Multi-wavelength mode-locked laser based on FBG-PZT feedback optimization

Abstract

The invention provides a multi-wavelength mode-locked laser based on FBG-PZT feedback optimization, the laser comprises a pump light source, a wavelength division multiplexer, a feedback tuning member, a polarization controller, a polarization isolator, a tapered fiber and an output coupler which are connected in sequence, the pump light source emits pump light, and the output coupler outputs laser; the laser further comprises an optical detector and a piezoelectric ceramic driver, the optical detector receives laser output by the output coupler and converts an optical signal into an electric signal to be transmitted to the piezoelectric ceramic driver, the piezoelectric ceramic driver is connected with the feedback tuning part, and the piezoelectric ceramic driver calculates wavelength shift based on the received electric signal and transmits the wavelength shift to the output coupler. A control signal is sent to the feedback tuning part, and the feedback tuning part compensates filtering parameters of the conical optical fiber in real time based on the control signal.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber lasers, and particularly to a multi-wavelength mode-locked laser based on FBG-PZT feedback optimization. Background Art

[0002] In recent years, with the continuous development of laser technology, lasers have been increasingly widely used in multiple fields such as optical communication, optical sensing, and laser measurement. The multi-wavelength mode-locked fiber laser can simultaneously generate stable laser outputs at multiple wavelengths, and has significant advantages in applications such as high-precision sensing and wavelength-division multiplexing communication systems due to its high frequency, stability, and tunability.

[0003] The multi-wavelength mode-locked fiber laser is a special type of fiber laser, which is characterized by its ability to generate ultrashort pulses at different wavelengths simultaneously. This laser combines the advantages of multi-wavelength and mode-locking technologies and shows important application potential in multiple fields such as optical sensing, optical measurement, microwave photonics, optical signal processing, terahertz wave generation, and wavelength-division multiplexing (WDM) optical transmission systems. In terms of working principle, the multi-wavelength mode-locked fiber laser uses active or passive mode-locking technology to inject pump light into the gain medium, making the particles in the doped fiber reach the mode-locking threshold, thereby forming a positive feedback effect in the resonant cavity and realizing multi-longitudinal mode oscillation. These oscillation modes can form stable ultrashort pulses after multiple rounds of circulation in the cavity. In particular, the multi-wavelength mode-locked fiber laser can achieve this process at multiple wavelengths simultaneously, thus outputting ultrashort pulses of multiple wavelengths.

[0004] However, most of the existing multi-wavelength mode-locked lasers currently rely on traditional fiber resonant cavities, fiber gain media, and filters and other structures, and there are still many technical challenges in achieving stable multi-wavelength mode-locked output, especially in the design and precise control of filtering devices. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a multi-wavelength mode-locked laser based on FBG-PZT feedback optimization to eliminate or improve one or more defects existing in the prior art.

[0006] One aspect of the present invention provides a multi-wavelength mode-locked laser based on FBG-PZT feedback optimization, the laser comprising a pump light source, a wavelength division multiplexer, a feedback tuner, a polarization controller, a polarization isolator, a tapered fiber, and an output coupler connected in sequence, the pump light source emits pump light, and the laser is output by the output coupler;

[0007] The laser further includes a photodetector and a piezoelectric ceramic driver. The photodetector receives the laser output by the output coupler, converts the optical signal into an electrical signal and transmits it to the piezoelectric ceramic driver. The piezoelectric ceramic driver is connected to the feedback tuning member. The piezoelectric ceramic driver calculates the wavelength shift based on the received electrical signal and sends a control signal to the feedback tuning member. The feedback tuning member performs real-time compensation on the filtering parameters of the tapered fiber based on the control signal.

[0008] With the above solution, the present invention combines the tapered fiber with the feedback tuning member, and can achieve more accurate and stable multi-wavelength mode-locked laser output. The application of the tapered fiber in the laser resonator not only effectively utilizes its unique filtering characteristics, but also can accurately control the interval between the output wavelengths, thereby realizing the stable output of multi-wavelength laser. Compared with the traditional multi-wavelength mode-locked laser, the laser of the present invention has a simpler structure and higher wavelength adjustment accuracy. In addition, the introduction of the feedback tuning structure of the feedback tuning member significantly improves the stability of the laser output. This technical solution has high flexibility and adjustability, can meet the application requirements of high-precision lasers, and is particularly suitable for high-speed optical fiber communication, high-precision sensors and precision measurement fields.

