A microwave photonics transmission system

Abstract

The application belongs to the technical field of microwave photonics, and particularly relates to a microwave photon transmission system, wherein a first wavelength power signal output by a first laser is obtained through an optical emission device, the first wavelength power signal is a power signal subjected to SBS suppression; an optical amplification device is connected with the optical emission device, and is used for amplifying the power of the first wavelength power signal; an optical relay device is connected with the optical amplification device, and is used for performing optical power compensation on the first wavelength power signal and outputting a first wavelength power compensation signal; and an optical receiving device is connected with the optical relay device, and is used for demodulating the first wavelength power compensation signal into an electrical signal. The application can effectively suppress SBS, thereby suppressing phase jitter caused by temperature change, strain change and the like in microwave photon transmission, suppressing system deterioration caused by SPM and EPM, and being beneficial to improving the performance of the microwave photon transmission system.

Description

Technical Field

[0001] This invention belongs to the field of microwave photonics technology, and specifically relates to a microwave photonics transmission system. Background Technology

[0002] With the nation listing next-generation information technology as a strategic emerging industry, China's optical communication field has achieved several major breakthroughs, mastering core technologies in transmission, access, and optical fiber cables, and gradually forming an industrial development pattern with regional characteristics. However, in practical field applications, microwave photonic transmission suffers from phase jitter due to changes in transmission medium temperature and strain (external vibrations, etc.), leading to system degradation. Currently, there are few truly effective solutions in the industry, and deviations in fundamental theory hinder the progress of engineering and commercialization.

[0003] First, Brillouin scattering (SBS) is inelastic scattering caused by acoustic phonons from a medium (optical fiber, atmosphere, liquid, etc.) (the scattering frequency of light is not equal to the incident frequency). Therefore, the frequency shift and intensity characteristics of Brillouin scattering mainly depend on the elastic and thermoelastic properties of the medium (optical fiber, atmosphere, liquid, etc.). Changes in temperature and strain will cause changes in the properties of these media (optical fiber, atmosphere, liquid, etc.), thus affecting the Brillouin frequency shift and intensity. Therefore, effectively suppressing SBS can suppress phase jitter caused by temperature changes and strain changes (external vibrations, etc.) in microwave photonic transmission, thereby improving the performance of microwave photonic transmission systems.

[0004] Stimulated Brillouin scattering (SBS) is a nonlinear effect that affects the transmission performance of optical fibers. Because optical fibers are electrostrictive materials, when high-power incident light propagates through them, an electrostrictive effect occurs, causing acoustic vibrations in the fiber crystal. These vibrations change the fiber's refractive index, forming a grating. This results in most of the incident light being converted into scattered light propagating in the opposite direction, producing stimulated Brillouin scattering. The scattered light waves are called Stokes waves.

[0005] Light waves and sound waves couple with each other through electrostriction. Even at very low incident light power, the Brownian motion of the molecules in the optical fiber material will generate acoustic noise. When this acoustic noise propagates in the optical fiber, the pressure difference will cause a change in the refractive index of the optical fiber material, thereby producing spontaneous scattering of the incident light. At the same time, the propagation of the sound wave in the material will make the pressure difference and the change in refractive index periodic, resulting in a Doppler frequency shift of the scattered light frequency relative to the incident light. This scattering is called spontaneous Pryoulian scattering.

[0006] Secondly, thanks to the invention of optical amplifiers, long-distance transmission can achieve signal amplification without photoelectric or electro-optical conversion. ASE noise, or Amplifier Spontaneous Emission, mixes with the signal to become the amplifier's noise. Given a fixed carrier-to-noise ratio (CNR) and optical modulation degree without an optical amplifier, the lower the noise figure of the optical amplifier and the higher the input optical power, the smaller the system CNR loss. Therefore, in practical applications, it is essential to maximize the input optical power of the optical amplifier and use low-noise optical amplifiers.

[0007] Furthermore, Self-Phase Modulation (SPM): In long-distance microwave photonic transmission systems, self-phase modulation in the optical fiber combines with the dispersion of ITU-T G652 optical fiber, causing significant second-order signal distortion through a phase-intensity conversion process. Self-phase modulation is a nonlinear effect in optical fibers, manifesting when the light intensity is too high. Due to the nonlinear polarization of SiO2 molecules caused by a strong electric field (Kerr effect), the refractive index n of the optical fiber exhibits a component proportional to the light intensity. In long-distance microwave photonic systems, SPM and dispersion in the optical fiber are the main factors causing system performance degradation. Summary of the Invention

[0008] To address the degradation problem in existing microwave photonic transmission systems, embodiments of the present invention provide the following technical solutions:

[0009] This invention provides a microwave photonic transmission system, comprising:

[0010] An optical emitting device is used to obtain a power signal of a first wavelength output by a first laser, wherein the power signal of the first wavelength is a power signal suppressed by SBS.

[0011] An optical amplification device is connected to the optical emitting device, and the optical amplification device is used to amplify the power of the power signal of the first wavelength;

[0012] An optical repeater is connected to the optical amplifier. The optical repeater is used to perform optical power compensation on the power signal of the first wavelength and output a power compensation signal of the first wavelength.

[0013] An optical receiving device is connected to the optical relay device, and the optical receiving device is used to demodulate the power compensation signal of the first wavelength into an electrical signal.

[0014] Furthermore, the optical emitting device is also used to obtain a power signal of a first wavelength output by the first laser, wherein the power signal of the first wavelength is a power signal with SBS suppression obtained after spectral broadening.

[0015] Obtain the power signal of the second wavelength output by the second laser;

[0016] The power signal of the first wavelength and the power signal of the second wavelength are sent to a dense wavelength division multiplexing (DWDM) multiplexer, and the combined power signal is output after DWDM multiplexing.

[0017] Furthermore, the optical emitting device includes: a first laser, a second laser, and a dense wavelength division multiplexing (DWDM) multiplexer.

[0018] One input terminal of the dense wavelength division multiplexing combiner is connected to the output terminal of the first laser;

[0019] The other input of the dense wavelength division multiplexing combiner is connected to the output of the second laser.

[0020] Furthermore, it also includes: a first Mach-Zehnder modulator and a second Mach-Zehnder modulator;

[0021] The input terminal of the first Mach-Zehnder modulator is connected to the output terminal of the first laser, and is used to receive the power signal of the first wavelength and modulate the power signal of the first wavelength.

[0022] The input of the second Mach-Zehnder modulator is connected to the output of the second laser to receive the power signal of the second wavelength, with a frequency of f. RF The radio frequency signal is used as the driver of the second Mach-Zehnder modulator to modulate the power signal of the second wavelength.

[0023] Furthermore,

[0024] The output of the first Mach-Zehnder modulator is connected to the first input of the dense wavelength division multiplexing combiner.

[0025] The output of the second Mach-Zehnder modulator is connected to the second input of the dense wavelength division multiplexing combiner.

