Multi-order complex signal generation method and demodulation device based on optical delay synchronization and power control

Abstract

The invention discloses a multi-order complex signal generation method and demodulation device based on optical delay synchronization and power control. The multi-order complex signal generation device comprises a baseband signal generator, a photoelectric oscillator, two optical delay synchronous synthesis systems and a radio frequency emission module, and obtains a high-frequency carrier multi-order complex signal which can be used for long-distance high-speed wireless transmission. And the signal receiving and demodulating device is used for receiving the high-frequency carrier multi-order complex signal, carrying out optical domain processing such as photon down-conversion and delay synchronization and electric domain processing such as photoelectric detection and low-pass filtering, and sampling and demodulating to obtain an original baseband signal. According to the device, electric domain operations such as baseband signal frequency mixing, higher-speed electric signal generation, multi-path electric power synthesis and radio-frequency signal down-conversion are transferred to an optical domain by using a relatively low-speed electronic device, so that the requirement on the electronic device is reduced; according to the device, through precise optical delay control, the problem caused by desynchrony between devices is solved, odd-bit and even-bit signals are obtained through sampling at the sampling rate of 1 / 2 in a time division multiplexing mode, and the requirement of electric sampling equipment is lowered. An original signal is obtained through a demodulation algorithm, and the transmission error rate can be lower than 10 <-6 >.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic communication, and particularly relates to a method for generating multi-order complex signals based on optical delay synchronization and power control and a demodulation device. Background Art

[0002] Digital communication plays an important role in modern communication systems. However, with the continuous increase in data rate, traditional electronic devices are facing increasingly serious bottlenecks. At high frequencies, electronic devices (such as high-speed amplifiers, modems, signal processing chips, etc.) have physical and electrical performance limitations. These devices usually need to convert electrical signals, which are restricted by aspects such as bandwidth, response speed, and power consumption. With the increase in data rate, traditional electronic devices are difficult to maintain efficient performance, resulting in bottlenecks in signal processing, amplification, transmission, etc., restricting the overall throughput of the communication system. In order to break through this bottleneck, the proposal of optical domain digital modulation addresses the bottleneck of traditional electronic devices in high-frequency signal processing. Optical domain modulation utilizes the advantages of fiber optic communication systems, leveraging the high-speed transmission characteristics of optical signals, low loss, and large bandwidth of optical fibers, thus solving the performance bottleneck of electronic devices at high data rates.

[0003] With the rapid development of microwave photonics: through optoelectronic conversion technology, optical signals can be efficiently interfaced with electronic systems; photonic devices (such as lasers, optical modulators, photodetectors, etc.) can respond and process information within an extremely short time scale, far exceeding the response speed of traditional electronic devices. This enables optical domain digital communication to operate at extremely high data rates without being restricted by the response speed of electronic devices. Moreover, the optoelectronic oscillator, an important invention in the field of microwave photonics, can provide high-quality optical and electrical signals and can up-convert baseband signals to radio frequency for transmission. Optical delay synchronization can synchronously convert electrical domain baseband signals to optical domain delay and can also transfer the phase synchronization in the radio frequency domain to optical domain delay matching.

[0004] The transmission capacity and efficiency of fiber optic communication systems can be achieved through techniques such as power combining, wavelength division multiplexing, time division multiplexing, etc. to realize a higher-speed optical transmission system. Complex high-order signal modulation formats (such as QPSK, 16QAM, etc.) can also be encoded by the phase, amplitude, or frequency of optical signals in the optical domain, thereby improving the efficiency and rate of optical transmission. Summary of the Invention

[0005] In view of the above, the present invention provides a method for generating multi-order complex signals based on optical delay synchronization and power control and a demodulation device, which can realize the synthesis of four 1x-speed digital modulation signals into one 4x-speed multi-order signal and the reverse demodulation of one 4x-speed multi-order signal into four 1x-speed digital signals. The system includes baseband signal generation, a multi-channel signal synthesis and transmission optical link, a signal reception optical link, a signal demodulation method, and a device.

[0006] The baseband signal generation section needs to process the original data to generate the electrical signal to be transmitted. First, the binary data stream D i is subjected to differential decoding (301) to obtain the binary code S i , which is the binary sequence to be transmitted. On this basis, through an electrical signal generation module such as FPGA (109), S i is used to generate a unipolar electrical signal V i (t) (302) with a symbol period of T, a frequency of f, and a signal amplitude equal to half the wave voltage of the modulator used.

