Optical communication wavelength meter based on lithium niobate microcavity comb-excited rubidium atom two-photon transition.

Abstract

This application discloses an optical communication wavelength meter based on lithium niobate microcavity optical comb-excited rubidium atom two-photon transitions, comprising a microcavity optical comb module, a repetition frequency phase-locked loop (PLL), an initial frequency PLL, a rubidium atom gas cell, and a frequency-stabilized light source. The microcavity optical comb module generates a fundamental frequency optical comb and a frequency-doubled optical comb to directly excite rubidium atom two-photon transitions. The frequency-stabilized light source achieves frequency stabilization through rubidium atom saturation absorption. The repetition frequency PLL adjusts the repetition frequency based on the error signal of the two-photon transition fluorescence intensity. The initial frequency PLL adjusts the initial frequency by feeding back the beat signal between the frequency-doubled optical comb and the frequency-stabilized light source. The two PLLs stabilize the microcavity optical comb to two sets of transition energy levels, achieving frequency locking between the repetition frequency and the initial frequency. The optical communication wavelength meter based on lithium niobate microcavity optical comb-excited rubidium atom two-photon transitions provided in this application avoids the cross-modulation effect in the joint adjustment mechanism of pump wavelength and pump power, reducing the size of the optical communication wavelength meter.

Description

Technical Field

[0001] This application relates to the field of optical communication wavelength meter technology, specifically to an optical communication wavelength meter based on the two-photon transition of rubidium atoms excited by a lithium niobate microcavity optical comb. Background Technology

[0002] Optical frequency standards are currently the most stable and accurate atomic frequency standards, and they have significant application prospects in precision measurement fields such as the measurement of fundamental physical constants and dark matter detection. Traditional optical clocks rely on hyperfine resonant cavities and cold atom systems, resulting in complex structures and large volumes. Furthermore, because the atomic transition spectral lines they utilize are located in the ultraviolet or visible bands, they are difficult to use as reference sources for optical communication. The optical frequency standard method, which uses an erbium-doped fiber comb to directly excite two-photon transitions of rubidium atoms, eliminates the need for hyperfine resonance in traditional optical clocks, simplifying the system structure. Simultaneously, the rubidium atom two-photon transition wavelength (778 nm) divided by two falls within the communication band, which is also the band covered by the erbium-doped fiber comb. Therefore, after the comb locks with the rubidium atom transition lines to form an atomic frequency standard, it can be used as a wavelength meter for optical communication.

[0003] Limited by the size and power consumption of erbium-doped fiber combs, the aforementioned optical communication wavelength meters that utilize fiber combs to excite two-photon transitions of rubidium atoms are difficult to further miniaturize and thus move towards practical application. In recent years, the emergence of microcavity combs based on the strong four-wave mixing effect in highly nonlinear microcavities has made it possible to reduce the size of the comb resonator to the millimeter or even micrometer scale. This can greatly reduce the size and power consumption of two-photon frequency standard systems, laying the foundation for realizing miniaturized and portable optical communication wavelength meters.

[0004] Currently, existing technologies have achieved optical atomic frequency standards for rubidium atom two-photon transitions based on microcavity optical combs. This method uses two microcavity optical combs, where the THz repetition rate comb is used to extract and lock f using the "f-2f" method. ceo A microcavity optical comb with a repetition rate of 22 GHz is used for frequency locking with the two-photon transition, and the frequency stability of the entire system is achieved by interlocking two optical combs. This achieves miniaturization of key components such as the optical comb without compromising stability.

[0005] In the aforementioned wavelength metering method based on microcavity optical combs, the fabrication process of the microcavities limits the direct generation of octave band optical combs within the cavity, while low-repetition-rate microcavities cannot achieve this. Consequently, this method necessitates the introduction of a second optical comb and four phase-locked loops to construct a complete optical frequency standard system. This results in an unusually large optical path and circuitry around the miniaturized resonant cavity, increasing system complexity and hindering overall system miniaturization.

[0006] The inability of microcavity optical combs with repetition rates of tens of GHz to lock onto f ceoThe problem was subsequently addressed by two improved solutions: one was to use highly nonlinear optical fibers outside the cavity to broaden the spectrum to octaves for self-reference locking. ceo Another method is to use two sets of transition spectral lines to simultaneously lock the two teeth of the optical comb, thereby simultaneously locking the initial frequency f. ceo and repetition frequency f rep Both of these schemes can construct optical communication optical standards using only a single microcavity optical comb and a dual phase-locked loop.

