Quantum dot optical frequency comb repetition frequency multiplication system and method based on time Talbot effect

Abstract

The invention discloses a quantum dot optical frequency comb repetition frequency multiplication system and method based on the time Talbot effect. The quantum dot optical frequency comb repetition frequency multiplication system comprises a quantum dot optical frequency comb source and a Talbot dispersion regulator. The optical frequency comb source generates an input optical frequency comb with repetition frequency; and the dispersion regulator calculates and applies a target total second-order group velocity dispersion amount meeting a fractional order time Talbot phase condition according to a preset integer multiplication factor N, so that the input optical frequency comb generates coherent time domain self-imaging and then forms an output optical frequency comb with repetition frequency. And multiplication is realized only through passive dispersion regulation and control, a high-speed active modulator is not needed, the energy efficiency is high, the structure is simple, and different high repetition frequency requirements of 200GHz and above can be met.

Description

Technical Field

[0001] This invention belongs to the field of quantum dot laser technology, and in particular relates to a quantum dot optical frequency comb repetition rate multiplication system and method based on the time Talbot effect, which is applicable to high-speed optical transmission systems, multi-carrier modulation, microwave photonics and related photonic applications. Background Technology

[0002] An optical frequency comb is a coherent light source with equally spaced discrete spectral lines in the frequency domain and corresponding to periodic ultrashort pulse sequences in the time domain. Due to its simultaneous frequency accuracy and time stability, it has significant application value in precision spectral measurement, microwave photonics, high-speed optical communication, and optical signal processing. The repetition frequency (i.e., the spacing between adjacent spectral lines or the pulse repetition rate) of an optical frequency comb is one of the key parameters determining its usable channel density and system throughput.

[0003] With the development of coherent optical communication, dense wavelength division multiplexing (DWDM), and frequency comb-based multicarrier modulation technology, high-speed optical transmission systems are placing higher demands on light sources. In particular, in systems of 100 Gbps and above, optical frequency combs with repetition frequencies of 100 GHz or even higher are gradually becoming one of the key light sources.

[0004] In existing technologies, optical frequency combs are typically generated using mode-locked lasers or based on Fabry-Pérot (FP) cavity structures. For FP-based optical frequency combs, the repetition rate is inversely proportional to the cavity length. Therefore, to obtain higher repetition rates, the cavity length needs to be significantly shortened, but this leads to problems such as difficulties in device integration, increased mode competition, decreased thermomechanical stability, and increased manufacturing and packaging difficulties, limiting engineering applications. Therefore, there is an urgent need for a technical solution that can achieve high repetition rate optical frequency combs without relying on cavity length limits or high-speed electro-optic phase modulators, while maintaining high energy utilization and system stability. Summary of the Invention

[0005] To address the above technical problems, this invention provides a quantum dot optical frequency comb repetition rate multiplication system and method based on the time Talbot effect.

[0006] The technical solution adopted by this invention to solve its technical problem is: A quantum dot optical frequency comb frequency multiplication system based on the time Talbot effect includes: Quantum dot optical frequency comb source, used to generate input optical frequency comb; The Talbot dispersion modulator has its optical input connected to the output of a quantum dot optical frequency comb source. Based on the target repetition frequency multiplication factor N, a target total second-order group velocity dispersion that satisfies the fractional-time Talbot effect is applied, causing the input optical frequency comb to generate coherent time-domain self-imaging and form an output optical frequency comb. The repetition frequency of the output optical frequency comb is N times the repetition frequency of the input optical frequency comb, where N is an integer multiplication factor greater than or equal to 2.

[0007] Preferably, the total second-order group velocity dispersion GDD needs to satisfy the fractional-time Talbot condition, specifically: ; ; Where m is a positive integer. For the input pulse period, This is the repetition frequency of the input optical frequency comb.

[0008] Preferably, the quantum dot optical frequency comb source is an optical frequency comb source based on a quantum dot mode-locked laser, and its repetition frequency is... It is 100 GHz, with the center wavelength located in the O band.

