Single-mode fiber laser capable of generating bright solitons and dark solitons and method

Abstract

The invention discloses a single-mode fiber laser capable of generating bright solitons and dark solitons and a method. The laser is characterized in that a wavelength division multiplexer is connected with a pumping source; one end of the Er-doped fiber is connected with the wavelength division multiplexer; the input end of the first polarization controller is connected with the other end of the erbium-doped fiber; the input end of the polarization analyzer is connected with the output end of the first polarization controller; the input end of the second polarization controller is connected with the output end of the polarization analyzer; the input port of the output coupler is connected with the output end of the second polarization controller, and the second output port of the output coupler is used as the output port of the fiber laser; the input end of the optical fiber isolator is connected with the first output port of the output coupler; the input end of the band-pass filter is connected with the output end of the optical fiber isolator, and the output end is connected with the wavelength division multiplexer. The method comprises the following steps: enabling the laser to respectively work in an equivalent saturated absorption region and an equivalent anti-saturated absorption region by utilizing a nonlinear polarization rotation mode locking technology, and respectively outputting bright solitons and dark solitons. The laser and the method can respectively generate bright soliton output and dark soliton output.

Description

Technical Field

[0001] The invention belongs to the technical fields of optical engineering, ultrafast nonlinear optical fiber dynamics and optical fiber lasers, and specifically relates to a single-mode optical fiber laser and a method for generating bright solitons and dark solitons. Background Art

[0002] Solitons are wave packets that can keep parameters unchanged when propagating in a medium. The nonlinear Schrödinger equation can be used to describe pulse propagation in fiber systems. Depending on the sign of the dispersion, bright solitons and dark solitons can be realized in single-mode fibers with anomalous dispersion and normal dispersion, respectively. Fiber lasers are dissipative systems because there are gains and losses in the laser cavity. Strictly speaking, the pulses generated in fiber lasers cannot be considered solitons. However, Kelly et al. demonstrated that even in high-gain fiber lasers, stable pulse evolution can be achieved as long as the soliton period is longer than the energy variation period. In an average sense, stable pulses generated in fiber lasers can be regarded as solitons. Pulse propagation in fiber lasers can be approximately described by the nonlinear Schrödinger equation even in the presence of large-period energy variations.

[0003] Research has found that fiber lasers operating in the anomalous dispersion region can generate bright solitons. Bright solitons refer to pulses with a zero background, while dark solitons refer to depressions on a certain background. When a fiber laser operates in the normal dispersion region, if appropriate spectral filtering can be applied, bright solitons called gain-dominated solitons or dissipative solitons can be obtained. Fiber lasers operating in the normal dispersion region can also support the generation of dark solitons. Therefore, it is possible to support the generation of both bright solitons and dark solitons at the same time through special design of fiber lasers operating in the normal dispersion region. The generation of bright solitons and dark solitons in a single fiber laser will help enhance the understanding of the pulse shaping mechanism of fiber lasers and has great application and research value. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a single-mode fiber laser and method that can generate bright solitons and dark solitons. The laser has a simple structure and low manufacturing cost, and can generate bright solitons and dark solitons as outputs respectively. The method has a simple implementation process and low implementation cost, and can output bright solitons and dark solitons respectively in the same single-mode fiber laser.

[0005] In order to achieve the above object, the present invention provides a single-mode fiber laser capable of generating bright solitons and dark solitons, the fiber laser comprising a pump source and a fiber ring cavity;

[0006] The fiber ring cavity comprises a wavelength division multiplexer, an erbium-doped fiber, a first polarization controller, an analyzer, a second polarization controller, an output coupler, a fiber isolator and a bandpass filter;

[0007] The pump port of the wavelength division multiplexer is connected to the output port of the pump source through a single-mode optical fiber;

[0008] The erbium-doped optical fiber is a single-mode optical fiber, one end of which is connected to the common port of the wavelength division multiplexer;

[0009] The input end of the first polarization controller is connected to the other end of the erbium-doped optical fiber;

[0010] The input end of the polarization analyzer is connected to the output end of the first polarization controller through a single-mode optical fiber;