[0007] However, all three schemes described above use a combined feedback adjustment method of pump frequency and pump power to stabilize the frequency of the microcavity optical comb. rep and f ceo This approach suffers from a cross-modulation effect, meaning that adjusting the pump power may simultaneously cause a change in the pump wavelength.

[0008] Furthermore, all three schemes mentioned above lock the atomic energy level transition spectral lines by frequency doubling with a continuous-wave laser, and then lock the microcavity optical comb to the frequency-stabilized laser, indirectly achieving the locking of the optical comb to the atomic spectral lines. The introduction of an additional laser, coupled with the fact that the frequency doubling process still occurs outside the cavity, also increases the complexity of the entire wavelengthmeter system. Summary of the Invention

[0009] To address this issue, this application provides an optical communication wavelength meter based on the two-photon transition of rubidium atoms excited by a lithium niobate microcavity optical comb, thereby solving the problems of cross-modulation effect and large size of existing optical communication wavelength meters.

[0010] To achieve the above objectives, this application provides the following technical solution:

[0011] An optical communication wavelength meter based on lithium niobate microcavity optical comb-excited rubidium atom two-photon transitions includes a microcavity optical comb module, a repetition frequency phase-locked loop, an initial frequency phase-locked loop, a photomultiplier tube, a rubidium atom gas cell, and a frequency-stabilized light source;

[0012] The microcavity optical comb module includes a pump source, an erbium-doped fiber amplifier, a lithium niobate microring resonator, and electrodes. The lithium niobate microring resonator and the electrodes are integrally formed. The pump source is used to generate laser light as the initial source for pumping the microcavity optical comb. After being amplified by the erbium-doped fiber amplifier, the laser light is coupled into the lithium niobate microring resonator as pump light to generate a fundamental frequency optical comb and a frequency doubling optical comb. The electrodes are used to control the repetition frequency of the optical comb.

[0013] The frequency-stabilized light source is used to excite the saturated absorption resonant transition of rubidium atoms on the D1 line and stabilize the frequency on the D1 line, serving as the frequency reference for the initial frequency phase-locked loop.

[0014] The repetition frequency phase-locked loop adjusts the repetition frequency of the frequency doubling optical comb based on the error signal of the fluorescence intensity of the two-photon transition, so that a certain mode of the frequency doubling optical comb is aligned with the two-photon spectrum peak of the rubidium atom. The fluorescence intensity of the two-photon transition radiation of the atoms in the rubidium atom gas chamber is collected by the photomultiplier tube.

[0015] The initial frequency phase-locked loop is used to beat the m-th mode of the frequency-stabilized light source with the frequency-doubling optical comb, and the error is fed back to the pump light source through the initial frequency phase-locked loop.

[0016] The repetitive frequency phase-locked loop and the initial frequency phase-locked loop continuously feed the frequency difference between the comb tooth frequency and the atomic frequency standard back to the feedback element of the microcavity optical comb until the frequency deviation stabilizes, thereby achieving long-term locking between the comb teeth and the atomic energy level.

[0017] Preferably, the initial frequency phase-locked loop includes a phase detection module, which includes a first photodetector, a second photodetector, a frequency divider, and a mixer. The first photodetector is used to obtain the frequency difference beat frequency signal between the frequency-stabilized laser (calculated to the saturated absorption line of the rubidium atom D1 line) and the atomic frequency reference and the saturated absorption frequency of the rubidium atom D1 line in the m-th mode of the frequency-doubled optical comb, and inputs it into the mixer. The second photodetector is used to input the same-frequency signal to extract the repetition frequency signal of the frequency-doubled optical comb, and inputs the same-frequency repetition frequency signal into the mixer via the frequency divider. The mixer is used to calculate the error between the rubidium atom frequency reference with a stable beat frequency signal and the same-frequency repetition signal.

[0018] Preferably, the pump source is an external cavity semiconductor pumped laser.

[0019] Preferably, the frequency-stabilized light source is a semiconductor laser.

[0020] Preferably, the lithium niobate microring resonator is etched using a femtosecond laser ablation method.

[0021] Preferably, the electrode is made using an unetched chromium mask.

[0022] Preferably, the system also includes a dichroic beam splitter, which is used to separate the optical comb generated by the lithium niobate microring resonator into a fundamental frequency optical comb and a frequency doubling optical comb.

