CN106532415A - Inclined grating-based stimulated Raman scattering effect suppression type optical fiber laser - Google Patents

Abstract

The invention belongs to the technical field of optical fiber communication, and discloses a stimulated Raman scattering effect-suppressed fiber laser based on a tilted grating, including: a pump source for outputting pump light; a gain fiber; a pump coupling device, and the The pump source is connected to the gain fiber for coupling the pump light into the gain fiber; the reflection component is connected to the gain fiber to reflect and couple the pump light output from the gain fiber into the gain An optical fiber; a tilted grating structure, connected to the gain fiber, used to deplete the energy of the stimulated Raman scattering wave exceeding the threshold wavelength. The invention provides a stimulated Raman scattering effect-suppressing fiber laser based on a tilted grating, which can take both the suppression of the stimulated Raman scattering effect and the equipment performance into account.

Description

A Stimulated Raman Scattering Suppressed Fiber Laser Based on Slanted Grating

technical field

The invention relates to the technical field of optical fiber line communication, in particular to a stimulated Raman scattering effect-suppressed fiber laser based on a tilted grating.

Background technique

There is a nonlinear effect in the quartz fiber. When a high power density optical signal is transmitted in the fiber, the refractive index of the fiber material is modulated by the high power light intensity, so that it is no longer a linear medium characteristic, and a new gain different from that of the signal light is produced. And frequency components, which affect the normal optical fiber signal transmission. The existing single-mode or multi-mode high-power fiber lasers are affected by the stimulated Raman scattering effect SRS to varying degrees, which will produce new wavelength components different from the laser's own wavelength, resulting in monochromaticity of the laser and performance degradation, so generally high-power lasers will take measures to suppress SRS and improve laser performance.

In the prior art, the main method for suppressing SRS in fiber lasers is to use large-diameter fibers, reduce the fiber transmission length as much as possible, or apply multiple pump sources. Strong impact, its performance is limited to a certain extent; at the same time, the range of objects used is narrow.

Contents of the invention

The invention provides a stimulated Raman scattering effect-suppressed fiber laser based on a tilted grating, which solves the technical problems in the prior art that the measures for suppressing the fiber laser are complicated, the process requirements are high, the performance is limited, and the scope of applicable objects is narrow.

In order to solve the above technical problems, the present invention provides a stimulated Raman scattering effect-suppressed fiber laser based on a tilted grating, including:

a pumping source for outputting pumping light;

gain fiber;

a pump coupling device, connected to the pump source and the gain fiber, for coupling the pump light into the gain fiber;

A reflection component, connected to the gain fiber, reflects and couples the pump light output by the gain fiber into the gain fiber;

A tilted grating structure, connected to the gain fiber, is used to deplete the energy of the stimulated Raman scattering wave exceeding the threshold wavelength.

Further, the tilted grating structure includes: tilted fiber grating;

The tilted fiber grating is welded to one end of the gain fiber.

Further, the tilted grating structure includes: a tilted grating written in the gain fiber.

Further, the reflection component includes: a total reflection fiber grating and a partial reflection fiber grating;

The total reflection fiber grating is welded at the input end of the gain fiber, and the partial reflection fiber grating is welded at the output end of the gain fiber.

Further, the pump coupling device includes: a first coupler and a second coupler;

The first coupler is connected between the total reflection fiber grating and the input end of the gain fiber;

The second coupler is connected between the partially reflecting fiber grating and the output end of the gain fiber;

The first coupler and the second coupler are respectively connected to the pumping source.

Further, the fiber laser also includes: an isolator;

The isolator is connected to the input end of the pump coupling device, and is used for suppressing reflection signals in the transmission fiber.

Further, the fiber laser also includes: a circulator;

The first end of the circulator is connected to the output end of the gain fiber, the second end of the circulator is connected to the reflection component; the third end of the circulator is connected to the pump coupling device;

Wherein, the pump light output by the gain fiber is input through the first end of the circulator, reflected by the reflection component, and enters the pump coupling device from the third end.

Further, the fiber laser also includes: an isolator;

The isolator is connected to the output end of the gain fiber, and is used for suppressing reflection signals in the transmission fiber.

