CN115459856A - Direct alignment and optical detection communication system and method based on module multiplexing - Google Patents
Direct alignment and optical detection communication system and method based on module multiplexing Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- 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
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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
- H04B10/2589—Bidirectional transmission
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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
- H04B10/2589—Bidirectional transmission
- H04B10/25891—Transmission components
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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
- H04B10/5161—Combination of different modulation schemes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention discloses a direct alignment and optical detection communication system and method based on module multiplexing, wherein the system comprises: n optical signal modulation units for generating N optical signals modulated by the fundamental mode; using N optical amplification units for amplifying optical signals; n first mode conversion units for obtaining optical signals of N channels with different modes; a mode multiplexing unit for combining the optical signals of the N channels with different modes into a first multiplexing mode optical signal; n module demodulation modules for demodulating and mode-converting N modules in the optical signal output by the communication fiber, respectively obtaining the optical signal modulated by the Mi-path mutual orthogonal mode corresponding to each module, and synthesizing the optical signal in the second multiplexing mode; and N photodetectors for converting the second multiplexed mode optical signal into an electrical signal. The invention improves the transmission performance and stability of the system, and has low cost, simple scheme and strong universality.
Description
Technical Field
The invention relates to the technical field of optical fiber communication, in particular to a module multiplexing-based direct alignment and optical detection communication system and method.
Background
A mode division multiplexing technology based on space dimensionality is a novel subversive technology for solving the next generation communication capacity crisis, and the principle of the technology is to use mutually orthogonal optical fiber modes as independent parallel channels for data transmission. For a short-distance optical fiber transmission system, the direct alignment detection technology with low cost, low complexity and low power consumption has great advantages in the detection scheme. Therefore, the module multiplexing direct alignment detection optical fiber transmission scheme has a wide development prospect in a short-distance optical interconnection system, and particularly has the aspect of expanding the optical communication capacity.
In an optical fiber communication system based on module multiplexing direct detection, because mode channels are involved, a transmission medium of the optical fiber communication system is not a single-mode optical fiber only supporting a fundamental mode, but a few-mode or multi-mode optical fiber supporting multiple modes, in the transmission medium, modes with extremely close or identical effective refractive indexes belong to the same module, and different modes in the same module are randomly coupled in the transmission medium, so that any one mode in each module is generally selected as an independent channel at a transmitting end. The simultaneously transmitted mode channels may also adopt different mode basis vectors, for example: linear polarization mode, orbital angular momentum mode or vector mode, etc. The number of modes (not including polarization) included in the fundamental mode module is 1, and the number of modes (not including polarization) included in the high-order mode module i is greater than or equal to 2, and is denoted as Mi. At present, the existing optical fiber communication system schemes based on module multiplexing direct alignment detection mainly include the following three types:
1. at a sending end, N independent optical signal modulation units generate N paths of independent signals which are loaded on N modes of N modules respectively, each mode channel is affiliated to different modules respectively, and each module comprises Mi independent modes. After the multiplexed optical signals are formed by the mode multiplexing unit, the multiplexed optical signals are transmitted in corresponding optical fiber media. And after transmission, the multiplexed optical signals reach a receiving end, the corresponding N modes in the multiplexed optical signals are demodulated into N paths of basic modes, then N paths of basic modes are sent to N single-mode photoelectric detectors to carry out photoelectric signal conversion and detection, and finally electric signal data acquisition and recovery are carried out. Such a scheme would only receive one of the Mi modes for a single module per module channel. However, because of the strong random coupling in the module during transmission in the optical fiber medium, the energy is randomly distributed in the same module mode, which results in the loss of received power and affects the performance and stability of the whole transmission system.
2. At a sending end, N independent optical signal modulation units generate N paths of independent signals which are loaded on N modes of N modules respectively, each mode channel is affiliated to different modules respectively, and each module comprises Mi independent modes. After the multiplexed optical signals are formed by the mode multiplexing unit, the multiplexed optical signals are transmitted in corresponding optical fiber media. And transmitting the optical signals to a receiving end, and multiplexing the corresponding M1+ M2+ in the optical signals. . . The MN modes are demodulated into M1+ M2+. . . M is a group of N And (2) a path-based mode, namely, respectively sending all Mi (i =1 or 2,.. Or N) modes in each module into Mi single-mode photoelectric detectors to perform photoelectric signal conversion, acquiring data, and performing diversity combining on Mi paths to recover the original signals loaded on each module. This solution can theoretically receive all the energy in each module, but in this solution a total of M1+ M2+ is required. . . The MN single-mode photodetector and the receiving technique using diversity combining are also required for each module, which is relatively high in cost and complexity.
