CN115459855B - Digital pulse shaping method based on linear superposition and optical fiber communication system - Google Patents
Digital pulse shaping method based on linear superposition and optical fiber communication system Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/508—Pulse generation, e.g. generation of solitons
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/524—Pulse modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/66—Non-coherent receivers, e.g. using direct detection
- H04B10/69—Electrical arrangements in the receiver
- H04B10/697—Arrangements for reducing noise and distortion
- H04B10/6972—Arrangements for reducing noise and distortion using passive filtering
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Abstract
The invention provides a digital pulse shaping method based on linear superposition and an optical fiber communication system, wherein the optical fiber communication system comprises a pulse shaping digital filter; the digital pulse shaping method based on linear superposition comprises the following steps: performing linear superposition processing on N different pulse shaping digital filter models to obtain a superposed pulse shaping digital filter model, wherein N is a positive integer greater than 1; according to the superimposed pulse shaping digital filter model, parameter adjustment is carried out on the pulse shaping digital filter; and the pulse shaping digital filter of the digital signal to be transmitted after parameter adjustment generates a shaped digital signal. According to the invention, the N pulse shaping digital filter models are subjected to linear superposition, so that the adjustment of the parameters of the pulse shaping digital filter can be realized, the degree of freedom of adjustment is large, the compatibility is strong, the flexibility is flexible, the transmission performance is further improved, and the cost and the complexity are reduced.
Description
Technical Field
The invention relates to the technical field of optical fiber communication, in particular to a digital pulse shaping method based on linear superposition and an optical fiber communication system.
Background
In a direct alignment (IM/DD) optical fiber communication system, particularly in a C-band (1530-1565 nm), due to large dispersion, after a certain distance of optical fiber transmission, frequency selective fading (fading) occurs in signals caused by dispersion and square rate detection, the power of different frequency components of the signals is attenuated to different extents, even completely submerged by noise, and strong inter-code interference (ISI) is introduced from the time domain, which greatly limit the communication performance, capacity and transmission distance of the actual IM/DD system. Especially for low cost high speed (> 100 Gb/s) data center optical interconnect (> 2km, inter-DCI) transmission systems.
On the other hand, pulse shaping (pulse shaping) is critical in the communication field, and can reduce the influence of inter-symbol interference (ISI) caused by bandwidth limitation in actual transmission. The effective bandwidth required for different pulse shaping is different and has a different frequency distribution. Common simple pulse shaping techniques include raised cosine shaped non-return to zero pulse shaping (RC-NRZ pulse shaping, abbreviated RC) and rectangular non-return to zero pulse shaping (Rect-NRZ pulse shaping, abbreviated Rect) and rectangular return to zero pulse shaping (RZ).
The fact that the frequency distribution of the Rect and the RZ is fixed, no parameter adjustment exists, and the transmission performance is difficult to further improve in a long-distance high-capacity system, so that the method has certain limitation; while RC can achieve a certain degree of freedom of tuning by roll-off factor (RoF), it is also difficult to further improve transmission performance in long-range high-capacity systems. There are, of course, other complex pulse shaping techniques that can change their frequency distribution, but are more complex to implement. That is, existing pulse shaping techniques have certain limitations for fibre channels that are limited in practical bandwidth and have chromatic dispersion.
Accordingly, the prior art has drawbacks and needs to be improved and developed.
Disclosure of Invention
The invention aims to solve the technical problems that the transmission performance cannot be further improved in a long-distance large-capacity system through simple parameter adjustment in the prior art.
The technical scheme adopted for solving the technical problems is as follows:
a digital pulse shaping method based on linear superposition, applied to an optical fiber communication system, characterized in that the optical fiber communication system comprises: a pulse shaping digital filter;
the digital pulse shaping method based on linear superposition comprises the following steps:
performing linear superposition processing on N different pulse shaping digital filter models to obtain a superposed pulse shaping digital filter model, wherein N is a positive integer greater than 1;
according to the superimposed pulse shaping digital filter model, parameter adjustment is carried out on the pulse shaping digital filter;
and the pulse shaping digital filter of the digital signal to be transmitted after parameter adjustment generates a shaped digital signal.