[0023] Compared with the prior art, this application has at least the following beneficial effects:

[0024] This application provides an optical communication wavelength meter based on the two-photon transition of rubidium atoms excited by a lithium niobate microcavity optical comb. Based on a lithium niobate microring resonator, by introducing an electro-dispersion repetition frequency modulation mechanism, the cross-modulation of pump power and wavelength in traditional microcavity optical comb frequency standard systems is avoided, and independent feedback control and locking of repetition frequency and initial frequency are achieved. Based on the second-order nonlinear effect in the lithium niobate microring resonator, a frequency-doubling optical comb is directly generated in the cavity and directly locked to the two-photon transition and saturation absorption spectral line of rubidium atoms. This significantly reduces the use of continuous light lasers and external self-reference optical paths and external frequency-doubling optical paths. While miniaturizing the core components, the size of peripheral components is effectively reduced, laying the foundation for the miniaturization and large-scale application of optical communication wavelength meters. Attached Figure Description

[0025] To more intuitively illustrate the prior art and this application, exemplary drawings are provided below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concept disclosed in this application and the exemplary drawings, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, size ratios, etc. of certain units (components).

[0026] Figure 1 A schematic diagram of the optical communication wavelength meter based on lithium niobate microcavity optical comb-excited two-photon transitions of rubidium atoms, provided in this application;

[0027] Figure 2 This is a schematic diagram of the microcavity optical comb module provided in this application.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. Pump light source; 2. Erbium-doped fiber amplifier; 3. Lithium niobate microring resonator; 4. Electrode; 5. Two-color beam splitter; 6. Optical communication frequency standard output; 7. Photomultiplier tube; 8. Rubidium atom gas cell; 9. Frequency-stabilized light source; 10. Second photodetector; 11. Frequency divider; 12. Mixer; 13. First photodetector. Detailed Implementation

[0030] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] In the description of this application: unless otherwise stated, "a plurality of" means two or more. The terms "first," "second," "third," etc., in this application are intended to distinguish the objects referred to and do not have any special meaning in terms of technical connotation (e.g., they should not be construed as an emphasis on importance or order). Expressions such as "comprising," "including," and "having" also mean "not limited to" (certain units, components, materials, steps, etc.).

[0032] The terms used in this application, such as "upper," "lower," "left," "right," and "middle," are generally used to indicate the general relative positional relationship for the purpose of intuitive understanding by referring to the accompanying drawings, and are not absolute limitations on the positional relationship in the actual product.

[0033] Please see Figure 1 This application provides an optical communication wavelength meter based on the two-photon transition of rubidium atoms excited by a lithium niobate microcavity optical comb. It derives a novel method for feedback-adjusted microcavity optical comb frequency, achieving f independently through two feedback units. rep and f ceo The frequency of the microcavity optical comb is stabilized long-term by employing rubidium atom two-photon transitions and saturable absorption, where the two-photon transitions are directly excited by the comb. The comb teeth can be represented as f... n =nf rep +f ceo When two sets of atomic frequency standards are used to lock the two comb teeth of the microcavity laser respectively, the repetition frequency f can be stabilized simultaneously. rep and initial frequency f ceo This achieves long-term stability of all teeth in the microcavity optical comb. This frequency stabilization mode, which utilizes two sets of transition spectral lines to simultaneously stabilize two comb teeth, overcomes the limitation of microcavity optical combs in the tens of GHz range being difficult to self-reference, and avoids the complex optical path introduced by external self-reference. Thus, the high stability of the atomic frequency standard is transferred to the communication band through the microcavity optical comb, realizing an optical communication wavelength meter. This wavelength meter includes a microcavity optical comb module, a rubidium atomic gas cell 8, a frequency-stabilized light source 9, a repetition frequency phase-locked loop, an initial frequency phase-locked loop, and a photomultiplier tube 7.

[0034] Specifically, the microcavity optical comb module includes a pump source 1, an erbium-doped fiber amplifier 2, a lithium niobate microring resonator 3, and an electrode 4. The lithium niobate microring resonator 3 and the electrode 4 are integrally formed. The pump source 1 adopts an external cavity semiconductor pump laser (containing a piezoelectric controller), the lithium niobate microring resonator 3 is etched by a femtosecond laser ablation method, and the electrode 4 is made of an unetched chromium mask.

[0035] It should be noted that chemical mechanical polishing technology is used to smooth the sidewalls of the lithium niobate microring resonator 3 after pattern transfer, thereby improving the quality factor Q of the microring resonator; the external cavity semiconductor pump laser (ECDL) has direct wavelength tuning capability.