[0009] Preferably, the Talbot dispersion modulator includes a dispersion device for providing the target total second group velocity dispersion (GDD); the dispersion device is at least one of dispersion-compensating fiber and chirped fiber Bragg grating.

[0010] Preferably, when the dispersion device is a dispersion-compensating fiber, the total second-order group velocity dispersion GDD provided by the dispersion-compensating fiber is determined by the second-order dispersion coefficient of the dispersion fiber. and the length of the dispersive medium Decide.

[0011] Preferably, the length L of the dispersion-compensating fiber is determined by the following formula to achieve the GDD value that satisfies the fractional-time Talbot condition: .

[0012] Preferably, when the dispersive device is a chirped fiber Bragg grating, a signal is provided at the center wavelength of the input optical frequency comb that is in harmony with the target. Equal group delay dispersion.

[0013] Preferably, when the dispersive characteristics of the dispersive device are characterized by the dispersive parameter D, the second-order dispersive coefficient... The conversion relationship with the dispersion parameter D is as follows: ; Where λ is the center wavelength of the input optical frequency comb, c is the speed of light in vacuum, and the unit of the dispersion parameter D is ps / (nm·km).

[0014] Preferably, the system further includes a verification module, the input of which receives the optical signal output by the Talbot dispersion modulator to characterize the characteristics of the output optical frequency comb; The verification module includes at least one of the following units: High-resolution spectrometer unit, used to analyze the spectral comb tooth spacing of the output optical frequency comb; An autocorrelator or optical sampling oscilloscope unit is used to measure the time-domain pulse waveform of the output optical frequency comb; The electro-optic modulation and beat frequency detection unit is used to perform down-conversion detection on the optical frequency comb signal.

[0015] A method for doubling the repetition frequency of a quantum dot optical frequency comb based on the time-Talbot effect includes the following steps: Provide one input optical frequency comb; Based on the target repetition frequency multiplication factor N, the target total second-order group velocity dispersion that satisfies the fractional-time Talbot effect is determined. A predetermined amount of total second-order group velocity dispersion is applied to the Talbot dispersion modulator, so that the input optical frequency comb generates coherent time-domain self-imaging and forms the output optical frequency comb. The repetition frequency of the output optical frequency comb is N times the repetition frequency of the input optical frequency comb, where N is an integer multiplication factor greater than or equal to 2.

[0016] This invention achieves predictable and deterministic doubling of the repetition frequency of a quantum dot optical frequency comb by pre-determining and applying a precise dispersion measure that satisfies the Talbot condition based on a target multiplication factor N. This parameterized design method ensures the output repetition frequency. The system achieves precise multiplication and generates N strictly equidistant pulse peaks within each input cycle, ensuring reliable performance and eliminating the need for dynamic feedback. The entire multiplication process is based on passive linear phase modulation, resulting in high energy efficiency and excellent signal quality. Furthermore, by flexibly setting the integer N, it can adapt to various high repetition rate requirements at 200 GHz and above, and its simple structure facilitates easy engineering implementation. Attached Figure Description

[0017] Figure 1 A schematic diagram of a frequency comb system for improving repetition frequency provided by the present invention; Figure 2 A schematic diagram of the input and output spectra in one embodiment of the present invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0019] To achieve a doubling of repetition frequency, this invention utilizes the time-Talbot effect. The time-Talbot effect is a time-domain self-imaging phenomenon that occurs when a periodic pulse sequence propagates in a medium with a defined second-order group velocity dispersion. When the pulse sequence passes through a medium with a certain group delay dispersion, each comb tooth acquires a quadratic spectral phase proportional to the square of the frequency shift, resulting in a coherent rearrangement of the frequency-domain phase relationship. When the fractional Talbot condition is satisfied, the time-domain waveform forms multiple equally spaced sub-pulses within each original period, manifesting as an integer multiple increase in repetition frequency. Thus, an integer multiple increase in repetition frequency is achieved without the need for a high-speed electro-optic phase modulator, generating a high-repetition-frequency optical comb suitable for high-speed optical transmission systems.

