阅读说明：本技术 一种基于布里渊随机光纤激光振荡的光速调控方法 (Light velocity regulating method based on Brillouin random fiber laser oscillation ) 是由 张亮 肖哲澜 裘增欢 张吉临 谢浩然 蒋义坤 于 2021-05-11 设计创作，主要内容包括：本发明涉及一种基于布里渊随机激光振荡的光群速度调控方法,基于布里渊随机光纤激光振荡装置实现快光及超光速传输,由两个光环形器、布里渊增益光纤和随机反馈介质构成半开放的环形腔,利用光纤介质中背向瑞利散射或弱光纤光栅阵列提供的分布式随机反馈取代传统固定共振腔中的单点镜面反馈,形成随机激光振荡,从而实现斯托克斯激光的单纵模运转,并对泵浦光信号产生反常色散和群速度加快效应,在超长距离上实现泵浦光信号群速度的光学调控。本发明不仅具有低阈值、室温下操作和工作在任意波长的优势,而且可实现在百米甚至千米量级超长光纤传输距离下的光速调控,在光纤传感及光通信传输方面具有良好的应用前景。(The invention relates to a light group velocity regulation and control method based on Brillouin random laser oscillation, which is characterized in that a Brillouin random fiber laser oscillation device is used for realizing fast light and super-fast light transmission, a semi-open annular cavity is formed by two optical circulators, Brillouin gain fibers and a random feedback medium, distributed random feedback provided by a back Rayleigh scattering or weak fiber grating array in the fiber medium is used for replacing single-point mirror feedback in a traditional fixed resonant cavity to form random laser oscillation, so that single longitudinal mode operation of Stokes laser is realized, abnormal dispersion and group velocity acceleration effects are generated on pumping light signals, and optical regulation and control of the group velocity of the pumping light signals are realized on super-long distance. The invention not only has the advantages of low threshold value, operation at room temperature and working at any wavelength, but also can realize the light speed regulation and control under the transmission distance of the ultra-long optical fiber with the magnitude of hundreds of meters or even kilometers, and has good application prospect in the aspects of optical fiber sensing and optical communication transmission.)

1. A light velocity regulation and control method based on Brillouin random fiber laser oscillation is realized based on a Brillouin random fiber laser oscillation device, and the device mainly comprises a narrow linewidth laser (1), an electro-optical modulator EOM (2), a signal generator (3), an optical amplifier (4), a first fiber circulator (5), a Brillouin gain fiber (6), an optical fiber coupler (7), a second fiber circulator (8) and a random feedback medium (9); the group velocity monitoring device of light includes photoelectric detector PD (10) and oscilloscope (11), its characterized in that, the speed of light regulation and control step is as follows:

a. the light emitted by the narrow linewidth laser (1) enters the electro-optical modulator EOM (2) and is modulated, and signal light with different frequencies and different waveforms is generated through modulation of the signal generator (3);

b. the modulated signal light enters an optical amplifier (4), and the amplifier performs power amplification on the optical signal to different degrees to obtain signal light under different average powers;

c. the optical signal output by the amplifier is used as Brillouin pump light, enters a section of optical fiber through the first port to the second port of the first optical fiber circulator (5) for transmission, and simultaneously excites the stimulated Brillouin scattering effect in the optical fiber;

d. the modulation condition of the signal light influences the acceleration degree of the optical group speed due to the limitation of the bandwidth of the Brillouin gain spectrum, and under the condition of the same sinusoidal modulation waveform, the modulation frequency is different, and the corresponding acceleration amount of the optical group speed is different;

e. under the condition that other conditions are not changed, when the set modulation frequency is smaller, the time lead of the monitored time domain waveform is larger, and the acceleration of the corresponding group speed is larger.

2. The optical speed regulation method based on brillouin random fiber laser oscillation according to claim 1, characterized in that: in the semi-open optical fiber annular cavity, a pumping optical signal enters a Brillouin gain optical fiber (6), and the section of optical fiber is used as a transmission medium; because the Brillouin random fiber laser oscillation device has the natural advantage of single longitudinal mode laser operation, the transmission distance can reach the magnitude of hundreds of meters or even kilometers.

