Carrier suppression optical beam forming device and method based on optical comb and periodic filtering

Abstract

The invention relates to the technical field of optics, and provides a carrier suppression optical beam forming device and method based on an optical comb and periodic filtering, an optical frequency comb generates a composite optical signal containing M comb teeth, and the composite optical signal is divided into M paths of single-wavelength optical carriers after being subjected to wavelength filtering by an M-wavelength wavelength division demultiplexer; m electro-optical modulators modulate M paths of single-wavelength optical carriers into optical carriers for modulation, formed M paths of microwave photon signals are combined into one path of optical carrier signals with M wavelengths through an M-wavelength wavelength division multiplexer, intensity suppression is carried out through a periodic filter, power compensation is carried out through an optical amplifier, and dispersion delay is carried out through a delay unit; and the photoelectric detector converts the optical carrier signals of the M wavelengths after dispersion delay into microwave signals to form final beam output. The problem that a large amount of optical power is wasted on optical carriers in a traditional optical beam forming framework can be solved, the link gain is greatly improved, the noise coefficient of the system is reduced, and therefore the dynamic range of the system is widened.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and more specifically, to a carrier-suppressed optical beamforming apparatus and method based on an optical comb and periodic filtering. Background Technology

[0002] Beamforming involves weighting the output of each array element with different weighting coefficient vectors based on the amplitude and phase of signals arriving from different directions, ensuring that signals from the same target are added in phase to obtain the maximum output in a specific direction. Optical beamforming, compared to other traditional beamforming methods, has inherent advantages in terms of bandwidth, speed, integration, and parallelism when facing the beamforming capabilities required for large-scale broadband arrays. It has gained significant attention due to its wide bandwidth, small size, light weight, low loss, strong resistance to electromagnetic interference, and the absence of beam skew issues common in traditional delay devices.

[0003] The basic architecture of traditional optical beamforming (e.g., LONG MH, XU JX, ZHOU T, et al. Multi-beam optical beamformer based on the integrated arrayed waveguide grating[C] / / Applied Optics and Photonics China 2023. Beijing: CSOE,2023.) is as follows: the electro-optic conversion unit linearly transforms the downlink radio frequency signal from the receiving antenna array to different optical carriers, then performs wavelength division multiplexing and power amplification, and then feeds them into dispersive delay devices with different delay amounts for different wavelength signals to achieve amplitude and phase weighting of different array signals. Finally, the radio frequency signal is demodulated through photoelectric conversion to form a beam output. In traditional architectures, electro-optical conversion typically uses amplitude modulation operating at the quadrature bias point. This results in significant power consumption on the optical carrier, leading to low link gain and high noise figure. Link gain can be increased by increasing the optical carrier power input to the modulator or by using optical power amplification. However, increasing the optical carrier power also increases the requirements on the optoelectronic conversion device. Since typical optoelectronic conversion devices are nonlinear, excessive power can cause them to saturate, inducing nonlinear effects in the optical fiber and reducing the dynamic range of the link. Carrier suppression technology, on the other hand, reduces the carrier power injected into the optoelectronic conversion device, improving link gain and reducing the system noise figure. Furthermore, by reducing the carrier power, the problem of significant optical power wasted on the optical carrier is avoided. Therefore, with a fixed input saturation optical power, the optoelectronic conversion device can accommodate signals of more wavelengths, corresponding to more array element signals, which is beneficial for array element expansion.

[0004] In terms of carrier suppression technology, the most commonly used carrier suppression method is the bias control method based on Mach-Zehnder modulator (MZM). However, in practical systems, due to problems such as uneven frequency response and bias point drift of MZM, the bias control method based on MZM is difficult to apply to broadband signals. Summary of the Invention

[0005] This invention addresses the high bandwidth and high dynamic range reception and processing requirements of broadband signal electronic information systems. Since broadband is a crucial characteristic of optical beamforming methods, this invention provides a carrier-suppressed optical beamforming device and method based on an optical comb and periodic filtering. This solves the problem of significant optical power wasted on the optical carrier in traditional optical beamforming architectures, greatly improving link gain, reducing system noise figure, and thus enhancing the system's dynamic range.

