Hyperfine Intrinsic Magnitude and Phase Response Measurement of Optical Filters Based on Electro-Optical Harmonics Heterodyne and Wiener-Lee Transformation

• Published in: Journal of lightwave technology Vol. 37; no. 11; pp. 2654 - 2660
• Main Authors: Zou, Xinhai, Zhang, Shangjian, Zhang, Zhiyao, Ye, Zijie, Lu, Rongguo, Chen, Dejun, Liu, Shuang, Li, Heping, Liu, Yong
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-06-2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acousto-optics; Amplitude modulation; Electro-optical harmonics heterodyne; Frequencies; Frequency measurement; Frequency modulation; Frequency ranges; Frequency response; Frequency shifters; Harmonics; Immunity; magnitude-frequency response; microwave photonics; Optical filters; Optical interferometry; Optical mixing; Optical variables measurement; Phase transitions; phase-frequency response; Rangefinding; Sidebands; Single sideband transmission; Wiener–Lee transformation
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2018.2879974

An electro-optical heterodyne scheme is proposed and demonstrated for magnitude- and phase-frequency response measurement of optical filters based on harmonics heterodyne and Wiener-Lee transformation. The method consists of an acousto-optic frequency shifter and a phase modulator located in a frequency-shifted heterodyne interferometer. The minimum phase-frequency response is simultaneously extracted from the measured magnitude-frequency response with the help of Kramers-Kronig relations and the Wiener-Lee transformation. As compared with the single-sideband-based or double-sideband-based methods, our method eliminates small-signal assumption and features an immunity to undesired spurious sidebands, enabling harmonic sideband sweeping with even-folded measuring frequency range. Prior to the conventional frequency-shifted heterodyne methods, the method enables simultaneous extraction of intrinsic magnitude and phase frequency responses for most optical filters by introducing the Wiener-Lee transformation. A phase-shifted fiber Bragg grating is measured for extracting the frequency responses in the proof-of-concept experiment with the frequency resolution up to 50 kHz and frequency range of 80 GHz by using a frequency-swept modulation of 20 GHz.