Communication device and radio frequency over fiber transmission system

Abstract

According to the communication device and the radio-over-fiber transmission system, an electro-optical modulation module is used for modulating an RF signal to multiple optical signals, the multiple optical signals obtained after modulation are transmitted in an optical fiber, and finally the RF signal modulated on the multiple optical signals is demodulated at the output end of optical fiber transmission through an electro-optical demodulation module. Therefore, the spectrum of the incident optical signal is broadened, the energy density of the incident optical signal is reduced, the power of the optical signal incident to the optical fiber is improved, and the performance and the transmission efficiency of a radio over fiber transmission system are improved.

Description

Communication device and radio frequency transmission system over light Technical Field

[0001] The present application relates to the field of communications, and more specifically, to a communication device and an optical radio frequency transmission system. Background Art

[0002] In recent years, to accommodate the ever-increasing transmission capacity of communications networks and meet the demands for network interactivity and flexibility, traditional communications networks have gradually evolved toward hybrid optical and electrical networks. Radio over fiber (RoF), a candidate for the next generation of low-cost broadband wireless access, modulates radio frequency (RF) signals onto an optical carrier, fully utilizing the fiber's bandwidth to transmit RF signals. RoF technology meets the demands for increased network transmission capacity, interactivity, and flexibility.

[0003] However, most current RoF transmission systems use ordinary G.652E optical fiber for signal transmission. When high-power optical signals are input into the fiber, they are easily affected by stimulated Brillouin scattering (SBS). This causes the optical signal power incident on the fiber to be low, resulting in limited optical power transmission through the fiber, which affects the performance and transmission efficiency of the RoF transmission system.

[0004] Summary of the Invention

[0005] The present application provides a communication device and an optical radio frequency transmission system, which achieves the broadening of the incoming optical signal spectrum and reduces the energy density of the incoming fiber light, thereby increasing the optical signal power incident on the optical fiber and improving the performance and transmission efficiency of the RoF transmission system.

[0006] In a first aspect, a light-carrying radio frequency transmission system is provided, which includes: an electro-optical modulation module: the electro-optical modulation module is used to modulate a radio frequency signal onto multiple optical signals to obtain multiple modulated optical signals; an optical fiber: the optical fiber is used to transmit the multiple modulated optical signals; and an optoelectronic demodulation module: the optoelectronic demodulation module is used to demodulate and output the radio frequency signal from the multiple modulated optical signals output by the optical fiber.

[0007] The first aspect provides an optical radio frequency transmission system that uses an electro-optical modulation module to modulate an RF signal onto multiple optical signals, transmits the modulated multiple optical signals through an optical fiber, and finally, uses an optoelectronic demodulation module at the output end of the optical fiber transmission to demodulate the RF signal modulated onto the multiple optical signals. This broadens the spectrum of the incoming optical signal, reduces the energy density of the incoming optical fiber, and thus increases the power of the optical signal incident on the optical fiber, thereby improving the performance and transmission efficiency of the RoF transmission system.

[0008] In one possible implementation of the first aspect, the system further includes: an optical signal generating module configured to generate the multiple optical signals; a radio frequency signal generating module configured to generate the radio frequency signal; and an optical amplifier configured to amplify the power of the multiple modulated optical signals and transmit the power-amplified optical signals to the optical fiber. In this implementation, the power amplification by the optical amplifier can improve the transmission efficiency of the multiple modulated optical signals in the optical fiber.

[0009] In a possible implementation of the first aspect, the wavelengths of the multiple optical signals generated by the optical signal generating module are all different, or the wavelengths of the multiple optical signals generated by the optical signal generating module may be partially the same and partially different.

[0010] In a possible implementation of the first aspect, the system further includes: an optical circulator, a reflected light power detection module, and a feedback control unit, wherein a first port of the optical circulator is connected to the output end of the optical amplifier, a second port of the optical circulator is connected to the input end of the optical fiber, a third port of the optical circulator is connected to the input end of the reflected light power detection module, an output end of the reflected light power detection module is connected to the input end of the feedback control unit, and an output end of the feedback control unit is connected to the optical signal generation module; the reflected light power detection module is configured to: detect the reflected light power of multiple modulated optical signals transmitted in the optical fiber, and when the reflected light power is greater than or equal to a first threshold, send a first signal to the feedback control unit; the feedback control unit is configured to generate a second signal under the action of the first signal and transmit the second signal to the optical signal generation module; the optical signal generation module is configured to adjust the wavelength and / or quantity of the generated multiple optical signals according to the second signal. In this implementation, the flexibility of the RoF transmission system can be improved. When the power of the optical signal incident on the optical fiber is greater than or equal to the preset SBS threshold power, the number and / or wavelength of the optical signal generated by the optical signal generation module are promptly adjusted to ensure that the power of the optical signal incident on the optical fiber is less than the SBS threshold power. This can improve the stability and performance of the RoF transmission system on the basis of increasing the power of the optical signal incident on the optical fiber.

[0011] Exemplarily, the preset threshold (first threshold) may be a preset or predefined SBS threshold power.

[0012] In a possible implementation of the first aspect, the radio frequency signal generation module is used to generate N radio frequency signals, the electro-optical modulation module includes N electro-optical modulation sub-modules, and the optoelectronic demodulation module includes N optoelectronic demodulation sub-modules. The system also includes: a first de-wavelength division multiplexer, a wavelength division multiplexer, and a second de-wavelength division multiplexer; the first de-wavelength division multiplexer is used to decompose the M optical signals generated by the optical signal generation module into N channels, where M is an integer greater than 1, and the i-th channel includes Ki optical signals, i is an integer greater than or equal to 1 and less than or equal to N; the i-th electro-optical modulation submodule is used to modulate the i-th RF signal to the K i On the optical signal, we get K i modulated optical signals, N electro-optical modulation submodules output Q modulated optical signals, Q is an integer greater than or equal to 1 and less than or equal to M; the wavelength division multiplexer is used to combine the Q modulated optical signals and transmit them to the optical amplifier; the second demultiplexer is used to decompose the optical signal output by the optical fiber into N optical signals, wherein the i-th optical signal includes K i modulated optical signals; the i-th optoelectronic demodulation submodule in the optoelectronic demodulation module is used to demodulate the i-th radio frequency signal from the i-th optical signal output by the second de-WDM, and the optoelectronic demodulation module is used to output N radio frequency signals. In this implementation, by combining the RoF transmission system with wavelength division multiplexing (WDM), adding a de-WDM and a WDM, multiple optical signals are decomposed into N channels, and multiple optical signals on one channel are used to modulate one radio frequency signal. By increasing the number of channels using WDM, it is possible to simultaneously transmit multiple RF signals. That is, the RoF transmission system implements multi-input multi-output (MIMO) transmission, thereby improving the performance of the RoF transmission system.

[0013] For example, the number of optical signals corresponding to each channel may be the same or different. The wavelength difference between two adjacent optical signals on each channel may be the same or different. The wavelengths of the multiple optical signals on each channel may all be different, or the wavelengths of the multiple optical signals may be partially the same and partially different.

[0014] In one possible implementation of the first aspect, the optical signal generation module includes any one of the following: an ultra-wideband optical frequency comb generation module based on a mode-locked laser, an optical signal generation module based on fiber nonlinear effects, an optical signal generation module based on an optoelectronic oscillator, an optical signal generation module based on a microring resonator, or an optical signal generation module based on an electro-optical modulator. In this implementation, the complexity of implementing the optical signal generation module can be reduced, and the implementation cost of the optical signal generation module can be reduced.

[0015] In one possible implementation of the first aspect, when the optical signal generation module includes an ultra-wideband optical frequency comb generation module, the first wavelength division multiplexer demultiplexes the multiple optical signals generated by the optical signal generation module into N channels, wherein the number of optical signals included in different channels may be the same or different, and the wavelength difference between two adjacent optical signals in each channel is the same. In this implementation, the optical signal generation module based on a fiber mode-locked laser has advantages such as small size, light weight, low cost, and easy maintenance.

[0016] In a possible implementation of the first aspect, the wavelengths of the multiple optical signals generated by the optical signal generation module are in a low-dispersion band. In this implementation, the influence of fiber dispersion can be reduced and the power of the RF signal recovered from the multiple modulated optical signals can be increased.

[0017] For example, for G.652E optical fiber, the wavelength of the corresponding low-dispersion band can be between 1300nm and 1324nm. That is, when the system uses G.652E optical fiber, the wavelength range of the multiple optical signals generated by the optical signal generating module can all be between 1300nm and 1324nm, that is, the wavelength of the low-dispersion region is adopted, thereby reducing the influence of optical fiber dispersion and improving the RF signal power recovered from multiple optical signals of different wavelengths.

[0018] For G.654E optical fiber, the corresponding low-dispersion wavelength band is in the 1550nm band. That is, when the RoF transmission system uses G.654E optical fiber, the wavelengths of the multiple optical signals generated by the optical signal generation module can all be within the 1550nm band, for example, between 1540 and 1560nm. This reduces the impact of optical fiber dispersion and increases the RF signal power recovered from multiple optical signals of different wavelengths.

[0019] In one possible implementation of the first aspect, the optical fiber further includes a dispersion compensator configured to compensate for dispersion of the modulated optical signal during transmission through the optical fiber. In this implementation, the impact of optical fiber dispersion can be reduced, thereby increasing the power of the RF signal recovered from the multiple modulated optical signals.

[0020] In a possible implementation of the first aspect, among the multiple optical signals generated by the optical signal generating module, a wavelength interval Δλ between two adjacent optical signals satisfies the following condition:

[0021]

[0022] Among them, n is a positive integer, f RFirepresents the frequency of the RF signal modulated onto the multiple optical signals, D(λ) represents the dispersion coefficient of the optical fiber, and L represents the optical fiber length. In this implementation, the effects of optical fiber dispersion can be reduced, and the power of the RF signal recovered from the multiple modulated optical signals can be increased.

[0023] In a possible implementation manner of the first aspect, the wavelengths of the multiple optical signals generated by the optical signal generating module are all different.

[0024] In a second aspect, a communication device is provided, comprising: an electro-optical modulation module and a first optical fiber, wherein the electro-optical modulation module is configured to receive a radio frequency signal and multiple optical signals, modulate the radio frequency signal onto the multiple optical signals to obtain multiple modulated optical signals, and transmit the multiple modulated optical signals to the first optical fiber; and the first optical fiber is configured to transmit the multiple modulated optical signals.

[0025] The communication device provided in the second aspect uses an electro-optical modulation module to modulate the RF signal into multiple optical signals, and transmits the multiple optical signals obtained after modulation in the optical fiber, thereby broadening the spectrum of the incoming optical signal, reducing the energy density of the incoming optical fiber, and thus increasing the power of the optical signal incident to the optical fiber.

[0026] In a possible implementation of the second aspect, the communication device may further include: an optoelectronic demodulation module, configured to demodulate and output a radio frequency signal from the multiple modulated optical signals output from the first optical fiber.

[0027] In a possible implementation of the second aspect, the communication device further includes: an optical signal generating module, a radio frequency signal generating module, and an optical amplifier, wherein the optical signal generating module is configured to generate the multiple optical signals and transmit the multiple optical signals to the electro-optical modulation module; the radio frequency signal generating module is configured to generate the radio frequency signal and transmit the radio frequency signal to the electro-optical modulation module; and the optical amplifier is configured to receive the multiple modulated optical signals output by the electro-optical modulation module, amplify the power of the multiple modulated optical signals, and transmit the power-amplified multiple modulated optical signals to the first optical fiber. In this implementation, the power amplification by the optical amplifier can improve the transmission efficiency of the multiple modulated optical signals in the optical fiber.

[0028] In a possible implementation of the second aspect, the communication device further includes: an optical circulator, a reflected light power detection module, and a feedback control unit, wherein a first port of the optical circulator is connected to the output end of the optical amplifier, a second port of the optical circulator is connected to the input end of the first optical fiber, a third port of the optical circulator is connected to the input end of the reflected light power detection module, an output end of the reflected light power detection module is connected to the input end of the feedback control unit, and an output end of the feedback control unit is connected to the optical signal generation module; the reflected light power detection module is configured to detect the reflected light power of multiple modulated optical signals transmitted in the first optical fiber, and when the reflected light power is greater than or equal to a first threshold, send a first signal to the feedback control unit; the feedback control unit is configured to receive the first signal, generate a second signal based on the first signal, and send the second signal to the optical signal generation module; the optical signal generation module is configured to receive the second signal and adjust the wavelength and / or quantity of the generated multiple optical signals based on the second signal. In this implementation, the flexibility of the communication device can be improved. When the power of the optical signal incident on the optical fiber is greater than or equal to the preset SBS threshold power, the number and / or wavelength of the optical signal generated by the optical signal generating module is adjusted in a timely manner to ensure that the power of the optical signal incident on the optical fiber is less than the SBS threshold power. This can improve the stability and performance of the communication device on the basis of increasing the power of the optical signal incident on the optical fiber.

[0029] In a possible implementation of the second aspect, the radio frequency signal generating module is used to generate N radio frequency signals, the electro-optical modulation module includes N electro-optical modulation sub-modules, and the optical signal generating module generates M optical signals. The communication device also includes: a first de-wavelength division multiplexer and a wavelength division multiplexer, wherein the first de-wavelength division multiplexer is used to receive the M optical signals generated by the optical signal generating module and decompose the M optical signals generated by the optical signal generating module into N channels, where M is an integer greater than 1, and the i-th channel includes K i optical signal, i is an integer greater than or equal to 1 and less than or equal to N; the i-th electro-optical modulation submodule is used to receive the i-th RF signal generated by the RF signal generating module and the K signal included on the i-th channel i optical signal, and modulate the ith RF signal onto the K i On the optical signal, we get K imodulated optical signals, N electro-optical modulation submodules output Q modulated optical signals, where Q is an integer greater than or equal to 1 and less than or equal to M; the wavelength division multiplexer is used to receive the Q modulated optical signals, combine the Q modulated optical signals, and transmit them to the optical amplifier. In this implementation, by combining the communication device with WDM and adding a demultiplexer and a wavelength division multiplexer, multiple optical signals are decomposed into N channels, and multiple optical signals on one channel are used to modulate one radio frequency signal. By increasing the number of channels using WDM, it is possible to simultaneously transmit multiple RF signals, that is, using this communication device to implement MIMO transmission, thereby improving the performance of the communication device.

[0030] In one possible implementation of the second aspect, the optical signal generation module includes one of the following: an ultra-wideband optical frequency comb generation module based on a mode-locked laser, an optical signal generation module based on fiber nonlinear effects, an optical signal generation module based on an optoelectronic oscillator, an optical signal generation module based on a microring resonator, or an optical signal generation module based on an electro-optical modulator. In this implementation, the complexity of implementing the optical signal generation module can be reduced, and the implementation cost of the optical signal generation module can be reduced.

[0031] In one possible implementation of the second aspect, when the optical signal generation module includes an ultra-wideband optical frequency comb generation module, the first wavelength division multiplexer demultiplexes the M optical signals generated by the optical signal generation module into N channels, wherein the number of optical signals included in different channels within the N channels may be the same or different, and the wavelength difference between two adjacent optical signals in each channel is the same. In this implementation, the optical signal generation module based on a fiber mode-locked laser has advantages such as small size, light weight, low cost, and easy maintenance.

[0032] In a possible implementation of the second aspect, the wavelengths of the multiple optical signals generated by the optical signal generation module are in a low-dispersion band. In this implementation, the influence of fiber dispersion can be reduced and the power of the RF signal recovered from the multiple modulated optical signals can be increased.

[0033] In one possible implementation of the second aspect, the first optical fiber further includes a dispersion compensator configured to compensate for dispersion of the modulated optical signal during transmission through the first optical fiber. This implementation reduces the impact of optical fiber dispersion and increases the power of RF signals recovered from the multiple modulated optical signals.

[0034] In a possible implementation of the second aspect, among the multiple optical signals generated by the optical signal generating module, a wavelength interval Δλ between two adjacent optical signals satisfies the following condition:

[0035]

[0036] Among them, n is a positive integer, f RFi represents the frequency of the RF signal modulated onto the multiple optical signals, D(λ) represents the dispersion coefficient of the optical fiber, and L represents the length of the first optical fiber. In this implementation, the impact of optical fiber dispersion can be reduced, and the power of the RF signal recovered from the multiple modulated optical signals can be increased.

[0037] In a possible implementation manner of the second aspect, the wavelengths of the multiple optical signals are different.

[0038] In a third aspect, a communication device is provided, comprising: a second optical fiber and an optoelectronic demodulation module, wherein the second optical fiber is used to receive and transmit multiple modulated optical signals, where the multiple modulated optical signals are obtained by modulating a radio frequency signal onto multiple optical signals; and the optoelectronic demodulation module is used to demodulate and output the radio frequency signal from the multiple modulated optical signals output by the second optical fiber.

[0039] The communication device provided in the third aspect transmits the multiple optical signals obtained after modulation in the second optical fiber, and finally demodulates the RF signal modulated on the multiple optical signals through the optoelectronic demodulation module at the output end of the second optical fiber, thereby broadening the spectrum of the incoming optical signal, reducing the energy density of the incoming optical fiber, thereby increasing the power of the optical signal incident to the optical fiber, and improving the transmission efficiency of the RF signal.

[0040] In a possible implementation of the third aspect, the device may further include: an electro-optical modulation module: the electro-optical modulation module is used to modulate the radio frequency signal onto multiple optical signals to obtain multiple modulated optical signals, and the second optical fiber is used to transmit the multiple modulated optical signals.

[0041] In a possible implementation of the third aspect, the optoelectronic demodulation module includes N optoelectronic demodulation submodules, the multiple modulated optical signals are obtained by modulating N radio frequency signals onto multiple optical signals, and the communication device also includes: a second de-wavelength division multiplexer; the second de-wavelength division multiplexer is used to receive the multiple modulated optical signals output by the second optical fiber, and decompose the multiple modulated optical signals output by the second optical fiber into N optical signals, wherein the i-th optical signal includes K i modulated optical signals, where i is an integer greater than or equal to 1 and less than or equal to N; the i-th optoelectronic demodulation submodule in the optoelectronic demodulation module is configured to receive the i-th optical signal output by the second wavelength division multiplexer and demodulate the i-th radio frequency signal from the i-th optical signal, and the optoelectronic demodulation module is configured to output N radio frequency signals. In this implementation, by combining the communication device with WDM and utilizing WDM to increase the number of channels, simultaneous transmission of multiple RF signals can be achieved, i.e., MIMO transmission is implemented using the communication device, thereby improving the performance of the communication device.

[0042] In a possible implementation of the third aspect, among the N optical signals, the number of optical signals included in different optical signals is the same or different, and the number of optical signals included in the i-th optical signal is K i In the modulated optical signals, the wavelength difference between two adjacent optical signals is the same.

[0043] In one possible implementation of the third aspect, the second optical fiber further includes a dispersion compensator configured to compensate for dispersion of the multiple modulated optical signals during transmission within the second optical fiber. In this implementation, the impact of optical fiber dispersion can be reduced, and the power of RF signals recovered from the multiple modulated optical signals can be increased.

[0044] In a possible implementation manner of the third aspect, the wavelengths of the multiple optical signals are all different.

[0045] In a fourth aspect, a radio frequency over light transmission system is provided, which includes: a communication device provided in the second aspect or any possible implementation of the second aspect, and a communication device provided in the third aspect or any possible implementation of the third aspect.

[0046] In a fifth aspect, a method for transmitting a radio frequency signal is provided. The method can be applied to the optical radio frequency transmission system provided by the first aspect or any possible implementation of the first aspect, or to the optical radio frequency transmission system provided by the fourth aspect. The method includes: an electro-optical modulation module receives a radio frequency signal and multiple optical signals, modulates the radio frequency signal onto the multiple optical signals to obtain multiple modulated optical signals, and transmits the multiple modulated optical signals to an optical fiber; after receiving the multiple modulated optical signals, the optical fiber transmits the multiple modulated optical signals to an optoelectronic demodulation module; after receiving the multiple modulated optical signals, the optoelectronic demodulation module demodulates and outputs the radio frequency signal from the multiple modulated optical signals.

[0047] The fifth aspect provides a method for transmitting radio frequency signals, which modulates the RF signal onto multiple optical signals, transmits the multiple optical signals obtained after modulation in an optical fiber, and finally demodulates the RF signal modulated on the multiple optical signals at the output end of the optical fiber transmission, thereby broadening the spectrum of the incoming optical signal, reducing the energy density of the incoming optical fiber, thereby increasing the power of the optical signal incident to the optical fiber, and improving the transmission performance and transmission efficiency of the RF signal.

[0048] In a possible implementation of the fifth aspect, the method further includes: an optical signal generating module generating the multiple optical signals and transmitting the multiple optical signals to the electro-optical modulation module; a radio frequency signal generating module generating the radio frequency signal and transmitting the radio frequency signal to the electro-optical modulation module; and an optical amplifier receiving the multiple modulated optical signals transmitted by the electro-optical modulation module, amplifying the power of the multiple modulated optical signals, and transmitting the multiple modulated optical signals after power amplification to the optical fiber.

