Ring cavity multiwavelength thulium-doped fiber laser based on mach-zehnder interferometer

Abstract

The application provides a kind of based on Mach-Zehnder interferometer annular cavity multi-wavelength thulium-doped fiber laser, it relates to fiber laser technical field, the laser is composed of semiconductor laser and annular cavity, the annular cavity includes wavelength division multiplexer, thulium-doped fiber, isolator, fiber coupler, polarizer, Mach-Zehnder interference filter, black phosphorus saturable absorber and polarization controller.The application effectively overcomes gain competition and mode competition by integrating Mach-Zehnder interference filter with black phosphorus saturable absorber, realizes stable mode-locked laser output from single wavelength to multi-wavelength, and simultaneously exhibits a tunable spectral range of up to 55.8nm, meeting the needs of wavelength diversity for different application scenarios.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber lasers, in particular to a ring cavity multi-wavelength thulium-doped fiber laser based on a Mach-Zehnder interferometer. BACKGROUND

[0002] In the field of fiber lasers, thulium-doped fiber lasers have attracted extensive attention due to their excellent performance and wide application prospects. In particular, multi-wavelength thulium-doped fiber lasers have shown significant diversity and flexibility in the fields of optical communication, spectral analysis, and medical imaging. Set Sze Yun et al. from Tokyo University achieved a dual-wavelength mode-locked fiber laser by using a birefringent Lyot filter. This method uses the birefringence characteristics to stabilize the dual-wavelength output, demonstrating the application potential of dual-wavelength lasers. At the same time, Yan et al. from Nanyang Technological University demonstrated a tunable multi-wavelength thulium-doped mode-locked fiber laser, which achieved tuning between multiple wavelengths through a periodic cavity transfer modulation technique, indicating the flexibility of multi-wavelength laser output.

[0003] However, there are some deficiencies in the prior art in realizing multi-wavelength mode locking. Most of the lasers use birefringence-induced filters and double-hump gain spectra, but the gain competition effect makes it difficult for these lasers to support more stable wavelength pulses. The gain competition effect can cause uneven energy distribution between different wavelengths, affecting the stability of the laser. In addition, multi-wavelength thulium-doped fiber lasers usually face the problems of obvious mode competition and poor mode locking stability, which limit their performance and practical application. SUMMARY

[0004] To this end, the present application provides a ring cavity multi-wavelength thulium-doped fiber laser based on a Mach-Zehnder interferometer, which solves the problem of obvious mode competition and poor mode locking stability in the prior art in multi-wavelength thulium-doped fiber lasers.

[0005] To solve the above problems, the present application provides a ring cavity multi-wavelength thulium-doped fiber laser based on a Mach-Zehnder interferometer, which is composed of a semiconductor laser and a ring cavity. The ring cavity includes a wavelength division multiplexer, a thulium-doped fiber, an isolator, a fiber coupler, a polarizer, a Mach-Zehnder interferometric filter, a black phosphorus saturable absorber, and a polarization controller.

[0006] The semiconductor laser serves as a pump source for outputting pump light.

[0007] The pump light generated by the semiconductor laser is coupled into the thulium-doped fiber via the wavelength division multiplexer, in the process, the pump light energy is effectively absorbed and converted into signal light; the signal light enters the fiber coupler after the isolator, the fiber coupler divides the signal light into two ways: one way of signal light continues to circulate in the ring cavity, participating in laser oscillation; the other way as a laser output end is connected to the detection equipment for real-time monitoring of the signal state in the ring cavity; the signal light circulating in the ring cavity passes through the polarizer, and its polarization state is controlled and adjusted, and then enters the Mach-Zehnder interference filter for processing; the processed signal light enters the black phosphorus saturable absorber for modulation; the modulated signal light is further adjusted by the polarization controller and returns to the signal port of the wavelength division multiplexer, thereby completing the entire in-cavity circulation.

[0008] In the circulation process, pump light is continuously injected into the ring cavity, and the signal light is amplified in the thulium-doped fiber, and finally forms stable multi-wavelength laser output through the modulation of the Mach-Zehnder interference filter and the black phosphorus saturable absorber.