[0007] The multi-channel signal synthesis optical link includes: an optoelectronic oscillator, two optical delay synchronization synthesis systems, and a radio frequency transmission module. The optoelectronic oscillator is used to generate an optical carrier and sideband signals, which are used as the carrier for the subsequent system and to generate radio frequency signals for transmission; the optical delay synchronization synthesis system is used to synthesize the dual-channel baseband signals into a single frequency-doubled signal through optical delay synchronization; the delay systems synthesize higher-order signals through power control and transmit them after beating to radio frequency, obtaining a high-frequency carrier multi-order complex signal that can be used for long-distance high-speed wireless transmission.

[0008] The optoelectronic oscillator loop includes a laser (101), an electro-optic modulator (102), an optical coupler (103), a low-loss single-mode optical fiber (104), a photodetector (105), an electrical filter (106), and an electrical amplifier (107) to form a positive feedback loop to form a stable oscillation. The electro-optic modulator operates at the quadrature point to achieve double-sideband modulation of the oscillation signal.

[0009] The optical delay synchronization synthesis system realizes the synthesis of the dual-channel baseband signals. The optical signals output by the optoelectronic oscillator are used as the optical carriers for the two systems respectively through a 1×2 optical coupler (108) with a splitting ratio of 50:50. Then, it is divided into two paths through a 1×2 optical coupler (110) with a splitting ratio of 50:50. One path is delayed by the optical fiber delay line (111) and then injected into the electro-optic modulator (112), and the other path is first injected into the electro-optic modulator (113) and then delayed by the optical fiber delay line (114). The two paths are synthesized through a 2×1 coupler (115) to obtain a single signal. Among them, on the basis of the optical fiber delay lines (111) and (114) being used to match the dual-channel delay difference of the couplers (110) and (115), it is required to achieve a time difference of T / 2 between the modulation electrical signals of the electro-optic modulators (112) and (113).

[0010] The two optical delay synchronization synthesis systems achieve link synthesis through power control of the variable optical attenuator (123), and use the optical fiber delay line (116) to achieve dual-channel synchronization. Finally, a modulated signal is synthesized through a 2×1 optical coupler (124).

[0011] The synthesized signal is amplified by the EDFA (125), filtered by the optical band-pass filter (126), and then input into the photodetector (127). After converting the optical signal into a radio frequency signal, it is transmitted. The carrier of this radio frequency signal has the same frequency as the electrical signal obtained from the optoelectronic oscillator.

[0012] Furthermore, the modulation bandwidth requirements of the electro-optic modulators (112), (113), (119), and (120) exceed twice the baseband signal rate, i.e., 2f. The electro-optic modulator (112) modulates the signal V 1 (t), the electro-optic modulator (113) modulates the signal V 2 (t), the electro-optic modulator (119) modulates the signal V 3 (t), and the electro-optic modulator (120) modulates the signal V 4 (t).

[0013] The multi-order complex signal receiving and signal demodulation method and device include receiving a high-frequency carrier multi-order complex signal, amplifying it through a radio frequency amplifier, down-converting it to the baseband using photon technology, realizing dual-channel time-division multiplexing using dual-channel optical delay, and respectively sampling to obtain odd and even bit signals through photoelectric detection, low-pass filtering, etc., and obtaining multiple original signals through a demodulation algorithm.

[0014] After receiving the multi-order complex radio frequency signal (208), it is amplified by the radio frequency amplifier (209) and then down-converted using the microwave photon technology of a cascaded modulator. The optoelectronic oscillator loop is used in the front stage, and the electro-optic modulator (210) is used in the rear stage to load the signal radio frequency signal near the sideband. The signal is divided into two paths, and the optical fiber delay line (212) is used to control the time domain difference between the two paths of signals to be T / 2. The two paths of signals are respectively sent into the photodetectors (213) and (215), and then the target signals are extracted through the low-pass filters (214) and (216). The data obtained by sampling (217) and (218) is sent into the demodulation algorithm to restore the original data.

[0015] The optoelectronic oscillator loop at the receiving end has the same structure as the optoelectronic oscillator at the transmitting end, including a laser (201), an electro-optic modulator (202), an optical coupler (203), a low-loss single-mode optical fiber (204), a photodetector (205), an electrical filter (206), and an electrical amplifier (207) to form a positive feedback loop to form a stable oscillation. The difference lies in that the frequencies of the oscillation signals are different, and the electro-optic modulator works at the minimum point to achieve carrier suppression double-sideband modulation of the oscillation signal.

[0016] Furthermore, set the signal sampling rate Nf, where N is an integer, and the minimum value can be 1, corresponding to the factor of the downsampling (401). By adjusting the sampling delay, the sampling points can be located at the midpoint moment position of each symbol period. The demodulation algorithm includes the following steps:

[0017] (1) Sample the two-channel signals after delay synchronization through optoelectronic conversion respectively, output the odd and even bits of the corresponding signals, and perform downsampling (401) on the sampling results so that there is only one data within each symbol period.

[0018] (2) Perform four-level digital mapping (402) on the two-channel signals.

