Multi-wavelength random fiber laser based on four-port circulator and Brillouin-Rayleigh scattering

Abstract

The utility model belongs to the technical field of optical fiber lasers, and relates to a multi-wavelength random optical fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering, which is a closed-loop random optical fiber laser and comprises the four-port circulator, a seed laser is connected with the first port of the four-port circulator, and a seed laser is connected with the second port of the four-port circulator. The second port is connected with the Brillouin gain optical fiber, the third port is connected with the random Rayleigh scattering optical fiber, and the fourth port is connected with the optical fiber coupler; an erbium-doped fiber and a wavelength division multiplexer are connected between the Brillouin gain fiber and the fiber coupler, and a pump light port of the wavelength division multiplexer is connected with an output port of the 980nm laser. According to the utility model, the Brillouin gain optical fiber is subjected to Brillouin scattering, and the Rayleigh scattering of the random Rayleigh scattering optical fiber and the gain amplification of the erbium-doped optical fiber are combined, so that efficient and stable multi-wavelength output is realized, the number of output wavelengths is adjustable, the stability is high, and the device is suitable for a high-precision optical fiber sensing and dense wavelength division multiplexing system.

Description

Technical Field

[0001] This invention belongs to the field of fiber laser technology and relates to a multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering. Specifically, it relates to a closed-loop random laser based on a four-port circulator, a seed laser, a long-distance Brillouin gain fiber, a random Rayleigh scattering fiber, and an erbium-doped fiber. It achieves efficient and stable random laser output through the synergistic effect of stimulated Brillouin scattering and random Rayleigh scattering. Background Technology

[0002] Random fiber lasers, due to their advantages such as no fixed cavity structure, low coherence, and simple device design, have important applications in fiber optic sensing, communication, and spectral analysis. In 2010, Turitsyn et al. from Aston University in the UK...

[0003]

Turitsyn SK, Babin SA, El-Taher AE, et al. Random distributed feedback fiber laser[J]. Nature photonics, 2010, 4(4): 231-235.

[0004] In recent years, stimulated Brillouin scattering (SBS) has been introduced into random laser systems due to its high gain characteristics. Combined with random Rayleigh scattering, it can significantly enhance the laser conversion efficiency and expand the output wavelength range. In the previous literature [Pang M, Xie S, Bao X, et al. Rayleigh scattering-assisted narrow linewidth Brillouin lasing in cascaded fiber. Optics letters, 2012, 37(15): 3129-3131.], a narrow linewidth random laser output of 3.4 kHz was achieved by using three different spliced ​​fibers, with the middle high-Brillouin gain fiber amplifying the Stokes light and the two side fibers enhancing Rayleigh scattering. In the previous patent [2021, Guangdong University of Technology, A low-noise Brillouin random fiber laser, CN113097845A], a laser structure was proposed that uses highly germanium-doped fiber to generate Brillouin scattered light and uses femtosecond laser to write random gratings as random feedback, which shortens the cavity length of the Brillouin random fiber laser by more than three orders of magnitude. In the prior literature [Guo T, Zhang A, Pan H, et al. Tunable multi-wavelength SBS Q-switched random fiber laser based on SMF[J]. Applied Physics B, 2022, 128(5): 99.], a semi-open cavity structure tunable multi-wavelength stimulated Brillouin scattering Q-switched random fiber laser was proposed, which can achieve 1-18 order laser output by adjusting the pump power and the tunable laser source power. The prior literature [Pang Y, Ma S, Zhao X, et al. Single-longitudinal-mode short-cavity Brillouin random fiber laser via frequency auto-tracking with unpumped-EDF Sagnac loop[J].Infrared Physics & Technology, 2022, 127: 104461.] proposed using an unpumped erbium-doped fiber Sagnac loop as a filter structure, combining Brillouin gain in nonlinear fiber and Rayleigh scattering feedback in single-mode fiber to obtain narrow-linewidth random laser output.The prior literature [Xu L, Wang Y, Dai S, et al. Single-longitudinal-mode Brillouin random fiber laser with high linewidth-compression ratio and laser efficiency based on distributed intrinsic feedback mechanism[J]. Optics & Laser Technology, 2022, 156: 108471.] proposed to obtain random laser output with high linewidth compression ratio and conversion efficiency by utilizing the distributed intrinsic feedback mechanism structure of enhanced Rayleigh scattering fiber and the Brillouin gain of small core fiber.

