WO2017147775A1

WO2017147775A1 - Parallelly integrated optical fiber bragg grating, manufacturing method therefor, and manufacturing apparatus therefor

Info

Publication number: WO2017147775A1
Application number: PCT/CN2016/075138
Authority: WO
Inventors: 廖常锐; 王义平; 王侨
Original assignee: 深圳大学
Priority date: 2016-03-01
Filing date: 2016-03-01
Publication date: 2017-09-08

Abstract

A parallelly integrated optical fiber Bragg grating, manufacturing method therefor, and manufacturing apparatus therefor. The optical fiber grating comprises a solid-core optical fiber (1), wherein a plurality of optical fiber Bragg gratings (104) with different periods is written in a fiber core (103) of the solid-core optical fiber (1) along the axial direction of the optical fiber, and the gratings (104) are spaced apart by a particular distance. When the optical fiber gratings are manufactured, the moving speed of the optical fiber is controlled by means of a three-dimensional mobile platform (9), thereby implementing the writing, in the optical fiber core (103), of a plurality of optical fiber Bragg gratings (104) with parameters set by a user. The intervals between the gratings (104) are adjusted by means of the three-dimensional mobile platform (9) to prevent crosstalk among the gratings (104). This grating provides a good solution for a multi-wavelength optical fiber grating. The manufacturing method for a parallelly integrated optical fiber Bragg grating is simple and features low costs; optical fiber Bragg gratings obtained thereby have high mechanical strength and stable performance, and can be well applied in the field of optical fiber communications, optical fiber sensing, and optical fiber lasers.

Description

Parallel integrated fiber Bragg grating and manufacturing method and device thereof

Technical field

The present invention relates to the field of optical fiber technologies, and in particular, to a parallel integrated fiber Bragg grating, a manufacturing method thereof, and a manufacturing device.

Background technique

Multi-wavelength fiber grating is a new type of fiber optic device that has emerged in recent years. Its application range has covered many fields such as communication, sensing, laser and biomedicine. Multi-wavelength fiber gratings have developed so rapidly because of their unique wavelength selectivity.

From Qingge For the first time, Mao et al. used a plurality of fiber gratings with different center wavelengths to form multi-wavelength fiber gratings. The preparation method and theoretical analysis of multi-wavelength fiber gratings have become a hot research topic. There are many ways to write multi-wavelength fiber gratings, such as paralleling ordinary fiber gratings to form multi-wavelength gratings, and writing multi-wavelength gratings on special fibers (microstructured fibers, multi-mode fibers, birefringent fibers, etc.). Both require expensive phase masks and special fibers. At present, the main method for fabricating multi-wavelength fiber gratings is to use a phase mask method to write multi-wavelength fiber gratings on a special fiber. When this method is used, the center wavelength of the grating is limited by the phase mask, and special fiber needs to be purchased. This greatly increases the cost of writing multi-wavelength fiber gratings.

technical problem

The technical problem to be solved by the present invention is to provide a parallel integrated fiber Bragg grating, a manufacturing method thereof, and a manufacturing device, which do not use a phase mask, but write a parallel integrated fiber Bragg grating on a solid fiber.

Technical solution

The present invention is implemented as follows:

A parallel integrated fiber Bragg grating comprises a solid fiber. The core of the solid fiber is written with a plurality of fiber Bragg gratings with different periods along the fiber axis, and the gratings are spaced apart from each other by a certain distance.

Further, the grating has a length ranging from 500 micrometers to 2 centimeters.

Further, the gratings are parallel to each other.