[0009] In some embodiments of the present invention, the feedback tuning member adopts a structure in which a fiber Bragg grating is connected to a piezoelectric ceramic, and the fiber Bragg grating and the piezoelectric ceramic are tightly bonded using an adhesive.

[0010] In some embodiments of the present invention, during the process that the feedback tuning member performs real-time compensation on the filtering parameters of the tapered fiber based on the control signal, the feedback tuning member causes the piezoelectric ceramic to generate mechanical deformation based on the control signal, and applies tensile or compressive stress to the fiber Bragg grating through the mechanical deformation to adjust the Bragg wavelength of the fiber Bragg grating.

[0011] In some embodiments of the present invention, the process that the feedback tuning member performs real-time compensation on the filtering parameters of the tapered fiber based on the control signal includes:

[0012] The feedback tuning member calculates the central wavelength drift amount based on the reflection wavelength measured from the optical signal by the photodetector and the original reflection wavelength;

[0013] Based on the central wavelength shift amount, calculate the required axial strain of the fiber Bragg grating;

[0014] Based on the required axial strain of the fiber Bragg grating, calculate the required stress value of the fiber Bragg grating;

[0015] Based on the required stress value of the fiber Bragg grating, calculate the voltage applied to the piezoelectric ceramic.

[0016] In some embodiments of the present invention, in the step of calculating the axial strain required for the fiber Bragg grating based on the central wavelength offset, the axial strain is calculated according to the following formula:

[0017] Δλ = 0.79ε x ·λ B1 ;

[0018] where, Δλ represents the central wavelength offset, λ B1 represents the original reflection wavelength, and ε x represents the axial strain.

[0019] In some embodiments of the present invention, in the step of calculating the stress value required for the fiber Bragg grating based on the axial strain required for the fiber Bragg grating, the stress value required for the fiber Bragg grating is calculated according to the following formula:

[0020]

[0021] where, ε x represents the axial strain of the fiber Bragg grating, F represents the stress value of tension or contraction applied to the fiber Bragg grating by the mechanical deformation of the piezoelectric ceramic, E represents the Young's modulus, and S is the cross-sectional area of the fiber in which the fiber Bragg grating is located.

[0022] In some embodiments of the present invention, in the step of calculating the voltage applied to the piezoelectric ceramic based on the stress value required for the fiber Bragg grating, the value of the applied voltage is calculated according to the following formula:

[0023] F = d 33 ·V·E·S;

[0024] where, F represents the stress value of tension or contraction applied to the fiber Bragg grating by the mechanical deformation of the piezoelectric ceramic, V represents the value of the applied voltage, d 33 represents the piezoelectric constant of the piezoelectric ceramic, E represents the Young's modulus, and S is the cross-sectional area of the fiber in which the fiber Bragg grating is located.

[0025] In some embodiments of the present invention, a ytterbium-doped gain fiber is connected between the wavelength division multiplexer and the feedback tuner, and the ytterbium-doped gain fiber amplifies the optical signal to increase the frequency of the optical signal.

[0026] In some embodiments of the present invention, during the optical signal transmission process in which the laser emits pump light through the pump light source and outputs the laser through the output coupler, the transmission function of the tapered fiber is:

[0027]

[0028] where, The phase difference representing the mode interference effect of the tapered optical fiber; I co (λ) and I cl (λ) represent the light intensities of the core mode and the cladding mode of the tapered optical fiber, respectively; T(λ) represents the transmittance of light in the tapered optical fiber.

[0029] In some embodiments of the present invention, during the optical signal transmission process where the laser emits pump light through a pump light source and outputs laser light through an output coupler, the tapered optical fiber serves as a filtering device, and the free spectral range of the tapered optical fiber is:

[0030]

[0031] where Δ(λ) represents the free spectral range of the tapered optical fiber, λ represents the wavelength of the optical signal, and Δn eff represents the effective refractive index difference between the fundamental core mode and the high-order mode of the tapered optical fiber, and L represents the waist length of the tapered optical fiber.

[0032] The additional advantages, objectives, and features of the present invention will be partially elaborated in the following description, and will become partially apparent to those of ordinary skill in the art after studying the following text, or can be learned from the practice of the present invention. The objectives and other advantages of the present invention can be pointed out and obtained specifically in the specification and the drawings.

