Frequency-shift-free microwave photon channelized receiving device

Abstract

The invention belongs to the technical field of optical communication, and relates to a frequency-shift-free microwave photon channelized receiving device, which comprises a carrier optical frequency comb generation unit, a local oscillation optical frequency comb generation unit, an electro-optical modulation unit, an optical phase shift unit, a channel selection and spectrum processing unit and a plurality of photoelectric conversion units. A received broadband radio frequency signal is modulated on each comb tooth of the carrier wave optical frequency comb through the electro-optical modulation unit, and based on a vernier effect caused by different free spectral ranges of the carrier wave optical frequency comb and the local oscillator optical frequency comb and inherent frequency alignment of the same pumping laser, frequency alignment of the optical local oscillator and a required receiving sub-channel can be realized. And mirror image sub-channel suppression is realized based on opposite light phase shifts on two sides of the pump light. According to the invention, the structure is simple, a frequency shift and a special modulation structure required by frequency alignment are omitted, the problem of inter-channel crosstalk in a channelization receiving process is effectively suppressed, and the channelization number can be flexibly increased according to actual demands.

Description

Technical Field

[0001] The present invention relates to the technical field of optical communications, and in particular to a non-frequency-shifted microwave photon channelized receiving device. Background Art

[0002] With the rapid development of wireless communication technology, the massive access of communication devices and the continuous increase in terminal communication speeds have posed severe challenges to existing communication systems. To ensure communication quality, RF systems urgently need to overcome the bottleneck of increasingly scarce spectrum resources and evolve towards high frequency bands and large bandwidths. Although the microwave mixing technology of traditional superheterodyne detection can downconvert high-frequency signals to the intermediate frequency band, when the signal bandwidth is greater than the intermediate frequency sampling bandwidth, the analog-to-digital converter will not be able to fully sample the intermediate frequency signal, resulting in signal distortion. Therefore, it is urgent to explore new signal reception systems to overcome the dual bottlenecks of scarce spectrum resources and limited sampling bandwidth and achieve lossless reception of high-frequency, large-bandwidth signals.

[0003] Among various technical solutions for achieving wide-bandwidth signal reception, microwave photonic channelized reception technology, with its advantages of large bandwidth, low transmission loss, and resistance to electromagnetic interference, has become an effective solution. Currently, channelized reception technologies based on arrayed optical filtering, optical frequency combs, periodic optical filtering, and coherent optical frequency combs are being widely researched to meet the demand for wide-bandwidth signal reception. However, in practical applications, these existing technologies generally suffer from complex system structures and poor scalability, urgently requiring technological innovation and breakthroughs. Summary of the Invention

[0004] In order to solve the problems of complex system structure and poor scalability of microwave photon channelized receiving technology mentioned in the background technology, the present invention provides a frequency-shift-free microwave photon channelized receiving device, which aims to achieve highly integrated microwave photon channelized reception of large-bandwidth signals.

[0005] The present invention adopts the following technical solution: the present invention provides a frequency-shift-free microwave photon channelized receiving device, the device comprising a carrier optical frequency comb generating unit, a local oscillator optical frequency comb generating unit, an electro-optical modulation unit, an optical phase shifting unit, a channel selection and spectrum processing unit, and a plurality of photoelectric conversion units; the carrier optical frequency comb generating unit is connected to the input port of the electro-optical modulation unit, the local oscillator optical frequency comb generating unit is connected to the input port of the optical phase shifting unit; the output port of the electro-optical modulation unit is connected to the first input port of the channel selection and spectrum processing unit, the output port of the optical phase shifting unit is connected to the second input port of the channel selection and spectrum processing unit; and the output port of the channel selection and spectrum processing unit is connected to the photoelectric conversion unit.

[0006] The frequency-shift-free microwave photon channelized receiving device provided in the embodiment of the present application generates stable optical frequency comb signals through a carrier optical frequency comb generating unit and a local oscillator optical frequency comb generating unit, respectively, and can provide carrier and local oscillator signals for multiple channels at the same time, thereby realizing multi-channel parallel processing. The channel selection and spectrum processing unit performs spectral selection on the modulated carrier optical frequency comb and the phase-shifted local oscillator optical frequency comb, and inputs them into the photoelectric conversion unit. During operation, the entire device does not require frequency shifting of the optical frequency comb. Instead, it utilizes the inherent free spectral range difference between the two coherent optical frequency combs and realizes frequency alignment of the local oscillator light and the sub-channel based on the "vernier effect", thereby simplifying the system structure.