[0049] In a possible implementation of the fifth aspect, the method further includes: a reflected light power detection module detecting the reflected light power of multiple modulated optical signals transmitted in the optical fiber; when the reflected light power is greater than or equal to a first threshold, the reflected light power detection module sending a first signal to a feedback control unit; the feedback control unit receiving the first signal, generating a second signal based on the first signal, and sending the second signal to the optical signal generation module; the optical signal generation module receiving the second signal, and adjusting the wavelengths and / or number of the multiple optical signals generated based on the second signal. In this implementation, when the power of the optical signal incident on the optical fiber is greater than or equal to a preset SBS threshold power, the number and / or wavelength of the optical signals generated by the optical signal generation module are promptly adjusted to ensure that the power of the optical signal incident on the optical fiber is less than the SBS threshold power, thereby further improving the transmission performance and efficiency of the RF signal on the basis of increasing the power of the optical signal incident on the optical fiber.

[0050] In a possible implementation of the fifth aspect, the electro-optical modulation module includes N electro-optical modulation sub-modules, the radio frequency signal generation module generates N radio frequency signals, the optical signal generation module generates M optical signals, and the optoelectronic demodulation module includes N optoelectronic demodulation sub-modules. The method also includes: a first demultiplexer receives the M optical signals generated by the optical signal generation module, decomposes the M optical signals into N channels, where M is an integer greater than 1, and the i-th channel includes K i optical signals, i is an integer greater than or equal to 1 and less than or equal to N, and the K i The optical signal is transmitted to the i-th electro-optical modulation submodule; the i-th electro-optical modulation submodule receives the i-th RF signal and the K i Optical signal, modulate the ith RF signal to the K i On the optical signal, we get K i modulated optical signal, and K iThe modulated optical signals are transmitted to a wavelength division multiplexer, and N electro-optical modulation submodules output Q modulated optical signals, where Q is an integer greater than or equal to 1 and less than or equal to M. The wavelength division multiplexer receives the Q modulated optical signals, combines the Q modulated optical signals, and transmits them to the optical amplifier. The second demultiplexer receives the optical signal output by the optical fiber, decomposes the optical signal output by the optical fiber into N optical signals, and transmits the i-th optical signal to the i-th optoelectronic demodulation submodule in the optoelectronic demodulation module.

[0051] Among them, the i-th optical signal includes K i The i-th optoelectronic demodulation submodule in the optoelectronic demodulation module receives the i-th optical signal and demodulates it into the i-th RF signal. The optoelectronic demodulation module then outputs N RF signals. In this implementation, multiple optical signals are decomposed into N channels, and multiple optical signals on one channel are used to modulate one RF signal. By increasing the number of channels using WDM, multiple RF signals can be transmitted simultaneously. This means that the RoF transmission system implements MIMO transmission, improving the performance of the RoF transmission system.

[0052] In a possible implementation of the fifth aspect, when the optical signal generating module includes an ultra-wideband optical frequency comb generating module, the number of optical signals included in different channels of the N channels is the same or different, and among the multiple optical signals included in each channel, the wavelength difference between two adjacent optical signals is the same.

[0053] In a possible implementation of the fifth aspect, the wavelengths of the multiple optical signals are in a low dispersion band.

[0054] In a possible implementation of the fifth aspect, among the multiple optical signals, a wavelength interval Δλ between two adjacent optical signals satisfies the following condition:

[0055]

[0056] Among them, n is a positive integer, f RFi represents the frequency of the radio frequency signal modulated onto the multiple optical signals, D(λ) represents the dispersion coefficient of the optical fiber, and L represents the length of the optical fiber.

[0057] In a possible implementation of the fifth aspect, the wavelengths of the multiple optical signals are all different.

[0058] In a sixth aspect, a method for transmitting a radio frequency signal is provided. The method can be applied to the communication device provided by the second aspect or any possible implementation of the second aspect. The method includes: an electro-optical modulation module receives a radio frequency signal and multiple optical signals, modulates the radio frequency signal onto the multiple optical signals to obtain multiple modulated optical signals, and transmits the multiple modulated optical signals to a first optical fiber, and the first optical fiber transmits the multiple modulated optical signals.

[0059] The sixth aspect provides a method for transmitting radio frequency signals, which modulates the RF signal onto multiple optical signals and transmits the multiple optical signals obtained after modulation in an optical fiber, thereby broadening the spectrum of the incoming optical signal, reducing the energy density of the incoming optical fiber, and thus increasing the power of the optical signal incident on the optical fiber.

[0060] In a possible implementation of the sixth aspect, the method further includes: the optical signal generating module generates the multiple optical signals and transmits the multiple optical signals to the electro-optical modulation module; the radio frequency signal generating module generates the radio frequency signal and transmits the radio frequency signal to the electro-optical modulation module; the optical amplifier receives the multiple modulated optical signals output by the electro-optical modulation module, amplifies the power of the multiple modulated optical signals, and transmits the multiple modulated optical signals after power amplification to the first optical fiber.

[0061] In a possible implementation of the sixth aspect, the method further includes: a reflected light power detection module detecting the reflected light power of multiple modulated optical signals transmitted in the first optical fiber, and when the reflected light power is greater than or equal to a first threshold, sending a first signal to the feedback control unit; the feedback control unit receiving the first signal, generating a second signal based on the first signal, and sending the second signal to the optical signal generation module; the optical signal generation module receiving the second signal, and adjusting the wavelengths and / or quantity of the multiple optical signals generated based on the second signal. In this implementation, when the power of the optical signal incident on the optical fiber is greater than or equal to a preset SBS threshold power, the quantity and / or wavelength of the optical signal generated by the optical signal generation module is promptly adjusted to ensure that the power of the optical signal incident on the optical fiber is less than the SBS threshold power, thereby improving the stability of the optical signal incident on the optical fiber while increasing the power of the optical signal incident on the optical fiber.

[0062] In a possible implementation of the sixth aspect, the method further includes: the radio frequency signal generating module generates N radio frequency signals, the electro-optical modulation module includes N electro-optical modulation sub-modules, the optical signal generating module generates M optical signals, a first de-wavelength division multiplexer receives the M optical signals generated by the optical signal generating module, and decomposes the M optical signals generated by the optical signal generating module into N channels, where M is an integer greater than 1, and the i-th channel includes K ioptical signal, i is an integer greater than or equal to 1 and less than or equal to N; the i-th electro-optical modulation submodule receives the i-th RF signal generated by the RF signal generation module and the K signal included on the i-th channel i optical signal, and modulate the ith RF signal onto the K i On the optical signal, we get K i The optical amplifier is a device that receives multiple optical signals and outputs Q modulated optical signals from N electro-optical modulation submodules, where Q is an integer greater than or equal to 1 and less than or equal to M. A wavelength division multiplexer receives these Q modulated optical signals, combines them, and transmits them to the optical amplifier. In this implementation, multiple optical signals are decomposed into N channels, and multiple optical signals on a channel are used to modulate a single RF signal. By increasing the number of channels using WDM, multiple RF signals can be transmitted simultaneously, thus achieving MIMO transmission and further improving the transmission efficiency of RF signals.

[0063] In a possible implementation of the sixth aspect, the number of optical signals included in different channels among the N channels is the same or different, and among the multiple optical signals included in each channel, the wavelength difference between two adjacent optical signals is the same.

[0064] In a possible implementation of the sixth aspect, the wavelengths of the multiple optical signals generated by the optical signal generating module are in a low dispersion band.

[0065] In a possible implementation of the sixth aspect, the wavelengths of the multiple optical signals are all different.

[0066] In the seventh aspect, a method for transmitting a radio frequency signal is provided, which can be applied to the communication device provided by the third aspect or any possible implementation of the third aspect. The method includes: a second optical fiber receives and transmits multiple modulated optical signals, and transmits the multiple modulated optical signals to an optoelectronic demodulation module; the multiple modulated optical signals are obtained by modulating the radio frequency signal onto multiple optical signals; the optoelectronic demodulation module receives the multiple modulated optical signals, demodulates the multiple modulated optical signals output by the second optical fiber, and outputs the radio frequency signal.

[0067] The seventh aspect provides a method for transmitting radio frequency signals, which modulates the RF signal onto multiple optical signals, transmits the multiple optical signals obtained after modulation in an optical fiber, and finally demodulates the RF signal modulated on the multiple optical signals at the output end of the optical fiber transmission, thereby achieving the broadening of the spectrum of the incoming optical signal, reducing the energy density of the incoming optical fiber, thereby increasing the power of the optical signal incident to the optical fiber, and improving the transmission performance and transmission efficiency of the RF signal.

[0068] In a possible implementation of the seventh aspect, the optoelectronic demodulation module includes N optoelectronic demodulation submodules, the multiple modulated optical signals are obtained by modulating N radio frequency signals onto multiple optical signals, and the method further includes: a second demultiplexer receives the multiple modulated optical signals output by the second optical fiber, and decomposes the multiple modulated optical signals output by the second optical fiber into N optical signals, wherein the i-th optical signal includes K i modulated optical signals, where i is an integer greater than or equal to 1 and less than or equal to N; the i-th optoelectronic demodulation submodule in the optoelectronic demodulation module receives the i-th optical signal output by the second wavelength division multiplexer and demodulates the i-th radio frequency signal from the i-th optical signal. The optoelectronic demodulation module is configured to output N radio frequency signals. In this implementation, WDM increases the number of channels, enabling simultaneous transmission of multiple RF signals, i.e., achieving MIMO transmission, further improving RF signal transmission efficiency.

[0069] In a possible implementation of the seventh aspect, among the N optical signals, the number of optical signals included in different optical signals is the same or different, and the number of optical signals included in the i-th optical signal is K i In the modulated optical signals, the wavelength difference between two adjacent optical signals is the same.

[0070] In a possible implementation of the seventh aspect, the wavelengths of the multiple optical signals are different.

[0071] In an eighth aspect, a light-carrying radio frequency transmission system is provided, which includes: an electro-optical modulation module: the electro-optical modulation module is used to modulate the radio frequency signal onto the optical signal to obtain a modulated optical signal; a combiner: the combiner is used to combine multiple optical signals that have not been electro-optically modulated and the modulated optical signal into one optical signal; an optical fiber: the optical fiber is used to transmit the optical signal output by the combiner; and an optoelectronic demodulation module: the optoelectronic demodulation module is used to demodulate and output the radio frequency signal from the optical signal output by the optical fiber.

[0072] The eighth aspect provides a radio frequency over fiber transmission system that modulates an RF signal into an optical signal, combines this modulated optical signal with other unmodulated optical signals, and transmits them through an optical fiber. Ultimately, the RF signal modulated on the optical signal is demodulated at the output end of the optical fiber transmission. In other words, by treating the other unmodulated optical signals as interfering optical signals and transmitting them together with the modulated RF signal through the optical fiber, the optical signal spectrum can be broadened, reducing the optical energy density of the input fiber and increasing the optical signal power incident on the fiber. This increases the SBS power threshold, thereby improving the performance and transmission efficiency of the RoF transmission system.

[0073] In a possible implementation of the eighth aspect, the radio frequency over light transmission system further includes: an optical signal generating module configured to generate the multiple optical signals that are not electro-optically modulated; a radio frequency signal generating module configured to generate the radio frequency signal; and an optical amplifier configured to amplify the power of the optical signal and transmit the power-amplified optical signal to the optical fiber. In this implementation, the power amplification by the optical amplifier can improve the transmission efficiency of the optical signal in the optical fiber.

[0074] In a possible implementation of the eighth aspect, the system further includes: an optical circulator, a reflected light power detection module, and a feedback control unit, wherein a first port of the optical circulator is connected to the output end of the optical amplifier, a second port of the optical circulator is connected to the input end of the optical fiber, a third port of the optical circulator is connected to the input end of the reflected light power detection module, an output end of the reflected light power detection module is connected to the input end of the feedback control unit, and an output end of the feedback control unit is connected to the optical signal generating module; the reflected light power detection module is configured to: detect the reflected light power of multiple modulated optical signals transmitted in the optical fiber, and when the reflected light power is greater than or equal to a first threshold, send a first signal to the feedback control unit; the feedback control unit is configured to generate a second signal under the action of the first signal and transmit the second signal to the optical signal generating module; the optical signal generating module is configured to adjust the wavelength and / or quantity of the generated multiple non-electro-optically modulated optical signals according to the second signal. In this implementation, by providing a reflected light power detection module and a feedback control unit, the flexibility of the RoF transmission system can be improved. When the power of the optical signal incident on the optical fiber is greater than or equal to the preset SBS threshold power, the number and / or wavelength of the optical signal generated by the optical signal generation module are promptly adjusted to ensure that the power of the optical signal incident on the optical fiber is less than the SBS threshold power. This can improve the stability and performance of the RoF transmission system on the basis of increasing the power of the optical signal incident on the optical fiber.

[0075] In a possible implementation of the eighth aspect, the electro-optical modulation module includes: an electro-optical modulation module of a direct modulation mode or an electro-optical modulation module of an indirect modulation mode, the electro-optical modulation module of the direct modulation mode is used to generate an optical signal and modulate the radio frequency signal, the optical modulation module of the indirect modulation mode includes a light source generation module and an electro-optical modulation sub-module, the light source generation module is used to generate an optical signal, and the electro-optical modulation sub-module is used to modulate the radio frequency signal onto the optical signal to obtain a modulated optical signal. In this implementation, the use of the electro-optical modulation module of the direct modulation mode can reduce the complexity of the optical modulation module implementation and reduce the cost. The use of the electro-optical modulation module of the indirect modulation mode can improve the efficiency of modulating the radio frequency signal onto the optical signal and reduce the power loss in the modulation process.

[0076] In one possible implementation of the eighth aspect, when the electro-optical modulation module includes the indirect modulation electro-optical modulation module, the wavelength of the optical signal generated by the light source generation module is the same as the wavelength of any one of the multiple non-electro-optically modulated optical signals. In this implementation, the RoF transmission system can transmit higher-frequency RF signals, thereby improving the performance of the RoF transmission system.

[0077] In one possible implementation of the eighth aspect, when the electro-optical modulation module includes the indirect modulation electro-optical modulation module, the wavelength of the optical signal generated by the light source generation module is different from the wavelength of any optical signal among the multiple non-electro-optically modulated optical signals. In this implementation, the light source of the electro-optical modulation module can be independent of the optical signal generation module, thereby increasing the flexibility of the RoF transmission system.

[0078] In one possible implementation of the eighth aspect, the optical signal generation module includes any one of the following: an ultra-wideband optical frequency comb generation module based on a mode-locked laser, an optical signal generation module based on fiber nonlinear effects, an optical signal generation module based on an optoelectronic oscillator, an optical signal generation module based on a microring resonator, or an optical signal generation module based on an electro-optical modulator. In this implementation, the complexity of implementing the optical signal generation module can be reduced, and the implementation cost of the optical signal generation module can be reduced.

[0079] In one possible implementation of the eighth aspect, the wavelengths of the multiple optical signals generated by the optical signal generation module without electro-optical modulation are within a low-dispersion band. In this implementation, the influence of optical fiber dispersion can be reduced, and the power of the RF signal recovered from the multiple modulated optical signals can be increased.

[0080] In one possible implementation of the eighth aspect, the optical fiber further includes a dispersion compensator configured to compensate for dispersion of the modulated optical signal during transmission through the optical fiber. In this implementation, the impact of optical fiber dispersion can be reduced, and the power of the RF signal recovered from the multiple modulated optical signals can be increased.

[0081] In a possible implementation of the eighth aspect, the wavelengths of the multiple optical signals that have not been electro-optically modulated are all different, or some are the same and some are different.

[0082] In a ninth aspect, a communication device is provided, comprising: an electro-optical modulation module, a combiner, and a third optical fiber, wherein the electro-optical modulation module is used to receive a radio frequency signal, modulate the radio frequency signal onto an optical signal, obtain a modulated optical signal, and transmit the modulated optical signal to the combiner; the combiner is used to receive the modulated optical signal and multiple optical signals that have not been electro-optically modulated, combine the multiple optical signals that have not been electro-optically modulated and the modulated optical signal into one optical signal, and transmit the signal to the third optical fiber; and the third optical fiber is used to transmit the optical signal output by the combiner.

[0083] The communication device provided in the ninth aspect modulates an RF signal into an optical signal, combines the modulated optical signal with other unmodulated optical signals, and transmits the combined signal through an optical fiber. In other words, the unmodulated optical signal is used as an interference optical signal and transmitted along with the modulated RF signal through the optical fiber. This broadens the optical signal spectrum, reduces the optical energy density of the input light, and increases the optical signal power incident on the optical fiber, thereby increasing the SBS power threshold. This improves the performance and transmission efficiency of the communication device.

[0084] In a possible implementation of the ninth aspect, the communication device further includes: an optical signal generating module, a radio frequency signal generating module, and an optical amplifier, wherein the optical signal generating module is configured to generate the multiple optical signals that have not been electro-optically modulated and transmit the multiple optical signals that have not been electro-optically modulated to the combiner; the radio frequency signal generating module is configured to generate the radio frequency signal and transmit the radio frequency signal to the electro-optical modulation module; and the optical amplifier is configured to receive the optical signal output by the combiner, amplify the power of the optical signal output by the combiner, and transmit the power-amplified optical signal to a third optical fiber. In this implementation, the power amplification of the optical amplifier can improve the transmission efficiency of the multiple modulated optical signals in the optical fiber.

[0085] In a possible implementation of the ninth aspect, the communication device further includes: an optical circulator, a reflected light power detection module, and a feedback control unit, wherein the first port of the optical circulator is connected to the output end of the optical amplifier, the second port of the optical circulator is connected to the input end of the third optical fiber, the third port of the optical circulator is connected to the input end of the reflected light power detection module, the output end of the reflected light power detection module is connected to the input end of the feedback control unit, and the output end of the feedback control unit is connected to the optical signal generating module; the reflected light power detection module is used to: detect the reflected light power of the optical signal transmitted in the third optical fiber, and when the reflected light power is greater than or equal to a first threshold, send a first signal to the feedback control unit; the feedback control unit is used to receive the first signal, generate a second signal based on the first signal, and send the second signal to the optical signal generating module; the optical signal generating module is used to receive the second signal and adjust the wavelength and / or quantity of the multiple generated optical signals that are not electro-optically modulated based on the second signal. In this implementation, by providing a reflected light power detection module and a feedback control unit, the flexibility of the communication device can be improved. When the power of the optical signal incident on the optical fiber is greater than or equal to the preset SBS threshold power, the number and / or wavelength of the optical signal generated by the optical signal generation module are adjusted in a timely manner, ensuring that the power of the optical signal incident on the optical fiber is less than the SBS threshold power. This can improve the stability and performance of the communication device on the basis of increasing the power of the optical signal incident on the optical fiber.

[0086] In a possible implementation of the ninth aspect, the electro-optical modulation module includes: a direct modulation electro-optical modulation module or an indirect modulation electro-optical modulation module, the direct modulation electro-optical modulation module is used to generate the optical signal and modulate the radio frequency signal, and transmit the modulated optical signal to the combiner; the indirect modulation optical modulation module includes a light source generation module and an electro-optical modulation sub-module, the light source generation module is used to generate the optical signal, the electro-optical modulation sub-module is used to modulate the radio frequency signal onto the optical signal generated by the light source to obtain the modulated optical signal, and transmit the modulated optical signal to the combiner. In this implementation, the use of the direct modulation electro-optical modulation module can reduce the complexity of the optical modulation module implementation and reduce costs. The use of the indirect modulation electro-optical modulation module can improve the efficiency of modulating the radio frequency signal onto the optical signal and reduce the power loss in the modulation process.

[0087] In one possible implementation of the ninth aspect, when the electro-optical modulation module includes an electro-optical modulation module using the indirect modulation method, the wavelength of the optical signal generated by the light source generation module is the same as or different from the wavelength of any one of the multiple non-electro-optically modulated optical signals. In this implementation, the light source of the electro-optical modulation module can be independent of the optical signal generation module, thereby increasing the flexibility of the communication device system.

[0088] In a possible implementation of the ninth aspect, the optical signal generating module includes one of the following: an ultra-wideband optical frequency comb generating module based on a mode-locked laser, an optical signal generating module based on an optical fiber nonlinear effect, an optical signal generating module based on an optoelectronic oscillator, an optical signal generating module based on a microring resonator, or an optical signal generating module based on an electro-optical modulator.

[0089] In one possible implementation of the ninth aspect, the wavelengths of the multiple optical signals generated by the optical signal generation module without electro-optical modulation are within a low-dispersion band. In this implementation, the influence of optical fiber dispersion can be reduced, and the power of the RF signal recovered from the multiple modulated optical signals can be increased.

[0090] In one possible implementation of the ninth aspect, the third optical fiber further includes a dispersion compensator configured to compensate for dispersion of the optical signal during transmission through the third optical fiber. In this implementation, the impact of optical fiber dispersion can be reduced, thereby increasing the power of the RF signal recovered from the multiple modulated optical signals.

[0091] In a possible implementation of the ninth aspect, the wavelengths of the multiple optical signals that have not been electro-optically modulated are different.

[0092] In a tenth aspect, a communication device is provided, comprising: a fourth optical fiber and an optoelectronic demodulation module, the fourth optical fiber being used to receive and transmit an optical signal, the optical signal transmitted by the fourth optical fiber being obtained by combining multiple optical signals that have not been electro-optically modulated and an optical signal that has been electro-optically modulated into one optical signal, and the optical signal that has been electro-optically modulated being obtained by modulating a radio frequency signal onto the optical signal; the optoelectronic demodulation module being used to receive the optical signal output by the fourth optical fiber, and to demodulate and output the radio frequency signal from the optical signal output by the fourth optical fiber.