[0033] Those skilled in the art will understand that the objectives and advantages that can be achieved by the present invention are not limited to the above specific descriptions, and the above and other objectives that the present invention can achieve will be more clearly understood according to the following detailed description. Description of the Drawings

[0034] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and do not constitute a limitation to the present invention.

[0035] Figure 1 It is a schematic diagram of the overall architecture of the multi-wavelength mode-locked laser based on FBG-PZT feedback optimization for this solution;

[0036] Figure 2 It is a schematic diagram of the structure of the tapered optical fiber in this solution. Detailed Embodiments

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in combination with the embodiments and the drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but do not limit the present invention.

[0038] Here, it should also be noted that in order to avoid obscuring the present invention due to unnecessary details, only the structures and / or processing steps closely related to the solution according to the present invention are shown in the drawings, while other details less related to the present invention are omitted.

[0039] Most of the existing multi-wavelength mode-locked lasers rely on structures such as traditional fiber resonators, fiber gain media, and filters. There are still many technical challenges in achieving stable multi-wavelength mode-locked output, especially in the design and precise control of filtering devices.

[0040] Traditional multi-wavelength mode-locked fiber lasers usually rely on filtering devices such as fiber gratings, Fabry-Perot interferometers, or ring resonators. Although these filtering devices can provide certain filtering functions, they have problems such as complex structures, poor adjustment flexibility, and inaccurate parameter adjustment, resulting in limitations in the stability and accuracy of laser output. As a new type of filtering element, tapered fiber has shown good application prospects in multi-wavelength mode-locked fiber lasers due to its small volume, simple structure, and adjustable filtering bandwidth. By gradually changing the core structure of the tapered fiber, the multi-mode interference filtering effect can be effectively achieved, thereby realizing multi-wavelength mode-locked output, providing higher output stability and more precise wavelength control in multi-wavelength mode-locked lasers. Since such methods require controlling the period, central wavelength, and modulation depth of the filter by changing some corresponding parameters such as the device length, it is not easy to achieve precise control, which limits its practical application. Relying solely on the filtering characteristics of tapered fiber is not sufficient to completely solve the problems of the laser in terms of high stability, multi-wavelength output, and wavelength interval accuracy.

[0041] In order to further improve the performance of the laser and solve the deficiencies of tapered fiber in filtering performance, the present invention introduces a piezoelectric ceramic control (PZT) feedback tuning structure based on fiber Bragg grating (FBG) to improve the stability and adjustment accuracy of the system. Among them, fiber Bragg grating (FBG) has become a common means of realizing laser feedback tuning due to its characteristics such as high reflectivity, narrow bandwidth, and precise wavelength control. The FBG-PZT automatic feedback tuning structure can combine the dynamic response characteristics of PZT with the high-precision filtering function of FBG to optimize the laser output in real time, making up for the deficiencies of tapered fiber in adjustment accuracy and stability. Compared with the traditional structure, the present invention realizes more precise and stable multi-wavelength mode-locked output, providing a new solution for the development of high-performance fiber lasers.

[0042] Such as Figure 1As shown in the figure, the present invention proposes a multi-wavelength mode-locked laser based on FBG-PZT feedback optimization. The laser includes a pump light source, a wavelength division multiplexer, a feedback tuner, a polarization controller, a polarization isolator, a tapered fiber, and an output coupler connected in sequence. The pump light source emits pump light, and the laser is output by the output coupler.

[0043] In the specific implementation process, the pump light source uses a 980 nm pump light source.

[0044] In the specific implementation process, the laser further includes a photodetector and a piezoelectric ceramic driver. The photodetector receives the laser output by the output coupler, converts the optical signal into an electrical signal and transmits it to the piezoelectric ceramic driver. The piezoelectric ceramic driver is connected to the feedback tuner. The piezoelectric ceramic driver calculates the wavelength shift based on the received electrical signal and sends a control signal to the feedback tuner. The feedback tuner compensates the filtering parameters of the tapered fiber in real time based on the control signal.

