CN116846479A - Dual-optical-frequency comb generation system and method based on communication algorithm - Google Patents
Dual-optical-frequency comb generation system and method based on communication algorithm Download PDFInfo
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Abstract
The embodiment of the application provides a double-optical-frequency comb generating system and method based on a communication algorithm, and relates to the technical field of optical communication. The communication algorithm module is used for generating a preset time domain signal through a pseudo-random binary sequence and sending the preset time domain signal to the double optical frequency comb generating module, wherein the preset time domain signal is two groups of comb teeth with frequency difference on a frequency domain; the double-optical-frequency comb generating module comprises a laser, a signal generator, an electro-optical modulator and a microcavity, wherein the input end of the electro-optical modulator is respectively connected with the laser and the signal generator, the output end of the electro-optical modulator is connected with the microcavity, the laser generates continuous laser signals with preset wavelengths, the signal generator receives preset time domain signals and generates double-frequency comb time domain digital electric signals based on the preset time domain signals, and the electro-optical modulator modulates the continuous laser signals into time domain pseudo-random sequence optical signals corresponding to the double-optical-frequency comb based on the double-frequency comb time domain digital electric signals and inputs the time domain pseudo-random sequence optical signals into the microcavity.
Description
Technical Field
The application relates to the technical field of optical communication, in particular to a double-optical-frequency comb generating system and method based on a communication algorithm.
Background
Currently, optical communication and spectroscopic applications rely heavily on the measurement of various types of optical spectra, such as absorption/transmission spectra, fluorescence spectra, and raman spectra, but resolution and speed tend to be a bottleneck. Among the various available spectrometry methods, spectroscopic analysis is most popular. The double optical frequency comb system can map a broadband comb line to the radio frequency domain by using two optical frequency combs with slightly offset repetition frequencies, a so-called multi-heterodyne or double comb process which is widely adopted due to its advantages in terms of dynamic range, refresh rate and spectral resolution. The dual optical frequency comb combines many advantages of traditional broadband spectroscopy and tunable laser spectroscopy onto a platform, and as with traditional fourier transform infrared spectroscopy, the receiving demodulation end can detect the spectrum by using only one photodetector.
Dual optical frequency combs offer the possibility to surpass traditional fourier transform spectroscopy because of the lack of moving parts or high resolution virtual image phased arrays. Based on the increasing data acquisition speed, sensitivity, tuning range and accuracy requirements, various double optical frequency comb methods from terahertz to ultraviolet band have been explored and studied. These methods are implemented by various optical frequency comb sources, including mode-locked lasers, microresonator combs, quantum cascade lasers, and electro-optic digital frequency combs. For most of the generation ends of the double optical frequency comb, the additional phase locking and control electronic devices for maintaining mutual coherence are huge in size and high in cost, the system structure design is complex, the wide application of the double optical frequency comb system is greatly hindered, and the system is an important problem to be solved urgently at present. Because the electro-optical digital double-comb interferometers are mutually phase coherent, long-time measurement, a complex locking system and a computer algorithm are not needed, the complexity of the interferometer is greatly reduced, and the electro-optical digital double-comb interferometer is widely applied to the aspects of optical coherence tomography, spectral analysis and the like. In addition, since the digital signals generated by the codes can flexibly design the intervals of the comb teeth, and the cavity length is not fixed like that of a mode-locked laser and a micro-resonator comb, the digital optical frequency comb has the advantage of flexibility compared with the mode-locked laser, the quantum cascade laser and the micro-resonator comb. However, for the traditional electro-optic digital optical frequency comb, the system is simplified, but the system is realized by two paths, a plurality of splitters, electro-optic modulators, acousto-optic modulators, balance detectors and the like are needed, and the complexity of the system is low.
In general, the existing dual optical frequency comb generating systems, whether they be mode-locked lasers, microresonator combs, quantum cascade lasers or traditional electro-optic digital frequency combs, are complex and are not conducive to practical application requirements.
Disclosure of Invention
The embodiment of the application aims to provide a double-optical-frequency comb generating system and a method based on a communication algorithm, which can realize the technical effects of simplifying the generating system of the double-optical-frequency comb and improving the practicability.
