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CN-122017342-A - Tunable step frequency microwave carrier system based on double-pump Brillouin cavity

CN122017342ACN 122017342 ACN122017342 ACN 122017342ACN-122017342-A

Abstract

The invention discloses a tunable step frequency microwave carrier system based on a double-pump Brillouin cavity, which comprises a Brillouin laser cavity, a frequency shift injection locking loop and an optical circulation frequency shift loop, wherein the system takes two beams of wavelength tunable laser as pumping light to form a Brillouin laser cavity to generate first-order Brillouin laser, the frequency of the pumping laser is locked by utilizing the frequency shift injection locking technology, the linewidth of the pumping laser is compressed to generate dual-wavelength Brillouin laser with the linewidth compressed, the frequency of the DFB wavelength tunable laser is changed by a driver or the DFB wavelength tunable laser is changed to change the interval of the dual-wavelength Brillouin laser, in the optical circulation frequency shift loop, an acousto-optic modulator is programmed and finally a microwave source with programmable frequency sweep bandwidth is generated by a photoelectric detector.

Inventors

  • BAO HUALONG
  • WANG JIAXUAN
  • XU YIN

Assignees

  • 苏州大学

Dates

Publication Date
20260512
Application Date
20251224

Claims (10)

  1. 1. The tunable step frequency microwave carrier system based on the double-pump Brillouin cavity comprises a first optical circulator (5), a Brillouin gain optical fiber (22), a first optical fiber coupler (7) and a first polarization controller (13) which are sequentially and annularly connected to form a Brillouin laser cavity, wherein the Brillouin laser cavity receives two beams of wavelength tunable laser as pump light, one beam is emitted by a first DFB laser (1), passes through a second optical circulator (3) and a second optical fiber coupler (6), the other beam is emitted by a second DFB laser (2), passes through a third optical circulator (4) and the second optical fiber coupler (6), and the two beams of laser enter a first optical fiber amplifier (15) and the first optical circulator (5) together from the second optical fiber coupler (6) in sequence; The first optical fiber coupler (7) is connected with a third optical fiber coupler (8), wherein the third optical fiber coupler (8) is connected with a fourth optical fiber coupler (9), a first frequency shifter (17) and the second optical circulator (3) to form a first frequency shift injection locking loop, and the third optical fiber coupler (8), the second frequency shifter (18) and the third optical circulator (4) are connected to form a second frequency shift injection locking loop; The fourth optical fiber coupler (9) is sequentially connected with the fifth optical fiber coupler (10), the first acousto-optic modulator (19), the sixth optical fiber coupler (11), the seventh optical fiber coupler (12) and the photoelectric detector (25), wherein the sixth optical fiber coupler (11), the second optical fiber amplifier (16), the optical filter (24), the second acousto-optic modulator (20) and the second polarization controller (14) are sequentially and annularly connected to form an optical circulation frequency shift ring, the second acousto-optic modulator (20) is connected with the signal generator (23), and the signal generator (23) is connected with the first acousto-optic modulator (19).
  2. 2. The tunable step frequency microwave carrier system according to claim 1, wherein an eighth optical fiber coupler (26) may be additionally arranged between the second optical circulator (3) and the second optical fiber coupler (6), the eighth optical fiber coupler (26) is sequentially connected with the second frequency shifter (18), the third optical circulator (4) and the second optical fiber coupler (6), and the third optical circulator (4) is connected with the second DFB laser (2).
  3. 3. The tunable step frequency microwave carrier system according to claim 1, characterized in that the frequency of the first wavelength tunable laser emitted by the first DFB laser (1) is tuned by a driver (21) connected to the first DFB laser (1) or by a replacement DFB wavelength to change the interval of dual wavelength brillouin lasers.
  4. 4. A tunable step frequency microwave carrier system according to claim 3, characterized in that after tuning the frequency of the first wavelength tunable laser emitted by the first DFB laser (1), the second acoustic optical modulator (20) and the first acoustic optical modulator (19) inside and outside the optical cyclic frequency shift loop are programmed with repetition frequencies, pulse durations by means of a signal generator (23), and finally pass through the photodetector (25) to generate a microwave source with a programmable sweep bandwidth.
  5. 5. The tunable step frequency microwave carrier system according to claim 1, wherein the first order brillouin laser is opposite to the received laser propagation direction, the first polarization controller (13) in the brillouin laser cavity is used for adjusting the polarization of the laser to maximize the brillouin gain, the first optical fiber coupler (7) divides the first order brillouin laser into a first path of laser light and a second path of laser light, the first path of laser light circulates in the brillouin laser cavity, the second path of laser light enters the third optical fiber coupler (8) to divide a third path of laser light and a fourth path of laser light, the third path of laser light enters the second DFB laser (2) after being modulated by the second frequency shifter (18) by the third optical circulator (4) to lock the frequency of the second wavelength tunable laser light and compress the linewidth thereof, and the fourth path of laser light enters the fourth optical fiber coupler (9) to divide a fifth path of laser light and a sixth path of laser light.
  6. 6. The tunable step frequency microwave carrier system according to claim 5, wherein the fifth path of laser light enters the first DFB laser (1) through the second optical circulator (3) after being modulated by the first frequency shifter (17) so as to lock the frequency of the first wavelength tunable laser light and compress the linewidth thereof, the locked first wavelength tunable laser light and second wavelength tunable laser light serve as new light sources to generate dual-wavelength brillouin laser light with linewidth further compressed in the brillouin laser cavity, after a plurality of cycles, the linewidth of the dual-wavelength brillouin laser light reaches a limit, and the dual-wavelength brillouin laser light enters the fifth optical fiber coupler (10) as a sixth path of laser light to split a seventh path of laser light and an eighth path of laser light.
  7. 7. The tunable step frequency microwave carrier system of claim 6 wherein the seventh laser light is input to the first acousto-optic modulator (19) to generate an optical pulse, and enters the sixth fiber coupler (11) to split a ninth laser light and a tenth laser light, the ninth laser light circulating within an optical circulating frequency shift loop, and the eighth laser light and the tenth laser light enter the photodetector (25) together from the seventh fiber coupler (12) to output a step frequency optical signal with another wavelength brillouin laser light to generate a step frequency microwave signal.
  8. 8. The tunable step frequency microwave carrier system according to claims 1-2, characterized in that the second optical fiber coupler (6), the first optical fiber coupler (7), the third optical fiber coupler (8), the fourth optical fiber coupler (9), the fifth optical fiber coupler (10), the seventh optical coupler (12) and the eighth optical coupler (26) have one input and two outputs, and the sixth optical fiber coupler (11) has two inputs and two outputs.
  9. 9. The tunable step frequency microwave carrier system according to claim 1, characterized in that the second optical circulator (3) comprises three ports, which are respectively coupled to the first frequency shifter (17), the first DFB laser (1) and the second optical fiber coupler (6), the third optical circulator (4) comprises three ports, which are respectively coupled to the second frequency shifter (18), the second DFB laser (2) and the second optical fiber coupler (6), and the first optical circulator (5) comprises three ports, which are respectively coupled to the first optical fiber amplifier (15), the brillouin gain fiber (22) and the first polarization controller (13).
  10. 10. The tunable step frequency microwave carrier system according to claim 1, characterized in that the first frequency shifter (17) and the second frequency shifter (18) are electro-optical modulators.