[0009] Preferably, the exit end of the semiconductor laser is connected to the pump port of the wavelength division multiplexer through a single-mode optical fiber; the exit end of the wavelength division multiplexer is connected to the entrance end of the thulium-doped fiber through a single-mode optical fiber, and the exit end of the thulium-doped fiber is connected to the entrance end of the isolator through a single-mode optical fiber; the exit end of the isolator is connected to the entrance end of the fiber coupler through a single-mode optical fiber, and the first exit end of the fiber coupler is connected to the entrance end of the polarizer through a single-mode optical fiber; the exit end of the polarizer is connected to the entrance end of the Mach-Zehnder interference filter, and the exit end of the Mach-Zehnder interference filter is connected to the entrance end of the black phosphorus saturable absorber through a single-mode optical fiber; the exit end of the black phosphorus saturable absorber is connected to the entrance end of the polarization controller through a single-mode optical fiber, and the exit end of the polarization controller is finally connected to the signal port of the wavelength division multiplexer through a single-mode optical fiber, thereby completing the closed-loop connection of the entire optical path.

[0010] Preferably, the semiconductor laser is used to output continuous pump light with a center wavelength of 1570nm.

[0011] Preferably, the wavelength division multiplexer is a 1570 / 1950nm wavelength division multiplexer.

[0012] Preferably, the isolator is used to ensure one-way transmission of optical signals in the ring cavity, preventing interference and instability caused by optical feedback.

[0013] Preferably, the fiber coupler is a 50:50 fiber coupler.

[0014] Preferably, the Mach-Zehnder interference filter is formed by connecting a first fiber coupler and a second fiber coupler in series, forming two interference arms.

[0015] Preferably, the free spectral range of the Mach-Zehnder interferometric filter is 3nm.

[0016] Preferably, the signal light circulating in the cavity is adjusted in polarization state by a polarizer before entering the Mach-Zehnder interferometric filter for processing, specifically including:

[0017] After the signal light circulating in the cavity is adjusted in polarization state by a polarizer, it enters the Mach-Zehnder interferometric filter. The signal light adjusted in polarization state by the polarizer is split into two paths at the first fiber coupler, transmitted through different interference arms respectively, recombined and interfered at the second fiber coupler, to produce a comb filter effect, realizing the enhancement or suppression processing of specific wavelength optical signals.

[0018] Preferably, the transmission characteristics of the Mach-Zehnder interferometric filter are represented as:

[0019]

[0020] Where T is the transmittance, n eff represents the effective refractive index of the ordinary optical fiber, ΔL represents the physical length difference of the two interference arms, and λ represents the working wavelength; in addition, the free spectral range is an important parameter for describing the periodicity of the interference curve of the Mach-Zehnder interferometric filter, which represents the wavelength interval between adjacent two interference peaks or valleys, and the calculation formula of the free spectral range is:

[0021]

[0022] In the formula, Δλ represents the free spectral range.

[0023] From the above technical solutions, the present application has the following beneficial effects:

[0024] (1) Multi-wavelength stable output and wide spectrum tunability: By integrating the Mach-Zehnder interferometric filter and the black phosphorus saturable absorber, the present application effectively overcomes the gain competition and mode competition, realizes stable mode-locked laser output from single wavelength to multi-wavelength (four wavelengths), and exhibits a tunable spectral range of up to 55.8nm, meeting the needs of wavelength diversity in different application scenarios.

[0025] (2) Enhanced mode-locked stability: The combination of hybrid cavity mode-locked technology and Mach-Zehnder interferometric filter significantly improves the mode-locked stability of the laser, ensuring the high quality and reliability of the laser output, and providing a stable laser source for scientific research and industrial applications. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the drawings needed in the embodiments will be briefly described below. The features and advantages of the present application can be more clearly understood by referring to the drawings. The drawings are schematic and should not be construed as any limitation to the present application. For those skilled in the art, other drawings can be obtained without creative effort based on these drawings. Among them:

[0027] Figure 1 A structure schematic diagram of a ring cavity multi-wavelength thulium-doped fiber laser based on a Mach-Zehnder interferometer provided in the embodiments;

[0028] Figure 2 A design schematic diagram of a Mach-Zehnder interferometric filter in the embodiments, wherein (a) is a structure diagram of the Mach-Zehnder interferometric filter; and (b) is an interference performance map;

[0029] Figure 3 An output characteristic schematic diagram of the laser in the embodiments, wherein (a) is a spectrum; (b) is a fundamental frequency spectrum, (c) is a self-correlation curve, and (d) is a tunable spectrum of a single-wavelength thulium-doped fiber laser;

[0030] Figure 4 Wavelength and spectrum evolution diagrams of the laser under different pump powers in the embodiments, wherein (a) is a wavelength evolution diagram under different pump powers, and (b) is a spectrum evolution diagram of the laser under different pump powers.