[0045] In the specific implementation process, the optical signal is filtered by the tapered fiber. The tapered fiber realizes multi-wavelength mode-locked output through its unique geometric structure and mode coupling characteristics. This module has flexible adjustment capabilities, such as Figure 2 As shown in the figure, a, L, and d in the figure respectively represent the transition zone length, the waist length, and the waist diameter of the tapered fiber.

[0046] Specifically, the principle of the filtering characteristics of the tapered fiber is as follows: The signal light propagates in the core in the fundamental mode. Since the core radius gradually becomes smaller, the number of propagation modes in the core decreases, and part of the fundamental mode is coupled into the cladding and transmitted in the high-order mode. The light propagating in the core and the cladding has a phase difference due to the different environments (refractive index, boundary conditions) in which they are located, and thus an interference filtering effect is generated when coupling in the non-tapered region.

[0047] Adopting the above scheme, the present invention can realize more accurate and stable multi-wavelength mode-locked laser output by combining the tapered fiber with the feedback tuner. The application of the tapered fiber in the laser resonator not only effectively utilizes its unique filtering characteristics but also can accurately control the interval between the output wavelengths, thereby realizing the stable output of multi-wavelength lasers. Compared with the traditional multi-wavelength mode-locked laser, the laser structure of the present invention is simpler and has higher wavelength adjustment accuracy. In addition, the introduction of the feedback tuning structure of the feedback tuner significantly improves the stability of the laser output. This technical solution has high flexibility and tunability, can meet the application requirements of high-precision lasers, and is particularly suitable for high-speed optical fiber communication, high-precision sensors, and precision measurement fields.

[0048] Such as Figure 1As shown, in some embodiments of the present invention, the feedback tuning component adopts a structure in which an FBG and a PZT are combined in a composite manner. First, the FBG is closely attached to the surface of the PZT with an adhesive, and then clamped with a U-shaped clip.

[0049] In the specific implementation process, an optical fiber Bragg grating and a piezoelectric ceramic are closely bonded with an adhesive and clamped with a U-shaped clip.

[0050] Specifically, the FBG is arranged in the laser cavity of the laser for real-time monitoring of the wavelength and stability of the laser output. The FBG can accurately detect the wavelength drift information of the output through the wavelength change of the reflected optical signal.

[0051] In the specific implementation process, an optical fiber Bragg grating (FBG for short) is a passive filtering device formed by introducing periodic refractive index modulation into the optical fiber core through specific technical means; piezoelectric ceramics (PZT for short) are polycrystalline ceramic materials with piezoelectric effects. The piezoelectric effect means that when some materials are subjected to mechanical stress, they will generate electrode polarization phenomena and form charges on the surface of the materials; conversely, when an electric field is applied, the materials will undergo mechanical deformation. PZT is composed of zirconium titanate and lead titanate, and is formed by high-temperature sintering and polarization treatment, and has good piezoelectric properties and mechanical properties.

[0052] In some embodiments of the present invention, during the process of the feedback tuning component performing real-time compensation on the filtering parameters of the tapered optical fiber based on the control signal, the feedback tuning component causes the piezoelectric ceramic to generate mechanical deformation based on the control signal, and applies tensile or compressive stress to the optical fiber Bragg grating through the mechanical deformation to adjust the Bragg wavelength of the optical fiber Bragg grating.

[0053] In some embodiments of the present invention, the process of the feedback tuning component performing real-time compensation on the filtering parameters of the tapered optical fiber based on the control signal includes:

[0054] The feedback tuning component calculates the central wavelength drift amount based on the reflected wavelength measured from the optical signal by the photodetector and the original reflected wavelength;

[0055] Based on the central wavelength offset amount, calculate the axial strain required for the optical fiber Bragg grating;

[0056] Based on the axial strain required for the optical fiber Bragg grating, calculate the stress value required for the optical fiber Bragg grating;

[0057] Based on the stress value required for the optical fiber Bragg grating, calculate the voltage applied to the piezoelectric ceramic.

[0058] Specifically, the optical detector converts the monitored system output signal into an electrical signal, and the converted electrical signal is output to the piezoelectric ceramic driver for amplification, causing the PZT to generate mechanical deformation. The deformation is used to apply tensile or compressive stress to the FBG, thereby precisely adjusting the Bragg wavelength of the FBG and achieving strain adjustment of the FBG.