[0011] The input end of the second polarization controller is connected to the output end of the analyzer through a single-mode optical fiber;

[0012] The energy input port of the output coupler is connected to the output end of the second polarization controller through a single-mode optical fiber, and the output ratio of the second energy output port of the output coupler is not higher than 25%, which serves as the output port of the optical fiber laser;

[0013] The input end of the optical fiber isolator is connected to the first energy output port of the output coupler through a single-mode optical fiber;

[0014] The input end of the bandpass filter is connected to the output end of the optical fiber isolator through a single-mode optical fiber, and the output end is connected to the signal port of the wavelength division multiplexer through a single-mode optical fiber;

[0015] The fiber laser is used to generate stable bright solitons and dark solitons, and the stable bright solitons and dark solitons are output through the second energy output port of the output coupler.

[0016] Preferably, the pump source is a semiconductor laser coupled by a normal dispersion optical fiber, with a central wavelength at 976nm or 1480nm, and an output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band, and an output power greater than 400mW.

[0017] Preferably, the operating wavelength of the wavelength division multiplexer is 980 / 1550 nm or 1480 / 1550 nm, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550 nm band.

[0018] As a preference, the erbium-doped optical fiber is an optical fiber with normal dispersion in the 1550nm band, an absorption coefficient of 80dB / m at 1530nm, and a length of 3 meters.

[0019] As a preference, the first polarization controller is a three-coil rotating polarization controller or a squeezed polarization controller, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band. The second polarization controller is a three-coil rotating polarization controller or a squeezed polarization controller, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band.

[0020] As a preference, the polarization analyzer is a fiber polarization analyzer, and its output pigtail is a single-mode fiber with normal dispersion in the 1550nm band.

[0021] Preferably, the output coupler is a fiber coupler with an energy ratio of 25:75, and its output pigtail is a single-mode fiber with normal dispersion in the 1550nm band.

[0022] As a preference, the optical fiber isolator adopts an isolator with a central wavelength of 1550nm, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band.

[0023] As a preference, the bandpass filter adopts an isolator with a central wavelength of 1550nm and a 3dB bandwidth of 7.5nm to 10.5nm, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band.

[0024] In the present invention, the pump light emitted by the pump source can be coupled into the resonant cavity by setting a wavelength division multiplexer. By setting an erbium-doped optical fiber on the output side of the common port of the wavelength division multiplexer, photons can be absorbed and emitted, and the optical signal can be amplified within the range of 1550nm, so that the loss of the optical signal during the transmission process can be effectively compensated, the transmission distance can be extended, and the signal quality can be improved. By setting a first polarization controller on the output side of the erbium-doped optical fiber, the polarization and loss of the optical pulse in the resonant cavity can be adjusted. By setting an analyzer on the output side of the first polarization controller, the polarization direction of the optical pulse passing through the analyzer can be limited. By setting a second polarization controller on the output side of the analyzer, the polarization and loss of the optical pulse in the resonant cavity can be further adjusted. At the same time, the first polarization controller, the analyzer, and the second polarization controller set in sequence can work together, and through nonlinear polarization rotation, the laser can be operated in the equivalent saturated absorption region and the equivalent anti-saturated absorption region respectively, thereby generating bright soliton and dark soliton outputs respectively. By setting a fiber isolator, the unidirectional operation of the laser can be limited. The laser has a simple structure and low manufacturing cost, and can generate bright soliton and dark soliton outputs respectively.

[0025] The present invention also provides a method for generating bright solitons and dark solitons, using a single-mode fiber laser that can generate bright solitons and dark solitons, comprising the following steps:

[0026] Step 1: Use a pump source to provide continuous pump light, and couple the continuous pump light into the fiber laser through a wavelength division multiplexer;

[0027] Step 2: Utilize erbium-doped fiber to absorb continuous pump light and stimulate radiation of long-wave gain pulses, which oscillate in the fiber laser cavity;

[0028] Step three: through the joint action of the first polarization controller, the analyzer and the second polarization controller, and by utilizing the nonlinear polarization rotation generated when the gain pulse propagates in the optical fiber, the fiber laser is made to work in different areas. At the same time, the gain pulse transmitted counterclockwise is filtered by a bandpass filter. When the fiber laser works in the saturated absorption region, dissipative solitons, i.e. bright solitons, are output; when the fiber laser works in the anti-saturated absorption region, dark solitons are output.