In one implementation, the fiber optic communication system includes: the weight distribution unit and the superposition unit are connected with each other; and performing linear superposition processing on the N different pulse shaping digital filter models to obtain a superposed pulse shaping digital filter model, wherein the method comprises the following steps of:
n different pulse shaping digital filter models and weight coefficients of the pulse shaping digital filter models are determined in advance according to actual channel requirements;
each pulse shaping digital filter model generates a pulse shaping digital filter model with a corresponding weight value through the weight distribution unit according to each weight coefficient;
and adding tap values of corresponding positions of all the pulse shaping digital filter models with corresponding weights through the superposition unit to obtain a superposed pulse shaping digital filter model.
In one implementation, the weight distribution unit is a multiplier, an amplifier, or an attenuator; the superposition unit is an adder or a beam combiner.
In one implementation, the pulse shaping digital filter model is a raised cosine shaped non-return to zero pulse shaping digital filter model, a rectangular non-return to zero pulse shaping digital filter model, or a rectangular return to zero pulse shaping digital filter model.
In one implementation, the fiber optic communication system further includes: a digital signal generator connected to the pulse shaping digital filter; the pulse shaping digital filter after the digital signals to be transmitted are overlapped generates shaped digital signals, which comprises the following steps:
when the digital signal generator generates a digital signal to be transmitted, the digital signal to be transmitted passes through the pulse shaping digital filter to generate a shaped digital signal.
In one implementation, the fiber optic communication system further includes: the pulse shaping digital filter, the digital-to-analog converter and the intensity modulator are sequentially connected; the pulse shaping digital filter after the digital signal to be transmitted is subjected to parameter adjustment, after generating the shaped digital signal, further comprises:
inputting the shaped digital signal into the digital-to-analog converter to obtain an analog electric signal;
the intensity modulator modulates the analog electric signal onto a single-frequency optical carrier wave output by the laser to generate an optical signal.
In one implementation, the fiber optic communication system further includes: the optical fiber, and the optical amplifier, the optical attenuator, the photoelectric detector, the oscilloscope and the off-line digital signal processing module are connected in sequence; the intensity modulator modulates the analog electric signal onto a single-frequency optical carrier wave output by the laser, and after generating an optical signal, the method further comprises the following steps:
transmitting the optical signal through an optical fiber;
the optical signals after transmission are amplified by the optical amplifier, attenuated by the optical attenuator and photoelectrically converted by the photoelectric detector to obtain received electric signals;
the received electric signal is sampled by the oscilloscope to obtain a received digital signal;
and inputting the received digital signal into the off-line digital signal processing module for off-line digital signal processing.
The present invention also provides an optical fiber communication system, wherein the optical fiber communication system includes: the pulse shaping device comprises a weight distribution unit, a superposition unit and a pulse shaping digital filter which are connected in sequence;
the weight distribution unit is used for receiving corresponding pulse shaping digital filter models in the N different pulse shaping digital filter models and generating pulse shaping digital filter models with corresponding weight values according to preset weight coefficients;
the superposition unit is used for adding tap values of corresponding positions of the pulse shaping digital filter models with corresponding weights to obtain a superposed pulse shaping digital filter model;
the pulse shaping digital filter is used for carrying out parameter adjustment according to the superimposed pulse shaping digital filter model and shaping the digital signal to be transmitted.
In one implementation, the fiber optic communication system further includes: the digital signal generator is connected with the pulse shaping digital filter, and the pulse shaping digital filter, the digital-to-analog converter and the intensity modulator are sequentially connected; the optical fiber communication system further comprises an optical fiber, an optical amplifier, an optical attenuator, a photoelectric detector, an oscilloscope and an off-line digital signal processing module which are connected in sequence;
the digital signal generator is used for generating a digital signal to be transmitted;
the digital-to-analog converter is used for converting the shaped digital signal into an analog electric signal;
the intensity modulator is used for modulating the analog electric signal onto a single-frequency optical carrier wave output by the laser to generate an optical signal;
the optical fiber is used for transmitting the optical signal;
the optical amplifier is used for amplifying the optical signal after transmission;
the optical attenuator is used for attenuating the amplified optical signals;
the photoelectric detector is used for carrying out photoelectric conversion on the attenuated optical signals to obtain received electric signals;
the oscilloscope is used for sampling the received electric signal to obtain a received digital signal;
the off-line digital signal processing module is used for performing off-line digital signal processing on the received digital signal.