3. At a sending end, N independent optical signal modulation units generate N paths of independent signals which are loaded on N modes of N modules respectively, each mode channel is affiliated to different modules respectively, and each module comprises Mi independent modes. After the multiplexed optical signals are formed by the mode multiplexing unit, the multiplexed optical signals are transmitted in corresponding optical fiber media. And transmitting the data to a receiving end, separating the N modules by using a specific module demultiplexing device, and respectively transmitting the separated N modules to the N multimode photoelectric detectors. And finally, carrying out electric signal data acquisition and recovery after photoelectric signal conversion. The scheme can collect all energy in each module theoretically, but the scheme needs the module demultiplexing device to adapt to the used mode basis vector and communication transmission optical fiber, and when different mode basis vectors or different communication transmission optical fibers are used, a specific module demultiplexing device needs to be matched with the module demultiplexing device, so that the universality is not strong.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the above-mentioned deficiencies of the prior art, an object of the present invention is to provide a module multiplexing based optical fiber communication system and method for alignment detection, so as to solve the problems of poor transmission performance and stability, high cost, complexity and poor versatility of the existing module multiplexing based optical fiber communication system for alignment detection.
The technical scheme of the invention is as follows:
a direct alignment optical detection communication system based on module multiplexing comprises: the device comprises N optical signal modulation units, N optical amplification units, N first mode conversion units, a mode multiplexing unit, a communication optical fiber, N module demodulation modules and N photoelectric detectors; wherein N is greater than or equal to 1;
the N optical signal modulation units are used for generating optical signals modulated by N subgrade modes;
the N optical amplification units are respectively connected with the N optical signal modulation units and are used for amplifying the optical signals modulated by the fundamental mode;
the N first mode conversion units are respectively connected to the N optical amplification units and the mode multiplexing unit, and configured to load the optical signal modulated by the fundamental mode onto a corresponding transmission mode channel to obtain N optical signals of different mode channels, and input the optical signals to the mode multiplexing unit;
the mode multiplexing unit is respectively connected with the N first mode conversion units and the communication optical fiber, and is configured to combine optical signals of N channels in different modes into one channel of optical signal in a first multiplexing mode;
the communication optical fiber is respectively connected with the mode multiplexing unit and the N module demodulation modules and is used for outputting a first multiplexing mode optical signal;
the N module demodulation modules are respectively connected with the communication optical fiber and the N photodetectors, and are configured to demodulate and mode-convert the N modules in the optical signals output by the communication optical fiber, respectively obtain Mi-path optical signals modulated in the mutually orthogonal mode corresponding to each module, synthesize one path of optical signals in the second multiplexing mode, and transmit the optical signals to the photodetectors;
the N photoelectric detectors are respectively connected with the N module demodulation modules and used for converting the second multiplexing mode optical signals into electric signals.
In a further aspect of the present invention, the module multiplexing-based optical alignment and detection communication system further includes: n signal acquisition and recovery modules; the N signal acquisition and recovery modules are respectively connected with the N photoelectric detectors and used for converting and recovering the electric signals output by the photoelectric detectors.
In a further aspect of the present invention, the optical signal modulation unit includes: the device comprises a light source, a signal generator and a photoelectric modulator; wherein, the first and the second end of the pipe are connected with each other,
the light source is connected with the photoelectric modulator and used for generating a light signal and transmitting the light signal to the photoelectric modulator;
the signal generator is connected with the photoelectric modulator and used for generating an electric signal and transmitting the electric signal to the photoelectric modulator;
the photoelectric modulator is respectively connected with the light source and the signal generator and is used for modulating the electric signal generated by the signal generator to the optical carrier wave provided by the light source.
In a further aspect of the present invention, the module demodulation module comprises: mi second mode conversion units, mi third mode conversion units and single-mode combination unit; wherein, the first and the second end of the pipe are connected with each other,
mi second mode conversion units in each module demodulation module are used for respectively converting all Mi modes of the same module into basic mode modes to obtain Mi basic mode modes;
the Mi third mode conversion units are correspondingly connected with the Mi second mode conversion units and used for converting Mi road mode into Mi road mutual orthogonal mode;
the single module merging unit is connected with the Mi third mode conversion units and is used for synthesizing the optical signals modulated by the Mi paths in the mutually orthogonal mode into optical signals in a second multiplexing mode.
According to a further configuration of the present invention, the communication fiber is a few-mode fiber or a multi-mode fiber.
In a further configuration of the present invention, an optical splitter is connected between the few-mode fiber and the module demodulation module or between the multimode fiber and the module demodulation module, and the first multiplexing mode signal is divided into N independent and identical optical signals by the optical splitter.
According to the further arrangement of the invention, the single-mode combined unit and the photoelectric detector are connected by adopting a few-mode optical fiber or a multi-mode optical fiber.
Based on the same inventive concept, the invention also provides a module multiplexing-based direct-modulation direct-detection optical communication method, which comprises the following steps:
amplifying the generated N roadbed mode modulated optical signal;
loading the amplified N-channel modulated optical signals to corresponding transmission mode channels to obtain N channels of optical signals of different mode channels;
synthesizing the optical signals of N paths of different mode channels into a first multiplexing mode optical signal and inputting the first multiplexing mode optical signal into a communication optical fiber;
dividing the first multiplexing mode optical signals passing through the communication optical fiber into N paths of independent and same optical signals;
respectively demodulating N modules in the N paths of independent and same optical signals and carrying out mode conversion, respectively obtaining Mi paths of optical signals modulated in a mutual orthogonal mode corresponding to each module, and synthesizing the Mi paths of optical signals into a second multiplexing mode optical signal;
and converting the second multiplexing mode optical signal into an electrical signal.
