CN114614330A - Optical frequency comb generation method based on multi-frequency laser modulation and nonlinear spectrum spreading - Google Patents

Abstract

The invention discloses a method for generating an optical frequency comb based on multi-frequency laser modulation and nonlinear spectrum spreading, which comprises the steps of generating a frequency sideband through multi-frequency laser modulation to obtain an initial optical frequency comb; self-phase modulation in a highly nonlinear medium is utilized to broaden the spectrum and realize broadband optical frequency comb output. The invention provides a brand-new optical frequency comb generation method, which can realize frequency quantity multiplication, spectrum flatness optimization control and frequency comb bandwidth expansion by combining multi-frequency laser oscillation, modulation generation frequency sidebands and nonlinear frequency spectrum expansion, has a simple structure, is easy to realize, and is expected to provide brand-new technical reference for upgrading the performance of a dense wavelength division multiplexing system.

Description

Optical frequency comb generation method based on multi-frequency laser modulation and nonlinear spectrum spreading

Technical Field

The invention belongs to the interdisciplinary field of laser optics, nonlinear optics, optical communication and microwave photonics, in particular to a method for generating frequency sidebands through multi-frequency laser modulation, expanding frequency spectrum by utilizing self-phase modulation in a high nonlinear medium and finally realizing broadband optical frequency comb output, and particularly relates to an optical frequency comb generating method, system and storage medium based on multi-frequency laser modulation and nonlinear frequency spectrum expansion.

Background

The photoelectric information system is a complex system for realizing various information functions through a photoelectric device, and the photoelectric information system which is most widely applied at present is an optical fiber communication system. The optical fiber communication has the advantages of long transmission distance, large information capacity, stable system performance, electromagnetic interference resistance and the like, and is the most commonly adopted information transmission scheme of a fixed communication network; with the continuous development of wavelength division multiplexing, partial division multiplexing, time division multiplexing, mode division multiplexing and other technologies, the optical fiber communication rate is an exponential leap, and the capacity expansion and upgrading process of the modern communication network is promoted. The most mature multiplexing technology in the optical fiber communication system is the wavelength division multiplexing technology, and the communication speed is doubled by carrying different information by multi-wavelength optical carriers and transmitting the information by optical fibers. The performance of wdm systems is highly dependent on the performance of the multi-wavelength light source, and in particular, the multi-wavelength light source needs to generate equally spaced laser outputs at frequencies consistent with the International Telecommunications Union (ITU) frequency spacing standard, with high signal-to-noise ratio and spectrally flat broadband output characteristics. The multi-wavelength light source realized by the traditional discrete laser spectrum synthesis faces the bottleneck problems of high cost, limited channel number, poor stability and the like; the frequency domain shaping of the broad spectrum laser by using the multi-wavelength narrow linewidth band-pass filter also faces huge energy waste. Therefore, at present, the center of gravity of research on the multi-wavelength light source begins to shift to optical frequency combing, that is, the multi-wavelength laser with equal frequency intervals and comb-like spectral distribution is simultaneously output through various optical nonlinear effects.

The optical frequency comb has a plurality of generation modes, wherein the most common mode utilizes the excited four-wave mixing effect of a microcavity with high quality factor; in addition, the methods of ultrafast laser mode locking, high-speed optical modulation, self-phase modulation and the like can also realize optical frequency comb output.

Disclosure of Invention

Based on the problems of the prior art, the technical problem to be solved by the invention is how to generate multi-frequency laser output by a common gain medium multi-frequency laser; modulating a multi-frequency laser generating frequency equal-interval sideband by using a high-speed modulator to obtain an initial optical frequency comb; self-phase modulation in a high nonlinear medium is utilized to broaden the spectrum, and finally, broadband optical frequency comb output is achieved.