[0026] Furthermore, it also includes a dual parallel Mach-Zehnder modulator, with two input terminals located on two parallel Mach-Zehnder modulators on two branch arms of the dual parallel Mach-Zehnder modulator, one input terminal connected to the first laser and the other input terminal connected to the second laser, and having a frequency of f. RF The input of radio frequency signals.

[0027] Furthermore, the optical amplification device includes a first optical amplifier and a second optical amplifier, and the optical relay device includes a first dispersion compensation module and a second dispersion compensation module.

[0028] The first optical amplifier is used to amplify the power signal of the first wavelength to form a first amplified beam signal;

[0029] The first dispersion compensation module is connected to the first optical amplifier and is used to receive the first amplified beam signal and perform dispersion compensation processing on the first amplified beam signal to form a first compensated beam signal.

[0030] The second optical amplifier is connected to the first dispersion compensation module and is used to receive the first compensation beam signal and amplify the first compensation beam signal to form a second amplified beam signal.

[0031] The second dispersion compensation module is connected to the second optical amplifier and is used to receive the second amplified beam signal and perform compensation processing on the second amplified beam signal to form a second compensated beam signal.

[0032] Furthermore, the first optical amplifier is a preamplifier, and the second optical amplifier is a Raman amplifier.

[0033] Furthermore, it also includes a remote pumping device disposed between the first optical amplifier and the second optical amplifier, the remote pumping device being used to remotely amplify the first amplified beam signal.

[0034] Furthermore, it also includes: an optical isolation device, which includes an isolator and a TFF type WDM, the isolator being connected to the TFF type WDM, and the input end of the optical isolation device being connected to the output end of the dense wavelength division multiplexing multiplexer.

[0035] Furthermore, the first laser is a tunable linewidth laser, and the second laser is a narrow linewidth laser;

[0036] The first laser generates a laser signal with a wavelength of 1550.12 nm; the second laser generates a laser signal with a wavelength of 1550.92 nm.

[0037] The present invention has the following beneficial effects:

[0038] An embodiment of the present invention provides a microwave photonic transmission system, comprising: an optical transmitter for obtaining a power signal of a first wavelength output by a first laser, wherein the power signal of the first wavelength is a power signal suppressed by SBS; an optical amplifier connected to the optical transmitter for amplifying the power of the power signal of the first wavelength; an optical repeater connected to the optical amplifier for performing optical power compensation on the power signal of the first wavelength and outputting a power compensation signal of the first wavelength; and an optical receiver connected to the optical repeater for demodulating the power compensation signal of the first wavelength into an electrical signal. This invention suppresses phase jitter caused by temperature and strain changes in microwave photonic transmission by employing appropriate Stimulated Brillouin Scattering (SBS); reduces system carrier-to-noise ratio loss by using optical amplification devices; and mitigates system degradation caused by Self-Phase Modulation (SPM) and External-Phase Modulation (EPM) by using appropriate SBS thresholds to adapt to different transmission distances and by using optical repeaters to compensate fiber repeater segments one by one. This invention systematically solves the noise problems such as phase jitter in microwave photonic stable transmission, which is beneficial to improving the performance of microwave photonic transmission systems. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of a microwave photonic transmission system structure in one embodiment of the present invention.

[0041] Figure 2 This is a schematic diagram of the structure of a light emitting device in one embodiment of the present invention.

[0042] Figure 3 This is a schematic diagram of the structure of the light emitting device in another embodiment of the present invention.

[0043] Figure 4 The diagrams provided by this invention illustrate the relationship between strain and Brillouin frequency domain variation, as well as the relationship between temperature and Brillouin frequency domain variation.

[0044] Figure 5 This is a schematic diagram of a space optical communication structure in one embodiment of the present invention.

[0045] Figure 6 This is a schematic diagram of a lidar structure according to an embodiment of the present invention.

[0046] Figure 7This is a schematic diagram of an antenna / radar fiber optic array structure according to an embodiment of the present invention.

[0047] Figure 8 This is a schematic diagram of the structure of a global satellite navigation system according to an embodiment of the present invention.

[0048] Figure 9 This is a schematic diagram of the structure of the light emitting device in another embodiment of the present invention.

[0049] Figure 10 This is a schematic diagram of the structure of the light emitting device in another embodiment of the present invention.

[0050] Figure 11 This is a schematic diagram of the structure of an ultra-long-distance microwave photonic communication system according to an embodiment of the present invention.

[0051] Figure 12 This is a schematic diagram of a 5G / 6G fiber optic direct connection structure according to an embodiment of the present invention.

[0052] Figure 13 This is a schematic diagram of a 5G / 6G passive dense wavelength division multiplexing structure in one embodiment of the present invention.

[0053] Figure 14 This is a schematic diagram of an ultra-long-distance, large-span optical fiber quantum communication structure in one embodiment of the present invention.

[0054] Figure 15 This is a schematic diagram of the structure of an optical isolation device in one embodiment of the present invention.

[0055] Figure 16 This is a schematic diagram of the optical isolation device structure in another embodiment of the present invention. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0057] To improve the performance of microwave photonic transmission systems, the basic concept of this invention is as follows:

[0058] ① SBS suppression is performed using either direct modulation or external modulation to adapt to different transmission distances;

[0059] ② Use DCM (dispersion compensation) to compensate for each repeater segment individually.

[0060] The system degradation caused by SPM (Self-Phase Modulation) and EPM (External-Phase Modulation) is suppressed through measures ① and ②. Specific implementation methods are as follows:

[0061] Please see Figure 1 , Figure 1 This is a schematic diagram of a microwave photonic transmission system provided in one embodiment of the present invention.

[0062] Please see Figure 2 , Figure 2 This is a schematic diagram of the structure of a light emitting device in one embodiment of the present invention.

[0063] The microwave photonic transmission system includes:

[0064] The optical emitting device 1 is used to obtain the power signal of the first wavelength output by the first laser, wherein the power signal of the first wavelength is a power signal suppressed by SBS.

[0065] The power signal of the first wavelength output by the first laser is a working signal frequency of 1550.92nm, and the SBS suppression function is achieved by direct modulation.

[0066] SBS suppression frequency is (Local oscillator frequency), the signal operating frequency is , ≤ or ≥ Signal operating frequency and A mixed-frequency input laser achieves SBS suppression through phase modulation intensity. Stable phase transmission can effectively suppress phase noise caused by fiber temperature and strain during 1550.92nm wavelength microwave photon transmission.

[0067] The optical emitting device 1 drives the operating signal wavelength of the first laser by mixing the SBS signal and the signal source RF.

[0068] Optical amplification device 2 is connected to the optical emitting device 1, and the optical amplification device 2 is used to amplify the power of the power signal of the first wavelength;

[0069] In some embodiments, the optical amplification device 2 can be an EDFA / YEDFA power optical amplifier with an input range of -10 to +10 dBm and a preamplifier input range of -20 to +3 dBm. It employs APC (Automatic Power Control) and ACC (Automatic Current Control) to lock the output optical power deviation of the EDFA / YEDFA to ±0.1 dB.

