A microwave photonic frequency mixer based on optical add-drop filtering and optoelectronic oscillation

Abstract

The application discloses a microwave photon mixer based on optical add-drop filtering and photoelectric oscillation, which comprises a laser, an optical modulation and filtering processing chip, a photoelectric detection unit and a microwave amplifier. The optical modulation and filtering processing chip comprises a first optical coupler, a first phase modulator, a second phase modulator, a narrow-band flat-top optical filter, an optical add-drop filter and a second optical coupler; the photoelectric detection unit comprises a balanced detector and a photoelectric detector. The laser outputs an optical carrier, is connected with the optical modulation and filtering processing chip, and completes radio frequency modulation, local oscillation modulation and sideband selection; the optical add-drop filter is coupled with the photoelectric detector, is then connected with the microwave amplifier, and is then loaded into a radio frequency input port of the second phase modulator to realize photoelectric oscillation and generate a local oscillation signal; the optical signal output by the second optical coupler is coupled with the balanced detector to obtain a required mixed frequency signal. The application does not need an external electrical local oscillation source, simplifies the structure and has the advantage of full integration.

Description

Technical Field

[0001] This invention belongs to the field of microwave photonics technology and relates to microwave photonic mixers, specifically to a microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation. Background Technology

[0002] Mixers are key components in both the transmitting and receiving ends of electronic systems. Modern electronic systems increasingly demand wide-bandwidth, high-isolation, and high-dynamic-range microwave mixers. Microwave photonic mixing inherits the advantages of microwave photonics technology, such as wide bandwidth, frequency tunability, high isolation, and no electromagnetic interference, giving it inherent technological advantages over traditional microwave mixing. Microwave photonic mixing technology can be broadly categorized into different structures, including direct-modulation, series external modulation, and parallel external modulation. Based on these basic mixing architectures, researchers have used different electro-optic modulators to optimize key frequency conversion indicators (efficiency, isolation, nonlinearity), image frequency suppression, and self-interference elimination, proposing several optimization methods. However, most operations require an external local oscillator, and in practical applications, the operating frequency is limited by the tuning range of the external local oscillator. Therefore, it is necessary to combine microwave photonic mixing technology with photonic signal generation technology to achieve tunable microwave photonic mixing with self-generated local oscillator signals.

[0003] Myunghun Shin et al. proposed a self-generated local oscillator (LO) mixing scheme based on a series MAZ modulator. This scheme employs two cascaded MAZ modulators. The first stage performs RF modulation, and the second stage modulator is split into two paths via an optical coupler. One path combines a long optical fiber with an energy storage element, a photodetector, and an electrical amplifier to form an opto-oscillator that modulates the LO signal with itself. The other path outputs to the photodetector for photoelectric conversion, producing a mixed signal. This scheme uses a series-type microwave photonic frequency conversion, resulting in numerous harmonic noises at the output. The opto-oscillator requires an electrical filter and a long optical fiber delay line, limiting the tuning range and hindering integration.

[0004] Bo Yang et al. proposed a self-generated frequency conversion scheme for the local oscillator signal based on a dual parallel MACD modulator. This scheme uses two sub-modulators of the dual parallel MACD modulator to perform local oscillator modulation and intermediate frequency (IF) signal modulation respectively. The modulator output signal simultaneously contains both the local oscillator-modulated optical signal and the IF-modulated optical signal, which are split into two paths by a coupler. One path passes through an optical fiber delay line, a detector, an electrical filter, and an electrical amplifier before being connected to the local oscillator modulation port of the modulator, forming a photoelectric oscillator. The signals output from the two photodetectors have significant noise, necessitating the use of an electrical filter, and the tuning range is limited. It also requires a long optical fiber delay line, which is not conducive to integration.

[0005] Feng Yang et al. proposed a self-generated frequency conversion scheme for the local oscillator signal based on a polarization-multiplexed dual parallel Markov modulator. This scheme integrates two dual parallel Markov modulators with different polarization states, enabling functions such as carrier suppression single-sideband and band-sideband modulation. Combined with an optical filter, the harmonics output from the frequency conversion branch detector are suppressed, and up / down conversion switching can be achieved by adjusting the modulator's bias voltage. However, this scheme requires an electrical filter and a 90° bridge to limit the tuning range. Furthermore, the use of long fiber delay lines and polarization controllers makes integration impossible. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation, thereby solving the technical problem that the self-generation of the local oscillator signal in existing technologies cannot achieve full integration.