3. The optical speed regulation method based on brillouin random fiber laser oscillation according to claim 1, characterized in that: stokes light generated by excitation in the gain fiber is transmitted along the reverse direction, enters the second fiber circulator (8) through the ports from the second to the third of the first fiber circulator (5), enters the random feedback medium (9) through the ports from the first to the third of the second fiber circulator (8), provides distributed random feedback through the feedback medium, returns to the annular cavity through the ports from the second to the third of the second fiber circulator (8), reenters the gain fiber (6) through the fiber coupler (7) and participates in the process of Brillouin scattering with pump light; the feedback medium (9) is used for providing random distributed feedback to replace the traditional single-point mirror reflection, and Rayleigh scattering in common optical fibers or a weak optical fiber grating array is selected to provide distributed random feedback to realize random oscillation.

4. The optical speed regulation method based on brillouin random fiber laser oscillation according to claim 1, characterized in that: after the pump light signal is subjected to loss caused by Brillouin scattering, an anomalous dispersion region is generated, the optical group velocity of the pump light signal is further changed, the modulated light signal is transmitted through a gain fiber (6), then the modulated light signal is output from a semi-open annular cavity through a fiber coupler (7), is converted into an electric signal through a photoelectric detector PD (10) and is monitored by an oscilloscope (11), and corresponding time lead is calculated by reading time position points of signal wave crests in the same period under different pump powers on the oscilloscope (11), so that the acceleration degree of the optical group velocity is represented.

5. The optical speed regulation method based on brillouin random fiber laser oscillation according to claim 1, characterized in that: the optical fiber coupler mainly has the function of outputting and monitoring signal light in the device, a 2 x 2 coupler with the splitting ratio of 10/90 is selected, and 90% of ports on two sides are connected in a semi-open annular cavity, so that most Stokes light can still be transmitted in the optical fiber cavity, and the Stokes laser power in the cavity is ensured.

Technical Field

The invention relates to an optical regulation and control technology of a nonlinear effect, in particular to an optical speed regulation and control method based on Brillouin random laser oscillation, which mainly utilizes the Brillouin random optical fiber laser oscillation to realize all-optical regulation and control of optical group speed in long-distance optical fiber transmission.

Background

The group velocity regulation of light has important application prospects in the fields of all-optical communication, high-sensitivity sensing, interaction of light and substances and microwave photonics. Particularly, the fast light technology has important application value in the fields of laser interferometers, time stealth and laser gyroscopes.

Group velocity modulation based on optical fiber media has received much attention due to the advantages of low loss of the optical fiber itself, and ease of compatibility in optical fiber communication systems. The fast and slow light technology in the optical fiber medium is mainly realized through different nonlinear effects, wherein the fast and slow light scheme based on the stimulated Brillouin scattering effect has unique advantages due to low threshold value, operation at any wavelength and operability at room temperature. Heretofore, a method for realizing light velocity regulation by using a stimulated brillouin scattering effect is firstly realized in a brillouin optical fiber amplifier structure (see Song, k.et al.optics Express 13,82-88,2005), however, the efficiency of realizing group velocity acceleration by using the amplifier structure-based method is low, and the structure is relatively complex. Then, a scheme based on brillouin laser oscillation in a single-mode optical fiber has been proposed, and has attracted attention because of its advantages of self-acceleration, low loss, and high efficiency.

At present, the optical speed regulation and control technology based on Brillouin laser oscillation in the optical fiber is realized and further optimized by a method based on a special optical fiber, a mixed gain cavity structure and an embedded saturable absorber structure.

1. The optical speed regulation and control Technology based on the Brillouin laser oscillation is realized by using special optical fibers (see Deng, D.et al. IEEE Photonics Technology Letters 26, 1758-.

2. The mixed gain cavity structure is characterized in that a section of erbium-doped fiber excited by 980nm pumping is embedded into a Brillouin optical fiber annular cavity to serve as an auxiliary gain medium. (see Gao, l.et al. optics Letters 44, 5097-; the introduction of the erbium-doped fiber can effectively lower the threshold of the emergent Stokes laser, thereby improving the phenomenon of gain saturation. Final correlation experiments achieved 444.4ns timing advance in a 2m length of highly nonlinear fiber using a hybrid gain cavity structure incorporating a pumped erbium doped fiber.