[0070] Alternatively, an RFA-based centralized Raman amplifier can replace the EDFA / YEDFA power optical amplifier, reducing the carrier-to-noise ratio loss to less than 0.5. This is suitable for microwave photonic transmission, terahertz optical communication, lidar, and space communication.

[0071] Optical repeater 3 is connected to optical amplifier 2. Optical repeater 3 is used to perform optical power compensation on the power signal of the first wavelength and output the power compensation signal of the first wavelength.

[0072] In some embodiments, the optical repeater 3 is a dispersion compensation module (DCM) (also known as a dispersion compensation unit, DCU) used to compensate for dispersion, for example, to compensate for dispersion in a long transmission fiber.

[0073] Optical receiver 4 is connected to optical repeater 3. Optical receiver 4 is used to demodulate the power compensation signal of the first wavelength into an electrical signal.

[0074] The optical receiving device 4 of the present invention has a receiving power range of -20 to +3dBm, adopts optical AGC control, and locks the output RF level deviation to ±0.2dB.

[0075] This invention provides a microwave photonic transmission system comprising: an optical transmitter for obtaining a power signal of a first wavelength output from a first laser, wherein the first wavelength power signal is a power signal suppressed by SBS (Strain-Based Power Surge); an optical amplifier connected to the optical transmitter for amplifying the power of the first wavelength power signal; an optical repeater connected to the optical amplifier for performing optical power compensation on the first wavelength power signal and outputting a power-compensated signal of the first wavelength; and an optical receiver connected to the optical repeater for demodulating the power-compensated signal of the first wavelength into an electrical signal. This invention effectively suppresses SBS, thereby suppressing phase jitter caused by temperature changes and strain changes in microwave photonic transmission, suppressing system degradation caused by SPM (Strain-Based Power Surge) and EPM (Electronic Power-Based Power Surge), and improving the performance of the microwave photonic transmission system.

[0076] As a further improvement to the above embodiments, please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of a light emitting device in one embodiment of the present invention, as shown below. Figure 3 As shown.

[0077] The light emitting device 1 is also used to obtain the power signal of the first wavelength output by the first laser, wherein the power signal of the first wavelength is the power signal with SBS suppression obtained after spectral broadening.

[0078] Obtain the power signal of the second wavelength output by the second laser;

[0079] The power signals of the first wavelength and the power signals of the second wavelength are sent into a dense wavelength division multiplexing (DWDM) multiplexer, and the combined power signal is output after DWDM multiplexing.

[0080] It should be noted that Brillouin scattering (SBS) has a significant impact on fiber optic transmission systems.

[0081] Stimulated Brillouin scattering (SBS) is an inelastic scattering caused by acoustic phonons in a medium (optical fiber, atmosphere, liquid, etc.) (the scattering frequency of light is not equal to the incident frequency). Therefore, the characteristic parameters of Brillouin scattering, such as frequency shift and intensity, mainly depend on the elastic and thermoelastic properties of the medium (optical fiber, atmosphere, liquid, etc.). Changes in temperature and strain will cause changes in the properties of these media (optical fiber, atmosphere, liquid, etc.), thereby affecting the Brillouin frequency shift and intensity.

[0082] 1. Relationship between Brillouin frequency shift and temperature and strain

[0083] Changes in fiber temperature and strain can alter fiber properties, thus affecting Brillouin frequency shift and intensity. Brillouin frequency shift variation ( ) along the fiber and temperature change ( ) and strain change ( It exhibits a linear mixed change. =493MHz / % =1MHz / ℃. The Brillouin frequency shift temperature and strain formulas are as follows:

[0084] (Formula 1)

[0085] Temperature changes induce thermal expansion in optical fibers, affecting fiber density; their thermo-optical effects cause changes in refractive index; and temperature variations also alter fiber properties such as Young's modulus and Poisson's ratio. When strain changes, the elasto-optical effect causes changes in refractive index; the interatomic interaction potential within the fiber also influences Young's modulus and Poisson's ratio. Figure 4 The diagrams provided by this invention illustrate the relationship between strain and Brillouin frequency domain variation, as well as the relationship between temperature and Brillouin frequency domain variation.

[0086] 2. Brillouin frequency shift and bandwidth

[0087] The frequency of the reflected light is slightly less than the frequency of the incident light, the frequency difference is... The frequency difference is equal to the phonon's frequency; this frequency difference is called the Brillouin shift. The Brillouin shift can be determined only when backscattering of the Brillouin is present, and can be expressed through the refractive index *n* and the phonon velocity. and wavelength The calculations show that the Brillouin frequency is related to the composition of the medium and, to some extent, depends on the temperature and pressure of the medium. Another important application of stimulated Brillouin scattering is optical phase conjugation.

[0088] (Formula 2)

[0089] in, The Brillouin frequency shift for a wavelength of 1550nm is 11.2GHz; n is the effective group refractive index of the fiber, which is 1.4671. The phonon velocity in the optical fiber is 5.95 km / s; The wavelength is 1550nm.

[0090] 3. SBS threshold

[0091] (Formula 3)

[0092] in, This is the SBS threshold; The effective core area of ​​the optical fiber is calculated based on the core diameter. The peak Brillouin gain is 3 to 5 × 10⁻⁶. -11 m / W; Effective interaction length: ,in: - Fiber attenuation coefficient, - Fiber optic length; The SBS gain bandwidth for optical fiber is 20–100 MHz. The spectral linewidth of the incident light is given.

[0093] Therefore, SBS suppression includes the following two methods ① > ① The spectral linewidth of the incident light is greater than the SBS gain bandwidth of the optical fiber; ② An appropriate SBS threshold is used to adapt to different media and transmission distances. This can effectively suppress phase jitter caused by temperature changes, strain changes, etc. in microwave photonic transmission.

[0094] Optical phase conjugation (SBS) is an important application of optical phase conjugation (SBS). In atmospheric or space communications (LiDAR, satellite communications), it can suppress phase noise caused by turbulence, temperature, and environmental strain. SBS suppression enables optical phase conjugation to suppress phase noise caused by atmospheric turbulence, temperature, and environmental strain in LiDAR or satellite communications.

[0095] In one embodiment, see Figure 5 , Figure 5 This is a schematic diagram of a space optical communication structure in one embodiment of the present invention, as shown below. Figure 5As shown: In space optical communication applications, the first laser operates at a wavelength of 1550.12nm. As a phase-stable source laser, its spectral linewidth is tunable from 10kHz to 10GHz, that is, its SBS is continuously tunable from 3.4 to 23.4 dBm. A laser with a fixed spectral linewidth can be selected, for example, 0.1nm to achieve an SBS suppression of 24.4dBm.