In order to achieve the effect, the optical frequency comb generating method based on multi-frequency laser modulation and nonlinear spectrum spreading provided by the invention comprises the steps of generating multi-frequency laser output through a common gain medium multi-frequency laser, modulating the multi-frequency laser by using a high-speed modulator, generating frequency equal-interval sidebands to obtain an initial optical frequency comb, and realizing broadband optical frequency comb output by using self-phase modulation spread spectrum in a high nonlinear medium, wherein the common gain medium multi-frequency laser consists of a pumping source, a gain medium and a multi-frequency resonant cavity, the high-speed modulator is used for modulating the amplitude or phase of the multi-frequency laser, generating a series of frequency sidebands at equal intervals near an input frequency component, enabling the frequency intervals to be consistent with modulation repetition frequency, the output frequency quantity exceeds the input frequency quantity and preliminarily forms comb distribution in a frequency domain, and guiding the initial optical frequency comb into the high nonlinear medium, By generating new frequency components by self-phase modulation and realizing the output optical frequency comb of spectrum spreading, energy can be transferred among the frequency components by the nonlinear effect of self-phase modulation and the like.

Preferably, the multi-frequency laser is output by a common gain medium multi-frequency laser, the laser is composed of a pump light source, a Wavelength Division Multiplexer (WDM), an erbium-doped fiber (EDF), a high reflection fiber grating (HR-FBG), and a low reflection fiber grating (LR-FBG), three groups of fiber gratings with different wavelengths form three sets of resonant cavities, and three sets of three-channel laser outputs with wavelengths of 1549.6nm, 1550nm, and 1550.4nm are generated after the three sets of fiber gratings share the pump light-excited EDF gain medium with 976nm, that is, three-channel laser outputs with frequency intervals of 50 GHz.

Preferably, the phase of the three-frequency laser is modulated by a 10GHz sine wave simultaneously, frequency sidebands with the center frequency of the laser as an axis and the frequency interval of 10GHz and with symmetrical distribution and intensity size meeting the Bessel function are generated, when the phase modulation coefficient is 1, the normalized intensity of two adjacent lasers in the frequency domain and the middle frequency sidebands thereof is approximately 0.77, 0.44, 0.13, 0.44 and 0.77, and the initial frequency comb output with approximately the same frequency components can be realized by changing the phase modulation coefficient.

Preferably, the initial frequency comb is coupled into a high nonlinear waveguide, and spectrum broadening is generated under the combined action of third-order nonlinear effects such as self-phase modulation and the like and waveguide dispersion, so that a broadband output optical frequency comb is obtained.

Preferably, the pumping means includes, but is not limited to, electrical pumping, optical pumping, and hybrid pumping.

Preferably, the gain medium may be a crystal or a doped fiber; the multi-frequency resonant cavity needs to provide positive feedback for a plurality of equally spaced frequencies.

Preferably, the modulation waveform includes but is not limited to sine wave, square wave, sawtooth wave, the modulation parameter can be adjusted flexibly to change the output initial frequency comb frequency domain distribution; the sidebands of the respective input frequency components may overlap each other.

Preferably, the high nonlinear medium has low transmission loss, high nonlinear coefficient and near-zero anomalous dispersion characteristics, and includes, but is not limited to, high nonlinear fiber or photonic crystal fiber, chip integrated semiconductor waveguide, and periodically poled lithium niobate crystal.

A system for realizing the optical frequency comb generation method based on the multi-frequency laser modulation and the nonlinear spectrum spreading comprises a common gain medium multi-frequency laser, a pumping source, a gain medium and a multi-frequency resonant cavity, and further comprises:

the multi-frequency laser output module is used for generating multi-frequency laser output through the common gain medium multi-frequency laser;

the multi-frequency laser modulation module is used for modulating multi-frequency laser by using a high-speed modulator, generating frequency equal-interval sidebands and obtaining an initial optical frequency comb;

the nonlinear spectrum spreading module is used for expanding the narrow-band optical frequency comb into a wide-band optical frequency comb by utilizing self-phase modulation spread spectrum in a high nonlinear medium;

the pumping means include, but are not limited to, electrical pumping, optical pumping, hybrid pumping;

the gain medium may be a crystal or a doped fiber;

the multi-frequency resonant cavity needs to provide positive feedback for a plurality of equally spaced frequencies, and includes, but is not limited to, a multi-oscillation frequency standing wave cavity, an annular cavity containing a multi-channel filter, a fiber Fabry-Perot cavity formed by a plurality of sets of fiber gratings, a chip integrated microcavity doped with rare earth ions, and a multi-frequency distributed feedback cavity.

