A frequency-shift-free microwave photonic channelization receiver

Abstract

The application belongs to the technical field of optical communication and relates to a frequency-shift-free microwave photonic channelized receiving device, which comprises a carrier light frequency comb generating unit, a local light frequency comb generating 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. The received broadband radio frequency signal is modulated on each comb tooth of the carrier light frequency comb through the electro-optical modulation unit, and the frequency alignment between the optical local oscillator and the required receiving sub-channel can be realized based on the "vernier" effect caused by the different free spectral ranges of the carrier light frequency comb and the local light frequency comb and the inherent frequency alignment of the same pump laser. The mirror image sub-channel suppression is realized based on the opposite optical phase shifts on both sides of the pump light. The application has a simple structure, omits the frequency shift and special modulation structure required for frequency alignment, effectively suppresses the inter-channel crosstalk problem in the channelized receiving process, and can flexibly increase the channelization quantity according to actual needs.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical communication technology, and particularly relates to a frequency-shift-free microwave photonic channelized receiving device. BACKGROUND

[0002] With the vigorous development of wireless communication technology, the massive access of communication equipment and the continuous rise of terminal communication rate pose a severe challenge to the existing communication system. In order to guarantee the communication quality, the radio frequency system needs to break through the bottleneck of the increasingly scarce spectrum resources and evolve towards high frequency and large bandwidth. Although the microwave mixing technology of traditional superheterodyne detection can down-convert the high frequency signal to the intermediate frequency band, when the signal bandwidth is greater than the sampling bandwidth of the intermediate frequency, the analog-to-digital converter cannot sample the intermediate frequency signal completely, resulting in signal distortion. Therefore, it is urgent to explore a new signal receiving system to break through the dual bottleneck of spectrum resource shortage and limited sampling bandwidth and realize the lossless reception of high frequency and large bandwidth signals.

[0003] Among various technical solutions for realizing large bandwidth signal reception, the microwave photonic channelized receiving technology has become an effective solution due to its advantages of large bandwidth, low transmission loss and anti-electromagnetic interference. At present, the channelized receiving technology based on arrayed optical filtering, optical frequency comb and periodic optical filtering and coherent optical frequency comb is widely studied to meet the demand for large bandwidth signal reception. However, in actual application, these existing technologies have problems such as complex system structure and poor scalability, which need to be technically innovated and broken through. SUMMARY

[0004] To solve the problems of complex system structure and poor scalability of the microwave photonic channelized receiving technology mentioned in the background art, the present application provides a frequency-shift-free microwave photonic channelized receiving device, which aims to realize high-integration microwave photonic channelization reception for large bandwidth signals.

[0005] The present application adopts the following technical solution: the present application provides a frequency-shift-free microwave photonic channelized receiving device, which comprises a carrier optical frequency comb generating unit, a local oscillator optical frequency comb generating unit, an electro-optical modulation unit, an optical phase shift unit, a channel selection and optical spectrum processing unit and a plurality of photoelectric conversion units; the input port of the carrier optical frequency comb generating unit is connected with the electro-optical modulation unit, and the input port of the local oscillator optical frequency comb generating unit is connected with the optical phase shift unit; the output port of the electro-optical modulation unit is connected with the first input port of the channel selection and optical spectrum processing unit, and the output port of the optical phase shift unit is connected with the second input port of the channel selection and optical spectrum processing unit; the output port of the channel selection and optical spectrum processing unit is connected with the photoelectric conversion unit. The free spectral range of the carrier optical frequency comb is FSR OC The free spectral range of the local oscillator optical frequency comb is FSR LOThe carrier optical frequency comb generating unit and the local oscillator optical frequency comb generating unit are pumped by the same sub-laser, and the carrier optical frequency comb and the local oscillator optical frequency comb are coherent. The difference between the free spectral range of the carrier optical frequency comb and the free spectral range of the local oscillator optical frequency comb is equal to the bandwidth of the intermediate frequency sub-signal output by the frequency-shift-free microwave photonic channelized receiving device.