A fabrication apparatus for fabricating any of the above-described fiber Bragg gratings, comprising:

Femtosecond laser, laser energy regulator, shutter device, CCD camera, dichroic mirror, objective lens, three-dimensional mobile platform, fiber coupler, detection light source, spectrometer;

The three-dimensional mobile platform is used for straightening and fixing a solid fiber to be processed, and can drive the solid fiber to move in three directions of X, Y, and Z according to a set speed, wherein the X direction is an optical fiber axis. The Z direction is an optical axis direction of the objective lens, and the Y direction is a direction perpendicular to the X direction and the Z direction;

The laser light emitted by the femtosecond laser is adjusted by the laser energy adjuster, reflected by the dichroic mirror to the objective lens, and then focused by the objective lens, and the laser can be adjusted by adjusting the position of the solid fiber. The focus is located within the core of the solid fiber;

The detecting light source is connected to the solid fiber through the fiber coupler, and the detecting light emitted by the detecting light source is coupled to the solid fiber through the fiber coupler;

The spectrometer is configured to detect a transmission spectrum and/or a reflection spectrum of the detection light after passing through the solid core fiber;

The shutter device is disposed in an optical path of the laser for controlling a time interval during which the laser irradiates the solid fiber and a duration of each exposure;

The CCD camera is configured to acquire an image of the solid fiber through the dichroic mirror and the objective lens.

Further, the laser energy conditioner comprises a half wave plate and a granule prism, and the laser light emitted by the femtosecond laser passes through the half wave plate and enters the granule prism.

Further, the shutter device is disposed in an optical path between the laser energy conditioner and the dichroic mirror.

Further, the objective lens is an oil-immersed microscope objective lens having a numerical aperture value of 1.25 and an oil immersion liquid having an incidence of 1.445.

Further, the laser has a wavelength of 800 nm, a pulse frequency of 1 kHz, a pulse width of 100 femtoseconds, and an energy range of 50 nanojoules to 180 nanojoules.

A method of fabricating a fiber Bragg grating as described above using the fabrication apparatus as described above, comprising the steps of:

Step 1: Stretching and fixing the solid fiber of the peeling coating layer on the three-dimensional moving platform, and positioning the core of the solid fiber to the focus position of the laser emitted by the femtosecond laser by using the three-dimensional moving platform ;

Step 2: using the laser light emitted by the femtosecond laser to write a first fiber Bragg grating point by point along the fiber axis in the core of the solid fiber;

Step 3: moving the solid fiber along the optical fiber by a predetermined distance through a three-dimensional moving platform, and then writing the next fiber Bragg grating in the same manner;

Step 4: Repeat step 3 until all fiber Bragg gratings have been written.

Further, when each fiber Bragg grating is written, the transmission spectrum and/or the reflection spectrum of the obtained grating are monitored in real time by a spectrometer.

Beneficial effect

Compared with the prior art, the invention does not need to adopt an expensive phase mask, and the position of the solid fiber is controlled by a precise three-dimensional moving platform, so that multiple cores are parallel and spaced apart in the core of the solid fiber. The gratings of different periods are controlled by a three-dimensional moving platform to ensure that there is no crosstalk between the gratings. This grating provides a good solution for multi-wavelength fiber gratings. The invention provides a parallel integrated fiber Bragg grating, which has the advantages of simple preparation method and low cost, and the obtained fiber grating has high mechanical strength and stable performance, and has good application value in the fields of optical fiber communication, optical fiber sensing and fiber laser.

DRAWINGS

Figure 1: Schematic view of a parallel integrated fiber Bragg grating provided by the present invention;

2 is a schematic cross-sectional view of a parallel integrated fiber Bragg grating provided by the present invention;

3 is a schematic structural view of a device for fabricating a parallel integrated fiber Bragg grating provided by the present invention;

4 is a schematic flow chart of a method for fabricating a parallel integrated fiber Bragg grating provided by the present invention;

Figure 5: Schematic diagram of the reflection spectrum for each grating produced during the fabrication of a parallel integrated fiber Bragg grating;

Figure 6: Schematic diagram of the transmission spectrum for each grating produced during the fabrication of a parallel integrated fiber Bragg grating.