[0019] (3) Divide the two-channel odd and even signals into high and low bit data through serial-to-parallel conversion (403), a total of four groups of data.

[0020] (4) Analyze the odd and even bit data of the high and low signals respectively, and demodulate (404) to obtain the original four-channel signals.

[0021] The demodulation algorithm includes the following steps:

[0022] The specific algorithm logic for demodulating to the original data (404) is as follows: Take the odd and even signals of the high or low bits, and compare bit by bit (404-4) the even signal (404-1) and the odd signal (404-2) at the same time sequence: If the signals are not equal, the corresponding original one-channel data is 1 (404-5); If the signals are equal, the corresponding original one-channel data is 0 (404-6). Compare bit by bit (404-8) the even signal (404-1) and the odd signal of the next time sequence bit (404-3): If the signals are equal, the corresponding original two-channel data is 0 (404-9); If the signals are not equal, the corresponding original two-channel data is 1 (404-11). Obtain the original one-channel data (404-7) and the original two-channel data (404-11) through the demodulation process. Similarly, the original three-channel data and four-channel data can be obtained.

[0023] Compared with the background technology, the beneficial effects of the present invention are: The generating device uses precise optical fiber delay to replace electrical delay, misplaces the low-speed signals in the electrical domain by half a period through optical delay synchronization, and realizes the generation of a frequency-doubled signal through an optical modulation link; On this basis, through power control, intensity synthesis is achieved to a 4-fold multi-order signal; And the up-conversion of the baseband signal is realized and transmitted through an optoelectronic oscillator. The receiving and demodulating module, on the basis of receiving the radio frequency signal, is amplified by a radio frequency amplifier, down-converted to the baseband through photon technology, separates the odd and even bit signals by using dual-channel optical delay, and then through optoelectronic detection, low-pass filtering and other processing, samples the odd and even bit signals respectively, and obtains the original signal through the demodulation algorithm, and the transmission error rate is lower than 10 -6 . This device uses relatively low-speed electronic devices to transfer the electrical domain operations such as mixing of the baseband signal, generation of higher-speed electrical signals, multi-channel electrical power synthesis, and down-conversion of the radio frequency signal to the optical domain, reducing the requirements for electronic devices; This device compensates for the problems caused by the out-of-synchronization between devices through precise optical delay control, and uses the time-division multiplexing method to sample the odd and even bit signals respectively at a sampling rate of 1 / 2, reducing the requirements for electrical sampling equipment. Description of the Drawings

[0024] Figure 1 This is a schematic diagram of the specific optical - electrical link structure at the signal generation end of the device of the present invention.

[0025] In the figure: 101 - laser, 102 - electro - optical modulator, 103 - 1×2 optical coupler, 104 - low - loss single - mode optical fiber, 105 - photodetector, 106 - electrical band - pass filter, 107 - electrical amplifier, 108 - 1×2 optical coupler, 109 - FPGA, 110 - 1×2 optical coupler, 111 - optical fiber delay line, 112 - electro - optical modulator, 113 - electro - optical modulator, 114 - optical fiber delay line, 115 - 2×1 optical coupler, 116 - optical fiber delay line, 117 - 1×2 optical coupler, 118 - optical fiber delay line, 119 - electro - optical modulator, 120 - electro - optical modulator, 121 - optical fiber delay line, 122 - 2×1 optical coupler, 123 - optical attenuator, 124 - 2×1 optical coupler, 125 - erbium - doped fiber amplifier, 126 - optical band - pass filter, 127 - photodetector, 128 - transmitting antenna.

[0026] Figure 2 This is a schematic diagram of the specific optical - electrical link structure at the receiving end of the device of the present invention.

[0027] In the figure: 201 - laser, 202 - electro - optical modulator, 203 - 1×2 optical coupler, 204 - low - loss single - mode optical fiber, 205 - photodetector, 206 - electrical band - pass filter, 207 - electrical amplifier, 208 - receiving antenna, 209 - RF amplifier, 210 - electro - optical modulator, 211 - 1×2 optical coupler, 212 - optical fiber delay line, 213 - photodetector, 214 - electrical low - pass filter, 215 - photodetector, 216 - electrical low - pass filter, 217 - digital sampler, 218 - digital sampler.

[0028] Figure 3 This is a block diagram of the pre - order data processing and electrical signal generation at the signal generation end of the device of the present invention.

[0029] In the figure: 301 - binary differential coding, 302 - FPGA electrical signal generation.

[0030] Figure 4 This is a block diagram of the data demodulation processing at the signal receiving end of the device of the present invention.

[0031] In the figure: 401 - decimation, 402 - digital mapping, 403 - serial - to - parallel conversion, 404 - high / low - order signal demodulation.