[0007] In some embodiments, the carrier optical frequency comb generation unit is used to generate a carrier optical frequency comb, and the local oscillator optical frequency comb generation unit is used to generate a local oscillator optical frequency comb; the electro-optical modulation unit operates at a minimum bias point, is used to receive a broadband radio frequency signal, and loads the broadband radio frequency signal onto each comb tooth of the carrier optical frequency comb after electro-optical modulation; the optical phase shifter is used to adjust the phase of the local oscillator optical frequency comb; the channel selection and spectrum processing unit includes multiple output ports, is used to filter and select the carrier optical frequency comb teeth and the corresponding local oscillator optical frequency comb teeth after electro-optical modulation, filter out the negative first-order sideband of the modulation signal on the a-th carrier optical frequency comb tooth on the left side of the pump light and the corresponding local oscillator optical comb tooth, and input them into the input port of the photoelectric conversion unit, filter out the positive first-order sideband of the modulation signal on the a-th carrier optical frequency comb tooth on the right side of the pump light and the corresponding local oscillator optical comb tooth, and input them into another input port of the photoelectric conversion unit; the photoelectric conversion unit is used to down-convert the received optical signal to an intermediate frequency signal for output.

[0008] In some embodiments, the photoelectric conversion unit includes a first photodetector, a second photodetector, a 90° bridge, and a bandpass filter; the negative first-order sideband of the modulation signal on the ath carrier optical frequency comb tooth on the left side of the pump light and the corresponding local oscillator optical comb tooth are connected to the first photodetector, and the positive first-order sideband of the modulation signal on the ath carrier optical frequency comb tooth on the right side of the pump light and the corresponding local oscillator optical comb tooth are connected to the second photodetector, the first photodetector and the second photodetector are respectively connected to the two input ports of the 90° bridge, and the output port of the 90° bridge is connected to the input port of the bandpass filter.

[0009] In some embodiments, the free spectral range of the carrier optical frequency comb is FSR OC .

[0010] In some embodiments, the free spectral range of the local oscillator frequency comb is FSR LO .

[0011] In some embodiments, the carrier optical frequency comb generating unit and the local oscillator optical frequency comb generating unit are pumped by the same seed laser, and the carrier optical frequency comb and the local oscillator optical frequency comb are coherent.

[0012] In some embodiments, the difference between the free spectral ranges of the carrier optical frequency comb and the local oscillator optical frequency comb is equal to the bandwidth of the intermediate frequency sub-signal output by the non-frequency-shifted microwave photon channelized receiving device.

[0013] In some embodiments, the optical phase shifting unit adjusts the phase of the local oscillator optical frequency comb by 45 degrees.

[0014] In some embodiments, the channel selection and spectral processing unit is configured to provide a periodic wavelength division multiplexing filter response, wherein the free spectral range of the periodic filter response is equal to the free spectral range of the carrier optical frequency comb. In some embodiments, the carrier optical frequency comb generation unit is connected to the electro-optical modulation unit via an optical fiber or an integrated optical waveguide; the local oscillator optical frequency comb generation unit is connected to the optical phase shifter via an optical fiber or an integrated optical waveguide; the output port of the electro-optical modulation unit is connected to the channel selection and spectral processing unit via an optical fiber or an integrated optical waveguide; the optical phase shifter is connected to the channel selection and spectral processing unit via an optical fiber or an integrated optical waveguide; and the channel selection and spectral processing unit is connected to the optoelectronic conversion unit via an optical fiber or an integrated optical waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a structural diagram of a non-frequency-shifted microwave photon channelized receiving device provided in an embodiment of the present application; Figure 2 Schematic diagram of the frequency relationship between the comb teeth on both sides of the carrier optical frequency comb and the local oscillator optical frequency comb pump light provided in an embodiment of the present application; Figure 3 This is a schematic diagram of the relative frequency relationship between the 11th to 16th groups of comb teeth on the right side of the pump light after modulating a broadband signal provided by an embodiment of the present application; Figure 4 This is a schematic diagram of the relative frequency relationship of the 11th to 16th groups of comb teeth on the left side of the pump light after modulating a broadband signal provided by an embodiment of the present application.

[0016] Figure numerals: 1. Carrier optical frequency comb generation unit; 2. Local oscillator optical frequency comb generation unit; 3. Electro-optical modulation unit; 4. Optical phase shift unit; 5. Channel selection and spectrum processing unit; 6. Photoelectric conversion unit; 61. First photodetector; 62. Second photodetector; 63. 90° bridge; 64. Bandpass filter. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0018] The embodiment of the present application provides a non-frequency shifted microwave photon channelized receiving device, for example, Figure 1 As shown, it includes a carrier optical frequency comb generating unit 1, a local oscillator optical frequency comb generating unit 2, an electro-optical modulation unit 3, an optical phase shifting unit 4, a channel selection and spectrum processing unit 5 and a plurality of photoelectric conversion units 6.

