CN112564804A - All-fiber online mode conversion device - Google Patents
All-fiber online mode conversion device Download PDFInfo
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- CN112564804A CN112564804A CN202011364307.1A CN202011364307A CN112564804A CN 112564804 A CN112564804 A CN 112564804A CN 202011364307 A CN202011364307 A CN 202011364307A CN 112564804 A CN112564804 A CN 112564804A
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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
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
- H04B10/07955—Monitoring or measuring power
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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
- H04B10/29—Repeaters
- H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
- H04B10/2912—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form characterised by the medium used for amplification or processing
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Abstract
The invention discloses an all-fiber online mode conversion device, which comprises an optical signal preprocessing unit, a mode conversion unit, a signal shaping unit and a power feedback unit, wherein the optical signal preprocessing unit is used for preprocessing an optical signal; the mode conversion unit is respectively in communication connection with the optical signal preprocessing unit, the signal shaping unit and the power feedback unit; an input optical signal firstly enters an optical signal preprocessing unit, and is transmitted to a mode conversion unit after being filtered and operated at fixed power; the optical signal is subjected to mode conversion operation in the mode conversion unit and is divided into two paths of optical signals to be transmitted; one path of optical signal is transmitted to a power feedback unit, the power feedback unit converts the optical signal into a basic mode optical signal in a specified mode, and the power of the basic mode optical signal is measured and fed back to a mode conversion unit; the other path of optical signal is transmitted to a signal shaping unit, and is output as a mode conversion signal after energy compensation and filtering; the invention overcomes the problems of high cost, complex design and unmatched large-scale space mode exchange of the traditional mode conversion scheme.
Description
Technical Field
The invention relates to the field of optical communication, in particular to an all-fiber online mode conversion device.
Background
In recent years, as single-mode optical fiber transmission systems gradually approach the shannon limit, space division multiplexing and related transmission technologies thereof are widely researched by domestic and foreign research teams, so that the characteristic that independent information streams are simultaneously transmitted in multiple spatial modes is expected to be utilized, and breakthrough in the aspect of transmission capacity of optical fiber communication systems is realized. Meanwhile, with the continuous and deep research in the aspect, scientific research personnel put forward a concept of mode switching, and aim to improve the transmission capacity of an optical network and simultaneously compare a spatial channel with the traditional time division and frequency division channels to achieve the purpose of flexibly and intelligently switching the spatial mode channel in the optical network. The current major mode conversion techniques include: converting the high-order mode signal from the few-mode optical fiber into a fundamental mode signal by using a mode demultiplexer, and converting the fundamental mode signal into a specified high-order mode signal by using a mode multiplexer; and changing the effective refractive index in the fiber using a long period grating to effect conversion between modes, etc. The former method is complex in system composition and high in cost when being realized, and is not suitable for large-scale space mode exchange scenes. Meanwhile, the method can only support mode conversion between the basic mode and the high-order mode, but cannot realize the mode conversion between the high-order mode and the high-order mode, and does not meet the requirements of a mode exchange system. When the conversion between degenerate modes is performed in the mode conversion scheme based on the long-period grating, different operating environments (temperature, polarization state, fiber bending degree and the like) can generate different conversion efficiencies; meanwhile, the grating or waveguide conversion scheme has the problem of additional optical field coupling loss, and the signal power is lost, so that the method is not suitable for online system application. Therefore, in a flexible optical switching network, a more convenient and stable mode conversion scheme must be provided for any mode conversion between different modes of light, so that the stable operation of an optical network is ensured while the conversion efficiency is improved.