In a first aspect, an embodiment of the present application provides a dual optical frequency comb generating system based on a communication algorithm, including a communication algorithm module and a dual optical frequency comb generating module;
the communication algorithm module is used for generating a preset time domain signal through a pseudo-random binary sequence and sending the preset time domain signal to the double-optical-frequency comb generating module, wherein the preset time domain signal is two groups of comb teeth with frequency difference on a frequency domain;
the double-optical-frequency comb generating module comprises a laser, a signal generator, an electro-optical modulator and a microcavity, wherein the input end of the electro-optical modulator is respectively connected with the laser and the signal generator, the output end of the electro-optical modulator is connected with the microcavity, the laser generates continuous laser signals with preset wavelengths, the signal generator receives the preset time domain signals and generates double-frequency comb time domain digital electric signals based on the preset time domain signals, and the electro-optical modulator modulates the continuous laser signals into time domain pseudo-random sequence optical signals corresponding to the double-optical-frequency comb based on the double-frequency comb time domain digital electric signals and inputs the time domain pseudo-random sequence optical signals into the microcavity.
In the implementation process, the communication algorithm-based double-optical-frequency comb generation system generates a preset time domain signal through a communication algorithm module, so that two groups of comb teeth with a certain frequency difference are designed on a frequency domain through the design of the communication algorithm on the double-optical-frequency comb, and a group of integrated double-comb time domain signals (preset time domain signals) can be obtained through fast inverse Fourier transformation; leading a preset time domain signal into a signal generator, and modulating a continuous laser signal passing through an electro-optical modulator by the signal generator to generate a double optical frequency comb; after the double optical frequency comb passes through the microcavity, the receiving end can beat frequency through the photoelectric detector, so that the down-conversion of the double optical frequency comb and the process of reducing the detection bandwidth are realized; the double-optical-frequency comb generating system based on the communication algorithm is simple in structure, high in flexibility and strong in stability, and can achieve the technical effects of simplifying the double-optical-frequency comb generating system and improving practicality.
Further, the dual-optical-frequency comb generating system further comprises a photoelectric detector, and after the time-domain pseudo-random sequence optical signals are resonated through the microcavity, the time-domain pseudo-random sequence optical signals after the resonance are received and detected by the photoelectric detector.
In the implementation process, after the time domain pseudo random sequence optical signal resonates through the microcavity, frequency spectrum depression caused by specific absorption exists on the frequency domain of the comb teeth; therefore, after beat frequency detection by the photoelectric detector, the spectrum recess can be demodulated in a narrow bandwidth, namely, spectrum information in an original high bandwidth can be restored at a low sampling rate.
Further, the resonant condition of the microcavity is:
2πnR=mλ；
wherein n is the effective refractive index of the micro-ring in the micro-cavity, R is the radius of the micro-ring, m is the resonant order m=1, 2,3 …, λ is the resonant wavelength, and pi is the circumferential rate.
In the implementation process, the light meeting the resonance condition resonates in the microcavity, and the light not meeting the resonance condition is directly output from the original waveguide, so that the existence of a corresponding resonance peak at a specific wavelength can be seen from the transmission spectrum of the sweep frequency, and at the moment, the comb teeth can have frequency spectrum depression caused by specific absorption on the frequency domain.
Further, the communication algorithm module comprises a PRBS code time domain unit, a PRBS code frequency domain unit, a frequency domain integration unit and a double-comb time domain unit, wherein the PRBS code time domain unit, the PRBS code frequency domain unit, the frequency domain integration unit and the double-comb time domain unit are sequentially connected.
Further, the PRBS code time domain unit generates two sets of PRBS code sequences, and the two sets of PRBS code sequences are inconsistent in length.
Further, the PRBS code frequency domain unit acquires two groups of PRBS code sequences generated by the PRBS code time domain unit, and generates two groups of frequency comb teeth with the same center frequency and different repetition frequencies based on the two groups of PRBS code sequences through Fourier transformation.
Further, two groups of frequency comb teeth with the same center frequency and different repetition frequencies are overlapped and integrated into composite frequency comb teeth in the frequency domain integration unit, and the composite frequency comb teeth are subjected to inverse fast fourier transformation in the double-comb time domain unit to form the preset time domain signal.
