WO2018129845A1

WO2018129845A1 - Method for manufacturing fiber grating, and device and method for monitoring fiber grating

Info

Publication number: WO2018129845A1
Application number: PCT/CN2017/084907
Authority: WO
Inventors: 王英; 邓蜜; 王义平; 廖常锐
Original assignee: 深圳大学
Priority date: 2017-01-16
Filing date: 2017-05-18
Publication date: 2018-07-19
Also published as: CN106526742A

Abstract

A method for manufacturing a fiber grating, and a device and method for monitoring a fiber grating, for use in resolving the problem of low mechanical strength of a fiber grating manufactured by means of an existing technology. The method for manufacturing a fiber grating comprises: filling a preselected air hole of a perforated fiber (33) with a liquid having a high thermal expansion coefficient (S101); and heating a preset area of the perforated fiber (33) filled with the liquid to make the air hole filled with the liquid expand due to thermal expansion of the liquid, so that an air hole which is not filled with a liquid is pressed so as to obtain a fiber grating having a self-expansion structure (S102).The method or device for manufacturing a fiber grating is simple; moreover, the manufactured fiber grating has high mechanical strength and controllable expansion positions, can be widely applied, and is not easy to damage.

Description

Fiber grating preparation method, monitoring device and monitoring method

Technical field

The invention relates to the technical field of fiber grating manufacturing, in particular to a fiber grating preparation method, a monitoring device and a monitoring method.

Background technique

Photonic Crystal Fiber (PCF) The photonic crystal fiber is characterized by a periodic microporous structure, and the photonic crystal fiber is also called a porous fiber or a microstructured fiber. Compared with conventional optical fiber, PCF has the advantages of no cut-off single mode, high nonlinearity, large mode area, and controllable dispersion. Therefore, PCF can be used not only as a better optical transmission medium than conventional optical fibers, but also for making A variety of new photonic devices; long-period fiber gratings (LPFG) are sensitive to the external environment and can be widely used in communications, sensing, laser, and biomedical applications. Therefore, the preparation of a long-period fiber grating in a photonic crystal fiber combines the characteristics of the photonic crystal fiber with the characteristics of the long-period fiber grating, thereby greatly improving the performance of the PCF, and simultaneously solving the parameter crosstalk and the cut-off list of the original LPFG. Problems such as mode can effectively improve the quality of raster writing.

At present, there are various methods for preparing LPFG on PCF, and the market mainly uses a low-cost CO2 laser irradiation method. The mechanism of forming LPFG in PCF by CO2 laser irradiation method is to use residual stress release and physical deformation. Based on the residual stress release method, the CO2 laser is used as the heat shock element, so that the PCF cladding air hole is thermally collapsed and the periodic structure is destroyed. And get LPFG. However, due to the collapse of the air hole, the insertion loss of the incident light is increased, and if the physical deformation is produced by the taper or collapse of the CO2 heat source cycle, although a large refractive index modulation can be generated, the pore collapse or the taper melt deformation After the mechanical strength of the fiber is weakened, it is easy to break. Therefore, the fiber grating prepared by the CO2 laser irradiation method has low mechanical strength.

technical problem

The invention provides a fiber grating preparation method, a monitoring device and a monitoring method, aiming at solving the problem of low mechanical strength of the fiber grating produced by the prior art.

Technical solution

In order to solve the above technical problem, the present invention provides a method for fabricating a fiber grating, the method comprising the following steps:

Filling a liquid having a high coefficient of thermal expansion into a preselected air hole of the apertured fiber;

Presetting a predetermined area of the apertured optical fiber that has been filled with the liquid such that the air hole that has been filled with the liquid expands due to thermal expansion of the liquid to cause squeezing of the air hole that is not filled with the liquid Pressing, a fiber grating having a self-expanding structure is obtained.

Further, the step of heating the predetermined area of the apertured optical fiber that has been filled with the liquid includes:

In the axial direction of the apertured optical fiber that has been filled with the liquid, divided into N sub-band aperture fibers according to a preset grating pitch, where N is a positive integer;

The predetermined area of each of the sub-perforated fibers is sequentially heated.

Further, the sequentially heating the preset area of each of the sub-perforated optical fibers comprises: sequentially heating the preset area of the sub-belted optical fiber M times, wherein M is a positive integer.

Further, in the process of heating the predetermined region of the apertured optical fiber that has been filled with the liquid, the heating temperature is adjusted based on a spectral signal obtained by monitoring the fiber grating preparation process.

Further, the preselected air holes are any one or more air holes of the apertured optical fiber.

The present invention also provides a fiber grating monitoring device, the device comprising: a first single mode fiber, a second single mode fiber, a light source, and a spectrometer;

One end of the first single-mode optical fiber is fused to one end of the optical fiber to be monitored, and the other end of the first single-mode optical fiber is connected to the light source;

One end of the second single-mode fiber is fused to the other end of the optical fiber to be monitored, and the other end of the second single-mode fiber is connected to the spectrometer;

Wherein, the preselected air holes of the optical fiber to be monitored have been filled with a liquid having a high thermal expansion coefficient.

Further, the monitoring device further includes a heating device: the heating device is configured to heat the optical fiber to be monitored to make the air of the liquid to be inspected filled with the liquid The pores expand due to thermal expansion of the liquid to cause extrusion of air holes that are not filled with the liquid, resulting in a fiber grating having a self-expanding structure.