[0019] The carrier optical frequency comb generation unit 1 is connected to the input port of the electro-optical modulation unit 3, and the local oscillator optical frequency comb generation unit 2 is connected to the input port of the optical phase shifter 4. The output port of the electro-optical modulation unit 3 is connected to the first input port of the channel selection and spectral processing unit 5, and the output port of the optical phase shifter 4 is connected to the second input port of the channel selection and spectral processing unit 5. The output port of the channel selection and spectral processing unit 5 is connected to the input port of the photoelectric conversion unit 6. More specifically, the channel selection and spectral processing unit 5 includes multiple output ports, which are connected to multiple photoelectric conversion units 6 through the multiple output ports. In the channel selection and spectral processing unit 5, each two output ports are connected to the two input ports of one photoelectric conversion unit 6.

[0020] The carrier optical frequency comb generation unit 1 is used to generate the carrier optical frequency comb. The local oscillator optical frequency comb generation unit 2 is used to generate the local oscillator optical frequency comb. The electro-optical modulation unit 3 operates at the minimum bias point and is used to receive a broadband RF signal and load the broadband RF signal onto each comb tooth of the carrier optical frequency comb after electro-optical modulation. The optical phase shifter 4 is used to adjust the phase of the local oscillator optical frequency comb. It is used to filter and select the carrier optical frequency comb teeth and the corresponding local oscillator optical frequency comb teeth after electro-optical modulation, filter out the negative first-order sideband of the modulation signal on the a-th carrier optical frequency comb tooth on the left side of the pump light and the corresponding local oscillator optical comb tooth, and input them into the input port of the photoelectric conversion unit; filter out the positive first-order sideband of the modulation signal on the a-th carrier optical frequency comb tooth on the right side of the pump light and the corresponding local oscillator optical comb tooth, and input them into the other input port of the photoelectric conversion unit. The photoelectric conversion unit 6 is used to down-convert the received optical signal to an intermediate frequency signal for output.

[0021] In some embodiments, the photoelectric conversion unit 6 includes a first photodetector 61, a second photodetector 62, a 90° bridge 63, and a bandpass filter 64. The negative first-order sideband of the modulation signal on the ath carrier optical frequency comb tooth on the left side of the pump light and the corresponding local oscillator optical comb tooth are connected to the first photodetector, and the positive first-order sideband of the modulation signal on the ath carrier optical frequency comb tooth on the right side of the pump light and the corresponding local oscillator optical comb tooth are connected to the second photodetector. The first photodetector and the second photodetector are respectively connected to the two input ports of the 90° bridge, and the output port of the 90° bridge is connected to the input port of the bandpass filter.

[0022] This invention utilizes local oscillator (LO) optical phase shifting to construct an image interference suppression structure. Phase shifting the LO optical frequency comb is based on the "high frequency minus low frequency" principle during the beat process. The right-hand comb teeth of the pump light correspond to "signal minus LO, LO minus image," while the left-hand comb teeth of the pump light correspond to "image minus LO, LO minus signal." The useful signal subchannel and the image interference subchannel each receive opposite phase shifts. Mirror subchannels are then combined through a 90° bridge to achieve image subchannel suppression. When faced with multi-channel synchronous output, a channel selection and spectral processing unit with multi-channel filtering characteristics selects the corresponding signal sidebands and optical LOs on either side of the pump light, avoiding the extensive use of 90° optical mixers and reducing system complexity.

[0023] As a possible implementation method, the carrier optical frequency comb generating unit 1 generates a free spectrum range FSR OC The carrier optical frequency comb, the local oscillator optical frequency comb generating unit 2 generates a free spectrum range of FSR LO The electro-optical modulation unit 3 receives a broadband RF signal and implements carrier-suppressed double-sideband modulation of the RF signal on each comb tooth using a DC bias voltage. The optical phase shifter 4 adjusts the phase of the LO optical frequency comb using a DC bias voltage.

[0024] In order to better illustrate the frequency-shift-free microwave photonic channelized receiving device provided in the embodiment of the present application, the specific implementation process is described by taking the Ku-band broadband signal channelized reception with a center frequency of 15 GHz and a bandwidth of 6 GHz as an example.