In a second aspect, an embodiment of the present application further provides a dual optical frequency comb generating method based on a communication algorithm, which is applied to the dual optical frequency comb generating system based on the communication algorithm in any one of the first aspect, where the method includes:
generating a preset time domain signal based on a communication algorithm module;
the preset time domain signal generates a double-frequency comb time domain digital electric signal in the signal generator;
generating a continuous laser signal based on the laser;
the continuous laser signal is modulated in an electro-optical modulator through a double-frequency comb time domain digital electric signal to obtain a time domain pseudo-random sequence optical signal corresponding to the double-optical frequency comb;
the time domain pseudo random sequence optical signal resonates in the microcavity, and the resonated time domain pseudo random sequence optical signal is received and detected by the photoelectric detector.
Further, the step of generating a preset time domain signal based on the communication algorithm module includes:
generating two sets of PRBS code sequences based on PRBS code time domain units;
the two groups of PRBS code sequences generate two groups of frequency comb teeth with the same center frequency and different repetition frequencies through Fourier transformation in a PRBS code frequency domain unit;
the two groups of frequency comb teeth are overlapped and integrated into coincident frequency comb teeth in a frequency domain integration unit, wherein zero frequency comb teeth of the two groups of frequency comb teeth are coincident;
and the coincident frequency comb teeth perform inverse fast Fourier transform on the double-comb time domain unit to obtain the preset time domain signal.
Further, the time domain pseudo random sequence optical signal resonates in the microcavity, and the time domain pseudo random sequence optical signal after resonance is received and detected by the photoelectric detector, which includes the steps of:
the optical signals meeting the resonance condition of the microcavity in the time-domain pseudo-random sequence optical signals resonate, the optical signals which do not meet the resonance condition of the microcavity in the time-domain pseudo-random sequence optical signals are output from the original waveguide, and the time-domain pseudo-random sequence optical signals have corresponding resonance peaks at preset wavelengths;
and receiving and detecting the frequency spectrum concave caused by absorption of the time domain pseudorandom sequence optical signal after resonance at a preset wavelength on a frequency domain by a photoelectric detector, and demodulating the frequency spectrum concave.
Additional features and advantages of the disclosure will be set forth in the description which follows, or in part will be obvious from the description, or may be learned by practice of the disclosure.
In order to make the above objects, features and advantages of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.
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In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and should not be considered as limiting the scope, and other related drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a dual optical frequency comb generating system based on a communication algorithm according to an embodiment of the present application;
fig. 2 is a schematic flow chart of a dual optical frequency comb generating method based on a communication algorithm according to an embodiment of the present application;
fig. 3 is a schematic flow chart of another dual optical frequency comb generating method based on a communication algorithm according to an embodiment of the present application;
FIG. 4 is a schematic diagram of a digital frequency comb according to an embodiment of the present application;
FIG. 5 is a schematic diagram of a simulated beat frequency effect provided by an embodiment of the present application;
fig. 6 is a schematic diagram of a frequency comb demodulation principle according to an embodiment of the present application;
fig. 7 is a schematic diagram of a microcavity resonance measurement result of a dual-optical frequency comb according to an embodiment of the present application.
Icon: a communication algorithm module 100; a PRBS code time domain unit 110; a PRBS code frequency domain unit 120; a frequency domain integration unit 130; a double comb time domain unit 140; a dual optical frequency comb generation module 200; a laser 210; a signal generator 220; an electro-optic modulator 230; microcavity 240; a photodetector 250.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present application.
In the present application, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate an azimuth or a positional relationship based on that shown in the drawings. These terms are only used to better describe the present application and its embodiments and are not intended to limit the scope of the indicated devices, elements or components to the particular orientations or to configure and operate in the particular orientations.
Also, some of the terms described above may be used to indicate other meanings in addition to orientation or positional relationships, for example, the term "upper" may also be used to indicate some sort of attachment or connection in some cases. The specific meaning of these terms in the present application will be understood by those of ordinary skill in the art according to the specific circumstances.
Furthermore, the terms "mounted," "configured," "provided," "connected," and "connected" are to be construed broadly. For example, it may be a fixed connection, a removable connection, or a unitary construction; may be a mechanical connection, or a point connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements, or components. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
Furthermore, the terms "first," "second," and the like, are used primarily to distinguish between different devices, elements, or components (the particular species and configurations may be the same or different), and are not used to indicate or imply the relative importance and number of devices, elements, or components indicated. Unless otherwise indicated, the meaning of "a plurality" is two or more.
