Bandwidth and dynamic range reconfigurable microwave photonic link and implementation method

Abstract

The application discloses a microwave photon link with reconfigurable bandwidth and dynamic range and an implementation method thereof, wherein the implementation method comprises the following steps: generating an optical carrier by a laser and injecting the optical carrier into a double parallel Mach-Zehnder modulator, dividing the input end of the double parallel Mach-Zehnder modulator into two beams with a proportionally adjustable ratio, and respectively injecting the two beams into an upper side modulator and a lower side modulator of the double parallel Mach-Zehnder modulator; applying a radio frequency signal to the upper side modulator to modulate the injected optical carrier; the lower side modulator only performs carrier phase control; and performing direct current biasing on the double parallel Mach-Zehnder modulator by a bias control unit, and outputting a modulated optical signal. By adjusting the direct current biasing point of the upper side modulator and optimizing the optical power distribution ratio, the application can respectively realize the suppression of third-order intermodulation distortion and second harmonic distortion, realize two working modes of narrow-band large dynamic and ultra-wideband of the microwave photon link, and the two modes can be flexibly reconfigured.

Description

Technical Field

[0001] This invention relates to the field of microwave photonics technology, and in particular to a microwave photonic link and its implementation method that are reconfigurable in terms of bandwidth and dynamic range. Background Technology

[0002] Microwave photonics technology is a novel interdisciplinary field that integrates microwave and photonic technologies. It generates, transmits, and processes microwave signals in the optical domain, offering advantages over traditional microwave technologies, including broadband, high speed, parallelism, compactness, electromagnetic compatibility, and interference resistance. Externally modulated microwave photonic links possess advantages such as large bandwidth, wide dynamic range, and high reliability, showing promising application prospects. However, electro-optic externally modulated microwave photonic links are prone to nonlinear distortion due to the nonlinear effects of the electro-optic modulator, thus limiting the spurious-free dynamic range. The spurious-free dynamic range is defined as the range of signal input power where the signal output power is greater than the system output noise floor power, and the intermodulation distortion power is less than the system output noise floor power. Intermodulation distortion suppression is one of the most flexible and effective ways to improve the spurious-free dynamic range.

[0003] Several reported microwave photonic links utilize electrical devices for distortion cancellation. However, the frequency-dependent characteristics of these devices limit the suppression of third-order intermodulation distortion within a finite frequency range. Furthermore, reported microwave photonic links for third-order intermodulation distortion suppression in the optical domain, such as those employing silicon-based liquid crystal optical processors for phase modulation of the optical carrier band, polarization phase modulators, and dual-parallel modulators to cancel nonlinear distortion, are typically quite complex to control. The limited second-order spurious-free range caused by second-order intermodulation distortion has received less attention, but it remains a pressing issue for broadband RF systems. Microwave photonic links that can flexibly reconfigure their operating bandwidth and spurious-free dynamic range according to the application scenario can significantly improve system flexibility and reduce costs, yet related research is limited. Summary of the Invention

[0004] This invention proposes a reconfigurable microwave photonic link and its implementation method that adapts to bandwidth and dynamic range. By constructing mutually canceling distortion signals, it achieves dynamic range extension under different bandwidths. The control is simple and flexible, adaptable to different bandwidth and dynamic range requirements, and can be flexibly reconfigured in both narrowband high dynamic range and ultra-wideband operating modes. This invention can be applied to radar, communication, and other systems, and is suitable for various radio frequency systems with reconfigurable bandwidth and dynamic range requirements.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for implementing a reconfigurable microwave photonic link that adapts to bandwidth and dynamic range includes:

[0007] An optical carrier is generated by a laser and injected into a dual parallel Mach-Zehnder modulator. The carrier is split into two proportionally adjustable beams at the input of the dual parallel Mach-Zehnder modulator and injected into the upper and lower sub-modulators of the dual parallel Mach-Zehnder modulator, respectively. The upper and lower sub-modulators are connected in parallel and operate in a push-pull state.

[0008] The radio frequency signal is applied to the upper sub-modulator to modulate the injected optical carrier;

[0009] A DC bias voltage V1 is applied to the upper sub-modulator via the bias control unit, with a bias angle of . A DC bias voltage V2, which is correlated with the upper sub-modulator, is applied to the lower sub-modulator, with a bias angle of . and This invention employs an interrelated bias control method, which avoids the simultaneous fine control of multiple DC bias voltages and greatly simplifies the difficulty of bias control.