Disclosure of Invention
Aiming at the defects in the prior art, the all-fiber online mode conversion device provided by the invention solves the problems of high cost, complex design and unmatched mode exchange with a large-scale space mode in the traditional mode conversion scheme, and meets the requirement of mode free conversion between high-order modes; meanwhile, by carrying out feedback control, the influence of the working environment of the system on the mode conversion efficiency is reduced, and the reliability and the stability of the system under different application scenes are ensured.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows:
an all-fiber online mode conversion device, comprising: the device comprises an optical signal preprocessing unit, a mode conversion unit, a power feedback unit and a signal shaping unit; the mode conversion unit is respectively connected with the optical signal preprocessing unit, the signal shaping unit and the power feedback unit;
the optical signal preprocessing unit is used for receiving an input optical signal, filtering the input optical signal in a specified wavelength range and transmitting the optical signal with a fixed power to the mode conversion unit;
the mode conversion unit is used for receiving the optical signal transmitted by the optical signal preprocessing unit, dynamically adjusting according to the feedback signal sent by the power feedback unit, performing mode conversion on the optical signal, dividing the optical signal into two paths, and respectively transmitting the two paths of optical signals to the signal shaping unit and the power feedback unit;
the power feedback unit is used for receiving the optical signal transmitted by the mode conversion unit and converting the optical signal into a basic mode optical signal in a specified mode; sending the measured real-time power of the fundamental mode optical signal as a feedback signal to a mode conversion unit;
and the signal shaping unit is used for receiving the optical signal transmitted by the mode conversion unit, performing power compensation and noise filtering processing on the optical signal and finally outputting the mode conversion signal.
The invention has the beneficial effects that: the invention utilizes the influence of different radial expansion distances of the optical fiber expander on different mechanical stresses of the few-mode optical fiber, and simultaneously introduces a power feedback mechanism to adjust the radial displacement of the optical fiber expander in real time, thereby always ensuring that the mode conversion is in an efficient and stable state. Compared with the existing chip or grating mode conversion device, the invention directly realizes full-fiber mode conversion in the transmission few-mode fiber, and reduces the coupling loss caused by the transmission of the optical field between different working media. The device also realizes the increase of the working stability while reducing the cost, ensures the stability of the online mode conversion under different application scenes, and provides a feasible solution for deploying the spatial mode switching network in a large scale in the future.
Further, the optical signal preprocessing unit comprises a first optical filter with a specified wavelength and a first few-mode optical amplifier with rated output power;
the first optical filter is used for receiving an externally input optical signal, performing filtering processing in a specified wavelength range on the optical signal, and transmitting the filtered optical signal to the first few-mode optical amplifier;
and the first few-mode optical amplifier is used for amplifying the optical signal transmitted and filtered by the first optical filter and outputting the amplified optical signal with fixed power to the mode conversion unit.
The beneficial effects of the further scheme are as follows: the use of optical filters can produce a cleaner signal light in the frequency dimension, increasing the efficiency of the mode conversion process and the reliability of the power feedback unit. The filtered optical signal passes through a few-mode optical amplifier with rated output power, so that the output power of the optical signal of the unit is always kept the same, and the reference value of a feedback signal generated by a power feedback unit subsequently is ensured.
Further, the mode conversion unit comprises an optical fiber expander wound with a few-mode optical fiber, an adjustable piezoelectric controller, an optical isolator and a few-mode optical splitter;
a few-mode optical fiber with a specified length is wound in a groove of the optical fiber expander and is used for bearing an optical signal transmitted by the first few-mode optical amplifier, performing dynamic mode conversion on the optical signal according to a feedback signal sent by the power feedback unit and transmitting the optical signal to the optical isolator;
the adjustable voltage controller is used for dynamically adjusting output voltage according to a feedback signal sent by the power feedback unit, and changing the radial expansion distance of the few-mode optical fiber attached in the groove of the optical fiber expander through a wire;
the optical isolator is used for receiving the optical signal sent by the optical fiber expander, isolating backward reflected light and transmitting the optical signal to at least the mode optical splitter;
the few-mode optical splitter is used for splitting an optical signal transmitted by the optical isolator into two optical signals which are respectively injected into the power feedback unit and the signal shaping unit.