[0006] The frequency-shift-free microwave photonic channelized receiving device provided by the embodiment of the present application generates stable optical frequency comb signals by the carrier optical frequency comb generating unit and the local oscillator optical frequency comb generating unit, can simultaneously provide carrier signals and local oscillator signals for multiple channels, and realizes multi-channel parallel processing. The channel selection and spectrum processing unit performs spectrum selection on the modulated carrier optical frequency comb and the phase-shifted local oscillator optical frequency comb, and inputs the optical-electric conversion unit. The entire device does not need to perform frequency shift operation on the optical frequency comb in the operation process, utilizes the inherent difference between the free spectral range of the two coherent optical frequency combs, and realizes the frequency alignment of the local oscillator and the sub-channel based on the vernier effect, thereby simplifying the system structure.

[0007] In some embodiments, the carrier optical frequency comb generating unit is configured to generate a carrier optical frequency comb, the local oscillator optical frequency comb generating unit is configured to generate a local oscillator optical frequency comb, the electro-optical modulation unit is configured to work at a minimum bias point, and is configured to receive a wideband radio frequency signal and load the wideband radio frequency signal onto each tooth of the carrier optical frequency comb after electro-optical modulation, the optical phase shift unit is configured to adjust the phase of the local oscillator optical frequency comb, and the channel selection and spectrum processing unit includes multiple output ports, is configured to filter and select the modulated signal of the negative first-order sideband of the a-th tooth of the carrier optical frequency comb on the left of the pump light and the corresponding local oscillator tooth, and is configured to filter out the modulated signal of the positive first-order sideband of the a-th tooth of the carrier optical frequency comb on the right of the pump light and the corresponding local oscillator tooth, and input the modulated signal into the input port of the optical-electric conversion unit.

[0008] In some embodiments, the optical-electric conversion unit includes a first photoelectric detector, a second photoelectric detector, a 90° bridge, and a band-pass filter, the modulated signal of the negative first-order sideband of the a-th tooth of the carrier optical frequency comb on the left of the pump light and the corresponding local oscillator tooth are connected to the first photoelectric detector, the modulated signal of the positive first-order sideband of the a-th tooth of the carrier optical frequency comb on the right of the pump light and the corresponding local oscillator tooth are connected to the second photoelectric detector, the first photoelectric detector and the second photoelectric detector 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 band-pass filter.

[0009] In some embodiments, the optical phase shift unit adjusts the phase of the local oscillator optical frequency comb by 45°.

[0010] In some embodiments, the channel selection and spectral processing unit is configured to provide a periodic wavelength division multiplexing filter response, a free spectral range of the periodic wavelength division multiplexing filter response being equal to a free spectral range of the carrier optical frequency comb. In some embodiments, the connection between the local optical frequency comb generation unit and the optical phase shifting unit is through an optical fiber or an integrated optical waveguide; the connection between the output port of the electro-optical modulation unit and the channel selection and spectral processing unit is through an optical fiber or an integrated optical waveguide; the connection between the optical phase shifting unit and the channel selection and spectral processing unit is through an optical fiber or an integrated optical waveguide; the connection between the channel selection and spectral processing unit and the photoelectric conversion unit is through an optical fiber or an integrated optical waveguide. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a structural schematic diagram of a frequency shift-free microwave photonic channelized receiver device provided by an embodiment of the present application;

[0012] Figure 2 is a schematic diagram of the frequency relationship between the two sides of the pump light comb teeth of the carrier optical frequency comb and the local optical frequency comb provided by an embodiment of the present application;

[0013] Figure 3 is a schematic diagram of the relative frequency relationship of the right side 11th to 16th group of comb teeth of the pump light after modulating the wideband signal provided by an embodiment of the present application;

[0014] Figure 4 is a schematic diagram of the relative frequency relationship of the left side 11th to 16th group of comb teeth of the pump light after modulating the wideband signal provided by an embodiment of the present application.

[0015] The reference signs are as follows: 1, carrier optical frequency comb generation unit; 2, local optical frequency comb generation unit; 3, electro-optical modulation unit; 4, optical phase shifting unit; 5, channel selection and spectral processing unit; 6, photoelectric conversion unit; 61, first photoelectric detector; 62, second photoelectric detector; 63, 90° electrical bridge; 64, band-pass filter. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0017] The present application provides a frequency shift-free microwave photonic channelized receiver device, for example, Figure 1As shown, the device 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.

