CN102253564B - Continuous pumping optical fiber transmission stimulated Brillouin scattering device and method - Google Patents

Abstract

A system and method for generating stimulated Brillouin scattering, the pulse seed laser (1) sends out the pulse seed laser, the pulse seed laser is transmitted to the optical fiber beam splitter 2 through the polarization maintaining optical fiber, then divided into two bundles, the optical fiber beam combiner 3 is connected with the tail end of the first polarization maintaining optical fiber 7 and the tail end of the second polarization maintaining optical fiber 8, and the first polarization maintaining optical fiber 7 is provided with the optical fiber time difference adjusting device 5, the device 5 is used for adjusting the time difference of the laser beams in the first polarization maintaining optical fiber 7 and the second polarization maintaining optical fiber 8 reaching the optical fiber beam combiner 3, wherein the controller 9 controls the pumping system 6 to start working before the pulse seed laser sends out the pulse laser, and the laser amplifying medium 4 is pumped uninterruptedly in the whole working period.

Description

Optical fiber transmission stimulated Brillouin scattering device and method for continuous pumping

technical field

The invention relates to a Brillouin scattering laser device, which belongs to the technical field of photoelectron detection.

Background technique

At present, the technology of underwater target detection using Brillouin scattering has been practically applied. One of the biggest challenges in the development of this technology is the problem of detection distance. As we all know, the visible light window of fresh water or sea water is around 532nm, but even with this The wavelength of the laser is used as the laser wavelength for Brillouin scattering underwater detection. Due to the different water quality of the sea or lakes to be detected in practice, especially with the intensification of environmental pollution in recent years, there are generally poor water quality in various waters and poor water quality. The direct impact of laser underwater detection is that it seriously affects the transmission distance of the laser. Even in unpolluted waters, the attenuation coefficient of the 532nm laser is relatively large due to the medium water, especially for For various detection devices using the scattered light of stimulated Brillouin scattering, in order to achieve a longer detection distance, a high-power laser is required, but high-power lasers not only require high cost, but also require maintenance. The cost required in all aspects is very high, and the more unfavorable aspect is that the larger the output power of the laser, the larger the volume, and the large-volume laser is not advisable for some applications, because in some In the application, there is not so much space to accommodate a large-volume laser, and for some devices that detect on moving targets, the large volume is obviously not advisable. In order to achieve a longer stimulated Brillouin detection distance without increasing the volume or with a small increase in volume, various solutions have been proposed in the prior art. One of the technical solutions is to use another laser beam with the same frequency and the same polarization state to amplify the returned stimulated Brillouin scattered light, that is, to perform secondary stimulation on the generated stimulated Brillouin scattered light. Excitation amplification to increase the light intensity of the returned stimulated Brillouin scattered light, so as to ensure that the sensor at the receiving end can receive enough stimulated Brillouin scattered light signals for analysis on this basis to obtain the required detection medium Information, currently there are two ways to configure the laser and stimulated Brillouin scattered light path for amplification, one way is to cross the two beams, and the other way is to overlap the two beam paths . What shown in accompanying drawing 1 and accompanying drawing 2 all belong to the situation of intersecting setting, wherein in accompanying drawing 1, utilize two reflecting mirrors 102 and 103 to divide a beam of laser light 101 into two beams, and then separate the two beams of laser light at the receiving The stimulated Brillouin scattering medium 104 intersects to amplify the generated stimulated Brillouin scattered light. In this device, since a laser beam is divided into two beams, the frequency and polarization of the two laser beams are The state is exactly the same, the structure of the device is simple, but there are two problems, one problem is because a laser beam is divided into two beams, so the energy of the two laser beams must not be very high, the second problem The problem is that due to the use of the intersection method, the interaction distance between the two beams of light is very short, resulting in insufficient utilization of the laser beam. Accompanying drawing 2 shows another way of intersecting setting, in order to improve the problem that each laser beam is divided into two beams and cause each energy to become smaller, it is proposed to use the beams emitted by two lasers 201 by means of a mirror 202 Intersecting and incident to the stimulated Brillouin scattering medium 203, each of which is an independent laser, so the energy will not become smaller, in order to ensure that the laser light emitted by the two lasers is exactly the same in nature to ensure the stimulated amplification The occurrence of the same seed laser needs to be injected into the two lasers respectively. In this way, although the system solves the problem of reducing the energy of the laser beam, the device still cannot solve the problem of short interaction distance. In order to solve the problem of short interaction distance, the best way is to overlap the optical paths of the two laser beams. In the existing optical path overlapping settings, as disclosed in the published Chinese patent application CN101266342A, in order to realize the two The pulsed laser beams are overlapped on one optical path with a time difference (which is required for secondary stimulated Brillouin amplification). The device uses photoelectric crystals to control the two laser beams with different polarization states, so as to ensure both The two pulsed lasers are coupled to one optical path with a time difference, and the same polarization state can be guaranteed when reaching the stimulated Brillouin scattering medium. In this device, a polarization coupling mirror and an electro-optic crystal are required to realize the front and rear two beams. The polarization state control of laser beams is not only complicated in structure, but also requires high requirements for electro-optic crystals, and is accompanied by the following problems. The two laser beams used in this device either divide one laser beam into two beams, so that It will lead to the reduction of the energy of the two laser beams. If the two laser beams generated by two lasers are used, although the energy intensity is kept from being reduced, the use of two lasers will take up more space correspondingly, because Two lasers obviously need to occupy twice as much space, and the space problem cannot be solved or it is very difficult to solve in many cases, or it will cause a rapid increase in cost.

