CN112019295A - Orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation - Google Patents
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Abstract
The invention discloses an orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation, which belongs to the technical field of optical transmission.A series-parallel conversion unit is used for carrying out series-parallel conversion on input original data and then completing coding mapping in an APPM mapping unit, an up-sampling unit is used for carrying out orthogonal filtering on coded signals, and an adder unit is used for adding the filtered signals to synthesize a path of three-dimensional APPM signals for orthogonal mode transmission; the method realizes multiplexing of three paths of pulse amplitude modulation (APPM) signals based on three groups of orthogonal filters, further realizes great multiplication of transmission capacity by combining an orthogonal mode multiplexing transmission method, improves the problem of low APPM frequency spectrum efficiency, increases the transmission capacity, and provides a possibility for APPM to be expanded to more dimensions; meanwhile, the transmission scheme of orthogonal mode multiplexing eliminates mode crosstalk in few-mode optical fibers, MIMO-DSP processing is not needed at a receiving end, system cost is reduced, and high-capacity transmission with low complexity is realized.
Description
Technical Field
The invention belongs to the technical field of optical communication, and particularly relates to an orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation.
Background
With the acceleration of the information-based construction process, network users are increased rapidly, network flow is increased explosively, and the information is indicated according to a report that: from 2017 to 2022, mobile data traffic will grow at a Compound Annual Growth Rate (CAGR) of 46%, and by 2022 will reach 77.5 octets per month. In order to solve the problem, a mode multiplexing technology based on few-mode optical fiber is an indispensable technical scheme, and the transmission capacity is doubled by using different modes in the few-mode optical fiber as different spatial channels for data transmission. In a mode multiplexing system, although all orthogonal spatial modes and polarization modes in a few-mode fiber (FMF) are used as independent data channels, in actual fiber transmission, coupling occurs between the modes in the FMF due to various influencing factors in a link, so that crosstalk is generated, and the transmission information quality is influenced. Some researchers have adopted Multiple Input Multiple Output (MIMO) DSP processing schemes to solve the problem of mode crosstalk effectively by using these MIMO algorithms, but the MIMO is more expensive and more complex, and is more suitable for long-distance transmission than short-distance optical transmission, so that it is necessary to find a multiplexing mode with low complexity and high efficiency suitable for short-distance transmission.
Meanwhile, in a short-distance optical communication system, in order to accommodate more users and meet the requirement of transmission capacity, the development of short-distance transmission is from classical non-return-to-zero time division multiplexing (NRZ-TDM) to Wavelength Division Multiplexing (WDM) and more advanced modulation formats. Such as Orthogonal Frequency Division Multiplexing (OFDM), Carrierless Amplitude Phase (CAP) modulation, discrete multitone modulation (DMT), Pulse Amplitude Modulation (PAM), etc., which can achieve higher transmission capacity while maintaining the same bandwidth and number of channels. In these advanced modulation formats, PAM-4 has a significantly lower peak-to-average power than DMT modulation and better receiver sensitivity than CAP16 at the same bit rate, thus attracting the interest of a large number of researchers. However, the power loss of PAM increases exponentially with the increase of modulation order, and the problem of symbol crosstalk easily occurs in high-order PAM, which increases the difficulty of receiving and deciding. Pulse Position Modulation (PPM) divides a symbol into a plurality of subinterval intervals, and only one pulse signal exists in each interval, so that the method has the advantages of higher power efficiency and stronger intersymbol interference resistance, but also has the defect of low bandwidth utilization rate. Pulse amplitude position modulation (APPM) achieves a tradeoff between power consumption and bandwidth utilization by communicating information using both pulse amplitude and position, which can be viewed as a hybrid combination of M-PPM and M-PAM modulation formats. However, the conventional APPM also has the problems of large bandwidth occupation and low spectrum efficiency, is limited to be used in a high-rate transmission system, and needs a novel modulation mode combining pulse amplitude and position.
The APPM signal only has one pulse with information in each symbol period, so that the problems of large bandwidth occupation and low spectrum efficiency are easily caused, and meanwhile, the traditional APPM only has a single dimension, is difficult to improve transmission capacity and cannot meet the short-distance transmission requirements of large bandwidth requirement, large network scale and high flexibility; meanwhile, the conventional mode multiplexing system inevitably has the mode crosstalk problem, and a method which is purposefully proposed at present is not provided for simultaneously carrying out optimization compensation on the mode crosstalk problem and the mode crosstalk problem.