[0096] The second laser operates at the primary wavelength of 1550.92nm for space optical communication, employing a narrow-linewidth laser for coherent detection. At the transmitting end, dense wavelength division multiplexing (DWDM) is used to combine the 1550.12nm and 1550.92nm wavelengths. At the receiving end, the 1550.12nm and 1550.92nm wavelength signals are then subjected to DWDM demultiplexing. The 1550.92nm wavelength signal is used for photoelectric conversion via photodetector, while the 1550.12nm wavelength signal is used for termination. This achieves optical phase conjugation, suppressing phase noise caused by atmospheric turbulence, temperature, and environmental strain in space optical communication.

[0097] Optical phase conjugation is an important application of SBS, which can suppress phase noise caused by turbulence disturbances, temperature and environmental strain in atmospheric or space optical communications (satellite / ground, satellite / satellite, satellite / aircraft, aircraft / aircraft, air / ground and ground station to ground).

[0098] With the continuous development of laser technology, microwave photonics technology, optical communication technology, and other related fields, frequency-modulated continuous wave (FM-CW) lidar has received increasing attention. Compared to Time-of-Flight (TOF) lidar, FM-CW lidar has the following technical advantages: ① higher sensitivity and dynamic range (>60dB); ② resistance to interference from sunlight and other lasers; ③ ability to perform Doppler velocimetry; ④ facilitating on-chip integration. Benefiting from these advantages, FM-CW lidar has already been applied in high-precision 3D imaging, remote sensing mapping, and autonomous driving. The rapidly developing integrated microwave photonics technology is also injecting new vitality into FM-CW lidar, and on-chip integration will become an important development trend for FM-CW lidar.

[0099] Optical phase conjugation (SBS) plays an important role in lidar applications, suppressing phase noise caused by turbulence, temperature, and environmental strain.

[0100] The principle of a phase-stable transmission optical transmitter (Tx) with SBS functionality is as follows: by inputting an SBS source into a laser (the SBS suppression frequency is the local oscillator frequency), the signal operating frequency is... Dual SBS frequency suppression ≤ , ≥ Depending on the specific circumstances, do not interfere. In this case, It can be flexibly combined. The SBS threshold is tunable by tuning the phase modulation intensity. The SBS threshold can be selected based on the transmission medium (optical fiber, atmosphere, liquid, etc.).

[0101] Therefore, the microwave photonic transmission system provided by this invention serves as a clock frequency transmission device and can effectively suppress phase noise caused by fiber temperature and strain.

[0102] The laser operates at wavelengths that are not specifically 1550.92nm or 1550.12nm, as long as they conform to ITU-T wavelengths or other specific wavelengths. It can operate in optical radio frequency links, microwave photonic links (MPL), optical carrier communication (ROF), optical millimeter-wave communication, THzOF (terahertz optical communication), lidar, and other frequency bands and applications.

[0103] Please see Figure 6 , Figure 6 This is a schematic diagram of a lidar structure according to an embodiment of the present invention, as shown below. Figure 6 As shown, in the application of frequency-modulated continuous wave lidar, the first laser operates at a wavelength of 1550.12 nm, serving as a phase-stable source laser. Its spectral linewidth is tunable from 10 kHz to 10 GHz, meaning its SBS (Suppression Baseline) is continuously tunable from 3.4 to 23.4 dBm. A laser with a fixed spectral linewidth can be selected, for example, 0.1 nm to achieve an SBS suppression of 24.4 dBm. The second laser, operating at the main lidar wavelength of 1550.92 nm, is a narrow-linewidth laser used for coherent detection. At the transmitting end, dense wavelength division multiplexing (DWDM) is used to combine the 1550.12 nm and 1550.92 nm wavelengths; at the receiving end, DWDM is used to demultiplex the 1550.12 nm and 1550.92 nm wavelengths. The 1550.92 nm wavelength is used for photoelectric conversion in optical detection, while the 1550.12 nm wavelength is used for termination. This achieves optical phase conjugation, suppressing phase noise caused by atmospheric turbulence, temperature, and environmental strain in the lidar.

[0104] Multistatic radar must ensure time, frequency, and phase synchronization. In astronomical observation and aerospace telemetry and control, large-aperture antennas are required to obtain high resolution. However, the maximum aperture of a single antenna is limited by technical conditions and cannot be too large. To reduce costs and improve system flexibility, antenna arrays are used: multiple antennas located at different positions receive signals in phase coherently, which can be combined into an antenna with a large equivalent aperture. The key is to ensure the consistency of the phase relationship between the signals received by each antenna element in the antenna array.

[0105] Please see Figure 7 , Figure 7 This is a schematic diagram of an antenna / radar fiber optic array structure according to an embodiment of the present invention, as shown below. Figure 7As shown, in antenna / radar fiber optic array applications, the 1550.92nm wavelength is used for transmission within the antenna / radar fiber optic array. Optical carrier communication (ROF), millimeter-wave optical communication, or THz over fiber (THz optical communication) are employed to transmit radar, radio telescope, or aerospace telemetry and control frequency signals. A stable phase transmission optical transmitter (Tx) is also used. It has a wavelength of 1550.12nm and features SBS suppression. The 1550.12nm and 1550.92nm wavelengths (both uplink and downlink) are used for wavelength division multiplexing. The 1550.12nm wavelength serves as a high-precision clock frequency transmission device for antenna / radar fiber optic arrays, while effectively suppressing phase noise caused by fiber temperature and strain in 1550.92nm wavelength microwave photonic transmission.

[0106] In some embodiments, the 1550.92nm wavelength operating signal frequency and the high-precision clock frequency are mixed and SBS suppression is adopted. The stable phase transmission can effectively suppress the phase noise generated by fiber temperature and strain in the 1550.92nm wavelength microwave photonic transmission, so there is no need for 1550.12nm wavelength equipment and dense wavelength division multiplexing.

[0107] Please see Figure 8 , Figure 8 This is a schematic diagram of a global navigation satellite system structure according to an embodiment of the present invention. The global navigation satellite system achieves phase-stable transmission via optical fiber to the receiver. It eliminates hardware delay jitter from each antenna to the receiver in real time, ensuring that the signals received by the antennas are transmitted to the receiver with very small phase jitter, thereby significantly improving elevation accuracy to be comparable to horizontal accuracy. This enables high-precision attitude measurement or infrastructure structural health monitoring.

[0108] This invention provides a microwave photonic transmission system that obtains a power signal of a first wavelength from a first laser via an optical emitting device. This first wavelength power signal is a power signal with SBS suppression achieved through spectral broadening. A second wavelength power signal from a second laser is then obtained. The first and second wavelength power signals are fed into a dense wavelength division multiplexing (DWDM) multiplexer for DWDM multiplexing, outputting a combined power signal. By controlling the spectral linewidth of the incident light to be greater than the SBS gain bandwidth of the optical fiber, SBS suppression is achieved based on spectral broadening. This effectively suppresses SBS, thereby suppressing phase jitter caused by temperature and strain changes in microwave photonic transmission. This improves the performance of the microwave photonic transmission system, enables optical phase conjugation, and suppresses phase noise generated by atmospheric turbulence, temperature, and environmental strain in lidar or satellite communications.