[0093] The communication device provided in the tenth aspect modulates an RF signal into an optical signal, combines the modulated optical signal with other unmodulated optical signals, and transmits the combined signal through a fourth optical fiber. Ultimately, the RF signal modulated on the optical signal is demodulated at the output end of the fourth optical fiber. In other words, by treating the other unmodulated optical signals as interfering optical signals and transmitting them together with the modulated RF signal through the optical fiber, the optical signal spectrum is broadened, the energy density of the incoming light is reduced, and the power of the optical signal incident on the optical fiber is increased, i.e., the SBS power threshold is increased, thereby improving the performance and transmission efficiency of the communication device.

[0094] In a possible implementation of the tenth aspect, the wavelengths of the multiple optical signals that have not been electro-optically modulated are in a low-dispersion band. In this implementation, the influence of optical fiber dispersion can be reduced and the power of the RF signal recovered from the multiple modulated optical signals can be increased.

[0095] In one possible implementation of the tenth aspect, the fourth optical fiber further includes a dispersion compensator configured to compensate for dispersion of the optical signal during transmission in the fourth optical fiber. In this implementation, the impact of optical fiber dispersion can be reduced, and the power of the RF signal recovered from the multiple modulated optical signals can be increased.

[0096] In a possible implementation of the tenth aspect, the wavelengths of the multiple optical signals that have not been electro-optically modulated are different.

[0097] In the eleventh aspect, a radio frequency transmission system over light is provided, which includes: the communication device provided in the ninth aspect or any possible implementation of the ninth aspect, and the communication device provided in the tenth aspect or any possible implementation of the tenth aspect.

[0098] In the twelfth aspect, a method for transmitting a radio frequency signal is provided. The method can be applied to the radio frequency transmission system over light provided in the eighth aspect or any possible implementation of the eighth aspect, or applied to the radio frequency transmission system over light provided in the eleventh aspect, the method comprising: the electro-optical modulation module receives the radio frequency signal, modulates the radio frequency signal onto the optical signal to obtain the modulated optical signal, and transmits the modulated optical signal to the combiner; the combiner receives the modulated optical signal and multiple optical signals that have not been electro-optically modulated, combines the multiple optical signals that have not been electro-optically modulated and the modulated optical signal into one optical signal and transmits it to the optical fiber; the optical fiber transmits the optical signal output by the combiner to the optoelectronic demodulation module; the optoelectronic demodulation module receives the optical signal output by the optical fiber, and demodulates and outputs the radio frequency signal from the optical signal output by the optical fiber.

[0099] The twelfth aspect provides a method for transmitting radio frequency signals, which modulates an RF signal into an optical signal, combines the modulated optical signal with other unmodulated optical signals, and transmits the combined signal through an optical fiber. Finally, the RF signal modulated on the optical signal is demodulated at the output end of the optical fiber transmission. In other words, by treating the other unmodulated optical signals as interference optical signals and transmitting them together with the modulated RF signal through the optical fiber, the optical signal spectrum can be broadened, the energy density of the light entering the fiber can be reduced, and the power of the optical signal incident on the fiber can be increased, thereby improving the transmission performance and efficiency of the RF signal.

[0100] In a possible implementation of the twelfth aspect, the method further includes: an optical signal generating module generating the multiple non-electro-optically modulated optical signals and transmitting the multiple non-electro-optically modulated optical signals to the combiner; a radio frequency signal generating module generating the radio frequency signal and transmitting the radio frequency signal to the electro-optical modulation module; an optical amplifier receiving the optical signal output by the combiner, amplifying the power of the optical signal output by the combiner, and transmitting the power-amplified optical signal to the optical fiber. In this implementation, the power amplification of the optical amplifier can improve the transmission efficiency of the optical signal in the optical fiber.

[0101] In a possible implementation of the twelfth aspect, the method further includes: a reflected light power detection module detecting the reflected light power of the multiple modulated optical signals transmitted in the optical fiber, and sending a first signal to the feedback control unit when the reflected light power is greater than or equal to a first threshold; the feedback control unit receiving the first signal, generating a second signal based on the first signal, and sending the second signal to the optical signal generating module; the optical signal generating module receiving the second signal, and adjusting the wavelengths and / or quantity of the multiple non-electro-optically modulated optical signals generated based on the second signal. In this implementation, when the power of the optical signal incident on the optical fiber is greater than or equal to a preset SBS threshold power, the wavelengths and / or quantity of the multiple non-electro-optically modulated optical signals generated by the optical signal generating module are adjusted in a timely manner, ensuring that the power of the optical signal incident on the optical fiber is less than the SBS threshold power, thereby improving the stability of the optical signal incident on the optical fiber on the basis of increasing the power of the optical signal incident on the optical fiber.

[0102] In a possible implementation of the twelfth aspect, when the electro-optical modulation module includes an electro-optical modulation module of the indirect modulation method, the wavelength of the optical signal generated by the light source generating module is the same as or different from the wavelength of any one of the multiple optical signals that have not been electro-optically modulated.

[0103] In a possible implementation of the twelfth aspect, the wavelengths of the multiple optical signals generated by the optical signal generation module without electro-optical modulation are within a low-dispersion band. In this implementation, the influence of optical fiber dispersion can be reduced, and the power of the RF signal recovered from the multiple modulated optical signals can be increased.

[0104] In a possible implementation of the twelfth aspect, the wavelengths of the multiple optical signals that have not been electro-optically modulated are different.

[0105] In the thirteenth aspect, a method for transmitting a radio frequency signal is provided, which can be applied to the communication device provided in the above-mentioned ninth aspect or any possible implementation of the ninth aspect, and the method includes: an electro-optical modulation module receives a radio frequency signal, and modulates the radio frequency signal onto an optical signal to obtain a modulated optical signal, and transmits the modulated optical signal to the combiner; the combiner receives the modulated optical signal and multiple optical signals that have not been electro-optically modulated, combines the multiple optical signals that have not been electro-optically modulated and the modulated optical signal into one optical signal and transmits it to a third optical fiber; the third optical fiber transmits the optical signal output by the combiner.

[0106] A thirteenth aspect provides a method for transmitting radio frequency signals, wherein one RF signal is modulated into an optical signal, and the modulated optical signal is combined with other unmodulated optical signals into one optical signal, which is then transmitted through an optical fiber. In other words, the other unmodulated optical signal is used as an interference optical signal and transmitted together with the modulated RF signal through the optical fiber. This can broaden the optical signal spectrum, reduce the energy density of the light entering the fiber, and increase the optical signal power incident on the fiber, thereby improving the transmission performance and efficiency of the RF signal.

[0107] In a possible implementation of the thirteenth aspect, the method further includes: an optical signal generating module generating the multiple non-electro-optically modulated optical signals and transmitting the multiple non-electro-optically modulated optical signals to the combiner; a radio frequency signal generating module generating the radio frequency signal and transmitting the radio frequency signal to the electro-optical modulation module; and an optical amplifier receiving the optical signal output by the combiner, amplifying the power of the optical signal output by the combiner, and transmitting the power-amplified optical signal to a third optical fiber. In this implementation, the power amplification by the optical amplifier can improve the transmission efficiency of the optical signal in the optical fiber.

[0108] In a possible implementation of the thirteenth aspect, the method further includes: a reflected light power detection module detecting the reflected light power of multiple modulated optical signals transmitted in the third optical fiber, and when the reflected light power is greater than or equal to a first threshold, sending a first signal to a feedback control unit; the feedback control unit receiving the first signal, generating a second signal based on the first signal, and sending the second signal to an optical signal generation module; the optical signal generation module receiving the second signal, and adjusting the wavelengths and / or quantity of the multiple non-electro-optically modulated optical signals generated based on the second signal. In this implementation, when the power of the optical signal incident on the optical fiber is greater than or equal to a preset SBS threshold power, the wavelengths and / or quantity of the multiple non-electro-optically modulated optical signals generated by the optical signal generation module are adjusted in a timely manner, ensuring that the power of the optical signal incident on the optical fiber is less than the SBS threshold power, thereby improving the stability of the optical signal incident on the optical fiber on the basis of increasing the power of the optical signal incident on the optical fiber.

[0109] In a possible implementation of the thirteenth aspect, when the electro-optical modulation module includes an electro-optical modulation module of the indirect modulation method, the wavelength of the optical signal generated by the light source generating module is the same as or different from the wavelength of any one of the multiple optical signals that have not been electro-optically modulated.

[0110] In one possible implementation of the thirteenth aspect, the wavelengths of the multiple optical signals generated by the optical signal generation module without electro-optical modulation are within a low-dispersion band. In this implementation, the influence of optical fiber dispersion can be reduced, and the power of the RF signal recovered from the multiple modulated optical signals can be increased.

[0111] In a fourteenth aspect, a method for transmitting a radio frequency signal is provided, which can be applied to the communication device provided by the tenth aspect or any possible implementation of the tenth aspect, the method comprising: a fourth optical fiber receives and transmits an optical signal, the optical signal transmitted by the fourth optical fiber is obtained by combining multiple optical signals that have not been electro-optically modulated and an optical signal that has been electro-optically modulated into one optical signal, and the optical signal that has been electro-optically modulated is obtained by modulating a radio frequency signal onto an optical signal; and a photoelectric demodulation module receives the optical signal output by the fourth optical fiber, and demodulates and outputs the radio frequency signal from the optical signal output by the fourth optical fiber.

[0112] Fourteenth, a method for transmitting radio frequency signals is provided. This method modulates an RF signal into an optical signal, combines the modulated optical signal with other unmodulated optical signals, and transmits the combined signal through a fourth optical fiber. Finally, the RF signal modulated on the optical signal is demodulated at the output end of the fourth optical fiber. In other words, by treating the other unmodulated optical signals as interference signals and transmitting them together with the modulated RF signal through the optical fiber, the optical signal spectrum is broadened, the energy density of the incoming light is reduced, and the power of the optical signal incident on the optical fiber is increased, thereby improving the transmission performance and efficiency of the RF signal.

[0113] In a possible implementation of the fourteenth aspect, the wavelengths of the multiple optical signals that have not been electro-optically modulated are in a low dispersion band.

[0114] In a possible implementation of the fourteenth aspect, the wavelengths of the multiple optical signals that have not been electro-optically modulated are different.

[0115] In the fifteenth aspect, a network device is provided, which includes: the optical radio frequency transmission system provided by the first aspect or the fourth aspect, or the optical radio frequency transmission system in any possible implementation of the first aspect or the fourth aspect.

[0116] In the sixteenth aspect, a network device is provided, which includes: the communication device in the above-mentioned second aspect or any possible implementation of the second aspect, and the communication device in the above-mentioned third aspect or any possible implementation of the third aspect.

[0117] In the seventeenth aspect, a network device is provided, which includes: the optical radio frequency transmission system provided in the eighth aspect or the eleventh aspect, or the optical radio frequency transmission system in any possible implementation of the eighth aspect or the eleventh aspect.

[0118] In the eighteenth aspect, a network device is provided, which includes: the communication device in the above-mentioned ninth aspect or any possible implementation of the ninth aspect, and the communication device in the above-mentioned tenth aspect or any possible implementation of the tenth aspect.

[0119] The network device provided in the embodiment of the present application achieves the broadening of the incoming optical signal spectrum and reduces the energy density of the incoming optical fiber, thereby increasing the optical signal power incident on the optical fiber and improving the performance and transmission efficiency of the network device.

[0120] For example, the network device may include: a baseband unit and a remote radio frequency unit (radio frequency remote unit), the electro-optical modulation module can be set in the baseband unit in the base station, the optoelectronic demodulation module can be set in the remote radio frequency unit in the base station, and the optical fiber is used to connect the baseband unit and the remote radio frequency unit.

[0121] Exemplarily, one or more of an electro-optical modulation module, an optical signal generating module, a radio frequency signal generating module, an optical amplifier, an optical circulator, a reflected light power detection module, a feedback control unit, a first demultiplexer, a wavelength division multiplexer and a combiner can also be set on the baseband unit.

[0122] Exemplarily, a second wavelength division multiplexer and the like may also be provided in the remote radio frequency unit.

[0123] In the nineteenth aspect, a computer program product is provided, which includes a computer program, which, when executed by a processor, is used to execute the method in any possible implementation of the above aspects 5 to 7, or aspects 5 to 7.

[0124] In the twentieth aspect, a computer program product is provided, which includes a computer program, which, when executed by a processor, is used to execute the method in any possible implementation of the above aspects twelfth to fourteenth, or aspects twelfth to fourteenth.

[0125] In the twenty-first aspect, a computer-readable storage medium is provided, in which a computer program is stored. When the computer program is executed, it is used to execute the method in any possible implementation of the above aspects 5 to 7, or aspects 5 to 7.

[0126] In aspect 22, a computer-readable storage medium is provided, in which a computer program is stored. When the computer program is executed, it is used to execute the method in any possible implementation of aspects 12 to 14, or aspects 12 to 14 above.

[0127] In the twenty-third aspect, a chip is provided, which includes: a processor for calling and running a computer program from a memory, so that a communication device equipped with the chip executes the method in any possible implementation of the above fifth to seventh aspects, or the fifth to seventh aspects.

[0128] In the twenty-fourth aspect, a chip is provided, which includes: a processor for calling and running a computer program from a memory, so that a communication device equipped with the chip executes the method in any possible implementation of the above aspects 12 to 14, or aspects 12 to 14. BRIEF DESCRIPTION OF THE DRAWINGS

[0129] FIG1 is a schematic diagram of a RoF transmission system structure provided in an embodiment of the present application.

[0130] FIG2 is a schematic diagram of another example of a RoF transmission system structure provided in an embodiment of the present application.

[0131] FIG3 is a schematic diagram of another example of a RoF transmission system structure provided in an embodiment of the present application.

[0132] FIG4 is a schematic diagram of another example of a RoF transmission system structure provided in an embodiment of the present application.

[0133] FIG5 is a schematic diagram of another example of a RoF transmission system structure provided in an embodiment of the present application.

[0134] FIG6 is a schematic diagram of a single-channel (single-line) RoF transmission system structure provided in an embodiment of the present application.

[0135] FIG7 is a schematic diagram showing the numerical changes of the reflected light power and the output fiber optical power of a single-line control group 1 provided in an embodiment of the present application.

[0136] FIG8 is a schematic diagram showing the numerical changes of the reflected light power and the output fiber optical power of a four-line control group 1 provided in an embodiment of the present application.

[0137] FIG9 is a schematic diagram of the numerical changes of the reflected light power and the output fiber optical power of an eight-line control group 1 provided in an embodiment of the present application.

[0138] FIG10 is a schematic diagram showing the numerical changes of the reflected light power and the output fiber optical power of a single-line control group 2 provided in an embodiment of the present application.

[0139] FIG11 is a schematic diagram showing the numerical changes of the reflected light power and the output fiber optical power of a four-line control group 2 provided in an embodiment of the present application.

[0140] FIG12 is a schematic diagram of the numerical changes of the reflected light power and the output fiber optical power of an eight-line control group 2 provided in an embodiment of the present application.

[0141] FIG13 is a schematic diagram of another example of a RoF transmission system structure provided in an embodiment of the present application.

[0142] FIG14 is a schematic diagram of another example of a RoF transmission system structure provided in an embodiment of the present application.

[0143] Figure 15 is a schematic diagram of an example of a communication device structure provided in an embodiment of the present application.

[0144] Figure 16 is a schematic diagram of another example of a communication device structure provided in an embodiment of the present application.

[0145] Figure 17 is a schematic diagram of another example of a communication device structure provided in an embodiment of the present application.

[0146] Figure 18 is a schematic diagram of another example of a communication device structure provided in an embodiment of the present application.

[0147] Figure 19 is a schematic diagram of a network device structure provided in an embodiment of the present application. DETAILED DESCRIPTION

[0148] The technical solution in this application will be described below with reference to the accompanying drawings.

[0149] In the description of the embodiments of this application, unless otherwise specified, " / " represents or. For example, A / B can represent A or B. "And / or" in this article is simply a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of this application, "plurality" means two or more than two.

[0150] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this embodiment, unless otherwise specified, "plurality" means two or more.

[0151] The technical solution in this application will be described below with reference to the accompanying drawings.

[0152] In the description of the embodiments of this application, unless otherwise specified, " / " represents or. For example, A / B can represent A or B. "And / or" in this article is simply a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of this application, "plurality" means two or more than two.

[0153] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this embodiment, unless otherwise specified, "plurality" means two or more.

[0154] RoF, a candidate for the next generation of low-cost broadband wireless access, modulates RF signals onto optical carriers and transmits them over optical fiber links to achieve wireless access. This fully utilizes optical fiber bandwidth and uses optical fiber to transmit RF signals. Simply put, the baseband unit in a RoF base station modulates the RF signal onto an optical signal. The modulated optical signal is then transmitted over a complex optical fiber link. Upon reaching the remote unit in the base station, an optoelectronic demodulation module demodulates the optical signal to generate an RF signal, which is then transmitted through an antenna for user use. RoF technology meets the requirements for improving network transmission capacity, network interactivity, and flexibility.

[0155] However, the vast majority of RoF transmission systems currently in use use ordinary G.652E optical fiber for signal transmission. Due to the small effective cross-sectional area of ​​G.652E optical fiber, it is susceptible to the SBS effect when high-power optical signals are input into the fiber. This results in low optical signal power incident on the fiber, limiting the optical power transmitted through the fiber, and thus affecting the performance and transmission efficiency of the RoF transmission system. To address this issue, some currently use expensive, high-performance specialty optical fibers. However, the use of such specialty fibers is costly and cannot meet the long-distance, high-power transmission requirements of RoF transmission systems. Therefore, a solution is needed that, while considering the fiber's cost, increases the optical signal power incident on the fiber, reduces the impact of the SBS effect, and meets the long-distance, high-power transmission requirements of RoF transmission systems.

[0156] In view of this, the present application provides a RoF transmission system that modulates an RF signal onto multiple optical signals, transmits the modulated multiple optical signals in an optical fiber, and finally demodulates the RF signal modulated on the multiple optical signals at the output end of the optical fiber transmission. This achieves the goal of broadening the spectrum of the incoming optical signal, reducing the energy density of the incoming optical fiber, thereby increasing the power of the optical signal incident on the optical fiber, and improving the performance and transmission efficiency of the RoF transmission system.

[0157] First, the SBS effect is briefly described.

[0158] The basic phenomenon of the SBS effect is that energy transfer occurs between two optical signals that meet the phase matching condition and propagate in opposite directions. In essence, it is a nonlinear interaction between pump light, Stokes light, and acoustic waves in the medium. The SBS threshold power P SBS It can be determined by formula (1):

[0159]

[0160] In formula (1), g B is the peak SBS gain coefficient, L eff is the effective length of the optical fiber, K is the polarization factor, and its value is between 1 and 2. eff is the effective cross-sectional area of ​​the optical fiber.

[0161] The SBS threshold power is related to the energy density and linewidth of the optical signal incident on the fiber (i.e., incoming migration). The higher the optical energy density of the incoming fiber and the narrower the optical signal linewidth (i.e., the narrower the incoming migration signal spectrum), the lower the SBS threshold power. The primary impact of SBS on the system is channel energy loss caused by back reflections in the fiber.

[0162] In a RoF transmission system, the optical signal power incident on the optical fiber (i.e., the incoming optical power) is unlikely to exceed the SBS threshold power. Therefore, increasing the incoming optical power means increasing the SBS threshold power. In other words, in the embodiments of the present application, increasing the incoming optical power can also be understood as increasing the SBS threshold power.

[0163] FIG1 is a schematic diagram of a RoF transmission system structure provided in an embodiment of the present application. As shown in FIG1 , the system includes:

[0164] Electro-optical modulation module: The electro-optical modulation module is used to modulate the radio frequency signal onto multiple optical signals to obtain multiple modulated optical signals;

[0165] Optical fiber: Optical fiber is used to transmit multiple modulated optical signals;

[0166] Optoelectronic demodulation module: The optoelectronic demodulation module is used to demodulate multiple modulated optical signals output from the optical fiber and output RF signals.

[0167] Optionally, the optoelectronic demodulation module can transmit the demodulated RF signal to an analog RF circuit. Exemplarily, the analog RF circuit may include one or more of a filter, an amplifier, a mixer, an antenna, a power splitter, a combiner, and the like.

[0168] It should be understood that in the embodiment of the present application, multiple optical signals can be understood as the number of optical signals being greater than or equal to 2.

[0169] Optionally, in an embodiment of the present application, the wavelengths of the multiple optical signals may all be different, that is, the wavelengths of any two optical signals may be different; or, the wavelengths of the multiple optical signals may be partially the same and partially different. For example, among 10 optical signals, three of the optical signals may have the same wavelength, all λ1, and the other seven optical signals may have different wavelengths, for example, the other seven optical signals may have wavelengths of λ2 to λ8, respectively. Alternatively, the wavelengths of the multiple optical signals may all be the same. This embodiment of the present application is not limiting.

[0170] It should also be understood that in the embodiments of the present application, the aforementioned electro-optical modulation module, optical fiber, and optoelectronic demodulation module may be integrated or separately provided. In other words, the electro-optical modulation module, optical fiber, and optoelectronic demodulation module may or may not be physically separate, may be located in one place, or may be distributed across multiple network units. This is not a limitation of the embodiments of the present application.