The beneficial effects of the further scheme are as follows: the voltage-adjustable controller dynamically adjusts output voltage according to the numerical value of an optical power meter in the power feedback unit, is connected with the optical fiber expander through a wire and controls the radial expansion distance of the optical fiber expander, so that the mode conversion effect of few-mode optical fibers attached in the groove is changed, and efficient and stable mode conversion between modes is guaranteed. After the optical signal after mode conversion passes through the optical isolator, power crosstalk of reflected light to mode coupling can be prevented, and high reliability of mode conversion is guaranteed.
Further, the power feedback unit comprises a mode demultiplexer and an optical power meter;
the mode demultiplexer is used for receiving one path of optical signals transmitted by the few-mode optical splitter, converting the input optical signals into basic mode optical signals in a specified mode, and transmitting the converted basic mode optical signals to the optical power meter through a single-mode optical fiber;
and the optical power meter is used for measuring the real-time power of the basic mode optical signal transmitted by the mode demultiplexer and sending the measured data as feedback information to the adjustable voltage controller.
The beneficial effects of the further scheme are as follows: because different temperatures, signal polarization states and bending degrees of optical fibers seriously affect the spatial distribution of an optical signal mode field, in order to ensure that a mode conversion device still keeps good performance under more complex and more various scenes, a power feedback unit is introduced to adjust the output voltage of the voltage-adjustable controller. The value of the optical power meter is used as feedback information to be sent to the adjustable voltage controller of the mode conversion unit, so that the output voltage of the mode conversion unit is dynamically adjusted, and the mode conversion efficiency is kept in an efficient and stable state. Because the output optical power is ensured to be a fixed value in the optical signal shaping unit, the matching degree between the optical signal mode injected into the mode demultiplexer and the mode (namely the mode into which the optical signal needs to be converted) specified by the mode demultiplexer can be analyzed by observing the value of the optical power meter, and the output voltage of the piezoelectric controller is regulated and controlled accordingly.
Further, the signal shaping unit comprises a second few-mode optical amplifier and a second optical filter with specified wavelength, which are connected with each other through a few-mode tail fiber;
the second few-mode optical amplifier is used for receiving another path of optical signal transmitted by the few-mode optical splitter, performing power compensation processing on the optical signal, and transmitting the compensated optical signal to a second optical filter;
the second optical filter is used for carrying out noise filtering processing on the compensated optical signals transmitted by the second few-mode optical amplifier and finally outputting mode conversion signals.
The beneficial effects of the further scheme are as follows: the optical signal split by the few-mode optical splitter is input into a few-mode optical amplifier, and the amplifier can compensate energy damage generated in the processes of mode conversion, isolation, splitting and the like of the optical signal. The compensated signals enter an optical filter with specified wavelength, redundant frequency components generated in the process are filtered, and the spectral purity of the output optical signals is ensured so as to meet the requirement of online communication.
Furthermore, the input ends and the output ends of the first optical filter, the first few-mode optical amplifier, the optical isolator, the few-mode optical splitter, the mode demultiplexer, the second few-mode optical amplifier and the second optical filter are all connected through few-mode optical fibers with the same parameters.
The beneficial effects of the further scheme are as follows: the optical signal is transmitted by adopting the few-mode optical fiber with the same parameters to maintain the mode field subsection form of the input optical signal, thereby ensuring the stability of the mode conversion device.
Drawings
FIG. 1 is a schematic structural diagram of an all-fiber on-line mode conversion device according to the present invention;
FIG. 2 is a graph illustrating radial expansion distance versus power count for a fiber expander according to the present invention;
FIG. 3 is a diagram illustrating comparison of mode field distribution results of optical signals before and after mode conversion according to the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and all matters produced by the invention using the inventive concept are protected.