3. The optical group speed acceleration efficiency based on the Brillouin laser oscillation is mainly limited by the bandwidth brought by the longitudinal mode of the laser in the cavity, in order to ensure the output of the Stokes single longitudinal mode laser, the methods all adopt a short cavity method, and the optical fiber with the length of less than 10 meters is used as the Brillouin gain optical fiber, so that the optical speed regulation and control on the long-distance optical fiber cannot be realized. To overcome the fiber transmission distance limitation of fast light, single-frequency laser technology based on a saturated absorption structure is adopted (see Zhang, l.et al. optics Letters 40, 4404-. The method provides that an optical fiber saturable absorber structure consisting of a circulator, a coupler and a section of unpumped erbium-doped optical fiber is embedded in a long optical fiber ring cavity, and a stable standing wave is formed by optical signals transmitted in two directions in the optical fiber ring by adjusting a polarization controller in the optical fiber ring, so that a weakly coupled Bragg dynamic grating is formed, the effect of inhibiting multiple longitudinal modes is achieved, and the single longitudinal mode operation of the Stokes laser is realized. And finally, long-distance group velocity regulation and control of 500m high nonlinear optical fiber are realized.

In previous researches, optical speed regulation schemes based on brillouin laser oscillation are all realized based on a fixed and closed laser resonant cavity, however, multiple longitudinal mode oscillations inevitably exist in the fixed fiber resonant cavity, and therefore the efficiency and the transmission distance of optical speed regulation are limited. The realization of light velocity regulation in long-distance optical fiber transmission is the key direction of research in the field, wherein single longitudinal mode stokes laser operation is a key factor for breaking through the limitation of light velocity regulation distance, although a part of multiple longitudinal modes can be limited through a saturated absorber structure, a certain saturation effect exists, the single longitudinal mode operation cannot be guaranteed under a high-power condition, and the acceleration of group velocity is still limited by the influence of laser multiple longitudinal mode oscillation.

Disclosure of Invention

Aiming at solving the problems of the prior art, the invention aims to overcome the defects of the prior art and provide a light velocity regulation method based on novel Brillouin random fiber laser oscillation, aiming at the fundamental problem that the current light velocity regulation experiment is based on a fixed laser resonant cavity scheme and is limited by multi-longitudinal-mode transmission on distance factors, a semi-open annular cavity is formed by two optical circulators, Brillouin gain fibers and a random feedback medium, single-point mirror feedback in the traditional fixed resonant cavity is replaced by distributed random feedback provided by back Rayleigh scattering or weak fiber grating arrays in the fiber medium to form random laser oscillation, so that the single-longitudinal-mode operation of Stokes laser is realized, the abnormal dispersion and the group velocity acceleration effect are generated on pumping light signals, the limitation of multi-longitudinal-mode Kekes laser oscillation on the regulation of the pumping light group velocity in the traditional fast light regulation scheme of Brillouin laser oscillation in long-distance fiber transmission is broken, and finally, the optical regulation and control of the group speed of the pump light signals is realized on an ultra-long distance. The optical speed regulation and control method based on the Brillouin scattering not only has the advantages of low threshold value, operation at room temperature and working at any wavelength, but also can realize the optical speed regulation and control under the transmission distance of the ultra-long optical fiber of hundred meters or even kilometers, and has good application prospect in the aspects of optical fiber sensing and optical communication transmission.