[0171] For example, the electro-optical modulation module may be provided in a baseband unit (BBU) in a base station, the optoelectronic demodulation module may be provided in a remote radio unit (RRU) in the base station, and an optical fiber is used to connect the BBU and the RRU.

[0172] The RoF transmission system provided in this application uses an electro-optical modulation module to modulate an RF signal onto multiple optical signals. The modulated multiple optical signals are then transmitted through an optical fiber. Finally, an optoelectronic demodulation module is used at the output end of the optical fiber transmission to demodulate the RF signal modulated onto the multiple optical signals. This broadens the spectrum of the incoming optical signal, reduces the energy density of the incoming light, and thus increases the power of the optical signal incident on the optical fiber, thereby improving the performance and transmission efficiency of the RoF transmission system.

[0173] The RoF transmission system provided by this application will be described below with reference to specific examples.

[0174] FIG2 is a schematic diagram of another example of a RoF transmission system structure provided in an embodiment of the present application. As shown in FIG2 , the RoF transmission system includes:

[0175] Optical signal generating module: The optical signal generating module is used to generate multiple optical signals. In the following example, the wavelengths of the multiple optical signals generated by the optical signal generating module are all different. However, it should be understood that the wavelengths of the multiple optical signals generated by the optical signal generating module can also be some of the same and some of them different.

[0176] For example, the optical signal generation module can generate wavelengths of: λ1, λ2, λ3...λ m These are m optical signals of different wavelengths.

[0177] It should be understood that in the embodiment of the present application, λ1, λ2, λ3, ... λ m The wavelength difference between two adjacent optical signals of the m optical signals with different wavelengths can be the same, for example, the value of λ2-λ1, the value of λ3-λ2, ...λ m -λ m-1 The values ​​of can be the same, that is, the wavelengths of multiple optical signals are arranged in an increasing or decreasing arithmetic progression; or, the value of λ2-λ1, the value of λ3-λ2, ....λ m -λ m-1 Any two or more of the values ​​of may be different, that is, the difference between the wavelengths of two adjacent optical signals may also be different. This embodiment of the present application is not limited here.

[0178] RF signal generating module: RF signal generating module is used to generate RF signal. For example, the RF signal generated by the RF signal generating module is RF, and the frequency of the RF signal is f RF .

[0179] It is understood that in the embodiment of the present application, the RF signal generating module can generate one or more RF signals, and the frequencies corresponding to different RF signals (or different RF signals) can be different. For example, the RF signal generating module can generate: RF1, RF2...RF s These s RF signals, different RF signals correspond to f RF It can be different.

[0180] Electro-optical modulation module (or also called electro-optical modulation array): the output end of the optical signal generating module is connected to the input end of the electro-optical modulation module, the output end of the radio frequency signal generating module is connected to the input end of the electro-optical modulation module, the electro-optical modulation module receives the RF signal generated by the radio frequency signal generating module, and the multiple optical signals of different wavelengths generated by the optical signal generating module, and modulates the RF signal onto the multiple optical signals of different wavelengths to obtain multiple modulated optical signals. It can be understood that in this implementation, the radio frequency signal generating module can generate one RF signal. For example, the electro-optical modulation module can modulate one RF signal to λ1, λ2, λ3….λ m From the m optical signals of different wavelengths, m modulated optical signals are obtained, where m is an integer greater than 1.

[0181] An optical amplifier, whose input is connected to the output of the electro-optical modulation module, is used to receive the multiple modulated optical signals output by the electro-optical modulation module and amplify the power of the multiple modulated optical signals. For example, the optical amplifier can amplify the power of the multiple modulated optical signals to the watt level. After power amplification, the multiple modulated optical signals can be transmitted through the optical fiber.

[0182] In the embodiment of the present application, since one RF signal (for example, RF1) is simultaneously used to modulate m optical signals (for example, λ1, λ2, λ3, ... λ m ), the m modulated optical signals obtained are transmitted in the optical fiber, which is equivalent to broadening the spectrum of the incoming optical signal, which is equivalent to reducing the optical power density in the optical fiber core by m times. The reduction of the optical power density by m times is equivalent to expanding the effective cross-sectional area of ​​the optical fiber by m times, that is, A eff Convert to mA eff According to formula (1), A eff Convert to mA eff , then P SBS becomes mP SBS , that is, the SBS threshold power is increased by m times, so the SBS threshold power is increased, that is, the incoming optical power is increased.

[0183] Optical fiber: The input end of the optical fiber is connected to the output end of the optical amplifier. The optical fiber is used to transmit multiple modulated optical signals amplified by the optical amplifier. In the embodiments of the present application, the optical fiber can be a commonly used optical fiber, such as G.652E optical fiber, G.654E optical fiber, etc. The specific type of optical fiber used in the embodiments of the present application is not limited.

[0184] Optoelectronic demodulation module (also called optoelectronic demodulation array): The input end of the optoelectronic demodulation module is connected to the output end of the optical fiber. The optoelectronic demodulation module is used to receive multiple modulated optical signals transmitted by the optical fiber and demodulate and output RF signals from these multiple modulated optical signals. For example, RF1 can be demodulated from multiple modulated optical signals and input into the analog RF circuit for processing.

[0185] For example, the optical signal generation module can generate four optical signals with wavelengths of λ1 = 1549 nm, λ2 = 1550 nm, λ3 = 1551 nm, and λ4 = 1552 nm. The radio frequency signal generation module generates an RF signal, for example, with a frequency of 3.5 GHz, a power of 0 dBm, and a sinusoidal RF wave shape. In this case, the electro-optical modulation module can include four electro-optical intensity modulators, each with a half-wave voltage of 3.5 V, an extinction ratio of 35 dB, and operating at the quadrature point. The optical amplifier operates in automatic power control mode with a fixed output optical power of 1 W. The photoelectric demodulation module includes four photodetectors, each with a responsivity of 0.7 A / W.

[0186] The RoF transmission system provided herein modulates an RF signal onto multiple optical signals to generate multiple modulated optical signals. The power of these multiple modulated optical signals is amplified by an optical amplifier before being transmitted through an optical fiber. Finally, the RF signal modulated onto the multiple optical signals is demodulated at the output end of the optical fiber transmission. This broadens the spectrum of the incoming optical signal, reduces the energy density of the incoming light, and increases the power of the optical signal incident on the fiber. This increases the SBS power threshold, thereby improving the performance and transmission efficiency of the RoF transmission system. Furthermore, the power amplification provided by the optical amplifier can improve the transmission efficiency of the multiple modulated optical signals in the optical fiber.

[0187] Optionally, as a possible implementation, in order to increase the flexibility of the RoF transmission system, based on the structure shown in FIG2 , as shown in FIG3 , the RoF transmission system provided in the embodiment of the present application may further include:

[0188] Optical circulator, reflected light power detection module and feedback control unit.

[0189] The first port of the optical circulator is connected to the output of the optical amplifier, and the second port of the optical circulator is connected to the input of the optical fiber. Multiple modulated optical signals output by the optical amplifier are transmitted to the optical circulator through the first port of the optical circulator, and then transmitted to the optical fiber through the second port of the optical circulator for further transmission within the optical fiber. The third port of the optical circulator is connected to the input of a reflected light power detection module, the output of which is connected to the input of a feedback control unit, and the output of the feedback control unit is connected to the optical signal generation module.

[0190] Since the impact of SBS on the system is mainly the loss of channel energy caused by the back reflection of light in the optical fiber, the reflected light power detection module can be used to detect the reflected light power of multiple modulated optical signals transmitted in the optical fiber. When it is detected that the reflected light power is greater than or equal to a preset threshold (for example, a first threshold), a signal (for example, a first signal) is sent to the feedback control unit. The feedback control unit is used to generate a second signal (for example, a feedback level signal) under the action of the first signal and transmit it to the optical signal generation module. The optical signal generation module adjusts the wavelength and / or number of the multiple optical signals generated according to the feedback level signal. For example, the number of optical signals generated by the optical signal generation module and / or the wavelength difference between two adjacent optical signals in different optical signals, that is, the wavelength interval, etc. are adjusted.

[0191] Exemplarily, the preset threshold (first threshold) may be a preset or predefined SBS threshold power.

[0192] When the reflected light power detection module detects that the reflected light power is less than a preset threshold, it proves that the power of the optical signal incident on the optical fiber is less than the SBS threshold power, and the RoF transmission system can operate normally. The wavelengths and / or number of the multiple optical signals generated by the previous optical signal generation module can be maintained, and the multiple optical signals generated by the optical signal generation module can be used to modulate the RF signal, and the obtained multiple modulated optical signals can be transmitted in the optical fiber.

[0193] By providing a reflected light power detection module and a feedback control unit, the flexibility of the RoF transmission system can be improved. When the power of the optical signal incident on the optical fiber is greater than or equal to the preset SBS threshold power, the quantity and / or wavelength of the optical signal generated by the optical signal generation module are promptly adjusted to ensure that the power of the optical signal incident on the optical fiber is less than the SBS threshold power. This can improve the stability and performance of the RoF transmission system while increasing the power of the optical signal incident on the optical fiber.

[0194] Alternatively, as a possible implementation, the RoF transmission system provided in this application can be combined with WDM. WDM can be used to increase the number of channels, that is, to increase the number of transmitted RF signals, enabling simultaneous transmission of multiple RF signals, thereby improving the transmission efficiency and performance of the RoF transmission system. This will be illustrated below with reference to specific examples.

[0195] Based on the structure shown in FIG3 , as shown in FIG4 , the RoF transmission system may further include:

[0196] A first demultiplexer, a wavelength division multiplexer, and a second demultiplexer. As shown in FIG4 , the electro-optical modulation module may include n electro-optical modulation submodules, and the photoelectric demodulation module may include n photoelectric demodulation submodules. Optionally, the photoelectric demodulation submodule may also be referred to as a photoelectric detection submodule, i.e., the photoelectric demodulation module may also include n photoelectric detection submodules. The value of n may be a positive integer. For example, the value of n may be 4, 5, etc., and this is not limited in the present embodiment.

[0197] As shown in FIG4 , the input end of the first demultiplexer is connected to the output end of the optical signal generating module, and is used to decompose the multiple (for example, M, where M is an integer greater than 1) optical signals generated by the optical signal generating module into n channels. That is, the first demultiplexer is used to divide the multiple optical signals into n groups or n parts. Each channel (or each group) corresponds to (or includes) multiple optical signals. In other words, the i-th channel includes K i optical signals, where i is an integer greater than or equal to 1 and less than or equal to n. The number of optical signals corresponding to each channel can be the same or different. Among the multiple optical signals on each channel, the difference between the wavelengths of two adjacent optical signals can be the same or different. Among the multiple optical signals on each channel, the wavelengths of the multiple optical signals can all be different, or the wavelengths of the multiple optical signals can be partially the same and partially different.

[0198] As shown in FIG4 , the RF signal generating module can generate n RF signals, such as RF1, RF2…RF n The number (or number of channels) of the n-channel RF signals generated by the RF signal generating module is the same as the number of channels into which the first demultiplexer decomposes the multiple optical signals, both of which are n. The frequencies f corresponding to different RF signals are RF It can be different.

[0199] As shown in Figure 4, the output end of the first de-wavelength division multiplexer is connected to the input end of the optoelectronic demodulation module, and the output end of the RF signal generation module is connected to the input end of the optoelectronic demodulation module. Since the first de-wavelength division multiplexer divides multiple optical signals of different wavelengths into n channels, and the RF signal generation module generates n RF signals, the electro-optical modulation module includes n electro-optical modulation sub-modules. Therefore, an electro-optical modulation sub-module receives multiple optical signals and one RF signal on a channel, and modulates one RF signal onto multiple optical signals corresponding to one channel to obtain multiple modulated optical signals. In other words, the i-th electro-optical modulation sub-module is used to modulate the i-th RF signal onto the K signals included on the i-th channel. i On the optical signal, we get K i A modulated optical signal.

[0200] For example, as shown in FIG4 , the optical signals of different wavelengths corresponding to channel 1 are: 11 ,λ 12 ,λ 13 ….λ 1a The electro-optical modulation submodule 1 receives the optical signals of different wavelengths and the frequency f corresponding to the channel 1. RF1 The RF signal is modulated to λ 11 ,λ 12 ,λ 13 ….λ 1a The optical signal after electro-optical modulation on channel 1 is obtained. in, The letter m in the upper right corner indicates that the optical signal is electro-optically modulated. 11 ,λ 12 ,λ 13 ….λ 1a It represents the wavelength of the optical signal without electro-optical modulation.

[0201] The optical signals of different wavelengths corresponding to channel 2 are: 21 ,λ 22 ,λ 23 ….λ 2b The electro-optical modulation submodule 2 receives the optical signals of different wavelengths corresponding to the channel 2 and the frequency f RF2 The RF signal is modulated to λ 21 ,λ 22 ,λ 23 ….λ 2b The optical signal after electro-optical modulation on channel 2 is obtained. λ 21 ,λ 22 ,λ 23 ….λ 2bIt represents the wavelength of the optical signal without electro-optical modulation.

[0202] And so on:

[0203] The optical signals of different wavelengths corresponding to channel n are: n1 ,λ n2 ,λ n3 ….λ nm The electro-optical modulation submodule n receives the optical signals of different wavelengths corresponding to the channel n and the frequency f RFn The RF signal is modulated to λ n1 ,λ n2 ,λ n3 ….λ nm The optical signal after electro-optical modulation on channel n is obtained. λ n1 ,λ n2 ,λ n3 ….λ nm It represents the wavelength of the optical signal without electro-optical modulation.

[0204] Optionally, the values ​​of a, b, ..., m may be the same or different, that is, the number of optical signals corresponding to each channel may be the same or different.

[0205] Optional, λ i2 -λ i1 The value of λ i3 -λ i2 The value of λ i4 -λ i3 The values ​​of , .... can be the same or different, and the value of i can be: 1, 2, ..., n. That is, for each channel, the difference between the wavelengths of two adjacent optical signals can be the same or different.

[0206] In summary, the electro-optical modulation module includes n electro-optical modulation sub-modules and can output Q modulated optical signals, where Q is an integer greater than or equal to 1 and less than or equal to M.

[0207] As shown in Figure 4, the output of the electro-optical modulation module is connected to the input of the wavelength division multiplexer, which in turn is connected to the input of the optical amplifier. In the electro-optical modulation module, each electro-optical modulation submodule inputs the modulated optical signal into the wavelength division multiplexer. Specifically, the electro-optical modulation module inputs Q modulated optical signals into the wavelength division multiplexer, which then combines the Q modulated optical signals into one optical signal and transmits it to the optical amplifier.

[0208] The optical amplifier amplifies the power of the combined optical signal and then injects it into the optical fiber through the optical circulator, thereby achieving transmission in the optical fiber.

[0209] As shown in Figure 4, the output end of the optical fiber is connected to the input end of the second wavelength division multiplexer. The second wavelength division multiplexer is used to decompose one optical signal output by the optical fiber after electro-optical modulation into n optical signals, that is, to decompose the Q modulated optical signals transmitted in the optical fiber into n optical signals (n groups or n channels). The optical signal on each channel includes multiple modulated optical signals, that is, the optical signal on each channel (or each optical signal) includes multiple modulated optical signals with different wavelengths.

[0210] For example, as shown in FIG4 , the multiple modulated optical signals output from channel 1 of the second demultiplexer are: Indicates that the frequency is f RF1 The RF signal is modulated to a wavelength of λ 11 ,λ 12 ,λ 13 ….λ 1a After the optical signal is modulated, multiple optical signals with different wavelengths are obtained.

[0211] The multiple modulated optical signals output from channel 2 of the second demultiplexer are: in, Indicates that the frequency is f RF2 The RF signal is modulated to a wavelength of λ 21 ,λ 22 ,λ 23 ….λ 2b After the optical signal is modulated, multiple optical signals with different wavelengths are obtained.

[0212] And so on:

[0213] The multiple modulated optical signals output on channel n of the second demultiplexer are: in, Indicates that the frequency is f RFn The RF signal is modulated to a wavelength of λ n1 ,λ n2 ,λ n3 ….λ nm After the optical signal is modulated, multiple optical signals with different wavelengths are obtained.

[0214] In summary, the second demultiplexer can output n optical signals, each of which includes multiple optical signals with different wavelengths. In other words, the second demultiplexer is used to decompose the optical signal output by the optical fiber into n optical signals, wherein the i-th optical signal includes K i A modulated optical signal.

[0215] As shown in Figure 4 , the input end of the optoelectronic demodulation module is connected to the output end of the second wavelength division multiplexer. Since the optoelectronic demodulation module includes n optoelectronic demodulation submodules, one optoelectronic demodulation submodule in the optoelectronic demodulation module demodulates a radio frequency signal from an optical signal output by the second wavelength division multiplexer. In other words, the i-th optoelectronic demodulation submodule in the optoelectronic demodulation module is used to demodulate the i-th radio frequency signal from the i-th optical signal output by the second wavelength division multiplexer, and the optoelectronic demodulation module is used to output n radio frequency signals.

[0216] For example, as shown in FIG4 , the optoelectronic demodulation submodule 1 outputs the signal from the channel 1 of the second demultiplexer. The demodulated frequency is f RF1 The radio frequency signal, the optoelectronic demodulation module 2 outputs from the channel 2 of the second demultiplexer The demodulated frequency is f RF2 The RF signal of the second wavelength division multiplexer is output by the optoelectronic demodulation module n from the channel n of the second wavelength division multiplexer. The demodulated frequency is f RFn RF signal.

[0217] In this way, the optoelectronic demodulation module can output n-channel RF signals with frequencies of f RF1 、f RF2 …f RFn , thereby outputting these n RF signals.

[0218] The RoF transmission system shown in Figure 4 modulates an RF signal onto multiple optical signals of different wavelengths and transmits these modulated optical signals through the optical fiber. This broadens the spectrum of the incoming optical signal and reduces the energy density of the incoming light, thereby increasing the power of the optical signal incident on the fiber and improving the transmission efficiency of the RoF transmission system. Furthermore, by combining the RoF transmission system with WDM and adding demultiplexers and wavelength division multiplexers, the multiple optical signals are decomposed into N channels. The multiple optical signals on a single channel are used to modulate a single RF signal. By increasing the number of channels using WDM, multiple RF signals can be transmitted simultaneously. This means that the RoF transmission system implements MIMO transmission, improving the performance of the RoF transmission system.

[0219] It is understandable that the structure shown in FIG4 is an improvement on the structure shown in FIG3. In other possible implementations of the present application, a first de-WDM, a WDM, and a second de-WDM may be added to the structure shown in FIG2 or FIG1. ​​In other words, the structure shown in FIG4 may not include an optical circulator, a reflected light power detection module, and a feedback control unit. Alternatively, the structure shown in FIG4 may not include: an optical circulator, a reflected light power detection module, a feedback control unit, an optical amplifier, a radio frequency signal generation module, and an optical signal generation module.

[0220] In some possible implementations of the present application, the optical signal generation module in any of the above-described implementations may have various implementations depending on the principle of generating the optical signal. For example, the optical signal generation module may include any of: an ultra-wideband optical frequency comb generation module based on a mode-locked laser, an optical signal generation module based on fiber nonlinear effects, an optical signal generation module based on an optoelectronic oscillator, an optical signal generation module based on a microring resonator, and an optical signal generation module based on an electro-optical modulator. These are described in detail below.

[0221] In one possible implementation, the optical signal generating module may generate an optical signal based on a mode-locked laser. Based on the mode-locked laser, a phase-locked loop circuit is used to lock the optical frequency to a reference frequency through feedback control of the pump current, thereby directly generating an optical signal with a frequency interval equal to the repetition frequency of the mode-locked laser. In other words, when the optical signal is generated based on the mode-locked laser, the difference between the wavelengths of two adjacent optical signals of different wavelengths is the same. For example, in the example shown in FIG2 or FIG3, if the optical signal generating module generates an optical signal based on a mode-locked laser, the value of λ2-λ1, the value of λ3-λ2, ....λ m -λ m-1 For example, in the example shown in FIG4 , since the first demultiplexer can divide multiple optical signals of different wavelengths into n channels, for multiple optical signals on each channel, the difference between the wavelengths of two adjacent optical signals is the same. For example, for channel 1, λ 12 -λ 11 The value of λ 13 -λ 12 The value of λ 14 -λ 13 The value of , ... 1a -λ 1a-1The values ​​of are the same. In the embodiments of the present application, if the optical signal generation module generates optical signals based on a mode-locked laser, the optical signal generation module can also be called an ultra-wideband optical frequency comb generation module, which is used to generate multiple optical signals with equal intervals (e.g., equal wavelength intervals, equal frequency intervals, or equal time intervals). The ultra-wideband optical frequency comb generation module based on a fiber mode-locked laser has the advantages of small size, light weight, low cost, and easy maintenance.

[0222] In another possible implementation, the optical signal generation module can generate multiple optical signals based on the nonlinear effect of optical fibers. For example, parametric frequency conversion processes in nonlinear optics (such as four-wave mixing and self-phase modulation) can be used to obtain an optical frequency comb with mode-locked characteristics. In other words, if the optical signal generation module generates multiple optical signals based on the nonlinear effect of optical fibers, then the optical signal generation module can also be called an ultra-wideband optical frequency comb generation module, which is used to generate multiple optical signals with equal intervals (e.g., equal wavelength intervals, equal time intervals, or equal frequency intervals). The ultra-wideband optical frequency comb generation module based on nonlinear generation has a wider bandwidth and can generate a larger number of comb teeth.