A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the above-mentioned method.

Compared with the prior art, the invention provides a brand-new optical frequency comb generation method, which can realize frequency quantity multiplication, spectrum flatness optimization control and frequency comb bandwidth expansion by combining the action mechanisms of multi-frequency laser oscillation, frequency sideband generation by modulation, frequency broadening caused by self-phase modulation and the like, has a simple structure, is easy to realize, and is expected to provide brand-new technical reference for the performance upgrade of a dense wavelength division multiplexing system.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 shows a schematic diagram of the optical frequency comb generation principle based on multi-frequency laser modulation and nonlinear spectrum spreading in the present invention.

Detailed Description

Features and exemplary embodiments of various aspects of the present invention will be described in detail below, and in order to make objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention. It will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The invention provides an embodiment of an optical frequency comb generation method based on multi-frequency laser modulation and nonlinear spectrum spreading, which comprises the steps of generating multi-frequency laser output through a common gain medium multi-frequency laser, modulating the multi-frequency laser through a high-speed modulator, generating frequency equal interval sidebands to obtain an initial optical frequency comb, and realizing broadband optical frequency comb output through self-phase modulation spread spectrum in a high nonlinear medium, wherein the common gain medium multi-frequency laser consists of a pumping source, a gain medium and a multi-frequency resonant cavity, the high-speed modulator is used for modulating the amplitude or the phase of the multi-frequency laser, generating a series of frequency sidebands at equal intervals near an input frequency component, enabling the frequency interval to be consistent with modulation repetition frequency, enabling the output frequency quantity to exceed the input frequency quantity and preliminarily form comb distribution in a frequency domain, introducing the initial optical frequency comb into the high nonlinear medium, and further generating new frequency component through self-phase modulation, The energy of the output optical frequency comb for realizing spectrum spreading is transferred among frequency components through nonlinear effects such as self-phase modulation.

In some embodiments, an initial frequency comb is coupled into a highly nonlinear waveguide, and spectral broadening is generated under the combined action of third-order nonlinear effects such as self-phase modulation and waveguide dispersion, so that a broadband output optical frequency comb is obtained.

In some embodiments, pumping means include, but are not limited to, electrical pumping, optical pumping, hybrid pumping.

In some embodiments, the gain medium may be a crystal or doped fiber; the multi-frequency resonant cavity needs to provide positive feedback for a plurality of equally spaced frequencies.

In some embodiments, the modulation waveform includes but is not limited to sine wave, square wave, sawtooth wave, the modulation parameter can be flexibly adjusted to change the output initial frequency comb frequency domain distribution; the sidebands of the respective input frequency components may overlap each other.

In some embodiments, the highly nonlinear medium must have low transmission loss, high nonlinear coefficient and near-zero anomalous dispersion characteristics, including but not limited to highly nonlinear fiber or photonic crystal fiber, chip integrated semiconductor waveguide, periodically poled lithium niobate crystal.

The invention provides a system embodiment for realizing the optical frequency comb generating method based on the multi-frequency laser modulation and the nonlinear spectrum spread, which comprises a common gain medium multi-frequency laser, a pumping source, a gain medium, a multi-frequency resonant cavity and the like, and further comprises the following steps:

the multi-frequency laser output module is used for generating multi-frequency laser output through the common gain medium multi-frequency laser;

the multi-frequency laser modulation module is used for modulating multi-frequency laser by using a high-speed modulator, generating frequency equal-interval sidebands and obtaining an initial optical frequency comb;

the nonlinear spectrum spreading module is used for expanding the narrow-band optical frequency comb into a wide-band optical frequency comb by utilizing self-phase modulation spread spectrum in a high nonlinear medium;

in some embodiments, pumping means include, but are not limited to, electrical pumping, optical pumping, hybrid pumping;

in some embodiments, the gain medium may be a crystal or doped fiber;

in some embodiments, the multi-frequency resonant cavity is required to provide positive feedback for a plurality of equally spaced frequencies, including but not limited to a multi-oscillation frequency standing wave cavity, an annular cavity containing a multi-channel filter, a fiber fabry-perot cavity formed by a plurality of sets of fiber gratings, a chip integrated microcavity doped with rare earth ions, and a multi-frequency distributed feedback cavity.