[0059] With the above solution, when the output wavelength deviation is detected in this solution, the feedback tuning component of the FBG-PZT combination immediately responds and compensates the filtering parameters of the tapered fiber in real time, enabling the laser to always operate in the optimal working state. During the entire operation of the laser, the tapered fiber and the FBG-PZT feedback tuning system complement each other: the tapered fiber is responsible for achieving the preliminary filtering effect of multi-wavelength mode locking, while the FBG-PZT module further optimizes the output performance through precise feedback control, ensuring that the laser has higher stability and wavelength accuracy. This combined structure not only solves the accuracy bottleneck of the traditional laser in the filtering module but also significantly improves its adaptability to environmental changes. The key innovation point of this solution lies in the combination of the application of the tapered fiber and the automatic feedback tuning of the FBG-PZT. Through the synergistic effect of the two, it can provide stable and high-precision multi-wavelength mode-locked laser output in more complex application scenarios.

[0060] The FBG adopted in this solution is written by exposure under ultraviolet laser using a mask plate, and the grating period can be obtained from the Bragg grating equation:

[0061] λ B =2n eff Λ

[0062] where λ B represents the central wavelength, n eff represents the effective refractive index of the core, and Λ represents the period of the photolithography mask plate.

[0063] In some embodiments of the present invention, in the step of calculating the axial strain required for the fiber Bragg grating based on the central wavelength offset, the axial strain is calculated based on the following formula:

[0064] Δλ=0.79ε x ·λ B1 ;

[0065] where Δλ represents the central wavelength offset, λ B1 represents the original reflection wavelength, and ε x represents the axial strain.

[0066] Specifically, since the central wavelength of the FBG will be tuned as external factors such as external force, temperature, and humidity change, the tunability is based on this principle (mainly stress) to tune the wavelength. In the experiment, a piezoelectric ceramic (PZT) is used to tune the wavelength, and the magnitude of the wavelength tuning is proportional to the external stress.

[0067] In some embodiments of the present invention, in the step of calculating the stress value required for the fiber Bragg grating based on the axial strain required for the fiber Bragg grating, the stress value required for the fiber Bragg grating is calculated based on the following formula:

[0068]

[0069] where ε x represents the axial strain of the fiber Bragg grating, F represents the stress value of tensile or compressive force applied to the fiber Bragg grating due to the mechanical deformation generated by the piezoelectric ceramic, E represents the Young's modulus, and S is the cross-sectional area of the fiber in which the fiber Bragg grating is located.

[0070] According to the characteristics of the piezoelectric ceramic, the following relationship exists between the deformation amount ΔL of the PZT and the voltage V applied by the piezoelectric ceramic driver:

[0071] ΔL = d 33 ·V·L 0

[0072] where d 33 represents the piezoelectric constant of the PZT, and L 0 represents the initial length of the PZT.

[0073] The axial strain of the FBG is determined by the deformation amount ΔL of the PZT, and the specific relationship is as follows:

[0074]

[0075] By adjusting the magnitude of the applied voltage, the stress magnitude F borne by the fiber can be controlled to achieve strain adjustment of the FBG:

[0076] ε x = d 33 ·V

[0077] Adopting the above scheme, on the premise that the effective refractive index and the template period are certain, if it is desired to increase the wavelength tuning amount, only ε xValue. It can be seen from the above formula that increasing the stress value or decreasing the cross-sectional area S can increase the tuning amount. Reducing the cross-sectional area can obtain a larger wavelength tuning under the premise of the same stress. However, after reducing the cross-sectional area, the fiber has a very thin core, and it is very difficult to focus when using ultraviolet lithography to write gratings. The writing process is greatly lengthened, and the writing depth is limited. Therefore, mainly discuss increasing the stress value and increasing the tuning amount of the wavelength.

[0078] In some embodiments of the present invention, in the step of calculating the voltage applied to the piezoelectric ceramic based on the stress value required for the fiber Bragg grating, the value of the applied voltage is calculated based on the following formula:

[0079] F = d 33 ·V·E·S;

[0080] Wherein, F represents the stress value of stretching or shrinking applied to the fiber Bragg grating by the mechanical deformation generated by the piezoelectric ceramic, V represents the value of the applied voltage, d 33 represents the piezoelectric constant of the piezoelectric ceramic, E represents the Young's modulus, and S is the cross-sectional area of the fiber where the fiber Bragg grating is located.