[0032] Figure 5 This is a flow chart of the operation algorithm for high / low - order signal demodulation (404) at the signal receiving end of the device of the present invention.

[0033] In the figure: 401-1 - even (bit) signal, 404-2 - odd (bit) signal, 404-3 - timing delay, 404-4 - compare the even signal and the odd signal at the same timing, 404-5 - if not equal, assign the original one-way signal as 1, 404-6 - if equal, assign the original one-way signal as 0, 404-7 - obtain the original one-way signal, 404-8 - compare the even signal at the same timing and the odd signal at the next timing bit, 404-9 - if equal, assign the original two-way signal as 0, 404-10 - if not equal, assign the original one-way signal as 1, 404-11 - obtain the original two-way signal.

[0034] Figure 6 This is the simulation result diagram of the signal generation end of the device of the present invention.

[0035] Figure 7 This is the schematic diagram of the simulation demodulation at the receiving end of the device of the present invention. Detailed implementation manners

[0036] In order to describe the present invention more specifically, the technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0037] Figure 1 This is the specific structural schematic diagram of the optical and electrical link at the signal generation end of the device of the present invention. The generating device includes an optical and electrical oscillator, baseband signal generation, two optical delay synchronous synthesis systems, and a radio frequency transmitting module. The optical and electrical oscillator includes: 101 - laser, 102 - electro-optic modulator, 103 - 1×2 optical coupler, 104 - low-loss single-mode optical fiber, 105 - photodetector, 106 - electrical band-pass filter, 107 - electrical amplifier. The baseband signal generation uses 109 - FPGA to convert data into an electrical signal, and the signal pre-processing flowchart is as Figure 3 shown. The first optical delay synchronous synthesis system includes: 110 - 1×2 optical coupler, 111 - fiber delay line, 112 - electro-optic modulator, 113 - electro-optic modulator, 114 - fiber delay line, 115 - 2×1 optical coupler; the second optical delay synchronous synthesis system includes: 117 - 1×2 optical coupler, 118 - fiber delay line, 119 - electro-optic modulator, 120 - electro-optic modulator, 121 - fiber delay line, 122 - 2×1 optical coupler. The two synthesis systems are synthesized through 116 - fiber delay line, 123 - optical attenuator, 124 - 2×1 optical coupler. The radio frequency transmitting module includes: 125 - erbium-doped fiber amplifier, 126 - optical band-pass filter, 127 - photodetector, 128 - transmitting antenna.

[0038] Figure 2This is a schematic diagram of the specific structure of the optoelectronic link at the receiving end of the device of the present invention. The receiving device includes parts such as receiving radio frequency signals, photon downconversion, optical delay synchronization, and electrical sampling. The radio frequency signal is received and processed through 208 - receiving antenna, 209 - radio frequency amplifier. The photon downconversion module includes: 201 - laser, 202 - electro-optic modulator, 203 - 1×2 optical coupler, 204 - low-loss single-mode optical fiber, 205 - photodetector, 206 - electrical band-pass filter, 207 - electrical amplifier. The optical delay synchronization part includes: 211 - 1×2 optical coupler, 212 - fiber delay line. The electrical sampling includes: 215 - photodetector, 216 - electrical low-pass filter, 217 - digital sampler, 218 - digital sampler. The processing method of the sampled signal is as Figure 4 shown, and the processed data is sent to the demodulation algorithm. The flowchart of the demodulation algorithm is as Figure 5 shown.

[0039] The signal preprocessing operation block diagram of the baseband signal generation part is as Figure 3 shown. For the binary data stream D i perform differential coding (301) to obtain the binary code S i , and this signal is the binary sequence to be transmitted. On this basis, through an electrical signal generation module such as FPGA (109), S i is generated into a unipolar electrical signal V i (t) (302) with a symbol period of T, a frequency of f, and a signal amplitude of the half-wave voltage of the used modulator.

[0040] The multi-channel signal synthesis optical link includes: an optoelectronic oscillator, two optical delay synchronization synthesis systems, and a radio frequency transmission module. The optoelectronic oscillator is used to generate an optical carrier and sideband signals, which are used as the carrier of the subsequent system and to generate radio frequency signals for transmission; the optical delay synchronization synthesis system is used to synthesize a double-channel baseband signal into a frequency-doubled signal through optical delay synchronization; the delay systems synthesize higher-order signals through power control, beat to radio frequency and then transmit to obtain a high-frequency carrier multi-order complex signal that can be used for long-distance high-speed wireless transmission.