[0036] Please see Figure 2The microcavity optical comb module is used to generate the fundamental frequency optical comb and the frequency doubling optical comb. Specifically: the continuous laser output from the external cavity semiconductor pump laser in the communication band is amplified by the erbium-doped fiber amplifier 2 and then used as the pump light for the lithium niobate microring resonator 3, which is coupled into the lithium niobate microring resonator 3. Since the third-order nonlinear effect—the Kerr effect—that generates the microcavity optical comb has a threshold, the pump light must reach the threshold to generate the optical comb in the lithium niobate microring resonator 3; therefore, the erbium-doped fiber amplifier 2 is indispensable. Because the electrode 4 on the lithium niobate microring resonator 3 is made of an unetched chromium mask, the lithium niobate microring resonator 3 and the electrode 4 are a single unit. Therefore, when the pump light enters the lithium niobate microring resonator 3, it undergoes four-wave mixing within the cavity to generate the fundamental frequency optical comb. The fundamental frequency optical comb then undergoes a second-order nonlinear interaction within the cavity to generate the frequency doubling optical comb. Both are simultaneously coupled and output to the outside of the lithium niobate microring resonator 3.

[0037] The microcavity optical comb module is constructed based on a lithium niobate microring resonator 3 with integrated electrode 4, achieving efficient coupling between the pump light and the microcavity and deterministically realizing Kerr soliton mode-locking within the microcavity. The second-order nonlinear frequency doubling effect of the lithium niobate microring resonator 3 is used to generate the second harmonic of the fundamental frequency soliton optical comb, realizing a frequency-doubled replica of the second harmonic of the Kerr soliton optical comb. By applying an electric field to change the effective optical path of the microring resonator, the repetition frequency f of the microcavity optical comb is achieved. rep The control is achieved by adjusting the pump center wavelength to realize the center frequency of the microcavity optical comb, i.e., the initial frequency f. ceo Regulation.

[0038] More specifically, the optical communication wavelength meter based on the two-photon transition of rubidium atoms excited by the lithium niobate microcavity optical comb provided in this application also includes a dichromatic beam splitter 5, which is used to spatially separate the fundamental frequency optical comb and the frequency doubling optical comb generated in the lithium niobate microring resonant cavity 3.

[0039] In this application, the repetitive frequency phase-locked loop (PLL) Figure 1 The phase-locked loop 1) uses the rubidium atom two-photon transition as the frequency reference and feeds back to the electrode 4 of the microcavity optical comb module for feedback adjustment of the repetition frequency. Specifically, the photomultiplier tube 7 is used to collect the fluorescence intensity of the rubidium atom two-photon transition radiation in the rubidium atom gas cell 8 and extract the error signal of the fluorescence intensity. The repetition frequency phase-locked loop adjusts the repetition frequency of the frequency doubling optical comb according to the error signal of the fluorescence intensity, so that the nth mode of the frequency doubling optical comb is aligned with the rubidium atom two-photon spectral peak.

[0040] More specifically, for two-photon transitions directly excited by an optical comb, the two-photon transition has the highest intensity if and only if a mode of the optical comb is exactly located at a frequency that strictly corresponds to the spectral peak. This application uses a photomultiplier tube 7 to collect the fluorescence intensity of the two-photon transition radiation, extracts the error signal of the fluorescence, and uses feedback adjustment of the repetition frequency of the optical comb to ensure that the nth mode of the frequency-doubled optical comb is precisely aligned with the two-photon spectral peak. The mode frequency is f. n =nf rep +2f ceo The frequency of the two-photon spectrum peak of rubidium atoms is f TPT Then f satisfies TPT =f n =nf rep +2f ceo .

[0041] In this application, the initial frequency phase-locked loop (PLL) Figure 1 The phase-locked loop 2) uses the rubidium atom saturated absorption spectrum as the frequency reference and feeds back to the piezoelectric controller of the pump light source 1 of the microcavity optical comb module, so as to realize the feedback adjustment of the initial frequency.