[0223] In another possible implementation, the optical signal generation module can generate multiple optical signals using an optical frequency comb method based on an optoelectronic oscillator. Using this method, the optical signal generation module has high spectral purity, and the frequency of the generated optical signal can reach hundreds of gigahertz (GHz) with good flatness.

[0224] In another possible implementation, the optical signal generation module can be based on a microring resonator. By utilizing the low loss and small mode area characteristics of the microring resonator, the photon density is enhanced, and the pump light coupled into the microring resonator can produce nonlinear effects at a lower threshold. Therefore, the parametric frequency conversion caused by the optical Kerr effect allows the pump light frequency to be extended to other resonant modes of the microring resonator, resulting in a Kerr optical frequency comb. Compared with traditional optical frequency combs based on mode-locked lasers, microcavity Kerr optical frequency combs have the advantages of small size, light weight, low power consumption, and high integration. They also break through the physical cavity length limitations of conventional lasers, and their comb tooth spacing can cover a range from 1 GHz to several THz.

[0225] In another possible implementation, the optical signal generation module can be based on an electro-optical modulator. By selecting the system architecture and the voltage applied to the electro-optical modulator based on the electro-optic effect, the energy originally concentrated in the optical carrier is transferred to multiple optical sidebands near the center wavelength, thereby generating multiple optical signal outputs. This implementation is simple and controllable, and can produce multiple optical signals with high flatness, wide bandwidth, and high side mode suppression ratio. The frequency spacing of the multiple optical signals can be adjusted by simply changing the frequency of the RF drive signal, giving the electro-optical modulator-based optical signal generation module a certain degree of flexibility. Both the center frequency and the frequency spacing are typically adjustable.

[0226] It should be understood that in addition to using the above-mentioned methods to implement the optical signal generating module, in other implementation methods of the present application, other methods can also be used to implement the optical signal generating module, as long as the optical signal generating module can generate multiple optical signals. The embodiments of the present application are not limited here.

[0227] The following will take the structure shown in Figure 5 as an example to illustrate the RoF transmission system provided by this application, taking the optical signal generating module as an ultra-wideband optical frequency comb generating module and combining the RoF transmission system with WDM as an example.

[0228] As shown in FIG5 , the optical frequency comb signal E generated by the ultra-wideband optical frequency comb generation module OFC (t) can be determined by formula (2):

[0229]

[0230] In formula (2), t represents time, E ij represents the amplitude of the ijth comb signal (i.e., the ijth optical signal), ω ij represents the angular frequency of the ijth comb signal, where represents the wavelength of the ijth comb signal, c represents the speed of light, Indicates the frequency interval between two adjacent optical comb teeth.

[0231] The optical frequency comb signal E generated by the ultra-wideband optical frequency comb generation module OFC (t) After being decomposed by the first wavelength division multiplexer, it is divided into n channels (or can also be called n optical frequency combs).

[0232] The optical frequency comb signal E output by the first demultiplexer DWDM1 (t) can be determined by formula (3):

[0233]

[0234] In formula (3), E OFCq(t) represents the optical frequency comb signal output by the qth output channel of the first demultiplexer, where the value of q is 1, 2…n. It can be seen that each output channel (or each optical frequency comb) of the first de-Wavelength Division Multiplexer includes m optical frequency comb signals of different wavelengths. It is understood that in other embodiments of the present application, different output channels of the first de-Wavelength Division Multiplexer may output different numbers of optical frequency comb signals.

[0235] For example, as shown in FIG5 , the optical signals of different wavelengths corresponding to the output channel 1 of the first demultiplexer are: 11 ,λ 12 ,λ 13 ….λ 1m , the optical signals of different wavelengths corresponding to the output channel 2 of the first demultiplexer are: 21 ,λ 22 ,λ 23 ….λ 2m , the optical signals of different wavelengths corresponding to the output channel n of the first demultiplexer are: n1 ,λ n2 ,λ n3 ….λ nm .

[0236] As shown in Figure 5, the RF signal generation module generates n RF signals, and the electro-optical modulation module includes n electro-optical modulation sub-modules. Therefore, one electro-optical modulation sub-module receives an output channel of the first de-wavelength division multiplexer corresponding to multiple optical signals of different wavelengths and one RF signal, and modulates the one RF signal onto one channel corresponding to multiple optical signals of different wavelengths to obtain multiple modulated optical signals.

[0237] For example, as shown in FIG5 , the optical signals of different wavelengths corresponding to the output channel 1 of the first demultiplexer are: 11 ,λ 12 ,λ 13 ….λ 1m , the electro-optical modulation submodule 1 receives the corresponding multiple optical signals of different wavelengths λ on the output channel 1 11 ,λ 12 ,λ 13 ….λ 1m and frequency f RF1 The RF signal is modulated to λ 11 ,λ 12 ,λ 13 ….λ 1m The optical signal after electro-optical modulation on channel 1 is obtained.

[0238] The optical signals of different wavelengths corresponding to the output channel 2 of the first demultiplexer are: 21 ,λ 22 ,λ 23 ….λ 2m , the electro-optical modulation submodule 2 receives the corresponding multiple optical signals of different wavelengths λ on the output channel 2 21 ,λ 22 ,λ 23 ….λ 2m and frequency f RF2 The RF signal is modulated to λ 21 ,λ 22 ,λ 23 ….λ 2m The optical signal after electro-optical modulation on channel 2 is obtained.

[0239] The optical signals of different wavelengths corresponding to the output channel n of the first demultiplexer are: n1 ,λ n2 ,λ n3 ….λ nm The electro-optical modulation submodule 2 receives the optical signals λ of different wavelengths corresponding to the output channel n. n1 ,λ n2 ,λ n3 ….λ nm and frequency f RFn The RF signal is modulated to λ n1 ,λ n2 ,λ n3 ….λ nm The optical signal after electro-optical modulation on channel n is obtained.

[0240] In other words, the n optical frequency combs output by the first demultiplexer are input to the electro-optical modulation module. Each electro-optical modulation submodule in the electro-optical modulation module modulates one RF signal onto the m optical frequency comb signals of different wavelengths included in an output channel (or an optical frequency comb), thereby obtaining m modulated optical signals. For example, the number of modulated optical signals obtained by the electro-optical modulation module can be m × n.

[0241] The modulated optical signal E output by the n electro-optical modulation submodules included in the electro-optical modulation module EO (t) can be determined by formula (4):

[0242]

[0243] In formula (4), EEOq (t) represents the modulated optical signal output by the qth electro-optical modulation submodule, and the value of q is 1, 2...n. H(ω RFq ) represents the transfer function corresponding to the qth electro-optical modulation submodule, RFq represents the qth radio frequency signal, ω RFq represents the angular frequency of the RF signal transmitted to the qth electro-optical modulation sub-module.

[0244] The electro-optical modulation module modulates the output of multiple (or multi-channel) modulated optical signals E EO (t) Input to the wavelength division multiplexer.

[0245] The wavelength division multiplexer combines the multiple modulated optical signals output by the electro-optical modulation module into one optical signal and transmits it to the optical amplifier.

[0246] The optical amplifier amplifies the power of the combined optical signal and then injects it into the optical fiber through the optical circulator, thereby achieving transmission in the optical fiber.

[0247] As shown in FIG5 , the output end of the optical fiber is connected to the input end of a second wavelength division multiplexer. The second wavelength division multiplexer is used to decompose one modulated optical signal output by the optical fiber into n optical signals. That is, the optical signal transmitted in the optical fiber after electro-optical modulation is decomposed into n optical signals (n groups or n channels). The optical signal on each channel is obtained by modulating one radio frequency signal into multiple optical signals of different wavelengths. That is, the optical signal on each channel (or each optical signal) includes multiple modulated optical signals.

[0248] For example, as shown in FIG5 , the optical signals output on channel 1 of the second demultiplexer are: Indicates that the frequency is f RF1 The RF signal to the wavelength λ 11 ,λ 12 ,λ 13 ….λ 1m The optical signal is used to obtain multiple optical signals with different wavelengths.

[0249] The optical signals output on channel 2 of the second demultiplexer are: in, Indicates that the frequency is f RF2 The RF signal is modulated to a wavelength of λ 21 ,λ 22 ,λ 23 ….λ 2m After the optical signal is transmitted, multiple optical signals with different wavelengths are obtained.

[0250] And so on:

[0251] The optical signals output on channel n of the second demultiplexer are: in, Indicates that the frequency is f RFn The RF signal is modulated to a wavelength of λ n1 ,λ n2 , λ n3 ….λ nm After the optical signal is transmitted, multiple optical signals with different wavelengths are obtained.

[0252] In summary, as shown in Figure 5 , the second demultiplexer can output n optical signals, each of which includes multiple optical signals with different wavelengths after electro-optical modulation. In other words, the second demultiplexer is used to decompose the optical signal output by the optical fiber into n optical signals, each of which includes m optical signals with different wavelengths after electro-optical modulation.

[0253] In the structure shown in Figure 5, one RF signal is modulated onto m optical signals and then transmitted in the optical fiber, which is equivalent to broadening the spectrum of the incoming optical signal, which is equivalent to reducing the optical power density in the optical fiber core by m times. The reduction of the optical power density by m times is equivalent to expanding the effective cross-sectional area of ​​the optical fiber by m times, that is, A eff Convert to mA eff According to formula (1), A eff Convert to mA eff , then P SBS becomes mP SBS , that is, the SBS threshold power is increased by m times, so the SBS threshold power is increased, that is, the incoming optical power is increased.

[0254] For the single-channel RoF transmission system and the m-channel RoF transmission system shown in Figure 5, the single-channel RoF transmission system can be understood as modulating one RF signal onto one (or one) optical signal and then transmitting it in the optical fiber. eff Under the same and same incoming optical power, after the influence of SBS effect, the output optical power of the RoF transmission system with m channels shown in Figure 5 will increase by α(m) times compared with the single-channel RoF transmission system. Then the output signal E of the second demultiplexer will be DWDM2 (t) can be determined by formula (5):

[0255] E DWDM2 (t)=α(m)G OA E EO (t) (5)

[0256] In formula (5), G OA Indicates the amplification gain of the optical amplifier, E EO (t) represents the multiple modulated optical signals E output by the electro-optical modulation moduleEO (t), E EO (t) can be determined by formula (4).

[0257] As shown in FIG5 , the second demultiplexer can output n optical signals (or optical signals on n channels), each optical signal (or optical signal on each channel) including multiple optical signals with different wavelengths after electro-optical modulation.

[0258] As shown in FIG5 , the input end of the optoelectronic demodulation module is connected to the output end of the second de-WDM. The optoelectronic demodulation module includes n optoelectronic demodulation submodules. Therefore, one optoelectronic demodulation submodule in the optoelectronic demodulation module is used to demodulate an RF signal from an optical signal.

[0259] For example, as shown in FIG5 , the optoelectronic demodulation submodule 1 outputs the signal from the channel 1 of the second demultiplexer. The demodulated frequency is f RF1 The radio frequency signal, the optoelectronic demodulation module 2 outputs from the channel 2 of the second demultiplexer The demodulated frequency is f RF2 The RF signal of the second wavelength division multiplexer is output by the optoelectronic demodulation module n from the channel n of the second wavelength division multiplexer. The demodulated frequency is f RFn RF signal.

[0260] In this way, the optoelectronic demodulation module can output n-channel RF signals with frequencies of f RF1 、f RF2 …f RFn , thereby outputting these n RF signals, for example, inputting them into an analog RF circuit.

[0261] The n-channel RF signals finally recovered by the optoelectronic demodulation module can be determined by formula (6):

[0262]

[0263] In formula (6), ∝ means proportional, i RFq (t) represents the current or voltage of the recovered q-th RF signal, and the value of q is 1, 2…n, R(ω RFq ) represents the frequency response of the qth optoelectronic demodulation submodule.

[0264] Furthermore, it can be seen from formula (6) that after combining the RoF transmission system provided by the present application with the WDM system, the recovered RF signal power is improved by m compared to the single-channel RoF transmission system. 2 ×α 2 (m) times. This improves the RF signal transmission efficiency.

[0265] The RoF transmission system provided in this application modulates an RF signal onto multiple optical signals, transmits the resulting multiple modulated optical signals through an optical fiber, and ultimately demodulates the RF signal modulated onto the multiple optical signals at the output end of the optical fiber transmission. Because the transmission of multiple optical signals (i.e., multiple modulated optical signals) through an optical fiber causes fiber dispersion, the multiple electro-optically modulated optical signals may cancel each other out upon reception, resulting in lower power in the RF signal recovered from the multiple modulated optical signals.

[0266] For example, in the structure shown in FIG5 , the wavelengths output from channel 1 of the second demultiplexer are The modulated optical signal will be affected by the fiber dispersion during the transmission process in the optical fiber, and may cancel each other out when received, resulting in The power of the demodulated RF signal is low, which affects the power of RF signal transmission.

[0267] In order to solve the problem of fiber dispersion, as a possible implementation method: Assume that: for multiple optical signals of different wavelengths on any channel before electro-optical modulation, for example, λ1, λ2, λ3...λ shown in Figure 2 or Figure 3 m , λ shown in Figure 4 11 ,λ 12 ,λ 13 ….λ 1a , or λ shown in Figure 5 11 ,λ 12 ,λ 13 ….λ 1m Assume that the wavelength interval between two adjacent optical signals is Δλ. For example, in the example shown in FIG2 or FIG3, the value of λ2-λ1 can be Δλ, the value of λ3-λ2 can be Δλ, .... or, λ m -λ m-1 The value of can be Δλ; in the example of Figure 4, λ 12 -λ 11 The value of can be Δλ, λ 13 -λ 12 The value of can be Δλ, .... or λ 1a -λ 1a-1 The value of can be Δλ; in the example of Figure 5, λ 12 -λ 11 The value of can be Δλ, λ 13 -λ 12 The value of can be Δλ, .... or λ 1m -λ 1m-1 The value of can be Δλ, then the time delay Δτ between two adjacent optical signals can be determined by formula (7):

[0268] Δτ=D(λ)·L·Δλ ​​(7)

[0269] In formula (7), D(λ) represents the fiber dispersion coefficient when an optical signal with a wavelength of λ is transmitted in an optical fiber. When there are multiple optical signals transmitted in the optical fiber, D(λ) represents the fiber dispersion coefficient when these multiple optical signals are transmitted in the optical fiber. The value of D(λ) is related to the wavelength of the optical signal transmitted in the optical fiber, the type of optical fiber, etc. L represents the length of the optical fiber, and Δλ represents the wavelength interval between two adjacent optical signals. Then, when Δτ satisfies the following formula (8), the power of the RF signal output by any optoelectronic demodulation submodule in the optoelectronic demodulation module (if the optoelectronic demodulation module includes only one optoelectronic demodulation submodule, such as shown in Figures 2 and 3, it is the output of the optoelectronic demodulation module) can be increased, which can reduce the influence of optical fiber dispersion and improve the power of the RF signal recovered from the multiple modulated optical signals.

[0270]

[0271] In formula (8), n is a positive integer, T i represents the period of the RF signal modulated into multiple optical signals of different wavelengths, f RFi The frequency of the RF signal modulated into the plurality of optical signals having different wavelengths is indicated.

[0272] For example, for the examples shown in FIG2 and FIG3, the wavelengths of the multiple optical signals are: λ1, λ2, λ3 ....λ m , T i is the period of RF, f RFi f RF .

[0273] For another example, with respect to the example shown in FIG4 , the wavelengths of the multiple optical signals may be: λ 11 ,λ 12 ,λ 13 ….λ 1a , then the corresponding T i is the period of RF1, f RFi f RF1 Alternatively, the wavelengths of the multiple optical signals may be: 21 ,λ 22 ,λ 23 ….λ 2b , then the corresponding T i is the period of RF2, f RFi f RF2 Alternatively, the wavelengths of the multiple optical signals may be: n1 ,λ n2 ,λ n3 ….λnm , then the corresponding T i For RF n The period, f RFi f RFn .

[0274] For another example, with respect to the example shown in FIG5 , the wavelengths of the multiple optical signals may be: λ 11 ,λ 12 ,λ 13 ….λ 1m , then the corresponding T i is the period of RF1, f RFi f RF1 Alternatively, the wavelengths of the multiple optical signals may be: 21 ,λ 22 ,λ 23 ….λ 2m , then the corresponding T i is the period of RF2, f RFi f RF2 Alternatively, the wavelengths of the multiple optical signals may be: n1 ,λ n2 ,λ n3 ….λ nm , then the corresponding T i For RF n The period, f RFi f RFn .

[0275] According to formula (7) and formula (8), it can be determined that Δλ needs to satisfy the following formula (9):

[0276]

[0277] In formula (9), the value of n is a positive integer. According to formula (9), when the wavelength interval between two adjacent optical signals is reasonably adjusted, the power of the RF signal output by any optoelectronic demodulation submodule in the optoelectronic demodulation module (if the optoelectronic demodulation module includes only one optoelectronic demodulation submodule, for example, as shown in Figures 2 and 3, the power of the RF signal output by the optoelectronic demodulation module) can be increased, thereby reducing the influence of optical fiber dispersion and improving the power of the RF signal recovered from multiple optical signals of different wavelengths.

[0278] For example, according to formula (9), for the example shown in FIG2 or FIG3, the value of λ2-λ1, the value of λ3-λ2, ....λ m -λ m-1 The values ​​are set to That is, the value of λ2-λ1, the value of λ3-λ2, ....λ m -λ m-1Alternatively, the value of λ2-λ1 can be set to Set the value of λ3-λ2 to Set the value of λ4-λ3 to λ m -λ m-1 The value of That is, the value of λ2-λ1, the value of λ3-λ2, ....λ m -λ m-1 can be different, but are Or, the value of λ2-λ1, the value of λ3-λ2, ....λ m -λ m-1 Some of these values ​​may be the same, some may be different, but all of them are An integer multiple of .

[0279] To address fiber dispersion, another possible implementation approach is to ensure that the wavelengths of the multiple optical signals generated by the optical signal generation module are within a low-dispersion band. If the wavelengths of the multiple optical signals generated by the optical signal generation module are within the low-dispersion band, the fiber dispersion value will be below a threshold, thereby reducing the impact of fiber dispersion. For example, the threshold can be a fixed value, or it can be related to at least one of the fiber type, fiber length, and the power of the optical signal input to the fiber.

[0280] For example, for G.652E optical fiber, the corresponding low-dispersion band wavelength can be between 1300nm and 1324nm. That is, when the system uses G.652E optical fiber, the wavelength range of the multiple optical signals generated by the optical signal generation module can all be between 1300nm and 1324nm, that is, using wavelengths in the low-dispersion region, thereby reducing the impact of optical fiber dispersion and improving the RF signal power recovered from multiple optical signals of different wavelengths.

[0281] It is understood that different types of optical fibers may have different wavelengths in their corresponding low-dispersion bands. Therefore, in other implementations of the present application, if other types of optical fibers are used, the wavelength ranges of the multiple optical signals generated by the optical signal generation module may vary. For example, for G.654E optical fibers, the wavelength of their corresponding low-dispersion band is in the 1550nm band. That is, if the RoF transmission system uses G.654E optical fibers, the wavelength range of the multiple optical signals generated by the optical signal generation module may all be in the 1550nm band, for example, between 1540-1560nm.

[0282] To address the problem of fiber dispersion, another possible implementation method is to set a dispersion compensator (or dispersion compensation module) in the optical fiber to reduce the impact of fiber dispersion and increase the RF signal power recovered from multiple modulated optical signals.

[0283] It is understandable that in other implementations of the present application, other methods may be used to reduce the influence of optical fiber dispersion, and the embodiments of the present application are not limited thereto.

[0284] The RoF transmission system provided in this application will be described below with reference to specific experimental data.

[0285] FIG6 is a schematic diagram of a single-channel (or single-line) RoF transmission system structure. The difference from FIG3 is that in the RoF transmission system structure shown in FIG6 , the laser generates not multiple optical signals but a single optical signal. In other words, in the RoF transmission system structure shown in FIG6 , the laser generates a single optical signal with a wavelength of λ. c The RF signal generation module can generate an RF signal with a frequency of f RF The electro-optical modulation module receives the RF signal generated by the RF signal generation module and the laser generates one or more optical signals, and modulates the RF signal onto an optical signal to obtain a modulated optical signal. After optical fiber transmission, the wavelength of the optical fiber finally transmitted by the optoelectronic demodulation module is The demodulated frequency of the optical signal is f RF In the structure shown in Figure 3, the electro-optical modulation module receives the RF signal generated by the RF signal generation module and the multiple optical signals generated by the optical signal generation module, and modulates the RF signal onto the multiple optical signals to obtain multiple modulated optical signals. After optical fiber transmission, the optoelectronic demodulation module finally demodulates the multiple modulated optical signals transmitted in the optical fiber to obtain a frequency of f RF RF signal.

[0286] Furthermore, the structure shown in FIG6 does not include a reflected light power detection module and a feedback conversion circuit.

