Generation and distribution of a wide-band continuously tunable millimeter-wave signal with an optical external modulation technique

• Published in: IEEE transactions on microwave theory and techniques 2005-10, Vol.53 (10), p.3090-3097
• Main Authors: Guohua Qi, Jianping Yao, Seregelyi, J., Paquet, S., Belisle, C.
• Format: Article
• Language: English
• Subjects: Applied sciences; Circuit properties; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Electrooptic modulator; Exact sciences and technology; fiber Bragg grating (FBG); Fibers; Frequency; Frequency filters; Intensity modulation; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwave filters; Microwave generation; microwave photonics; Microwaves; Millimeter wave technology; millimeter-wave generation; Modulation; Modulators; Notch filters; Optical attenuators; Optical communication; Optical filters; optical heterodye; Optical modulation; Sidebands; Signal generators; Tuning; Wideband
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2005.855123

A new technique to generate and distribute a wide-band continuously tunable millimeter-wave signal using an optical external modulator and a wavelength-fixed optical notch filter is proposed. The optical intensity modulator is biased to suppress the odd-order optical sidebands. The wavelength-fixed optical notch filter is then used to filter out the optical carrier. Two second-order optical sidebands are obtained at the output of the notch filter. A millimeter-wave signal that has four times the frequency of the microwave drive signal is generated by beating the two second-order optical sidebands at a photodetector. Since no tunable optical filter is used, the system is easy to implement. A system using an LiNbO/sub 3/ intensity modulator and a fiber Bragg grating filter is built. A stable and high spectral purity millimeter-wave signal tunable from 32 to 50 GHz is obtained by tuning the microwave drive signal from 8 to 12.5 GHz. The integrity of the generated millimeter-wave signal is maintained after transmission over a 25-km standard single-mode fiber. Theoretical analysis on the harmonic suppression with different modulation depths and filter attenuations is also discussed.