[0010] A fixed DC bias voltage V3 is applied to the main modulator of the dual parallel Mach-Zehnder modulator by the bias control unit, so that the optical signal field strength of the upper and lower paths generates a 180° phase difference and outputs the modulated optical signal.

[0011] Furthermore, the modulated optical signal output by the dual parallel Mach-Zehnder modulator, after transmission, can be detected by a square law and converted by a photodetector to recover the radio frequency signal.

[0012] Furthermore, the expression for the modulated optical signal output by the dual parallel Mach-Zehnder modulator includes:

[0013]

[0014] in, Let P be the electric field of the optical carrier, P be the optical power of the optical carrier, and ω be the electric field of the optical c α is the optical carrier angular frequency; α is the optical power distribution ratio of the optical carrier in the upper path; m = πV RF / V π V is the modulation coefficient. RF V represents the amplitude of the radio frequency signal. π The half-wave voltage of the upper sub-modulator; bias angle Offset angle ω1 and ω2 are the angular frequencies of the radio frequency signal, which is a two-tone signal.

[0015] Furthermore, after the modulated optical signal is input to the photodetector, the photocurrent I with third-order intermodulation distortion generated by the optical carrier, sideband Selfie frequency, and cross-timer frequency... IMD3 The expressions include:

[0016]

[0017] Among them, J n (m) is a Bessel function of the first kind; the photocurrents generated by the optical carrier and sideband self-beat frequency of the upper sub-modulator are I1, I2, and I3, respectively, and the photocurrent generated by the mutual beat frequency of the sideband of the upper sub-modulator and the carrier of the lower sub-modulator is I4.

[0018] Furthermore, by expanding the Bessel function of the first kind and setting the sum of all third-order intermodulation distortions to zero, we obtain the condition for eliminating third-order intermodulation distortion as follows:

[0019]

[0020] There exists an optimal offset angle. The optical power allocation ratio α satisfies the optimal conditions for complete suppression of third-order intermodulation distortion and third-order spurious-free dynamic range.

[0021] Furthermore, by optimizing the optical power allocation ratio α and the offset angle... By making the amplitude of the photocurrent I4 equal to the sum of I1, I2, and I3, and their phases opposite, the third-order intermodulation distortion suppression and the optimization of the third-order spurious-free dynamic range are achieved, thus completing the configuration of the narrowband large dynamic range operating mode of the microwave photonic link.

[0022] Furthermore, after the modulated optical signal is input to the photodetector, the expression for the photocurrent that generates second harmonic distortion due to the optical carrier, sideband Selfie frequency, and cross-timer frequency includes:

[0023]

[0024] Among them, J n (m) is a Bessel function of the first kind; the photocurrents generated by the carrier and sideband self-beat frequency of the upper sub-modulator are I'1 and I'2, respectively, and the photocurrent generated by the mutual beat frequency of the sideband of the upper sub-modulator and the carrier of the lower sub-modulator is I'3; the bias angle applied to the lower modulator...

[0025] Furthermore, by expanding the Bessel function of the first kind and setting the sum of all second-harmonic distortion products to zero, the condition for suppressing second-harmonic distortion is obtained as follows:

[0026]

[0027] Since the conditions for the generation and suppression of second-order intermodulation distortion and second-harmonic distortion in the link are the same, based on the link's bandwidth requirements, this analysis focuses only on second-harmonic distortion suppression. An optimal offset angle exists. The optical power allocation ratio α' satisfies the optimal conditions for complete suppression of second-order intermodulation distortion / second-harmonic distortion and second-order spurious-free dynamic range.

[0028] Furthermore, by optimizing the optical power allocation ratio α' and the offset angle... By making the amplitudes of the photocurrents I'1 and the sum of I'2 and I'3 equal and their phases opposite, the second-order intermodulation distortion / second-harmonic distortion and the second-order spurious-free dynamic range are optimized, thus completing the configuration of the ultra-wideband operating mode of the microwave photonic link.

[0029] This invention eliminates the need for complex control of multiple bias points. By simply optimizing the bias angle and optical power distribution ratio of the sub-modulators on the dual parallel Mach-Zehnder modulator, it enables flexible reconfiguration of both narrowband and ultra-wideband operating modes of the microwave photonic link.