In order to achieve the purpose of the invention, the invention adopts the following technical scheme:

a light velocity regulation and control method based on Brillouin random fiber laser oscillation is realized based on a Brillouin random fiber laser oscillation device, and the device mainly comprises a narrow linewidth laser, an electro-optical modulator EOM, a signal generator, an optical amplifier, a first fiber circulator, a Brillouin gain fiber, an optical fiber coupler, a second fiber circulator and a random feedback medium; the group velocity monitoring device of light includes photoelectric detector PD and oscilloscope, and the speed of light regulation and control step is as follows:

a. the light emitted by the narrow-linewidth laser enters the electro-optic modulator EOM and is modulated, and signal light with different frequencies and different waveforms is generated through modulation of the signal generator;

b. the modulated signal light enters an optical amplifier, and the amplifier performs power amplification on the optical signal to different degrees to obtain signal light under different average powers;

c. the optical signal output by the amplifier is used as Brillouin pump light, enters a section of optical fiber through the first to the second ports of the first optical fiber circulator for transmission, and simultaneously excites the stimulated Brillouin scattering effect in the optical fiber;

d. the modulation condition of the signal light influences the acceleration degree of the optical group speed due to the limitation of the bandwidth of the Brillouin gain spectrum, and under the condition of the same sinusoidal modulation waveform, the modulation frequency is different, and the corresponding acceleration amount of the optical group speed is different;

e. under the condition that other conditions are not changed, when the set modulation frequency is smaller, the time lead of the monitored time domain waveform is larger, and the acceleration of the corresponding group speed is larger.

Preferably, in the semi-open fiber ring cavity, the pump light signal enters the brillouin gain fiber, while the section of fiber serves as a transmission medium; because the Brillouin random fiber laser oscillation device has the natural advantage of single longitudinal mode laser operation, the transmission distance can reach the magnitude of hundreds of meters or even kilometers.

Preferably, stokes light generated by excitation in the gain fiber is transmitted along the reverse direction, enters the second fiber circulator through the ports from the second part to the third part of the first fiber circulator, enters the random feedback medium through the ports from the first part to the second part of the second fiber circulator, the feedback medium provides distributed random feedback, the feedback light returns to the annular cavity through the ports from the second part to the third part of the second fiber circulator, reenters the gain fiber through the fiber coupler and participates in the process of stimulated Brillouin scattering with the pump light; the feedback medium is used for providing random distributed feedback to replace the traditional single-point mirror reflection, and Rayleigh scattering in common optical fibers or a weak optical fiber grating array is selected to provide distributed random feedback to realize random oscillation.

Preferably, the pump optical signal generates an anomalous dispersion region after undergoing loss caused by brillouin scattering, so as to change the optical group velocity of the pump optical signal, the modulated optical signal is output from the semi-open annular cavity through the optical fiber coupler after passing through the gain optical fiber, is converted into an electrical signal through the photoelectric detector PD and is monitored by the oscilloscope, and the corresponding time advance is calculated by reading the time position point of the signal peak in the same period under different pump powers on the oscilloscope, so as to represent the acceleration degree of the optical group velocity.

Preferably, the optical fiber coupler mainly plays a role in outputting and monitoring signal light in the device, a 2 × 2 coupler with a splitting ratio of 10/90 is selected, and 90% of ports on two sides are connected in a semi-open annular cavity, so that most stokes light can still be transmitted in the optical fiber cavity, and the stokes laser power in the cavity is ensured. Couplers with other splitting ratios can also be selected for operation.

Preferably, the light emitted from the laser source enters the electro-optical modulator EOM and is modulated, and the signal generator generates signals with different frequencies and different waveforms to correspondingly modulate the light. The modulated light enters an optical amplifier, and the optical signal is subjected to power amplification to different degrees by the amplifier so as to obtain the final output signal light waveform under different powers. The optical signal output by the amplifier will enter the semi-open ring cavity as pump signal light. Through the ports from the first to the second of the first optical fiber circulator, pumping signal light enters the Brillouin gain optical fiber, and the section of optical fiber also serves as a transmission medium; the Stokes light generated by the excitation in the gain fiber is transmitted along the reverse direction, enters the second fiber circulator through the ports from the second to the third of the first fiber circulator, enters the feedback medium through the ports from the first to the second of the second fiber circulator, provides distributed random feedback light through the feedback medium, is transmitted reversely, returns to the annular cavity again through the ports from the second to the third of the second fiber circulator, reenters the Brillouin gain fiber through the coupler, and participates in the process of stimulated Brillouin scattering. The pump light signal undergoes anomalous dispersion after Brillouin scattering, is output from the semi-open annular cavity through the coupler after being transmitted through the gain fiber, is converted into an electric signal through the photoelectric detector PD and is monitored by the oscilloscope.