[0005] In the aforementioned prior document, the random laser cavity contains two three-port circulators. One circulator injects seed light into the Brillouin gain fiber, and the other circulator introduces the reverse stimulated Brillouin scattering light into the random Rayleigh scattering fiber. The numerous optical components in the optical path increase the system's complexity and introduce uncontrollable factors that degrade the laser beam output performance and quality. Utility Model Content

[0006] The present invention aims to provide a random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering mechanism. The purpose is to use a seed laser to excite Brillouin scattering, and combine random Rayleigh scattering of the fiber with the gain amplification of the erbium-doped fiber amplifier to achieve highly stable random Brillouin laser output.

[0007] The technical solution of this utility model is: a multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering, which is a closed-loop random fiber laser, including a four-port circulator. The first port of the four-port circulator is connected to a seed laser, the second port is connected to a Brillouin gain fiber, the third port is connected to a random Rayleigh scattering fiber, and the fourth port is connected to a fiber coupler. An erbium-doped fiber and a wavelength division multiplexer are connected between the Brillouin gain fiber and the fiber coupler. The pump port of the wavelength division multiplexer is connected to the output port of a 980nm laser.

[0008] In the above technical solution, the center wavelength of the seed laser is in the 1550nm band, which serves as the seed light and provides the initial pump light signal.

[0009] In the above technical solution, the four-port circulator controls the unidirectional transmission of optical signals (1→2→3→4) to ensure the stability of the optical path within the annular cavity.

[0010] In the above technical solution, the second port of the four-port circulator is connected to the first port of the Brillouin gain fiber, the second port of the Brillouin gain fiber is connected to the first port of the erbium-doped fiber, the second port of the erbium-doped fiber is connected to the common port of the wavelength division multiplexer, and the Brillouin gain fiber is used to generate stimulated Brillouin scattering to generate back-stokes light.

[0011] In the above technical solution, the fiber optic coupler is a 1:9 fiber optic coupler, which distributes the optical signal proportionally (10% output, 90% feedback to the optical path), of which 10% provides laser output. Specifically, the fiber optic coupler has an input port, a 90% main output port, and a 10% output and monitoring port.

[0012] In the above technical solution, the pump optical port of the wavelength division multiplexer is connected to the first port of the 980nm laser, and the erbium-doped fiber (EDF) is driven by the 980nm pump laser to provide gain amplification of the intracavity oscillating light.

[0013] In the above technical solution, the 980nm laser is a pump source.

[0014] In the above technical solution, the signal optical port of the wavelength division multiplexer is connected to the 90% main output port of the fiber coupler. The wavelength division multiplexer (WDM) is used to couple 980nm pump light and 1550nm signal light.

[0015] In the above technical solution, the input port of the fiber optic coupler is connected to the fourth port of the four-port circulator.

[0016] In the above technical solution, the Rayleigh scattering fiber provides random Rayleigh scattering to enhance distributed feedback. The other end of the random Rayleigh scattering fiber is cut at an 8° angle to eliminate the influence of end-face reflection. The 8° angle fiber end face suppresses fiber end-face reflection to ensure the effect of random Rayleigh scattering.

[0017] In the above technical solution, the third port of the four-port circulator is connected to the first port of the random Rayleigh scattering fiber, and the second port of the random Rayleigh scattering fiber is connected to the 8° angle fiber end face.

[0018] The technical advantages of this invention are as follows: This invention achieves efficient and stable multi-wavelength output by combining Brillouin scattering of Brillouin gain fiber with Rayleigh scattering of random Rayleigh scattering fiber and gain amplification of erbium-doped fiber. The number of output wavelengths is adjustable and the stability is high, making it suitable for high-precision fiber optic sensing and dense wavelength division multiplexing systems. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering according to this invention.

[0020] Figure 2 This is the output spectrum of the Brillouin random fiber laser of this invention; where: (left: seed light; right: first-order and second-order random Brillouin lasers);

[0021] Figure 3 This refers to the conversion efficiency of the Brillouin random fiber laser of this invention.

[0022] Figure 4 The output stability of the Brillouin random fiber laser of this invention is: (a) peak stability; (b) wavelength stability.