[0109] As a further improvement to the above embodiments, the optical emitting device 1 includes: a first laser, a second laser, and a dense wavelength division multiplexing (DWDM) multiplexer.

[0110] One input terminal of the dense wavelength division multiplexing combiner is connected to the output terminal of the first laser;

[0111] The other input of the dense wavelength division multiplexing combiner is connected to the output of the second laser.

[0112] The above connection method is a direct modulation method: it employs dense wavelength division multiplexing of a second laser source and a first laser source with stable phase. The spectral linewidth of the first laser is determined based on the transmission medium (optical fiber, atmosphere, liquid, etc.), thereby optically achieving SBS suppression. Alternatively, a tunable linewidth laser can also be selected to achieve SBS suppression.

[0113] In addition, SPM and EPM also have an impact on microwave photonic transmission systems.

[0114] Self-phase modulation (SPM): In long-distance microwave photonics transmission systems, self-phase modulation in optical fibers, combined with the dispersion of ITU-T G652 fibers, causes significant second-order signal distortion through a phase-intensity conversion process. Self-phase modulation is a nonlinear effect in optical fibers, manifesting when the light intensity is too high. Due to the nonlinear polarization of SiO2 molecules caused by a strong electric field (Kerr effect), the refractive index n of the fiber exhibits a component proportional to the light intensity. In long-distance microwave photonics systems, SPM and dispersion in the fiber are the main factors causing system performance degradation. To achieve long-distance transmission, it is essential to reduce the dispersion constant of the optical fiber. Dispersion compensation is the most effective method.

[0115] External-Phase Modulations (EPM): For steady-state optical transmitters, a high SBS threshold can be obtained by utilizing a large phase modulation index in the integrated MZM and phase modulator. The EPM effect is a conversion between external-phase modulation and intensity modulation, and it interacts with the nonlinear dispersion of the fiber. EPM also introduces second-order distortion. The increase in the SBS threshold caused by phase modulation is given by the following formula:

[0116] (Formula 4)

[0117] Therefore, in microwave photonic transmission systems, ① an appropriate SBS threshold is adopted to adapt to different transmission distances; ② DCM (dispersion compensation) is used to compensate for each repeater segment. These measures suppress system degradation caused by SPM (self-phase modulation) and EPM (external phase modulation).

[0118] Therefore, as a further improvement to the above embodiments, please refer to Figure 9 , Figure 9This is a schematic diagram of the structure of the light emitting device in another embodiment of the present invention; as shown below. Figure 9 As shown, the light emitting device 1 also includes: a first Mach-Zehnder modulator and a second Mach-Zehnder modulator;

[0119] The input of the first Mach-Zehnder modulator is connected to the output of the first laser, and is used to receive the power signal of the first wavelength and modulate the power signal of the first wavelength.

[0120] The input of the second Mach-Zehnder modulator is connected to the output of the second laser to receive the power signal of the second wavelength, with a frequency of f. RF The radio frequency signal is used as the driver of the second Mach-Zehnder modulator to achieve modulation of the power signal of the second wavelength.

[0121] The SBS suppression signal is obtained by broadening the output spectrum of the first laser and input to the first Mach-Zehnder modulator. The working signal wavelength signal of the second laser is input to the second Mach-Zehnder modulator and subjected to dense wavelength division multiplexing to combine the wavelengths, thereby ensuring that the working signal wavelength of the second laser can effectively suppress phase noise.

[0122] A Mach-Zehnder modulator splits the input light into two equal signals, each entering a separate optical branch of the modulator. These two branches are made of electro-optical materials whose refractive index varies with the magnitude of the applied electrical signal. Because the change in refractive index of the optical branches causes a change in the signal phase, when the outputs of the two branch signals are combined again, the synthesized optical signal is an interference signal with varying intensity. This effectively converts the change in the electrical signal into a change in the optical signal, achieving modulation of light intensity.

[0123] Specifically, the output of the first Mach-Zehnder modulator is connected to the first input of the dense wavelength division multiplexing combiner.

[0124] The output of the second Mach-Zehnder modulator is connected to the second input of the dense wavelength division multiplexing combiner.

[0125] The spectral broadening of the first laser is suppressed by SBS and input to the first Mach-Zehnder modulator. The working signal wavelength output by the second laser is input to the second Mach-Zehnder modulator and then subjected to dense wavelength division multiplexing (DWDM) to combine the wavelengths, thereby ensuring that the working signal wavelength output by the second laser can effectively suppress phase noise.

[0126] External modulation method: Dense wavelength division multiplexing is used with a second laser as the signal source and a first laser as the phase-stable source. The spectral linewidth of the first laser is determined based on the transmission medium (optical fiber, atmosphere, liquid, etc.) to achieve optical SBS suppression. For example, using a 0.1 nm spectral linewidth laser achieves 24.4 dBm SBS suppression. The first laser can be a tunable linewidth laser for SBS suppression, for example, continuously tuned from 10 kHz to 10 GHz, i.e., SBS suppression of 3.4–23.4 dBm. Laser 2 is the operating signal wavelength and is a narrow linewidth laser.

[0127] In another embodiment, a dual parallel Mach-Zehnder modulator is also included.

[0128] The two input terminals are located on two parallel Mach-Zehnder modulators on the two branch arms of the dual parallel Mach-Zehnder modulator, respectively. One input terminal is connected to the first laser, and the other input terminal is connected to the second laser, with a frequency of f. RF The input of radio frequency signals.

[0129] Figure 10 This is a schematic diagram of the structure of the light emitting device in another embodiment of the present invention; as shown below. Figure 10 As shown, Figure 9 The first Mach-Zehnder modulator and the dense wavelength division multiplexing combiner and the second Mach-Zehnder modulator in the circuit are replaced with dual parallel Mach-Zehnder modulators. Figure 10 Working principle and Figure 9 The same applies, so I won't go into details here.

[0130] Thanks to the invention of optical amplifiers, long-distance transmission can achieve signal amplification without photoelectric or electro-optical conversion. ASE noise, or Amplifier Spontaneous Emission, mixes with the signal to become the amplifier's noise. Given a fixed carrier-to-noise ratio (CNR) and optical modulation degree without an optical amplifier, a lower CNR and higher input optical power result in less CNR loss. Therefore, in practical applications, it is essential to maximize the input optical power of the optical amplifier and use low-noise optical amplifiers.