As shown in fig. 1, the present invention provides an embodiment of an optical frequency comb generation method based on multi-frequency laser modulation and nonlinear spectrum expansion, first, multi-frequency laser is output by a common gain medium multi-frequency laser, the laser is composed of a pump light source, a Wavelength Division Multiplexer (WDM), an erbium-doped fiber (EDF), a high reflection fiber grating (HR-FBG), and a low reflection fiber grating (LR-FBG), three sets of fiber gratings with different wavelengths form three sets of resonant cavities, and three channels of laser outputs with wavelengths of 1549.6nm, 1550nm, and 1550.4nm are generated after sharing an EDF gain medium excited by 976nm pump light, that is, three-frequency laser outputs with frequency interval of 50 GHz; secondly, a 10GHz sine wave is used for simultaneously modulating the phases of three-frequency lasers to generate frequency sidebands which take the central frequency of the lasers as an axis, have the frequency interval of 10GHz, are symmetrically distributed, and have the intensity which meets the Bessel function, when the phase modulation coefficient is 1, the normalized intensity of two lasers adjacent to each other in the frequency domain and the middle frequency sidebands thereof is approximately 0.77, 0.44, 0.13, 0.44 and 0.77, and the initial frequency comb output with approximately the same frequency components can be realized by changing the phase modulation coefficient; and finally, coupling the initial frequency comb into a high nonlinear waveguide, and generating spectrum broadening under the combined action of third-order nonlinear effects such as self-phase modulation and the like and waveguide dispersion to obtain a broadband output optical frequency comb.

The invention provides an embodiment of an optical frequency comb generation method based on multi-frequency laser modulation and nonlinear spectrum spreading, which comprises the following steps:

s101, generating multi-frequency laser output through a common gain medium multi-frequency laser, wherein the multi-frequency laser can be a multi-longitudinal-mode laser, a multi-channel filtering ring laser and a multi-grating fiber laser;

s102, modulating a multi-frequency laser through a high-speed modulator, generating frequency equal-interval sidebands and forming an initial optical frequency comb; the modulation optical freedom degree can be amplitude or phase, the modulation waveform can be sine wave or square wave, the modulation parameter needs to be flexibly adjusted to obtain frequency sideband output with flat spectrum, and the multi-frequency laser sidebands can be mutually overlapped;

s103, realizing broadband optical frequency comb output by utilizing self-phase modulation spread spectrum in a high nonlinear medium, wherein the high nonlinear medium has low transmission loss, high nonlinear coefficient and near-zero anomalous dispersion characteristics.

The invention provides an embodiment of a method for generating an optical frequency comb based on multi-frequency laser modulation and nonlinear spectrum spreading.

In some embodiments, the multi-frequency resonant cavity is composed of a pumping source, a gain medium and a multi-frequency resonant cavity, and the pumping mode includes but is not limited to electrical pumping, optical pumping and mixed pumping, and the number of the pumping sources is not limited; the gain medium may be a crystal or a doped fiber; the multi-frequency resonant cavity needs to provide positive feedback for a plurality of equally spaced frequencies, and the specific implementation modes include, but are not limited to, a multi-oscillation frequency standing wave cavity, an annular cavity containing a multi-channel filter, an optical fiber Fabry-Perot cavity formed by a plurality of sets of fiber gratings, a rare earth ion-doped chip integrated microcavity, a multi-frequency distributed feedback cavity and the like; the specific parameters of the multi-frequency laser such as wavelength range, frequency number, frequency interval and output power are not limited.