[0023] Wherein: 1-Seed laser; 11-Seed laser first port; 2-Four-port circulator; 21-Four-port circulator first port; 22-Four-port circulator second port; 23-Four-port circulator third port; 24-Four-port circulator fourth port; 3-Brillouin gain fiber; 31-Brillouin gain fiber first port; 32-Brillouin gain fiber second port; 4-Erbium-doped fiber; 41-Erbium-doped fiber first port; 42-Erbium-doped fiber second port; 5-Wavelength division multiplexer; 51-Wavelength division multiplexer common port. ; 52 - Wavelength division multiplexer pump optical port; 53 - Wavelength division multiplexer signal optical port; 6 - 980nm laser; 61 - 980nm laser first port; 7 - Fiber coupler; 71 - Fiber coupler 90% main output port; 72 - Fiber coupler 10% output / monitoring port; 73 - Fiber coupler input port; 8 - Random Rayleigh scattering fiber; 81 - Random Rayleigh scattering fiber first port; 82 - Random Rayleigh scattering fiber second port; 9 - 8° angle fiber end face; 91 - 8° angle fiber end face first port. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0025] Example 1;

[0026] like Figure 1As shown, a multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering includes a seed laser 1, a four-port circulator 2, a Brillouin gain fiber 3, an erbium-doped fiber 4, a wavelength division multiplexer 5, a 980nm laser 6, an fiber coupler 7, a random Rayleigh scattering fiber 8, and an 8° angle fiber end face 9. The first port 11 of the seed laser 1 is connected to the first port 21 of the four-port circulator 2. The second port 22 of the four-port circulator 2 is connected to the first port 31 of the Brillouin gain fiber 3. The second port 32 of the Brillouin gain fiber 3 is connected to the first port 41 of the erbium-doped fiber 4. The second port 42 of the erbium-doped fiber 4 is connected to the common port 51 of the wavelength division multiplexer 5. The pump port 52 of the wavelength division multiplexer 5 is connected to the output of the 980nm laser 6. The wavelength division multiplexer pump optical port 61 is connected to the wavelength division multiplexer signal optical port 53 of the wavelength division multiplexer 5, which is connected to the fiber coupler 90% main output port 71 of the fiber coupler 7. The fiber coupler input port 73 of the fiber coupler 7 is connected to the fourth port 24 of the four-port circulator 2. The fourth port 23 of the four-port circulator 2 is connected to the first port 81 of the random Rayleigh scattering fiber 8. The second port 82 of the random Rayleigh scattering fiber 8 is connected to the first port 91 of the 8° angle fiber end face 9.

[0027] like Figure 2 As shown, Figure 2 These are the output spectra of the seed laser and the random Brillouin fiber laser. The center wavelength of the seed laser is 1550.204 nm; the two output wavelengths of the random Brillouin laser are 1550.288 nm and 1550.376 nm, respectively, with wavelength intervals of 0.084 nm and 0.172 nm from the seed laser, corresponding to the first-order and second-order Brillouin lasers, respectively.

[0028] like Figure 3 As shown, Figure 3 This is the conversion efficiency of the Brillouin random laser. The output power of the 8° angle fiber end face increases with the increase of the seed laser output power, and the conversion efficiency reaches 38.9%.

[0029] like Figure 4 As shown, Figure 4 It is the output stability of a random laser over 1 hour, including the peak intensity stability at each wavelength and the center wavelength stability.

[0030] In this embodiment, the multi-wavelength random fiber laser is a semi-open cavity Brillouin random fiber laser. Its cavity contains a Brillouin gain fiber 3, a random Rayleigh scattering fiber 8, a section of erbium-doped fiber 4, a four-port circulator 2, a wavelength division multiplexer 5, and a fiber coupler 7. The four-port circulator controls unidirectional optical signal transmission (1→2→3→4). The seed laser acts as a seed source, providing the initial pump signal. When the output power of the seed laser exceeds the stimulated Brillouin scattering threshold of the Brillouin gain fiber, the fiber is excited to generate stimulated Brillouin scattering, and the subsequent Stokes light propagates within the cavity. A 980nm laser serves as the pump source and is connected to the erbium-doped fiber via the wavelength division multiplexer, forming an erbium-doped fiber amplifier. The random Rayleigh scattering fiber provides both random Rayleigh scattering and stimulated Brillouin scattering; this fiber generates random Rayleigh scattering of the incident Stokes light; if the light intensity in the Brillouin gain fiber exceeds its stimulated Brillouin scattering threshold, higher-order Brillouin light is excited. The reverse Rayleigh scattered light enters the four-port circulator via the three-port port and then the input of the 1:9 coupler, thus forming a closed loop and generating oscillation. Finally, the random laser is output to the outside through the 10% port of the 1:9 coupler. Simultaneously, the forward Rayleigh scattering in the random Rayleigh scattering fiber can also be output through the 8° angle fiber endface.