[0031] The description of the drawings is as follows: 1, semiconductor laser; 2, wavelength division multiplexer; 200, pump port; 201, signal port; 3, thulium-doped fiber; 4, isolator; 5, fiber coupler; 500, first exit end; 501, second exit end; 6, polarizer; 7, Mach-Zehnder interferometric filter; 71, first fiber coupler; 72, second fiber coupler; 8, black phosphorus saturable absorber; 9, polarization controller. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below by combining the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort fall within the scope of protection of the present application.

[0033] Embodiment one

[0034] In order to solve the problems of obvious mode competition and poor mode-locked stability in the multi-wavelength thulium-doped fiber laser in the prior art. As shown inFigure 1 As shown, the embodiment of the present application proposes a kind of ring cavity multi-wavelength thulium-doped fiber laser based on Mach-Zehnder interferometer, the laser is composed of semiconductor laser 1 and ring cavity, and the ring cavity includes wavelength division multiplexer (wavelength division multiplexer, WDM) 2, Tm-doped fiber (Tm-doped fiber, TDF) 3, isolator (Isolator, ISO) 4, optical coupler (optical coupler, OC) 5, polarizer (Polarizer) 6, Mach-Zehnder interference filter 7, black phosphorus saturable absorber (Black Phosphorus Saturable Absorber, BP-SA) 8, polarization controller (Polarization Controller, PC) 9.

[0035] In the embodiment of the present application, semiconductor laser 1 is used as pump source to output pump light.

[0036] The pump light generated by semiconductor laser 1 is coupled into Tm-doped fiber 3 via wavelength division multiplexer 2, and in this process, the pump light energy is effectively absorbed and converted into (near 1900nm) signal light. After passing through isolator 4, the signal light enters optical coupler 5, which divides the signal light into two paths: one path of signal light continues to circulate in the ring cavity and participates in laser oscillation; the other path is connected to the detection device as a laser output end, for real-time monitoring of the signal state in the ring cavity. The signal light circulating in the ring cavity passes through polarizer 6, and its polarization state is controlled and adjusted, and then enters Mach-Zehnder interference filter 7 for processing. The processed signal light enters black phosphorus saturable absorber 8 to achieve modulation. The modulated signal light is further adjusted by polarization controller 9 and then returns to the signal port 201 of wavelength division multiplexer 2, thereby completing the entire in-cavity circulation.

[0037] In the circulation process, pump light is continuously injected into the ring cavity, and the signal light is amplified in Tm-doped fiber 3 and is modulated by Mach-Zehnder interference filter 7 and black phosphorus saturable absorber 8, and finally forms stable multi-wavelength laser output.

[0038] Specifically, in the embodiment of the present application, the wavelength division multiplexer 2 is used to couple the pump light and the signal light, so that the pump light can enter the thulium-doped fiber 3, while the signal light is allowed to circulate in the ring cavity; the isolator 4 is used to ensure the one-way transmission of the optical signal in the ring cavity, preventing interference and instability caused by optical feedback; the polarizer 6 is used to preliminarily adjust the polarization state of the optical signal; the Mach-Zehnder interferometric filter 7 is used to produce a comb filter effect, realizing the enhancement or suppression of the optical signal of a specific wavelength; the black phosphorus saturable absorber 8 acts as a modulation element, which modulates the optical signal by using the nonlinear absorption characteristics of black phosphorus, stabilizes the laser output, and realizes mode locking or multi-wavelength operation; the polarization controller 9 is used to finely adjust the polarization state of the optical signal in the cavity to match the optimal working conditions of the laser.