[0006] In a first aspect, the present invention provides a carrier-suppressed optical beamforming apparatus based on an optical comb and periodic filtering, comprising: An optical frequency comb is used to generate a composite optical signal containing M comb teeth, where M corresponds to the number of antenna array elements and each comb tooth corresponds to a wavelength. The M-wavelength demultiplexer is used to perform wavelength filtering on composite optical signals and split them into M single-wavelength optical carriers. M electro-optic modulators are used to modulate M single-wavelength optical carriers onto optical carriers to form M microwave photonic signals. An M-wavelength wavelength division multiplexer is used to combine M microwave photonic signals into one M-wavelength optical carrier signal. A periodic filter is used to suppress the intensity of optical carrier signals of M wavelengths; An optical amplifier is used for power compensation of M wavelength optical carrier signals after intensity suppression; The delay unit is used to perform dispersion delay on the M wavelength optical carrier signals after power compensation; A photodetector is used to convert M wavelengths of optical carrier signal after dispersion delay into microwave signals to form the final beam output.

[0007] In a preferred embodiment, the M electro-optic modulators use a radio frequency signal with wavelength λf to perform double-sideband modulation on M single-wavelength optical carriers. The wavelength of the upper sideband signal is λx+λf, and the wavelength of the lower sideband signal is λx-λf, where x is equal to 1~M, corresponding to M wavelengths.

[0008] In a preferred embodiment, when the periodic filter suppresses the intensity of the M wavelength optical carrier signals, it also filters out the lower sideband signals.

[0009] In a preferred embodiment, in the delay unit, each wavelength undergoes independent dispersion delay, and the delay amount obtained by the optical carrier signal of each wavelength is related to the beam direction.

[0010] Secondly, the present invention provides a carrier-suppressed optical beamforming method based on optical comb and periodic filtering, comprising: An optical frequency comb generates a composite optical signal containing M comb teeth, where M corresponds to the number of antenna array elements and each comb tooth corresponds to a wavelength. The M-wavelength demultiplexer performs wavelength filtering on the composite optical signal and splits it into M single-wavelength optical carriers. M electro-optic modulators modulate M single-wavelength optical carriers onto the optical carriers to form M microwave photonic signals; An M-wavelength wavelength division multiplexer combines M microwave photonic signals into one M-wavelength optical carrier signal. A periodic filter suppresses the intensity of optical carrier signals of M wavelengths; The optical amplifier performs power compensation on the M wavelength optical carrier signals after intensity suppression; The delay unit performs dispersion delay on the M wavelength optical carrier signals after power compensation; The photodetector converts the M wavelength optical carrier signals after dispersion delay into microwave signals, forming the final beam output.

[0011] In a preferred embodiment, the M electro-optic modulators use a radio frequency signal with wavelength λf to perform double-sideband modulation on M single-wavelength optical carriers. The wavelength of the upper sideband signal is λx+λf, and the wavelength of the lower sideband signal is λx-λf, where x is equal to 1~M, corresponding to M wavelengths.

[0012] In a preferred embodiment, when the periodic filter suppresses the intensity of the M wavelength optical carrier signals, it also filters out the lower sideband signals.

[0013] In a preferred embodiment, in the delay unit, each wavelength undergoes independent dispersion delay, and the delay amount obtained by the optical carrier signal of each wavelength is related to the beam direction.

[0014] In summary, this invention utilizes an optical frequency comb and a periodic filter to achieve carrier-suppressed optical beamforming, overcoming the problem of significant optical power wastage on the optical carrier in traditional microwave photonic beamforming. Compared with beamforming methods based on conventional intensity modulation electro-optic conversion, it greatly improves system gain and reduces noise figure, making it suitable for broadband signal reception in electronic information systems. It is particularly significant and valuable in high-sensitivity receiving systems. Specific beneficial effects are as follows: 1. This invention uses an optical frequency comb to provide an optical carrier source, and the frequency difference of each wavelength is stable, which provides a basis for subsequent periodic filtering.

[0015] 2. This invention employs carrier-suppressed optical beamforming to improve the link gain and dynamic range, and reduce the link noise figure.

[0016] 3. This invention uses a filtering method to achieve carrier suppression, which is suitable for ultra-wideband optical beamforming.

[0017] 4. This invention avoids the problem of a large amount of optical power being wasted on the optical carrier. Therefore, when the saturated optical power input to the photodetector is constant, it can accommodate signals of more wavelengths, that is, correspond to more array element signals, which is beneficial for array element expansion.