[0042] Specifically, the m-th mode of a frequency-doubled optical comb located at 795 nm is used for frequency stabilization of the saturated absorption of the D1 line of rubidium atoms. The frequency of this mode is f. m =mf rep +2f ceo The optical frequency comb cannot be directly stabilized through the saturated absorption spectral line; it requires indirect stabilization using a frequency-stabilizing light source 9. This light source 9 is pre-locked to the rubidium atom saturated absorption line D1, with a frequency of f. SA The frequency of the signal generated by the beat frequency of the two is f. b =f SA -f m Because f SA To establish a stable atomic frequency reference, f must be stabilized. m This means that f must first be stabilized. b Therefore, it is necessary to perform phase detection with a signal of the same frequency (the frequency-doubled optical comb generated by the microcavity optical comb module). The error signal is then fed back to the pump source 1 of the microcavity optical comb module through the initial frequency phase-locked loop to adjust the f of the optical comb. ceo (Initial frequency), at which point f is satisfied. SA =f m +f b =mf rep +2f ceo +f b .

[0043] It should be noted that the scheme in this application requires frequency stabilization of the frequency doubling optical comb, and the frequency of its k-th mode can be expressed as f. k =kf rep +2f ceo , where frep f is the repetition frequency of the fundamental frequency optical comb. ceo This represents the initial frequency of the fundamental frequency optical comb. The two-photon transition of rubidium atoms corresponds to the 778nm band of the frequency doubling comb, while a certain mode of the frequency doubling comb at 795nm is used for frequency stabilization of the rubidium atom D1 line saturation absorption.

[0044] Joint f TPT with f SA Two formulas, considering the f in a typical microcavity optical comb module rep Up to tens of GHz, while f rep >f b , if and only if f b f rep When dividing by d, i.e., f b =f rep / d, the repetition frequency f of the microcavity optical comb can be determined by the frequency difference between the two sets of atomic transition spectral lines. rep ,have:

[0045]

[0046] This shows that the repetition frequency of the microcavity optical comb is locked to the frequency difference between the two sets of rubidium atom spectral lines. At this point, f... ceo It was also locked onto a certain algebraic sum of two sets of transition frequencies. In this way, the optical frequency standard of rubidium atoms was transmitted to the communication band where the fundamental frequency optical comb is located. This optical comb can output a frequency standard through optical communication and be used to realize a wavelength meter.

[0047] It should be noted that the error signal generated by the repetition frequency phase detection is directly fed back to electrode 4 of the optical comb after passing through the servo circuit, thus achieving frequency locking; similarly, f ceo The signal is mixed and phase-detected by a phase-locked loop to obtain an error signal, which is then fed back to the piezoelectric actuator of pump light source 1 after passing through a servo circuit. By adjusting the wavelength of the pump light, f can be achieved. ceo The lock.

[0048] Among them, the optical comb used for two-photon excitation is a second-order nonlinear frequency doubling effect inside the microcavity that directly generates a second-harmonic optical comb, avoiding complex frequency doubling optical paths and continuous optical locking structures, and significantly reducing the system volume; the semiconductor laser used for rubidium atom saturated absorption frequency stabilization is a 795nm semiconductor laser, and the feedback signal is the beat frequency signal between the frequency doubling optical comb and the frequency-stabilized laser. This method also avoids external cavity frequency doubling.

[0049] The optical communication wavelength meter based on lithium niobate microcavity optical comb-induced rubidium atom two-photon transitions provided in this application overcomes the bottleneck of difficult frequency control of existing microcavity optical combs, while also solving the problem of difficult volume compression of the microcavity periphery. Specifically, this application, based on the ferroelectric material system of lithium niobate, introduces a microcavity optical comb repetition frequency control mechanism based on electro-induced refractive index changes, combined with the adjustment of the center wavelength of the microcavity optical comb based on the pump frequency, to achieve an optical comb repetition frequency f. rep and initial frequency f ceo Independent control is achieved. Simultaneously, the second-order nonlinearity of ferroelectric materials is used to directly generate a frequency-doubled optical comb within the lithium niobate microring resonator 3, directly exciting rubidium atoms to two-photon transitions and locking them to the transition spectral lines. This avoids the introduction of additional frequency-doubled optical paths and continuous optical locking structures, effectively reducing the volume of the peripheral parts. This lays the foundation for the realization of miniaturized optical communication wavelength meters, enabling their widespread application in wavelength calibration for optical communication.

[0050] In summary, the optical communication wavelength meter based on lithium niobate microcavity optical comb-excited rubidium atom two-photon transitions provided in this application has the following advantages:

[0051] (1) By adjusting the electric field to change the dispersion in the lithium niobate microring resonator, the repetition frequency can be finely adjusted, avoiding the cross-modulation effect in the joint adjustment mechanism of pump wavelength and pump power, and realizing the independent control and locking of the optical comb repetition frequency and initial frequency.