Disclosure of Invention
The purpose of the invention is as follows: in order to solve the problems of mode crosstalk in the traditional few-mode transmission system and low spectral efficiency in the traditional APPM modulation, the invention aims to provide an orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation, which adopts an orthogonal mode multiplexing system based on three-dimensional pulse amplitude position modulation to carry out transmission based on the appeal of high-capacity, low-complexity and high-spectral efficiency transmission and the generation mechanism of mode crosstalk.
The technical scheme is as follows: in order to achieve the purpose, the invention adopts the following technical scheme:
the orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation comprises the steps that input original data are subjected to serial-parallel conversion through a serial-parallel conversion unit and then are subjected to coding mapping in an APPM mapping unit, coded signals are subjected to orthogonal filtering through a filter unit after passing through an up-sampling unit, and the orthogonal filtered signals are added through an adder unit to form a path of three-dimensional APPM signals and then are subjected to orthogonal mode transmission.
Further, the method comprises the following steps:
1) the serial-parallel conversion unit converts input original data into parallel transmission data;
2) the data transmitted in parallel in the step 1) is subjected to APPM mapping to obtain signals subjected to APPM mapping through an APPM mapping unit, and then coding transmission is carried out;
one time slot exists pulse in each symbol period of the signal mapped by the APPM, and other time slots are 0, and the pulses have eight different combination forms;
3) performing up-sampling on the signal subjected to the APPM mapping in the step 2) through an up-sampling unit to realize the periodic continuation of the signal on a frequency spectrum and obtain three paths of APPM signals; in the up-sampling unit, the up-sampling of a certain multiple can restore the transmitted information at the receiving end, and simultaneously, the requirement of the number of taps of the filter is reduced;
4) filtering the signal obtained in the step 3) through a filter unit; multiplying the APPM signals after the up-sampling unit by three mutually orthogonal filters, and keeping the orthogonality of the three APPM signals;
5) synthesizing the three APPM signals in the step 4) into one path through an adder unit to obtain a complete three-dimensional APPM signal, and then transmitting the complete three-dimensional APPM signal in the orthogonal mode multiplexing system.
Further, in step 1), the input original data is divided into three data streams after being subjected to serial-to-parallel conversion, and multi-dimensional multiplexing is performed.
Further, in step 2), the three data streams generated by the serial-to-parallel change are each subjected to 2 × 4APPM mapping by the APPM mapping unit.
Further, in the 2 × 4APPM, each symbol has three bits, one bit is used for amplitude matching and two bits are used for position matching; wherein,irepresenting the amplitude bit, corresponding 0 and 1 tov 1 ，v 2 The probability of occurrence of two pulses with different amplitudes is equal, which is 1/2;jrepresenting a position bity 1 ,y 2 Combining for selecting one of the four time slots for filtering the energy signal, byiAndjthe selection and combination of the APPM signals complete the process of pulse amplitude position modulation, only one time slot of the generated APPM signals has pulses in each symbol period, the pulse amplitudes of other time slots are 0, and the pulses have eight different combination forms.
Further, in step 4), the filtering of the signal obtained in step 3) is to obtain three mutually orthogonal filter units by using a maximum-minimum optimization algorithm, and a frequency response curve formula of the orthogonal filter is expressed as:
wherein,f i is the first of the transmitting endiThe impulse response of the loop filter is determined,f 1the impulse response of the first filter at the transmitting end is shown,f 2representing the impulse response of the second filter on the transmitting side,f 3representing the impulse response of a third filter at the transmitting end; f isf i Frequency-amplitude characteristic of (1), F1Is a filterf 1Frequency-amplitude characteristic of (1), F2Is a filterf 2Frequency-amplitude characteristic of (1), F3Is a filterf 3The frequency-amplitude characteristic of (a); h is the target bandpass frequency response; in the linear constraintR（Z）For the polyphase decomposition of the filter bank of the receiver,S（Z）for the polyphase decomposition of the transmitter filter bank, for the permutation matrix,Iis a matrix of the units,Z -n representing n delay elements, and calculating a matched filter of the receiving end response through the linear constraint; on the basis of PR condition, the optimization principle is utilized to make IF 1 -HI, IF 2 -HI, IF 3 -HThe maximum one of the I three terms is minimized, and finally the transmission filter is optimized through iterationF i The portion beyond the target bandpass frequency response tends to be minimal.