[0031] This embodiment uses a four-port circulator, which reduces the number of optical components inside the laser cavity and simplifies the structure of the laser;

[0032] This embodiment combines a dual feedback mechanism of Brillouin scattering and Rayleigh scattering, which significantly improves laser output efficiency;

[0033] In this embodiment, random Rayleigh scattering in the optical fiber replaces the reflector as optical feedback to realize the oscillation of random optical signals; stimulated Brillouin scattering and erbium-doped fiber amplification work together to provide gain amplification within the laser cavity.

[0034] This embodiment utilizes an 8° angle fiber endface to suppress endface Fresnel reflection and reduce external noise interference.

[0035] This embodiment uses a 1:9 coupler to monitor laser output.

[0036] This embodiment uses an 8° angle fiber end face to measure the laser output light intensity, and then calculates the conversion efficiency of the random laser.

[0037] Example 2:

[0038] A multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering is disclosed. The seed laser 1 is a distributed feedback (DFB) semiconductor laser, the Brillouin gain fiber 3 is a 20km single-mode fiber, the random Rayleigh scattering fiber 8 is a 2km single-mode fiber, and the 8° angle fiber end face 9 is a fiber optic connector. The first port of the DFB semiconductor laser is connected to the first port 21 of the four-port circulator 2. The second port 22 of the four-port circulator 2 is connected to the first port of the 20km single-mode fiber. The second port of the 20km single-mode fiber is connected to the first port 41 of the erbium-doped fiber 4. The second port 42 of the erbium-doped fiber 4 is connected to the common port 51 of the wavelength division multiplexer 5. The pump port 52 of the wavelength division multiplexer 5 is connected to a 980nm laser. The output port (wavelength division multiplexer pump port 61) of optical device 6 is connected, the wavelength division multiplexer signal port 53 of wavelength division multiplexer 5 is connected to the fiber coupler 90% main output port 71 of fiber coupler 7, the fiber coupler input port 73 of fiber coupler 7 is connected to the fourth port 24 of four-port circulator 2, the third port 23 of four-port circulator 2 is connected to the first port 81 of 2km single-mode fiber, and the second port 82 of 2km single-mode fiber is connected to the first port of fiber optic connector.

[0039] In this embodiment, the multi-wavelength random fiber laser has a semi-open cavity structure, containing two single-mode fibers, one erbium-doped fiber, a four-port circulator, a wavelength division multiplexer (WDM), and a fiber coupler. The four-port circulator controls unidirectional optical signal transmission (1→2→3→4), and the DFB laser (distributed feedback laser, center wavelength 1550nm) serves as a seed source, providing the initial pump signal. A 20km long single-mode fiber is excited to generate Brillouin scattering, and the backscattered Stokes light oscillates within the cavity. A 980nm laser serves as the pump source and is connected to the erbium-doped fiber via the WDM to form an erbium-doped fiber amplifier. The 2km single-mode fiber provides random Rayleigh scattering and stimulated Brillouin scattering; when the light intensity exceeds a higher-order Brillouin threshold, higher-order Brillouin light is excited. Finally, the laser is output to the outside via the WDM.

[0040] This embodiment combines a dual feedback mechanism of Brillouin scattering and Rayleigh scattering, which significantly improves laser output efficiency and the number of wavelengths.

[0041] This embodiment utilizes random Rayleigh scattering and stimulated Brillouin scattering in single-mode fiber as optical feedback, replacing the reflector, to achieve oscillation amplification of random optical signals.

[0042] This embodiment utilizes APC patch cords to suppress Fresnel reflections at the fiber end face, thereby reducing external noise interference.

[0043] Example 3;

[0044] A multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering is disclosed. The seed laser 1 is a fiber laser (FL), the Brillouin gain fiber 3 is a 20km small-core fiber, and the random Rayleigh scattering fiber 8 is a 2km Rayleigh scattering enhancement fiber or a random fiber grating. The first port 11 of the fiber laser (FL) is connected to the first end 21 of the four-port circulator 2. The second port 22 of the four-port circulator 2 is connected to the first port of the 20km small-core fiber. The second port of the 20km small-core fiber is connected to the first port 41 of the erbium-doped fiber 4. The second port 42 of the erbium-doped fiber 4 is connected to the common port 51 of the wavelength division multiplexer 5. The pump port 52 of the wavelength division multiplexer 5 is connected to the output of a 980nm laser 6. The wavelength division multiplexer pump port 61 is connected to the wavelength division multiplexer signal port 53, which is connected to the fiber coupler 90% main output port 71 of the fiber coupler 7. The fiber coupler input port 73 of the fiber coupler 7 is connected to the fourth port 24 of the four-port circulator 2. The fourth port 23 of the four-port circulator 2 is connected to the first port of the 2Km Rayleigh scattering enhanced fiber or random fiber grating. The second port of the 2Km Rayleigh scattering enhanced fiber or random fiber grating is polished to an 8° tilt angle.