[0030] A reconfigurable microwave photonic link with adaptable bandwidth and dynamic range includes a laser, a dual parallel Mach-Zehnder modulator, a bias control unit, and a photodetector. The dual parallel Mach-Zehnder modulator includes an upper sub-modulator, a lower sub-modulator, and a main modulator. The upper and lower sub-modulators are connected in parallel and operate in a push-pull state. The upper and lower sub-modulators are located on the upper and lower arms of the main modulator, respectively.

[0031] The laser generates an optical carrier and injects it into a dual parallel Mach-Zehnder modulator. At the input of the dual parallel Mach-Zehnder modulator, the laser is split into two proportionally adjustable beams, which are injected into the upper sub-modulator and the lower sub-modulator, respectively. The upper sub-modulator is also subjected to a radio frequency signal to modulate the injected optical carrier.

[0032] The bias control unit is configured to apply a DC bias voltage V1 to the upper submodulator, with a bias angle of . A DC bias voltage V2, which is correlated with the upper sub-modulator, is applied to the lower sub-modulator, with a bias angle of . and A fixed DC bias voltage V3 is applied to the main modulator to create a 180° phase difference between the upper and lower optical signal field strengths and output modulated optical signals.

[0033] The photodetector is configured to perform square-rate detection, realize the beat between the optical carrier and its sidebands, and recover the radio frequency signal.

[0034] The beneficial effects of this invention are as follows:

[0035] 1. This invention constructs mutually canceling distortion signals by controlling a single bias point and optical power distribution ratio of a dual parallel Mach-Zehnder modulator, enabling microwave photonic links to adapt to ultra-wideband and narrowband high dynamic range applications, and allowing flexible reconfiguration of the two operating modes. In this invention, the upper and lower sub-modulators of the dual parallel Mach-Zehnder modulator use interconnected bias voltages, while the main modulator uses a fixed DC bias voltage. Only the adjustment of a single bias point and the optical power distribution ratio is needed to achieve ultra-wideband and narrowband high dynamic range operating modes respectively. The flexible reconfiguration of the two modes greatly simplifies the system's control complexity.

[0036] 2. This invention does not require complex hardware components, has a simple structure, and greatly reduces the size and weight of microwave photonic links; by integrating microwave photonic links into multiple channels, the hardware size can be further reduced to meet the requirements of compact installation environments.

[0037] In summary, compared with existing microwave photonic links, this invention has the advantages of simple structure and easy control. By adjusting the optical power distribution ratio of the dual parallel Mach-Zehnder modulators and a bias control point, it is possible to suppress third-order intermodulation distortion / second-harmonic distortion, enabling the microwave photonic link to have two working modes: narrowband with large dynamic range and ultra-wideband. Moreover, the two working modes can be quickly reconfigured to meet the needs of different application scenarios. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a microwave photonic link device with reconfigurable bandwidth and dynamic range according to Embodiment 1 of the present invention.

[0039] Figure 2 This is a schematic diagram of the spectrum and electrical spectrum in the narrowband large dynamic mode of Embodiment 2 of the present invention.

[0040] Figure 3 This is a schematic diagram of the spectrum and electrical spectrum in the ultra-wideband mode of Embodiment 3 of the present invention.

[0041] Figure 4 This is a comparison between the third-order spurious-free dynamic range in the narrowband large dynamic mode of Embodiment 2 of the present invention and the existing third-order spurious-free dynamic range based on the MZM microwave photonic link.

[0042] Figure 5 These are the second-order and third-order spurious-free dynamic ranges of the link in the ultra-wideband mode of Embodiment 3 of the present invention.

[0043] Figure reference numerals: MZM is a Mach-Zehnder modulator, DPMZM is a dual parallel Mach-Zehnder modulator, MZM1 is the upper sub-modulator, MZM2 is the lower sub-modulator, and MZM3 is the master modulator; bias1, bias2, and bias3 are the bias voltage control points applied to MZM1, MZM2, and MZM, respectively; IMD2 is second-order intermodulation distortion, and IMD3 is third-order intermodulation distortion; SFRD2 is second-order spurious-free dynamic range, and SFRD3 is third-order spurious-free dynamic range. Detailed Implementation

[0044] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments are now described. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0045] Example 1

[0046] like Figure 1 As shown, this embodiment provides a reconfigurable microwave photonic link with adaptable bandwidth and dynamic range, including a laser, a dual parallel Mach-Zehnder modulator, a bias control unit, and a photodetector. The laser provides the optical carrier; the dual parallel Mach-Zehnder modulator includes an upper sub-modulator, a lower sub-modulator, and a main modulator. The upper and lower sub-modulators are connected in parallel and operate in a push-pull configuration, located on opposite arms of the main modulator; the bias control unit applies a DC voltage to the upper, lower, and main modulators and controls the DC voltage to operate at the target operating point; the photodetector is configured to perform square-law detection to detect the beat between the optical carrier and its sidebands, recovering the radio frequency signal.