Further, in the step 5), the synthesizing, by the adder unit, the three APPM signals in the step 4) into one path specifically includes: at a transmitting end, according to an orthogonalization mode field principle that a mode field correlation coefficient is 0, continuous light generated by a laser source passes through an SLM to realize the regulation and control of a mode field, orthogonal mode light with different mode spot radiuses is output, light input is provided for an MZM, and intensity modulation is realized; the three-dimensional APPM on the electric domain converts a digital signal into an analog signal waveform through a digital-to-analog converter and then is used for driving the MZM; the light of each mode loaded with the three-dimensional APPM is amplified by an erbium-doped fiber amplifier (EDFA) and then is synthesized into one path by an orthogonal photon coupler.
The spot radius of each mode is in a step shapeIncreasing radius (a 1 ＜a 2 ＜…＜a N ) The superposition appears as an arrangement of concentric circles with different radii. The orthogonal mode light carrying information and coupled into a path is transmitted in a 25KM few-mode optical fiber.
In the receiving end, the optical signal of the receiving end firstly passes through an optical filter, which can filter the amplifier spontaneous emission noise (ASE) noise generated by EDFA in the transmitting end and filter the channel noise at the same time; and then, the received optical power is adjusted through an adjustable optical attenuator (VOA), the photoelectric detector is used for detecting a received optical signal and converting the received optical signal into an electric signal, and finally, the demodulation and the error rate calculation of the three-dimensional APPM are carried out at a computer end.
The orthogonal mode multiplexing method based on three-dimensional pulse amplitude position modulation can be embodied in two aspects: firstly, input original data are divided into three parts after series-parallel conversion, the three parts are respectively mapped to form three paths of 2 multiplied by 4APPM matching signals, then the three paths of signals are subjected to upsampling and three groups of mutually orthogonal filters to generate mutually orthogonal three-dimensional signals, the three paths of signals are combined into one path through an adder, and at the moment, a three-dimensional APPM signal is generated; in a second aspect, continuous light output by a laser source passes through the optical field regulation function of a Spatial Light Modulator (SLM) to output a plurality of orthogonal mode lights with different mode spot radii, the cross correlation coefficient among a plurality of orthogonal mode light fields is 0, and the modes are mutually orthogonal. After the generated multiple orthogonal mode lights are respectively loaded with three-dimensional APPM signals, one path of light is synthesized by an orthogonal photon coupler and transmitted in few-mode optical fibers.
Has the advantages that: compared with the prior art, the orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation has the advantages that the APPM frequency spectrum efficiency is low, but the transmission quality is high, the system complexity and the cost are reduced by reducing the sampling multiple requirement in the sampling process and the required filter tap number, meanwhile, the three-dimensional APPM multiplexing realized based on three groups of orthogonal filters effectively improves the system transmission capacity, and provides possibility for the system to expand to higher dimension; based on the orthogonal mode multiplexing transmission method, mode crosstalk is reduced by eliminating overlapping between modes, multi-mode multiplexing transmission without MIMO processing at a receiving end can be realized, the complexity and the cost of a system are reduced, and the capacity of a transmission system is effectively improved.
Drawings
Fig. 1 is a flow chart of an orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation;
FIG. 2 is a three-dimensional pulse amplitude position modulation schematic;
FIG. 3 is a 2 × 4APPM mapping rule;
FIG. 4 is a graph of mutually orthogonal three-dimensional filter frequency responses;
FIG. 5 is a transmission protocol of the present invention;
fig. 6 shows the bit error rate simulation result of the present invention.
Detailed Description
The present invention will be further described with reference to the following embodiments.
An orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation is disclosed, as shown in fig. 2, input original data are subjected to serial-to-parallel conversion through a serial-to-parallel conversion unit and then are subjected to coding mapping in an APPM mapping unit, coded signals are subjected to orthogonal filtering through a filter unit after passing through an up-sampling unit, and orthogonal filtered signals are added through an adder unit to form a path of three-dimensional APPM signals and then are subjected to orthogonal mode transmission. The method specifically comprises the following steps:
1) series-parallel conversion unit
The serial-parallel conversion unit converts input data into parallel transmission data; in order to multiplex in multiple dimensions, input original data are divided into three data streams after being subjected to serial-parallel conversion;
2) APPM mapping unit
In order to perform better coding transmission, the three data streams of step 1) need to be subjected to APPM mapping; only one time slot has pulse in each symbol period of the signal mapped by the APPM, and other time slots are 0, and the pulses have eight different combination forms;
3) upsampling unit
In order to realize the periodic extension of the signal on the frequency spectrum, the APPM mapping signal in the step 2) needs to be up-sampled; in the up-sampling unit, the up-sampling of a certain multiple can restore the transmitted information at the receiving end, and simultaneously, the requirement of the number of taps of the filter is reduced;
4) filter unit
Filtering the signals obtained in the step 3) in order to keep the orthogonality of the three APPM signals; multiplying an APPM signal after an up-sampling unit by three paths of filters which are orthogonal to each other;
5) adder unit
In order to obtain a complete three-dimensional APPM signal, the three signals in the step 4) are combined into one path through an adder unit, and then the path is transmitted in an orthogonal mode multiplexing system.
In step 2), the three data streams generated by the serial-parallel change are respectively subjected to 2 × 4APPM mapping by an APPM mapping unit. In 2 x 4APPM, each symbol has three bits, one for amplitude matching and two for position matching. In the drawingsiRepresenting the amplitude bit, corresponding 0 and 1 tov 1 ，v 2 The probability of occurrence of two pulses with different amplitudes is equal, which is 1/2;jrepresenting a position bity 1 ,y 2 Combining for selecting one of the four time slots for filtering the energy signal, byiAndjthe selection and combination of the APPM signals complete the process of pulse amplitude position modulation, only one time slot of the generated APPM signals has pulses in each symbol period, the pulse amplitudes of other time slots are 0, and the pulses have eight different combination forms.
In step 3), taking the sampling multiple of 4 as an example, the spectrum period prolongation of 4 times is carried out. The sampling method comprises the following steps: assume that the input first 2 × 4APPM signal is {0,2,0,0,1, … }, and becomes {0,0,0,0, 0,2,0,0,0,0,0,0,0,0, … } after 4 times of upsampling.
In the step 4), in order to maintain the orthogonality of the three APPM signals, the signals obtained in the step 3) are filtered. Three mutually orthogonal filter units (including a first filter unit, a second filter unit and a third filter unit) are obtained by using a maximum minimum optimization algorithm, and a frequency response curve graph of the orthogonal filter can be specifically expressed by a formula as follows:
wherein,f i is the first of the transmitting endiThe impulse response of the loop filter is determined,f 1the impulse response of the first filter at the transmitting end is shown, and similarly,f 2，f 3and the impulse response of the third filter is the second path. F isf i Of frequency amplitude characteristic, i.e. F1Is a filterf 1Frequency-amplitude characteristic of (1), F2Is a filterf 2Frequency-amplitude characteristic of (1), F3Is a filterf 3Frequency amplitude characteristic of (2). H is the target bandpass frequency response; in the linear constraintR（Z）, S（Z）For polyphase decomposition of receiver and transmitter filter banks, for permutation matrices,Iis a matrix of the units,Z -n and representing n delay elements, and calculating a matched filter of the receiving end response through the linear constraint. Based on the above-mentioned equal numbers, on the basis of PR condition and using optimization principle to make IF 1 -HI, IF 2 -HI, IF 3 -HThe maximum one of the I three terms is minimized, and finally the transmission filter is optimized through iterationF i The portion beyond the target bandpass frequency response tends to be minimal.