The embodiment of the application provides a system and a method for generating a double optical frequency comb based on a communication algorithm, which can be applied to the generation process of the double optical frequency comb; the double optical frequency comb generating system based on the communication algorithm generates a preset time domain signal through the communication algorithm module, so that two groups of comb teeth with a certain frequency difference are designed on a frequency domain through the design of the double optical frequency comb by the communication algorithm, and a group of integrated double comb time domain signals (preset time domain signals) can be obtained through fast Fourier transformation; leading a preset time domain signal into a signal generator, and modulating a continuous laser signal passing through an electro-optical modulator by the signal generator to generate a double optical frequency comb; after the double optical frequency comb passes through the microcavity, the receiving end can beat frequency through the photoelectric detector, so that the down-conversion of the double optical frequency comb and the process of reducing the detection bandwidth are realized; the double-optical-frequency comb generating system based on the communication algorithm is simple in structure, high in flexibility and strong in stability, and can achieve the technical effects of simplifying the double-optical-frequency comb generating system and improving practicality.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a dual optical frequency comb generating system based on a communication algorithm according to an embodiment of the present application, where the dual optical frequency comb generating system based on the communication algorithm includes a communication algorithm module 100 and a dual optical frequency comb generating module 200;
illustratively, the communication algorithm module 100 is configured to generate a preset time domain signal through a pseudo-random binary sequence, and send the preset time domain signal to the dual optical frequency comb generating module, where the preset time domain signal is two groups of comb teeth with frequency differences in a frequency domain.
Illustratively, a random bit data stream may be generated by a Pseudo-random binary sequence (Pseudo-Random Binary Sequence, PRBS), two sets of PRBS code sequences are generated based on the Pseudo-random binary sequence, the lengths of the two sets of PRBS code sequences are not uniform to achieve a slight misalignment in the frequency domain; thus, a preset time domain signal is generated based on the two groups of PRBS codes, and the preset time domain signal is two groups of comb teeth with frequency difference on the frequency domain.
Illustratively, the dual-optical-frequency comb generating module 200 includes a laser 210, a signal generator 220, an electro-optical modulator 230 and a microcavity 240, wherein an input end of the electro-optical modulator 230 is respectively connected to the laser 210 and the signal generator 220, an output end of the electro-optical modulator 230 is connected to the microcavity 240, the laser 210 generates a continuous laser signal with a preset wavelength, the signal generator 220 receives a preset time-domain signal and generates a dual-frequency comb time-domain digital electric signal based on the preset time-domain signal, and the electro-optical modulator 230 modulates the continuous laser signal into a time-domain pseudo-random sequence optical signal corresponding to the dual-optical-frequency comb based on the dual-frequency comb time-domain digital electric signal and inputs the time-domain pseudo-random sequence optical signal to the microcavity 240.
Illustratively, the electro-optic modulator 230 is controlled by a dual-frequency comb time domain digital electrical signal generated by a signal generator driven by a code (preset time domain signal) to modulate a single-wavelength, power-stable continuous laser signal into a time domain pseudo-random sequence optical signal corresponding to a dual optical frequency comb, thereby implementing conversion from an electrical frequency comb to an optical frequency comb.
Illustratively, the dual optical frequency comb generating system further includes a photodetector 250, and after the time domain pseudo random sequence optical signal resonates through the microcavity 240, the resonating time domain pseudo random sequence optical signal is received and detected by the photodetector 250.
Illustratively, after the time domain pseudo random sequence optical signal resonates through the microcavity 240, the comb teeth have spectral notches in the frequency domain caused by specific absorption; thus, after beat detection by the photodetector 250, the spectral notch can be demodulated in a narrow bandwidth, i.e., spectral information in the original high bandwidth can be highly restored at a low sampling rate.
Illustratively, the resonant condition of microcavity 240 is:
2πnR=mλ；
wherein n is the effective refractive index of the micro-ring in the micro-cavity, R is the radius of the micro-ring, m is the resonant order m=1, 2,3 …, λ is the resonant wavelength, and pi is the circumferential rate.