The present invention further provides that the step of demodulating and mode converting N modules in the N independent and same optical signals respectively, obtaining the Mi orthogonal mode modulated optical signals corresponding to each module respectively, and synthesizing the second multiplexing mode optical signals comprises:
respectively converting all Mi modes in the same module in the N paths of independent and same optical signals into a basic mode to obtain Mi basic mode modes;
converting the Mi roadbed mode into a Mi road mutual orthogonal mode;
and synthesizing the Mi paths of optical signals modulated by the mutually orthogonal modes into a second multiplexing mode optical signal.
The invention provides a direct alignment and light detection communication system and method based on module multiplexing, wherein the system comprises: the device comprises N optical signal modulation units, N optical amplification units, N first mode conversion units, a mode multiplexing unit, a communication optical fiber, N module demodulation modules and N photoelectric detectors; wherein N is greater than or equal to 1; the N optical signal modulation units are used for generating optical signals modulated by N subgrade modes; the N optical amplification units are respectively connected with the N optical signal modulation units and are used for amplifying the optical signals modulated by the fundamental mode; the N first mode conversion units are respectively connected to the N optical amplification units and the mode multiplexing unit, and configured to load the optical signal modulated by the fundamental mode onto a corresponding transmission mode channel to obtain N optical signals of different mode channels, and send the optical signals to the mode multiplexing unit; the mode multiplexing unit is respectively connected with the N first mode conversion units and the communication optical fiber and is used for combining N paths of optical signals of different mode channels into one path of first multiplexing mode optical signal; the communication optical fiber is respectively connected with the mode multiplexing unit and the N module demodulation modules and is used for outputting a first multiplexing mode optical signal; the N module demodulation modules are respectively connected with the rear part of the communication optical fiber and the N photodetectors, and are used for respectively demodulating and converting modes of the N modules in optical signals output by the communication optical fiber, obtaining Mi-path optical signals modulated in an orthogonal mode respectively corresponding to each module, synthesizing the Mi-path optical signals into a path of optical signals in a second multiplexing mode, and transmitting the optical signals to the photodetectors; the N photoelectric detectors are respectively connected with the N module demodulation modules and used for converting the second multiplexing mode optical signals into electric signals. The generated N optical signals modulated by the roadbed mode are amplified, then the amplified N optical signals modulated by the roadbed mode are loaded to corresponding sending mode channels to obtain N optical signals of different mode channels, then the N optical signals of the different mode channels are synthesized into a first multiplexing mode optical signal and input into a communication optical fiber, N modules in the optical signals output by the communication optical fiber are respectively demodulated and mode converted, then Mi optical signals modulated by mutually orthogonal modes are respectively obtained corresponding to each module, the Mi optical signals are synthesized into a second multiplexing mode optical signal, and the second multiplexing optical signal is converted into an electric signal. Therefore, the invention can realize the full receiving of N modules through N photoelectric detectors, improves the transmission performance and stability of the system, completes the operation of the filter module in the optical domain during demodulation and receiving, and has lower cost and simpler scheme. In addition, the invention does not need to be based on a module demultiplexing device, can be suitable for various mode vectors and different communication transmission optical fibers, and has strong universality.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a module multiplexing-based direct alignment and optical detection communication system in the present invention.
Fig. 2 is a schematic structural diagram of a two-module-multiplexing few-mode fiber-optic transmission-based optical alignment and detection system according to an embodiment of the present invention.
Fig. 3 is a diagram of mode field distribution of mode channels photographed by a CCD camera in a two-module multiplexing few-mode fiber transmission alignment detection optical communication system according to an embodiment of the present invention.
Fig. 4 is a flow chart of the module multiplexing-based direct alignment and optical detection communication in the present invention.
In the drawings, the reference numbers: 1. an optical signal modulation unit; 11. a light source; 12. a signal generator; 13. a photoelectric modulator; 2. a light amplification unit; 3. a first mode conversion unit; 4. a mode multiplexing unit; 5. a communication optical fiber; 6. a module demodulation module; 61. a second mode conversion unit; 62. a third mode conversion unit; 63. a single-mode combining unit; 7. a photodetector; 71. a single mode interface photodetector; 72. a multimode interface photodetector; 8. a signal acquisition and recovery module; 9. a delay fiber.
Detailed Description
The present invention provides a module multiplexing-based optical communication system and method for direct alignment and optical detection, and in order to make the purpose, technical scheme and effect of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
In the embodiments and claims, the articles "a", "an", "the" and "the" may include plural forms as well, unless the context specifically dictates otherwise. If there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the feature.