[0029] The present invention proposes a method for generating bright solitons and dark solitons. By operating the laser in the normal dispersion region, the fiber laser can be operated in different regions by using nonlinear polarization rotation technology. When operating in the equivalent saturated absorption region, that is, the cavity transmission function is in a positive feedback state, bright solitons can be generated; when operating in the equivalent anti-saturated absorption region, that is, the cavity transmission function is in a negative feedback state, dark solitons can be generated. When stable dark solitons are generated, the background of the dark solitons gradually increases when propagating through the gain fiber, and the blackness of the dark solitons (the ratio of the depression intensity of the dark solitons to the background) remains unchanged. When stable bright solitons are generated, because spectral filtering plays a major role, the spectrum of the bright solitons presents obvious steep edges.

[0030] The method has a simple implementation process and low implementation cost. It is based on a pulse shaping technology determined by a bandpass filtering effect and a pulse shaping technology determined by a balance between normal dispersion and nonlinear effects that satisfy the nonlinear Schrödinger equation. The nonlinear polarization rotation mode-locking technology is used to enable the laser to operate in an equivalent saturated absorption region and an equivalent anti-saturated absorption region, respectively, with the aim of outputting bright solitons and dark solitons, respectively, in the same single-mode fiber laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A diagram of an experimental device for realizing a single-mode fiber laser capable of generating bright soliton and dark soliton output according to an embodiment of the present invention;

[0032] Figure 2 A time domain diagram of bright solitons output by a numerical simulation laser according to an embodiment of the present invention;

[0033] Figure 3 A spectrum diagram of bright solitons output by a numerical simulation laser according to an embodiment of the present invention;

[0034] Figure 4 A time domain diagram of dark solitons output by a numerically simulated laser according to an embodiment of the present invention;

[0035] Figure 5 This is a spectrum diagram of dark solitons output by a numerically simulated laser according to an embodiment of the present invention.

[0036] In the figure: 1. pump source, 2. wavelength division multiplexer, 2a. pump port, 2b. signal port, 2c. common port, 3. erbium-doped fiber, 4. first polarization controller, 5. analyzer, 6. second polarization controller, 7. output coupler, 8. fiber isolator, 9. bandpass filter, 10. fiber ring cavity. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] like Figures 1 to 5 As shown, the present invention provides a single-mode fiber laser that can generate bright solitons and dark solitons, and the fiber laser includes a pump source 1 and a fiber ring cavity 10;

[0039] The fiber ring cavity 10 includes a wavelength division multiplexer 2, an erbium-doped fiber 3, a first polarization controller 4, an analyzer 5, a second polarization controller 6, an output coupler 7, a fiber isolator 8 and a bandpass filter 9;

[0040] The pump port 2a of the wavelength division multiplexer 2 is connected to the output port of the pump source 1 through a single-mode optical fiber;

[0041] The erbium-doped optical fiber 3 is a single-mode optical fiber, one end of which is connected to the common port 2c of the wavelength division multiplexer 2;

[0042] The input end of the first polarization controller 4 is connected to the other end of the erbium-doped optical fiber 3;

[0043] The input end of the polarization analyzer 5 is connected to the output end of the first polarization controller 4 through a single-mode optical fiber;

[0044] The input end of the second polarization controller 6 is connected to the output end of the analyzer 5 through a single-mode optical fiber;

[0045] The energy input port of the output coupler 7 is connected to the output end of the second polarization controller 6 through a single-mode optical fiber, and the output ratio of the second energy output port of the output coupler 7 is not higher than 25%, which serves as the output port of the optical fiber laser;

[0046] The input end of the optical fiber isolator 8 is connected to the first energy output port of the output coupler 7 through a single-mode optical fiber;

[0047] The input end of the bandpass filter 9 is connected to the output end of the optical fiber isolator 8 through a single-mode optical fiber, and the output end thereof is connected to the signal port 2b of the wavelength division multiplexer 2 through a single-mode optical fiber;

[0048] The fiber laser is used to generate stable bright solitons and dark solitons, and the stable bright solitons and dark solitons are output through the second energy output port of the output coupler 7 .