Illustratively, light meeting the resonance condition will resonate in the microcavity 240, and light not meeting the resonance condition will be directly output from the original waveguide, so that from the transmission spectrum of the sweep, the existence of a corresponding resonance peak at a specific wavelength can be seen, and at this time, the comb teeth will have a spectral notch caused by specific absorption in the frequency domain.
Illustratively, the communication algorithm module 100 includes a PRBS code time domain unit 110, a PRBS code frequency domain unit 120, a frequency domain integration unit 130, and a double comb time domain unit 140, where the PRBS code time domain unit 110, the PRBS code frequency domain unit 120, the frequency domain integration unit 130, and the double comb time domain unit 140 are sequentially connected.
Illustratively, the PRBS code time domain unit 110 generates two sets of PRBS code sequences, and the two sets of PRBS code sequences are inconsistent in length.
Illustratively, the PRBS code frequency domain unit 120 acquires two sets of PRBS code sequences generated by the PRBS code time domain unit 110, and generates two sets of frequency comb teeth having the same center frequency and different repetition frequencies based on the two sets of PRBS code sequences by fourier transform.
For example, two sets of frequency comb teeth with the same center frequency and different repetition frequencies are overlapped and integrated into a composite frequency comb tooth in the frequency domain integrating unit 130, and the composite frequency comb tooth is inverse fast fourier transformed into a preset time domain signal in the double-comb time domain unit 140.
Referring to fig. 2, fig. 2 is a flow chart of a dual optical frequency comb generating method based on a communication algorithm, which is provided in an embodiment of the present application and is applied to the dual optical frequency comb generating system based on the communication algorithm shown in fig. 1, and the dual optical frequency comb generating method based on the communication algorithm includes the following steps:
s100: generating a preset time domain signal based on a communication algorithm module;
s200: generating a double-frequency comb time domain digital electric signal in a signal generator by a preset time domain signal;
s300: generating a continuous laser signal based on the laser;
s400: modulating the continuous laser signal in an electro-optical modulator through a double-frequency comb time domain digital electric signal to obtain a time domain pseudo-random sequence optical signal corresponding to the double-optical frequency comb;
s500: the time domain pseudo random sequence optical signal resonates in the microcavity, and the resonated time domain pseudo random sequence optical signal is received and detected by the photoelectric detector.
Referring to fig. 3, fig. 3 is a flow chart of another dual optical frequency comb generating method based on a communication algorithm according to an embodiment of the present application.
Illustratively, S100: the step of generating a preset time domain signal based on the communication algorithm module comprises the following steps:
s110: generating two sets of PRBS code sequences based on PRBS code time domain units;
s120: generating two groups of frequency comb teeth with the same center frequency and different repetition frequencies by Fourier transformation of the two groups of PRBS code sequences in a PRBS code frequency domain unit;
s130: the two groups of frequency comb teeth are overlapped and integrated into coincident frequency comb teeth in the frequency domain integrating unit, wherein zero frequency comb teeth of the two groups of frequency comb teeth are coincident;
s140: the coincident frequency comb teeth are subjected to inverse fast fourier transform in a double-comb time domain unit to form a preset time domain signal.
Illustratively, S500: the time domain pseudo random sequence optical signal resonates in the microcavity, and the resonant time domain pseudo random sequence optical signal is received and detected by the photoelectric detector, and the method comprises the following steps:
the optical signals meeting the resonance condition of the microcavity in the time-domain pseudo-random sequence optical signals resonate, the optical signals which do not meet the resonance condition of the microcavity in the time-domain pseudo-random sequence optical signals are output from the original waveguide, and the time-domain pseudo-random sequence optical signals have corresponding resonance peaks at preset wavelengths;
the frequency spectrum depression caused by absorption of the time domain pseudorandom sequence optical signal after resonance exists at a preset wavelength on a frequency domain, and the frequency spectrum depression is received and detected by a photoelectric detector and demodulated.