[0041] The optoelectronic oscillator loop includes a laser (101), an electro-optic modulator (102), an optical coupler (103), a low-loss single-mode optical fiber (104), and a photodetector (105) connected in sequence through an optical fiber. The output of the photodetector (105) is connected in sequence with an electrical filter (106) and an electrical amplifier (107) through a radio frequency line and injected into the electro-optic modulator (102) to form a positive feedback loop to form a stable oscillation. As Figure 1 shown. Control the electro-optic modulator (102) to work at the quadrature point to achieve double-sideband modulation of the oscillation signal. Assume that the optical field strength E in (t) output by the laser and the local oscillator driving signal V LO(t) is expressed as:

[0042]

[0043] where E 0 and ω c are the amplitude and angular frequency of the optical carrier, and V LO and ω LO are the amplitude and angular frequency of the oscillating signal. Then the output of the electro-optic modulator can be expressed as:

[0044]

[0045] At this time, the output of the electro-optic modulator mainly contains f c , f c ±f LO three optical sidebands.

[0046] The baseband electrical signals generated by the FPGA (109) are respectively connected to the electro-optic modulators (112)(113)(119)(120) through RF cables, as Figure 1 shown. According to the modulation relationship of the electro-optic modulator, setting the working state of the modulator to the maximum point, then the input-output relationship is:

[0047]

[0048] The signal amplitude of the unipolar electrical signal V(t) is the half-wave voltage of the corresponding modulator. Therefore, the two states (0, 1) of the baseband signal respectively correspond to (1, -1) of the output result. For the sake of easy expression, the four-way outputs are normalized and expressed as Φ 1 (t), Φ 2 (t), Φ 3 (t), Φ 4 (t), where:

[0049]

[0050] The optical delay synchronization synthesis system is implemented as follows. As Figure 1As shown in the figure: The optical signal output by the optoelectronic oscillator is divided into two paths by a 1×2 optical coupler (108) and used as the optical carriers of the system. The 1×2 optical coupler (110), fiber optic delay line (111), electro-optic modulator (112), and 2×1 coupler (115) are connected in sequence by optical fibers. The 1×2 optical coupler (110), electro-optic modulator (113), fiber optic delay line (114), and 2×1 coupler (115) are connected in sequence by optical fibers. Similarly, for another system optical carrier, the 1×2 optical coupler (117), fiber optic delay line (118), electro-optic modulator (119), and 2×1 coupler (122) are connected in sequence by optical fibers. The 1×2 optical coupler (117), electro-optic modulator (120), fiber optic delay line (121), and 2×1 coupler (122) are connected in sequence by optical fibers. The dual-channel signals synthesized by the 2×1 coupler (115) and the dual-channel signals synthesized by the 2×1 coupler (122) are optically delay-matched by the fiber optic delay line (116) and power-controlled by the optical attenuator (123), and then synthesized into one signal by the 2×1 coupler (124). Thus, the synthesis of four baseband signals into one signal through optical delay synchronization and power control is completed. This signal is connected in sequence by optical fibers to the EDFA (125), optical bandpass filter (126), and photodetector (127), and the signal is transmitted through the antenna (128) connected by a radio frequency line.

[0051] Assume that the optical signal output by the optoelectronic oscillator is E OEO (t), and the dual-channel optical carriers passing through the 1×2 optical coupler (108) are represented as E 1 (t), E 2 (t):

[0052] According to the principles of electro-optic modulators and optical delay, the dual-channel input signals E 11 (t), E 12 (t) of the 2×1 optical coupler (115) can be expressed as:

[0053]

[0054] where Δt 111 , Δt 114 are the optical path delays introduced by the fiber optic delay lines, and Δt 110 is the delay difference introduced by the asynchronous dual channels of the optical coupler (110). The two signals are synthesized by the 2×1 optical coupler (115), and Δt 115 is the asynchronous delay difference of the two channels of this coupler. The synthesized signal is expressed as follows:

[0055]

[0056] Adjust the fiber optic delay lines (11)(14) so that the delays satisfy the following relationship:

[0057]

[0058] At this time, e 13 (t) can be expressed as follows:

[0059]

[0060] This is a time-delay matching dual-channel modulation synthesis system, which realizes the misaligned synthesis of two signals through time-delay matching. It can be seen from the formula that the relationship between the power of the output signal and the two input signals is "exclusive OR", that is

[0061]

[0062] Therefore, by changing the time-delay difference between the two signals, the signal with the original frequency f can be delayed by half a period through time-delay misalignment to obtain a new data with a frequency of 2f, and the operation method is the "exclusive OR" relationship. Thus, the optical domain synthesis of the two signals is realized through time-delay matching.