The invention also provides a computer readable storage medium storing a computer program executable for implementing the steps of the linear superposition based digital pulse shaping method as described above.
The invention provides a digital pulse shaping method based on linear superposition and an optical fiber communication system, wherein the optical fiber communication system comprises a pulse shaping digital filter; the digital pulse shaping method based on linear superposition comprises the following steps: performing linear superposition processing on N different pulse shaping digital filter models to obtain a superposed pulse shaping digital filter model, wherein N is a positive integer greater than 1; according to the superimposed pulse shaping digital filter model, parameter adjustment is carried out on the pulse shaping digital filter; and the pulse shaping digital filter of the digital signal to be transmitted after parameter adjustment generates a shaped digital signal. According to the invention, the N pulse shaping digital filter models are subjected to linear superposition, so that the adjustment of the parameters of the pulse shaping digital filter can be realized, the degree of freedom of adjustment is large, the compatibility is strong, the flexibility is flexible, the transmission performance is further improved, and the cost and the complexity are reduced.
Drawings
FIG. 1 is a flow chart of a preferred embodiment of a digital pulse shaping method based on linear superposition in the present invention.
Fig. 2 is a flowchart showing a step S100 in a digital pulse shaping method based on linear superposition according to a preferred embodiment of the present invention.
Fig. 3 is a schematic block diagram of an embodiment of a digital pulse shaping method based on linear superposition in the present invention.
Fig. 4 is a functional schematic of a preferred embodiment of the fiber optic communication system of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clear and clear, the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Referring to fig. 1, fig. 1 is a flowchart of a digital pulse shaping method based on linear superposition in the present invention. As shown in fig. 1, the digital pulse shaping method based on linear superposition according to the embodiment of the invention includes the following steps:
and step S100, carrying out linear superposition processing on N different pulse shaping digital filter models to obtain a superposed pulse shaping digital filter model, wherein N is a positive integer greater than 1.
The digital pulse shaping method based on linear superposition is particularly applied to an optical fiber communication system, and is particularly used for a direct alignment m-PAM optical fiber communication system. The optical fiber communication system includes: a pulse shaping digital filter. Since the common simple pulse shaping techniques include raised cosine non-return to zero pulse shaping (RC), rectangular non-return to zero pulse shaping (Rect) and rectangular return to zero pulse shaping (RZ), the present invention may utilize models of these simple pulse shaping techniques as a basis, that is, the pulse shaping digital filter model may be a raised cosine non-return to zero pulse shaping digital filter model, a rectangular non-return to zero pulse shaping digital filter model, or a rectangular return to zero pulse shaping digital filter model. And linearly superposing two or more of the models of the simple pulse shaping technology to obtain pulse shaping digital filter models with different average powers, and then carrying out parameter adjustment on the pulse shaping digital filter according to the superposed pulse shaping digital filter models.
In one implementation, the fiber optic communication system includes: a weight distribution unit and a superposition unit which are connected with each other. As shown in fig. 2, the step S100 specifically includes:
step S110, N different pulse shaping digital filter models and weight coefficients of the pulse shaping digital filter models are determined in advance according to actual channel requirements;
step S120, each pulse shaping digital filter model generates a pulse shaping digital filter model with a corresponding weight value through the weight distribution unit according to each weight coefficient;
and step 130, adding tap values of corresponding positions of all pulse shaping digital filter models with corresponding weights through the superposition unit to obtain a superposed pulse shaping digital filter model.
The invention relates to a novel digital pulse shaping technology which is based on N simple pulse shaping technologies and performs linear superposition with different weights. Because the average power requirements of the filters are different for different actual channels, the specific selection of different N pulse shaping digital filter models and the corresponding weights thereof are determined according to the actual channel requirements. Specifically, in the digital domain, each path of pulse shaping digital filter model utilizes a corresponding weight distribution unit to distribute weight values.