[0047] Accordingly, this embodiment also provides a method for implementing a microwave photonic link that is adaptable to bandwidth and dynamic range reconfigurability, including:

[0048] An optical carrier is generated by a laser and injected into a dual parallel Mach-Zehnder modulator. The input of the dual parallel Mach-Zehnder modulator is split into two proportionally adjustable beams and injected into the upper and lower sub-modulators of the dual parallel Mach-Zehnder modulator respectively. The upper and lower sub-modulators are connected in parallel and operate in a push-pull state.

[0049] The radio frequency signal is applied to the upper sub-modulator to modulate the injected optical carrier;

[0050] A DC bias voltage V1 is applied to the upper sub-modulator via the bias control unit, with a bias angle of . A DC bias voltage V2, which is correlated with the upper sub-modulator, is applied to the lower sub-modulator, with a bias angle of . and This embodiment uses an interrelated bias control method, which can avoid the simultaneous fine control of multiple DC bias voltages and greatly simplify the difficulty of bias control.

[0051] A fixed DC bias voltage V3 is applied to the main modulator by the bias control unit, so that the optical signal field strength of the upper and lower paths are 180° phased, and the modulated optical signal is output.

[0052] The modulated optical signal output from the dual-parallel Mach-Zehnder modulator, after transmission, can be detected by a photodetector using square law detection and photoelectric conversion to recover the radio frequency (RF) signal. The recovered RF signal and its various distortions are essentially generated by the superposition of photocurrents due to the beat frequencies between the optical carrier and optical sidebands, and between the optical sidebands themselves. In this embodiment, an additional phase shift is introduced into the optical carrier in the lower sub-modulator of the dual-parallel Mach-Zehnder modulator, and it is coherently synthesized with the upper modulated optical signal. Therefore, the photodetector signal contains both the photocurrent generated by the self-beat frequency between the upper sub-modulator's optical sideband and the optical carrier, and the photocurrent generated by the beat frequencies between the upper sub-modulator's optical sideband and the lower modulator's optical carrier. By adjusting the bias voltage applied to the upper sub-modulator, multiple distortion components generated by the self-beat frequency and the beat frequencies can be canceled out, ensuring that the microwave photonic link can operate in a narrowband, high dynamic range, and ultra-wideband mode. Furthermore, the two operating modes can be flexibly switched by adjusting the bias voltage.

[0053] Therefore, the reconfiguration between the narrowband high dynamic range operating mode and the ultra-wideband operating mode in the microwave photonic link can be achieved by adjusting the optical power allocation ratio and the bias angle applied to the upper sub-modulator, which is simple to control.

[0054] It should be noted that the bandwidth of microwave photonic links is affected by the inherent bandwidth of the devices and cross-octave distortion signals. In recent years, device capabilities have improved rapidly, broadband devices are readily available, and improving the bandwidth of the devices themselves is not the focus of this invention. The ultra-wideband referred to in this invention means that the link bandwidth is not limited by cross-octave distortion signals.

[0055] Example 2

[0056] This embodiment is based on embodiment 1:

[0057] This embodiment provides a method for implementing a microwave photonic link with reconfigurable bandwidth and dynamic range, which can be used to realize a narrowband high dynamic range operating mode.

[0058] When a two-tone signal with angular frequencies of ω1 and ω2 is applied to the upper sub-modulator, the output spectrum of the dual parallel Mach-Zehnder modulator and the suppression of third-order intermodulation distortion after photoelectric conversion are as follows: Figure 2 As shown. Among them, the third-order intermodulation distortion with angular frequency of 2ω1-ω2(2ω2-ω1) can be generated by the optical carrier and sideband generated by the upper sub-modulator at the photodetector self-beat frequency, with three main contributors, generating photocurrents I1, I2, and I3 respectively; it can also be generated by the inter-beat frequency of the optical sideband generated by the upper sub-modulator and the optical carrier generated by the lower sub-modulator, generating photocurrent I4.