[0018] The carrier optical frequency comb generating unit 1 is connected with an input port of the electro-optical modulation unit 3, and the local oscillator optical frequency comb generating unit 2 is connected with an input port of the optical phase shifting unit 4. An output port of the electro-optical modulation unit 3 is connected with a first input port of the channel selection and spectrum processing unit 5, and an output port of the optical phase shifting unit 4 is connected with a second input port of the channel selection and spectrum processing unit 5. An output port of the channel selection and spectrum processing unit 5 is connected with an input port of the photoelectric conversion unit 6. More specifically, the channel selection and spectrum processing unit 5 includes a plurality of output ports, and is connected with the plurality of photoelectric conversion units 6 through the plurality of output ports. In the channel selection and spectrum processing unit 5, each two output ports are connected with two input ports of one photoelectric conversion unit 6.

[0019] The carrier optical frequency comb generating unit 1 is configured to generate a carrier optical frequency comb. The local oscillator optical frequency comb generating unit 2 is configured to generate a local oscillator optical frequency comb. The electro-optical modulation unit 3 is configured to operate at a minimum bias point, and is configured to receive a wideband radio frequency signal and load the wideband radio frequency signal onto each tooth of the carrier optical frequency comb after electro-optical modulation. The optical phase shifting unit 4 is configured to adjust a phase of the local oscillator optical frequency comb. The channel selection and spectrum processing unit 5 is configured to filter and select the modulated signal of the left a-th tooth of the carrier optical frequency comb and the corresponding local oscillator optical comb tooth, and input the negative first-order sideband of the modulated signal into an input port of the photoelectric conversion unit. The channel selection and spectrum processing unit 5 is also configured to filter and select the positive first-order sideband of the modulated signal of the right a-th tooth of the carrier optical frequency comb and the corresponding local oscillator optical comb tooth, and input the positive first-order sideband of the modulated signal into another input port of the photoelectric conversion unit. The photoelectric conversion unit 6 is configured to down-convert the received optical signal to an intermediate frequency signal and output the intermediate frequency signal.

[0020] In some embodiments, the photoelectric conversion unit 6 includes a first photoelectric detector 61, a second photoelectric detector 62, a 90° bridge 63, and a band-pass filter 64. The negative first-order sideband of the modulated signal of the left a-th tooth of the carrier optical frequency comb and the corresponding local oscillator optical comb tooth are connected with the first photoelectric detector, and the positive first-order sideband of the modulated signal of the right a-th tooth of the carrier optical frequency comb and the corresponding local oscillator optical comb tooth are connected with the second photoelectric detector. The first photoelectric detector and the second photoelectric detector are respectively connected with two input ports of the 90° bridge, and an output port of the 90° bridge is connected with an input port of the band-pass filter.

[0021] The application is based on the way of realizing the local oscillator light phase shift to construct the mirror frequency interference suppression structure, the local oscillator light frequency comb is phase shifted, and based on the frequency high minus frequency low in the beat frequency process, that is, the right comb tooth of the pump light is signal minus local oscillator, and the left comb tooth of the pump light is mirror frequency minus local oscillator, the useful signal subchannel and the mirror frequency interference subchannel obtain opposite phase shifts respectively, and then through the 90° bridge, the mirror image subchannel suppression can be realized. When facing the multi-channel synchronous output, the corresponding signal sideband and the optical local oscillator on both sides of the pump light are selected through the channel selection and spectrum processing unit with multi-channel filtering characteristics, the use of a large number of 90° optical mixers is avoided, and the complexity of the system is reduced.

[0022] As a possible implementation, the carrier light frequency comb generating unit 1 generates a carrier light frequency comb with a free spectral range FSR OC , and the local oscillator light frequency comb generating unit 2 generates a local oscillator light frequency comb with a free spectral range FSR LO . The electro-optical modulation unit 3 receives a wideband radio frequency signal and realizes carrier suppressed double sideband modulation of the radio frequency signal on each comb tooth through a direct current bias voltage. The optical phase shift unit 4 adjusts the phase of the local oscillator light frequency comb through a direct current bias voltage.

[0023] In order to better illustrate the non-frequency-shifted microwave photonic channelized receiving device provided by the embodiment of the application, taking the channelized receiving of a Ku-band wideband signal with a center frequency of 15 GHz and a bandwidth of 6 GHz as an example, the specific implementation process is described.