In step 5), the system scheme of the orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation is shown in fig. 5. At a transmitting end, according to an orthogonalization mode field principle that a mode field correlation coefficient is 0, continuous light generated by a laser source passes through an SLM to realize the regulation and control of a mode field, orthogonal mode light with different mode spot radiuses is output to provide light input for an MZM, and intensity modulation is realized. Electric powerThe three-dimensional APPM in domain converts the digital signal to an analog signal waveform via a digital-to-analog converter, which is then used to drive the MZM. The light of each mode loaded with the three-dimensional APPM is amplified by an erbium-doped fiber amplifier (EDFA) and then is synthesized into one path by an orthogonal photon coupler. The radius of the spot of each mode is in a step-type increasing radius (a 1 ＜a 2 ＜…＜a N ) The superposition appears as an arrangement of concentric circles with different radii. The orthogonal mode light carrying information and coupled into a path is transmitted in a 25KM few-mode optical fiber.
At the receiving end, the optical signal at the receiving end passes through an optical filter, which can filter out the amplifier spontaneous emission noise (ASE) noise generated by EDFA in the transmitting end, and can filter out the channel noise at the same time, contrary to the work flow of the transmitting end. And then, the received optical power is adjusted through an adjustable optical attenuator (VOA), the photoelectric detector is used for detecting a received optical signal and converting the received optical signal into an electric signal, and finally, the demodulation and the error rate calculation of the three-dimensional APPM are carried out at a computer end.
Examples
Fig. 1 is a flow chart of a system according to the present invention, in which original data is subjected to three-dimensional APPM mapping to realize multi-dimensional multiplexing of 3 APPM signals, and simultaneously, N laser sources obtain a plurality of orthogonal mode lights with different mode spot radii after passing through an SLM, and then the three-dimensional APPM signals passing through a digital-to-analog converter (ADC) are subjected to orthogonal mode multiplexing under the action of a mach-zehnder modulator (MZM). In which three-dimensional pulse amplitude position modulation is the core content of the present invention, as shown in fig. 2, the process can be divided into serial-to-parallel conversion, APPM mapping, upsampling, filter and adder. The specific work flow of each module is as follows:
(1) series-parallel conversion unit
For multidimensional multiplexing, the input original data is divided into three data streams after being subjected to serial-to-parallel conversion.
(2) APPM mapping unit
Thus, only one time slot of the signal subjected to the APPM mapping has pulses in each symbol period, and other time slots are 0, and the pulses have eight different combinations.
The three data streams generated by the serial-to-parallel transformation are each subjected to 2 × 4APPM mapping, the mapping rule being shown in fig. 3. In 2 x 4APPM, each symbol has three bits, one for amplitude matching and two for position matching. In the drawingsiRepresenting the amplitude bit, corresponding 0 and 1 tov 1 ，v 2 The probability of occurrence of two pulses with different amplitudes is equal, which is 1/2;jrepresenting a position bity 1 ,y 2 Combining for selecting one of the four time slots for filtering the energy signal, byiAndjthe selection and combination of the APPM signals complete the process of pulse amplitude position modulation, only one time slot of the generated APPM signal has pulse and other time slots are 0 in each symbol period, and the pulse has eight different combination forms.
(3) Upsampling unit
In the up-sampling unit, the up-sampling of a certain multiple can restore the transmitted information at the receiving end, and simultaneously, the requirement of the number of taps of the filter is reduced. In a system with a sampling multiple of 4, the sampling method is as follows: assume that the input first 2 × 4APPM signal is {0,2,0,0,1, … }, and becomes {0,0,0,0, 0,2,0,0,0,0,0,0,0,0, … } after 4 times of upsampling.
(4) Filter unit
For three-dimensional multiplexing of the APPM, we multiply the up-sampled APPM signal by three mutually orthogonal filters. The invention uses the maximum and minimum optimization algorithm to obtain three mutually orthogonal filter units, and fig. 4 is a frequency response curve diagram of the orthogonal filter adopted by the invention, which can be expressed by a formula as follows:
wherein,f i is the first of the transmitting endiThe impulse response of the loop filter is determined,f 1indicating the first path filter impulse of the transmitting endIn response, the user may, likewise,f 2，f 3and the impulse response of the third filter is the second path. F isf i Of frequency amplitude characteristic, i.e. F1Is a filterf 1Frequency-amplitude characteristic of (1), F2，F3Is a filterf 2，f 3H is the target bandpass frequency response; in the linear constraintR（Z）,S（Z）For polyphase decomposition of receiver and transmitter filter banks, for permutation matrices,Iis a matrix of the units,Z -n and representing n delay elements, and calculating a matched filter of the receiving end response through the linear constraint. Based on the above-mentioned equal numbers and PR condition, use optimization principle to make IF 1 -HI, IF 2 -HI, IF 3 -HThe maximum one of the I three terms is minimized, and finally the transmission filter is optimized through iterationF i The portion beyond the target bandpass frequency response tends to be minimal.