Contents of the invention

The present invention is proposed in order to solve the above-mentioned technical problems, not only can realize the overlapping of optical paths of two laser beams of the same nature with time difference, but also realize that the volume of the device does not become significantly larger, and the time difference can be adjusted. The adjustment of its time difference can be set according to the optimization of stimulated Brillouin scattering amplification. Of course, if the above-mentioned device is used for other applications that require two laser beams with the same properties to be overlapped with time difference, the time difference will be Adjustment is made according to actual needs, that is, the device can not only be used in the application of stimulated Brillouin amplification, but also can be applied to similar systems requiring such devices.

In order to solve the above-mentioned technical problems, the present invention has time difference two-way identical laser optical path overlap device comprising: pulse seed laser (1), optical fiber beam splitter (2), optical fiber beam combiner (3), laser amplifying medium (4), an optical fiber time difference adjusting device (5), a laser amplification medium pumping system (6), a first polarization maintaining optical fiber (7), a second polarization maintaining optical fiber (8), and a controller 9 .

The pulse seed laser (1) emits pulse seed laser light, which is transmitted to the fiber beam splitter 2 through a polarization-maintaining optical fiber, and then split into two beams, and the two beams of laser light respectively enter the first polarization beam connected to the fiber beam splitter 2 Maintaining optical fiber 7 and second polarization maintaining optical fiber 8, these two polarization maintaining optical fibers are used to transmit the incoming pulsed laser beams to the optical fiber combiner 3 in a polarization maintaining manner, and the optical fiber combiner 3 is connected with the first polarization The tail ends of the maintaining optical fiber 7 and the second polarization maintaining optical fiber 8 are all connected, that is, their other ends, and an optical fiber time difference adjusting device 5 is arranged in the first polarization maintaining optical fiber 7, and the device 5 is used to adjust the first polarization maintaining The time difference between the arrival of the laser beams in the optical fiber 7 and the second polarization-maintaining optical fiber 8 at the fiber combiner 3, the above-mentioned two laser beams enter the laser amplifying medium 4 after exiting the fiber combiner 3, and the amplified laser beam The beam is then incident on a stimulated Brillouin scattering medium for generating amplified stimulated Brillouin scattering. Wherein the laser amplifying medium 4 has a pumping system 6 symmetrically distributed with respect to the amplifying medium, wherein the controller 9 controls the pumping system 6 to start working before the pulsed seed laser emits pulsed laser light, and the laser amplifying medium 4 is pumped during the entire working period Uninterrupted pumping is implemented, and the pumping system (6) stops for a period of time after amplifying the two beams of seed lasers with a time difference until the next cycle of amplification is performed.