Preferably, the timing advance of the signal light is affected by modulation conditions, and in the case of the same modulation waveform, the modulation frequency is different, and the group velocity is increased by a different amount. Generally, when the set modulation frequency is smaller, the time advance of the monitored time domain waveform is larger, and the corresponding group speed is increased by a larger amount.

Preferably, the length of the brillouin gain medium is selected from optical fibers with a length of hundreds of meters to kilometers due to the advantage of single-frequency laser output of the brillouin random laser oscillation device, so that long-distance light speed regulation is realized. The properties of the optical fiber also have an influence on the acceleration degree of the group velocity, and theoretically, the optical fiber with smaller core radius and higher Brillouin gain coefficient can provide larger time advance and group velocity acceleration under certain other conditions as a gain medium.

Preferably, the feedback medium is used for providing random feedback, and optical fibers with lengths of more than one hundred meters can be selected for providing Rayleigh scattering feedback or a random feedback medium such as a weak fiber grating array can be selected for providing distributed random feedback.

Preferably, the fast optical modulation control method based on Brillouin random fiber oscillation is based on a Brillouin random laser oscillation device, and breaks through the situation that the traditional laser oscillation device has a fixed resonant cavity to cause multi-longitudinal-mode laser. The output of the random laser has specific statistical characteristics and natural single-mode transmission characteristics, and full-optical regulation and control of the optical group speed over an ultra-long distance can be realized.

Compared with the prior art, the invention has the following obvious and prominent substantive characteristics and remarkable advantages:

1. the invention relates to an optical group velocity regulation and control method based on Brillouin random laser oscillation. The method is mainly based on a Brillouin random fiber laser oscillation device to realize fast light and super-fast light transmission, and the device basically comprises the following steps: the device comprises a laser source, an electro-optical modulator, a signal generator, an optical circulator, an optical fiber and a coupler; the invention is characterized in that: the semi-open annular cavity is formed by two optical circulators, the Brillouin gain optical fiber and a random feedback medium, and distributed random feedback provided by a backward Rayleigh scattering or weak optical fiber grating array in the optical fiber medium is used for replacing single-point mirror feedback in a traditional fixed resonant cavity to form random laser oscillation, so that single longitudinal mode operation of Stokes laser is realized, abnormal dispersion and group velocity acceleration effects are generated on pumping optical signals, the limitation of multi-longitudinal mode Stokes laser oscillation on pumping optical group velocity regulation in a traditional Brillouin laser oscillation fast light regulation scheme in long-distance optical fiber transmission is broken, and finally optical regulation of the pumping optical signal group velocity is realized over a very long distance;

2. the light speed regulation and control method based on Brillouin scattering not only has the advantages of low threshold value, operation at room temperature and working at any wavelength, but also can realize light speed regulation and control at the transmission distance of hundreds of meters or even kilometers of ultra-long optical fiber, and has good application prospect in the aspects of optical fiber sensing and optical communication transmission;

3. the method is simple and easy to implement, low in cost and suitable for popularization and application.

Drawings

Fig. 1 is a system diagram showing a fast light control method based on a brillouin single mode random fiber laser according to the present invention.

Fig. 2 is a system diagram of a fast light control method based on a brillouin polarization-maintaining random fiber laser according to the present invention.

Fig. 3 is a system diagram showing a fast optical modulation method of a random fiber laser based on a brillouin hybrid gain cavity according to the present invention.

The reference numbers in the drawings are specifically indicated as: 1. a narrow linewidth laser; 2. an electro-optic modulator; 3. a signal generator; 4. an erbium-doped fiber amplifier; 5. a first optical circulator; 6. a gain fiber; 7. an optical coupler; 8. a second optical circulator; 9. a feedback medium; 10. a photodetector; 11. an oscilloscope; 12. a light polarization controller; 13. an optical splitter; 14. pumped erbium doped fiber.

Detailed Description

The technical method of the present invention will be explained in detail below with reference to embodiments in the drawings. However, the present invention is not limited to the following embodiments. Many forms may be made without departing from the spirit of the invention and the scope of the claims, which are to be protected thereby.