Description

Tunable step frequency microwave carrier system based on double-pump Brillouin cavity Technical Field The invention relates to the field of microwave carrier systems, in particular to a tunable step frequency microwave carrier system based on a double-pump Brillouin cavity. Background In modern radar systems, to achieve versatility and adaptability to complex electromagnetic environments, it is desirable to generate multi-band swept-frequency microwave signals with tunable microwave center frequencies and wide swept bandwidths. Traditional electronic methods have encountered significant challenges in generating such signals due to frequency agility and narrow bandwidth limitations. The stepping frequency signal generation method relying on photon technology becomes an alternative scheme, and can expand the broadband tunable microwave center frequency and the broadband sweep bandwidth which cannot be realized by traditional electronic equipment. In addition to expanding the signal center frequency range, this approach also provides arbitrary programmability in the frequency sweep bandwidth and frequency hopping rate. In addition, the photon method is not interfered by electromagnetic interference, so that the method has advantages in the aspects of radar vital sign detection, high-precision radar ranging and the like. In recent years, although the center frequency agility and tuning range of step frequency signals have been extended to some extent, for example, a single frequency laser is used to adjust the step frequency carrier frequency by filtering in the optical loop, but this method still has a limitation. The method for carrying out the center frequency tuning by changing the center wavelength of the optical circulating filter can only limit the center frequency tuning range of the stepping frequency signal below the sweep bandwidth, so that the working capacity is limited to 100GHz. This limitation is particularly problematic for terahertz carrier generation, which is a key requirement for the next generation 6G communication system. To solve this problem, a dual laser structure employing two incoherent light sources has been proposed. However, the naturally occurring incoherence between the two lasers in such a configuration can affect the phase stability and spectral purity of the signal. In addition, the latest research utilizes soliton micro-combs to expand the capability of stepping frequency signals, and the frequency sweep of a 4GHz terahertz wave band is realized through selective comb line extraction. While this approach has advantages, it also faces two key challenges, firstly the microwave center frequency resolution is limited to the free spectral range of the microcavity, typically in the hundreds of GHz range, and secondly the need for accurate optical filters and high gain amplifiers for operation increases system complexity, and creating soliton combs involves complex laser sweep, stable and accurate red detuning control procedures, which further increases the difficulty of practical deployment. The brillouin photon platform opens new possibilities for high performance carrier sources. Researchers have proposed a novel passive locking method based on frequency-shift optical injection locking, aiming at combining the stimulated brillouin scattering, frequency-shift, optical injection locking and other technologies. In the method, the generated Brillouin laser frequency is shifted to the vicinity of the pumping frequency, the performance of the pumping laser is optimized through an injection locking technology, and the Brillouin light is respectively locked on a specific longitudinal mode, so that the mode jump phenomenon is effectively restrained, and the signal center frequency with megahertz-level fine frequency tuning and expandability in the terahertz range is generated. Although this approach is capable of tuning the frequency, there are still deficiencies in sweep speed and bandwidth. Disclosure of Invention The invention aims to provide a tunable step frequency microwave carrier system based on a double-pump Brillouin cavity so as to solve the problem that the sweep frequency speed and the bandwidth of the microwave carrier frequency cannot be flexibly adjusted, and further generate a step frequency microwave signal with programmable center frequency, sweep frequency bandwidth and frequency hopping speed. According to one aspect of the invention, a tunable step frequency microwave carrier system based on a double-pump Brillouin cavity is provided, and the tunable step frequency microwave carrier system comprises a first optical circulator, a Brillouin gain fiber, a first fiber coupler and a first polarization controller which are sequentially connected in an annular manner to form a Brillouin laser cavity, wherein the Brillouin laser cavity receives two beams of wavelength tunable laser as pump light, one beam is emitted by a first DFB laser, passes through a second optical circ