(5) Adder unit
The three orthogonal signals after orthogonal filtering are simply added and synthesized into one path through an adder unit.
The system scheme of the orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation is shown in fig. 5. At a transmitting end, according to an orthogonalization mode field principle that a mode field correlation coefficient is 0, continuous light generated by a laser source passes through an SLM to realize the regulation and control of a mode field, orthogonal mode light with different mode spot radiuses is output to provide light input for an MZM, and intensity modulation is realized. The three-dimensional APPM in the electrical domain converts the digital signal to an analog signal waveform via a digital-to-analog converter, which is then used to drive the MZM. The light of each mode loaded with the three-dimensional APPM is amplified by an erbium-doped fiber amplifier (EDFA) and then is synthesized into one path by an orthogonal photon coupler. The radius of the spot of each mode is in a step-type increasing radius (a 1 ＜a 2 ＜…＜a N ) The superposition appears as an arrangement of concentric circles with different radii. Coupled into a single pathThe information-bearing orthogonal mode light is transmitted in 25KM few-mode fiber.
At the receiving end, the optical signal at the receiving end passes through an optical filter, which can filter out the amplifier spontaneous emission noise (ASE) noise generated by EDFA in the transmitting end, and can filter out the channel noise at the same time, contrary to the work flow of the transmitting end. And then, the received optical power is adjusted through an adjustable optical attenuator (VOA), the photoelectric detector is used for detecting a received optical signal and converting the received optical signal into an electric signal, and finally, the demodulation and the error rate calculation of the three-dimensional APPM are carried out at a computer end.
In order to illustrate the improvement of error performance of the method described in the patent, some characteristic values of the APPM, the three-dimensional APPM (3D-APPM), the 3D-CAP8 and the 3D-CAP16 are listed in Table 1. The information entropy of 2 × 4APPM and three-dimensional APPM can be calculated to be 0.75 and 2.25 respectively according to the formula of the information entropy, so that the transmission capacity of the three-dimensional APPM subjected to three-dimensional multiplexing can be regarded as three times of that of the conventional APPM. In the comparison of the three-dimensional APPM with the 3D-CAP8 and the 3D-CAP16, the up-sampling factor of the 3D-CAP-16 is set as 16, the up-sampling factors of other two modulation formats at the same transmission rate are calculated on the basis, the up-sampling rate factor of the three-dimensional APPM is lower than that of the other two schemes through the analysis of the results in the table 1, namely the occupied bandwidth is smaller, and the fact that the frequency spectrum utilization rate of the proposed scheme is improved compared with that of the traditional scheme is proved.
TABLE 1 comparison of three-dimensional APPM with 3D-CAP8, 3D-CAP16
To further illustrate that the proposed scheme has good error performance, simulation is performed in a white gaussian noise channel, the set sampling multiple is shown in table 1, the obtained error performance simulation result is shown in fig. 6, and the error rate is 10-3Then, the signal-to-noise ratios of the three-dimensional APPM, the 3D-CAP8 and the 3D-CAP16 are respectively as follows: 3.3dB, 4.13dB, 6.71 dB. Compared with 3D-CAP8 and 3D-CAP16, the three-dimensional APPM obtains the signal-to-noise ratio gains of 0.83dB and 3.41dB respectively. Illustrating the proposed solution to make the system obtainThe improvement of the error code performance is realized.
The above description is only a preferred embodiment of the present invention, and it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the technical principles of the present invention, and these modifications and variations should also be construed as the scope of the present invention.
Claims (7)
1. The orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation is characterized by comprising the following steps: the input original data is subjected to serial-to-parallel conversion through a serial-to-parallel conversion unit and then is subjected to coding mapping in an APPM mapping unit, coded signals are subjected to orthogonal filtering through a filter unit after passing through an up-sampling unit, and the orthogonally filtered signals are added through an adder unit to form a three-dimensional APPM signal and then are subjected to orthogonal mode transmission.