[0018] 5. This invention enables the simultaneous formation of multiple beams with only one set of optical frequency comb and periodic filter. Optical beamforming is an important functional unit in broadband electronic countermeasures systems, radar systems, and communication systems. This invention improves upon the problem of a large amount of optical power being wasted on the optical carrier in traditional microwave photonic beamforming, which leads to low link gain, low dynamic range, and high noise figure. It can significantly improve the performance of the system and has great significance and application value in the fields of radar, electronic countermeasures, and communication. Attached Figure Description

[0019] Figure 1 This invention provides a schematic diagram of a carrier-suppressed optical beamforming device and method based on an optical comb and periodic filtering, which is an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the carrier suppression principle based on optical comb and periodic filtering in an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0023] Example like Figure 1As shown, an embodiment of the present invention provides a carrier-suppressed optical beamforming device based on an optical comb and periodic filtering, comprising: An optical frequency comb is used to provide a stable, equally spaced frequency light source, outputting a composite optical signal containing M comb teeth, where M corresponds to the number of antenna elements, and each comb tooth corresponds to a wavelength; that is, M comb teeth correspond to M wavelengths λ1~λ2. M ; An M-wavelength demultiplexer is used to perform wavelength filtering on a composite optical signal and divide it into M single-wavelength optical carriers. The center wavelength of the M-wavelength demultiplexer channel corresponds to the wavelength of each comb tooth in the composite optical signal. M electro-optic modulators are used to modulate M single-wavelength optical carriers onto the optical carriers to form M microwave photonic signals. In this embodiment of the invention, the M single-wavelength optical carriers are modulated using a radio frequency signal with wavelength λf. The wavelength of the upper sideband signal is λx + λf, and the wavelength of the lower sideband signal is λx - λf, where x is equal to 1 to M, corresponding to M wavelengths λ1 to λ2. M ,like Figure 2 As shown.

[0024] An M-wavelength wavelength division multiplexer is used to combine M microwave photonic signals into one M-wavelength optical carrier signal. A periodic filter is used to suppress the intensity of optical carrier signals of M wavelengths, while also filtering out the lower sideband signals. An optical amplifier is used for power compensation of M wavelength optical carrier signals after intensity suppression; The delay unit is used to perform dispersion delay on the M wavelength optical carrier signals after power compensation, that is, to perform independent dispersion delay for each wavelength. The delay amount obtained by each wavelength optical carrier signal is related to the beam direction. A photodetector is used to convert M wavelengths of optical carrier signal after dispersion delay into microwave signals to form the final beam output.

[0025] Based on the same technical concept, embodiments of the present invention also provide a carrier-suppressed optical beamforming method based on optical comb and periodic filtering, including: Step 1: The optical frequency comb generates a composite optical signal containing M comb teeth, where M corresponds to the number of antenna array elements and each comb tooth corresponds to a wavelength. Step 2: The M-wavelength demultiplexer performs wavelength filtering on the composite optical signal, splitting it into M single-wavelength optical carriers. Step 3: M electro-optic modulators modulate M single-wavelength optical carriers onto the optical carriers to form M microwave photonic signals; Step 4: The M-wavelength wavelength division multiplexer combines the M microwave photonic signals into one M-wavelength optical carrier signal. Step 5: The periodic filter suppresses the intensity of the M wavelength optical carrier signals; Step 6: The optical amplifier performs power compensation on the M wavelength optical carrier signals after intensity suppression; Step 7: The delay unit performs dispersion delay on the M wavelength optical carrier signals after power compensation; Step 8: The photodetector converts the M wavelength optical carrier signals after dispersion delay into microwave signals to form the final beam output.

[0026] To demonstrate the effectiveness of the carrier-suppressed optical beamforming device and method based on optical comb and periodic filtering of this invention, a simulation system was built using a 1×8 array as an example. Eight 10GHz radio frequency signals were modulated onto eight single-wavelength optical carriers of different wavelengths via electro-optic conversion. The wavelength and power parameters of the input electro-optic modulators 1-8 are shown in Table 1. The eight modulated microwave photonic signals were combined into one eight-wavelength optical carrier signal by an eight-wavelength wavelength division multiplexer. After entering the periodic filter, the optical carrier signal strength was consistent with the sideband signal power. After periodic filtering and power compensation by an optical amplifier, the saturated output optical power was 23dBm. The delay unit performed dispersion delay on each wavelength of the optical carrier signal, with the beam pointing preset to 0°. Finally, the photodetector converted the optical carrier signal into a microwave signal output, with the optical power input to the photodetector being 10dBm.

[0027] Table 1. Wavelength and power parameters of multi-wavelength lasers

[0028] Simulation results show that the microwave signal gain is -17.3dB and the system noise figure is 23.0dB.