[0131] It should be noted that the degradation of CNR by the optical amplifier is due to ASE noise, which stands for Amplifier Spontaneous Emission. ASE noise mixes with the signal and becomes the amplifier's noise. Given a fixed carrier-to-noise ratio (CNR) and optical modulation degree without an optical amplifier, the lower the noise figure of the optical amplifier and the higher the input optical power, the smaller the CNR loss. Therefore, it is important to maximize the input optical power of the optical amplifier and use a low-noise optical amplifier. The CNR loss caused by the optical amplifier is:

[0132] (Formula 5)

[0133] in, The carrier-to-noise ratio of the optical amplifier is denoted by Be; Be is the RF operating bandwidth. m is the noise figure of the optical amplifier; m is the optical modulation degree. λ=1550nm ; ; This represents the power of the input optical amplifier.

[0134] Therefore, measures to reduce the carrier-to-noise ratio (CNR) loss caused by optical amplifiers include: ① increasing the power of the input optical amplifier; ② using low-noise optical amplifiers, as the noise figure of existing EDFA / YEDFA is 4–8 dB, and the CNR loss is 2 dB when the noise figure is 4 dB; ③ using FRA Raman amplifiers with extremely low noise figures for centralized use to replace existing EDFA / YEDFA, which can reduce the CNR loss to less than 0.5; ④ in long-distance fiber optic transmission, due to the large number of cascaded EDFAs and FRAs, in order to reduce stray wavelengths other than signal light and reduce ASE noise of EDFAs and FRAs, the use of optical filters should be considered, which can effectively reduce the CNR loss of multiple stages of the system by about 1.2–1.5 dB.

[0135] In one embodiment, the optical amplification device 2 includes a first optical amplifier and a second optical amplifier, and the optical relay device 3 includes a first dispersion compensation module and a second dispersion compensation module.

[0136] The first optical amplifier is used to amplify the power signal of the first wavelength to form the first amplified beam signal;

[0137] The first dispersion compensation module is connected to the first optical amplifier and is used to receive the first amplified beam signal and perform dispersion compensation processing on the first amplified beam signal to form a first compensated beam signal.

[0138] The second optical amplifier is connected to the first dispersion compensation module and is used to receive the first compensation beam signal and amplify the first compensation beam signal to form the second amplified beam signal.

[0139] The second dispersion compensation module is connected to the second optical amplifier and is used to receive the second amplified beam signal and perform compensation processing on the second amplified beam signal to form a second compensated beam signal.

[0140] Specifically, the first amplification device is a preamplifier, and the second amplification device is a Raman amplifier.

[0141] The input range of the EDFA / YEDFA power optical amplifier is -10 to +10dBm, and the input range of the preamplifier is -20 to +3dBm. It adopts APC (Automatic Power Control) and ACC (Automatic Current Control) to lock the output optical power deviation of the EDFA / YEDFA to ±0.1dB.

[0142] In some embodiments, an RFA-centric Raman amplifier replaces the existing EDFA / YEDFA, reducing the carrier-to-noise ratio loss to less than 0.5. This is suitable for microwave photonic transmission, terahertz optical communication, lidar, and space communication.

[0143] The use of distributed Raman amplifiers can effectively increase the gain of space optical communication links by more than 10dB and effectively reduce carrier-to-noise ratio loss.

[0144] Those skilled in the art can choose flexibly according to the actual situation.

[0145] In some embodiments, a remote pumping device is also included, disposed between the first optical amplifier and the second optical amplifier, the remote pumping device being used to remotely amplify the first amplified beam signal.

[0146] It should be noted that the remote pumping device is existing technology, and this invention does not make any structural improvements to the remote pumping device. This invention applies remote pumping technology to a microwave photonic transmission system to achieve ultra-long-distance, large-span, high-precision fiber optic time and frequency transmission. Those skilled in the art can select a suitable remote pumping device according to actual needs.

[0147] Please see Figure 11 , Figure 11 This is a schematic diagram of an ultra-long-distance microwave photonic communication system according to an embodiment of the present invention, as shown below. Figure 11 As shown, the clock frequency from the clock source is input to the stable phase transmission optical transmitter (Tx). Through EDFA amplification, EDFA and DCM combination, remote pumping technology (span up to 300km), FRA (fiber Raman amplifier, distributed application, span over 150km), and DCM combination; a centralized FRA can be used to replace the EDFA, reducing carrier-to-noise ratio loss and achieving a transmission distance of 10,000km; the DWDM of the bidirectional transmission backbone can be replaced by a circulator. The average frequency offset is -2.6 × 10⁻⁶. -20 The long-term frequency stability is 1×10-19 Phase jitter caused by temperature changes, strain changes (external vibrations, etc.) is effectively reduced to 5 × 10⁻⁶. -3 With a precision within ps / (K·Km) and combined with the accuracy of the time interval counter, the time accuracy for 10,000 km can be controlled within 100 ps. It can be applied to users in industries such as communications networks, power, internet, aerospace and military, and transportation.

[0148] Please see Figure 12 , Figure 12 This is a schematic diagram of a 5G / 6G fiber optic direct connection structure according to an embodiment of the present invention.

[0149] It should be noted that the main 5G frequency band is Sub6GHz, primarily 3.5GHz; the extended 5G frequency band is millimeter wave, primarily 28 / 39 / 60 / 73GHz. The 6GHz terahertz band ranges from 0.1 to 10THz, with approximately 10THz of candidate spectrum. Using microwave photonics (MPL), optical carrier communication (ROF), optical millimeter wave communication, or THz over Fiber (terahertz optical communication) transmission, only a pair of optical transceiver modules is needed to cover most of the frequency bands.

[0150] For example, a 40GHz microwave photonic module using predistortion circuits or linear lasers can cover not only the full frequency bands of 2G, 3G, 4G and Sub6G, but also some of the 5G extended frequency band millimeter waves, providing almost full coverage of the operator's frequency bands and greatly saving operating costs.

[0151] In this invention, a wavelength of 1550.92nm is used for 2G, 3G, 4G, 5G, and 6G fronthaul, employing microwave photonic transmission. A stable phase transmission optical transmitter (Tx) is also used. It uses a wavelength of 1550.12nm and has SBS suppression capabilities. The 1550.12nm and 1550.92nm wavelengths (both uplink and downlink) are used for dense wavelength division multiplexing. The 1550.12nm wavelength serves as a high-precision clock frequency transmission device for DU / AAU, while effectively suppressing phase noise caused by fiber temperature and strain in microwave photonic transmission at the 1550.92nm wavelength.

[0152] Please see Figure 13 , Figure 13 This is a schematic diagram of a 5G / 6G passive dense wavelength division multiplexing structure in one embodiment of the present invention, as shown below. Figure 13 As shown, each AAU uses a different wavelength for 2G, 3G, 4G, 5G, and 6G fronthaul, employing microwave photonics transmission. A stable phase transmission optical transmitter (Tx) is also included. It has a wavelength of 1550.12nm and features SBS suppression. The 1550.12nm wavelength is used as one wavelength in passive DWDM and is used for wavelength division multiplexing with each AAU wavelength (uplink and downlink). The 1550.12nm wavelength serves as a high-precision clock frequency transmission device for DU / AAU, and can effectively suppress phase noise caused by fiber temperature and strain during microwave photonic transmission at each AAU wavelength.

