Abstract
We report an optical vector analyzer (OVA) for characterization of Fano resonance structures based on unbalanced optical double-sideband (UB-ODSB) carrier modulation, with capability to investigate the optical structures with asymmetric and ultra-narrowband spectral responses. The ratio of UB-ODSB sidebands amplitudes is not equal to one and constant throughout the measurement process. Transmitted through the optical resonant structure UB-ODSB-radiation is sent to photodetector, that is used to convert the optical signal to electrical one. Output photodetector signal contains the beat components of the UB- ODSB-radiation sidebands and optical carrier. These components splits up by bandpass filters (BPF) for post-processing of measurement results in accordance with new mathematical model that is also presented in this paper. The proposed approach allows to measure phase and magnitude responses of the optical device under test (ODUT) with high resolution; to formulate a criterion for signal falling within the limits of the investigated spectral response; to take one-step measurements.
Highlights
The theoretical investigations of the ring fiber structures with the π-phase-shifted fiber Bragg grating (FBG) have been carried out over the past five years [1]
We report an optical vector analyzer (OVA) for characterization of resonance structures based on unbalanced optical double-sideband modulation (UB-ODSB), with capability to investigate the optics structures with asymmetric and ultra-narrowband spectral responses, such as Fano resonance
UB-ODSB-radiation source consists from two modulators made by PNPPK (Perm) with half-wave voltage 3,2 V and bandwidth 11-13 GHz and optical bandpass filter (OBPF) Finisar WaveShaper 4000S
Summary
The theoretical investigations of the ring fiber structures with the π-phase-shifted fiber Bragg grating (FBG) have been carried out over the past five years [1]. The main problem of the first method is to generate ODSB-signal with optical carrier, which is asymmetrically located respect to the scanning sidebands [7,8,9] When this signal received by photodetector, the frequencies of beat components of the shifted optical carrier and scanning sidebands will be different from the modulation frequency and not equal to each other. The modulation frequency of the second modulator is constant, so bandpass problems of 90 phase shifter is eliminated It selected so in units of kHz range or smaller, that the sidebands are located so close to the MOC that the transmission coefficient of the ODUTs for all components of the UB-ODSB-radiation spectrum one can take as the same. The main advantage of proposed OVA is one-step measurements
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