The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below:

the first embodiment is as follows:

in this embodiment, referring to fig. 1, an optical speed control method based on brillouin random fiber laser oscillation is implemented based on a brillouin random fiber laser oscillation device, which mainly includes a narrow linewidth laser 1, an electro-optical modulator EOM2, a signal generator 3, an optical amplifier 4, a first fiber circulator 5, a brillouin gain fiber 6, a fiber coupler 7, a second fiber circulator 8, and a random feedback medium 9; the group velocity monitoring device of light comprises a photoelectric detector PD10 and an oscilloscope 11, and the light velocity regulating and controlling steps are as follows:

a. the light emitted by the narrow linewidth laser 1 enters the electro-optic modulator EOM2 to be modulated, and signal light with different frequencies and different waveforms is generated by the modulation of the signal generator 3;

b. the modulated signal light enters an optical amplifier 4, and the amplifier performs power amplification on the optical signal to different degrees to obtain signal light under different average powers;

c. the optical signal output by the amplifier is used as Brillouin pump light, enters a section of optical fiber through the ports from the first part to the second part of the first optical fiber circulator 5 for transmission, and simultaneously excites the stimulated Brillouin scattering effect in the optical fiber;

d. the modulation condition of the signal light influences the acceleration degree of the optical group speed due to the limitation of the bandwidth of the Brillouin gain spectrum, and under the condition of the same sinusoidal modulation waveform, the modulation frequency is different, and the corresponding acceleration amount of the optical group speed is different;

e. under the condition that other conditions are not changed, when the set modulation frequency is smaller, the time lead of the monitored time domain waveform is larger, and the acceleration of the corresponding group speed is larger.

The optical speed regulation and control method based on the Brillouin scattering not only has the advantages of low threshold value, operation at room temperature and working at any wavelength, but also can realize the optical speed regulation and control under the transmission distance of the ultra-long optical fiber of hundred meters or even kilometers, and has good application prospect in the aspects of optical fiber sensing and optical communication transmission.

Example two:

this embodiment is substantially the same as the first embodiment, and is characterized in that:

in this embodiment, in the semi-open fiber ring cavity, the pump light signal enters the brillouin gain fiber 6, and this segment of fiber serves as a transmission medium; because the Brillouin random fiber laser oscillation device has the natural advantage of single longitudinal mode laser operation, the transmission distance can reach the magnitude of hundreds of meters or even kilometers.

In the embodiment, stokes light generated by excitation in the gain fiber is transmitted along the reverse direction, enters the second fiber circulator 8 through ports from the second to the third of the first fiber circulator 5, enters the random feedback medium 9 through ports from the first to the third of the second fiber circulator 8, provides distributed random feedback through the feedback medium, returns to the ring cavity through ports from the third to the fourth of the second fiber circulator 8, reenters the gain fiber 6 through the fiber coupler 7, and participates in the stimulated brillouin scattering process with the pump light; the feedback medium 9 is used for providing random distributed feedback, replaces the traditional single-point mirror reflection, and selects Rayleigh scattering in common optical fibers or a weak optical fiber grating array to provide distributed random feedback so as to realize random oscillation.

In this embodiment, the pump optical signal generates an anomalous dispersion region after undergoing a loss caused by brillouin scattering, so as to change the optical group velocity thereof, the modulated optical signal is output from the semi-open ring cavity through the optical fiber coupler 7 after passing through the gain optical fiber 6, is converted into an electrical signal through the photodetector PD10 and is monitored by the oscilloscope 11, and the corresponding time advance is calculated by reading the time position point of the signal peak in the same period under different pump powers on the oscilloscope 11, so as to characterize the acceleration degree of the optical group velocity.

In this embodiment, the optical fiber coupler mainly outputs and monitors signal light, a 2 × 2 coupler with a splitting ratio of 10/90 is selected, and 90% of ports on two sides are connected in a semi-open ring cavity, so that most stokes light can still be transmitted in the optical fiber cavity, and the stokes laser power in the cavity is ensured.