[0024] For example, the carrier light frequency comb unit 1 and the local oscillator light frequency comb unit 2 from the same seed laser pump generate a carrier light frequency comb and a local oscillator light frequency comb with free spectral ranges of 49 GHz and 50 GHz respectively. Figure 2 The frequency relationship between the carrier light frequency comb and the local oscillator light frequency comb on both sides of the pump light comb teeth is shown.

[0025] From Figure 2 It can be seen that, due to the different free spectral ranges of the carrier light frequency comb and the local oscillator light frequency comb, with the increase of the number of comb teeth, the frequency difference between the corresponding comb teeth of the carrier light frequency comb and the local oscillator light frequency comb also gradually increases, and the frequency difference of the nth comb tooth on the left or right side of the pump light can be expressed as:

[0026]

[0027] The free spectral range of the signal light frequency comb and the local light frequency comb in the embodiment is 1 GHz, and the frequency difference between the nth comb tooth is n GHz. After modulating the radio frequency signal on the carrier light frequency comb, with the increase of the number of comb teeth, each local light on the local light frequency comb will be aligned with different positions of the modulated signal with a step of 1 GHz, that is, the embodiment can realize the channelization down-conversion reception of the wideband signal with a subchannel bandwidth of 1 GHz.

[0028] Exemplarily, Figure 3 The relative frequency relationship of the 11th to 16th group of comb teeth on the right side of the pump light after modulating the radio frequency signal is shown, and it can be seen that the 11th group of comb teeth is filtered out by the channel selection and spectrum processing unit and output to the photoelectric conversion unit to complete the down-conversion, and the bandwidth of the down-converted signal covers 1-7 GHz, and a radio frequency band-pass filter with a center frequency of 1.5 GHz and a bandwidth of 1 GHz can obtain the down-converted signal of the first subchannel (CH1). Similarly, the 12th group of comb teeth input to the photoelectric detector obtains a down-converted signal with a bandwidth covering 0-6 GHz, and through the same band-pass filter, the down-converted signal of the second subchannel (CH2) can be obtained. Similarly, the down-converted output of all subchannels with the same intermediate frequency can be realized.

[0029] From Figure 3 It can be seen that in the 14th, 15th and 16th group of comb teeth, the local light respectively aligns with the middle position of the second channel and the third channel, the middle position of the third channel and the fourth channel, and the middle position of the fourth channel and the fifth channel, and respectively forms two groups of mirror image frequency components, so that after down-conversion in the photoelectric conversion unit, the down-converted signal of the first channel causes in-band interference to the required fourth channel down-converted signal, the down-converted signal of the second channel causes in-band interference to the required fifth channel down-converted signal, and the down-converted signal of the third channel causes in-band interference to the required sixth channel down-converted signal. The present application adopts a mirror frequency suppression measure based on optical phase shift to suppress the inter-channel crosstalk in the channelization down-conversion.

[0030] Specifically, the present application implements 45° phase shift on the local light frequency comb, and based on the principle that "frequency high minus frequency low" in the beat frequency process, if the fourth channel down-conversion obtains +45° phase shift in the 14th group of comb teeth, then the first channel will obtain-45° phase shift, so that the down-converted signals of the two mirror image subchannels have a phase difference of 90°.

[0031] Exemplarily, in Figure 4In the 11th to 16th groups of comb teeth on the left side of the pump light, the down-conversion process is opposite to that of the right side comb teeth. In the 14th group of comb teeth, the first channel obtains a phase shift of +45°, and the fourth channel obtains a phase shift of -45°, and the two channels have a phase difference of 90°. That is, the down-converted signals of the same channel on the left and right sides of the pump light are in phase quadrature with each other. Through a 90° bridge, the mirror frequency interference sub-channels are in opposite phase interference and the useful signal sub-channels are in the same phase interference. Similarly, for the inter-channel crosstalk of the fifth channel and the sixth channel, the suppression can be realized by phase control of the 15th group and the 16th group of comb teeth on the left and right sides of the pump light.

[0032] As can be seen from the above embodiments, the non-frequency-shifted microwave photon channelization receiving device provided by the application realizes good wideband signal channelization down-conversion output, suppresses the interference of the mirror channel, and solves the inter-channel crosstalk problem existing in the channelization receiving.