The embodiment of the application develops a double optical frequency comb system with simple system structure, high flexibility and strong stability based on the method of communication algorithm free coding by an example: the method comprises the steps of performing simulation design on a generated code of a double-optical-comb system through a computer end (a communication algorithm module), integrating optical frequency comb frequency domains with slightly offset two repetition frequencies at the code end, and obtaining a group of double-comb time domain signals through fast Fourier transform; the time domain digital signal generated by the code is input into a signal generator, the signal generator sends a signal to carry out intensity modulation on single-frequency light, and the electric signal frequency domain comb teeth generated by the signal generator are converted into optical signal frequency domain comb teeth, so that the generation of double optical frequency combs is realized; the receiving end carries out beat frequency through the photoelectric detector, and the process of bandwidth compression of the double optical frequency comb detecting end is realized.
By way of example, referring to fig. 1 to 3, the dual optical frequency comb generating system based on the communication algorithm provided in the embodiment of the present application is mainly divided into two parts:
firstly, the communication algorithm module 100 generates a flat time domain signal on a frequency domain mainly through a Pseudo Random Binary Sequence (PRBS) to realize the generation of a digital electric double-frequency comb time domain signal;
and the second is a dual-optical-frequency comb generating module 200, which mainly realizes simple, flexible and convenient digital dual-optical-frequency comb generating and testing functions through a set of simple systems of a laser 210, a signal generator 220, an electro-optical modulator 230 and a photoelectric detector 250.
Illustratively, a PRBS code may produce a random bit data stream, the conventional format of the PRBS code being PRBSn, n representing the length of the register, the corresponding output length being expressed as:
PRBS n=2 n -1；
if PRBS8 indicates that the register corresponding to the PRBS code is 8 bits, the data that can be generated in one cycle is 2 8 1, namely 255 bits of data, the currently commonly used PRBS codes are PRBS7, PRBS9, PRBS11, PRBS15, PRBS32, etc., and the present application is not limited thereto;
in some implementation scenarios, according to design requirements, first, two sets of PRBS code sequences are generated by using PRBS codes, where the lengths of the two sets of PRBS codes are inconsistent, so as to achieve slight misalignment in the frequency domain, and then the two sets of PRBS code sequences are transformed into the frequency domain by fourier transform and are evenly distributed in a fixed range bandwidth; thus, two sets of center frequencies are obtainedf 0 Two groups of frequency comb teeth with slightly different repetition frequencies, wherein the comb tooth frequencies of the frequency comb are respectivelyf 1,n Andf 2,n the interval between two groups of comb teeth is respectivelyΔf 1 And (3) withΔf 2 The frequency difference between them can be noted as:
Δf = Δf 2 –Δf 1 ；
the zero frequency comb teeth of the two groups of frequency combs are overlapped, then the sequence number comb teeth at the two sides of the frequency comb are different in frequency domain,Δf、2×Δf、3×Δf、···、n×ΔfThe method comprises the steps of carrying out a first treatment on the surface of the The two groups of frequency comb teeth are overlapped on a frequency spectrum after being unified on codes, and then the frequency comb teeth are subjected to inverse fast Fourier transform to be converted into the overlapping of two groups of PRBS codes on time domains, so that the burden and the complexity of an experimental system are reduced, and the experimental system is greatly improvedStability of the system;
alternatively, as an example, the comb teeth employed in the algorithm code simulation areΔf 1 =65.9MHz、Δf 1 = 63.9MHz，Frequency differenceΔf = Δf 2 –Δf 1 =2MHzTotal bandwidth2GHzSingle side band1GHzThe double-comb superposition effect is shown in fig. 4, and fig. 4 is a schematic diagram of a digital frequency comb provided by the embodiment of the application; the analog photoelectric detector effect is used for performing beat frequency demodulation on the double comb teeth, and the comb teeth with new frequency spectrum are provided with the following teethΔf，The GHz bandwidth is successfully compressed to the MHz level, and the effect that the double-frequency comb can directly overlap on the time domain can also realize the double-comb down-conversion bandwidth compression is proved, the result is shown in fig. 5, and fig. 5 is a schematic diagram of the simulation beat frequency effect provided by the embodiment of the application.