[0063] Similarly, according to the above principle, another group of signals E 21 (t), E 22 (t) after passing through the time-delay matching dual-channel modulation synthesis system and entering the 1×2 optical coupler (112) can be expressed as:

[0064]

[0065] where Δt 118 , Δt 121 are the optical path delays introduced by the optical fiber delay lines, and Δt 108 , Δt 117 are the time-delay differences introduced by the dual-channel asynchronism of the 1×2 optical couplers (108)(117) respectively. The two signals are synthesized by the 2×1 optical coupler (122), and Δt 122 is the time-delay difference of the two-channel asynchronism of this coupler. The synthesized signal is expressed as follows:

[0066] Adjust the optical fiber delay lines (118)(121) so that the time delay satisfies the following relationship:

[0067]

[0068] At this time, E 23 (t) can be expressed as follows:

[0069]

[0070] The signal E out (t) synthesized through the optical fiber delay line (16) and the 2×1 coupler (24) is expressed as follows:

[0071]

[0072] The regulation delay line is as follows. After matching the dual-channel synthesis, the following results are obtained:

[0073]

[0074] The optical signal is converted into an electrical signal by a photodetector. Ignoring the carrier signals above the second order, the approximate expression of the electrical signal is as follows:

[0075]

[0076] Regulate the optical attenuator (23) so that The power matching results in the following change of the electrical signal expression:

[0077] At this time, the four-channel baseband signals have synchronized the optical delay and controlled the power of one signal, and up-converted it to radio frequency for transmission through the antenna. This is the principle of the signal generation end of the device of the present invention. Figure 6 This is the simulation schematic diagram of the system. Figure 6 (a) and (b) are respectively the four 1x-speed binary baseband signals to be transmitted; Figure 6 (c) and (d) are the two radio frequency signals respectively synthesized by the optical delay synchronization synthesis system. After filtering and other processing, two 2x-speed binary signals can be obtained, which respectively correspond to the synthesis of the previous data; Figure 6 (e) is a radio frequency signal synthesized by power control, that is, a 4x-speed binary signal, and the low and high bits respectively correspond to Figure 6 the two signals of (c) and (d); Figure 6 (f) is the spectrum diagram of the output radio frequency signal, and the baseband signal is shifted to 10 GHz.

[0078] The multi-order complex signal receiving and signal demodulating method and device of the present invention include that after the radio frequency signal is received, it is amplified by a radio frequency amplifier, down-converted to the baseband by photon technology, realizes dual-channel time division multiplexing by using dual-channel optical delay, and through photoelectric detection, low-pass filtering and other processing, respectively samples to obtain odd and even bit signals, and obtains multiple original signals through a demodulation algorithm.

[0079] Utilize the technology of microwave photonics to realize the down-conversion of broadband radio frequency signals, which is achieved by cascading modulators. Such as Figure 2Shown: The optoelectronic oscillator loop has the same structure as the optoelectronic oscillator at the transmitting end, but the frequencies of the oscillating signals are different, and the electro-optic modulator operates at the minimum point to achieve carrier-suppressed double-sideband modulation of the oscillating signal; the output is connected to the electro-optic modulator (210) through an optical fiber as the carrier of the next stage, and the RF signal received by the antenna (208) is sequentially connected to the RF amplifier (209) and the electro-optic modulator (210) through an RF line. The modulator is set to operate at the quadrature point to load the RF signal onto the optical carrier.

[0080] Let the center frequency of the laser be f c , the frequency of the oscillating signal formed by the optoelectronic oscillator be f lo , and the center frequency of the received RF signal be f RF , then it can be considered that the frequency of the output signal of the optoelectronic oscillator is f c ±f lo . After passing through the electro-optic modulator (210) and ignoring the higher-order components, it can be considered that the frequency of the output signal is f c ±f lo , f c ±f lo ±f RF . By controlling the RF signal to be near the optical sideband output by the optoelectronic oscillator and ignoring the higher-order signals, the approximate output can be obtained as:

[0081] i(t)∝cos[(f c +f lo +f RF -f c +f lo )t]+cos[(f c +f lo -f RF -v c +f lo )t]+cos[(f c -f lo +f RF -f c -f lo )t]+cos[(f c -f lo -f RF -f c -f lo )t]

[0082] =cos[(2f lo +f RF )t]+cos[(2f lo -f RF )t]+cos[(f RF -2f lo )t]+cos[(-f RF -2flo )t]

[0083] Set 2f lo -f RF = 2f, that is, twice the frequency of the original baseband signal, and the photonic down-conversion of the RF signal is completed. The optical domain processing of the signal sampling is as follows Figure 2 As shown, the down-converted signal passes through an optical delay (212), and the signal delay difference between the two paths entering the digital samplers (217)(218) is controlled to be T / 2. The signals with a delay difference of T / 2 for the two paths are respectively sent to the photodetectors (213)(214), and the target signal is extracted through the low-pass filters 2(10)(212), and two columns of signals are sampled using the digital samplers (217)(218).