In one embodiment, the weight distribution unit is a multiplier, an amplifier, or an attenuator. That is, in the digital domain, N different pulse shaping digital filter models are multiplied by corresponding weight coefficients via multipliers or amplifiers, or the corresponding weight coefficients are attenuated via attenuators, thus producing N pulse shaping digital filter models of different weights (different average powers). The superposition unit is an adder or a beam combiner. The N pulse shaping digital filter models with different weights are subjected to linear superposition through an adder or a beam combiner, so that the novel pulse shaping digital filter model after superposition is realized.
Specifically, the linear superposition is implemented by adding, for example, if two pulse shaping digital filter models perform linear superposition, the expressions corresponding to the two pulse shaping digital filter models are f (n) and g (n), respectively, the linear superposition is a×f (n) +b×g (n), and a and b are corresponding weight coefficients.
The step S100 is followed by: and step 200, carrying out parameter adjustment on the pulse shaping digital filter according to the superimposed pulse shaping digital filter model.
According to the invention, the N pulse shaping digital filter models are subjected to linear superposition, so that the adjustment of the parameters of the pulse shaping digital filter can be realized, the communication transmission capacity and the transmission distance of the direct alignment and direct detection transmission system are further improved, or the transmission performance of the whole system is improved, the cost and the complexity are reduced, and meanwhile, the method has the characteristics of large adjustment freedom degree, strong compatibility and flexibility and practicability.
The step S200 is followed by: step S300, the pulse shaping digital filter of the digital signal to be transmitted after parameter adjustment generates a shaped digital signal.
In one implementation, the fiber optic communication system further includes: and a digital signal generator connected to the pulse shaping digital filter. The step S300 specifically includes: when the digital signal generator generates a digital signal to be transmitted, the digital signal to be transmitted passes through the pulse shaping digital filter to generate a shaped digital signal.
Specifically, the digital signal generator is an m-PAM digital signal generator, and the m-PAM digital signal to be transmitted is subjected to a novel pulse shaping digital filter to generate the required shaped m-PAM digital signal for subsequent digital-to-analog conversion and electro-optical modulation, and actual optical fiber system transmission.
In one embodiment, the fiber optic communication system further comprises: the pulse shaping digital filter, the digital-to-analog converter and the intensity modulator are sequentially connected. The step S300 further includes: inputting the shaped digital signal into the digital-to-analog converter to obtain an analog electric signal; the intensity modulator modulates the analog electric signal onto a single-frequency optical carrier wave output by the laser to generate an optical signal. That is, the signal to be transmitted is processed into an optical signal before optical fiber transmission is performed. Specifically, the pulse-shaped signal is a 60-Gbaud PAM-4 digital signal. The 60-Gbaud PAM-4 digital signal is converted into a PAM-4 analog electric signal of 60-Gbaud through a digital-to-analog converter. The intensity modulator modulates the PAM-4 analog electrical signal onto a single-frequency optical carrier (1550.12 nm) output by the laser, and maps the PAM-4 analog electrical signal linearly onto the intensity of the optical carrier.
In one implementation, the fiber optic communication system further includes: the optical fiber, and the optical amplifier, the optical attenuator, the photoelectric detector, the oscilloscope and the off-line digital signal processing module which are connected in sequence. The intensity modulator modulates the analog electric signal onto a single-frequency optical carrier wave output by the laser, and after generating an optical signal, the method further comprises the following steps: transmitting the optical signal through an optical fiber; the optical signals after transmission are amplified by the optical amplifier, attenuated by the optical attenuator and photoelectrically converted by the photoelectric detector to obtain received electric signals; the received electric signal is sampled by the oscilloscope to obtain a received digital signal; and inputting the received digital signal into the off-line digital signal processing module for off-line digital signal processing.