Description of drawings

Accompanying drawing 1 is a system in the prior art that divides a laser beam into two beams and crosses them in a stimulated Brillouin scattering medium;

Accompanying drawing 2 is a system in the prior art where two laser beams emitted by two lasers with the same nature are crossed in a stimulated Brillouin scattering medium;

Accompanying drawing 3 is the first embodiment of the continuous pump stimulated Brillouin scattering device in the present invention;

Accompanying drawing 4 is the second embodiment of the stimulated Brillouin scattering device of continuous pumping in the present invention.

In accompanying drawing 3, 1 represents the seed laser device, 2 represents the optical fiber beam splitter, 3 represents the optical fiber beam combiner, 4 represents the laser amplifying medium, 5 represents the optical fiber time difference adjusting device, 6 represents the pumping system of the laser amplifying medium, and 7 represents the first A polarization maintaining fiber, 8 is a second polarization maintaining fiber, 9 is a controller.

Detailed ways

The first embodiment of the present invention will be described below with reference to FIG. 3 . The pulse seed laser 1 emits pulse seed laser light, and the pulse seed laser light enters the fiber beam splitter 2 after being transmitted through the polarization-maintaining fiber, and then splits into two beams, which respectively enter the first polarization-maintaining fiber 7 and the second polarization-maintaining fiber connected to the fiber beam splitter. Polarization-maintaining optical fiber 8, in the first polarization-maintaining optical fiber 7, an optical fiber time difference adjustment device 5 is arranged, and the tail ends of the first polarization-maintaining optical fiber 7 and the second polarization-maintaining optical fiber 8 are all connected to the fiber combiner 3, that is, the optical fiber The beam combiner 3 is connected to the other end of the first polarization-maintaining optical fiber and the second polarization optical fiber, and the laser beam is incident on the laser amplification medium 4 after passing through the polarization-maintaining optical fiber and the optical fiber beam combiner 3, wherein the laser amplification medium 4 has a The pumping system 6 is symmetrically distributed in the medium, and the controller 9 is connected to the pumping system 6 and the pulse seed laser 1 . The optical fiber time difference adjusting device can adopt an adjustable optical fiber delay device and the like.

The seed laser 1 emits seed laser light, which is transmitted to the fiber beam splitter 2 through a polarization-maintaining fiber, and then split into two beams, respectively entering the first polarization-maintaining fiber 7 and the second polarization-maintaining fiber 8 connected to the fiber beam splitter , in the first polarization maintaining optical fiber 7 is provided with optical fiber time difference adjusting device 5, the tail ends of the first polarization maintaining optical fiber 7 and the second polarization maintaining optical fiber 8 are connected to the fiber combiner 3, and in the first polarization maintaining optical fiber 7 is provided with an optical fiber time difference adjusting device, which is used to adjust the time difference when the laser beams in the first polarization maintaining optical fiber 7 and the second polarization maintaining optical fiber 8 arrive at the fiber combiner 3, and the above two laser beams are in the After exiting the fiber beam combiner 3, it enters into the laser amplification medium 4 to be amplified by the laser amplification medium, and the amplified laser beam then enters the stimulated Brillouin scattering medium (not shown in the figure) for generating amplification stimulated Brillouin scattering. The laser amplifying medium 4 has pumping systems 6 distributed symmetrically with respect to the laser amplifying medium, and the controller 9 controls the pumping system 6 and the pulse seed laser 1 at the same time. Here, the seed laser adopts a pulsed laser, which can not only make the two laser beams distinguish in time, realize the secondary optimization amplification of stimulated Brillouin scattering, but also ensure that the laser beam passing through the laser amplification medium later in time is also Effective amplification can be obtained, and in order to achieve the above two points, it is necessary to ensure that the pumping system has pumped the laser amplification medium to an excited state when the laser beam passes through the laser amplification medium, which is realized by the controller 9. The controller 9 can ensure that the pumping system 6 is already in working condition before the pulsed seed laser emits the pulsed seed laser, and the pumping system keeps working uninterruptedly during the whole process, so as to ensure that the first laser beam passes through the laser amplification Afterwards, the medium can also amplify the second laser beam. After such a setting, two laser beams with the same properties before and after the time difference can be realized in one laser, so that the amplified stimulated Brillouin scattering can be realized. If the laser amplifying medium is pumped for a long time, it may cause damage to the laser amplifying medium due to untimely heat dissipation or excessive heat accumulation. In order to prevent damage to the laser amplifying medium, the device amplifies the After the two seed laser beams, stop for a certain period of time to meet the needs of heat dissipation.