In some implementations, the comb teeth employed in the examples areΔf 1 =5MHz、Δf 1 =5.005MHz，Frequency differenceΔf = Δf 2 –Δf 1 =5KHzTotal bandwidth5GHzSingle side band2.5GHz. Therefore, the spectrum resolution of the system is about 5MHz, so that the requirements of most microcavities are met, the highest sampling rate is consistent with the frequency difference of 5KHz, and the requirement of high-speed sampling is met. It should be noted that the parameter indexes can be freely adjusted according to the requirements, so that the flexibility is high and the adaptability is strong;
in the double optical frequency comb generating module, a single-wavelength continuous laser emits light with the wavelength ofλ 0 =1550nmAnd the continuous laser signals of the laser light source enter an electro-optical intensity modulator for modulation. The electro-optical intensity modulator is controlled by a double-frequency comb time domain digital electric signal generated by a code driven signal generator, and continuous laser signals with stable single wavelength power are modulated into a time domain pseudo-random sequence corresponding to a double-optical frequency comb, so that the conversion from the electric frequency comb to the optical frequency comb is realized; then the micro-cavity is input into a micro-cavity system, and the resonance condition is met in the micro-ring resonant cavity due to the characteristics of the micro-cavityWill resonate within the ring, where n is the effective refraction of the micro-ringThe ratio, R is the radius of the micro-ring, m is the resonance order m=1, 2,3 …,/and->Is the resonant wavelength. Light which does not meet the resonance condition is directly output from the original waveguide, so that the existence of a corresponding resonance peak at a specific wavelength can be seen from the transmission spectrum of the sweep frequency, the single-sideband 2.5GHz frequency comb is down-converted to 2.5MHz, the result is shown in FIG. 6, and FIG. 6 is a schematic diagram of the demodulation principle of the frequency comb provided by the embodiment of the application;
therefore, after the double optical frequency comb passes through the microcavity, the frequency spectrum recess caused by specific absorption exists in the frequency domain of the comb teeth, after the frequency spectrum recess enters the photoelectric detection beat to be detected, the recess can be demodulated in the single side band 2.5MHz narrow bandwidth after down-conversion, and the frequency spectrum information in the original 2.5GHz bandwidth can be highly restored at a low sampling rate. At the same time, the center wavelength of the comb teeth is changedλ 0 The wavelength is moved to the short wave direction, so that the resonance peak in the corresponding frequency spectrum can be seen to move rightwards, and the fact that the concave is generated by micro-ring resonance is proved, as shown in fig. 7, fig. 7 is a schematic diagram of a micro-cavity resonance measurement result of the double-optical-frequency comb provided by the embodiment of the application, and the double-optical-frequency comb generation system can well perform high-precision, adjustable and high-speed detection.
In all embodiments of the present application, "large" and "small" are relative terms, "more" and "less" are relative terms, "upper" and "lower" are relative terms, and the description of such relative terms is not repeated herein.
It should be appreciated that reference throughout this specification to "in this embodiment," "in an embodiment of the present application," or "as an alternative" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the appearances of the phrases "in this embodiment," "in an embodiment of the application," or "as an alternative embodiment" in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Those skilled in the art will also appreciate that the embodiments described in the specification are alternative embodiments and that the acts and modules referred to are not necessarily required for the present application.
In various embodiments of the present application, it should be understood that the sequence numbers of the foregoing processes do not imply that the execution sequences of the processes should be determined by the functions and internal logic of the processes, and should not be construed as limiting the implementation of the embodiments of the present application.
The foregoing is merely illustrative of the present application, and the present application is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present application. Therefore, the protection scope of the application shall be subject to the protection scope of the claims.
Claims (10)
1. The double-optical-frequency comb generating system based on the communication algorithm is characterized by comprising a communication algorithm module and a double-optical-frequency comb generating module;
the communication algorithm module is used for generating a preset time domain signal through a pseudo-random binary sequence and sending the preset time domain signal to the double-optical-frequency comb generating module, wherein the preset time domain signal is two groups of comb teeth with frequency difference on a frequency domain;
the double-optical-frequency comb generating module comprises a laser, a signal generator, an electro-optical modulator and a microcavity, wherein the input end of the electro-optical modulator is respectively connected with the laser and the signal generator, the output end of the electro-optical modulator is connected with the microcavity, the laser generates continuous laser signals with preset wavelengths, the signal generator receives the preset time domain signals and generates double-frequency comb time domain digital electric signals based on the preset time domain signals, and the electro-optical modulator modulates the continuous laser signals into time domain pseudo-random sequence optical signals corresponding to the double-optical-frequency comb based on the double-frequency comb time domain digital electric signals and inputs the time domain pseudo-random sequence optical signals into the microcavity.