In some embodiments, the modulation generation frequency sideband modulates the amplitude or phase of the multi-frequency laser by using a high-speed modulator, generates a series of frequency sidebands at equal intervals near an input frequency component, the frequency interval is consistent with a modulation repetition frequency, the number of output frequencies exceeds the number of input frequencies, and a comb-shaped distribution is preliminarily formed in a frequency domain; modulation waveforms include but are not limited to sine waves, square waves and sawtooth waves, and modulation parameters can be flexibly adjusted to change the frequency domain distribution of the output initial frequency comb; the sidebands of the respective input frequency components may overlap each other; the specific parameters such as modulation repetition frequency, modulator type, etc. are not limited.

In some embodiments, the spectrum is spread, an initial optical frequency comb is introduced into a highly nonlinear medium, new frequency components are further generated through self-phase modulation, and the output optical frequency comb for spectrum spreading is realized, and energy is transferred among the frequency components through nonlinear effects such as self-phase modulation; the high nonlinear medium has low transmission loss, high nonlinear coefficient and near-zero anomalous dispersion characteristics, and comprises but is not limited to a high nonlinear optical fiber or a photonic crystal optical fiber, a chip integrated semiconductor waveguide, a periodically polarized lithium niobate crystal and the like, the type of nonlinear effect generated in the high nonlinear medium is not limited, various nonlinear effect enhancement modes (micro-ring cavity resonance, a photonic crystal slow optical waveguide, a graphene coating and the like) are not limited, and the frequency interval, the spectral flatness, the effective bandwidth, the output power, specific application scenes and the like of an output optical frequency comb are not limited.

Compared with the prior art, the invention has the following advantages:

firstly, the invention provides a brand-new optical frequency comb generation method, which effectively combines three optical frequency comb generation methods of multi-frequency laser oscillation, frequency sideband generation by modulation and nonlinear effect, and can realize the output of the optical frequency comb with high average power, more frequency quantity and large bandwidth range;

and secondly, the spectrum platform optimization control of the output optical frequency comb can be realized by adjusting parameters such as the grating transmission spectrum of the common gain medium multi-frequency laser, the modulation coefficient of the modulator, the dispersion of the nonlinear medium and the like, and the system performance of the subsequent dense wavelength division multiplexing is improved.

In addition, the system structure is highly compatible with the standard preparation process of the chip integrated optical path, has higher engineering practicability, and can provide integrated equipment support for applications such as optical fiber communication, microwave photon signal processing, optical time measurement, laser radar, optical ranging and the like.

For convenience of description, the above devices are described as being divided into various units by function, and are described separately. Of course, the functionality of the various elements may be implemented in the same one or more pieces of software and/or hardware in the practice of the present application.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

The application may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The application may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

In a typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.

The memory may include forms of volatile memory in a computer readable medium, Random Access Memory (RAM) and/or non-volatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). Memory is an example of a computer-readable medium.

Computer-readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), Digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer readable medium does not include a transitory computer readable medium such as a modulated data signal and a carrier wave.

It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

All the embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.

The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement or the like made within the spirit and principle of the present application shall be included in the scope of the claims of the present application.

Claims (10)

1. A method for generating optical frequency comb based on multi-frequency laser modulation and non-linear frequency spectrum expansion includes generating multi-frequency laser output by a common gain medium multi-frequency laser, modulating multi-frequency laser by a high-speed modulator, generating frequency equal interval sidebands to obtain initial optical frequency comb, realizing broadband optical frequency comb output by self-phase modulation spread spectrum in high non-linear medium, modulating amplitude or phase of multi-frequency laser by the high-speed modulator, generating a series of frequency sidebands at equal intervals near input frequency component, enabling frequency interval to be consistent with modulation repetition frequency, enabling output frequency number to exceed input frequency number and preliminarily forming comb distribution in frequency domain, introducing the initial optical frequency comb into high non-linear medium, further generating new frequency component by self-phase modulation, The energy of the output optical frequency comb for realizing spectrum spreading is transferred among frequency components through nonlinear effects such as self-phase modulation.