As shown in fig. 1, an all-fiber online mode conversion device includes: the device comprises an optical signal preprocessing unit, a mode conversion unit, a power feedback unit and a signal shaping unit; the mode conversion unit is respectively connected with the optical signal preprocessing unit, the signal shaping unit and the power feedback unit;
the optical signal preprocessing unit is used for receiving an input optical signal, filtering the input optical signal in a specified wavelength range, filtering out interference generated by other wavelengths of light, and then enabling the power of the output optical signal to be a fixed value; outputting the processed input optical signal to the mode conversion unit;
the mode conversion unit is used for receiving the optical signal transmitted by the optical signal preprocessing unit, dynamically adjusting according to the feedback signal sent by the power feedback unit, performing mode conversion on the optical signal, dividing the optical signal into two paths, and respectively transmitting the two paths of optical signals to the signal shaping unit and the power feedback unit;
the power feedback unit is used for receiving the optical signal transmitted by the mode conversion unit and converting the optical signal into a basic mode optical signal in a specified mode; sending the measured real-time power of the fundamental mode optical signal as a feedback signal to a mode conversion unit;
and the signal shaping unit is used for receiving the optical signal transmitted by the mode conversion unit, performing power compensation and noise filtering processing on the optical signal, converting the optical signal into a specified signal mode with stable optical power and mode field distribution, and finally outputting a mode conversion signal.
The optical signal preprocessing unit receives an input optical signal through a few-mode optical fiber, filters out interference generated by other wavelengths of light by filtering the input optical signal in a specified wavelength range, sends the optical signal to a first few-mode optical amplifier through the few-mode optical fiber, and enables the output optical signal power of the unit to be a fixed value through the first few-mode optical amplifier with specified output power. And then injecting the preprocessed input optical signal into a mode conversion unit, and adjusting the output voltage through a power feedback and adjustable voltage controller, thereby controlling the optical fiber expander to complete the stable conversion between the optical signal modes. The optical signal passing through the mode conversion unit enters the power feedback unit and the signal shaping unit at the same time. The power feedback unit converts the optical signal after mode conversion into a basic mode optical signal by using the mode demultiplexer in a specified mode, and the mode conversion unit dynamically adjusts the output voltage of the adjustable voltage controller by taking the real-time power of the basic mode optical signal as a feedback signal to realize stable mode conversion of the optical signal in the few-mode optical fiber. In addition, after the optical signal entering the signal shaping unit is compensated and shaped in dimensions such as power, frequency and the like, a specified mode signal with stable optical power and mode field distribution after mode conversion is obtained at the output end.
In the embodiment of the invention, the optical signal preprocessing unit comprises a first optical filter with specified wavelength and a first few-mode optical amplifier with rated output power;
the first optical filter is used for receiving an externally input optical signal, performing filtering processing in a specified wavelength range on the optical signal, and transmitting the filtered optical signal to the first few-mode optical amplifier; the use of optical filters can produce a cleaner signal light in the frequency dimension, increasing the efficiency of the mode conversion process and the reliability of the power feedback unit.
And the first few-mode optical amplifier is used for amplifying the optical signal transmitted and filtered by the first optical filter and outputting the amplified optical signal with fixed power to the mode conversion unit. The filtered optical signal passes through a few-mode optical amplifier with rated output power, so that the output power of the optical signal of the unit is always kept the same, and the reference value of a feedback signal generated by a power feedback unit subsequently is ensured.
The method comprises the steps that an externally input optical signal is filtered in a specified wavelength range through a first optical filter, purer signal light is generated in a frequency dimension, the efficiency of a mode conversion process and the reliability of a power feedback unit are increased, then the filtered optical signal passes through a few-mode optical amplifier with rated output power, the optical signal output power of the unit is always kept the same as a fixed value, the reference value of a feedback signal generated by the power feedback unit is guaranteed, and finally the first few-mode optical amplifier transmits the optical signal to the mode conversion unit through a few-mode optical fiber.