[0287] The structure shown in Figure 6 is used to set up a single-line control group 1. The single-line control group can be understood as modulating the RF signal onto an optical signal. In the structure shown in Figure 6, it is assumed that the wavelength λ of the optical signal generated by the laser is cThe wavelength is 1550 nm and the power is 12 dBm. The RF signal generation module generates a sinusoidal RF signal with a frequency of 3.5 GHz and a power of 0 dBm. The electro-optical modulation module modulates the RF signal onto the optical signal. Its half-wave voltage is 3.5 V, its extinction ratio is 35 dB, and it operates at the quadrature point. The optical amplifier operates in automatic power control mode, with a fixed output optical power of 1 W. The photoelectric demodulation module (or photodetector) has a responsivity of 0.7 A / W. In the structure shown in Figure 6, a 300-meter G.652E optical fiber is selected. An adjustable optical attenuator is added after the optical amplifier. The adjustable optical attenuator adjusts the optical amplifier output power (or input optical power) between -10 and 30 dBm. An optical power meter is used to measure the output optical power (or transmitted optical power) and the reflected optical power at port 2 (i.e., the second port) of the circulator.

[0288] A four-line experimental set 1 was set up using the structure shown in Figure 3. In this structure, an optical signal generation module was configured to generate four optical signals of different wavelengths. For example, this optical signal generation module could be an ultra-wideband optical frequency comb generation module, outputting a four-line optical frequency comb with comb wavelengths of λ1, λ2, λ3, and λ4, respectively. Assume that: λ1 = 1549 nm, λ2 = 1550 nm, λ3 = 1551 nm, and λ4 = 1552 nm, and the comb power is 12 dBm. The radio frequency signal generation module generates an RF signal, for example, with a frequency of 3.5 GHz, a power of 0 dBm, and a sinusoidal RF wave form. The electro-optical modulation module could include four electro-optical intensity modulators, each with a half-wave voltage of 3.5 V and an extinction ratio of 35 dB, operating at the quadrature point. The electro-optical modulation module receives the RF signal, as well as λ1, λ2, λ3, and λ4, and modulates the RF signal onto λ1, λ2, λ3, and λ4. The optical amplifier operates in automatic power control mode, with a fixed output optical power of 1W. The optoelectronic demodulation module (or optoelectronic demodulation array) includes four photodetectors, each with a responsivity of 0.7A / W. In this case, the experimental group is referred to as a four-wire experimental group. A four-wire experimental group can be understood as modulating the RF signal into four optical signals of different wavelengths, generating four modulated optical signals for transmission through the optical fiber. Furthermore, in this experimental group, a 300-meter G.652E optical fiber was selected. An adjustable optical attenuator was added after the optical amplifier to adjust the output optical power of the optical amplifier between -10 and 30dBm. The optical power output (or transmitted optical power) and the reflected optical power at circulator port 2 were measured using an optical power meter.

[0289] An eight-line experimental set 1 was set up using the structure shown in Figure 3. In this structure, an optical signal generation module was configured to generate eight optical signals of different wavelengths. For example, this optical signal generation module could be an ultra-wideband optical frequency comb generation module, outputting an 8-line optical frequency comb with comb wavelengths of λ1, λ2, λ3, λ4, λ5, λ6, λ7, and λ8, respectively. Assume that: λ1 = 1547 nm, λ2 = 1548 nm, λ3 = 1549 nm, λ4 = 1550 nm, λ5 = 1551 nm, λ6 = 1552 nm, λ7 = 1553 nm, and λ8 = 1554 nm, with comb power of 12 dBm. The radio frequency signal generation module generated an RF signal, for example, with a frequency of 3.5 GHz and a power of 0 dBm, exhibiting a sinusoidal RF wave form. The electro-optical modulation module could include eight photoelectric intensity modulators, each with a half-wave voltage of 3.5 V and an extinction ratio of 35 dB, operating at quadrature points. The electro-optical modulation module receives the RF signal, as well as λ1, λ2, λ3, λ4, λ5, λ6, λ7, and λ8, and modulates the RF signal onto λ1, λ2, λ3, λ4, λ5, λ6, λ7, and λ8. The optical amplifier operates in automatic power control mode, with a fixed output optical power of 1W. The photoelectric demodulation module (or photoelectric demodulation array) can include eight photodetectors, each with a responsivity of 0.7A / W. In this case, the experimental group is an eight-line experimental group. The eight-line experimental group can be understood as modulating the RF signal onto eight optical signals of different wavelengths, resulting in eight modulated optical signals that are transmitted through the optical fiber. In addition, in this experimental group, a 300-meter G.652E optical fiber was also selected, and an adjustable optical attenuator was added after the optical amplifier. The adjustable optical attenuator was used to adjust the optical power output of the optical amplifier (or the incoming optical power) between -10 and 30 dBm. The optical power output from the fiber (or the transmitted optical power) and the reflected optical power at circulator port 2 were measured using an optical power meter.

[0290] Figure 7 shows the changes in the reflected optical power and output optical power for the single-line control group 1. The horizontal axis value corresponding to the point where the output optical power and the reflected optical power are equal (i.e., the optical power output by the optical amplifier) ​​is used as the SBS power threshold. As can be seen from Figure 7, for the single-line control group 1, the SBS power threshold is approximately 23dBm.

[0291] Figure 8 shows the changes in the reflected optical power and output optical power for the four-wire experiment group 1. The horizontal axis value corresponding to the equal output optical power and reflected optical power (i.e., the optical power output by the optical amplifier) ​​is used as the SBS power threshold. As can be seen from Figure 8, for the four-wire experiment group 1, the SBS power threshold is approximately 27dBm.

[0292] Figure 9 shows the numerical changes in the reflected optical power and the output optical power for the eight-line experimental group 1. The horizontal axis value corresponding to when the output optical power and the reflected optical power are equal (i.e., the optical power output by the optical amplifier) ​​is used as the SBS power threshold. As can be seen from Figure 9, since the point where the output optical power and the reflected optical power are equal has not yet appeared, the SBS power threshold for the eight-line experimental group 1 is greater than 30dBm.

[0293] It can be seen from FIG. 7 to FIG. 9 that as the number of optical signals modulated into RF signals increases, the SBS power threshold gradually increases, that is, the incoming optical power gradually increases.

[0294] Furthermore, a single-line control group 2 is set up using the structure shown in Figure 6, wherein the difference between the single-line control group 2 and the single-line control group 1 is that a G.652E optical fiber with a length of 1000 meters is used, and the settings of other parameters are the same as those of the single-line control group 1. For details, please refer to the above description of the single-line control group 1. For the sake of brevity, it will not be repeated here.

[0295] The four-wire experimental group 2 was set up using the structure shown in Figure 3. The difference between the four-wire experimental group 2 and the four-wire experimental group 1 is that a G.652E optical fiber with a length of 1000 meters was used. The settings of other parameters were the same as those of the four-wire experimental group 1. For details, please refer to the above description of the four-wire experimental group 1. For the sake of brevity, it will not be repeated here.

[0296] The eight-wire experimental group 2 was set up using the structure shown in Figure 3. The difference between the eight-wire experimental group 2 and the eight-wire experimental group 1 is that a G.652E optical fiber with a length of 1000 meters was used. The settings of other parameters were the same as those of the eight-wire experimental group 1. For details, please refer to the above description of the eight-wire experimental group 1. For the sake of brevity, it will not be repeated here.

[0297] Figure 10 shows the changes in the reflected optical power and output optical power for the single-line control group 2. The horizontal axis value corresponding to the point where the output optical power and the reflected optical power are equal (i.e., the optical power output by the optical amplifier) ​​is used as the SBS power threshold. As can be seen from Figure 10, for single-line control group 2, the SBS power threshold is approximately 17dBm.

[0298] Figure 11 shows the changes in the reflected optical power and the output optical power for the four-wire experiment group 2. The horizontal axis value corresponding to the equal output optical power and the reflected optical power (i.e., the optical power output by the optical amplifier) ​​is used as the SBS power threshold. As can be seen from Figure 11, for the four-wire experiment group 2, the SBS power threshold is approximately 25dBm.

[0299] Figure 12 shows the changes in the reflected optical power and output optical power for the eight-line experimental group 2. The horizontal axis value corresponding to the equal output optical power and reflected optical power (i.e., the optical power output by the optical amplifier) ​​is used as the SBS power threshold. As can be seen from Figure 12, for the eight-line experimental group 2, the SBS power threshold is approximately 28dBm.

[0300] It can be seen from FIG9 to FIG11 that as the number of optical signals modulated into different wavelengths by the RF signal increases, the SBS power threshold gradually increases, that is, the incoming optical power gradually increases.

[0301] FIG13 is a schematic diagram of another RoF transmission system structure proposed in this application. As shown in FIG13 , the system includes:

[0302] The optical signal generating module is used to generate multiple optical signals. It is understood that the wavelengths of the multiple optical signals can be different, that is, the wavelengths of any two optical signals can be different; or the wavelengths of the multiple optical signals can be partially the same and partially different.

[0303] For example, the RF signal generation module can generate wavelengths of: λ1, λ2, λ3...λ m These m optical signals of different wavelengths are all optical signals that have not been electro-optically modulated.

[0304] The RF signal generating module is used to generate a RF signal. For example, the RF signal generated by the RF signal generating module is RF, and the frequency of the RF signal is f RF .

[0305] The electro-optical modulation module receives the RF signal generated by the RF signal generation module and modulates the RF signal into a wavelength of λ. s optical signal (i.e., modulated optical signal).

[0306] It should be understood that in other embodiments of the present application, the electro-optical modulation module receives the RF signal generated by the RF signal generation module, and can also modulate the RF onto multiple optical signals to obtain multiple modulated optical signals. In the following example, the electro-optical modulation module receives the RF signal generated by the RF signal generation module, modulates the RF onto an optical signal, and obtains a wavelength of λ s The modulated optical signal.

[0307] As a possible implementation, λ s and λ1, λ2, λ3….λ m The same one in .

[0308] As another possible implementation, λ s and λ1, λ2, λ3….λ m They are all different.

[0309] The output end of the electro-optical modulation module is connected to the input end of the combiner, and the output end of the optical signal generation module is connected to the input end of the combiner. The combiner is used to receive multiple optical signals generated by the optical signal generation module (i.e., multiple optical signals that have not been electro-optically modulated) and the optical signal output by the electro-optical modulation module (modulated optical signal), and combine λ s and λ1, λ2, λ3….λ m Combined into one optical signal.

[0310] An optical amplifier, whose input is connected to the output of the combiner, receives the optical signal output by the combiner and amplifies the power of the optical signal. For example, the optical amplifier can amplify the power of the optical signal to the watt level, allowing the amplified optical signal to be transmitted through the optical fiber. It is understood that the optical amplifier is optional.

[0311] The optical fiber has its input end connected to the output end of the optical amplifier, and the optical fiber is used to transmit the optical signal amplified by the optical amplifier. In the embodiments of the present application, the optical fiber can use a commonly used optical fiber, such as G.652E optical fiber, G.654E optical fiber, etc. The specific type of optical fiber used in the embodiments of the present application is not limited.

[0312] The optoelectronic demodulation module has its input end connected to the output end of the optical fiber. The optoelectronic demodulation module is used to receive the optical signal transmitted by the optical fiber, and demodulate and output the RF signal from the optical signal output by the optical fiber. For example, the frequency f can be demodulated from the optical signal. RF RF signal.

[0313] Optionally, the optoelectronic demodulation module can transmit the demodulated RF signal to an analog RF circuit. Exemplarily, the analog RF circuit may include one or more of a filter, an amplifier, a mixer, an antenna, a power splitter, a combiner, and the like.

[0314] The RoF transmission system provided herein modulates an RF signal into an optical signal, combines this modulated optical signal with other unmodulated optical signals, and transmits them through an optical fiber. Ultimately, the RF signal modulated on the optical signal is demodulated at the output end of the optical fiber transmission. In other words, by treating the other unmodulated optical signals as interference signals and transmitting them together with the modulated RF signal through the optical fiber, the optical signal spectrum can be broadened, reducing the input optical energy density and increasing the optical signal power incident on the fiber. This increases the SBS power threshold, thereby improving the performance and transmission efficiency of the RoF transmission system.

[0315] It is understandable that the RF signal generating module, RF signal generating module, and optical amplifier shown in FIG13 are optional. In the system shown in FIG13 , the RF signal generating module, RF signal generating module, and optical amplifier may not be included. In this case, the electro-optical modulation module may obtain or acquire the RF signal using other methods, and the combiner may also obtain or acquire multiple optical signals that are not electro-optically modulated using other methods. This embodiment of the present application is not limited thereto.

[0316] Optionally, as a possible implementation, in order to increase the flexibility of the RoF transmission system, based on the structure shown in FIG13 , as shown in FIG14 , the RoF transmission system provided in the embodiment of the present application may further include:

[0317] Optical circulator, reflected light power detection module and feedback conversion circuit.

[0318] The first port of the optical circulator is connected to the output of the optical amplifier, and the second port of the optical circulator is connected to the input of the optical fiber. The optical signal output by the optical amplifier is transmitted to the optical circulator through the first port of the optical circulator, and then transmitted to the optical fiber through the second port of the optical circulator, and then transmitted within the optical fiber. The third port of the optical circulator is connected to the input of the reflected light power detection module, the output of the reflected light power detection module is connected to the input of the feedback control unit, and the output of the feedback control unit is connected to the optical signal generation module.

[0319] Since the impact of SBS on the system is mainly the loss of channel energy caused by the back reflection of light in the optical fiber, the reflected light power detection module can be used to detect the reflected light power of multiple modulated optical signals transmitted in the optical fiber. When it is detected that the reflected light power is greater than or equal to a preset threshold (for example, a first threshold), a signal (for example, a first signal) is sent to the feedback control unit. The feedback control unit is used to generate a second signal (for example, a feedback level signal) under the action of the first signal and transmit it to the optical signal generation module. The optical signal generation module adjusts the wavelength and / or number of the multiple optical signals generated according to the feedback level signal. For example, the number of optical signals generated by the optical signal generation module and / or the wavelength difference between two adjacent optical signals in different optical signals, that is, the wavelength interval, etc., are adjusted.

[0320] Exemplarily, the preset threshold (first threshold) may be a preset or predefined SBS threshold power.

[0321] When the reflected light power detection module detects that the reflected light power is less than a preset threshold, it proves that the power of the optical signal incident on the optical fiber is less than the SBS threshold power, and the RoF transmission system can operate normally. The wavelengths and / or number of the multiple optical signals generated by the previous optical signal generation module can be maintained, and the multiple optical signals generated by the optical signal generation module and the modulated optical signal can be transmitted together in the optical fiber.

[0322] By providing a reflected light power detection module and a feedback control unit, the flexibility of the RoF transmission system can be improved. When the power of the optical signal incident on the optical fiber is greater than or equal to the preset SBS threshold power, the quantity and / or wavelength of the optical signal generated by the optical signal generation module are promptly adjusted to ensure that the power of the optical signal incident on the optical fiber is less than the SBS threshold power. This can improve the stability and performance of the RoF transmission system while increasing the power of the optical signal incident on the optical fiber.

[0323] Optionally, as a possible implementation method, in the structure shown in FIG13 or FIG14 , the modulation mode of the electro-optical modulation module can be a direct modulation mode or an indirect modulation mode, which will be explained respectively below.

[0324] Direct modulation means that the electro-optical modulation module can both generate a light source and modulate the RF signal. The RF signal is modulated onto the optical signal generated by the electro-optical modulation module, resulting in a modulated optical signal. Direct modulation reduces the complexity and cost of implementing the optical modulation module.

[0325] Indirect modulation (also known as external modulation) involves an electro-optical modulation module comprising a light source and an electro-optical modulation submodule. The light source generates an optical signal, which is then input into the electro-optical modulation submodule. The electro-optical modulation submodule receives the optical signal and the radio frequency signal, modulating the radio frequency signal onto the optical signal to produce a modulated optical signal. Indirect modulation improves the efficiency of modulating the radio frequency signal onto the optical signal and reduces power loss during the modulation process.

[0326] As an example, when indirect modulation is used, the wavelength of the optical signal generated by the light source in the electro-optical modulation module is the same as the wavelength of any of the multiple optical signals generated by the optical signal generation module. This allows the RoF transmission system to transmit higher-frequency RF signals, improving the performance of the RoF transmission system.

[0327] As another possible implementation, when indirect modulation is used, the wavelength of the optical signal generated by the light source in the electro-optical modulation module and any of the wavelengths of the multiple optical signals generated by the optical signal generation module are different. In this implementation, the light source of the electro-optical modulation module can be independent of the optical signal generation module, increasing the flexibility of the RoF transmission system.

[0328] In some possible implementations of the present application, the optical signal generation module in FIG. 13 or FIG. 14 may have a variety of different implementations depending on the principle of generating the optical signal. For example, the optical signal generation module may include: an ultra-wideband optical frequency comb generation module based on a mode-locked laser, an optical signal generation module based on fiber nonlinear effects, an optical signal generation module based on an optoelectronic oscillator, an optical signal generation module based on a microring resonator, or an optical signal generation module based on an electro-optical modulator. For an explanation of the specific implementation of the optical signal generation module, reference may be made to the above-mentioned specific description of the specific implementation of the optical signal generation module. For the sake of brevity, this description will not be repeated here.

[0329] The RoF transmission system provided by the present application modulates one RF signal into an optical signal, combines the modulated optical signal with other unmodulated optical signals into one signal, and transmits the signal in an optical fiber. Finally, the RF signal modulated on the optical signal is demodulated at the output end of the optical fiber transmission. Since the transmission of multiple optical signals in an optical fiber will cause optical fiber dispersion, the modulated optical signal and other unmodulated optical signals may cancel each other out when received, resulting in a low power of the RF signal recovered from the modulated optical signal. For example, in the structure shown in Figure 13 or Figure 14, the unmodulated optical signals λ1, λ2, λ3...λ output from the optical amplifier are m and the modulated optical signal λ s , will be affected by the fiber dispersion during the transmission process in the optical fiber, and may cancel each other out when receiving, resulting in s The power of the demodulated RF signal is low, which affects the power of RF signal transmission.

[0330] To address fiber dispersion, one possible implementation approach is to configure the wavelengths of the multiple optical signals generated by the optical signal generation module to fall within a low-dispersion band, thereby reducing the impact of fiber dispersion. Another possible implementation approach is to incorporate a dispersion compensator (or dispersion compensation module) within the optical fiber to reduce the impact of fiber dispersion and increase the RF signal power recovered from the multiple modulated optical signals. For details on these two approaches, refer to the detailed descriptions above and are omitted here for brevity.

[0331] The communication device provided in the embodiments of the present application will be described in detail below.

[0332] FIG15 is a schematic block diagram of a communication device 1500 according to an embodiment of the present application. As shown in FIG15 , the communication device 1500 may include an electro-optical modulation module and a first optical fiber. The electro-optical modulation module is configured to modulate a radio frequency signal onto multiple optical signals to obtain multiple modulated optical signals, and the first optical fiber is configured to transmit the multiple modulated optical signals.

[0333] The communication device provided in the present application utilizes an electro-optical modulation module to modulate an RF signal onto multiple optical signals, and transmits the multiple optical signals obtained after modulation in an optical fiber, thereby broadening the spectrum of the incoming optical signal, reducing the energy density of the incoming optical fiber, and thus increasing the power of the optical signal incident on the optical fiber.

[0334] In some possible implementations, the communication device 1500 may further include:

[0335] Optical signal generating module: The optical signal generating module is used to generate multiple optical signals;

[0336] Radio frequency signal generating module: The radio frequency signal generating module is used to generate the radio frequency signal;

[0337] Optical amplifier: The optical amplifier is used to amplify the power of multiple modulated optical signals and transmit the power-amplified optical signals to the first optical fiber.

[0338] In some possible implementations, the communication device 1500 may further include: an optical circulator, a reflected light power detection module, and a feedback control unit.

[0339] The first port of the optical circulator is connected to the output end of the optical amplifier, the second port of the optical circulator is connected to the input end of the first optical fiber, the third port of the optical circulator is connected to the input end of the reflected light power detection module, the output end of the reflected light power detection module is connected to the input end of the feedback control unit, and the output end of the feedback control unit is connected to the optical signal generation module;

[0340] The reflected light power detection module is used to detect the reflected light power of multiple modulated optical signals transmitted in the first optical fiber. When the reflected light power is greater than or equal to a first threshold, the module sends a first signal to the feedback control unit. The feedback control unit is used to generate a second signal under the action of the first signal and transmit the second signal to the optical signal generation module. The optical signal generation module is used to adjust the wavelengths and / or quantities of the multiple optical signals generated according to the second signal.

[0341] In some possible implementations, the RF signal generating module is used to generate N RF signals, the electro-optical modulation module includes N electro-optical modulation sub-modules, and the communication device 1500 may further include: a first wavelength division demultiplexer and a wavelength division multiplexer.

[0342] The first demultiplexer is used to decompose the M optical signals generated by the optical signal generating module into N channels, where M is an integer greater than 1, and the i-th channel includes K i optical signals, i is an integer greater than or equal to 1 and less than or equal to N.

[0343] The i-th electro-optical modulation submodule is used to modulate the i-th RF signal to the K i On the optical signal, we get K i modulated optical signals, and N electro-optical modulation submodules output Q modulated optical signals, where Q is an integer greater than or equal to 1 and less than or equal to M.

[0344] The wavelength division multiplexer is used to combine the Q modulated optical signals and transmit them to the optical amplifier.