2. The method for generating an optical frequency comb based on multi-frequency laser modulation and nonlinear spectrum spreading as claimed in claim 1, wherein the multi-frequency laser is output by a common gain medium multi-frequency laser, the laser is composed of a pump light source, a Wavelength Division Multiplexer (WDM), an erbium-doped fiber (EDF), a high reflection fiber grating (HR-FBG), and a low reflection fiber grating (LR-FBG), and three sets of fiber gratings with different wavelengths form three sets of resonant cavities, and generate three-channel laser outputs with wavelengths of 1549.6nm, 1550nm, and 1550.4nm respectively after sharing the pump light excited EDF gain medium with 976nm, that is, three-frequency laser outputs with a frequency interval of 50 GHz.

3. The method as claimed in claim 1, wherein the phase of the three-frequency laser is modulated by a 10GHz sine wave to generate frequency sidebands having a frequency interval of 10GHz and a symmetric distribution with an intensity satisfying a bessel function with a center frequency of the laser as an axis, and the normalized intensities of two adjacent lasers and their middle frequency sidebands in the frequency domain are approximately 0.77, 0.44, 0.13, 0.44, and 0.77 when the phase modulation factor is 1, and the initial frequency comb output with approximately the same frequency components can be realized by changing the phase modulation factor.

4. The method as claimed in claim 1, wherein an initial frequency comb is coupled into a highly nonlinear waveguide to generate a spectral broadening under the combined action of third-order nonlinear effects such as self-phase modulation and waveguide dispersion, thereby obtaining a broadband output optical frequency comb.

5. The method for optical frequency comb generation based on multi-frequency laser modulation and nonlinear spectral spreading as claimed in claim 1 or 2, wherein the pumping means includes but is not limited to electrical pumping, optical pumping, and hybrid pumping.

6. The method for optical frequency comb generation based on multifrequency laser modulation and nonlinear spectral spreading according to claim 1 or 2, wherein the gain medium can be a crystal or a doped fiber; the multi-frequency resonant cavity needs to provide positive feedback for a plurality of equally spaced frequencies.

7. The method as claimed in claim 1 or 3, wherein the modulation waveform includes but is not limited to sine wave, square wave, and sawtooth wave, and the modulation parameters can be flexibly adjusted to change the output initial frequency comb frequency domain distribution; the sidebands of the respective input frequency components may overlap each other.

8. The method for optical frequency comb generation based on multi-frequency laser modulation and nonlinear spectrum spreading as claimed in claim 1 or 4, wherein the highly nonlinear medium has to have low transmission loss, high nonlinear coefficient and near-zero anomalous dispersion characteristics, including but not limited to highly nonlinear fiber or photonic crystal fiber, chip integrated semiconductor waveguide, and periodically poled lithium niobate crystal.

9. A system for implementing the method for generating an optical frequency comb based on multi-frequency laser modulation and nonlinear spectrum spreading as claimed in claims 1-8, comprising a common gain medium multi-frequency laser, which is composed of a pump source, a gain medium and a multi-frequency resonant cavity, and further comprising:

the multi-frequency laser output module is used for generating multi-frequency laser output through the common gain medium multi-frequency laser;

the multi-frequency laser modulation module is used for modulating multi-frequency laser by using a high-speed modulator, generating frequency equal-interval sidebands and obtaining an initial optical frequency comb;

the nonlinear spectrum spreading module is used for expanding the narrow-band optical frequency comb into a wide-band optical frequency comb by utilizing self-phase modulation spread spectrum in a high nonlinear medium;

the pumping means includes but is not limited to electrical pumping, optical pumping, hybrid pumping;

the gain medium may be a crystal or a doped fiber;

the multi-frequency resonant cavity needs to provide positive feedback for a plurality of equally spaced frequencies, and includes, but is not limited to, a multi-oscillation frequency standing wave cavity, an annular cavity containing a multi-channel filter, a fiber Fabry-Perot cavity formed by a plurality of sets of fiber gratings, a chip integrated microcavity doped with rare earth ions, and a multi-frequency distributed feedback cavity.

10. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the method of any one of claims 1 to 8.

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