It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or wirelessly coupled. As used herein, the term "and/or" includes all or any element and all combinations of one or more of the associated listed items.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
In addition, technical solutions between the embodiments may be combined with each other, but must be based on the realization of the technical solutions by a person skilled in the art, and when the technical solutions are contradictory to each other or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
Referring to fig. 1 to fig. 3, the present invention provides a preferred embodiment of a module multiplexing based direct alignment detection optical communication system.
As shown in fig. 1, the present invention provides a module multiplexing based optical alignment detection system, which includes: the system comprises N optical signal modulation units 1, N optical amplification units 2, N first mode conversion units 3, a mode multiplexing unit 4, a communication optical fiber 5, N module demodulation modules 6 and N photoelectric detectors 7; wherein N is greater than or equal to 1; the N optical signal modulation units 1 are used for generating optical signals modulated by N subgrade modes; the N optical amplification units 2 are respectively connected to the N optical signal modulation units 1, and are configured to amplify the optical signal modulated by the fundamental mode; the N first mode conversion units 3 are respectively connected to the N optical amplification units 2 and the mode multiplexing unit 4, and are configured to load the optical signal modulated by the fundamental mode onto a corresponding transmission mode channel to obtain N optical signals of different mode channels and input the optical signals to the mode multiplexing unit 4; the mode multiplexing unit 4 is connected to the N first mode converting units 3 and the communication fiber 5, and is configured to combine optical signals of N channels in different modes into one channel of optical signal in a first multiplexing mode; the communication optical fiber 5 is connected to the mode multiplexing unit 6 and the N module demodulation modules 6, respectively, and is configured to output a first multiplexing mode optical signal; the N module demodulation modules 6 are respectively connected to the communication fiber 5 and the N photodetectors 7, and configured to demodulate and mode-convert the N modules in the optical signals output by the communication fiber 5, respectively obtain Mi-path optical signals modulated in the mutually orthogonal mode corresponding to each module, synthesize a second multiplexing mode optical signal, and transmit the second multiplexing mode optical signal to the photodetectors 7; the N photodetectors 7 are respectively connected to the N module demodulation modules 6, and are configured to convert the second multiplexing mode optical signal into an electrical signal.
Specifically, the N optical signal modulation units 1, the N optical amplification units 2, and the N first mode conversion units 3 correspond to the N module demodulation modules 6 and the N photodetectors 7, the N optical signal modulation units 1, the N optical amplification units 2, and the N first mode conversion units 3 form a transmitting end of the communication system, and the N module demodulation modules 6 and the N photodetectors 7 form a receiving end of the communication system, where N is a positive integer greater than or equal to 1.
The N optical signal modulation units 1 respectively generate symbols to be transmitted, thereby generating N independent optical signals based on fundamental mode modulation and transmitting the optical signals to the N optical amplification units 2, the N optical amplification units 2 respectively perform signal amplification processing on the N fundamental mode modulated optical signals and transmit the optical signals to the first mode conversion unit 3, the fundamental mode is converted into a corresponding high-order mode through the first mode conversion unit 3, thereby loading the fundamental mode modulated optical signals onto corresponding transmission mode channels respectively to obtain N optical signals of different mode channels and transmitting the optical signals to the mode multiplexing unit 4 to synthesize one path of first multiplexing mode optical signals through the mode multiplexing unit 4. Each channel mode belongs to different modules, the number of modes contained in each module is Mi (1 ≦ i ≦ N, excluding polarization), and the first mode conversion module may face different mode basis vectors, such as a linear polarization mode, an orbital angular momentum mode, or a vector mode. Then, the optical signal in the first multiplexing mode is input to the communication fiber 5, the optical signal transmitted through the communication fiber 5 is divided into N independent and identical optical signals, after the N modules are respectively demodulated and mode-converted by the N module demodulation modules 6 at the receiving end, the optical signals modulated in the Mi-path mutual orthogonal mode are respectively obtained corresponding to each module, and are synthesized into the optical signal in the second multiplexing mode and transmitted to the photodetector 7, and the optical signal is converted into an electrical signal by the photodetector 7.
In the above technical solution, the present invention amplifies the generated N optical signals modulated by the fundamental mode, loads the amplified N optical signals modulated by the fundamental mode to the corresponding transmission mode signals to obtain N optical signals of different mode channels, synthesizes the N optical signals of different mode channels into the first multiplexing mode optical signal and inputs the first multiplexing mode optical signal to the communication optical fiber, demodulates and converts the mode of the N modules in the optical signal transmitted by the communication optical fiber, obtains Mi optical signals modulated by the mutually orthogonal mode corresponding to each module, synthesizes the Mi optical signals into the second multiplexing mode optical signal, and converts the second multiplexing mode optical signal into the electrical signal. Therefore, the invention can realize N module full receiving through N photoelectric detectors 7, can improve the transmission performance, stability and reliability of the system on the premise of ensuring the communication transmission capacity, and can complete the operation of the filtering module in the optical domain during demodulation and receiving, thus aiming at a single module, the single module can complete the data acquisition and recovery only by the single photoelectric detector 7 and a single receiving channel, the diversity and combination receiving of a plurality of photoelectric detectors 7 are not needed, other algorithms are not needed to be introduced for data processing, the cost is lower, and the scheme is simpler. In addition, the invention does not need to be based on a module demultiplexing device (most module demultiplexers are still in a research stage, and few commercial products are available), can be suitable for various mode basis vectors and different communication transmission optical fibers, and has strong universality and flexible flexibility.