One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

The stimulated Raman scattering effect-suppressed fiber laser based on the tilted grating provided in the embodiment of the present application, by setting the tilted grating structure, performs targeted screening for the pump light energy and the initial signal light energy, that is, sets the SRS threshold condition: The light below a specific wavelength is screened and reflected into the cavity to realize positive feedback, realize gain accumulation, and finally output a laser signal; when a wave above a specific wavelength passes through a tilted grating structure or device, due to wavelength matching, the fundamental mode transmitted in the fiber core The energy will be coupled with the cladding mode, resulting in an increase in its loss, so that the threshold condition of the SRS is no longer met, the suppression of the SRS is realized, and the pure output is achieved at a specific wavelength; thus, both SRS suppression and device performance are taken into account. On the other hand, the seamless connection between devices does not need to change its own materials and structures, and the maximum SRS suppression can be achieved on the basis of ensuring the performance of the original laser; through various parameters of the tilted grating, such as the grating length, The adjustability of modulation period, modulation depth, inclination, chirp, etc. makes it theoretically possible to deal with the SRS situation under different lasers, realize the suppression of SRS under the premise of ensuring the laser beam and output power to the greatest extent, and can adapt to various fiber lasers ; At the same time, the output characteristics of the fiber laser, such as polarization characteristics, can also be changed by modulating the structural parameters of the tilted fiber grating, which can meet the needs of various types of fiber lasers.

Description of drawings

Fig. 1 is a schematic structural diagram of a stimulated Raman scattering effect-suppressed fiber laser based on a tilted grating provided in Embodiment 1 of the present invention;

FIG. 2 is a schematic structural diagram of a stimulated Raman scattering effect-suppressed fiber laser based on a tilted grating provided in Embodiment 2 of the present invention;

3 is a schematic structural diagram of a stimulated Raman scattering effect-suppressed fiber laser based on a tilted grating provided in Embodiment 3 of the present invention;

FIG. 4 is a schematic structural diagram of a stimulated Raman scattering effect-suppressed fiber laser based on a tilted grating provided in Embodiment 4 of the present invention;

Fig. 5 is the OptiGrating simulation result of the inclination angle of the fiber laser provided by the embodiment of the present invention for the transmission spectrum;

Fig. 6 is the OptiGrating simulation result of the period of the fiber laser provided by the embodiment of the present invention for the transmission spectrum;

Fig. 7 is the OptiGrating simulation result of the length of the fiber laser provided by the embodiment of the present invention for the transmission spectrum.

detailed description

The embodiment of the present application solves the technical problems in the prior art that the fiber laser suppression measures are complicated, the process requirements are high, the performance is limited, and the scope of applicable objects is narrow by providing a stimulated Raman scattering effect suppressing fiber laser based on a tilted grating; The technical effect of suppressing the stimulated Raman scattering effect and improving the performance of the laser is achieved.

In order to better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solutions of the present application. , rather than limiting the technical solutions of the present application, the embodiments of the present application and the technical features in the embodiments can be combined without conflict.

In the following, four specific structural realization schemes are proposed for the laser structure.

Embodiment one

Referring to Figure 1, an embodiment of the present invention provides a stimulated Raman scattering effect-suppressed fiber laser based on a tilted grating, including:

a pumping source for outputting pumping light;

gain fiber 1;

A pump coupling device (3, 4), connected to the pump source and the gain fiber 1, for coupling the pump light into the gain fiber 1.

The reflective components (5, 6) are connected to the gain fiber 1, and reflect and couple the pump light output by the gain fiber 1 into the gain fiber 1.

The inclined grating structure 2 is connected with the gain fiber 1 and is used for losing the energy of the stimulated Raman scattering wave exceeding the threshold wavelength.

Specifically, the tilted grating structure includes: a tilted fiber grating; the tilted fiber grating is welded to one end of the gain fiber.

The reflection assembly includes: a total reflection fiber Bragg grating 5 and a partial reflection fiber Bragg grating 6; the total reflection fiber Bragg grating 5 is welded to the input end of the gain fiber 1, and the partial reflection fiber Bragg grating 6 is welded to the gain fiber 1 output.

The pump coupling device includes: a first coupler 3 and a second coupler 4 ; the first coupler 3 is connected between the total reflection fiber grating 5 and the input end of the gain fiber 1 .

The second coupler 4 is connected between the partially reflecting fiber grating 6 and the output end of the gain fiber 1 .

The first coupler 3 and the second coupler 4 are respectively connected to the pumping sources.

Further, the fiber laser further includes: an isolator 7; the isolator 7 is connected to the input end of the pump coupling device, and is used for suppressing reflection signals in the transmission fiber.

Embodiment two

Referring to FIG. 2 , this embodiment is based on the first embodiment, and makes a second solution for the structural form of the tilted grating 2 .

Specifically, the tilted grating structure includes: a tilted grating written in the gain fiber.

Other structures will not be repeated

The above two embodiments are cavity-shaped fiber lasers, and the following is an implementation scheme of a ring optical laser based on a tilted grating.