In this system, the optical paths of the front and rear two laser beams are completely overlapped, so as to ensure the maximum distance between the stimulated Brillouin, and at the same time, only one laser is needed, not only does not reduce the energy, and also achieved the purpose of not increasing the volume. At the same time, since the optical fiber time difference adjusting device 5 is provided, the time difference between the front and rear two laser beams can be adjusted arbitrarily, so that the system can be applied to various environments.

The optical fiber time difference adjustment device 5 is used to adjust the time difference between the two laser beams. As for the setting of the time difference, it can be set according to the optimization of stimulated Brillouin scattering. If the above-mentioned device is used for other applications, it can also be set according to the actual The situation is adjusted, that is, the above-mentioned device is not limited to stimulated Brillouin scattering.

The second embodiment of the present invention is described below in conjunction with accompanying drawing 4, in the second embodiment, comprise two laser amplifying media 4 and 4 ', wherein laser amplifying medium 4 has pumping system 6, and laser amplifying medium 4 ' has pump pumping system 6', these two pumping systems are controlled by the controller 9, in the process of use, the two pumping systems work alternately, as has been explained above, due to the need for heat dissipation of the laser amplification medium in the first embodiment It cannot always be in the pumping state, so after amplifying two seed lasers each time, it needs to be interrupted for a period of time. Due to the occurrence of this interruption time, the occurrence frequency of the device is reduced, but for the device of the second embodiment Then the frequency of stimulated Brillouin scattering can be significantly increased. Each of the two laser amplifying media and the corresponding pumping system in this embodiment are the same as those in the first embodiment. The two laser amplifying The media work alternately, for example, first use the laser amplifying medium 4 and the corresponding pumping system 6 to amplify the two seed lasers with time difference required for the first stimulated Brillouin scattering, and then perform the next stimulated Brillouin scattering. When Brillouin scattering occurs, the laser amplifying medium 4' and the pumping system 6' are used to amplify the required two beams of seed laser light with time difference, and the laser amplifying medium 4 and the other seed laser beams are used next time. Corresponding to the pumping system 6 , such alternate use can make each amplifying medium obtain sufficient heat dissipation time without reducing the occurrence frequency of stimulated Brillouin scattering.

Claims (3)

1. a stimulated Brillouin scattering generating means comprises: pulse seed laser instrument (1), fiber optic splitter (2); Optical-fiber bundling device (3), laser amplification medium (4), optical fiber time difference regulating device (5); Laser amplification medium pumping system (6), first polarization-maintaining fiber (7), second polarization-maintaining fiber (8); The 3rd polarization-maintaining fiber, controller (9);

Pulse seed laser instrument (1) sends pulse seed laser; This pulse seed laser is transferred to fiber optic splitter (2) through the 3rd polarization-maintaining fiber; Be divided into two bundles then; This two bundles laser enters into first polarization-maintaining fiber (7) and second polarization-maintaining fiber (8) that is connected with fiber optic splitter (2) respectively; An other end of first polarization-maintaining fiber (7) all is connected with optical-fiber bundling device (3) with an other end of second polarization-maintaining fiber (8); And in first polarization-maintaining fiber (7), be provided with optical fiber time difference regulating device (5); This optical fiber time difference regulating device (5) is used to regulate the mistiming of the laser beam arrival optical-fiber bundling device (3) in first polarization-maintaining fiber (7) and second polarization-maintaining fiber (8), and two above-mentioned bundle seed laser bundles are in output fiber bundling device (3) is injected into laser amplification medium (4) afterwards, and wherein laser amplification medium (4) has the pumping system (6) that is symmetrically distributed about amplification medium; Controller wherein (9) is being controlled pumping system (6) and before the pulse seed laser instrument sends pulse laser, is promptly being started working; And in during two bundle seed lasers with time difference are amplified laser amplification medium (4) is carried out continual pumping, pumping system (6) just stops a period of time after two bundle seed lasers with time difference are amplified, up to carrying out the next round circulation.