[0059] Assume that a bias voltage is applied to the bias angle generated by the upper sub-modulator. And set the bias angle of the lower-path modulator to be Set to with Interrelated, and Simultaneously, the main modulator is biased at its minimum point, causing a 180° phase difference between the upper and lower optical signal field strengths. Through optimization... This allows I4 to have the same amplitude as the sum of I1, I2, and I3, but opposite phase, thereby achieving third-order intermodulation distortion suppression, improving spurious-free dynamic range, and enabling narrowband large dynamic range working mode configuration.

[0060] Specifically, the microwave photonic link implementation method of this embodiment can be implemented by the following steps:

[0061] (1) The continuous light generated by the laser is injected into the dual parallel Mach-Zehnder modulator and split into two proportionally adjustable beams, which are then input into the upper sub-modulator and the lower sub-modulator, respectively.

[0062] (2) Apply radio frequency dual-tone signals with angular frequencies of ω1 and ω2 to the upper sub-modulator of the upper path to modulate the injected optical carrier, while the lower sub-modulator has no radio frequency input.

[0063] (3) The bias control unit applies bias voltages to the bias voltage control points Bias1, Bias2, and Bias3 of the dual parallel Mach-Zehnder modulator, respectively. The bias control unit applies a DC bias to the upper sub-modulator, with a bias angle... Apply a DC bias to the lower submodulator that is correlated with the upper submodulator. Both the upper and lower sub-modulators operate in push-pull mode.

[0064] (4) The bias master modulator is positioned at its minimum point, causing a 180° phase difference between the upper and lower optical signal field strengths. The output optical signal can be expressed as:

[0065]

[0066] in, Let P be the electric field of the optical carrier, P be the optical power of the optical carrier, and ω be the electric field of the optical c α is the optical carrier angular frequency; α is the optical power distribution ratio of the optical carrier in the upper path; m = πV RF / V π V is the modulation coefficient. RF V represents the amplitude of the radio frequency signal. π The half-wave voltage of the upper sub-modulator; bias angle Offset angle

[0067] As can be seen from the above formula, the output optical field includes the optical carrier, harmonics, and intermodulation distortion from the upper sub-modulator, as well as the phase-modulated optical carrier from the lower sub-modulator.

[0068] (5) The modulated optical signal is input to the photodetector, and a third-order intermodulation distortion photocurrent I is generated by the optical carrier and the self-beat frequency and cross-beat frequency of each sideband. IMD3 It can be represented as:

[0069]

[0070] Among them, J n (m) is a Bessel function of the first kind. The photocurrents generated by the carrier and sideband beat frequencies of the upper sub-modulator are I1, I2, and I3, respectively; the photocurrent generated by the beat frequencies of the upper sub-modulator sideband and the lower sub-modulator carrier is I4.

[0071] (6) Expanding the Bessel function of the first kind and setting the sum of all third-order intermodulation distortions in the above equation to zero, we can see that the condition for eliminating third-order intermodulation distortion is:

[0072]

[0073] There exists an optimal offset angle. And α (0 < α < 1), satisfying the optimization conditions for complete suppression of third-order intermodulation distortion and the third-order spurious-free dynamic range. There exists an optimal α, when α ≈ 0.55, the output signal amplitude is maximized, and the third-order spurious-free dynamic range is maximized. A comparison of the third-order spurious-free dynamic range of the microwave photonic link with that of existing MZM-based microwave photonic links is shown below. Figure 4 As shown, the third-order spurious-free dynamic range is improved by approximately 19 dB.

[0074] Example 3

[0075] This embodiment is based on embodiment 1:

[0076] This embodiment provides a method for implementing a microwave photonic link with reconfigurable bandwidth and dynamic range, which is used to realize an ultra-wideband operating mode.

[0077] When a two-tone signal with angular frequencies of ω1 and ω2 is applied to the upper sub-modulator, the output spectrum of the dual parallel Mach-Zehnder modulator and the suppression of second harmonic distortion after photoelectric conversion are as follows: Figure 3 As shown. The second harmonic distortion with an angular frequency of 2ω1 (2ω2) can be generated at the photodetector self-beat frequency by the optical carrier and sideband generated by the upper sub-modulator, with two main contributors, producing photocurrents I'1 and I'2 respectively; it can also be generated by the inter-beat frequency of the optical sideband generated by the upper sub-modulator and the optical carrier generated by the lower sub-modulator, producing a photocurrent I'3. The bias voltage is applied in the same way as in the large dynamic range mode described above, by optimizing the optical power distribution ratio α' and... This allows the sum of I'1 and I'2, I'3 to have equal amplitudes but opposite phases, thereby achieving second harmonic distortion suppression and enabling the configuration of the microwave photonic link's ultra-wideband operating mode.