Referring to fig. 1, in a further implementation manner of an embodiment, the module multiplexing-based dcdc communication system further includes: n signal acquisition and recovery modules 8; the N signal acquisition and recovery modules 8 are respectively connected with the N photoelectric detectors 7 and used for converting and recovering the electric signals output by the photoelectric detectors 7.
Specifically, after the photodetector 7 converts the second multiplexing mode optical signal into an electrical signal, the signal acquisition and recovery module 8 completes the conversion and recovery from the electrical signal (analog signal) to a digital signal.
With continuing reference to fig. 1, in a further implementation of an embodiment, the optical signal modulation unit 1 includes: a light source 11, a signal generator 12 and a photoelectric modulator 13; wherein, the light source 11 is connected with the optoelectronic modulator 13, and is used for generating and transmitting a light signal to the optoelectronic modulator 13; the signal generator 12 is connected to the electro-optical modulator 13, and is used for generating an electrical signal and transmitting the electrical signal to the electro-optical modulator 13; the optical modulators 13 are respectively connected to the light source 11 and the signal generator 12, and are configured to modulate the electrical signal generated by the signal generator 12 onto an optical carrier provided by the light source 11.
Specifically, the light source 11 is a single-wavelength light source, and in practical implementation, the electro-optical modulator 13 modulates the electrical signal generated by the signal generator 12 onto a single-wavelength carrier provided by the light source 11 to generate a corresponding optical signal, that is, a fundamental mode modulated optical signal.
Continuing to refer to fig. 1, in a further implementation of an embodiment, the module demodulation module 6 includes: mi second mode converting units 61, mi third mode converting units 62 and a single-mode combining unit 63; the second mode converting units 61 in the demodulation modules of each module are configured to convert all the Mi modes of the same module into the fundamental mode respectively to obtain an Mi fundamental mode; the Mi third mode converting units 62 are correspondingly connected to the Mi second mode converting units 61, and are configured to convert an Mi fundamental mode into an Mi-path mutually orthogonal mode; the single module merging unit 63 is connected to the Mi third mode converting units 52, and is configured to combine the Mi optical signals modulated in the mutually orthogonal mode into a second multiplexing mode optical signal.
Specifically, in each of the module demodulation modules 6, each path of independent and same optical signal is equally divided into Mi paths of optical signals according to a ratio 1: mi, mi (i is greater than or equal to 1 and less than or equal to N) is the number of modes (including no polarization) included in the corresponding module, and then the Mi paths of optical signals are respectively converted into the fundamental mode through Mi second mode conversion units 61 to obtain the Mi fundamental mode.
After the Mi subgrade mode is obtained, the Mi subgrade mode is converted into an Mi-path mutual orthogonal mode through different third mode conversion units 62, then optical signals modulated based on the Mi-path mutual orthogonal mode are sent to a single-mode combining unit 63, and the Mi-path optical signals (the optical signals modulated by the Mi-path mutual orthogonal mode) are combined into one path of optical signals in a second multiplexing mode after mode multiplexing.
It should be noted that before entering the single-mode combining unit 63, it is necessary to ensure that the optical paths traversed by the Mi optical signals are the same, and ensure that the Mi optical signals are aligned in time, so that the optical paths are aligned, and a multipath effect is avoided.
Continuing to refer to fig. 1, in a further implementation of an embodiment, the communication fiber 5 is a few-mode fiber or a multimode fiber.
Specifically, the first multiplexing mode optical signal enters the communication transmission fiber 5 for transmission, where the communication transmission fiber 5 needs to support all the mode channels used, and is generally a few-mode fiber or a multi-mode fiber. In the used communication optical fiber, the modes with extremely close effective refractive indexes or the same modes are classified into the same module, and the different modes in the same module can generate random strong coupling in the communication optical fiber, so that the various modes in the same module can be randomly distributed at the output end of the optical fiber. While the mode channels of different modules are weakly coupled to some extent in the communication fiber, the specific module crosstalk depends on the fiber transmission length, the fiber characteristics, and the external environment.
Still referring to fig. 1, in a further implementation manner of an embodiment, an optical splitter is connected between the few-mode optical fiber and the module demodulation module 6 or between the multimode optical fiber and the module demodulation module 6, and an optical signal passing through the communication optical fiber 5 is divided into N independent and identical optical signals.
Specifically, after the first multiplexed mode optical signal is output from the communication fiber 5, the first multiplexed mode optical signal is divided into N independent and identical optical signals by an optical splitter.
In a further embodiment of an embodiment, referring to fig. 1, the single-mode combining unit 63 is connected to the photodetector 7 by a few-mode fiber or a multi-mode fiber.