[0345] In some possible implementations, in the communication device 1500, the optical signal generating module includes any one of the following: an ultra-wideband optical frequency comb generating module based on a mode-locked laser, an optical signal generating module based on optical fiber nonlinear effects, an optical signal generating module based on an optoelectronic oscillator, an optical signal generating module based on a microring resonator, or an optical signal generating module based on an electro-optical modulator.

[0346] In some possible implementations, the wavelengths of the multiple optical signals generated by the optical signal generating module are in a low dispersion band.

[0347] In some possible implementations, the first optical fiber further includes a dispersion compensator, which is used to compensate for the dispersion of the modulated optical signal during transmission in the first optical fiber.

[0348] In some possible implementations, among the multiple optical signals generated by the optical signal generating module, a wavelength interval Δλ between two adjacent optical signals satisfies the following condition:

[0349]

[0350] Among them, n is a positive integer, f RFi represents the frequency of the RF signal modulated onto multiple optical signals, D(λ) represents the dispersion coefficient of the optical fiber, and L represents the length of the optical fiber.

[0351] In some possible implementations, the wavelengths of the multiple optical signals are different.

[0352] In some possible implementations, the communication device 1500 may further include: an optoelectronic demodulation module, which is configured to demodulate and output a radio frequency signal from a plurality of modulated optical signals output from the optical fiber.

[0353] For the detailed description and beneficial effects of each implementation of the communication device 1500, reference may be made to the description of the corresponding parts in the implementation shown in FIG. 1 to FIG. 5 , which will not be repeated here for the sake of brevity.

[0354] FIG16 is a schematic block diagram of another communication device 1600 according to an embodiment of the present application. As shown in FIG16 , the communication device 1600 may include a second optical fiber and an optoelectronic demodulation module. The optoelectronic demodulation module is configured to demodulate and output a radio frequency signal from multiple modulated optical signals output by the second optical fiber. The multiple modulated optical signals transmitted by the second optical fiber are obtained by modulating the radio frequency signal onto multiple optical signals.

[0355] The communication device provided in the present application transmits multiple optical signals obtained after modulation in an optical fiber, and finally demodulates the RF signal modulated on the multiple optical signals at the output end of the optical fiber transmission, thereby broadening the spectrum of the incoming optical signal, reducing the energy density of the incoming optical fiber, thereby increasing the power of the optical signal incident to the optical fiber, and improving the transmission efficiency of the RF signal.

[0356] In some possible implementations, the optoelectronic demodulation module includes N optoelectronic demodulation sub-modules, and the communication device 1600 may further include: a second wavelength division demultiplexer.

[0357] The second demultiplexer is used to decompose the optical signal output from the second optical fiber into N optical signals, wherein the i-th optical signal includes K i The optical demodulation module includes an optical signal modulated by a first optical signal and an optical signal modulated by a second wavelength division multiplexer. The optical demodulation module includes an i-th optical signal and an optical signal modulated by a second optical signal modulator. The i-th optical signal and the optical signal modulator submodule in the optical demodulation module are configured to demodulate the i-th radio frequency signal from the i-th optical signal output by the second wavelength division multiplexer. The optical demodulation module is configured to output N radio frequency signals. In this implementation, multiple RF signals can be transmitted simultaneously, i.e., MIMO transmission is implemented using the communication device, thereby improving the performance of the communication device.

[0358] In some possible implementations, the communication device 1600 may further include: an electro-optical modulation module, which is used to modulate the radio frequency signal onto multiple optical signals to obtain multiple modulated optical signals, and transmit the multiple modulated optical signals to the second optical fiber.

[0359] The embodiment of the present application further provides a RoF transmission system, which includes: the above-mentioned communication device 1500 and the above-mentioned communication device 1600.

[0360] The radio frequency over fiber transmission system provided in the embodiments of the present application utilizes an electro-optical modulation module to modulate an RF signal onto multiple optical signals, transmits the modulated multiple optical signals through an optical fiber, and finally, utilizes an optoelectronic demodulation module at the output end of the optical fiber transmission to demodulate the RF signal modulated onto the multiple optical signals. This broadens the spectrum of the incoming optical signal, reduces the energy density of the incoming optical fiber, and thereby increases the power of the optical signal incident on the optical fiber, thereby improving the performance and transmission efficiency of the RoF transmission system.

[0361] In some possible implementations, the first optical fiber in the communication device 1500 and the second optical fiber in the communication device 1600 may be the same optical fiber.

[0362] The present application also provides a method for transmitting a radio frequency signal. The method can be applied to the RoF transmission system provided in the present application. The method includes: an electro-optical modulation module receives a radio frequency signal and multiple optical signals, modulates the radio frequency signal onto the multiple optical signals to obtain multiple modulated optical signals, and transmits the multiple modulated optical signals to an optical fiber; after receiving the multiple modulated optical signals, the optical fiber transmits the multiple modulated optical signals to an optoelectronic demodulation module; after receiving the multiple modulated optical signals, the optoelectronic demodulation module demodulates the multiple modulated optical signals and outputs an radio frequency signal.

[0363] The radio frequency signal transmission method of the embodiment of the present application modulates the RF signal onto multiple optical signals, transmits the multiple modulated optical signals in an optical fiber, and finally demodulates the RF signal modulated on the multiple optical signals at the output end of the optical fiber transmission, thereby broadening the spectrum of the incoming optical signal, reducing the energy density of the incoming optical fiber, thereby increasing the power of the optical signal incident on the optical fiber, and improving the transmission performance and transmission efficiency of the RF signal.

[0364] For example, in some possible implementations, the method further includes: an optical signal generating module generating the multiple optical signals and transmitting the multiple optical signals to the electro-optical modulation module; a radio frequency signal generating module generating the radio frequency signal and transmitting the radio frequency signal to the electro-optical modulation module; an optical amplifier receiving the multiple modulated optical signals transmitted by the electro-optical modulation module, amplifying the power of the multiple modulated optical signals, and transmitting the multiple modulated optical signals after power amplification to the optical fiber.

[0365] For example, in some possible implementations, the method further includes: a reflected light power detection module detecting the reflected light power of multiple modulated optical signals transmitted in the optical fiber; when the reflected light power is greater than or equal to a first threshold, the reflected light power detection module sending a first signal to a feedback control unit; the feedback control unit receiving the first signal, generating a second signal based on the first signal, and sending the second signal to the optical signal generation module; the optical signal generation module receiving the second signal, and adjusting the wavelengths and / or number of the multiple optical signals generated based on the second signal. In this implementation, when the power of the optical signal incident on the optical fiber is greater than or equal to a preset SBS threshold power, the number and / or wavelength of the optical signals generated by the optical signal generation module are promptly adjusted to ensure that the power of the optical signal incident on the optical fiber is less than the SBS threshold power, thereby further improving the transmission performance and efficiency of the RF signal on the basis of increasing the power of the optical signal incident on the optical fiber.

[0366] For a description of various possible implementations and beneficial effects of the radio frequency signal transmission method provided in the embodiments of the present application, reference may be made to the descriptions of the relevant implementations in Figures 1 to 6 above, which will not be repeated here for the sake of brevity.

[0367] An embodiment of the present application also provides a method for transmitting a radio frequency signal, which can be applied to the communication device 1500 provided in an embodiment of the present application. The method includes: an electro-optical modulation module receives a radio frequency signal and multiple optical signals, modulates the radio frequency signal onto the multiple optical signals to obtain multiple modulated optical signals, and transmits the multiple modulated optical signals to a first optical fiber, and the first optical fiber transmits the multiple modulated optical signals.

[0368] The radio frequency signal transmission method of the embodiment of the present application modulates the RF signal onto multiple optical signals, and transmits the multiple optical signals obtained after modulation in an optical fiber, thereby broadening the spectrum of the incoming optical signal, reducing the energy density of the incoming optical fiber, and thus increasing the power of the optical signal incident to the optical fiber.

[0369] For a description of various possible implementations and beneficial effects of the radio frequency signal transmission method provided in the embodiments of the present application, reference may be made to the above description of the relevant implementations of the communication device 1500 , which will not be repeated here for the sake of brevity.

[0370] An embodiment of the present application also provides a method for transmitting a radio frequency signal, which can be applied to the communication device 1600 provided in an embodiment of the present application. The method includes: a second optical fiber receives and transmits multiple modulated optical signals, and transmits the multiple modulated optical signals to an optoelectronic demodulation module, where the multiple modulated optical signals are obtained by modulating a radio frequency signal onto the multiple optical signals; the optoelectronic demodulation module receives the multiple modulated optical signals, demodulates the multiple modulated optical signals output by the second optical fiber, and outputs a radio frequency signal.

[0371] The radio frequency signal transmission method provided in the embodiment of the present application modulates the RF signal onto multiple optical signals, transmits the multiple modulated optical signals in an optical fiber, and finally demodulates the RF signal modulated on the multiple optical signals at the output end of the optical fiber transmission, thereby broadening the spectrum of the incoming optical signal, reducing the energy density of the incoming optical fiber, thereby increasing the power of the optical signal incident on the optical fiber, and improving the transmission performance and transmission efficiency of the RF signal.

[0372] For a description of various possible implementations and beneficial effects of the radio frequency signal transmission method provided in the embodiments of the present application, reference may be made to the above description of the relevant implementations of the communication device 1600 , which will not be repeated here for the sake of brevity.

[0373] FIG17 is a schematic block diagram of another example of a communication device 1700 according to an embodiment of the present application. As shown in FIG17 , the communication device 1700 may include an electro-optical modulation module, a combiner, and a third optical fiber. The electro-optical modulation module is configured to modulate a radio frequency signal onto an optical signal to obtain a modulated optical signal. The combiner is configured to combine multiple optical signals that have not been electro-optically modulated and the modulated optical signal into a single optical signal. The third optical fiber is configured to transmit the optical signal output by the combiner.

[0374] The communication device provided herein modulates an RF signal into an optical signal, combines this modulated optical signal with other unmodulated optical signals, and transmits the combined signal through an optical fiber. In other words, the unmodulated optical signal, acting as an interference signal, is transmitted along with the modulated RF signal through the optical fiber. This broadens the optical signal spectrum, reduces the optical energy density entering the fiber, and increases the optical signal power incident on the fiber. This increases the SBS power threshold, thereby improving the performance and transmission efficiency of the communication device.

[0375] In some possible implementations, the communication device 1700 may further include: an optical signal generating module: the optical signal generating module is used to generate multiple optical signals that are not electro-optically modulated; a radio frequency signal generating module: the radio frequency signal generating module is used to generate the radio frequency signal; an optical amplifier: the optical amplifier is used to amplify the power of the optical signal and transmit the power-amplified optical signal to a third optical fiber.

[0376] In some possible implementations, the communication device 1700 may further include: an optical circulator, a reflected light power detection module, and a feedback control unit, wherein a first port of the optical circulator is connected to the output end of the optical amplifier, a second port of the optical circulator is connected to the input end of the third optical fiber, a third port of the optical circulator is connected to the input end of the reflected light power detection module, an output end of the reflected light power detection module is connected to the input end of the feedback control unit, and an output end of the feedback control unit is connected to the optical signal generation module; the reflected light power detection module is configured to: detect the reflected light power of multiple modulated optical signals transmitted in the third optical fiber, and when the reflected light power is greater than or equal to a first threshold, send a first signal to the feedback control unit; the feedback control unit is configured to, under the action of the first signal, generate a second signal and transmit the second signal to the optical signal generation module; the optical signal generation module is configured to adjust the wavelength and / or quantity of the generated multiple non-electro-optically modulated optical signals according to the second signal.

[0377] In some possible implementations, the electro-optical modulation module includes: a direct modulation electro-optical modulation module or an indirect modulation electro-optical modulation module, the direct modulation electro-optical modulation module is used to generate an optical signal and modulate the radio frequency signal, the indirect modulation optical modulation module includes a light source generation module and an electro-optical modulation sub-module, the light source generation module is used to generate an optical signal, and the electro-optical modulation sub-module is used to modulate the radio frequency signal onto the optical signal to obtain a modulated optical signal.

[0378] In some possible implementations, when the electro-optical modulation module includes the electro-optical modulation module of the indirect modulation method, the wavelength of the optical signal generated by the light source generating module is the same as or different from the wavelength of any one of the multiple optical signals that have not been electro-optically modulated.

[0379] In some possible implementations, the wavelengths of the multiple optical signals generated by the optical signal generation module that are not electro-optically modulated are in a low dispersion band.

[0380] In some possible implementations, the third optical fiber further includes a dispersion compensator, which is used to compensate for the dispersion of the optical signal during transmission in the third optical fiber.

[0381] In some possible implementations, the wavelengths of the multiple optical signals that are not electro-optically modulated are different.

[0382] In some possible implementations, the communication device 1700 may further include: an optoelectronic demodulation module, wherein the optoelectronic demodulation module is configured to demodulate the optical signal output from the optical fiber and output a radio frequency signal.

[0383] For the detailed description and beneficial effects of each implementation of the communication device 1700, please refer to the description of the corresponding parts in the implementation shown in Figures 13 to 14. For the sake of brevity, they will not be repeated here.

[0384] FIG18 is a schematic block diagram of another example of a communication device 1800 according to an embodiment of the present application. As shown in FIG18 , the communication device 1800 may include a fourth optical fiber and an optoelectronic demodulation module. The optoelectronic demodulation module is configured to demodulate the optical signal output from the fourth optical fiber and output a radio frequency signal. The optical signal transmitted in the fourth optical fiber is obtained by combining multiple optical signals that have not been electro-optically modulated and an optical signal that has undergone electro-optical modulation into one optical signal. The electro-optically modulated optical signal is obtained by modulating the radio frequency signal onto the optical signal.

[0385] The communication device provided in the embodiments of the present application combines the modulated optical signal and other unmodulated optical signals into one path, which is then transmitted through an optical fiber. Ultimately, the RF signal modulated on the optical signal is demodulated at the output end of the optical fiber transmission. In other words, by treating the other unmodulated optical signal as an interfering optical signal and transmitting it along with the modulated RF signal through the optical fiber, the optical signal spectrum can be broadened, the energy density of the light entering the fiber can be reduced, the power of the optical signal incident on the fiber can be increased, and the transmission efficiency of the RF signal can be improved.

[0386] In some possible implementations, the communication device 1800 may further include an electro-optical modulation module and a combiner. The electro-optical modulation module is configured to modulate a radio frequency signal onto an optical signal to obtain a modulated optical signal. The combiner is configured to combine multiple unmodulated optical signals and the modulated optical signal into one optical signal and transmit the signal to a fourth optical fiber.

[0387] The present application also provides a RoF transmission system, which includes: the above-mentioned communication device 1700 and the above-mentioned communication device 1800.

[0388] In some possible implementations, the third optical fiber in the communication device 1700 and the fourth optical fiber in the communication device 1800 may be the same optical fiber.

[0389] The embodiments of the present application also provide a method for transmitting a radio frequency signal, which can be applied to the RoF transmission system provided in the embodiments of the present application. The method includes: an electro-optical modulation module receives a radio frequency signal, modulates the radio frequency signal onto an optical signal, obtains a modulated optical signal, and transmits the modulated optical signal to the combiner; the combiner receives the modulated optical signal and multiple optical signals that have not been electro-optically modulated, combines the multiple optical signals that have not been electro-optically modulated and the modulated optical signal into one optical signal, and transmits the signal to an optical fiber; the optical signal output by the combiner is transmitted via the optical fiber to an optoelectronic demodulation module; the optoelectronic demodulation module receives the optical signal output by the optical fiber, demodulates the optical signal output by the optical fiber, and outputs a radio frequency signal.

[0390] The radio frequency signal transmission method of the embodiment of the present application modulates an RF signal into an optical signal, combines the modulated optical signal with other unmodulated optical signals, and transmits them through an optical fiber. Ultimately, the RF signal modulated on the optical signal is demodulated at the output end of the optical fiber transmission. In other words, by using the other unmodulated optical signals as interference optical signals and transmitting them together with the modulated RF signal through the optical fiber, the optical signal spectrum can be broadened, the energy density of the light entering the fiber can be reduced, and the power of the optical signal incident on the fiber can be increased, thereby improving the transmission performance and efficiency of the RF signal.

[0391] For example, in some possible implementations, the method further includes: an optical signal generation module generating the multiple non-electro-optically modulated optical signals and transmitting the multiple non-electro-optically modulated optical signals to the combiner; a radio frequency signal generation module generating the radio frequency signal and transmitting the radio frequency signal to the electro-optical modulation module; and an optical amplifier receiving the optical signal output by the combiner, amplifying the power of the optical signal output by the combiner, and transmitting the power-amplified optical signal to the optical fiber. In this implementation, the power amplification by the optical amplifier can improve the transmission efficiency of the optical signal in the optical fiber.

[0392] For example, in some possible implementations, the method further includes: a reflected light power detection module detecting the reflected light power of multiple modulated optical signals transmitted in the optical fiber, and when the reflected light power is greater than or equal to a first threshold, sending a first signal to the feedback control unit; the feedback control unit receiving the first signal, generating a second signal based on the first signal, and sending the second signal to the optical signal generation module; the optical signal generation module receiving the second signal, and adjusting the wavelengths and / or quantity of the multiple non-electro-optically modulated optical signals generated based on the second signal. In this implementation, when the power of the optical signal incident on the optical fiber is greater than or equal to a preset SBS threshold power, the wavelengths and / or quantity of the multiple non-electro-optically modulated optical signals generated by the optical signal generation module are promptly adjusted to ensure that the power of the optical signal incident on the optical fiber is less than the SBS threshold power, thereby improving the stability of the optical signal incident on the optical fiber while increasing the power of the optical signal incident on the optical fiber.

[0393] For a description of various possible implementations and beneficial effects of the radio frequency signal transmission method provided in the embodiments of the present application, reference may be made to the description of the implementations related to Figures 13 and 14 above, which will not be repeated here for the sake of brevity.

[0394] An embodiment of the present application further provides a method for transmitting a radio frequency signal, which can be applied to the communication device 1700 provided in an embodiment of the present application. The method includes: an electro-optical modulation module receives a radio frequency signal, modulates the radio frequency signal onto an optical signal, obtains a modulated optical signal, and transmits the modulated optical signal to the combiner; the combiner receives the modulated optical signal and multiple optical signals that have not been electro-optically modulated, combines the multiple optical signals that have not been electro-optically modulated and the modulated optical signal into one optical signal, and transmits the optical signal to a third optical fiber; and the third optical fiber transmits the optical signal output by the combiner.

[0395] The radio frequency signal transmission method of the embodiment of the present application modulates an RF signal into an optical signal, combines the modulated optical signal with other unmodulated optical signals, and transmits the combined signal through an optical fiber. In other words, by treating the other unmodulated optical signals as interference optical signals and transmitting them together with the modulated RF signal through the optical fiber, the optical signal spectrum can be broadened, the energy density of the light entering the fiber can be reduced, and the power of the optical signal incident on the fiber can be increased, thereby improving the transmission performance and efficiency of the RF signal.

[0396] For a description of various possible implementations and beneficial effects of the radio frequency signal transmission method provided in the embodiments of the present application, reference may be made to the above description of the relevant implementations of the communication device 1700. For the sake of brevity, these descriptions will not be repeated here.

[0397] An embodiment of the present application also provides a method for transmitting a radio frequency signal, which can be applied to the communication device 1800 provided in an embodiment of the present application. The method includes: a fourth optical fiber receives and transmits an optical signal to an optoelectronic demodulation module, where the optical signal transmitted by the fourth optical fiber is obtained by combining multiple optical signals that have not been electro-optically modulated and an optical signal that has been electro-optically modulated into one optical signal, and the electro-optically modulated optical signal is obtained by modulating a radio frequency signal onto the optical signal; the optoelectronic demodulation module receives the optical signal output by the fourth optical fiber, and demodulates and outputs the radio frequency signal from the optical signal output by the fourth optical fiber.

[0398] The radio frequency signal transmission method of the embodiment of the present application modulates one RF signal into an optical signal, combines the modulated optical signal with other unmodulated optical signals into one signal, and transmits the combined signal through a fourth optical fiber. Finally, the RF signal modulated on the optical signal is demodulated at the output end of the fourth optical fiber. In other words, by treating the other unmodulated optical signals as interference optical signals and transmitting them together with the modulated RF signal through the optical fiber, the optical signal spectrum can be broadened, the energy density of the light entering the fiber can be reduced, and the power of the optical signal incident on the optical fiber can be increased, thereby improving the transmission performance and efficiency of the RF signal.

[0399] For a description of various possible implementations and beneficial effects of the radio frequency signal transmission method provided in the embodiments of the present application, reference may be made to the above description of the relevant implementations of the communication device 1800 , which will not be repeated here for the sake of brevity.

[0400] It should be understood that in various embodiments of the present application, the terms "first," "second," and so on are merely intended to indicate that multiple objects are distinct. For example, the terms "first wavelength division multiplexer" and "second wavelength division multiplexer" are merely intended to indicate different service servers. These terms should not affect the service servers themselves or their number, and should not impose any limitations on the embodiments of the present application.

[0401] It should also be understood that the division of the modes, situations, categories and embodiments in the embodiments of the present application is only for the convenience of description and should not constitute a special limitation. The features of various modes, categories, situations and embodiments can be combined without contradiction.