Specifically, the optical signal is sent to an optical fiber for transmission, and the optical fiber can be a standard single mode fiber of 100 km. The different parameters of the single mode fiber part, such as dispersion value, loss and the like, have the influence on the overall performance that the larger the dispersion value or the larger the loss, the performance is also deteriorated. The transmitted optical signal is amplified by an optical amplifier and attenuated by an optical attenuator to change the optical power detected subsequently; photoelectric conversion is carried out through a photoelectric detector to obtain a received electric signal, and sampling is carried out through an oscilloscope to obtain a received digital signal; and finally, sending the received digital signals to an off-line Digital Signal Processing (DSP) module for off-line digital signal processing. Thus, the complete transmission process of the digital signal to be transmitted is realized.
Because other complicated digital filters for adjusting signal frequency domain distribution mostly need to carry out complicated operation in the frequency domain, the invention only needs N simple pulse shaping digital filter models to carry out linear superposition, and has the characteristics of simple realization, strong compatibility and flexibility, and simultaneously, the adjustment degree of freedom is higher; compared with a single simple pulse shaping digital filter, the implementation complexity of the invention is comparable, but a new degree of freedom of adjustment is added, i.e. the specific selection of different N pulse shaping digital filter models and their corresponding weights achieve a new degree of freedom of adjustment. The invention can increase the communication transmission capacity and transmission distance of a direct alignment detection (IM/DD) m-PAM transmission system or improve the transmission performance of the whole system, in particular to a low-cost high-speed (> 100 Gb/s) data center optical interconnection (> 2km, inter-DCI) transmission system in a C wave band.
A specific example is described below.
Embodiment one:
as shown in fig. 3, two pulse shaping digital filter models of rz+rc are selected in advance according to the actual channel requirement, and the weight coefficient corresponding to RZ is determined to be a, and the weight coefficient corresponding to RC is determined to be b.
The RZ model is expressed as f (n), and a is multiplied by a through a multiplier 1 to obtain a x f (n); the RC model is expressed as g (n), b is multiplied by b through a multiplier 1, and b is obtained; a×f (n) and b×g (n) are processed by an adder 2 to obtain a×f (n) +b×g (n) after linear superposition, and parameter adjustment is performed on a pulse shaping digital filter 3 in an optical fiber communication system according to a×f (n) +b×g (n).
The PAM-4 digital signal generated by the m-PAM digital signal generator 4 is converted into a PAM-4 analog electric signal of 60-Gbaud through the digital-to-analog converter 5;
the intensity modulator 6 modulates the PAM-4 analog electric signal onto a single-frequency optical carrier wave (1550.12 nm) output by the laser 7, and linearly maps the PAM-4 analog electric signal onto the intensity of the optical carrier wave to obtain an optical signal;
sending the optical signal into a 100 km standard single-mode optical fiber 8 for transmission;
the transmitted optical signal is amplified by an optical amplifier 9 and attenuated by an optical attenuator 10 to change the optical power detected subsequently;
photoelectric conversion is performed by the photoelectric detector 11 to obtain a received electric signal, and sampling is performed by the oscilloscope 12 to obtain a received digital signal;
and finally, sending the received digital signals to an offline digital signal processing module 13 for offline digital signal processing.
In addition, two pulse shaping digital filter models RZ+Rect can be selected for linear superposition.
The present invention also provides an optical fiber communication system, referring to fig. 4, the optical fiber communication system includes: a weight distribution unit 21, a superposition unit 22, and a pulse shaping digital filter 23 connected in this order;
the weight distribution unit 21 is configured to receive a corresponding pulse shaping digital filter model of the N different pulse shaping digital filter models, and generate a pulse shaping digital filter model of a corresponding weight according to a preset weight coefficient;
the superimposing unit 22 is configured to add tap values at corresponding positions of the pulse shaping digital filter models with corresponding weights to obtain a superimposed pulse shaping digital filter model;
the pulse shaping digital filter 23 is configured to perform parameter adjustment according to the superimposed pulse shaping digital filter model, and perform shaping processing on a digital signal to be transmitted.