[0020] The objective of this invention can be achieved through the following technical solutions.

[0021] A quantum dot optical frequency comb repetition rate multiplication system based on the time-Talbot effect includes a quantum dot optical frequency comb source and a Talbot dispersion modulator.

[0022] A quantum dot optical frequency comb source is used to generate the input optical frequency comb, the repetition frequency of which is... Its frequency domain contains equally spaced discrete spectral lines, with a spectral line spacing of [missing information]. The time domain is .

[0023] Furthermore, the quantum dot optical frequency comb source is an optical frequency comb source based on a quantum dot mode-locked laser, and its repetition frequency is... It is 100 GHz, with the center wavelength located in the O band.

[0024] The Talbot dispersion modulator connects its optical input to the output of a quantum dot optical frequency comb source. Based on the target repetition frequency multiplication factor N, it determines and applies a target total second-order group velocity dispersion (GDD) that satisfies the fractional-time Talbot effect, causing the input optical frequency comb to produce a coherent temporal self-imaging effect, thus forming the output optical frequency comb. The repetition frequency of the output optical frequency comb... Furthermore, its time-domain waveform in each input pulse period It presents N equally spaced pulse peaks, where N is an integer multiplication factor greater than or equal to 2.

[0025] Specifically, the schematic diagram is as follows: Figure 1 As shown.

[0026] In one embodiment, the total second-order group velocity dispersion GDD needs to satisfy the fractional-time Talbot condition, specifically: ; ; Where m is a positive integer. For the input pulse period, This is the repetition frequency of the input optical frequency comb.

[0027] In one embodiment, the Talbot dispersion modulator includes a dispersion device for providing a target total second group velocity dispersion (GDD); the dispersion device is at least one of dispersion-compensating fiber and chirped fiber Bragg grating.

[0028] In one embodiment, when the dispersion device is a dispersion-compensating fiber, the total second-order group velocity dispersion GDD provided by the dispersion-compensating fiber is determined by the second-order dispersion coefficient of the dispersion-compensating fiber. and the length of the dispersive medium Decide.

[0029] in, The positive and negative signs correspond to normal dispersion / anomalous dispersion. The frequency doubling condition of this invention mainly depends on whether the target |GDD| satisfies the Talbot condition; therefore, the Talbot dispersion modulator can be adopted. Dispersive media that are either positive or negative.

[0030] Furthermore, the Talbot dispersion modulator can employ dispersion-compensating fiber, chirped fiber Bragg grating (CFBG), or other equivalent dispersion devices. The parameter determination steps are as follows: 1) Determine the input repetition frequency, for example ,but ; 2) Determine the target multiplication factor, for example, N=2 (output 200 GHz); 3) Calculate the target total second dispersion based on the above Talbot conditions. ; 4) Calculate and determine the device parameters based on the type of dispersive device.

[0031] Specifically, the final spectral diagram is as follows: Figure 2 As shown.

[0032] In one embodiment, the length L of the dispersion-compensating fiber is determined to achieve a GDD value that satisfies the fractional-time Talbot condition, as follows: ; in, For the target GDD value, Let be the second-order dispersion coefficient of the dispersive fiber. For example, take... Therefore, L≈7.96 / 21≈0.38 km.

[0033] In one embodiment, when the dispersive device is a chirped fiber Bragg grating, a signal with the target wavelength is provided at the center wavelength of the input optical frequency comb. Equal group delay dispersion.

[0034] Furthermore, according to the target Select a fixed or tunable CFBG of appropriate specifications to provide the required output at the center wavelength. Fine matching can be achieved through cascading or adjustable structures when necessary.

[0035] In one embodiment, when the dispersive properties of the dispersive medium are characterized by the dispersive parameter D, the second-order dispersion coefficient... The conversion relationship with the dispersion parameter D is as follows: ; Where λ is the center wavelength of the input optical frequency comb, c is the speed of light in vacuum, and the unit of the dispersion parameter D is ps / (nm·km).