[0007] Another objective of this invention is to provide a microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation, which solves the technical problem that the link loss of the local oscillator signal needs to be further reduced in the prior art.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation includes a laser, an optical modulation and filtering chip, a photoelectric detection unit, and a microwave amplifier.

[0010] The laser is used to output an optical carrier and is connected to an optical modulation and filtering chip and a photoelectric detection unit from left to right.

[0011] In the aforementioned optical modulation and filtering chip, the input end of the first optical coupler is connected to the laser, and the output end of the first optical coupler is split into two paths. The first output end of the first optical coupler is connected to the optical input end of the first phase modulator, and the second output end of the first optical coupler is connected to the optical input end of the second phase modulator.

[0012] The optical output terminal a of the first phase modulator is connected to the input terminal of the narrowband flat-top optical filter, and the output terminal c of the narrowband flat-top optical filter is connected to the first input terminal of the second optical coupler.

[0013] The optical output terminal b of the second phase modulator is connected to the input terminal of the optical add-drop filter, and the input terminal d of the optical add-drop filter is connected to the second input terminal of the second optical coupler.

[0014] The photoelectric detection unit includes a balanced detector. The first output terminal f1 and the second output terminal f2 of the second optical coupler are both connected to the balanced detector. The output terminal g of the balanced detector outputs a frequency conversion signal.

[0015] The photoelectric detection unit further includes a photodetector. The through-terminal e of the optical add-drop filter is connected to the photodetector. The photodetector is connected to the microwave amplifier. The output of the microwave amplifier is connected to the radio frequency input port of the second phase modulator, forming a photoelectric oscillation loop.

[0016] The present invention also has the following technical features:

[0017] The second phase modulator performs local oscillator modulation, and the local oscillator modulated optical signal includes a +1st order sideband, an optical carrier, and a -1st order sideband.

[0018] The optical add-drop filter performs sideband selection on the local oscillator modulated optical signal.

[0019] The filtering spectra of the through end e and the download end d of the optical add-drop filter are complementary. The through end e of the optical add-drop filter is a narrowband notch filter used to filter out the optical signal required to realize the photoelectric oscillation loop. The download end of the optical add-drop filter is a bandpass filter used to filter out one of the sidebands of the local oscillator modulation signal.

[0020] The optical add-drop filter is a high-Q, narrow-bandwidth filter, which can be implemented by a micro-ring resonator or a micro-disk resonator.

[0021] The first phase modulator performs radio frequency modulation, and the radio frequency modulated optical signal includes a +1st order sideband, an optical carrier, and a -1st order sideband.

[0022] The narrowband flat-top optical filter performs sideband selection on the radio frequency modulated optical signal.

[0023] The narrowband flat-top optical filter can be implemented by cascading micro-ring resonators, cascading micro-disk resonators, or micro-ring-assisted MZI filters.

[0024] Compared with the prior art, the present invention has the following technical effects:

[0025] (I) The microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation proposed in this invention combines microwave photonic broadband mixing technology with photonic broadband signal generation technology based on photoelectric oscillators, which can realize broadband tunable microwave photonic mixing with self-generated local oscillator signal.

[0026] (II) This invention utilizes the complementary characteristics of the filtering spectra of the two ports of the optical add-drop filter to complete the sideband selection function in the optoelectronic oscillator and mixer module without the need for an additional optical splitter, thus simplifying the structure and reducing link loss.

[0027] (III) The optoelectronic oscillator constructed by the present invention does not require a long optical fiber delay line, and all devices can be chip devices, realizing full chip integration, which can reduce the size and weight compared with the existing technology.

[0028] (IV) In this invention, by adjusting the center frequencies of the narrowband flat-top optical filter and the optical add-drop filter, the tuning of the LO and RF operating frequencies and the switching between up and down conversion can be realized. It has great application value and market prospects in broadband, multi-band RF transceivers. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation of the present invention.