In the embodiment of the invention, the mode conversion unit comprises an optical fiber expander wound with a few-mode optical fiber, an adjustable voltage controller, an optical isolator and a 50:50 few-mode optical splitter;
the few-mode optical fiber with a specified length is wound in the groove of the optical fiber expander and is used for bearing an optical signal which is transmitted by the first few-mode optical amplifier and is subjected to filtering and amplification processing and transmitting the optical signal to the optical isolator;
the adjustable voltage controller is used for dynamically adjusting output voltage according to a feedback signal sent by the power feedback unit, and changing the radial expansion distance of the few-mode optical fiber attached in the groove of the optical fiber expander through a wire; the voltage-adjustable controller dynamically adjusts output voltage according to the numerical value of an optical power meter in the power feedback unit, is connected with the optical fiber expander through a wire and controls the radial expansion distance of the optical fiber expander, so that the mode conversion effect of few-mode optical fibers attached in the groove is changed, and efficient and stable mode conversion between modes is guaranteed.
The optical isolator is used for receiving the optical signal sent by the optical fiber expander, isolating backward reflected light and transmitting the optical signal to at least the mode optical splitter; the input end of the optical isolator is connected with the output end of the few-mode optical fiber in the optical fiber expander, and the parameters of the few-mode tail fiber of the optical isolator are the same as those of the few-mode optical fiber in the optical fiber expander. After the optical signal after mode conversion passes through the optical isolator, power crosstalk of reflected light to mode coupling can be prevented, and high reliability of mode conversion is guaranteed.
The few-mode optical splitter is used for splitting an optical signal transmitted by the optical isolator into two optical signals, and the two optical signals are respectively injected into the power feedback unit and the signal shaping unit through few-mode tail fibers with the same parameters.
The filtered optical signal is carried by the few-mode optical fiber and injected into the mode conversion unit, because the few-mode bare fiber with a certain length carrying the optical signal is wound in the groove around the optical fiber expander, different mechanical stresses can be generated on the few-mode optical fiber by different displacements generated by the optical fiber expander in the radial direction, so that different mode conversion effects are generated, the voltage-adjustable controller dynamically adjusts the output voltage according to the numerical value of an optical power meter in the power feedback unit, the optical fiber expander is connected through an electric wire, and the radial expansion distance of the optical fiber expander is controlled, so that the mode conversion effect of the few-mode optical fiber attached in the groove is changed, and efficient and stable mode conversion between modes is ensured. The input end of the optical isolator is connected with the output end of the few-mode optical fiber in the optical fiber expander, and the parameters of the few-mode tail fiber of the optical isolator are the same as those of the few-mode optical fiber in the optical fiber expander. After the optical signal after mode conversion passes through the optical isolator, power crosstalk of reflected light to mode coupling can be prevented, and high reliability of mode conversion is guaranteed. After output optical signals of the optical isolator are injected into the few-mode optical splitter through the few-mode optical fibers, the generated two paths of optical signals are respectively injected into the power feedback unit and the signal shaping unit through the few-mode tail fibers with the same parameters.
In the embodiment of the invention, the power feedback unit comprises a mode demultiplexer and an optical power meter;
the spatial distribution of the optical signal mode field is severely affected by different temperatures, signal polarization states and the degree of bending of the fiber. Therefore, in order to keep the mode conversion device with good performance under more complex and various scenes, a power feedback unit is introduced to regulate the output voltage of the voltage-adjustable controller.
The mode demultiplexer is used for receiving one path of optical signals transmitted by the few-mode optical splitter, converting the input optical signals into basic mode optical signals in a specified mode, and transmitting the converted basic mode optical signals to the optical power meter through a single-mode optical fiber; the input end of the mode demultiplexer is connected with one of the output ends of the optical splitters in the mode conversion unit through few-mode tail fibers, and signals split by the optical splitters are injected into the mode demultiplexer; the mode demultiplexer converts an input optical signal into a fundamental mode optical signal in a specified mode and measures the fundamental mode optical signal with an optical power meter.