[0036] In one detailed embodiment, the repetition frequency is input. The center wavelength λ can be 1310 nm (O band). Input pulse period: ; The frequency domain comb tooth angular frequency of the input optical frequency comb is expressed as: ; When the optical frequency comb passes through the Talbot dispersion modulator, the dispersion device applies a secondary spectral phase: ; Therefore, the phase of the quadratic spectrum obtained by the kth comb tooth is: ; When GDD satisfies the Talbot condition, the relative phases of each comb tooth are coherently rearranged, and the output intensity is... It repeats in the basic cycle, that is, in each original cycle Two equally spaced sub-pulses are formed within (interval) This achieves the output repetition frequency: ; When the total second-order dispersion satisfies the fractional-time Talbot condition, where N is the target multiplication factor (2, 4, 8…) and m is a positive integer, the output intensity waveform follows the... This is a fundamental periodic repetition. Equivalently, at any length T... in N occurrences with Δt = within a time window The equally spaced sub-pulse peaks increase the output repetition frequency to: ; In one embodiment, a verification module is also included, the input of which receives the optical signal output by the Talbot dispersion modulator to characterize the characteristics of the output optical frequency comb. The verification module includes at least one of the following units: High-resolution spectrometer unit, used to analyze the spectral comb tooth spacing of the output optical frequency comb; An autocorrelator or optical sampling oscilloscope unit is used to measure the time-domain pulse waveform of the output optical frequency comb; The electro-optic modulation and beat frequency detection unit is used to perform down-conversion detection on the optical frequency comb signal.

[0037] Specifically, the verification module is used to verify the repetition frequency and spectral structure of the output optical frequency comb. For optical frequency combs with repetition frequencies of 200 GHz and above, one or a combination of the following methods can be used: (i) Optical frequency domain detection: High-resolution spectrometer analysis to obtain changes in spectral line spacing; (ii) Time-domain detection: Verify the shortening of the time-domain period using an autocorrelation instrument or optical sampling oscilloscope system; (iii) Electro-optic downconversion detection: High repetition frequency information is mapped to measurable electrical frequency bands by using electro-optic modulation / beat frequency mapping to achieve equivalent downconversion characterization.

[0038] Furthermore, the Talbot dispersion modulator can employ different types of dispersion media or programmable phase filter structures; the verification module can employ different frequency domain / time domain / down-conversion measurement methods. Any method that achieves the above-mentioned technical effects should fall within the protection scope of this invention.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects: 1) The repetition frequency of the optical frequency comb can be doubled using only dispersive devices, without the need for a high-speed phase modulator; 2) The coherent self-imaging mechanism based on the time-Talbot effect has high energy utilization. This repetition rate doubling process is a passive linear phase processing, which theoretically does not change the total energy of the optical signal. The energy loss mainly comes from passive losses such as insertion loss and coupling loss of dispersive devices. 3) By utilizing the time-Talbot effect to generate frequency-doubled optical combs, quantum dot optical combs with high repetition rates of 200 GHz and above can be realized, which can be applied to high-speed optical transmission systems; 4) The system has a simple structure and is easy to implement.

[0040] In one embodiment, a method for doubling the repetition frequency of a quantum dot optical frequency comb based on the time Talbot effect includes the following steps: An input optical frequency comb is provided, and the repetition frequency of the input optical frequency comb is... ; Based on the target repetition frequency multiplication factor N, the target total second-order group velocity dispersion that satisfies the fractional-time Talbot effect is determined. A predetermined amount of total second-order group velocity dispersion is applied to the Talbot dispersion modulator, causing the input optical frequency comb to produce a coherent time-domain self-imaging effect, forming the output optical frequency comb. The repetition frequency of the output optical frequency comb is... N is an integer multiplier greater than or equal to 2.

[0041] For specific limitations regarding the quantum dot optical frequency comb repetition frequency multiplication method based on the time Talbot effect, please refer to the limitations of the quantum dot optical frequency comb repetition frequency multiplication system based on the time Talbot effect mentioned above, which will not be repeated here.