In one implementation, the fiber optic communication system further includes: the digital signal generator 24, the digital-to-analog converter 25, the intensity modulator 26 and the laser 27 are connected with the pulse shaping digital filter, and the pulse shaping digital filter, the digital-to-analog converter and the intensity modulator are connected in sequence; the optical fiber communication system further comprises an optical fiber 28, an optical amplifier 29, an optical attenuator 30, a photoelectric detector 31, an oscilloscope 32 and an offline digital signal processing module 33 which are connected in sequence;
the digital signal generator 24 is used for generating a digital signal to be transmitted;
the digital-to-analog converter 25 is used for converting the shaped digital signal into an analog electrical signal;
the intensity modulator 26 is configured to modulate the analog electrical signal onto a single-frequency optical carrier output by the laser 27, so as to generate an optical signal;
the optical fiber 28 is used for transmitting the optical signal;
the optical amplifier 29 is configured to amplify the optical signal after the transmission is completed;
the optical attenuator 30 is used for attenuating the amplified optical signal;
the photodetector 31 is configured to photoelectrically convert the attenuated optical signal to obtain a received electrical signal;
the oscilloscope 32 is used for sampling the received electric signal to obtain a received digital signal;
the offline digital signal processing module 33 is configured to perform offline digital signal processing on the received digital signal; as described in detail above.
The invention also provides a computer readable storage medium storing a computer program executable for implementing the steps of the linear superposition based digital pulse shaping method as described above.
In summary, the invention discloses a digital pulse shaping method based on linear superposition and an optical fiber communication system, wherein the optical fiber communication system comprises a pulse shaping digital filter; the digital pulse shaping method based on linear superposition comprises the following steps: performing linear superposition processing on N different pulse shaping digital filter models to obtain a superposed pulse shaping digital filter model, wherein N is a positive integer greater than 1; according to the superimposed pulse shaping digital filter model, parameter adjustment is carried out on the pulse shaping digital filter; and the pulse shaping digital filter of the digital signal to be transmitted after parameter adjustment generates a shaped digital signal. According to the invention, the N pulse shaping digital filter models are subjected to linear superposition, so that the adjustment of the parameters of the pulse shaping digital filter can be realized, the degree of freedom of adjustment is large, the compatibility is strong, the flexibility is flexible, the transmission performance is further improved, and the cost and the complexity are reduced.
It is to be understood that the invention is not limited in its application to the examples described above, but is capable of modification and variation in light of the above teachings by those skilled in the art, and that all such modifications and variations are intended to be included within the scope of the appended claims.
Claims (10)
1. A digital pulse shaping method based on linear superposition, applied to an optical fiber communication system, characterized in that the optical fiber communication system comprises: a pulse shaping digital filter;
the digital pulse shaping method based on linear superposition comprises the following steps:
performing linear superposition processing on N different pulse shaping digital filter models to obtain a superposed pulse shaping digital filter model, wherein N is a positive integer greater than 1;
according to the superimposed pulse shaping digital filter model, parameter adjustment is carried out on the pulse shaping digital filter;
and the pulse shaping digital filter of the digital signal to be transmitted after parameter adjustment generates a shaped digital signal.
2. The linear superposition based digital pulse shaping method according to claim 1, wherein the optical fiber communication system comprises: the weight distribution unit and the superposition unit are connected with each other; and performing linear superposition processing on the N different pulse shaping digital filter models to obtain a superposed pulse shaping digital filter model, wherein the method comprises the following steps of:
n different pulse shaping digital filter models and weight coefficients of the pulse shaping digital filter models are determined in advance according to actual channel requirements;
each pulse shaping digital filter model is processed by the weight distribution unit according to the weight coefficient of each pulse shaping digital filter model to generate a pulse shaping digital filter model with a corresponding weight;
and adding tap values of corresponding positions of all the pulse shaping digital filter models with corresponding weights through the superposition unit to obtain a superposed pulse shaping digital filter model.
3. The digital pulse shaping method based on linear superposition according to claim 2, wherein the weight distribution unit is a multiplier, an amplifier or an attenuator; the superposition unit is an adder or a beam combiner.
4. The linear superposition based digital pulse shaping method according to claim 1, wherein the pulse shaping digital filter model is a raised cosine shaped non-return to zero pulse shaping digital filter model, a rectangular non-return to zero pulse shaping digital filter model, or a rectangular return to zero pulse shaping digital filter model.