Embodiments of the invention

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

As shown in FIG. 1, the parallel integrated fiber Bragg grating includes a solid fiber 1 in which a plurality of fiber Bragg gratings 104 are written along the fiber axis in the core 103 of the solid fiber 1, each grating 104 having a different period. Each of the gratings 104 is parallel to each other and spaced apart from each other by a certain distance. Each grating has a length ranging from 500 microns to 2 cm. As can be seen in Figure 1, there are three gratings 104 in the core 103 which are parallel to each other and spaced apart to ensure that no crosstalk occurs between the gratings 104. Each of the gratings 104 can also be formed in parallel with each other to form a plurality of layers, each layer having at least two gratings 104. In Figures 1 and 2, 101 is a coating layer and 102 is a cladding layer.

3 shows a fabrication apparatus for fabricating the above-described parallel integrated fiber Bragg grating. As shown in FIGS. 1, 2, and 3, the apparatus includes a femtosecond laser 2, a laser energy conditioner, a shutter device 5, a CCD camera 6, and a dichroic mirror. 7. Objective lens 8, three-dimensional moving platform 9, fiber coupler 10, detection light source 11, and spectrometer 12.

The three-dimensional mobile platform 9 is used for straightening and fixing the solid fiber 1 to be processed, and can drive the solid fiber 1 to move in three directions of X, Y and Z according to the set speed, wherein the X direction is the solid fiber 1 In the axial direction, the movement speed of the solid fiber 1 in the X direction can be controlled by the three-dimensional moving platform 9 to control the period of the produced grating 104, and the Z direction is the optical axis direction of the objective lens, and after writing a layer of the grating 104, through the three-dimensional The mobile platform 9 controls the solid fiber 1 to move a certain distance in the Z direction to write another layer of the grating 104, and the Y direction is a direction perpendicular to the X direction and the Z direction. After writing a grating 104, it is controlled by the 3D mobile platform 9. After the solid fiber 1 is moved along the Y axis by a set distance, the next grating can be written, and the distance moved along the Y axis is the grating pitch.

The laser light emitted by the femtosecond laser 2 is adjusted by the laser energy conditioner, and then reflected by the dichroic mirror 7 to the objective lens 8, and then focused by the objective lens 8, and then the focus of the laser fiber 1 is placed on the solid fiber by adjusting the position of the solid fiber 1. 1 inside the core. The laser has a wavelength of 800 nm, a pulse frequency of 1 kHz, a pulse width of 100 femtoseconds, and an energy range of 50 nanojoules to 180 nanojoules. The laser energy conditioner can adjust the laser energy in this energy range. The laser energy conditioner specifically includes a half wave plate 3 and a granule prism 4, and the laser light emitted from the femtosecond laser 2 passes through the half wave plate 3 and enters the granule prism 4, and is emitted from the granule prism 4, and then incident on the objective lens 8. . The incident laser energy intensity can be adjusted by rotating the half-wave plate 3. The objective lens 8 is an oil immersion objective lens having a numerical aperture value of 1.25. The oil immersion liquid is similar to the fiber material, and the oil immersion liquid has a refractive index of 1.445. Adjusting the position of the solid fiber 1 by the three-dimensional moving platform 9 accurately positions the laser focus into the core of the solid fiber 1 where the grating 104 needs to be prepared.

To perform real-time monitoring of the transmitted/reflected spectrum of the resulting grating 104 during the preparation of the grating 104, the fabrication apparatus further includes a detection source 11 and a spectrometer 12. The detecting light source 11 is connected to the solid fiber 1 through the fiber coupler 10, and the detecting light emitted from the detecting light source 11 is coupled to the solid fiber 1 via the fiber coupler 10. The spectrometer 12 is for detecting a transmission spectrum and/or a reflection spectrum of the detection light after passing through the solid core fiber 1. When the spectrometer 12 is coupled to the head end of the solid fiber 1 through the fiber coupler 10, the resulting reflection spectrum of each of the gratings 104 can be detected, when the spectrometer 12 is connected to the end of the solid fiber 1 (shown in broken lines in FIG. 3) At time, the transmission spectrum of each of the produced gratings 104 can be detected. The fiber coupler 10 can employ a fiber coupler with an insertion loss of 3 dB.