[0049] As a preferred embodiment, the total length of the optical fiber of the fiber laser is 5 meters.

[0050] As a preferred embodiment, the pump source 1 is a semiconductor laser coupled with a normal dispersion fiber, the central wavelength of which is at 976nm or 1480nm, and the output pigtail is a single-mode fiber with normal dispersion in the 1550nm band, and the output power is greater than 400mW. It is preferred to use a pump source 1 with a central wavelength of 976nm to correspond to the pump absorption peak of the erbium-doped fiber to improve the pumping efficiency, and the output pigtail integrally connected to the pump source 1 is a single-mode fiber that is single-mode in the 1550nm band; as a further preferred embodiment, the output pigtail integrally connected to the pump source 1 is a Corning MetroCor.

[0051] As a preferred embodiment, the function of the wavelength division multiplexer 2 is to couple the pump light into the resonant cavity, the working wavelength of the wavelength division multiplexer 2 is 980 / 1550nm or 1480 / 1550nm, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band. As a further preferred embodiment, the output pigtail type of the wavelength division multiplexer 2 is Corning MetroCor.

[0052] As a preferred embodiment, the erbium-doped fiber 3 has normal dispersion fiber in the 1550nm band, an absorption coefficient of 80dB / m at 1530nm, and a length of 3 meters. As a further preferred embodiment, the erbium-doped fiber 3 is EDF80, 300cm long, purchased from OFS, with a high doping concentration, an absorption peak of 80dB / m@1530nm, a strong gain, and a dispersion coefficient of 40.8ps at 1550nm. 2 Of course, as an alternative, other single-mode erbium-doped optical fibers with normal dispersion in the 1550nm band can also be used.

[0053] As a preferred embodiment, the first polarization controller 4 is used to adjust the polarization and loss of the optical pulse in the resonant cavity. The first polarization controller 4 is a three-coil rotating polarization controller or a squeezed polarization controller, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band. As a further preferred embodiment, the output pigtail type of the first polarization controller 4 is Corning MetroCor.

[0054] As a preferred embodiment, the function of the polarizer 5 is to limit the polarization direction of the light pulse passing through the polarizer, and the polarizer 5 is a fiber polarizer, and its output pigtail is a single-mode fiber with normal dispersion in the 1550nm band. As a further preferred embodiment, the output pigtail type of the polarizer 5 is Corning MetroCor.

[0055] As a preferred embodiment, the function of the second polarization controller 6 is to adjust the polarization and loss of the light pulse in the resonant cavity. The second polarization controller 6 is a three-coil rotating polarization controller or a squeezed polarization controller, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band. As a further preferred embodiment, the output pigtail type of the second polarization controller 6 is Corning MetroCor.

[0056] As a preferred embodiment, the function of the optical fiber isolator 8 is to limit the unidirectional operation of the laser, and the optical fiber isolator 8 adopts an isolator with a central wavelength of 1550nm, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band. As a further preferred embodiment, the output pigtail type of the optical fiber isolator 8 is Corning MetroCor.

[0057] As a preferred embodiment, the output coupler 7 is a fiber coupler with an energy ratio of 25:75, and its output pigtail is a single-mode fiber with normal dispersion in the 1550nm band. As a further preferred embodiment, the output pigtail type of the output coupler 7 is Corning MetroCor.

[0058] As a preferred embodiment, the bandpass filter 9 uses an isolator with a central wavelength of 1550nm and a 3dB bandwidth of 7.5nm to 10.5nm, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band. As a further preferred embodiment, the output pigtail type of the bandpass filter 9 is Corning MetroCor.