[0030] Figure 2 These are schematic diagrams of the spectral and electrical spectra at different locations provided in embodiments of the present invention; Figure 2 (a) in the figure is the spectrum of the output signal at the optical output terminal a of the first phase modulator; Figure 2 (b) in the diagram is the spectrum of the output signal at the optical output terminal b of the second phase modulator; Figure 2 (c) in the diagram represents the spectrum output from the output terminal c of the narrowband flat-top filter. Figure 2 In the diagram, (d) represents the spectrum output from the download end d of the optical interleaving filter;

[0031] Figure 2 In the diagram, (e) represents the spectrum output from the through-hole e of the optical interleaving filter. Figure 2 (f1) and (f2) are the spectral diagrams output from the first output terminal f1 and the second output terminal f2 of the second optical coupler; Figure 2 The electrical spectrum output from the (g) balanced detector at terminal g; where, Figure 2 In figure (c), the dashed line represents the spectrum of a narrowband flat-top filter; Figure 2 The dashed lines in (d) and (e) represent the spectrum of the optical interpolation filter.

[0032] The meanings of the labels in the figure are as follows: 1-Laser, 2-Optical modulation and filtering chip, 3-Photodetector unit, 4-First optical coupler, 5-First phase modulator, 6-Second phase modulator, 7-Narrowband flat-top optical filter, 8-Optical add-drop filter, 9-Second optical coupler, 10-Balanced detector, 11-Photodetector, 12-Microwave amplifier.

[0033] The specific content of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, all components and devices in this invention are based on components and devices known in the prior art.

[0035] This invention provides a microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation, wherein:

[0036] Includes a laser for outputting an optical carrier;

[0037] It includes optical modulation and filtering processing chips, used for local oscillator modulation, radio frequency modulation, sideband selection, and output of optical signals required for frequency conversion and photoelectric oscillation;

[0038] Includes a photoelectric detection unit for photoelectric conversion, outputting a frequency conversion signal and an electrical local oscillator signal generated by a photoelectric oscillator;

[0039] This includes microwave amplifiers and local oscillator amplifiers for optoelectronic oscillation loops.

[0040] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0041] Example:

[0042] This embodiment presents a microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation, such as... Figure 1 As shown, a microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation includes a laser 1, an optical modulation and filtering chip 2, a photoelectric detection unit 3, and a microwave amplifier 12.

[0043] Specifically, laser 1, used to output optical carrier, is connected from left to right to optical modulation and filtering chip 2 and photoelectric detection unit 3;

[0044] like Figure 1 As shown, in the optical modulation and filtering chip 2, the input end of the first optical coupler 4 is connected to the laser 1, and the output end of the first optical coupler 4 is split into two paths. The first output end of the first optical coupler 4 is connected to the optical input end of the first phase modulator 5, and the second output end of the first optical coupler 4 is connected to the optical input end of the second phase modulator 6.

[0045] like Figure 1 As shown, the optical output terminal a of the first phase modulator 5 is connected to the input terminal of the narrowband flat-top optical filter 7, and the output terminal c of the narrowband flat-top optical filter 7 is connected to the first input terminal of the second optical coupler 9.

[0046] like Figure 1As shown, the optical output terminal b of the second phase modulator 6 is connected to the input terminal of the optical add-drop filter 8, and the input terminal d of the optical add-drop filter 8 is connected to the second input terminal of the second optical coupler 9.

[0047] like Figure 1 As shown, the photoelectric detection unit 3 includes a balanced detector 10. The first output terminal f1 and the second output terminal f2 of the second optical coupler 9 are both connected to the balanced detector 10. The output terminal g of the balanced detector 10 outputs a frequency conversion signal.

[0048] like Figure 1 As shown, the photoelectric detection unit 3 also includes a photodetector 11. The through end e of the optical interpolation filter 8 is connected to the photodetector 11. The photodetector 11 is connected to the microwave amplifier 12. The output end of the microwave amplifier 12 is connected to the radio frequency input port of the second phase modulator 6 to form a photoelectric oscillation loop.

[0049] Specifically, laser 1 is used to output an optical carrier, which is coupled to the optical input terminal of optical modulation and filtering chip 2. The optical carrier emitted by laser 1 is coupled by first optical coupler 4 and split into two paths, which are respectively input to first phase modulator 5 and second phase modulator 6.

[0050] Specifically, the second phase modulator 6 is used for local oscillator modulation, and the local oscillator modulated optical signal includes a +1st order sideband, an optical carrier, and a -1st order sideband; the first phase modulator 5 is used for radio frequency modulation, and the radio frequency modulated optical signal includes a +1st order sideband, an optical carrier, and a -1st order sideband.

[0051] Specifically, the optical add-drop filter 8 is a high-Q, narrow-bandwidth filter that can be implemented by a micro-ring resonator or a micro-disk resonator. Its through-end e and download-end d filter spectra have complementary characteristics, which can complete the sideband selection function in the optoelectronic oscillator and mixer module.