The optical power meter is used for measuring the real-time power of the basic mode optical signal transmitted by the mode demultiplexer and sending the measured data serving as feedback information to the voltage-adjustable controller; when the mode of the optical signal converted by the mode conversion unit does not match the mode specified by the mode demultiplexer (i.e. the mode to which the mode conversion is required), the value of the optical power meter will be lower than the decision threshold, and when the matching degree between the two is increased, the optical power will approach the decision threshold. Therefore, according to the above rule, the value of the optical power meter can be used as feedback information to be sent to the voltage-adjustable controller of the mode conversion unit, so as to realize the dynamic adjustment of the output voltage thereof, and keep the mode conversion efficiency in an efficient and stable state.
One branch is injected into the mode demultiplexer by the optical signal of the mode conversion unit. The optical signal is then converted to the fundamental mode in the specified mode by a mode demultiplexer, and the optical power of the fundamental mode signal is measured by an optical power meter. Because the output optical power is ensured to be a fixed value in the optical signal shaping unit, the matching degree between the optical signal mode injected into the mode demultiplexer and the mode (namely the mode into which the optical signal needs to be converted) specified by the mode demultiplexer can be analyzed by observing the value of the optical power meter, and the output voltage of the piezoelectric controller is regulated and controlled accordingly. Tests show that the radial displacement of the optical fiber expander and the optical power meter of the power feedback unit approximately show the relationship shown in FIG. 2, and the feasibility of mode conversion of the device is proved.
In the embodiment of the invention, the signal shaping unit comprises a second few-mode optical amplifier and a second optical filter with specified wavelength, which are connected with each other through a few-mode tail fiber; and the devices are interconnected through few-mode tail fibers with the same parameters as the few-mode optical fibers.
The second few-mode optical amplifier is used for receiving another path of optical signal transmitted by the few-mode optical splitter, performing power compensation on loss generated by the optical signal in the processes of mode conversion, isolation and the like, and transmitting the compensated optical signal to a second optical filter;
the second optical filter is used for carrying out noise filtering processing on the compensated optical signals transmitted by the second few-mode optical amplifier and finally outputting mode conversion signals. The optical signal after power compensation enters the optical filter with the specified wavelength again, noise with other wavelengths generated in the operation process of the mode conversion unit and the signal shaping unit is filtered, and the purity of the spectrum of the output optical signal is ensured so as to meet the requirement of online communication.
The optical signal passing through the mode conversion unit, except for one path of optical signal entering the power feedback unit, the other path of output optical signal sequentially enters a second few-mode optical amplifier and a second optical filter according to the sequence, and power compensation and spectrum filtering are respectively carried out on the optical signal after mode conversion, branching, backward isolation and other operations, so that the output signal light meets the quality requirement of continuous communication. Fig. 3 is a distribution diagram of mode fields of the output optical signals of the signal shaping unit before and after mode conversion, which is observed by the infrared camera, and the distribution of the mode fields after mode conversion is orthogonal to the distribution of the mode fields before mode conversion, which shows that the device of the present invention has a good mode conversion effect.
In the embodiment of the invention, the input ends and the output ends of the first optical filter, the first few-mode optical amplifier, the optical isolator, the few-mode optical splitter, the mode demultiplexer, the second few-mode optical amplifier and the second optical filter are all connected through few-mode optical fibers with the same parameters. The optical signal is transmitted by adopting the few-mode optical fiber with the same parameters to maintain the mode field subsection form of the input optical signal, thereby ensuring the stability of the mode conversion device.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.