[0059] The fiber laser of the present invention uses a gain fiber with normal dispersion and a passive fiber with normal dispersion. Allowing the fiber laser to work in the normal dispersion region and introducing a 10nm bandpass filter are the keys to the laser of the present invention to realize the output of bright solitons and dark solitons respectively; when the laser works in the equivalent saturated absorption region, that is, when the cavity transfer function is in a positive feedback state, the pulse shaping received by the gain pulse during propagation is determined by the bandpass filtering effect of the bandpass filter, so that bright solitons can be generated; when the laser works in the equivalent anti-saturated absorption region, that is, when the cavity transfer function is in a negative feedback state, the influence of the wider bandpass filter on the gain pulse is very weak, and the pulse shaping received by the gain pulse during propagation is determined by the balance between normal dispersion and nonlinearity that satisfies the nonlinear Schrödinger equation, so that dark pulses can be generated.

[0060] The fiber laser of the present invention is verified by numerical simulation. The time domain diagram and spectrum diagram of the bright soliton output by the laser obtained by numerical simulation are shown as follows: Figure 2 and 3 As shown in the figure, the time domain diagram and spectrum diagram of the dark soliton are respectively Figure 4 and 5 As shown. Figure 2 From the figure, we can see the typical steep spectral edge of the dissipative soliton (bright soliton) in the normal dispersion region due to the bandpass filtering effect; Figure 4 It can be seen that the depression of the dark soliton goes directly to zero, that is, the blackness of the dark soliton reaches 1.

[0061] The present invention also provides a method for generating bright solitons and dark solitons, using a single-mode fiber laser that can generate bright solitons and dark solitons, comprising the following steps:

[0062] Step 1: Use pump source 1 to provide pump continuous light, and couple the pump continuous light into the fiber laser through wavelength division multiplexer 2;

[0063] Step 2: Utilize the erbium-doped fiber 3 to absorb the pump continuous light and stimulate the emission of long-wave gain pulses. The generated gain pulses oscillate in the fiber laser cavity. Because all devices operate in the normal dispersion region, the gain pulses are not split, ensuring the stable output of subsequent bright solitons and dark solitons.

[0064] Step three: through the joint action of the first polarization controller 4, the analyzer 5 and the second polarization controller 6, and by utilizing the nonlinear polarization rotation generated when the gain pulse propagates in the optical fiber, the optical fiber laser operates in different areas. At the same time, the gain pulse transmitted counterclockwise is filtered by the bandpass filter 9. When the optical fiber laser operates in the saturated absorption region, a dissipative soliton, i.e., a bright soliton output, is obtained; when the optical fiber laser operates in the anti-saturated absorption region, a dark soliton output is obtained.

[0065] In this process, because the fiber laser operates in the normal dispersion region, the counterclockwise transmitted gain pulse is filtered by a bandpass filter. When the laser operates in the saturated absorption region, the pulse shaping received by the gain pulse during propagation is mainly determined by the bandpass filter, so that dissipative solitons, namely bright solitons, can be obtained. When the laser operates in the anti-saturated absorption region, the pulse shaping received by the gain pulse during propagation can be described by the nonlinear Schrödinger equation, which is mainly determined by the mutual balance between nonlinearity and normal dispersion, so that dark soliton output can be obtained.

[0066] The method has a simple implementation process and low implementation cost. It is based on a pulse shaping technology determined by a bandpass filtering effect and a pulse shaping technology determined by a balance between normal dispersion and nonlinear effects that satisfy the nonlinear Schrödinger equation. The nonlinear polarization rotation mode-locking technology is used to enable the laser to operate in an equivalent saturated absorption region and an equivalent anti-saturated absorption region, respectively, with the aim of outputting bright solitons and dark solitons, respectively, in the same single-mode fiber laser.