The shutter device 5 is disposed in the optical path of the laser, specifically in the optical path between the laser energy adjuster and the dichroic mirror 7, for controlling the time interval during which the laser irradiates the solid fiber 1 and the duration of each illumination. The CCD camera 6 is configured to acquire an image of the solid fiber 1 through the dichroic mirror 7 and the objective lens 8. The image of the laser focus and the nearby position in the solid fiber 1 can be observed and collected by the CCD camera 6 to facilitate the observation of the grating 104 fabrication process. FIG. 4 is a flowchart showing a method for fabricating the above-mentioned fiber grating structure by using the above-mentioned manufacturing device. As shown in FIG. 1, 2, 3 and 4, the method specifically includes the following steps:

Step 1: Straightening and fixing the solid fiber 1 stripping the coating layer on the three-dimensional moving platform 9, and positioning the core of the solid fiber 1 to the focus of the laser emitted by the femtosecond laser 2 by using the three-dimensional moving platform 9. position. Before writing the grating 104, it is necessary to adjust the laser focus position, the laser energy, the moving speed of the three-dimensional moving platform 9, and the like in advance.

Step 2: Using the laser light emitted by the femtosecond laser 2, the first fiber Bragg grating is written point by point along the fiber axis in the core of the solid fiber 1.

Step 3: The solid fiber 1 is moved radially along the fiber by a predetermined distance through the three-dimensional moving platform 9, and then the next fiber Bragg grating 104 is written in the same manner. After each writing of a grating 104, the solid fiber 1 is moved by the three-dimensional moving platform 9 to the initial writing position when the grating 104 is written, and then the fiber is radially moved to write the next grating 104. The radial movement distance is the grating pitch, and the pitch of each grating 104 is generally set to 2 micrometers. Of course, after writing a grating 104, the solid fiber 1 can be directly returned to the initial writing position, and the solid fiber 1 can be directly moved along the optical fiber by a set distance, and then the next grating 104 is written. When the next grating 104 is written, the moving direction of the solid fiber 1 in the X direction will be opposite to that when the grating 104 is written, so that the respective gratings 104 have a parallel positional relationship.

Step 4: Repeat step 3 until all fiber Bragg gratings 104 have been written. The completed gratings 104 are parallel to each other and spaced apart by a set distance. If a multi-layered fiber Bragg grating 104 is to be produced, after the grating 104 is prepared, the optical fiber 1 needs to be moved by a set distance in the Z-axis direction by the three-dimensional moving platform 9, and another layer of the grating 104 is prepared.

When each of the gratings 104 is written, the reflectance spectrum and the transmission spectrum of each of the gratings 104 produced by the recording are recorded in real time by the spectrometer 12. The three spectra from top to bottom in Fig. 5 are the reflection spectra when three gratings 104 are produced, respectively, and the three spectra from top to bottom in Fig. 6 are the transmission spectra when three gratings 104 are produced, respectively. As can be seen from Figures 5 and 6, no crosstalk occurs between the gratings 104, and the spectra of the gratings 104 are not affected by each other.

Compared with the conventional preparation method, the manufacturing method of the invention is flexible and can be applied to any type of solid core fiber 1. By adjusting parameters such as laser energy, grating period, grating length and the like, the writing efficiency of the fiber grating 104 can be greatly improved, the high-quality fiber grating 104 can be obtained, and the grating 104 can have stable mechanical strength and performance. The parallel integrated fiber Bragg grating 104 produced by the invention has good application value in the fields of optical fiber communication, optical fiber sensing and fiber laser, such as: (1) Filter based on parallel integrated fiber Bragg grating 104: fiber grating 104 As a fiber filter, a parallel integrated fiber Bragg grating 104 can be used as a multi-wavelength fiber filter; (2) a temperature and strain sensor based on a parallel integrated fiber Bragg grating 104: for example, one of the fiber gratings 104 fabricated in the present invention Sample test, temperature sensitivity is 12 pm / ̊ C, strain sensitivity can reach 1 pm / μ ε; (3) wavelength selection device based on multi-wavelength fiber grating 104: one of the samples of the parallel integrated fiber Bragg grating 104 fabricated by the present invention High temperature test, after 12 hours at 1000 ̊C, the fiber grating 104 has no degradation and has very good high temperature stability, so it can be used in high power fiber laser systems.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims

A parallel integrated fiber Bragg grating is characterized in that it comprises a solid fiber, and a fiber Bragg grating with different periods is written along the fiber axis of the core of the solid fiber, and the gratings are spaced apart from each other by a certain distance.
The fiber Bragg grating of claim 1 wherein said grating has a length in the range of 500 microns to 2 cm.
The fiber Bragg grating of claim 1 wherein the gratings are parallel to one another.
A device for fabricating a fiber Bragg grating according to any of claims 1-3, comprising:

Femtosecond laser, laser energy regulator, shutter device, CCD camera, dichroic mirror, objective lens, three-dimensional mobile platform, fiber coupler, detection light source, spectrometer;

The three-dimensional mobile platform is used for straightening and fixing a solid fiber to be processed, and can drive the solid fiber to move in three directions of X, Y, and Z according to a set speed, wherein the X direction is an optical fiber axis. The Z direction is an optical axis direction of the objective lens, and the Y direction is a direction perpendicular to the X direction and the Z direction;

The laser light emitted by the femtosecond laser is adjusted by the laser energy adjuster, reflected by the dichroic mirror to the objective lens, and then focused by the objective lens, and the laser can be adjusted by adjusting the position of the solid fiber. The focus is located within the core of the solid fiber;

The detecting light source is connected to the solid fiber through the fiber coupler, and the detecting light emitted by the detecting light source is coupled to the solid fiber through the fiber coupler;

The spectrometer is configured to detect a transmission spectrum and/or a reflection spectrum of the detection light after passing through the solid core fiber;

The shutter device is disposed in an optical path of the laser for controlling a time interval during which the laser irradiates the solid fiber and a duration of each exposure;

The CCD camera is configured to acquire an image of the solid fiber through the dichroic mirror and the objective lens.
The fabricating apparatus according to claim 4, wherein said laser energy conditioner comprises a half wave plate and a granule prism, and said laser emitted from said femtosecond laser passes through said half wave plate and enters said granitic prism .
The fabrication apparatus according to claim 4, wherein said shutter means is disposed in an optical path between said laser energy conditioner and said dichroic mirror.
The fabrication apparatus according to claim 4, wherein said objective lens is an oil-immersed microscope objective lens having a numerical aperture value of 1.25 and an oil immersion liquid having an incidence of 1.445.
The fabrication apparatus according to claim 4, wherein said laser has a wavelength of 800 nm, a pulse frequency of 1 kHz, a pulse width of 100 femtoseconds, and an energy range of 50 nanojoules to 180 nanojoules.
A method of fabricating a fiber Bragg grating according to any one of claims 1 to 3, comprising the steps of:

Step 1: Stretching and fixing the solid fiber of the peeling coating layer on the three-dimensional moving platform, and positioning the core of the solid fiber to the focus position of the laser emitted by the femtosecond laser by using the three-dimensional moving platform ;

Step 2: using the laser light emitted by the femtosecond laser to write a first fiber Bragg grating point by point along the fiber axis in the core of the solid fiber;

Step 3: moving the solid fiber along the optical fiber by a predetermined distance through a three-dimensional moving platform, and then writing the next fiber Bragg grating in the same manner;

Step 4: Repeat step 3 until all fiber Bragg gratings have been written.
The method according to claim 9, wherein the transmission spectrum and/or the reflection spectrum of the produced grating are monitored in real time by a spectrometer when writing the respective fiber Bragg gratings.