[0042] The foregoing has provided a detailed description of a quantum dot optical frequency comb repetition frequency multiplication method and system based on the time-Talbot effect, as provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention, and the descriptions of the embodiments above are merely for the purpose of helping to understand the core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A quantum dot optical frequency comb repetition rate multiplication system based on the time Talbot effect, characterized in that, include: Quantum dot optical frequency comb source, used to generate input optical frequency comb; The Talbot dispersion modulator has its optical input connected to the output of a quantum dot optical frequency comb source. Based on the target repetition frequency multiplication factor N, a target total second-order group velocity dispersion that satisfies the fractional-time Talbot effect is applied, causing the input optical frequency comb to generate coherent time-domain self-imaging and form an output optical frequency comb. The repetition frequency of the output optical frequency comb is N times the repetition frequency of the input optical frequency comb, where N is an integer multiplication factor greater than or equal to 2.

2. The system according to claim 1, characterized in that, The total second-order group velocity dispersion GDD must satisfy the fractional-time Talbot condition, specifically: ； ； Where m is a positive integer. For the input pulse period, This is the repetition frequency of the input optical frequency comb.

3. The system according to claim 2, characterized in that, The quantum dot optical frequency comb source is an optical frequency comb source based on a quantum dot mode-locked laser, and its repetition frequency is... It is 100 GHz, with the center wavelength located in the O band.

4. The system according to claim 3, characterized in that, The Talbot dispersion modulator includes a dispersion device that provides the target total second group velocity dispersion (GDD). The dispersion device is at least one of dispersion-compensating fiber and chirped fiber Bragg grating.

5. The system according to claim 4, characterized in that, When the dispersive device is a dispersion-compensated fiber, the total second-order group velocity dispersion GDD provided by the dispersion-compensated fiber is determined by the second-order dispersion coefficient of the dispersion-compensated fiber. and the length of the dispersive medium Decide.

6. The system according to claim 5, characterized in that, To achieve the GDD value that satisfies the fractional-time Talbot condition, the length L of the dispersion-compensating fiber is determined by the following formula: 。 7. The system according to claim 4, characterized in that, When the dispersive device is a chirped fiber Bragg grating, it provides a signal at the center wavelength of the input optical frequency comb that is in harmony with the target. Equal group delay dispersion.

8. The system according to claim 5 or 7, characterized in that, When the dispersive characteristics of a dispersive device are characterized by the dispersive parameter D, the second-order dispersive coefficient... The conversion relationship with the dispersion parameter D is as follows: ； Where λ is the center wavelength of the input optical frequency comb, c is the speed of light in vacuum, and the unit of the dispersion parameter D is ps / (nm·km).

9. The system according to claim 8, characterized in that, It also includes a verification module, whose input receives the optical signal output from the Talbot dispersion modulator to characterize the output optical frequency comb. The verification module includes at least one of the following units: High-resolution spectrometer unit, used to analyze the spectral comb tooth spacing of the output optical frequency comb; An autocorrelator or optical sampling oscilloscope unit is used to measure the time-domain pulse waveform of the output optical frequency comb; The electro-optic modulation and beat frequency detection unit is used to perform down-conversion detection on the optical frequency comb signal.

10. A method for doubling the repetition frequency of a quantum dot optical frequency comb based on the time Talbot effect, characterized in that, Includes the following steps: Provide one input optical frequency comb; Based on the target repetition frequency multiplication factor N, the target total second-order group velocity dispersion that satisfies the fractional-time Talbot effect is determined. A predetermined amount of total second-order group velocity dispersion is applied to the Talbot dispersion modulator, so that the input optical frequency comb generates coherent time-domain self-imaging and forms the output optical frequency comb. The repetition frequency of the output optical frequency comb is N times the repetition frequency of the input optical frequency comb, where N is an integer multiplication factor greater than or equal to 2.

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