[0402] It should also be understood that the above description of the embodiments of the present application focuses on emphasizing the differences between the various embodiments. The same or similar points that are not mentioned can be referenced with each other. For the sake of brevity, they will not be repeated here.

[0403] It should also be understood that the division of the modules (units) within the RoF transmission system and various communication devices in the above implementations is merely a logical functional division. In actual implementation, these modules can be fully or partially integrated into a single physical entity, or physically separated. Furthermore, the modules within the RoF transmission system and various communication devices can be implemented entirely in hardware; some modules can also be implemented in software through processing elements, while others can be implemented in hardware. For example, each module can be a separate processing element or integrated into a single chip within the RoF transmission system or communication device.

[0404] In the several embodiments provided herein, it should be understood that the disclosed systems can be implemented in other ways. For example, the embodiments of the RoF transmission system and communication device described above are merely illustrative. For example, the module divisions described are merely logical functional divisions. Actual implementations may employ alternative divisions, such as combining or integrating multiple modules or components into another system, or omitting or disabling certain features. Furthermore, the couplings or direct couplings or communication connections shown or discussed may be indirect couplings or communication connections between devices or units, either through interfaces, electrical, mechanical, or other means.

[0405] The present application also provides a network device that can include any of the RoF transmission systems or communication devices provided in the above embodiments. For example, the network device can include the communication device 1500 and / or the communication device 1600 described above, or the network device can include the communication device 1700 and / or the communication device 1800 described above.

[0406] For example, the network device provided in the embodiment of the present application can be a device with wireless transceiver functions for communicating with a terminal device, or it can be a device for accessing a terminal device to a wireless network. The network device can be a node in a radio access network, which can also be called a base station, or a radio access network (RAN) node (or device). The network device can be an evolved base station (evolved Node B, eNB or eNodeB) in LTE; or a next generation node B (gNB) in a 5G network or a base station in a future evolved public land mobile network (PLMN), a broadband network service gateway (BNG), an aggregation switch or a non-third generation partnership project (3GPP) access device, etc.

[0407] Optionally, the network equipment in the embodiments of the present application may also include various forms of base stations, such as: macro base stations, micro base stations (also called small stations), relay stations, equipment that implements base station functions in communication systems evolved after 5G, transmission points (transmitting and receiving points, TRP), transmitting points (transmitting points, TP), mobile switching centers, and equipment that assumes base station functions in device-to-device (D2D), vehicle-to-everything (V2X), and machine-to-machine (M2M) communications, etc., and may also include centralized units (CU) and distributed units (DU) in cloud radio access network (C-RAN) systems, and network equipment in non-terrestrial network (NTN) communication systems, that is, they can be deployed on high-altitude platforms or satellites. The embodiments of the present application do not specifically limit this.

[0408] Figure 19 is a structural diagram of a network device 1900 provided in an embodiment of the present application. The network device 1900 includes one or more radio frequency units, such as a remote radio unit (RRU) 1901 and one or more baseband units (BBU) (also referred to as digital units, DU) 1902. The RRU 1901 can be called a transceiver unit, a transceiver, a transceiver circuit, or a transceiver, etc., and may include at least one antenna 19011 and a radio frequency unit 19012. The RRU 1901 is mainly used for receiving and transmitting radio frequency signals and converting radio frequency signals into baseband signals, for example, for sending signaling messages to terminal devices. The BBU 1902 is mainly used for baseband processing, controlling the base station, etc. The RRU 1901 and the BBU 1902 can be physically set together or physically separated, that is, a distributed base station.

[0409] The BBU 1902 is the control center of the base station, which can also be called a processing unit. It is mainly used to perform baseband processing functions such as channel coding, multiplexing, modulation, spread spectrum, etc. For example, the BBU (processing unit) 1902 can be used to control the base station 190 to execute the operation process of the network device in the above method embodiment.

[0410] For example, for any of the RoF transmission systems or communication devices provided in the above embodiments, the BBU 1902 may be provided with one or more of an electro-optical modulation module, an optical signal generation module, an RF signal generation module, an optical amplifier, an optical circulator, a reflected light power detection module, a feedback control unit, a first wavelength division multiplexer, a wavelength division multiplexer, and a combiner. The RRU 1901 may be provided with one or more of an electro-optical demodulation module and a second wavelength division multiplexer. Optical fibers are used to connect the BBU and RRU. Multiple optical signals, such as multiple modulated optical signals or multiple optical signals that have not been electro-optically modulated and modulated optical signals, may be transmitted in the optical fibers.

[0411] In one example, the BBU 1902 may be composed of one or more single boards, and the multiple single boards may jointly support a wireless access network of a single access standard (such as an LTE system or a 5G system), or may respectively support wireless access networks of different access standards. The BBU 1902 also includes a memory 19021 and a processor 19022. The memory 19021 is used to store necessary instructions and data. For example, the memory 19021 stores the codebook in the above embodiment, etc. The processor 19022 is used to control the base station to perform necessary actions, such as controlling the base station to execute the operation process of the network device in the above method embodiment. The memory 19021 and the processor 19022 can serve one or more single boards. That is, a memory and a processor can be set separately on each single board. Alternatively, multiple single boards may share the same memory and processor. In addition, necessary circuits may be set on each single board.

[0412] In one possible implementation, with the development of system-on-chip (SoC) technology, all or part of the functions of parts 1902 and 1901 can be implemented using SoC technology. For example, they can be implemented using a base station function chip that integrates a processor, memory, antenna interface, and other components. Programs for base station-related functions are stored in the memory, and the processor executes the programs to implement the base station-related functions. Optionally, the base station function chip can also read memory external to the chip to implement the base station-related functions.

[0413] It should be understood that the structure of the network device illustrated in Figure 19 is only one possible form and should not constitute any limitation to the embodiments of the present application. The present application does not exclude the possibility of other forms of base station structures that may appear in the future.

[0414] In one example, the unit in any of the above devices may be one or more integrated circuits configured to implement the above method, such as one or more application specific integrated circuits (ASICs), or one or more digital signal processors (DSPs), or one or more field programmable gate arrays (FPGAs), or a combination of at least two of these integrated circuit forms. For another example, when the unit in the device can be implemented in the form of a processing element scheduler, the processing element may be a general-purpose processor, such as a central processing unit (CPU) or other processor that can call a program. For another example, these units can be integrated together and implemented in the form of a system-on-a-chip (SOC).

[0415] It should be understood that in the embodiments of the present application, the processor in the embodiments of the present application may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc.

[0416] It should also be understood that the memory in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of random access memory (RAM) are available, such as static RAM (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), and direct rambus RAM (DR RAM).

[0417] The present invention also provides a computer-readable medium for storing computer program code, wherein the computer program includes instructions for executing any of the radio frequency signal transmission methods provided in the present invention. The computer-readable medium may be ROM or RAM, which is not limited in the present invention.

[0418] The present application also provides a computer program product, which includes instructions. When the instructions are executed, a communication device or a network device performs the operation of any radio frequency signal transmission method provided in the embodiments of the present application.

[0419] The present application also provides a system-on-chip (SoC), comprising a processing unit and a communication unit. The processing unit may be, for example, a processor, and the communication unit may be, for example, an input / output interface, a pin, or a circuit. The processing unit may execute computer instructions to cause the chip within the communication device to perform any of the radio frequency signal transmission methods provided in the embodiments of the present application.

[0420] Optionally, any one of the communication devices provided in the above embodiments of the present application may include the system chip.

[0421] Optionally, the computer instructions are stored in a storage unit.

[0422] Optionally, the storage unit is a storage unit within the chip, such as a register, cache, etc. The storage unit can also be a storage unit located outside the chip within the terminal, such as a ROM or other type of static storage device that can store static information and instructions, RAM, etc. The processor mentioned in any of the above can be a CPU, a microprocessor, an ASIC, or one or more integrated circuits for controlling the execution of the program of the above-mentioned method for main system information transmission. The processing unit and the storage unit can be decoupled and respectively set on different physical devices, and connected by wired or wireless means to implement the respective functions of the processing unit and the storage unit to support the system chip to implement the various functions in the above-mentioned embodiments. Alternatively, the processing unit and the memory can also be coupled on the same device.

[0423] The terms "system" and "network" are often used interchangeably in this document. The term "and / or" is simply a description of an association between related objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " generally indicates an "or" relationship between the related objects.

[0424] Various objects such as various messages / information / equipment / network elements / systems / devices / actions / operations / processes / concepts that may appear in this application are named. It can be understood that these specific names do not constitute a limitation on the relevant objects. The names assigned may change with factors such as scenarios, contexts or usage habits. The understanding of the technical meaning of the technical terms in this application should be mainly determined from the functions and technical effects embodied / executed in the technical solutions.

[0425] Those skilled in the art will appreciate that the methods in the embodiments of the present application can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, they can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer programs or instructions. When the computer program or instruction is loaded and executed on a computer, the process or function described in the embodiments of the present application is executed in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer program or instruction can be stored in a computer-readable storage medium or transmitted via the computer-readable storage medium. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server that integrates one or more available media.

[0426] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0427] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the unit is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0428] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0429] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0430] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (such as a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage media include: USB flash drives, mobile hard drives, read-only memories (ROMs), and random access memories.

[0431] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A communication device, characterized in that: The communication device includes: an electro-optical modulation module and a first optical fiber, The electro-optical modulation module is configured to receive a radio frequency signal and multiple optical signals, modulate the radio frequency signal onto the multiple optical signals to obtain multiple modulated optical signals, and transmit the multiple modulated optical signals to the first optical fiber; The first optical fiber is used to transmit the multiple modulated optical signals.

2. The communication device according to claim 1, characterized in that The communication device further includes: an optical signal generating module, a radio frequency signal generating module and an optical amplifier, wherein: The optical signal generating module is used to generate the multiple optical signals and transmit the multiple optical signals to the electro-optical modulation module; The radio frequency signal generating module is used to generate the radio frequency signal and transmit the radio frequency signal to the electro-optical modulation module; The optical amplifier is used to receive the multiple modulated optical signals output by the electro-optical modulation module, amplify the power of the multiple modulated optical signals, and transmit the multiple modulated optical signals after power amplification to the first optical fiber.

3. The communication device according to claim 2, characterized in that The communication device further comprises: an optical circulator, a reflected light power detection module and a feedback control unit; The first port of the optical circulator is connected to the output end of the optical amplifier, the second port of the optical circulator is connected to the input end of the first optical fiber, the third port of the optical circulator is connected to the input end of the reflected light power detection module, the output end of the reflected light power detection module is connected to the input end of the feedback control unit, and the output end of the feedback control unit is connected to the optical signal generating module; The reflected light power detection module is configured to detect the reflected light power of the multiple modulated optical signals transmitted in the first optical fiber, and send a first signal to the feedback control unit when the reflected light power is greater than or equal to a first threshold; The feedback control unit is configured to receive the first signal, generate a second signal according to the first signal, and send the second signal to the optical signal generating module; The optical signal generating module is configured to receive the second signal and adjust the wavelengths and / or quantities of the generated multiple optical signals according to the second signal.

4. The communication device according to claim 2 or 3, characterized in that The radio frequency signal generating module is used to generate N radio frequency signals, the electro-optical modulation module includes N electro-optical modulation submodules, the optical signal generating module generates M optical signals, and the communication device further includes: a first demultiplexer and a wavelength division multiplexer, wherein, The first demultiplexer is configured to receive M optical signals generated by the optical signal generating module, and decompose the M optical signals generated by the optical signal generating module into N channels, where M is an integer greater than 1, the i-th channel includes Ki optical signals, and i is an integer greater than or equal to 1 and less than or equal to N; an i-th electro-optical modulation submodule, configured to receive the i-th radio frequency signal generated by the radio frequency signal generation module and the Ki optical signals included in the i-th channel, and modulate the i-th radio frequency signal onto the Ki optical signals included in the i-th channel to obtain Ki modulated optical signals; the N electro-optical modulation submodules output Q modulated optical signals, and the N electro-optical modulation submodules transmit the Q modulated optical signals to the wavelength division multiplexer, where Q is an integer greater than or equal to 1 and less than or equal to M; The wavelength division multiplexer is used to receive the Q modulated optical signals, and combine the Q modulated optical signals and transmit them to the optical amplifier.

5. The communication device according to any one of claims 2 to 4, characterized in that The optical signal generating module includes one of the following: An ultra-wideband optical frequency comb generation module based on a mode-locked laser, an optical signal generation module based on the nonlinear effect of an optical fiber, an optical signal generation module based on an optoelectronic oscillator, an optical signal generation module based on a microring resonator, or an optical signal generation module based on an electro-optical modulator. The communication device according to claim 4 , wherein: When the optical signal generating module includes an ultra-wideband optical frequency comb generating module, the first de-wavelength division multiplexer decomposes the M optical signals generated by the optical signal generating module into N channels, the number of optical signals included in different channels in the N channels is the same or different, and among the multiple optical signals included in each channel, the wavelength difference between two adjacent optical signals is the same.

7. The communication device according to any one of claims 2 to 6, characterized in that: The wavelengths of the multiple optical signals generated by the optical signal generating module are in a low dispersion band.

8. The communication device according to any one of claims 1 to 7, characterized in that The first optical fiber also includes a dispersion compensator, which is used to compensate for the dispersion of the modulated optical signal during transmission in the first optical fiber.

9. The communication device according to any one of claims 2 to 8, characterized in that Among the multiple optical signals generated by the optical signal generating module, the wavelength interval Δλ between two adjacent optical signals satisfies the following condition: Among them, n is a positive integer, f RFi represents the frequency of the radio frequency signal modulated onto the multiple optical signals, D(λ) represents the dispersion coefficient of the optical fiber, and L represents the length of the first optical fiber.

10. The communication device according to any one of claims 1 to 9, characterized in that: The wavelengths of the multiple optical signals are different.

11. A communication device, characterized in that: The communication device includes: a second optical fiber and an optoelectronic demodulation module; The second optical fiber is used to receive and transmit a plurality of modulated optical signals to the optoelectronic demodulation module, wherein the plurality of modulated optical signals are obtained by modulating a radio frequency signal onto the plurality of optical signals; The optoelectronic demodulation module is used to receive a plurality of modulated optical signals output by the second optical fiber, and demodulate and output the radio frequency signal from the plurality of modulated optical signals.

12. The communication device according to claim 11, wherein: The optoelectronic demodulation module includes N optoelectronic demodulation submodules, the multiple modulated optical signals are obtained by modulating N radio frequency signals onto multiple optical signals, and the communication device further includes: a second de-wavelength division multiplexer; The second wavelength division multiplexer is configured to receive the multiple modulated optical signals output by the second optical fiber, decompose the multiple modulated optical signals output by the second optical fiber into N optical signals, and transmit the i-th optical signal to the i-th optoelectronic demodulation submodule in the optoelectronic demodulation module, wherein the i-th optical signal includes Ki modulated optical signals, where i is an integer greater than or equal to 1 and less than or equal to N; The i-th optoelectronic demodulation submodule in the optoelectronic demodulation module is used to receive the i-th optical signal output by the second de-wavelength division multiplexer and demodulate the i-th radio frequency signal from the i-th optical signal. The optoelectronic demodulation module is used to output the N radio frequency signals.

13. The communication device according to claim 12, wherein: Among the N optical signals, different optical signals include the same or different numbers of optical signals, and among the Ki modulated optical signals included in the i-th optical signal, the wavelength difference between two adjacent optical signals is the same.

14. The communication device according to any one of claims 11 to 13, characterized in that: The second optical fiber further includes a dispersion compensator, which is used to compensate for the dispersion of the multiple modulated optical signals during transmission in the second optical fiber.

15. The communication device according to any one of claims 11 to 14, characterized in that: The wavelengths of the multiple optical signals are different.

16. A radio frequency over light transmission system, characterized in that: The system comprises: the communication device according to any one of claims 1 to 10, and the communication device according to any one of claims 11 to 15.

17. A communication device, characterized in that: The communication device includes: an electro-optical modulation module, a combiner and a third optical fiber, wherein: The electro-optical modulation module is used to receive a radio frequency signal, modulate the radio frequency signal onto an optical signal to obtain a modulated optical signal, and transmit the modulated optical signal to the combiner; The combiner is configured to receive the modulated optical signal and a plurality of optical signals that have not been electrically-optically modulated, combine the plurality of optical signals that have not been electrically-optically modulated and the modulated optical signal into one optical signal, and transmit the combined optical signal to the third optical fiber. The third optical fiber is used to transmit the optical signal output by the combiner.

18. The communication device according to claim 17, wherein: The communication device further includes: an optical signal generating module, a radio frequency signal generating module and an optical amplifier, wherein: The optical signal generating module is configured to generate the plurality of optical signals that have not been electrically-optically modulated, and transmit the plurality of optical signals that have not been electrically-optically modulated to the combiner; The radio frequency signal generating module is used to generate the radio frequency signal and transmit the radio frequency signal to the electro-optical modulation module; The optical amplifier is used to receive the optical signal output by the combiner, amplify the power of the optical signal output by the combiner, and transmit the power-amplified optical signal to the third optical fiber.

19. The communication device according to claim 18, wherein: The communication device further comprises: an optical circulator, a reflected light power detection module and a feedback control unit; The first port of the optical circulator is connected to the output end of the optical amplifier, the second port of the optical circulator is connected to the input end of the third optical fiber, the third port of the optical circulator is connected to the input end of the reflected light power detection module, the output end of the reflected light power detection module is connected to the input end of the feedback control unit, and the output end of the feedback control unit is connected to the optical signal generating module; The reflected light power detection module is configured to detect the reflected light power of the optical signal transmitted in the third optical fiber, and send a first signal to the feedback control unit when the reflected light power is greater than or equal to a first threshold; The feedback control unit is configured to receive the first signal, generate a second signal according to the first signal, and send the second signal to the optical signal generating module; The optical signal generating module is configured to receive the second signal and adjust the wavelengths and / or quantities of the generated plurality of optical signals that are not electro-optically modulated according to the second signal.

20. The communication device according to any one of claims 17 to 19, characterized in that: The electro-optical modulation module includes: a direct modulation electro-optical modulation module or an indirect modulation electro-optical modulation module; The direct modulation electro-optical modulation module is used to generate the optical signal and modulate the radio frequency signal, and transmit the modulated optical signal to the combiner; The optical modulation module of the indirect modulation method includes a light source generating module and an electro-optical modulation sub-module. The light source generating module is used to generate an optical signal. The electro-optical modulation sub-module is used to modulate the radio frequency signal onto the optical signal generated by the light source to obtain a modulated optical signal, and transmit the modulated optical signal to the combiner.

21. The communication device according to claim 20, wherein: When the electro-optical modulation module includes the electro-optical modulation module of the indirect modulation mode, the wavelength of the optical signal generated by the light source generating module is the same as or different from the wavelength of any one of the multiple optical signals that have not been electro-optically modulated.

22. The communication device according to any one of claims 18 to 21, characterized in that: The optical signal generating module includes one of the following: An ultra-wideband optical frequency comb generation module based on a mode-locked laser, an optical signal generation module based on the nonlinear effect of an optical fiber, an optical signal generation module based on an optoelectronic oscillator, an optical signal generation module based on a microring resonator, or an optical signal generation module based on an electro-optical modulator.

23. The communication device according to any one of claims 18 to 22, characterized in that: The wavelengths of the multiple optical signals generated by the optical signal generating module and not subjected to electro-optical modulation are located in a low dispersion band.

24. The communication device according to any one of claims 17 to 23, characterized in that The third optical fiber also includes a dispersion compensator, which is used to compensate for the dispersion of the optical signal during transmission in the third optical fiber.

25. The communication device according to any one of claims 17 to 24, characterized in that The wavelengths of the multiple optical signals that are not electro-optically modulated are different.

26. A communication device, characterized in that: The communication device includes: a fourth optical fiber and an optoelectronic demodulation module; The fourth optical fiber is used to receive and transmit an optical signal to the optoelectronic demodulation module, wherein the optical signal transmitted by the fourth optical fiber is obtained by combining a plurality of optical signals that have not been electro-optically modulated and an optical signal that has been electro-optically modulated into one optical signal, and the electro-optically modulated optical signal is obtained by modulating a radio frequency signal onto the optical signal; The optoelectronic demodulation module is configured to receive the optical signal output by the fourth optical fiber, and demodulate and output the radio frequency signal from the optical signal output by the fourth optical fiber.

27. The communication device according to claim 26, characterized in that The wavelengths of the multiple optical signals that have not been electro-optically modulated are in a low dispersion band.

28. The communication device according to claim 26 or 27, characterized in that The fourth optical fiber further includes a dispersion compensator, which is used to compensate for the dispersion of the optical signal during transmission in the fourth optical fiber.

29. The communication device according to any one of claims 26 to 28, characterized in that The wavelengths of the multiple optical signals that are not electro-optically modulated are different.

30. A radio frequency transmission system over light, characterized in that: The system comprises: the communication device according to any one of claims 17 to 25, and the communication device according to any one of claims 26 to 29.

31. A network device, characterized in that: The network device includes: the communication device according to any one of claims 1 to 10, and / or the communication device according to any one of claims 11 to 15.

32. A network device, characterized in that: The network device includes: the communication device according to any one of claims 17 to 25, and / or the communication device according to any one of claims 26 to 29.

33. A network device, characterized in that: The network device includes: the radio frequency over fiber transmission system according to claim 16, and / or the radio frequency over fiber transmission system according to claim 30.

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