[0029] Based on the above simulation, even after removing the periodic filter, the output optical power of the optical amplifier remains 23 dBm. Furthermore, all other functional unit parameters remain unchanged, and the optical power input to the photodetector remains 10 dBm. Simulation results show that the RF signal gain is -29.5 dB and the system noise figure is 28.9 dB. Under the same conditions, compared to the carrier-suppressed optical beamforming device and method based on optical comb and periodic filtering in this invention, the microwave signal gain is reduced by 12.2 dB, and the noise figure deteriorates by 5.9 dB.

[0030] As can be seen from the above, this invention utilizes an optical frequency comb and a periodic filter to achieve carrier-suppressed optical beamforming, overcoming the problem of a large amount of optical power being wasted on the optical carrier in traditional microwave photonic beamforming. This greatly improves the system gain and reduces the noise figure, making it suitable for broadband signal reception in electronic information systems. It is particularly significant and valuable in high-sensitivity receiving systems.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A carrier-suppressed optical beamforming device based on an optical comb and periodic filtering, characterized in that, include: An optical frequency comb is used to generate a composite optical signal containing M comb teeth, where M corresponds to the number of antenna array elements and each comb tooth corresponds to a wavelength. The M-wavelength demultiplexer is used to perform wavelength filtering on composite optical signals and split them into M single-wavelength optical carriers. M electro-optic modulators are used to modulate M single-wavelength optical carriers onto optical carriers to form M microwave photonic signals. An M-wavelength wavelength division multiplexer is used to combine M microwave photonic signals into one M-wavelength optical carrier signal. A periodic filter is used to suppress the intensity of optical carrier signals of M wavelengths; An optical amplifier is used for power compensation of M wavelength optical carrier signals after intensity suppression; The delay unit is used to perform dispersion delay on the M wavelength optical carrier signals after power compensation; A photodetector is used to convert M wavelengths of optical carrier signal after dispersion delay into microwave signals to form the final beam output.

2. The carrier-suppressed optical beamforming apparatus based on optical comb and periodic filtering according to claim 1, characterized in that, The M electro-optic modulators use radio frequency signals with wavelength λf to perform double-sideband modulation on M single-wavelength optical carriers. The wavelength of the upper sideband signal is λx+λf, and the wavelength of the lower sideband signal is λx-λf, where x is equal to 1~M, corresponding to M wavelengths.

3. The carrier-suppressed optical beamforming apparatus based on optical comb and periodic filtering according to claim 2, characterized in that, When the periodic filter suppresses the intensity of M wavelength optical carrier signals, it also filters out the lower sideband signals.

4. The carrier-suppressed optical beamforming apparatus based on optical comb and periodic filtering according to claim 1, characterized in that, In the delay unit, each wavelength undergoes independent dispersion delay, and the delay amount obtained by the optical carrier signal of each wavelength is related to the beam direction.

5. A carrier-suppressed optical beamforming method based on optical comb and periodic filtering, characterized in that, include: An optical frequency comb generates a composite optical signal containing M comb teeth, where M corresponds to the number of antenna array elements and each comb tooth corresponds to a wavelength. The M-wavelength demultiplexer performs wavelength filtering on the composite optical signal and splits it into M single-wavelength optical carriers. M electro-optic modulators modulate M single-wavelength optical carriers onto the optical carriers to form M microwave photonic signals; An M-wavelength wavelength division multiplexer combines M microwave photonic signals into one M-wavelength optical carrier signal. A periodic filter suppresses the intensity of optical carrier signals of M wavelengths; The optical amplifier performs power compensation on the M wavelength optical carrier signals after intensity suppression; The delay unit performs dispersion delay on the M wavelength optical carrier signals after power compensation; The photodetector converts the M wavelength optical carrier signals after dispersion delay into microwave signals, forming the final beam output.

6. The carrier-suppressed optical beamforming method based on optical comb and periodic filtering according to claim 5, characterized in that, The M electro-optic modulators use radio frequency signals with wavelength λf to perform double-sideband modulation on M single-wavelength optical carriers. The wavelength of the upper sideband signal is λx+λf, and the wavelength of the lower sideband signal is λx-λf, where x is equal to 1~M, corresponding to M wavelengths.

7. The carrier-suppressed optical beamforming method based on optical comb and periodic filtering according to claim 5, characterized in that, When the periodic filter suppresses the intensity of M wavelength optical carrier signals, it also filters out the lower sideband signals.

8. The carrier-suppressed optical beamforming method based on optical comb and periodic filtering according to claim 5, characterized in that, In the delay unit, each wavelength undergoes independent dispersion delay, and the delay amount obtained by the optical carrier signal of each wavelength is related to the beam direction.

Images