[0039] As an optional specific embodiment, the outgoing end of the semiconductor laser 1 is connected to the pump port 200 of the wavelength division multiplexer 2 through a single-mode optical fiber; the outgoing end of the wavelength division multiplexer 2 is connected to the incoming end of the thulium-doped fiber 3 through a single-mode optical fiber, and the outgoing end of the thulium-doped fiber 3 is connected to the incoming end of the isolator 4 through a single-mode optical fiber; the outgoing end of the isolator 4 is connected to the incoming end of the fiber coupler 5 through a single-mode optical fiber, and the first outgoing end 500 of the fiber coupler 5 is connected to the incoming end of the polarizer 6 through a single-mode optical fiber; the outgoing end of the polarizer 6 is connected to the incoming end of the Mach-Zehnder interferometric filter 7, and the outgoing end of the Mach-Zehnder interferometric filter 7 is connected to the incoming end of the black phosphorus saturable absorber 8 through a single-mode optical fiber; the outgoing end of the black phosphorus saturable absorber 8 is connected to the incoming end of the polarization controller 9 through a single-mode optical fiber, and the outgoing end of the polarization controller 9 is finally connected to the signal port 201 of the wavelength division multiplexer 2 through a single-mode optical fiber, thereby completing the closed-loop connection of the entire optical path. In addition, the second outgoing end 501 of the fiber coupler 5 serves as the output end of the laser and is connected to a detection device to monitor the state of the signal in the ring cavity in real time.

[0040] As an optional specific embodiment, as shown in Figure 2 The Mach-Zehnder interferometric filter 7 is formed by connecting a first fiber coupler (3dB fiber coupler) 71 and a second fiber coupler (3dB fiber coupler) 72 in series, forming two interference arms.

[0041] As an optional specific embodiment, after the signal light circulating in the cavity is adjusted by the polarizer 6, it enters the Mach-Zehnder interferometric filter 7 for processing, which specifically includes:

[0042] The in-cavity circulating signal light is adjusted in polarization state by the polarizer 6, and then enters the Mach-Zehnder interference filter 7. The signal light adjusted in polarization state by the polarizer 6 is divided into two paths at the first fiber coupler 71, and then recombined and interfered at the second fiber coupler 72 after being transmitted through different interference arms, so as to realize the enhancement or suppression processing of the specific wavelength light signal.

[0043] Further, the transmission characteristic of the Mach-Zehnder interference filter is represented as:

[0044]

[0045] Wherein, T is the transmittance, n eff represents the effective refractive index of the common optical fiber, ΔL represents the physical length difference of the two interference arms, and λ represents the working wavelength. In addition, the free spectral range is an important parameter for describing the periodicity of the interference curve of the Mach-Zehnder interference filter, which represents the wavelength interval between the adjacent two interference peaks or valleys. The calculation formula of the free spectral range is:

[0046]

[0047] In the formula, Δλ represents the free spectral range (FSR).

[0048] As an optional embodiment, the laser of the present application comprises a 1570nm semiconductor laser 1, a 1570 / 1950nm wavelength division multiplexer 2, a 1.8-meter-long thulium-doped fiber 3, an isolator 4, a 50:50 fiber coupler 5, a polarizer 6, a Mach-Zehnder interference filter 7 with a free spectral range of 3nm, a black phosphorus saturable absorber 8, and a polarization controller 9. The total length of the interference arms of the Mach-Zehnder interference filter 7 is about 60cm, and the total length of the ring cavity is 14.78m.

[0049] In order to further illustrate the advantages of the present application, the following specific experiments are described.

[0050] During the experiment, the Mach-Zehnder interference filter 7 shown in Figure 2 is carefully prepared. The filter is composed of two 3dB fiber couplers, and the two interference arms are connected by fiber fusion technology, and the lengths of the two interference arms are made as equal as possible. In order to overcome the wavelength drift problem of the Mach-Zehnder interference filter 7 at room temperature, the two interference arms are wound and bound into one arm during preparation, so as to reduce the wavelength drift caused by the influence of the environment on the different arms, thereby stabilizing the performance of the filter.

[0051] After the filter was prepared, performance test was carried out. Since the current wide spectrum light source does not cover the spectral region of 1.8 μm and longer, the performance at 1.5 μm wavelength was preliminarily tested. Figure 2 As shown in (b), through laser spectrum measurement, the free spectral range of the Mach-Zehnder interferometer-based filter 7 selected in the experiment is 3 nm, and the average extinction ratio at the resonance wavelength is about 12 dB.