Specifically, the second multiplexing mode optical signal enters the photodetector 7 through a corresponding transmission optical fiber, where the communication transmission optical fiber is a few-mode optical fiber or a multi-mode optical fiber supporting the transmission of the Mi-path mutually orthogonal modes. Because different modes corresponding to the Mi path optical signals are orthogonal with each other, interference does not occur in few-mode or mode optical fibers, thereby realizing that data information carried by all modes in a single module can be detected and received, ensuring that the optical signals received by the photoelectric detector 7 are stable and reliable,
referring to FIG. 2, for a better understanding of the present invention, a specific embodiment of the present invention is described below.
As shown in fig. 2, fig. 2 is a schematic structural diagram of a two-module multiplexing few-mode fiber transmission alignment detection optical communication system according to an embodiment. In the optical fiber communication system, an Orbital Angular Momentum (OAM) mode is used as a mode basis vector, an OAM mode with the order of 0-order and 3-order modules is used as a multiplexing transmission channel, and each mode loads 38Gbaud PAM-4 signals, so that the module multiplexing optical fiber communication system which completes 2-module full-receiving schemes based on 2 photoelectric detectors is realized. The light source 11 of the optical fiber communication system adopts a single-wavelength laser, the optical amplification unit 2 adopts an optical amplifier, the first mode conversion unit 3, the second mode conversion unit 61 and the third mode conversion unit 62 all adopt spiral phase plates, the mode multiplexing unit 4 and the single-mode combination unit 63 adopt an optical beam combiner, the photoelectric detector 7 adopts a single-mode interface photoelectric detector 71 and a multi-mode interface photoelectric detector 72, and the signal acquisition and recovery module 8 adopts an oscilloscope. The working principle is as follows:
first, at the transmitting end of the optical fiber communication system, the signal generator 12 generates a 38Gbaud PAM-4 electrical signal, and the electro-optical modulator 13 modulates the generated electrical signal onto a single carrier (with a wavelength of 1550.12 nm) output by the laser. The modulated optical signal is amplified by a preamplifier, and the amplified optical signal is equally divided into 2 paths. In two paths of optical signals, one path of the two paths of optical signals keeps a state of a fundamental mode, and the fundamental mode module only comprises one fundamental mode (without polarization). The fundamental mode modulated optical signal is decorrelated with another path after passing through a section of delay fiber 9. It should be noted that, in practice, the N optical signal modulation modules are independent, and in this example, a delay fiber is added to one of the two paths of signals, so that the two paths of signals are decorrelated. 9
In addition, the original fundamental mode of the other path of the optical fiber passes through the + 3-order spiral phase plate and is converted into a + 3-order OAM mode, and for the transmission optical fiber used in the embodiment, the module (3-order OAM module) to which the + 3-order OAM mode belongs comprises 2 modes (not including polarization), namely the + 3-order OAM mode and the-3-order OAM mode. The fundamental mode modulation optical signal and the + 3-order OAM mode modulation optical signal are multiplexed into one path through the optical beam combiner. And the optical signals after the multiplexing mode enter 5 kilometers of few-mode optical fiber for transmission. Wherein fig. 3 (a) and 3 (b) are: and at the output end of the communication optical fiber, the intensity distribution conditions of the two paths of mode fields are respectively observed by a CCD camera.
The output multiplexed optical signal after being transmitted through the communication optical fiber is equally divided into two paths. One path is directly sent to the single-mode interface photoelectric detector, the single-mode tail fiber of the single-mode interface photoelectric detector 71 directly filters a high-order mode in a multiplexing mode, detection of a fundamental mode modulation optical signal is achieved, and finally signal acquisition is completed through an oscilloscope. Thus, a single mode interface photodetector 71 can complete the reception of the fundamental mode module. And the other path is used for demodulation and reception of the 3-order OAM module. Because the module comprises two modes, the module is equally divided into two paths of optical signals, the two paths of optical signals pass through spiral phase plates with the order of-3/+ 3 respectively, the + 3/-3-order OAM in the multiplexing mode is reduced into a basic mode, the basic mode in the multiplexing mode is converted into an OAM mode with the order of-3/+ 3, and the two paths of optical signals are coupled into a single-mode jumper to filter out a high-order mode. Thereby completing demodulation of the 3-stage OAM module.
After two paths of optical signals modulated by the fundamental mode are obtained, the fundamental mode is converted into a + 3-order OAM mode after one path of optical signals passes through a + 3-order spiral phase plate. Therefore, the + 3-order OAM mode of the path and the basic mode of the other path are orthogonal, and the two paths are multiplexed into a path of optical signal through the optical beam combiner. The optical paths of the two optical signals passing through the optical combiner are consistent before entering the optical combiner, and the two optical signals are aligned in time.
And coupling the obtained multiplexing optical signal into a single few-mode optical fiber jumper. The few-mode optical fiber jumper wire supports 3-order OAM module transmission under the condition of the used wavelength (1550.12 nm). Fig. 3 (c) and 3 (d) are: and at the output end of the few-mode optical fiber jumper, the intensity distribution conditions of two modes are respectively observed by a CCD camera.