[0025] For example, the free spectral ranges of the carrier optical frequency comb unit 1 and the local oscillator optical frequency comb unit 2 generated by the same seed laser pumping are 49 GHz and 50 GHz, respectively. Figure 2 The frequency relationship between the carrier optical frequency comb and the local oscillator optical frequency comb pump light on both sides is shown.

[0026] from Figure 2 It can be seen that due to the different free spectral ranges of the carrier frequency comb and the local oscillator frequency comb, the frequency difference between the corresponding comb teeth of the carrier frequency comb and the local oscillator frequency comb gradually increases with the increase in the number of comb teeth. The frequency difference of the nth comb tooth on the left or right side of the pump light can be expressed as: In this embodiment, the free spectrum difference between the signal optical frequency comb and the local oscillator optical frequency comb is 1 GHz, so the frequency difference between the nth comb teeth is n GHz. After modulating the RF signal on the carrier optical frequency comb, as the number of comb teeth increases, each optical local oscillator on the local oscillator optical frequency comb will be aligned with different positions of the modulated signal in 1 GHz steps. In other words, this embodiment can achieve channelized down-conversion reception of broadband signals with a 1 GHz subchannel bandwidth.

[0027] For example, Figure 3 The figure shows the relative frequency relationship of the 11th to 16th comb teeth on the right side of the pump light after RF signal modulation. It can be seen that the 11th comb teeth are filtered out by the channel selection and spectral processing unit and output to the optoelectronic conversion unit for down-conversion. The down-converted signal has a bandwidth of 1-7 GHz. It then passes through an RF bandpass filter with a center frequency of 1.5 GHz and a bandwidth of 1 GHz to obtain the down-converted signal of the first subchannel (CH1). Similarly, the 12th comb teeth are input into the photodetector to obtain a down-converted signal with a bandwidth of 0-6 GHz. Passing through the same bandpass filter, the down-converted signal of the second subchannel (CH2) is obtained. This process continues in this way, achieving channelized down-conversion output with the same intermediate frequency for all subchannels.

[0028] from Figure 3 It can be seen that in the 14th, 15th and 16th groups of comb teeth, the local oscillator light is respectively aligned with the middle position of the second and third channels, the middle position of the third and fourth channels, and the middle position of the fourth and fifth channels, forming two sets of frequency components that are mirror images of each other. After the down-conversion in the optoelectronic conversion unit, the down-conversion signal of the first channel causes in-band interference to the required down-conversion signal of the fourth channel, the down-conversion signal of the second channel causes in-band interference to the required down-conversion signal of the fifth channel, and the down-conversion signal of the third channel causes in-band interference to the required down-conversion signal of the sixth channel. The present application adopts an image frequency suppression measure based on optical phase shifting to suppress inter-channel crosstalk in channelized down-conversion.

[0029] Specifically, the present invention implements a 45° phase shift on the local oscillator optical frequency comb. Based on the principle of "high frequency minus low frequency" in the beat process, if the fourth channel obtains a +45° phase shift during downconversion in the 14th set of comb teeth, then the first channel will obtain a -45° phase shift, resulting in a 90° phase difference between the downconverted signals of the two mirror-image sub-channels.

[0030] For example, in Figure 4 In the 11th to 16th comb teeth on the left side of the pump light, the downconversion process is opposite to that on the right. In the 14th comb tooth, the first channel receives a +45° phase shift, while the fourth channel receives a -45° phase shift, again with a 90° phase difference between the two channels. This means that the downconverted signals of the same channel on the left and right sides of the pump light are in phase quadrature. By combining them with a 90° bridge, the image interference sub-channels interfere in opposite phases, while the useful signal sub-channels interfere constructively in phase. Similarly, the inter-channel crosstalk in the fifth and sixth channels can be suppressed by controlling the phase of the 15th and 16th comb teeth on the left and right sides of the pump light.

[0031] It can be seen from the above embodiments that the frequency-shift-free microwave photonic channelized receiving device provided in the present application achieves good broadband signal channelized down-conversion output, suppresses interference from mirror channels, and solves the inter-channel crosstalk problem existing in channelized reception.

[0032] The above content is a further detailed description of the present invention in conjunction with the preferred technical solution, and the specific implementation of the invention cannot be limited to these descriptions. For those skilled in the art of the present invention, simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered within the scope of protection of the present invention.