[0078] Specifically, the microwave photonic link implementation method of this embodiment can be implemented by the following steps:

[0079] (1) The continuous light generated by the laser is injected into the dual parallel Mach-Zehnder modulator and split into two proportionally adjustable beams, which are then input into the upper sub-modulator and the lower sub-modulator, respectively.

[0080] (2) Apply radio frequency dual-tone signals with angular frequencies of ω1 and ω2 to the upper sub-modulator of the upper path to modulate the injected optical carrier, while the lower sub-modulator has no radio frequency input.

[0081] (3) The bias control unit applies bias voltages to the bias voltage control points Bias1, Bias2, and Bias3 of the dual parallel Mach-Zehnder modulator, respectively. The bias control unit applies a DC bias to the upper sub-modulator, with a bias angle... Apply a DC bias to the lower submodulator that is correlated with the upper submodulator. Both the upper and lower sub-modulators operate in push-pull mode.

[0082] (4) The bias master modulator is positioned at its minimum point, causing a 180° phase difference between the upper and lower optical signal field strengths. The output optical signal can be expressed as:

[0083]

[0084] in, Let P be the electric field of the optical carrier, P be the optical power of the optical carrier, and ω be the electric field of the optical c α is the optical carrier angular frequency; α is the optical power distribution ratio of the optical carrier in the upper path; m = πV RF / V π V is the modulation coefficient.RF V represents the amplitude of the radio frequency signal. π The half-wave voltage of the upper sub-modulator; bias angle Offset angle

[0085] As can be seen from the above formula, the output optical field includes the optical carrier, harmonics, and intermodulation distortion from the upper sub-modulator, as well as the optical carrier after phase modulation from the lower sub-modulator.

[0086] (5) The modulated optical signal is input to the photodetector. The photocurrent with second harmonic distortion generated by the optical carrier and the sideband self-beat frequency and cross-beat frequency can be expressed as:

[0087]

[0088] The photocurrents generated by the self-beating frequencies of the upper sub-modulator carrier and sideband are I'1 and I'2, respectively; the photocurrent generated by the mutual beat frequencies of the upper sub-modulator sideband and the lower sub-modulator carrier is I'3. The bias angle applied to the lower sub-modulator...

[0089] (6) Expanding the Bessel function of the first kind in the above equation and setting the sum of all second harmonic distortion products in the above equation to zero, we can find that the condition for eliminating second harmonic distortion is:

[0090]

[0091] There exists an optimal offset angle. The power distribution ratio α' (0 < α' ≤ 1) satisfies the optimal conditions for complete suppression of second harmonic distortion and second-order spurious-free dynamic range. When α' = 1, When k = 0, ±1,..., the second harmonic distortion suppression is strongest, and the ratio of the detected output signal power to the third-order intermodulation distortion signal is largest, meaning that the second-order and third-order spurious-free dynamic ranges of the microwave photonic link are optimized in ultra-wideband operating mode. At this time, the second-order and third-order spurious-free dynamic ranges of the ultra-wideband microwave photonic link are as follows: Figure 5 As shown.

[0092] It should be noted that, for the sake of simplicity, the foregoing method embodiments are described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