The multiplexed optical signals are sent to a single multi-mode interface photoelectric detector 72 through a few-mode optical fiber jumper, so that the detection of 3-order OAM module optical signals is realized, and finally, signal acquisition is completed through an oscilloscope. Thus, the single multimode interface photodetector 72 completes the reception of the 3 rd order OAM module.
Referring to fig. 4, in some embodiments, the present invention further provides a method for direct modulation and direct detection optical communication based on module multiplexing, which includes the steps of:
s100, amplifying the generated N roadbed mode modulated optical signal; specifically, as described in an embodiment of a module multiplexing-based direct alignment detection optical communication system, details are not repeated here.
S200, loading the amplified N-channel modulated optical signals to corresponding transmission mode channels to obtain N channels of optical signals of different mode channels; specifically, as described in an embodiment of a module multiplexing-based direct alignment detection optical communication system, details are not repeated here.
S300, synthesizing the optical signals of the N channels with different modes into a first multiplexing mode optical signal and inputting the optical signal into a communication optical fiber; specifically, as described in an embodiment of a module multiplexing-based direct alignment detection optical communication system, details are not repeated here.
S400, dividing the first multiplexing mode optical signal transmitted by the communication optical fiber into N paths of independent and same optical signals; specifically, as described in an embodiment of a module multiplexing-based direct alignment detection optical communication system, details are not repeated here.
S500, demodulating and mode converting N modules in the N paths of independent and same optical signals respectively, obtaining Mi paths of optical signals modulated in a mutually orthogonal mode corresponding to each module respectively, and synthesizing the Mi paths of optical signals into a second multiplexing mode optical signal; specifically, as described in an embodiment of a module multiplexing-based direct alignment detection optical communication system, details are not repeated here.
And S600, converting the second multiplexing mode optical signal into an electric signal. Specifically, as described in an embodiment of a module multiplexing-based optical alignment detection communication system, details are not repeated herein.
In some embodiments, step S500 includes the steps of:
s510, respectively converting all Mi modes in the same module in the N paths of independent and same optical signals into a basic mode to obtain Mi basic mode modes; specifically, as described in an embodiment of a module multiplexing-based optical alignment detection communication system, details are not repeated herein.
S520, converting the Mi roadbed mode into a Mi road mutual orthogonal mode; particularly, as described in an embodiment of a direct alignment and optical detection communication system based on module multiplexing, no further description is provided herein,
s530, the Mi-path mutually orthogonal mode modulated optical signals are combined into a second multiplexing mode optical signal. Specifically, as described in an embodiment of a module multiplexing-based optical alignment detection communication system, details are not repeated herein.
To sum up, the present invention provides a module multiplexing-based direct alignment and optical detection communication system and method, wherein the system includes: the device comprises N optical signal modulation units, N optical amplification units, N first mode conversion units, a mode multiplexing unit, a communication optical fiber, N module demodulation modules and N photoelectric detectors; wherein N is greater than or equal to 1; the N optical signal modulation units are used for generating N optical signals modulated by the subgrade mode; the N optical amplification units are respectively connected with the N optical signal modulation units and are used for amplifying the optical signals modulated by the fundamental mode; the N first mode conversion units are respectively connected to the N optical amplification units and the mode multiplexing unit, and configured to load the optical signal modulated by the fundamental mode onto a corresponding transmission mode channel to obtain N optical signals of different mode channels, and input the optical signals to the mode multiplexing unit; the mode multiplexing unit is respectively connected with the N first mode conversion units and the communication optical fiber and is used for combining N paths of optical signals of different mode channels into one path of first multiplexing mode optical signal; the communication optical fiber is respectively connected with the mode multiplexing unit and the N module demodulation modules and is used for outputting a first multiplexing mode optical signal; the N module demodulation modules are respectively connected to the communication optical fiber and the N photodetectors, and configured to demodulate and mode-convert the N modules in the optical signal output by the communication optical fiber, respectively obtain optical signals modulated in an Mi-path mutual orthogonal mode corresponding to each module, and synthesize optical signals in a second multiplexing mode to transmit to the photodetectors; the N photoelectric detectors are respectively connected with the N module demodulation modules and used for converting the second multiplexing mode optical signals into electric signals. Therefore, the invention can realize the full receiving of N modules through N photoelectric detectors, improves the transmission performance and stability of the system, completes the operation of the filter module in the optical domain during demodulation and receiving, and has lower cost and simpler scheme. In addition, the invention does not need to be based on a module demultiplexing device, can be suitable for various mode vectors and different communication transmission optical fibers, and has strong universality.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (9)
1. The utility model provides a directly, straighten and examine optical communication system based on module is multiplexing which characterized in that includes: the device comprises N optical signal modulation units, N optical amplification units, N first mode conversion units, a mode multiplexing unit, a communication optical fiber, N module demodulation modules and N photoelectric detectors; wherein N is greater than or equal to 1;
the N optical signal modulation units are used for generating optical signals modulated by N subgrade modes;
the N optical amplification units are respectively connected with the N optical signal modulation units and are used for amplifying the optical signals modulated by the fundamental mode;
the N first mode conversion units are respectively connected to the N optical amplification units and the mode multiplexing unit, and configured to load the optical signal modulated by the fundamental mode onto a corresponding transmission mode channel to obtain N optical signals of different mode channels, and input the optical signals to the mode multiplexing unit;
the mode multiplexing unit is respectively connected with the N first mode conversion units and the communication optical fiber, and is used for combining optical signals of N channels of different mode channels into one channel of first multiplexing mode optical signal;
the communication optical fiber is respectively connected with the mode multiplexing unit and the N module demodulation modules and is used for outputting a first multiplexing mode optical signal;
the N module demodulation modules are respectively connected with the communication optical fiber and the N photodetectors, and are configured to demodulate and mode-convert the N modules in the optical signals output by the communication optical fiber, respectively obtain Mi-path optical signals modulated in the mutually orthogonal mode corresponding to each module, synthesize one path of optical signals in the second multiplexing mode, and transmit the optical signals to the photodetectors;
the N photoelectric detectors are respectively connected with the N module demodulation modules and used for converting the second multiplexing mode optical signals into electric signals.