Claims (6)
1. An all-fiber on-line mode conversion device, comprising: the device comprises an optical signal preprocessing unit, a mode conversion unit, a power feedback unit and a signal shaping unit; the mode conversion unit is respectively connected with the optical signal preprocessing unit, the signal shaping unit and the power feedback unit;
the optical signal preprocessing unit is used for receiving an input optical signal, filtering the input optical signal in a specified wavelength range and transmitting the optical signal with fixed power to the mode conversion unit;
the mode conversion unit is used for receiving the optical signal transmitted by the optical signal preprocessing unit, dynamically adjusting according to the feedback signal sent by the power feedback unit, performing mode conversion on the optical signal, dividing the optical signal into two paths, and respectively transmitting the two paths of optical signals to the signal shaping unit and the power feedback unit;
the power feedback unit is used for receiving the optical signal transmitted by the mode conversion unit and converting the optical signal into a basic mode optical signal in a specified mode; sending the measured real-time power of the fundamental mode optical signal as a feedback signal to the mode conversion unit;
and the signal shaping unit is used for receiving the optical signal transmitted by the mode conversion unit, performing power compensation and noise filtering processing on the optical signal and finally outputting a mode conversion signal.
2. The all-fiber on-line mode conversion device according to claim 1, wherein said optical signal preprocessing unit comprises a first optical filter and a first few-mode optical amplifier with rated output power;
the first optical filter is used for receiving an externally input optical signal, performing filtering processing in a specified wavelength range on the optical signal, and transmitting the filtered optical signal to the first few-mode optical amplifier;
the first few-mode optical amplifier is configured to amplify the optical signal filtered by the first optical filter, and output the amplified optical signal with fixed power to the mode conversion unit.
3. The all-fiber in-line mode conversion device of claim 2, wherein the mode conversion unit comprises a fiber expander, a tunable piezoelectric controller, an optical isolator and a few-mode optical splitter;
a few-mode optical fiber with a specified length is wound in a groove of the optical fiber expander and is used for bearing an optical signal transmitted by the first few-mode optical amplifier, performing dynamic mode conversion on the optical signal according to a feedback signal sent by the power feedback unit and transmitting the optical signal to the optical isolator;
the adjustable voltage controller is used for dynamically adjusting output voltage according to a feedback signal sent by the power feedback unit and changing the radial expansion distance of the few-mode optical fiber attached in the groove of the optical fiber expander;
the optical isolator is used for receiving the optical signal sent by the optical fiber expander, isolating backward reflected light and transmitting the optical signal to the at least one mode splitter;
the few-mode optical splitter is used for splitting an optical signal transmitted by the optical isolator into two optical signals which are respectively injected into the power feedback unit and the signal shaping unit.
4. The all-fiber online mode conversion device according to claim 3, wherein the power feedback unit comprises a mode demultiplexer and an optical power meter;
the mode demultiplexer is configured to receive one path of optical signals transmitted by the few-mode optical splitter, convert the input optical signals into fundamental mode optical signals in a designated mode, and transmit the converted fundamental mode optical signals to the optical power meter through a single-mode optical fiber;
the optical power meter is used for measuring the real-time power of the basic mode optical signal transmitted by the mode demultiplexer and sending the measured data serving as feedback information to the voltage-adjustable controller; .
5. The all-fiber in-line mode conversion device according to claim 4, wherein said signal shaping unit comprises a second few-mode optical amplifier and a second optical filter connected to each other through a few-mode pigtail;
the second few-mode optical amplifier is used for receiving another path of optical signal transmitted by the few-mode optical splitter, performing power compensation processing on the optical signal, and transmitting the compensated optical signal to the second optical filter;
and the second optical filter is used for carrying out noise filtering processing on the compensated optical signal transmitted by the second few-mode optical amplifier and finally outputting a mode conversion signal.
6. The all-fiber in-line mode conversion device according to claim 5, wherein the input and output ends of said first optical filter, said first few-mode optical amplifier, said optical isolator, said few-mode optical splitter, said mode demultiplexer, said second few-mode optical amplifier and said second optical filter are all connected by a few-mode fiber with the same parameters.
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