parallel Mach-Zehnder modulator
  • Electro-optic modulator
  • Frequency chirp
  • Nonlinear distortion
  • Ratrace circuit
  • Third-order Intermodulation distortion

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


Dive into the research topics of 'Compensation of third-order intermodulation distortion of electro-optic modulator by using frequency chirp modulation'. Together they form a unique fingerprint.

Cite this