The embodiment is an optical group velocity control method based on Brillouin random laser oscillation. The method is mainly based on a Brillouin random fiber laser oscillation device to realize fast light and super-fast light transmission, and the device basically comprises the following steps: the device comprises a laser source, an electro-optical modulator, a signal generator, an optical circulator, an optical fiber and a coupler; the method of the embodiment is characterized in that: the semi-open annular cavity is formed by two optical circulators, the Brillouin gain fiber and a random feedback medium, and distributed random feedback provided by a backward Rayleigh scattering or weak fiber grating array in the optical fiber medium is used for replacing single-point mirror feedback in a traditional fixed resonant cavity to form random laser oscillation, so that single longitudinal mode operation of Stokes laser is realized, abnormal dispersion and group velocity acceleration effects are generated on pumping optical signals, the limitation of multi-longitudinal mode Stokes laser oscillation on pumping optical group velocity regulation in a traditional fast light regulation scheme of Brillouin laser oscillation in long-distance optical fiber transmission is broken, and finally optical regulation of the group velocity of the pumping optical signals is realized over a very long distance.

Example three:

this embodiment is substantially the same as the above embodiment, and is characterized in that:

in this embodiment, as shown in fig. 1, the optical speed regulation scheme based on brillouin random single-mode fiber laser oscillation includes: 1. a 1550nm narrow linewidth laser; 2. an electro-optic modulator; 3. a signal generator; 4. an erbium-doped fiber amplifier; 5. a first single mode fiber circulator; 6. a 500m long single mode fiber; 7. a single mode coupler with a splitting ratio of 10/90; 8. a second single mode fiber circulator; 9. 1km of long single mode fiber; 10. a photodetector; 11. an oscilloscope.

The 20kHz narrow linewidth laser emits 1550nm laser, the laser is modulated into 100kHz sine waveform through the electro-optic modulator, the sine waveform is amplified in different degrees of power through the EDFA, and the laser enters the Brillouin gain optical fiber through the ports from the first optical circulator to the second optical circulator. When no stimulated brillouin scattering effect occurs, the transit time of the beam through the fiber is:

where L is the length of the gain fiber, c is the speed of light in vacuum, n_gIs the group index of refraction determined by the properties of the original fiber material.

The power of the pumping signal light is continuously increased along with continuous adjustment of the erbium-doped fiber amplifier, when the power exceeds a stimulated Brillouin scattering threshold value, a stimulated Brillouin scattering phenomenon occurs in an optical fiber medium, Stokes light generated by stimulation is transmitted in a reverse direction and enters another section of optical fiber to generate Rayleigh scattering, and Rayleigh scattering light returns to a semi-open ring cavity again and enters a gain optical fiber to participate in a Brillouin laser resonance process. According to the Kramers-Kronig relationship, absorption or loss of resonance affects the change in refractive index and thus the group refraction. Therefore, as the stimulated brillouin scattering occurs, the transit time of the light beam through the optical fiber changes:

where L is still the length of the gain fiber, c is the speed of light in vacuum, n_g' is the group refractive index corresponding to the stimulated Brillouin scattering。

The waveform of the output signal light can be monitored by an oscilloscope. By reading the time position of the sine wave crest in the same period on an oscilloscope, the difference of the propagation time of the light beam in the optical fiber can be calculated, which is called as the time advance:

according to the time advance, the group refractive index and the group velocity of the corresponding signal light under the current pumping power can be calculated:

therefore, the timing advance at different pump powers can be read correspondingly by adjusting the erbium-doped fiber amplifier. The greater the timing advance, the greater the degree of acceleration of the group speed. The timing advance is limited by other factors, and the decision formula is as follows:

wherein G is the Brillouin gain, gamma_BRepresents the Brillouin gain bandwidth, I_SExpressing the energy of the Stokes light, L being the length of the gain fiber, g representing the Brillouin gain coefficient, P_SRepresents the Stokes light power, A_effThe effective mode field area of the fiber.