[0081] In some embodiments of the present invention, a ytterbium-doped gain fiber is connected between the wavelength division multiplexer and the feedback tuning element, and the ytterbium-doped gain fiber amplifies the optical signal and improves the frequency of the optical signal.

[0082] In the specific implementation process, the output of the pump light source is transmitted to the ytterbium-doped gain fiber through the wavelength division multiplexer, and the gain effect is realized in the ytterbium-doped gain fiber, and a high-frequency optical signal is excited.

[0083] In some embodiments of the present invention, during the transmission process of the optical signal of the pump light emitted by the laser through the pump light source and output by the output coupler, the transmission function of the tapered fiber is:

[0084]

[0085] Wherein, represents the phase difference of the mode interference effect of the tapered fiber; I co (λ) and I cl (λ) represent the optical intensities of the core mode and the cladding mode of the tapered fiber respectively; T(λ) represents the transmittance of light in the tapered fiber.

[0086] In some embodiments of the present invention, during the transmission process of the optical signal of the pump light emitted by the laser through the pump light source and output by the output coupler, the tapered fiber is used as a filtering device, and the free spectral range (FSR) of the tapered fiber is:

[0087]

[0088] where Δ(λ) represents the free spectral range of the tapered fiber, λ represents the wavelength of the optical signal, and Δn eff represents the effective refractive index difference between the fundamental core mode and the high-order mode of the tapered fiber, and L represents the waist length of the tapered fiber.

[0089] It can be seen that changing the waist length can change the free spectral range of the transfer function.

[0090] Adopting the above scheme, a filtering effect is provided by the tapered fiber to achieve multi-wavelength mode-locked output, and the FBG-PZT feedback tuning system is used to compensate the parameters of the tapered fiber in real time, thereby improving the accuracy and stability of the multi-wavelength output.

[0091] In summary, the present invention provides a multi-wavelength mode-locked fiber laser based on FBG-PZT feedback optimization. By combining the tapered fiber with the FBG-PZT automatic feedback tuning, the disadvantage of inaccurate adjustment of the tapered fiber parameters in the traditional method is overcome, and the output performance and stability of the laser are improved, so as to achieve accurate and controllable multi-wavelength mode-locked output. The core of the present invention lies in the close combination of the tapered fiber and the FBG-PZT automatic feedback tuning structure, further improving the output accuracy, stability and reliability of the laser.

[0092] Those of ordinary skill in the art should understand that the various exemplary components, systems, and methods described in connection with the embodiments disclosed herein can be implemented in hardware, software, or a combination of both. Specifically, whether to implement in hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention. When implemented in hardware, it can be, for example, an electronic circuit, an application-specific integrated circuit (ASIC), appropriate firmware, a plug-in, a functional card, etc. When implemented in software, the elements of the present invention are programs or code segments used to perform the required tasks. The program or code segment can be stored in a machine-readable medium or transmitted through a data signal carried in a carrier wave on a transmission medium or a communication link.

[0093] It should be clear that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order between steps after understanding the spirit of the present invention.

[0094] In the present invention, features described and / or illustrated for one embodiment may be used in the same manner or in a similar manner in one or more other embodiments, and / or combined with the features of other embodiments or replace the features of other embodiments.

[0095] The foregoing are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various modifications and variations can be made to the embodiments of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A multi-wavelength mode-locked laser based on FBG-PZT feedback optimization, characterized in that: The laser comprises a pump light source, a wavelength division multiplexer, a feedback tuner, a polarization controller, a polarization isolator, a tapered optical fiber and an output coupler which are connected in sequence. The pump light source emits pump light, and the output coupler outputs laser light. The laser also includes a light detector and a piezoelectric ceramic driver. The light detector receives the laser output by the output coupler and converts the optical signal into an electrical signal and transmits it to the piezoelectric ceramic driver. The piezoelectric ceramic driver is connected to a feedback tuning component. The piezoelectric ceramic driver calculates the wavelength shift based on the received electrical signal and sends a control signal to the feedback tuning component. The feedback tuning component compensates the filtering parameters of the tapered optical fiber in real time based on the control signal.

2. The multi-wavelength mode-locked laser based on FBG-PZT feedback optimization according to claim 1, characterized in that: The feedback tuning element adopts a structure in which a fiber Bragg grating is connected to a piezoelectric ceramic, and an adhesive is used to tightly bond the fiber Bragg grating to the piezoelectric ceramic.