[0052] Specifically, the through-port e of the optical add-drop filter 8 is a narrowband notch filter. If the +1st order sideband of the local oscillator modulated optical signal is within the stopband of the through-port e of the optical add-drop filter 8, then the optical carrier and the -1st order sideband must be within the passband of the through-port e of the optical add-drop filter 8. Conversely, if the -1st order sideband of the local oscillator modulated optical signal is within the stopband of the through-port e of the optical add-drop filter 8, then the optical carrier and the +1st order sideband must be within the passband of the through-port e of the optical add-drop filter 8, thus achieving phase modulation to intensity modulation conversion. The through-port e of the optical add-drop filter 8 is connected to the optical input terminal of the photodetector 11 to complete photoelectric conversion. The RF output port of the photodetector 11 is connected to the RF input port of the second phase modulator 6 via the microwave amplifier 12, forming a photoelectric oscillator. The local oscillator signal frequency output by the stably oscillating photoelectric oscillator is the optical carrier frequency f. c The center frequency f of the notch filter stopband OF The difference |fc -f OF |

[0053] Specifically, the download end d of the optical add-drop filter 8 is a bandpass filter that is complementary to the through end e. The download end d is exactly the passband at the stopband frequency of the through end e, which can filter out the +1 or -1 sideband of the local oscillator modulated optical signal.

[0054] Specifically, the narrowband flat-top optical filter 7 can be implemented by a cascaded micro-ring resonator, a cascaded micro-disk resonator, or a micro-ring-assisted MZI filter. If the +1st order sideband of the RF modulated optical signal is within the passband of the narrowband flat-top optical filter 7, then the optical carrier and the -1st order sideband must be within the stopband of the narrowband flat-top optical filter 7. Conversely, if the -1st order sideband of the RF modulated optical signal is within the passband of the narrowband flat-top optical filter 7, then the optical carrier and the +1st order sideband must be within the stopband of the narrowband flat-top optical filter 7.

[0055] Specifically, the optical coupler 9 combines the radio frequency modulation optical sideband and the local oscillator modulation optical sideband filtered out by the narrow-band flat-top optical filter 7 and the optical add-drop filter 8. The combined optical signal is then input to the balanced detector 10 and converted into a frequency conversion signal for output.

[0056] Specifically, by adjusting the operating frequency of laser 1, narrowband flat-top optical filter 7, and optical add-drop filter 8, the local oscillator and radio frequency operating frequencies can be tuned and switched between up and down conversion.

[0057] Specifically, the laser 1, the photoelectric detection unit 3, and the microwave amplifier 12 can be packaged modules or chip devices.

[0058] The specific operation of the microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation of the present invention includes the following steps:

[0059] Step 1: The optical carrier output by laser 1 is coupled to the optical input terminal of optical modulation and filtering chip 2, and then split into two paths by the first optical coupler 4 and input to the first phase modulator 5 and the second phase modulator 6 respectively.

[0060] Step two: The optical carrier output from laser 1 is coupled to the second phase modulator 6. The optical signal output from the second phase modulator 6 is filtered by an optical add-drop filter 8. The pass-through port e of the optical add-drop filter 8 is a narrowband notch filter used to achieve phase modulation-intensity modulation conversion. The pass-through port e of the optical add-drop filter 8 is coupled to a photodetector 11 and then connected to a microwave amplifier 12. The output of the microwave amplifier 12 is connected to the RF input port of the second phase modulator 6, forming an opto-oscillator. The relative positions of the operating frequencies of laser 1 and optical add-drop filter 8 are adjusted so that the -1st order sideband of the local oscillator modulated optical signal and the optical carrier are located within the passband of the pass-through port e of the optical add-drop filter 8, and the +1st order sideband of the local oscillator modulated optical signal is located within the stopband of the pass-through port e of the optical add-drop filter 8. The opto-oscillator achieves stable output, and the spectrum output by the second phase modulator 6 is shown below. Figure 2 As shown in (b) above, the spectrum output from the through terminal e of the optical add-drop filter 8 is as follows. Figure 2 As shown in (e), it can be seen that the filtering at the download end d of the optical add-drop filter 8 is complementary to the filtering at the pass-through end e. The download end d of the optical add-drop filter 8 is a bandpass filter that is complementary to the pass-through end e. At this time, the +1st order sideband of the local oscillator modulated optical signal can be filtered out, and the output spectrum is shown in Figure 1. Figure 2 As shown in (d) in the figure.