Example four:

this embodiment is substantially the same as the above embodiment, and is characterized in that:

in this embodiment, the degree of group velocity increase is directly related to the stability of the fiber laser oscillation. As shown in fig. 2, the optical speed regulation scheme based on the brillouin random polarization-maintaining fiber laser includes: 1. a 1550nm narrow linewidth laser; 2. an electro-optic modulator; 3. a signal generator; 4. an erbium-doped fiber amplifier; 5. a first polarization maintaining circulator; 6. a 500m length of polarization maintaining fiber; 7. a polarization-maintaining fiber coupler with a splitting ratio of 10/90; 8. a second polarization maintaining fiber circulator; 9. a polarization maintaining fiber of 1km length; 10. a photodetector; 11. an oscilloscope; 12. a light polarization controller; 13. a beam splitter.

Fig. 2 shows a brillouin random fiber laser with a full polarization-maintaining cavity structure, wherein the polarization direction of pump signal light emitted from an erbium-doped fiber amplifier is adjusted by an optical polarization controller, and is monitored by a polarization beam splitter, and when most of the power is aligned to the slow axis of the beam splitter, linear polarization light output by the slow axis of the beam splitter is used as the pump signal light.

In the full polarization maintaining structure, the polarization characteristics of the pump light and the Stokes laser can be maintained, and the optimal Brillouin gain can be provided when the polarization of the two beams of light are matched, so that the time advance is improved, and the regulation degree of the light group velocity is improved.

Example five:

this embodiment is substantially the same as the above embodiment, and is characterized in that:

in this embodiment, as shown in fig. 3, an erbium-doped fiber gain is added into the cavity based on the random laser of the example 2 with the full polarization-maintaining function, and generally includes: 1. a 1550nm narrow linewidth laser; 2. an electro-optic modulator; 3. a signal generator; 4. an erbium-doped fiber amplifier; 5. a first polarization maintaining circulator; 6. a 500m length of polarization maintaining fiber; 7. a polarization maintaining coupler with a splitting ratio of 10/90; 8. a second polarization maintaining circulator; 9. a polarization maintaining fiber of 1km length; 10. a photodetector; 11. an oscilloscope; 12. a light polarization controller; 13. an optical splitter; 14. pumped erbium doped fiber. Wherein the pumped erbium doped fiber comprises: 15. a wavelength division multiplexer WDM; 16. a 980nm pump source; 17. an 8m long erbium doped fiber.

In the erbium doped fiber part of the pump, the 980nm pump excited erbium doped fiber is used as a gain medium. When the Stokes laser enters the part, stimulated radiation amplification can occur, so that power gain is increased, the stimulated Brillouin scattering process in the gain fiber is enhanced, and the optimization of the optical speed regulation degree based on Brillouin random laser oscillation is realized from the direction of improving the laser power in the Stokes cavity.

The above embodiment is an optical group velocity control method based on brillouin random laser oscillation. The method is mainly based on a Brillouin random fiber laser oscillation device to realize fast light and super-fast light transmission, and the device basically comprises the following steps: laser source, electro-optical modulator, signal generator, optical circulator, optical fiber and coupler. The characteristics of the above embodiment are: the semi-open annular cavity is formed by two optical circulators, the Brillouin gain fiber and a random feedback medium, and distributed random feedback provided by a backward Rayleigh scattering or weak fiber grating array in the optical fiber medium is used for replacing single-point mirror feedback in a traditional fixed resonant cavity to form random laser oscillation, so that single longitudinal mode operation of Stokes laser is realized, abnormal dispersion and group velocity acceleration effects are generated on pumping optical signals, the limitation of multi-longitudinal mode Stokes laser oscillation on pumping optical group velocity regulation in a traditional fast light regulation scheme of Brillouin laser oscillation in long-distance optical fiber transmission is broken, and finally optical regulation of the group velocity of the pumping optical signals is realized over a very long distance. The optical speed regulation and control method based on Brillouin scattering in the embodiment has the advantages of low threshold value, operation at room temperature and working at any wavelength, can realize optical speed regulation and control at the transmission distance of the ultra-long optical fiber of hundred meters or even kilometers, and has good application prospect in the aspects of optical fiber sensing and optical communication transmission.

The embodiments of the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to the embodiments, and various changes and modifications can be made according to the purpose of the invention, and any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention shall be equivalent substitutions, as long as the purpose of the present invention is met, and the present invention shall fall within the protection scope of the present invention without departing from the technical principle and inventive concept of the present invention.