[0153] It can be applied to ITS and rail transit systems: ① Intelligent Transportation Systems (ITS) provide information services such as high-precision time synchronization, real-time traffic conditions, and optimal routes. Currently, ITS mainly has two types: Road-to-Vehicle Communication (RVC) and Inter-Vehicle Communication (IVC). RVC access systems can provide multi-service broadband access and are characterized by simple installation and low cost. ② Microwave photonics transmission technology is not only applied to ITS but also to rail transit systems and high-speed railways. Utilizing antennas distributed along the railway line, a seamless wireless network covering the railway can be formed. In specific implementation, it provides high-precision time synchronization. Each base station uses microwave photonics technology to achieve radio frequency remote extension, improving the effective utilization of the coverage area and simplifying handover issues.

[0154] Mixing other wavelength operating signal frequencies with high-precision clock frequencies and employing SBS suppression, stable phase transmission can effectively suppress phase noise generated by fiber temperature and strain in other wavelength microwave photonic transmission, thus eliminating the need for 1550.12nm wavelength equipment and DWDM.

[0155] The impact of RIN and IIN on microwave photonics transmission systems

[0156] Relative intensity noise (RIN) is directly related to the fiber optic link. RIN originates from the quantum fluctuations of carrier and photon density within the resonant cavity and is inherent to the laser. Its inherent intensity noise is not high, generally less than -160dB / Hz, but it can exhibit significant intensity noise in the system. Degradation can even increase it by 10-20dB. This is due to noise caused by light reflected from fiber discontinuities (such as active connectors or fiber fusion splices) into the laser cavity, or noise caused by light undergoing multiple reflections between discontinuities.

[0157] Microwave photonic transmission systems also suffer from interference intensity noise (IIN). The so-called interference intensity noise caused by multiple reflections along the fiber system increases the relative noise. Interference intensity noise is caused by the different arrival times of two coherent beams at the photodetector, which converts the frequency-modulated phase noise of the laser into amplitude-modulated interference intensity noise.

[0158] Because optical links contain a large number of passive optical components, and optical reflection can significantly increase RIN and IIN, the following measures can be taken to reduce system noise: selecting appropriate laser bias current; adding optical isolators; using high-quality active connectors with high reflection loss, such as SC / APC with reflection loss <-60dB; using optical couplers (splitters) with high isolation suitable for systems with different operating wavelengths; appropriately reducing the number of active connectors; and employing high-quality construction techniques at optical cable splicing points.

[0159] like Figure 14 As shown, Figure 14 This is a schematic diagram of an ultra-long-distance, large-span fiber optic quantum communication structure in one embodiment of the present invention. The quantum communication optical signal is many orders of magnitude lower than the optical signal of a stable phase optical transmission system (ultra-long-distance, high-precision, large-span fiber optic time-frequency transmission). When performing WDM (DWDM or CWDM) transmission, the adjacent isolation of typical WDM (DWDM or CWDM) devices is <30dB. The optical signal of the stable phase optical transmission system is easily crosstalked into the quantum communication optical signal, causing an increase in the RIN noise of the quantum communication laser and the intensity noise of the photodetector. Therefore, it is necessary to improve the adjacent isolation of WDM devices.

[0160] It should be noted that Wavelength Division Multiplexing (WDM) is a technique that combines two or more optical carrier signals of different wavelengths (carrying various information) at the transmitting end using a multiplexer (also called a multiplexer) and couples them into the same optical fiber for transmission. At the receiving end, the various wavelength optical carriers are separated by a demultiplexer (also called a demultiplexer), and then further processed by an optical receiver to recover the original signal. This technique of simultaneously transmitting two or more different wavelength optical signals in the same optical fiber is called wavelength division multiplexing.

[0161] DWDM (Dense Wavelength Division Multiplexer) technology utilizes the bandwidth and low-loss characteristics of single-mode optical fiber, employing multiple wavelengths as carriers to allow simultaneous transmission of each carrier channel within the fiber. Compared to conventional single-channel systems, DWDM not only significantly increases the communication capacity of network systems and fully utilizes the bandwidth of optical fibers, but also offers numerous advantages such as simple capacity expansion and reliable performance.

[0162] CWDM (Coarse Wavelength Division Multiplexer), also known as a coarse wavelength division multiplexer, is a low-cost WDM transmission technology for metropolitan area network access layers. In principle, CWDM uses an optical multiplexer to multiplex optical signals of different wavelengths onto a single optical fiber for transmission. At the receiving end of the link, an optical demultiplexer decomposes the mixed signal in the fiber into signals of different wavelengths, which are then connected to the corresponding receiving equipment.

[0163] Quantum signals are particularly fragile, and interference can occur from factors such as sound, vibration, and temperature changes in real-world applications. Furthermore, the thermal expansion and contraction of optical cables, as well as signal crosstalk between different fibers within the same cable, make on-site implementation extremely difficult. Therefore, a stable phase transmission optical transmitter (Tx) is necessary. With a wavelength of 1550.12nm and SBS suppression function, it serves as a high-precision clock frequency transmission device for quantum communication, while effectively suppressing phase noise generated by temperature and strain in quantum communication optical fibers. The wavelength is 1550.92nm for quantum communication transmission.

[0164] When quantum communication is used for transmission with a clock frequency transmission system that has SBS suppression, it requires DWDM (Dense Wavelength Division Multiplexing) or CWDM (Coarse Wavelength Division Multiplexing, e.g.) If the wavelength is 1550.12nm, then quantum communication can choose a wavelength of 1490nm or 1310nm; the quantum communication optical signal can bypass optical amplification equipment such as EDFA and remote pumping through DWDM or CWDM as needed.

[0165] Quantum communication optical signals are orders of magnitude lower than those in stable optical transmission systems. In WDM (DWDM or CWDM) transmission, the adjacent isolation of typical WDM (DWDM or CWDM) devices is less than 30 dB. The optical signal from the stable optical transmission system is prone to crosstalk into the quantum communication optical signal, increasing the RIN noise of the quantum communication laser and the intensity noise of the photodetector. Therefore, it is necessary to improve the adjacent isolation of WDM devices.

[0166] Based on the above, some embodiments of the present invention further include: an optical isolation device, the optical isolation device including an isolator and a TFF type WDM, the isolator being connected to the TFF type WDM, and the input end of the optical isolation device being connected to the output end of the dense wavelength division multiplexing combiner.