Embodiment Three

Referring to Figure 3, an embodiment of the present invention provides a stimulated Raman scattering effect-suppressed fiber laser based on a tilted grating, including:

a pumping source for outputting pumping light;

gain fiber;

A pump coupling device, connected to the pump source and the gain fiber, for coupling the pump light into the gain fiber.

The reflection component is connected with the gain fiber, and reflects and couples the pump light output from the gain fiber into the gain fiber.

A tilted grating structure, connected to the gain fiber, is used to deplete the energy of the stimulated Raman scattering wave exceeding the threshold wavelength.

Specifically, the tilted grating structure includes: a tilted fiber grating; the tilted fiber grating is welded to one end of the gain fiber.

The fiber laser also includes: a circulator;

The first end of the circulator is connected to the output end of the gain fiber, the second end of the circulator is connected to the reflection component; the third end of the circulator is connected to the pump coupling device;

Wherein, the pump light output by the gain fiber is input through the first end of the circulator, reflected by the reflection component, and enters the pump coupling device from the third end.

Further, the fiber laser also includes: an isolator;

The isolator is connected to the output end of the gain fiber, and is used for suppressing reflection signals in the transmission fiber.

Embodiment four

Referring to FIG. 4 , this embodiment is based on the third embodiment, and makes a second solution for the structure of the tilted grating.

Specifically, the tilted grating structure includes: a tilted grating written in the gain fiber.

The working process will be introduced in detail below.

Take the Raman scattering wavelength 1114nm as an example for illustration.

Pump source, 976nm LD output: provide stimulated radiation energy in Yb-doped fiber to generate stimulated radiation.

Ytterbium-doped fiber: Stimulated radiation gain medium, which provides the gain required for laser output.

Isolator: Suppresses the reflected signal in the transmission fiber to ensure the output quality of the laser.

Fiber Bragg Grating FBG: It only reflects the band centered on the Bragg wavelength of the FBG, and filters out the rest of the wavelengths.

Coupler: couple the external optical signal into the laser, or couple the laser signal in the laser out.

Tilted grating TFBG structure: It has a loss effect on the stimulated Raman scattering wavelength. By controlling the parameters such as inclination angle and grating period, it only acts on the Raman wavelength of 1114nm, and the LP01 mode under the stimulated Raman scattering wavelength of 1114nm Coupled into the loss in the cladding of the fiber to realize the function of suppressing the stimulated Raman scattering effect SRS.

Referring to Figure 5, Figure 6 and Figure 7, for the TFGB with 1.55um wavelength as the center wavelength, the OptiGrating simulation results of its inclination, period, and length for the transmission spectrum.

According to the simulation results, the transmission loss at the matching wavelength can be controlled according to the length, inclination, and grating period of the TFBG.

At the same time, when faced with the SRS effect in a large wavelength range, the chirp and apodization effects can also be introduced into the inclined grating structure to achieve the matching effect on the SRS wavelength and achieve the maximum suppression.

For an example of an ytterbium-doped stimulated Raman scattering effect-suppressed fiber laser based on a tilted grating, a theoretically feasible TFBG structure parameter for suppressing the SRS wavelength is as follows (there are many other structures that can be designed):

Cladding radius: 62.5um, core radius: 3.375um, grating length: 2cm, refractive index modulation depth: 0.0005

The working process of Yb-doped fiber laser based on tilted grating to suppress SRS effect based on TFBG is as follows (considering that the Yb-fiber length of Yb-doped fiber is fixed):

Specifically

When the pump light energy and the initial signal light energy are low (the SRS threshold condition is not reached):

When the 976nm pump light is injected into the laser, the 976nm optical signal in the ytterbium-doped fiber causes the ytterbium ion (Yb ³⁺ ) medium energy level in the fiber to undergo excited level transition radiation, producing a light source with a central wavelength of 1060nm. In the FBG structure, the 1060nm wavelength light is screened and reflected into the cavity to realize positive feedback and gain accumulation, and finally output the 1060nm laser signal at the half mirror end;

When the pump light energy and the initial signal light energy are high, it is necessary to achieve high power output (reaching the SRS threshold condition)

The laser energy of 1060nm is normally output, and the wavelength of the stimulated Raman scattering of 1114nm is due to the wavelength matching when passing through the TFBG structure or device, the fundamental mode energy transmitted in the fiber core will be coupled with the cladding mode, resulting in its The loss is increased, so that the threshold condition of SRS is no longer satisfied, the suppression of SRS is realized, and the output is as pure as possible under the wavelength of 1060nm;

The use of tilted fiber gratings as a separate SRS device for suppressing fiber lasers is simple and convenient to use, and can be directly welded or engraved; it is a characteristic of optical fiber devices, and can be changed by changing its structural parameters (tilt angle, grating, etc.) period, etc.), theoretically it can be applied to any kind of fiber laser (single-mode, multi-mode, different dopant ions), and minimally affects the performance of the laser itself;

It can effectively adjust the structural parameters of the tilted grating (grating tilt angle, grating constant, chirp, etc.) to adapt to changes in fiber lasers and external requirements (such as polarization characteristics, etc.), and has strong scalability and robustness.