2. The communication algorithm-based dual optical frequency comb generation system of claim 1, further comprising a photodetector, wherein the time domain pseudo random sequence optical signal is received and detected by the photodetector after being resonated by the microcavity.
3. The communication algorithm-based dual optical frequency comb generation system of claim 1, wherein the microcavity has a resonance condition of:
2πnR=mλ；
wherein n is the effective refractive index of the micro-ring in the micro-cavity, R is the radius of the micro-ring, m is the resonant order m=1, 2,3 …, λ is the resonant wavelength, and pi is the circumferential rate.
4. The system of claim 1, wherein the communication algorithm module comprises a PRBS code time domain unit, a PRBS code frequency domain unit, a frequency domain integration unit, and a double comb time domain unit, and the PRBS code time domain unit, the PRBS code frequency domain unit, the frequency domain integration unit, and the double comb time domain unit are sequentially connected.
5. The communication algorithm-based dual optical frequency comb generation system of claim 4, wherein the PRBS code time domain unit generates two sets of PRBS code sequences, and wherein the two sets of PRBS code sequences are not identical in length.
6. The system according to claim 5, wherein the PRBS code frequency domain unit obtains two sets of PRBS code sequences generated by the PRBS code time domain unit, and generates two sets of frequency comb teeth having the same center frequency and different repetition frequencies based on the two sets of PRBS code sequences by fourier transform.
7. The communication algorithm-based double optical frequency comb generating system according to claim 6, wherein two groups of frequency comb teeth with the same center frequency and different repetition frequencies are overlapped and integrated into an overlapped frequency comb tooth in the frequency domain integrating unit, and the overlapped frequency comb tooth is subjected to inverse fast fourier transform in the double comb time domain unit to be the preset time domain signal.
8. A method for generating a double optical frequency comb based on a communication algorithm, which is applied to the double optical frequency comb generating system based on a communication algorithm as claimed in any one of claims 1 to 6, and comprises:
generating a preset time domain signal based on a communication algorithm module;
the preset time domain signal generates a double-frequency comb time domain digital electric signal in the signal generator;
generating a continuous laser signal based on the laser;
the continuous laser signal is modulated in an electro-optical modulator through a double-frequency comb time domain digital electric signal to obtain a time domain pseudo-random sequence optical signal corresponding to the double-optical frequency comb;
the time domain pseudo random sequence optical signal resonates in the microcavity, and the resonated time domain pseudo random sequence optical signal is received and detected by the photoelectric detector.
9. The method for generating a dual optical frequency comb based on a communication algorithm according to claim 8, wherein the step of generating a preset time domain signal based on the communication algorithm module comprises:
generating two sets of PRBS code sequences based on PRBS code time domain units;
the two groups of PRBS code sequences generate two groups of frequency comb teeth with the same center frequency and different repetition frequencies through Fourier transformation in a PRBS code frequency domain unit;
the two groups of frequency comb teeth are overlapped and integrated into coincident frequency comb teeth in a frequency domain integration unit, wherein zero frequency comb teeth of the two groups of frequency comb teeth are coincident;
and the coincident frequency comb teeth are subjected to inverse fast Fourier transform in a double-comb time domain unit to obtain the preset time domain signal.
10. The method for generating a dual optical frequency comb based on a communication algorithm according to claim 8, wherein the time domain pseudo random sequence optical signal resonates in the microcavity, and the time domain pseudo random sequence optical signal after the resonance is received and detected by a photodetector, comprising the steps of:
the optical signals meeting the resonance condition of the microcavity in the time-domain pseudo-random sequence optical signals resonate, the optical signals which do not meet the resonance condition of the microcavity in the time-domain pseudo-random sequence optical signals are output from the original waveguide, and the time-domain pseudo-random sequence optical signals have corresponding resonance peaks at preset wavelengths;
and receiving and detecting the frequency spectrum concave caused by absorption of the time domain pseudorandom sequence optical signal after resonance at a preset wavelength on a frequency domain by a photoelectric detector, and demodulating the frequency spectrum concave.
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