Tunable dual-passband microwave photonic filter realization device and method

Abstract

The invention belongs to the technical field of photoelectricity, and particularly relates to a tunable dual-passband microwave photonic filter realization device and method based on stimulated Brillouin scattering. A laser is adopted as a light source; signal light and pump light are generated by an optical coupler branch; a signal light branch is used for loading a to-be-filtered microwave signal through electro-optical phase modulation; a pump light branch generates tunable dual-wavelength pump light by utilizing a Brillouin scattering effect in a single-mode optical fiber and double-sideband suppressed-carrier modulation in a double-parallel Mach-Zehnder modulator; and the conversion from phase modulation of corresponding frequency components in the signal light to intensity modulationis realized by utilizing an absorption spectrum of the double-wavelength pump light in a high-nonlinearity optical fiber, so that a dual-passband microwave photonic filter with a narrow line width, ahigh out-of-band rejection ratio and high stability is realized, wherein the central frequency positions of two passbands are continuously tuned in the same direction by changing the frequency of a radio-frequency signal loaded to the double-parallel Mach-Zehnder modulator, and in addition, a passband interval can be changed by changing optical fibers with different Brillouin frequency shift quantities.

Description

technical field [0001] The invention belongs to the field of optoelectronic technology, and in particular relates to a device and method for realizing a tunable double-passband microwave photon filter. Background technique [0002] Microwave filters are usually implemented in the electrical domain by single or multiple coupled resonators, used to select microwave signals in the desired frequency band and suppress microwave signals in the remaining frequency bands, and are essential devices in radio frequency systems and links. The main disadvantage of electric domain microwave filters is poor tuning, which cannot meet the application requirements of some radio frequency systems that require wide-band tuning. The microwave photonic filter modulates the electrical signal onto the light wave, processes the signal in the optical domain, and then converts it back to the electrical domain to obtain the filtered electrical signal, which effectively overcomes the problem of poor tun...

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Problems solved by technology

In 2016, J.Q.Li and others proposed a dual-bandband microwave photonic filter based on two independent pump lasers (J.Q.Li, Y.C.Xiao, W.Dong, et al.Dual-bandbandpass tunable microwave photonic filter based on stimulated Brillouinscattering .Optoelectronics Letters, 2016,12(4):276-279), realizes the free tuning of the dual passband, but the center frequency of the passband depends on the frequency difference between the lasers, so the frequency drift of the laser seriously affects the entire The stability of the filtering system. At the same time, the scheme uses the Brillouin gain spectrum to realize the conversion from phase modulation to intensity modulation, so Brillouin spontaneous emission noise is inevitably introduced, which deteriorates the signal-to-noise ratio of the system.

In 2017, S.L.Hu et al. used a single laser combined with electro-optic modulation to generate dual pump light, and realized a tunable dual-passband microwave photonic filter (Hu S, Li L, Yi X, et al. Tunable Dual-Passband Microwave Photonic FilterBased on Stimulated Brillouin Scattering.IEEE Photonics Technology Letters,2017,29(3):330-333), although the influence of laser frequency drift on the stability of the filtering system has been solved, the two filter passbands can only be The Brillouin frequency shift (about 10 GHz) is center-symmetrically distributed, which severely limits the tuning flexibility of the filter system. In addition, this scheme also uses the Brillouin gain spectrum to realize the conversion from phase modulation to intensity modulation, and Brillouin spontaneous radiation Noise still degrades the signal-to-noise ratio of the system

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