One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

The stimulated Raman scattering effect-suppressed fiber laser based on the tilted grating provided in the embodiment of the present application, by setting the tilted grating structure, performs targeted screening for the pump light energy and the initial signal light energy, that is, sets the SRS threshold condition: The light below a specific wavelength is screened and reflected into the cavity to realize positive feedback, realize gain accumulation, and finally output a laser signal; when a wave above a specific wavelength passes through a tilted grating structure or device, due to wavelength matching, the fundamental mode transmitted in the fiber core The energy will be coupled with the cladding mode, resulting in an increase in its loss, so that the threshold condition of the SRS is no longer met, the suppression of the SRS is realized, and the pure output is achieved at a specific wavelength; thus, both SRS suppression and device performance are taken into account. On the other hand, the seamless connection between devices does not need to change its own materials and structures, and the maximum SRS suppression can be achieved on the basis of ensuring the performance of the original laser; through various parameters of the tilted grating, such as the grating length, The adjustability of modulation period, modulation depth, inclination, chirp, etc. makes it theoretically possible to deal with the SRS situation under different lasers, realize the suppression of SRS under the premise of ensuring the laser beam and output power to the greatest extent, and can adapt to various fiber lasers ; At the same time, the output characteristics of the fiber laser, such as polarization characteristics, can also be changed by modulating the structural parameters of the tilted fiber grating, which can meet the needs of various types of fiber lasers.

Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements without departing from the spirit and scope of the technical solution of the present invention shall be covered by the claims of the present invention.

Claims (8)

1. a kind of stimulated raman scattering suppressive optical fiber laser based on oblique raster, it is characterised in that include：

Pumping source, for exporting pump light；

Gain fibre；

Pump coupling device, is connected with the pumping source and the gain fibre, for the coupling pump light is entered described Gain fibre；

Reflection subassembly, is connected with the gain fibre, and the pump light reflection coupling that gain fibre is exported is entered the gain fibre；

Oblique raster structure, is connected with the gain fibre, exceeds the energy of the stimulated Raman scattering ripple of threshold wave-length for loss Amount.

2. the stimulated raman scattering suppressive optical fiber laser based on oblique raster as claimed in claim 1, its feature It is that the oblique raster structure includes：Inclined optical fiber grating；

The inclined optical fiber grating welding is in described gain fibre one end.

3. the stimulated raman scattering suppressive optical fiber laser based on oblique raster as claimed in claim 1, its feature It is that the oblique raster structure includes：The oblique raster being scribed in the gain fibre.

4. the stimulated raman scattering suppressive optical-fiber laser based on oblique raster as described in any one of claims 1 to 3 Device, it is characterised in that the reflection subassembly includes：Total reflection fiber grating and part reflection fiber grating；

Input of the total reflection fiber grating welding in the gain fibre, part reflection fiber grating welding is in institute State gain fibre output end.

5. the stimulated raman scattering suppressive optical fiber laser based on oblique raster as claimed in claim 4, its feature It is that the pump coupling device includes：First coupler and the second coupler；

First coupler is connected between the total reflection fiber grating and the gain fibre input；

Second coupler is connected between the part reflection fiber grating and the gain fibre output end；

First coupler and second coupler are connected with the pumping source respectively.

6. the stimulated raman scattering suppressive optical fiber laser based on oblique raster as claimed in claim 4, its feature It is that the optical fiber laser also includes：Isolator；

The isolator is connected with the input of the pump coupling device, for suppressing the reflected signal in Transmission Fibers.

7. the stimulated raman scattering suppressive optical-fiber laser based on oblique raster as described in any one of claims 1 to 3 Device, it is characterised in that the optical fiber laser also includes：Circulator；

The circulator first end is connected with the gain fibre output end, the second end of the circulator and the reflection subassembly phase Even；The 3rd end of the circulator is connected with the pump coupling device；

Wherein, the pump light of the gain fibre output is input into via the first end of the circulator, anti-by the reflection subassembly Penetrate, the pump coupling device is entered from the 3rd end.

8. the stimulated raman scattering suppressive optical fiber laser based on oblique raster as claimed in claim 7, its feature It is that the optical fiber laser also includes：Isolator；

The isolator is connected with the output end of the gain fibre, for suppressing the reflected signal in Transmission Fibers.