[0045] In this embodiment, the Brillouin gain coefficient of the small-core fiber is 3.61 × 10⁻⁶. -11 m / W, which is greater than the Brillouin gain coefficient of ordinary single-mode fiber (2.55 × 10⁻⁶). 11 m / W can further improve the conversion efficiency of random lasers.

[0046] In this embodiment, the Rayleigh scattering coefficient of the 2km Rayleigh scattering enhanced fiber is greater than that of a regular single-mode fiber; the Rayleigh scattering coefficient of the random fiber grating is much greater than that of the single-mode fiber, and a ~cm long random grating can be used to replace the Rayleigh scattering fiber to reduce the overall cavity length of the random laser.

[0047] In this embodiment, the multi-wavelength random fiber laser has a semi-open cavity structure, containing two fiber segments, one erbium-doped fiber segment, a four-port circulator, a wavelength division multiplexer, and a fiber coupler. The four-port circulator controls unidirectional optical signal transmission (1→2→3→4), and the fiber laser acts as a seed source, providing the initial pump signal. A 20km long small-core fiber is excited to generate Brillouin scattering, and the backscattered Stokes light oscillates within the cavity. A 980nm laser serves as the pump source and is connected to the erbium-doped fiber via the wavelength division multiplexer, forming an erbium-doped fiber amplifier. A 2km Rayleigh scattering enhancement fiber provides random Rayleigh scattering and stimulated Brillouin scattering; when the light intensity exceeds a higher-order Brillouin threshold, higher-order Brillouin light is excited; alternatively, a random fiber grating provides random Rayleigh scattering. Finally, the laser is output to the outside through the 10% port of the fiber coupler.

[0048] This embodiment combines a dual feedback mechanism of Brillouin scattering and Rayleigh scattering, which significantly improves laser output efficiency and the number of wavelengths.

[0049] This embodiment utilizes random Rayleigh scattering and stimulated Brillouin scattering in single-mode fiber as optical feedback, replacing the reflector, to achieve oscillation amplification of random optical signals.

[0050] In this embodiment, the end face of the random Rayleigh scattering fiber is directly ground and polished to an 8° angle.

[0051] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering, characterized in that: It is a closed-loop random fiber laser, including a four-port circulator (2). The first port of the four-port circulator (2) is connected to the seed laser (1), the second port is connected to the Brillouin gain fiber (3), the third port is connected to the random Rayleigh scattering fiber (8), and the fourth port is connected to the fiber coupler (7). An erbium-doped fiber (4) and a wavelength division multiplexer (5) are connected between the Brillouin gain fiber (3) and the fiber coupler (7). The pump port of the wavelength division multiplexer (5) is connected to the output port of the 980nm laser (6).

2. A multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering as described in claim 1, characterized in that: The seed laser (1) has a center wavelength in the 1550nm band and provides an initial pump light signal.

3. A multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering as described in claim 1, characterized in that: The four-port circulator (2) controls the unidirectional transmission of optical signals.

4. A multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering according to claim 1, characterized in that: The second port of the four-port circulator (2) is connected to the first port of the Brillouin gain fiber (3), the second port of the Brillouin gain fiber (3) is connected to the first port of the erbium-doped fiber (4), and the second port of the erbium-doped fiber (4) is connected to the common port of the wavelength division multiplexer (5).

5. A multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering according to claim 1, characterized in that: The fiber optic coupler (7) is a 1:9 fiber optic coupler with an input port, a 90% main output port, and a 10% output and monitoring port.

6. A multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering according to claim 5, characterized in that: The pump optical port of the wavelength division multiplexer (5) is connected to the first port of the 980nm laser (6), the signal optical port of the wavelength division multiplexer (5) is connected to the 90% main output port of the fiber coupler (7), and the input port of the fiber coupler (7) is connected to the fourth port of the four-port circulator (2).

7. A multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering according to claim 6, characterized in that: The 980nm laser (6) is a pump source.

8. A multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering according to claim 1, characterized in that: The other end of the random Rayleigh scattering fiber (8) is cut at an 8° angle.

9. A multi-wavelength random fiber laser based on a four-port circulator and Brillouin-Rayleigh scattering according to claim 8, characterized in that: The third port of the four-port circulator (2) is connected to the first port of the random Rayleigh scattering fiber (8), and the second port of the random Rayleigh scattering fiber (8) is connected to the 8° angle fiber end face (9).

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