[0167] like Figure 15 As shown, Figure 15 This is a schematic diagram of the structure of an optical isolation device in one embodiment of the present invention, as shown below. Figure 15As shown, a two-stage TFF (Thin Film Filter) WDM is used, employing TFF thin film filter technology. DWDM or CWDM methods can be selected. Adjacent isolation: Stage 1 ≥ 30dB, Stage 2 ≥ 60dB.

[0168] like Figure 16 As shown, Figure 16 This is a schematic diagram of an optical isolation device in one embodiment of the present invention. The difference between the present invention and the above is that the secondary TFF type WDM device is replaced with an isolator, so that the adjacent isolation is ≥80dB.

[0169] It should be noted that the isolator is existing technology. This invention does not improve the isolator structure. The improvement method of this invention is to realize two or more stages in series. Those skilled in the art can select the isolator according to actual needs.

[0170] In some embodiments, the first laser is a tunable linewidth laser and the second laser is a narrow linewidth laser; the first laser generates a laser signal with a wavelength of 1550.12 nm; and the second laser generates a laser signal with a wavelength of 1550.92 nm.

[0171] The microwave photonic communication system provided by this invention can be applied to microwave photonic links, microwave photonic ramps (MWP), analog optical links, radio over fiber communication, RF over fiber communication, millimeter wave over fiber communication, terahertz over fiber communication, 5G / 6G transmission, GNSS over fiber, radio telescope / radar fiber arrays, lidar, optical quantum communication, long-distance high-precision fiber time and frequency transmission, etc. This invention achieves SBS suppression based on spectral broadening, which can effectively suppress SBS, thereby suppressing phase jitter caused by temperature changes, strain changes, etc. in microwave photonic transmission. This is beneficial to improving the performance of microwave photonic transmission systems, enabling optical phase conjugation, and suppressing phase noise caused by atmospheric turbulence disturbances, temperature, and environmental strain in lidar or satellite communication.

[0172] In summary, this invention provides a microwave photonic transmission system, comprising: employing appropriate Stimulated Brillouin Scattering (SBS) to suppress phase jitter caused by temperature changes and strain changes (external vibrations, etc.) during microwave photonic transmission; employing centralized Raman Fractional Resonance Amplifier (FRA) to reduce the system's carrier-to-noise ratio (CNR) loss; employing appropriate SBS thresholds to adapt to different transmission distances and using Dispersion Compensation (DCM) to compensate for each fiber repeater segment to suppress system degradation caused by Self-Phase Modulation (SPM) and External Phase Modulation (EPM); and addressing the impact and improvement measures of Relative Intensity Noise (RIN) and Interference Intensity Noise (IIN) on the microwave photonic transmission system. This invention systematically solves the noise problems such as phase jitter in microwave photonic stable phase transmission and also provides various devices and application scenarios based on the microwave photonic stable phase transmission system.

[0173] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0174] It should be noted that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.

[0175] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0176] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A microwave photonic transmission system, characterized in that, include: An optical emitting device is used to obtain a power signal of a first wavelength output by a first laser, wherein the power signal of the first wavelength is a power signal suppressed by SBS. An optical amplification device is connected to the optical emitting device, and the optical amplification device is used to amplify the power of the power signal of the first wavelength; An optical repeater is connected to the optical amplifier. The optical repeater is used to perform optical power compensation on the power signal of the first wavelength and output a power compensation signal of the first wavelength. An optical receiving device is connected to the optical relay device, and the optical receiving device is used to demodulate the power compensation signal of the first wavelength into an electrical signal; The optical emitting device is also used to obtain a power signal of a first wavelength output by the first laser, wherein the power signal of the first wavelength is a power signal with SBS suppression obtained after spectral broadening. Obtain the power signal of the second wavelength output by the second laser; The power signal of the first wavelength and the power signal of the second wavelength are sent to a dense wavelength division multiplexing (DWDM) multiplexer, and the combined power signal is output after DWDM multiplexing.

2. The microwave photonic transmission system according to claim 1, characterized in that, The optical emitting device includes: a first laser, a second laser, and a dense wavelength division multiplexing (DWDM) multiplexer. One input terminal of the dense wavelength division multiplexing combiner is connected to the output terminal of the first laser; The other input of the dense wavelength division multiplexing combiner is connected to the output of the second laser.

3. The microwave photonic transmission system according to claim 1 or 2, characterized in that, Also includes: First Mach-Zehnder modulator and second Mach-Zehnder modulator. The input terminal of the first Mach-Zehnder modulator is connected to the output terminal of the first laser, and is used to receive the power signal of the first wavelength and modulate the power signal of the first wavelength. The input of the second Mach-Zehnder modulator is connected to the output of the second laser to receive the power signal of the second wavelength, with a frequency of f. RF The radio frequency signal is used as the driver of the second Mach-Zehnder modulator to modulate the power signal of the second wavelength.

4. The microwave photonic transmission system according to claim 3, characterized in that, The output of the first Mach-Zehnder modulator is connected to the first input of the dense wavelength division multiplexing combiner. The output of the second Mach-Zehnder modulator is connected to the second input of the dense wavelength division multiplexing combiner.

5. The microwave photonic transmission system according to claim 1 or 2, characterized in that, It also includes a dual parallel Mach-Zehnder modulator, with two input terminals located on two parallel Mach-Zehnder modulators on two branch arms of the dual parallel Mach-Zehnder modulator, one input terminal connected to the first laser and the other input terminal connected to the second laser, and having a frequency of f. RF The input of radio frequency signals.

6. The microwave photonic transmission system according to claim 1, characterized in that, The optical amplification device includes a first optical amplifier and a second optical amplifier, and the optical relay device includes a first dispersion compensation module and a second dispersion compensation module. The first optical amplifier is used to amplify the power signal of the first wavelength to form a first amplified beam signal; The first dispersion compensation module is connected to the first optical amplifier and is used to receive the first amplified beam signal and perform dispersion compensation processing on the first amplified beam signal to form a first compensated beam signal. The second optical amplifier is connected to the first dispersion compensation module and is used to receive the first compensation beam signal and amplify the first compensation beam signal to form a second amplified beam signal. The second dispersion compensation module is connected to the second optical amplifier and is used to receive the second amplified beam signal and perform compensation processing on the second amplified beam signal to form a second compensated beam signal.

7. The microwave photonic transmission system according to claim 6, characterized in that, The first optical amplifier is a preamplifier, and the second optical amplifier is a Raman amplifier.

8. The microwave photonic transmission system according to claim 7, characterized in that, It also includes a remote pumping device disposed between the first optical amplifier and the second optical amplifier, the remote pumping device being used to remotely amplify the first amplified beam signal.

9. The microwave photonic transmission system according to claim 1, characterized in that, Also includes: An optical isolation device, comprising an isolator and a TFF-type WDM, wherein the isolator is connected to the TFF-type WDM, and the input terminal of the optical isolation device is connected to the output terminal of the dense wavelength division multiplexing multiplexer.

Images