[0052] When the pump power is 327 mW, the output characteristics of the Thulium-doped fiber laser based on the Mach-Zehnder interferometer and the ring cavity in the fundamental frequency state are shown in (a). Figure 3 Figure 3 (a) shows that the spectrum has a 3dB bandwidth of about 0.4 nm and a central wavelength of 1875.6 nm. Figure 3 (b) is a spectrum diagram of the laser output, the pulse repetition frequency is 13.53 MHz, and the signal-to-noise ratio SNR is greater than 56 dB when the resolution bandwidth is 10 kHz, indicating that the laser designed in the application has good mode-locked performance. The small graph inserted is a stable single pulse sequence with a time interval of 47.4 ns. Figure 3 (c) presents the mode-locked pulse width measured by a commercial autocorrelator, and the output pulse width is 13.17 ps through hyperbolic secant sech 2 fitting of experimental data. By adjusting the polarization controller 9, the linear transmission spectrum of the birefringent fiber has the characteristic of comb filtering in the spectrum, the birefringent filtering period is represented by the wavelength at which the adjacent two transmission peaks are located, and the change of Δn affects the size of the phase difference, thereby changing the birefringent filtering period and the transmission central wavelength. In the experiment, adjusting the polarization controller 9 can change the Δn of the fiber, so that the filtering wavelength in the laser ring cavity moves, causing the wavelength tunable experimental result, and the tunable range of the laser is about 55.8 nm Figure 3 (d).

[0053] The wavelength evolution of the Thulium-doped fiber laser based on the Mach-Zehnder interferometer and the ring cavity with the increase of the pump power is shown in (a). Figure 4 As the Mach-Zehnder interferometer-based filter 7 provides comb filtering effect, when the pump power is increased, sufficient gain can be provided in multiple transmission windows at the same time, so as to realize multi-wavelength pulse mode locking. It can be observed that when the power is 400 mW, 421 mW and 439 mW, respectively, there are 2, 3 and 4 peaks, respectively, to obtain two-wavelength, three-wavelength and four-wavelength mode-locked lasers Figure 4 (a). Figure 4 ​(b) is the spectrum variation graph of the laser with the increase of pump power, and the two frequency intervals are 276Hz when the dual-wavelength mode locking. These multi-wavelength mode-locked lasers have wide application prospects in many fields. For example, in the communication system, they can be used as multi-wavelength light sources to improve the transmission capacity and spectral efficiency; in the field of spectrum analysis, sensing and measurement, multi-wavelength lasers can provide more abundant spectral information and higher measurement accuracy; and in the field of scientific research, they can be used to explore frontier topics such as nonlinear optical phenomena and ultrafast optical signal processing. In summary, the laser designed in the present application provides strong technical support and driving force for the development of many fields.

[0054] In summary, the multi-wavelength thulium-doped fiber laser based on a Mach-Zehnder interferometer ring cavity designed in the present application significantly improves the mode competition and mode locking stability problems faced by traditional multi-wavelength thulium-doped fiber lasers by introducing a black phosphorus saturable absorber 8 and a Mach-Zehnder interferometric filter 7. The all-fiber structure ensures high integration and stability, while the unique hybrid cavity mode locking method effectively widens the spectral tuning range to 55.8nm and supports flexible switching from single-wavelength to four-wavelength. This innovative design not only improves the stability and wavelength diversity of the laser output, but also provides strong technical support for realizing high-performance, multi-purpose fiber laser systems.