[0033] The above is a further detailed description of the application in combination with the preferred technical solutions, and cannot be regarded as a limitation on the specific implementation of the application. For those skilled in the art to which the application belongs, without departing from the concept of the application, simple deductions and substitutions can also be made, which should be regarded as the protection scope of the application.

Claims

1. A frequency-agile microwave photonic channelization receiver apparatus, characterized by, The application relates to a carrier light frequency comb generating unit, a local light 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 light frequency comb generating unit is connected with an input port of the electro-optical modulation unit, and the local light frequency comb generating unit is connected with an input port of the optical phase shifting unit. An output port of the electro-optical modulation unit is connected with a first input port of the channel selection and spectrum processing unit, and an output port of the optical phase shifting unit is connected with a second input port of the channel selection and spectrum processing unit. The carrier light frequency comb generating unit is used for generating a carrier light frequency comb, and the local light frequency comb generating unit is used for generating a local light frequency comb. A free spectral range of the carrier optical frequency comb is FSR OC A free spectral range of the local optical frequency comb is FSR LO The carrier optical frequency comb generating unit and the local optical frequency comb generating unit are pumped by the same kind of sub-laser, the carrier optical frequency comb and the local optical frequency comb are coherent, and a difference between the free spectral ranges of the carrier optical frequency comb and the local optical frequency comb is equal to a bandwidth of the intermediate frequency sub-signal output by the frequency shift-free microwave photonic channelized receiving device. The electro-optical modulation unit works at a minimum bias point and is used for receiving a wideband radio frequency signal and loading the wideband radio frequency signal onto each tooth of the carrier light frequency comb after electro-optical modulation. The optical phase shifting unit is used for adjusting the phase of the local light frequency comb. The channel selection and spectrum processing unit comprises a plurality of output ports and is used for filtering and selecting the carrier light frequency comb tooth and the corresponding local light frequency comb tooth after electro-optical modulation, filtering out the negative first-order sideband of the modulation signal on the left a-th carrier light frequency comb tooth of the pump light and the corresponding local light comb tooth and inputting the negative first-order sideband into an input port of the photoelectric conversion unit, and filtering out the positive first-order sideband of the modulation signal on the right a-th carrier light frequency comb tooth of the pump light and the corresponding local light comb tooth and inputting the positive first-order sideband into another input port of the photoelectric conversion unit. The photoelectric conversion unit is used for down-converting the received optical signal into an intermediate frequency signal output. The photoelectric conversion unit comprises a first photoelectric detector, a second photoelectric detector, a 90-degree bridge and a band-pass filter. The negative first-order sideband of the modulation signal on the left a-th carrier light frequency comb tooth of the pump light and the corresponding local light comb tooth are connected with the first photoelectric detector, the positive first-order sideband of the modulation signal on the right a-th carrier light frequency comb tooth of the pump light and the corresponding local light comb tooth are connected with the second photoelectric detector, the first photoelectric detector and the second photoelectric detector are respectively connected with two input ports of the 90-degree bridge, and an output port of the 90-degree bridge is connected with an input port of the band-pass filter. The optical phase shifting unit adjusts the phase of the local light frequency comb by 45 degrees.

2. The frequency-agile microwave photonic channelization receiver of claim 1, wherein, The channel selection and spectrum processing unit is configured to provide a periodic wavelength division multiplexing filter response, and a free spectral range of the periodic wavelength division multiplexing filter response is equal to a free spectral range of the carrier light frequency comb.

3. The frequency-agile microwave photonic channelization receiver of claim 1, wherein, The carrier light frequency comb generating unit and the electro-optical modulation unit are connected through an optical fiber or an integrated optical waveguide.

4. The frequency-agile microwave photonic channelization receiver of claim 1, wherein, The local light frequency comb generating unit and the optical phase shifting unit are connected through an optical fiber or an integrated optical waveguide. The output port of the electro-optical modulation unit and the channel selection and spectrum processing unit are connected through an optical fiber or an integrated optical waveguide. The optical phase shifting unit and the channel selection and spectrum processing unit are connected through an optical fiber or an integrated optical waveguide. ​ The channel selection and spectral processing unit is connected to the opto-electric conversion unit by optical fibers or integrated optical waveguides.

Images