2. a stimulated Brillouin scattering generating means comprises: pulse seed laser instrument (1), fiber optic splitter (2); Optical-fiber bundling device (3), first laser amplification medium (4) and second laser amplification medium (4 '), optical fiber time difference regulating device (5); The first laser amplification medium pumping system (6) and the second laser amplification medium pumping system (6 '), first polarization-maintaining fiber (7), second polarization-maintaining fiber (8); The 3rd polarization-maintaining fiber, controller (9);

Pulse seed laser instrument (1) sends pulse seed laser; This pulse seed laser is transferred to fiber optic splitter (2) through the 3rd polarization-maintaining fiber; Be divided into two bundles then; This two bundles laser enters into first polarization-maintaining fiber (7) and second polarization-maintaining fiber (8) that is connected with fiber optic splitter (2) respectively; An other end of first polarization-maintaining fiber (7) all is connected with optical-fiber bundling device (3) with an other end of second polarization-maintaining fiber (8); And in first polarization-maintaining fiber (7), be provided with optical fiber time difference regulating device (5); This optical fiber time difference regulating device (5) is used to regulate the mistiming of the laser beam arrival optical-fiber bundling device (3) in first polarization-maintaining fiber (7) and second polarization-maintaining fiber (8); Two above-mentioned bundle seed laser bundles are in output fiber bundling device (3) is injected into first laser amplification medium (4) and second laser amplification medium (4 ') afterwards; First laser amplification medium (4) and second laser amplification medium order on light path is provided with; Wherein first laser amplification medium (4) has the first laser amplification medium pumping system (6); Second laser amplification medium (4 ') has the second laser amplification medium pumping system (6 '), the first laser amplification medium pumping system (6) and all controlled device of the second laser amplification medium pumping system (6 ') (9) control, and controller wherein (9) is being controlled said two pumping systems and before the pulse seed laser instrument sends pulse laser, is promptly being started working; Said two pumping system alternations; Also be to amplify with first laser amplification medium (4) and the first laser amplification medium pumping system (6) corresponding earlier the needed front and back two bundle seed lasers with time difference of stimulated Brillouin scattering take place for the first time, when carrying out stimulated Brillouin scattering generation next time, use second laser amplification medium (4 ') and the second laser amplification medium pumping system (6 ') to amplify this time needed front and back two bundle seed lasers with time difference with it; Re-use first laser amplification medium (4) and the first laser amplification medium pumping system (6) corresponding next time the time again, be used alternatingly like this with it.

3. stimulated Brillouin scattering method for generation; Pulse seed laser instrument (1) sends pulse seed laser; This pulse seed laser is transferred to fiber optic splitter (2) through polarization-maintaining fiber; Be divided into two bundles then; This two bundles seed laser enters into first polarization-maintaining fiber (7) and second polarization-maintaining fiber (8) that is connected with fiber optic splitter (2) respectively; These two polarization-maintaining fibers are used for the pulse laser beam that imports into separately is transferred to optical-fiber bundling device (3) with the mode that polarization keeps; Optical-fiber bundling device (3) all is connected with an other end of first polarization-maintaining fiber (7) and an other end of second polarization-maintaining fiber (8); And in first polarization-maintaining fiber (7), be provided with optical fiber time difference regulating device (5), this optical fiber time difference regulating device (5) is used to regulate the mistiming of the seed laser bundle arrival optical-fiber bundling device (3) in first polarization-maintaining fiber (7) and second polarization-maintaining fiber (8), and above-mentioned two-way seed laser bundle is in output fiber bundling device (3) is injected into laser amplification medium (4) afterwards; Laser beam through after amplifying then incides the stimulated Brillouin scattering that the stimulated Brillouin scattering medium is used to produce amplification; Wherein laser amplification medium (4) has the pumping system (6) that is symmetrically distributed about amplification medium, and controller wherein (9) is being controlled pumping system (6) and before the pulse seed laser instrument sends pulse laser, promptly started working, and in during two bundle seed lasers with time difference are amplified laser amplification medium (4) is carried out continual pumping; Pumping system (6) just stops a period of time after two bundle seed lasers with time difference are amplified, up to carrying out the next round circulation.

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