2. The orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation according to claim 1, characterized in that: the method comprises the following steps:
1) the serial-parallel conversion unit converts input original data into parallel transmission data;
2) the data transmitted in parallel in the step 1) is subjected to APPM mapping to obtain signals subjected to APPM mapping through an APPM mapping unit, and then coding transmission is carried out;
3) performing up-sampling on the signal subjected to the APPM mapping in the step 2) through an up-sampling unit to realize the periodic continuation of the signal on a frequency spectrum and obtain three paths of APPM signals; in the up-sampling unit, the up-sampling of a certain multiple can restore the transmitted information at the receiving end, and simultaneously, the requirement of the number of taps of the filter is reduced;
4) filtering the signal obtained in the step 3) through a filter unit; multiplying the APPM signals after the up-sampling unit by three mutually orthogonal filters, and keeping the orthogonality of the three APPM signals;
5) synthesizing the three APPM signals in the step 4) into one path through an adder unit to obtain a complete three-dimensional APPM signal, and then transmitting the complete three-dimensional APPM signal in the orthogonal mode multiplexing system.
3. The orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation according to claim 2, characterized in that: in step 1), the input original data is divided into three data streams after serial-to-parallel conversion, and multi-dimensional multiplexing is performed.
4. The orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation according to claim 3, characterized in that: in step 2), the three data streams generated by the serial-parallel change are respectively subjected to 2 × 4APPM mapping by an APPM mapping unit.
5. The orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation according to claim 4, characterized in that: in the 2 × 4APPM, each symbol has three bits, one bit for amplitude matching and two bits for position matching; wherein,irepresenting the amplitude bit, corresponding 0 and 1 tov 1 ，v 2 The probability of occurrence of two pulses with different amplitudes is equal, which is 1/2;jrepresenting a position bity 1 ,y 2 Combining for selecting one of the four time slots for filtering the energy signal, byiAndjthe selection and combination of the pulse amplitude position modulation are completed.
6. The orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation according to claim 2, characterized in that: in step 4), the filtering of the signal obtained in step 3) is to obtain three mutually orthogonal filter units by using a maximum-minimum optimization algorithm, and a frequency response curve formula of the orthogonal filter is represented as:
wherein,f i is the first of the transmitting endiThe impulse response of the loop filter is determined,f 1the impulse response of the first filter at the transmitting end is shown,f 2representing the impulse response of the second filter on the transmitting side,f 3representing the impulse response of a third filter at the transmitting end; f isf i Frequency-amplitude characteristic of (1), F1Is a filterf 1Frequency-amplitude characteristic of (1), F2Is a filterf 2Frequency-amplitude characteristic of (1), F3Is a filterf 3The frequency-amplitude characteristic of (a); h is the target bandpass frequency response; in the linear constraintR（Z）For the polyphase decomposition of the filter bank of the receiver,S（Z）for the polyphase decomposition of the transmitter filter bank, for the permutation matrix,Iis a matrix of the units,Z -n representing n delay elements, and calculating a matched filter of the receiving end response through the linear constraint; using the optimization principle toF 1 -HI, IF 2 -HI, IF 3 -HThe maximum one of the I three terms is minimized, and finally the transmission filter is optimized through iterationF i The portion beyond the target bandpass frequency response tends to be minimal.
7. The orthogonal mode multiplexing transmission method based on three-dimensional pulse amplitude position modulation according to claim 2, characterized in that: in step 5), the step of synthesizing the three APPM signals in step 4) into one path by the adder unit specifically includes: at a transmitting end, according to an orthogonalization mode field principle that a mode field correlation coefficient is 0, continuous light generated by a laser source passes through an SLM to realize the regulation and control of a mode field, orthogonal mode light with different mode spot radiuses is output, light input is provided for an MZM, and intensity modulation is realized; the three-dimensional APPM on the electric domain converts a digital signal into an analog signal waveform through a digital-to-analog converter and then is used for driving the MZM; and after light amplification is carried out on the light of each mode loaded with the three-dimensional APPM through the erbium-doped fiber amplifier, the light is synthesized into one path through the orthogonal photon coupler.
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