[0055] Obviously, the above embodiments are only examples for the sake of clarity, and are not limiting of the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A ring cavity multiwavelength thulium-doped fiber laser based on Mach-Zehnder interferometer, characterized in that, The laser is composed of a semiconductor laser and a ring cavity, and the ring cavity comprises a wavelength division multiplexer, a thulium-doped fiber, an isolator, a fiber coupler, a polarizer, a Mach-Zehnder interference filter, a black phosphorus saturable absorber and a polarization controller. The semiconductor laser serves as a pump source for outputting pump light. The pump light generated by the semiconductor laser is coupled into the thulium-doped fiber via the wavelength division multiplexer, and in this process, the pump light energy is effectively absorbed and converted into signal light; the signal light enters the fiber coupler after passing through the isolator, and the fiber coupler divides the signal light into two paths: one path of the signal light continues to circulate in the ring cavity and participate in laser oscillation; the other path is connected to a detection device as a laser output end for real-time monitoring of the signal state in the ring cavity; the signal light circulating in the ring cavity passes through the polarizer and its polarization state is controlled and adjusted, and then enters the Mach-Zehnder interference filter for processing; the processed signal light enters the black phosphorus saturable absorber to achieve modulation; the modulated signal light is further adjusted by the polarization controller and then returns to the signal port of the wavelength division multiplexer, thereby completing the entire in-cavity circulation. In the circulation process, pump light is continuously injected into the ring cavity, the signal light is amplified in the thulium-doped fiber, and through the modulation of the Mach-Zehnder interference filter and the black phosphorus saturable absorber, stable multi-wavelength laser output is finally formed; the free spectral range of the Mach-Zehnder interference filter is 3nm; the transmission characteristic of the Mach-Zehnder interference filter is represented as: where T is the transmittance, n eff where n eff represents the effective refractive index of the common fiber, AL represents the physical length difference of the two interference arms, and λ represents the operating wavelength; in addition, the free spectral range is an important parameter for describing the periodicity of the interference curve of the Mach-Zehnder interference filter, which represents the wavelength interval between two adjacent interference peaks or valleys, and the calculation formula of the free spectral range is: In the formula, Δλ represents the free spectral range.

2. The Mach-Zehnder interferometer based ring cavity multiwavelength thulium doped fiber laser of claim 1, wherein, The exit end of the semiconductor laser is connected to the pump port of the wavelength division multiplexer through a single-mode optical fiber; the exit end of the wavelength division multiplexer is connected to the entrance end of the thulium-doped fiber through a single-mode optical fiber, and the exit end of the thulium-doped fiber is connected to the entrance end of the isolator through a single-mode optical fiber; the exit end of the isolator is connected to the entrance end of the fiber coupler through a single-mode optical fiber, and the first exit end of the fiber coupler is connected to the entrance end of the polarizer through a single-mode optical fiber; the exit end of the polarizer is connected to the entrance end of the Mach-Zehnder interference filter, and the exit end of the Mach-Zehnder interference filter is connected to the entrance end of the black phosphorus saturable absorber through a single-mode optical fiber; the exit end of the black phosphorus saturable absorber is connected to the entrance end of the polarization controller through a single-mode optical fiber, and the exit end of the polarization controller is finally connected to the signal port of the wavelength division multiplexer through a single-mode optical fiber, thereby completing the closed-loop connection of the entire optical path.

3. The Mach-Zehnder interferometer based ring cavity multiwavelength thulium doped fiber laser of claim 1, wherein, The semiconductor laser is used to output continuous pump light with a center wavelength of 1570nm.

4. The Mach-Zehnder interferometer based ring cavity multiwavelength thulium doped fiber laser of claim 1, wherein, The wavelength division multiplexer is a 1570 / 1950nm wavelength division multiplexer.

5. The Mach-Zehnder interferometer based ring cavity multiwavelength thulium doped fiber laser of claim 1, wherein, The isolator is used to ensure one-way transmission of optical signals in the ring cavity and prevent interference and instability caused by optical feedback.

6. The Mach-Zehnder interferometer based ring cavity multiwavelength thulium doped fiber laser according to claim 1, wherein, The fiber coupler is a 50:50 fiber coupler.

7. The Mach-Zehnder interferometer based ring cavity multiwavelength thulium doped fiber laser according to claim 1, wherein, The Mach-Zehnder interference filter is formed by connecting a first fiber coupler and a second fiber coupler in series to form two interference arms.

8. The Mach-Zehnder interferometer based ring cavity multiwavelength thulium doped fiber laser according to claim 1, characterized in that, After the signal light circulating in the cavity passes through the polarizer for polarization state adjustment, it enters the Mach-Zehnder interference filter for processing, which specifically includes: The intracavity circulating signal light passes through a polarizer to adjust the polarization state, and then enters a Mach-Zehnder interference filter. The signal light whose polarization state is adjusted by the polarizer is divided into two paths at a first fiber coupler, and then transmitted through different interference arms. After recombination at a second fiber coupler, the signal light produces a comb filter effect and realizes enhancement or suppression processing of specific wavelength optical signals.

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