[0052] (2) By directly locking the frequency-doubling optical comb inside the lithium niobate microring resonator with the transition spectral lines of two sets of rubidium atoms, the introduction of a continuous laser is minimized without introducing an external self-reference or an external frequency-doubling optical path. This effectively reduces the size of the peripheral components while miniaturizing the core components, laying the foundation for the large-scale application of optical communication wavelength meters.

[0053] The technical features of the above embodiments can be combined in any way (as long as there is no contradiction in the combination of these technical features). For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; these embodiments not explicitly written should also be considered to be within the scope of this specification.

Claims

1. An optical communication wavelength meter based on two-photon transitions of rubidium atoms excited by a lithium niobate microcavity optical comb, characterized in that, It includes a microcavity optical comb module, a repetition frequency phase-locked loop, an initial frequency phase-locked loop, a photomultiplier tube, a rubidium atom gas cell, and a frequency-stabilized light source; The microcavity optical comb module includes a pump source, an erbium-doped fiber amplifier, a lithium niobate microring resonator, and electrodes. The lithium niobate microring resonator and the electrodes are integrally formed. The pump source is used to generate laser light as the initial source for pumping the microcavity optical comb. After being amplified by the erbium-doped fiber amplifier, the laser light is coupled into the lithium niobate microring resonator as pump light to generate a fundamental frequency optical comb and a frequency doubling optical comb. The electrodes are used to control the repetition frequency of the optical comb. The frequency-stabilized light source is used to excite the saturated absorption resonant transition of rubidium atoms on the D1 line and stabilize the frequency on the D1 line, serving as the frequency reference for the initial frequency phase-locked loop. The repetition frequency phase-locked loop adjusts the repetition frequency of the frequency doubling optical comb based on the error signal of the fluorescence intensity of the two-photon transition, so that the nth mode of the frequency doubling optical comb is aligned with the two-photon spectrum peak of the rubidium atom. The fluorescence intensity of the atomic two-photon transition radiation in the rubidium atom gas chamber is collected by the photomultiplier tube. The initial frequency phase-locked loop, the frequency-stabilized light source, and the m-th mode of the frequency-doubling optical comb beat the frequency, and the error is fed back to the pump light source through the initial frequency phase-locked loop; The repetitive frequency phase-locked loop and the initial frequency phase-locked loop continuously feed the frequency difference between the comb tooth frequency and the atomic frequency standard back to the feedback element of the microcavity optical comb until the frequency deviation stabilizes, thereby achieving long-term locking between the comb teeth and the atomic energy level.

2. The optical communication wavelength meter based on lithium niobate microcavity optical comb-excited rubidium atom two-photon transitions according to claim 1, characterized in that, The initial frequency phase-locked loop includes a phase detection module, which comprises a first photodetector, a second photodetector, a frequency divider, and a mixer. The first photodetector is used to obtain the beat frequency signal of the frequency-stabilized laser to the saturated absorption line of the rubidium atom D1 line and the m-th mode of the frequency-doubled optical comb, and inputs it into the mixer. The second photodetector is used to extract the repetition frequency signal of the frequency-doubled optical comb and input the repetition frequency signal into the mixer via the frequency divider. The mixer is used to obtain the error between the beat frequency signal and the repetition frequency division signal.

3. The optical communication wavelength meter based on lithium niobate microcavity optical comb-excited rubidium atom two-photon transitions according to claim 1, characterized in that, The pump source is an external cavity semiconductor pumped laser.

4. The optical communication wavelength meter based on lithium niobate microcavity optical comb-excited rubidium atom two-photon transitions according to claim 1, characterized in that, The frequency-stabilized light source uses a semiconductor laser.

5. The optical communication wavelength meter based on lithium niobate microcavity optical comb-excited rubidium atom two-photon transitions according to claim 1, characterized in that, The lithium niobate microring resonant cavity is etched using a femtosecond laser ablation method.

6. The optical communication wavelength meter based on lithium niobate microcavity optical comb-excited rubidium atom two-photon transitions according to claim 1, characterized in that, The electrode is made using an unetched chromium mask.

7. The optical communication wavelength meter based on lithium niobate microcavity optical comb-excited rubidium atom two-photon transitions according to claim 1, characterized in that, It also includes a dichroic beam splitter, which is used to separate the optical comb generated by the lithium niobate microring resonator into a fundamental frequency optical comb and a frequency doubling optical comb.

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