[0061] Step 3: Apply an RF signal with frequencies f1 to f2 to the RF input port of the first phase modulator 5. The spectrum output by the first phase modulator 5 is shown below. Figure 2 As shown in (a), after filtering by the narrowband flat-top optical filter 7, if the +1st order sideband of the RF modulated optical signal is within the passband of the output terminal c of the narrowband flat-top optical filter 7, then the optical carrier and the -1st order sideband must be within the stopband of the output terminal c of the narrowband flat-top optical filter 7. The RF modulated optical signal spectrum obtained at the output terminal c is as follows. Figure 2 As shown in (c) in the figure.

[0062] Step four: The optical signal output from the download end d of the optical add-drop filter 8 and the optical signal output from the output end c of the narrowband flat-top optical filter 7 are passed through the second optical coupler 9, and the resulting spectrum is as follows: Figure 2 As shown in (f1) and (f2), it can be seen that the output optical signal contains the +1st order sideband of the local oscillator modulated optical signal and the +1st order sideband of the radio frequency modulated optical signal.

[0063] Step 5: The optical signal output from the second optical coupler 9 is coupled into the balanced detector 10, and after photoelectric conversion, a mixed signal is obtained, such as... Figure 2 As shown in (g), the frequency f1-f is obtained. LO ~f2-f LO The intermediate frequency signal.

Claims

1. A microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation, comprising a laser (1), an optical modulation and filtering processing chip (2), a photoelectric detection unit (3), and a microwave amplifier (12), characterized in that: The laser (1) is used to output optical carriers and is connected to an optical modulation and filtering chip (2) and a photoelectric detection unit (3) from left to right. In the optical modulation and filtering chip (2), the input end of the first optical coupler (4) is connected to the laser (1), and the output end of the first optical coupler (4) is divided into two paths. The first output end of the first optical coupler (4) is connected to the optical input end of the first phase modulator (5), and the second output end of the first optical coupler (4) is connected to the optical input end of the second phase modulator (6). The optical output terminal a of the first phase modulator (5) is connected to the input terminal of the narrowband flat-top optical filter (7), and the output terminal c of the narrowband flat-top optical filter (7) is connected to the first input terminal of the second optical coupler (9). The optical output terminal b of the second phase modulator (6) is connected to the input terminal of the optical add-drop filter (8), and the download terminal d of the optical add-drop filter (8) is connected to the second input terminal of the second optical coupler (9). The first phase modulator (5) performs radio frequency modulation, and the radio frequency modulated optical signal includes a +1st order sideband, an optical carrier, and a -1st order sideband; The narrowband flat-top optical filter (7) performs sideband selection on the radio frequency modulated optical signal; The second phase modulator (6) performs local oscillator modulation, and the local oscillator modulated optical signal includes a +1st order sideband, an optical carrier, and a -1st order sideband; The optical add-drop filter (8) performs sideband selection on the local oscillator modulated optical signal; The photoelectric detection unit (3) includes a balanced detector (10). The first output terminal f1 and the second output terminal f2 of the second optical coupler (9) are both connected to the balanced detector (10). The output terminal g of the balanced detector (10) outputs a frequency conversion signal. The photoelectric detection unit (3) further includes a photoelectric detector (11). The through end e of the optical interpolation filter (8) is connected to the photoelectric detector (11). The photoelectric detector (11) is connected to the microwave amplifier (12). The output end of the microwave amplifier (12) is connected to the radio frequency input port of the second phase modulator (6) to form a photoelectric oscillation loop. The filtering spectra of the through end e and the download end d of the optical interpolation filter (8) are complementary. The through end e of the optical interpolation filter (8) is a narrowband notch filter used to filter out the optical signal required to realize the photoelectric oscillation loop. The download end of the optical interpolation filter (8) is a bandpass filter used to filter out one of the sidebands of the local oscillator modulation signal.

2. The microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation as described in claim 1, characterized in that, The optical add-drop filter (8) is a high-Q, narrow-bandwidth filter, and the optical add-drop filter (8) is implemented by a micro-ring resonator or a micro-disk resonator.

3. The microwave photonic mixer based on optical add-drop filtering and photoelectric oscillation as described in claim 1, characterized in that, The narrowband flat-top optical filter (7) is implemented by a cascaded micro-ring resonator, a cascaded micro-disk resonator, or a micro-ring-assisted MZI filter.

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