[0084] The processing and demodulation block diagram of the sampled signal is as follows Figure 4 As shown: The sampling rate of the digital sampler is set to Nf, where N is the downsampling (401) factor, and the lowest value that can be taken is 1. The sampled signal is digitally mapped (402) to obtain the data Sr 1 and Sr 2 , and these two columns of data respectively represent the odd and even bits of the output 2x speed signal; through serial-to-parallel conversion (403), it is further decomposed into Sr 11 , Sr 12 , Sr 21 , Sr 22 four groups of data, where Sr 11 , Sr 21 are the high bits, and Sr 12 , Sr 22 are the low bits. To respectively realize the restoration of the high and low bits to the original signal (404), the flowchart of the implemented demodulation algorithm is as follows Figure 5 As shown. Taking the conversion of the even signal Sr 21 (404-1) and the odd signal Sr 11 (404-2) of the high bits to restore the original D 1 (404-7), D 2 (404-11) data as an example, the algorithm logic is as follows: Compare bit by bit (404-4) Sr 11 and Sr 21 at the same time sequence: If the signals are not equal, the corresponding original signal D 1 is 1 (404-5); if the signals are equal, the corresponding original signal D 1 is 0 (404-6). Compare bit by bit (404-8) Sr 21 and Sr 11 of the next time sequence bit (404-3): If the signals are equal, the corresponding original signal D 2 is 0 (404-9); if the signals are not equal, the corresponding original signal D2 is 1(404 - 10). The original signal D is realized 1 and D 2 is restored.

[0085] Through Figure 4 data processing and Figure 5 the demodulation algorithm, the signal can be directly restored to the original D 1 and D 2 and D 3 and D 4 four columns of binary data streams, and the demodulation result is unique. Thus, the demodulation of the modulation signal is realized.

[0086] Figure 7 is the simulation schematic diagram of the receiving system. Figure 7 (a) is the spectrum diagram of the transmitted radio frequency signal. Figure 7 (b) is the time domain diagram of the transmitted signal. Through the down-conversion structure at the receiving end, the signal is down-converted to a low frequency to obtain a spectrum diagram as shown in Figure 7 (d), and two groups of baseband signals are obtained through dual-channel sampling as shown in Figure 7 (e), and the time domain difference is T / 2. The data obtained by this sampling and the original transmitted data can be restored to the original data through the above demodulation algorithm.

[0087] The above description of the embodiments is to facilitate the understanding and application of the present invention by ordinary technical personnel in the technical field. It is obvious that those skilled in the art can easily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A multi-order complex signal generation method and demodulation device based on optical delay synchronization and power control, characterized in that: The system includes: baseband signal generation, multi-channel signal synthesis transmission optical link and signal receiving optical link, signal demodulation method and device; the baseband signal generation part needs to process the original data to generate the electrical signal to be transmitted; firstly, the binary data stream D i Perform reverse differential encoding (301) to obtain the binary code S i , which is a binary sequence to be transmitted; on this basis, S i Generates a unipolar electrical signal V with a symbol period of T, a frequency of f, and a signal amplitude of the half-wave voltage of the modulator used i (t)(302).

2. The method and device for generating a multi-order complex signal according to claim 1, characterized in that: The multi-channel signal synthesis optical link includes: an optoelectronic oscillator, two optical delay synchronization synthesis systems and a radio frequency transmission module; the optoelectronic oscillator is used to generate an optical carrier and a sideband signal, which are used as a carrier of a subsequent system and to generate a radio frequency signal for transmission; the optical delay synchronization synthesis system is used to synthesize a dual-channel baseband signal into a frequency-doubled signal through optical delay synchronization; higher-order signals are synthesized between the delay systems through power control, and the signals are transmitted after being beat to radio frequency, thereby obtaining a high-frequency carrier multi-order complex signal that can be used for long-distance high-speed wireless transmission.

3. The method and device for generating a multi-order complex signal according to claim 2, characterized in that: The optoelectronic oscillator loop includes a laser (101), an electro-optical modulator (102), an optical coupler (103), a low-loss single-mode optical fiber (104), a photodetector (105), an electric filter (106), and an electric amplifier (107), which form a positive feedback loop to form a stable oscillation; the electro-optical modulator works at a quadrature point to realize double-sideband modulation of the oscillation signal.

4. The method and device for generating a multi-order complex signal according to claim 2, characterized in that: The optical delay synchronization synthesis system realizes the double-speed synthesis of dual-path baseband signals. The optical signal output by the optoelectronic oscillator is used as the optical carrier of two systems respectively through a 1×2 optical coupler (108) with a splitting ratio of 50:50; and then is divided into two paths through a 1×2 optical coupler (110) with a splitting ratio of 50:

50. One path is injected into an electro-optical modulator (112) after being delayed by an optical fiber delay line (111), and the other path is first injected into an electro-optical modulator (113) and then delayed by an optical fiber delay line (114). The two paths are synthesized by a 2×1 coupler (115) to obtain one signal. The optical fiber delay lines (111) and (114) are used to match the delay difference of the two paths of the couplers (110) and (115), and are required to realize a time domain phase difference of T / 2 between the modulated electrical signals of the electro-optical modulators (112) and (113).