3. The multi-wavelength mode-locked laser based on FBG-PZT feedback optimization according to claim 2, characterized in that: In the process of the feedback tuning component performing real-time compensation on the filtering parameters of the tapered optical fiber based on the control signal, the feedback tuning component causes the piezoelectric ceramic to generate mechanical deformation based on the control signal, applies tensile or contractive stress to the fiber Bragg grating through the mechanical deformation, and adjusts the Bragg wavelength of the fiber Bragg grating.

4. The multi-wavelength mode-locked laser based on FBG-PZT feedback optimization according to claim 2, characterized in that: The process of the feedback tuning component performing real-time compensation on the filtering parameters of the tapered optical fiber based on the control signal includes: The feedback tuning element calculates the center wavelength drift based on the reflection wavelength measured by the light detector from the optical signal and the original reflection wavelength; Calculating the axial strain required for the fiber Bragg grating based on the central wavelength offset; Calculating the stress value required for the fiber Bragg grating based on the axial strain required for the fiber Bragg grating; The voltage applied to the piezoelectric ceramic is calculated based on the stress value required for the fiber Bragg grating.

5. The multi-wavelength mode-locked laser based on FBG-PZT feedback optimization according to claim 4, characterized in that: In the step of calculating the axial strain amount required for the fiber Bragg grating based on the central wavelength offset, the axial strain amount is calculated based on the following formula: Δλ=0.79ε x ·l B1 ; Where Δλ represents the center wavelength offset, λ B1 represents the original reflection wavelength, ε x represents the axial strain.

6. The multi-wavelength mode-locked laser based on FBG-PZT feedback optimization according to claim 4, characterized in that: In the step of calculating the stress value required by the fiber Bragg grating based on the axial strain amount required by the fiber Bragg grating, the stress value required by the fiber Bragg grating is calculated based on the following formula: in,· x represents the axial strain of the fiber Bragg grating, F represents the stress value of stretching or contracting the fiber Bragg grating due to mechanical deformation of the piezoelectric ceramic, E represents Young's modulus, and S is the cross-sectional area of ​​the optical fiber where the fiber Bragg grating is located.

7. The multi-wavelength mode-locked laser based on FBG-PZT feedback optimization according to claim 4, characterized in that: In the step of calculating the voltage applied to the piezoelectric ceramic based on the stress value required for the fiber Bragg grating, the value of the applied voltage is calculated based on the following formula: F=d 33 ·V·E·S; Where F represents the stress value of stretching or contraction of the fiber Bragg grating caused by mechanical deformation of the piezoelectric ceramic, V represents the value of the applied voltage, and d 33 represents the piezoelectric constant of the piezoelectric ceramic, E represents the Young's modulus, and S represents the cross-sectional area of ​​the optical fiber where the fiber Bragg grating is located.

8. The multi-wavelength mode-locked laser based on FBG-PZT feedback optimization according to claim 1, characterized in that: The wavelength division multiplexer and the feedback tuning element are connected by an ytterbium-doped gain optical fiber, and the ytterbium-doped gain optical fiber amplifies the optical signal to increase the frequency of the optical signal.

9. The multi-wavelength mode-locked laser based on FBG-PZT feedback optimization according to claim 1, characterized in that: In the optical signal transmission process in which the laser emits pump light through the pump light source and the output coupler outputs the laser, the transmission function of the tapered optical fiber is: in, The phase difference representing the mode interference effect of the tapered fiber; I co (λ) and I cl (λ) represents the light intensity of the core mode and cladding mode of the tapered optical fiber respectively; T(λ) represents the transmittance of light in the tapered optical fiber.

10. The multi-wavelength mode-locked laser based on FBG-PZT feedback optimization according to claim 1, characterized in that: In the optical signal transmission process in which the laser emits pump light through the pump light source and the output coupler outputs the laser, the tapered optical fiber is used as a filter element, and the free spectrum range of the tapered optical fiber is: Where Δ(λ) represents the free spectral range of the tapered fiber, λ represents the wavelength of the optical signal, and Δn eff It represents the effective refractive index difference between the fundamental core mode of the tapered fiber and the high-order mode of the tapered fiber, and L represents the waist length of the tapered fiber.

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