5. The linear superposition based digital pulse shaping method of claim 1, wherein the fiber optic communication system further comprises: a digital signal generator connected to the pulse shaping digital filter; the pulse shaping digital filter after the digital signals to be transmitted are overlapped generates shaped digital signals, which comprises the following steps:
when the digital signal generator generates a digital signal to be transmitted, the digital signal to be transmitted passes through the pulse shaping digital filter to generate a shaped digital signal.
6. The linear superposition based digital pulse shaping method of claim 1, wherein the fiber optic communication system further comprises: the pulse shaping digital filter, the digital-to-analog converter and the intensity modulator are sequentially connected; the pulse shaping digital filter after the digital signal to be transmitted is subjected to parameter adjustment, after generating the shaped digital signal, further comprises:
inputting the shaped digital signal into the digital-to-analog converter to obtain an analog electric signal;
the intensity modulator modulates the analog electric signal onto a single-frequency optical carrier wave output by the laser to generate an optical signal.
7. The linear superposition based digital pulse shaping method of claim 6, wherein the fiber optic communication system further comprises: the optical fiber, and the optical amplifier, the optical attenuator, the photoelectric detector, the oscilloscope and the off-line digital signal processing module are connected in sequence; the intensity modulator modulates the analog electric signal onto a single-frequency optical carrier wave output by the laser, and after generating an optical signal, the method further comprises the following steps:
transmitting the optical signal through an optical fiber;
the optical signals after transmission are amplified by the optical amplifier, attenuated by the optical attenuator and photoelectrically converted by the photoelectric detector to obtain received electric signals;
the received electric signal is sampled by the oscilloscope to obtain a received digital signal;
and inputting the received digital signal into the off-line digital signal processing module for off-line digital signal processing.
8. An optical fiber communication system, the optical fiber communication system comprising: the pulse shaping device comprises a weight distribution unit, a superposition unit and a pulse shaping digital filter which are connected in sequence;
the weight distribution unit is used for receiving corresponding pulse shaping digital filter models in the N different pulse shaping digital filter models and generating pulse shaping digital filter models with corresponding weight values according to preset weight coefficients;
the superposition unit is used for adding tap values of corresponding positions of the pulse shaping digital filter models with corresponding weights to obtain a superposed pulse shaping digital filter model;
the pulse shaping digital filter is used for carrying out parameter adjustment according to the superimposed pulse shaping digital filter model and shaping the digital signal to be transmitted.
9. The fiber optic communication system of claim 8, further comprising: the digital signal generator is connected with the pulse shaping digital filter, and the pulse shaping digital filter, the digital-to-analog converter and the intensity modulator are sequentially connected; the optical fiber communication system further comprises an optical fiber, an optical amplifier, an optical attenuator, a photoelectric detector, an oscilloscope and an off-line digital signal processing module which are connected in sequence;
the digital signal generator is used for generating a digital signal to be transmitted;
the digital-to-analog converter is used for converting the shaped digital signal into an analog electric signal;
the intensity modulator is used for modulating the analog electric signal onto a single-frequency optical carrier wave output by the laser to generate an optical signal;
the optical fiber is used for transmitting the optical signal;
the optical amplifier is used for amplifying the optical signal after transmission;
the optical attenuator is used for attenuating the amplified optical signals;
the photoelectric detector is used for carrying out photoelectric conversion on the attenuated optical signals to obtain received electric signals;
the oscilloscope is used for sampling the received electric signal to obtain a received digital signal;
the off-line digital signal processing module is used for performing off-line digital signal processing on the received digital signal.
10. A computer readable storage medium, characterized in that it stores a computer program executable for implementing the steps of the linear superposition based digital pulse shaping method according to any of claims 1-7.
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| US6337606B1 (en) * | 1999-02-02 | 2002-01-08 | Sicom, Inc. | Digital communications modulator having a modulation processor which supports high data rates |
| CN111884727A (en) * | 2020-07-15 | 2020-11-03 | 杭州电子科技大学 | High-speed photon digital-to-analog conversion method and system based on digital mapping |
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