5. The method and device for generating a multi-order complex signal according to claim 4, characterized in that: The two optical delay synchronization synthesis systems realize link synthesis through power control of an adjustable optical attenuator (123), and realize dual-path synchronization by using an optical fiber delay line (116), and finally synthesize a 4-times-speed multi-order complex modulation signal through a 2×1 optical coupler (124).

6. The method and device for generating a multi-order complex signal according to claim 4, characterized in that: The modulation bandwidth of the electro-optical modulator (112) (113) (119) (120) is required to be more than twice the baseband signal rate, i.e., 2f; the electro-optical modulator (112) modulates the signal V1(t), the electro-optical modulator (113) modulates the signal V2(t), the electro-optical modulator (119) modulates the signal V3(t), and the electro-optical modulator (120) modulates the signal V4(t).

7. The method and device for generating a multi-order complex signal according to claim 2, characterized in that: The synthesized signal is amplified by an EDFA (Erbium-doped Optical Fiber Amplifier) ​​(125), filtered by an optical bandpass filter (126), and then input into a photodetector (127), which converts the optical signal into a radio frequency signal and transmits it. The carrier of the radio frequency signal has the same frequency as the electrical signal obtained by the optoelectronic oscillator.

8. The signal receiving and demodulating method and device according to claim 1, characterized in that: The signal receiving optical link includes receiving a high-frequency carrier multi-order complex signal and amplifying it through a radio frequency amplifier, down-converting it to baseband through photonic technology, realizing dual-path time division multiplexing by using dual-path optical delay, sampling to obtain parity and even bit signals respectively through photoelectric detection, low-pass filtering and other processing, and obtaining multiple original signals through a demodulation algorithm.

9. The signal receiving and demodulating method and device according to claim 7, characterized in that: After receiving a multi-order complex radio frequency signal (208), it is amplified by a radio frequency amplifier (209) and then down-converted using the microwave photonic technology of a cascade modulator; the front stage uses an optoelectronic oscillator loop, and the back stage uses an electro-optical modulator (210) to load the radio frequency signal near the sideband; the signal is divided into two paths, and the time domain phase difference of the two signals is controlled by an optical fiber delay line (212) to be T / 2; the two signals are respectively sent to a photoelectric detector (213) (215) and then passed through a low-pass filter (214) (216) to extract the target signal, and the data obtained by sampling (217) (218) is sent to a demodulation algorithm to restore the original data.

10. The signal receiving and demodulating method and device according to claim 8, characterized in that: The receiving end optoelectronic oscillator loop has the same structure as the transmitting end optoelectronic oscillator, and includes a laser (201), an electro-optical modulator (202), an optical coupler (203), a low-loss single-mode optical fiber (204), a photodetector (205), an electric filter (206), and an electric amplifier (207) to form a positive feedback loop to form a stable oscillation. The difference is that the frequency of the oscillation signal is different, and the electro-optic modulator works at the minimum point to achieve carrier suppressed double-sideband modulation of the oscillation signal; The signal sampling rate Nf is set, where N is an integer and can be as small as 1, corresponding to the factor of downsampling (401); the sampling delay is adjusted so that the sampling point can be located at the middle point of each symbol period; The demodulation algorithm comprises the following steps: (1) The delayed synchronized dual-path signals are sampled after photoelectric conversion, and the parity bits of the corresponding output signals are downsampled (401) to obtain only one data in each symbol period; (2) performing four-level digital mapping (402) on the two signals; (3) dividing the two odd and even signals into high and low bit data through serial-to-parallel conversion (403), a total of four groups of data; (4) respectively analyzing the parity data of the high-order and low-order signals, and demodulating (404) to obtain the original four-channel signals; The demodulation algorithm (404) comprises the following steps: The specific algorithm logic for demodulating to the original data (404) is as follows: take the odd or even signal of the high or low bit, and compare (404-4) the even signal (404-1) and the odd signal (404-2) at the same time sequence: if the signals are not equal, the corresponding original one-way data is 1 (404-5); if the signals are equal, the corresponding original one-way data is 0 (404-6); compare (404-8) the even signal (404-1) and the odd signal of the next time sequence bit (404-3): if the signals are equal, the corresponding original two-way data is 0 (404-9); if the signals are not equal, the corresponding original two-way data is 1 (404-11); through the demodulation process, the original one-way data (404-7) and the original two-way data (404-11) are obtained; similarly, the original three-way data and four-way data can be obtained.

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