2. The modular multiplexing based direct alignment and detection optical communication system according to claim 1, further comprising: n signal acquisition and recovery modules; the N signal acquisition and recovery modules are respectively connected with the N photoelectric detectors and used for converting and recovering the electric signals output by the photoelectric detectors.
3. The module-multiplexing-based direct alignment and detection optical communication system according to claim 1, wherein the optical signal modulation unit comprises: the device comprises a light source, a signal generator and a photoelectric modulator; wherein, the first and the second end of the pipe are connected with each other,
the light source is connected with the photoelectric modulator and used for generating a light signal and transmitting the light signal to the photoelectric modulator;
the signal generator is connected with the photoelectric modulator and used for generating an electric signal and transmitting the electric signal to the photoelectric modulator;
the photoelectric modulator is respectively connected with the light source and the signal generator and is used for modulating the electric signal generated by the signal generator to the optical carrier wave provided by the light source.
4. The modular multiplexing based direct alignment and detection optical communication system according to claim 1, wherein the modular demodulation module comprises: mi second mode conversion units, mi third mode conversion units and single-mode combination unit; wherein, the first and the second end of the pipe are connected with each other,
the Mi second mode conversion units in each module demodulation module are used for respectively converting all Mi modes of the same module into basic mode modes to obtain Mi subgrade mode modes;
the Mi third mode conversion units are correspondingly connected with the Mi second mode conversion units and used for converting Mi road mode into Mi road mutual orthogonal mode;
the single module merging unit is connected with Mi third mode conversion units and is used for synthesizing Mi path optical signals modulated by the mutually orthogonal mode into optical signals of a second multiplexing mode.
5. The modular multiplexing based direct alignment and optical detection communication system according to claim 1, wherein the communication fiber is a few-mode fiber or a multi-mode fiber.
6. The modular multiplexing-based direct alignment detection optical communication system according to claim 5, wherein an optical splitter is connected between the few-mode fiber and the modular demodulation module or between the multimode fiber and the modular demodulation module, and the first multiplexed mode signal is divided into N independent and identical optical signals by the optical splitter.
7. The modular multiplexing-based direct alignment and optical detection communication system according to claim 4, wherein the single-module merging unit is connected with the photodetector by a few-mode fiber or a multi-mode fiber.
8. A module multiplexing-based direct alignment optical detection communication method is characterized by comprising the following steps:
amplifying the generated N roadbed mode modulated optical signal;
loading the amplified N-channel modulated optical signals to corresponding transmission mode channels to obtain N channels of optical signals of different mode channels;
synthesizing the optical signals of N channels with different modes into a first multiplexing mode optical signal and sending the first multiplexing mode optical signal into a communication optical fiber;
dividing the first multiplexing mode optical signal after passing through the communication optical fiber into N paths of independent and same optical signals;
respectively demodulating N modules in the N paths of independent and same optical signals and carrying out mode conversion, respectively obtaining Mi paths of optical signals modulated in a mutual orthogonal mode corresponding to each module, and synthesizing the Mi paths of optical signals into a second multiplexing mode optical signal;
and converting the second multiplexing mode optical signal into an electrical signal.
9. The method according to claim 8, wherein the step of demodulating and mode-converting N modules of the N independent and identical optical signals, respectively, to obtain Mi-channels of mutually orthogonal mode-modulated optical signals corresponding to each module, and synthesizing the second multiplexing mode optical signals comprises:
respectively converting all Mi modes of the same module in the N paths of independent and same optical signals into a Mi fundamental mode to obtain Mi fundamental mode modes;
converting the Mi roadbed mode into a Mi road mutual orthogonal mode;
and synthesizing the Mi paths of optical signals modulated by the mutually orthogonal modes into optical signals of a second multiplexing mode.
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