[0067] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A single-mode fiber laser capable of generating bright solitons and dark solitons, the fiber laser comprising a pump source (1) and a fiber ring cavity (10), characterized in that ； The optical fiber ring cavity (10) comprises a wavelength division multiplexer (2), an erbium-doped optical fiber (3), a first polarization controller (4), an analyzer (5), a second polarization controller (6), an output coupler (7), an optical fiber isolator (8) and a bandpass filter (9); The pump port (2a) of the wavelength division multiplexer (2) is connected to the output port of the pump source (1) via a single-mode optical fiber; The erbium-doped optical fiber (3) is a single-mode optical fiber, one end of which is connected to the common port (2c) of the wavelength division multiplexer (2); The input end of the first polarization controller (4) is connected to the other end of the erbium-doped optical fiber (3); The input end of the polarization analyzer (5) is connected to the output end of the first polarization controller (4) via a single-mode optical fiber; The input end of the second polarization controller (6) is connected to the output end of the analyzer (5) via a single-mode optical fiber; The energy input port of the output coupler (7) is connected to the output end of the second polarization controller (6) through a single-mode optical fiber, and the output ratio of the second energy output port of the output coupler (7) is not higher than 25%, which serves as the output port of the optical fiber laser; The input end of the optical fiber isolator (8) is connected to the first energy output port of the output coupler (7) via a single-mode optical fiber; The input end of the bandpass filter (9) is connected to the output end of the optical fiber isolator (8) through a single-mode optical fiber, and the output end is connected to the signal port (2b) of the wavelength division multiplexer (2) through a single-mode optical fiber; The optical fiber laser is used to generate stable bright solitons and dark solitons, and the stable bright solitons and dark solitons are output through the second energy output port of the output coupler (7).

2. A single-mode fiber laser capable of generating bright solitons and dark solitons according to claim 1, characterized in that: The pump source (1) is a semiconductor laser coupled by an optical fiber with normal dispersion, with a central wavelength at 976nm or 1480nm, and an output tail fiber is a single-mode optical fiber with normal dispersion in the 1550nm band, with an output power greater than 400mW.

3. The single-mode fiber laser capable of generating bright solitons and dark solitons according to claim 1, characterized in that: The working wavelength of the wavelength division multiplexer (2) is 980 / 1550nm or 1480 / 1550nm, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band.

4. The single-mode fiber laser capable of generating bright solitons and dark solitons according to claim 1, characterized in that: The erbium-doped optical fiber (3) is an optical fiber with normal dispersion in the 1550nm band, an absorption coefficient of 80dB / m at 1530nm, and a length of 3 meters.

5. The single-mode fiber laser capable of generating bright solitons and dark solitons according to claim 1, characterized in that: The first polarization controller (4) is a three-coil rotating polarization controller or a squeezed polarization controller, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band; the second polarization controller (6) is a three-coil rotating polarization controller or a squeezed polarization controller, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band.

6. The single-mode fiber laser capable of generating bright solitons and dark solitons according to claim 1, characterized in that: The polarization analyzer (5) is an optical fiber polarization analyzer, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band.

7. The single-mode fiber laser capable of generating bright solitons and dark solitons according to claim 1, characterized in that: The output coupler (7) is a fiber coupler with an energy ratio of 25:75, and its output pigtail is a single-mode fiber with normal dispersion in the 1550nm band.

8. The single-mode fiber laser capable of generating bright solitons and dark solitons according to claim 1, characterized in that: The optical fiber isolator (8) is an isolator with a central wavelength of 1550 nm, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550 nm band.

9. The single-mode fiber laser capable of generating bright solitons and dark solitons according to claim 1, characterized in that: The bandpass filter (9) adopts an isolator with a central wavelength of 1550nm and a 3dB bandwidth of 7.5nm to 10.5nm, and its output pigtail is a single-mode optical fiber with normal dispersion in the 1550nm band.

10. A method for generating bright solitons and dark solitons, using a single-mode fiber laser capable of generating bright solitons and dark solitons as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: using a pump source (1) to provide a pump continuous light, and coupling the pump continuous light into a fiber laser through a wavelength division multiplexer (2); Step 2: Utilize the erbium-doped fiber (3) to absorb the pump continuous light and stimulate the emission of a long-wave gain pulse, and the generated gain pulse oscillates in the fiber laser cavity; Step 3: Through the joint action of the first polarization controller (4), the analyzer (5) and the second polarization controller (6), and by utilizing the nonlinear polarization rotation generated when the gain pulse propagates in the optical fiber, the optical fiber laser is made to work in different regions. At the same time, the gain pulse transmitted counterclockwise is filtered by a bandpass filter (9). When the optical fiber laser works in the saturated absorption region, a dissipative soliton, i.e., a bright soliton output, is obtained; when the optical fiber laser works in the anti-saturated absorption region, a dark soliton output is obtained.

Images