Claims

1. A microwave photon channelized receiving device without frequency shifting, characterized in that: include: A carrier optical frequency comb generation unit, a local oscillator optical frequency comb generation unit, an electro-optical modulation unit, an optical phase shift unit, a channel selection and spectrum processing unit, and multiple photoelectric conversion units; The carrier optical frequency comb generating unit is connected to the input port of the electro-optical modulation unit, and the local oscillator optical frequency comb generating unit is connected to the input port of the optical phase shifting unit; The output port of the electro-optical modulation unit is connected to the first input port of the channel selection and spectrum processing unit, the output port of the optical phase shift unit is connected to the second input port of the channel selection and spectrum processing unit; the output port of the channel selection and spectrum processing unit is connected to the photoelectric conversion unit.

2. The non-frequency-shifted microwave photon channelized receiving device according to claim 1, characterized in that: The carrier optical frequency comb generating unit is used to generate a carrier optical frequency comb, and the local oscillator optical frequency comb generating unit is used to generate a local oscillator optical frequency comb; The electro-optical modulation unit operates at a minimum bias point, is used to receive a broadband radio frequency signal, and load the broadband radio frequency signal onto each comb tooth of the carrier optical frequency comb after electro-optical modulation; The optical phase shifting unit is used to adjust the phase of the local oscillator optical frequency comb; The channel selection and spectrum processing unit includes multiple output ports for filtering and selecting the carrier optical frequency comb teeth and the corresponding local oscillator optical frequency comb teeth after electro-optical modulation, filtering out the negative first-order sideband of the modulation signal on the a-th carrier optical frequency comb tooth on the left side of the pump light and the corresponding local oscillator optical comb tooth, and inputting them into the input port of the photoelectric conversion unit; filtering out the positive first-order sideband of the modulation signal on the a-th carrier optical frequency comb tooth on the right side of the pump light and the corresponding local oscillator optical comb tooth, and inputting them into another input port of the photoelectric conversion unit; The photoelectric conversion unit is used to down-convert the received optical signal into an intermediate frequency signal for output.

3. The non-frequency-shifted microwave photon channelized receiving device according to claim 2, characterized in that: The photoelectric conversion unit includes a first photodetector, a second photodetector, a 90° bridge and a bandpass filter; The negative first-order sideband of the modulation signal on the ath carrier optical frequency comb tooth on the left side of the pump light and the corresponding local oscillator optical comb tooth are connected to the first photodetector, and the positive first-order sideband of the modulation signal on the ath carrier optical frequency comb tooth on the right side of the pump light and the corresponding local oscillator optical comb tooth are connected to the second photodetector. The first photodetector and the second photodetector are respectively connected to the two input ports of the 90° bridge, and the output port of the 90° bridge is connected to the input port of the bandpass filter.

4. The non-frequency-shifted microwave photon channelized receiving device according to claim 1, characterized in that: The free spectral range of the carrier optical frequency comb is FSR OC .

5. The non-frequency-shifted microwave photon channelized receiving device according to claim 4, characterized in that: The free spectral range of the local oscillator frequency comb is FSR LO .

6. The non-frequency-shifted microwave photon channelized receiving device according to claim 5, characterized in that: The carrier optical frequency comb generating unit and the local oscillator optical frequency comb generating unit are pumped by the same seed laser, and the carrier optical frequency comb and the local oscillator optical frequency comb are coherent.

7. The non-frequency-shifted microwave photon channelized receiving device according to claim 5, characterized in that: The difference between the free spectral ranges of the carrier optical frequency comb and the local oscillator optical frequency comb is equal to the bandwidth of the intermediate frequency sub-signal output by the non-frequency-shifted microwave photon channelized receiving device.

8. The non-frequency-shifted microwave photon channelized receiving device according to claim 1, characterized in that: The optical phase shifting unit adjusts the phase of the local oscillator optical frequency comb by 45 degrees.

9. The non-frequency-shifted microwave photon channelized receiving device according to claim 1, characterized in that: The channel selection and spectrum processing unit is configured to provide a periodic wavelength division multiplexing filter response, wherein a free spectral range of the periodic filter response is equal to a free spectral range of the carrier optical frequency comb.

10. The non-frequency-shifted microwave photon channelized receiving device according to claim 1, characterized in that: The carrier optical frequency comb generating unit and the electro-optical modulation unit are connected via an optical fiber or an integrated optical waveguide; The local oscillator optical frequency comb generating unit and the optical phase shifting unit are connected via an optical fiber or an integrated optical waveguide; The output port of the electro-optical modulation unit is connected to the channel selection and spectrum processing unit via an optical fiber or an integrated optical waveguide; The optical phase shift unit is connected to the channel selection and spectrum processing unit via an optical fiber or an integrated optical waveguide; The channel selection and spectrum processing unit is connected to the photoelectric conversion unit via an optical fiber or an integrated optical waveguide.

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