Claims

1. A method for implementing a reconfigurable microwave photonic link with adaptable bandwidth and dynamic range, characterized in that, include: An optical carrier is generated by a laser and injected into a dual parallel Mach-Zehnder modulator. The carrier is split into two proportionally adjustable beams at the input of the dual parallel Mach-Zehnder modulator and injected into the upper and lower sub-modulators of the dual parallel Mach-Zehnder modulator, respectively. The upper and lower sub-modulators are connected in parallel and operate in a push-pull state. The radio frequency signal is applied to the upper sub-modulator to modulate the injected optical carrier; A DC bias voltage is applied to the up-path submodulator via the bias control unit. V 1. Offset angle is And apply a DC bias voltage to the lower sub-modulator that is correlated with the upper sub-modulator. V 2, the offset angle is ,and ; A fixed DC bias voltage is applied to the main modulator of the dual parallel Mach-Zehnder modulator by a bias control unit. V 3. Create a 180° phase difference between the upper and lower optical signal field strengths and output a modulated optical signal; The expression for the modulated optical signal output by the dual parallel Mach-Zehnder modulator includes: in, For optical carrier electric field, For optical carrier power, It is the optical carrier angular frequency; This refers to the optical power allocation ratio of the optical carrier in the uplink; The modulation coefficient, For radio frequency signal amplitude, The half-wave voltage of the upper sub-modulator; bias angle Offset angle ; and ω is the angular frequency of the radio frequency signal, which is a two-tone signal; After the modulated optical signal is input to the photodetector, the photocurrent with third-order intermodulation distortion generated by the optical carrier, sideband Selfie frequency, and inter-timer frequency... The expressions include: in, It is a Bessel function of the first kind; the photocurrents generated by the optical carrier and the sideband Selfie frequency after passing through the upper sub-modulator are respectively , , The photocurrent generated by the inter-frequency beat between the upper sub-modulator sideband and the lower sub-modulator carrier is ; Expanding the Bessel function of the first kind and setting the sum of all third-order intermodulation distortions to zero, we obtain the condition for eliminating third-order intermodulation distortion as follows: There exists an optimal offset angle. and optical power allocation ratio It satisfies the optimal conditions for complete suppression of third-order intermodulation distortion and the third-order spurious-free dynamic range; By optimizing the optical power allocation ratio and offset angle , to make photocurrent and , , The sum of the three has equal amplitude and opposite phase, thereby achieving the optimization of third-order intermodulation distortion suppression and third-order spurious-free dynamic range, and completing the configuration of the microwave photonic link's narrowband large dynamic range working mode. After the modulated optical signal is input to the photodetector, the expression for the photocurrent that generates second harmonic distortion due to the optical carrier, sideband Selfie frequency, and cross-timer frequency includes: in, It is a Bessel function of the first kind; the photocurrents generated by the carrier and sideband Selfie frequencies of the upper sub-modulator are respectively and The photocurrent generated by the inter-frequency beat between the upper sub-modulator sideband and the lower sub-modulator carrier is Apply the bias angle to the sub-modulator. ; Expanding the Bessel function of the first kind and setting the sum of all second-harmonic distortion products to zero, we obtain the condition for eliminating second-harmonic distortion as follows: There exists an optimal offset angle. and optical power allocation ratio The optimal conditions for complete suppression of second harmonic distortion and second-order spurious-free dynamic range are met. By optimizing the optical power allocation ratio and offset angle , to make photocurrent and , The sum of the two has equal amplitude and opposite phase, thereby achieving the suppression of second harmonic distortion and the optimization of the second-order spurious-free dynamic range, and completing the configuration of the ultra-wideband operating mode of the microwave photonic link.

2. The method for implementing a reconfigurable microwave photonic link with adaptable bandwidth and dynamic range according to claim 1, characterized in that, The modulated optical signal output by the dual parallel Mach-Zehnder modulator, after transmission, can be detected by a square law and converted by a photodetector to recover the radio frequency signal.

3. A microwave photonic link adaptable to bandwidth and dynamic range, employing the microwave photonic link implementation method of claim 1, characterized in that, It includes a laser, a dual parallel Mach-Zehnder modulator, a bias control unit, and a photodetector. The dual parallel Mach-Zehnder modulator includes an upper sub-modulator, a lower sub-modulator, and a main modulator. The upper and lower sub-modulators are connected in parallel and operate in a push-pull state. The upper and lower sub-modulators are located on the upper and lower arms of the main modulator, respectively. The laser generates an optical carrier and injects it into a dual parallel Mach-Zehnder modulator. At the input of the dual parallel Mach-Zehnder modulator, the laser is split into two proportionally adjustable beams, which are injected into the upper sub-modulator and the lower sub-modulator, respectively. The upper sub-modulator is also subjected to a radio frequency signal to modulate the injected optical carrier. The bias control unit is configured to apply a DC bias voltage to the uplink submodulator. V 1. Offset angle is And apply a DC bias voltage to the lower sub-modulator that is correlated with the upper sub-modulator. V 2, the offset angle is ,and ; and applying a fixed DC bias voltage to the main modulator. V 3. Create a 180° phase difference between the upper and lower optical signal field strengths and output a modulated optical signal; The photodetector is configured to perform square-rate detection, realize the beat between the optical carrier and its sidebands, and recover the radio frequency signal.

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