Further, in the process of heating the optical fiber to be monitored, the heating device repeatedly heats the preset area of the optical fiber to be monitored M times, wherein M is a positive integer;

And adjusting the heating temperature based on the spectral signal obtained by monitoring the fiber grating preparation process.

The invention also provides a fiber grating monitoring method, which is applied to the above-mentioned fiber grating monitoring device, and the monitoring method comprises:

During heating of the apertured optical fiber to be monitored, the light emitted by the light source is transmitted to the heated optical fiber to be monitored via the first single mode fiber to generate a spectrum of the optical fiber to be monitored. Signaling and transmitting the spectral signal to the spectrometer via the second single mode fiber;

The spectrometer monitors the spectral signal in real time during the heating of the optical fiber to be monitored, and determines whether the optical fiber to be monitored reaches the preset fiber grating standard according to the spectral signal;

Wherein the apertured optical fiber to be monitored is a perforated optical fiber in which a liquid having a high thermal expansion coefficient has been filled in the preselected air hole.

And adjusting the heating temperature based on the spectral signal.

Beneficial effect

Compared with the prior art, the invention has the following advantages:

The present invention fills a liquid having a high coefficient of thermal expansion into a preselected air hole of a perforated optical fiber; and heats a predetermined area of the perforated optical fiber that has been filled with the liquid so that the air hole that has been filled with the liquid The liquid expands by thermal expansion to cause extrusion of an air hole that is not filled with the liquid, resulting in a fiber grating having a self-expanding structure. The fiber grating is fabricated by the method or the device, and the method is simple, and the produced fiber grating has high mechanical strength, controllable expansion position, strong applicability and is not easy to be damaged.

DRAWINGS

1 is a flow chart of a method for fabricating a fiber grating according to a first embodiment of the present invention;

2 is a flow chart of a method for fabricating a fiber grating according to a second embodiment of the present invention;

3 is a schematic cross-sectional view of an optical fiber in a fiber grating preparation process according to an embodiment of the present invention;

4 is a schematic diagram of a preparation process of a long period fiber grating provided by an embodiment of the present invention;

5 is a schematic diagram of a fiber grating monitoring device according to an embodiment of the present invention;

6 is a schematic diagram of a fiber grating monitoring device according to a third embodiment of the present invention;

7 is a schematic diagram of a fiber grating monitoring device according to a fourth embodiment of the present invention;

FIG. 8 is a flowchart of a method for monitoring a fiber grating according to a fifth embodiment of the present invention.

Embodiments of the invention

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As a first embodiment of the present invention, as shown in FIG. 1, the present invention provides a method for fabricating a fiber grating, the method comprising the following steps:

Step S101: filling a liquid having a high coefficient of thermal expansion into a preselected air hole of the apertured optical fiber;

Step S102: heating a predetermined area of the apertured optical fiber that has been filled with the liquid, so that the air hole filled with the liquid expands due to thermal expansion of the liquid to the air that is not filled with the liquid. The holes are extruded to obtain a fiber grating having a self-expanding structure.

In summary, the method provided by the first embodiment of the present invention fills a liquid having a high coefficient of thermal expansion into a preselected air hole of the apertured optical fiber; and heats a predetermined area of the apertured optical fiber that has been filled with the liquid. So that the air hole that has been filled with the liquid expands due to thermal expansion of the liquid to squeeze the air hole that is not filled with the liquid, thereby obtaining a fiber grating having a self-expanding structure. The fiber grating is fabricated by the method or the device, and the high expansion coefficient liquid is filled inside the optical fiber, so the structure has a good integration feature, the expansion is naturally heated by the internal expansion, and the method is simple, and the method is simple; The grating has high mechanical strength, controllable expansion position, strong applicability and is not easy to be damaged; and the fiber grating preparation method, filled liquid with high thermal expansion coefficient, preselected air hole, heating temperature, heating times, heating method, heating device, heating The position can be adjusted, and the expansion size, shape and distribution of the air hole inside the fiber can be flexibly changed, so that the flexibility is higher; and the method for preparing the fiber grating is low in cost, good in repeatability, and greatly improves the preparation efficiency of the fiber grating.

As a second embodiment of the present invention, as shown in FIGS. 1 and 2, the present invention provides a method of fabricating a fiber grating, the method comprising the following steps:

Step S101: filling a liquid having a high coefficient of thermal expansion into a preselected air hole of the apertured optical fiber; wherein the fiber grating preparation can be achieved when a liquid having a high thermal expansion coefficient is uniformly filled in the preselected air hole of the apertured optical fiber The best effect.

Step S102: heating a predetermined area of the apertured optical fiber that has been filled with the liquid, so that the air hole filled with the liquid expands due to thermal expansion of the liquid to the air that is not filled with the liquid. The holes are extruded to obtain a fiber grating having a self-expanding structure. Wherein, the cladding of the apertured fiber of the heated predetermined region is first softened by heat.

In step S102, the step of heating the preset area of the apertured optical fiber that has been filled with the liquid includes:

Step S102-1: dividing into N sub-band aperture fibers according to a preset grating pitch in an axial direction of the apertured optical fiber that has been filled with the liquid, where N is a positive integer;

Step S102-2: heating a preset area of each of the sub-perforated fibers in sequence.

Among them, the purpose of steps S102-1 and S102-2 is to obtain a long-period fiber grating having a self-expanding structure. Presetting a preset grating pitch for a certain length of the apertured fiber, and heating only the sub-band aperture fiber of a predetermined grating pitch length for each heating, sequentially for each of the sub-band aperture fibers The predetermined area is heated to finally obtain a long-period fiber grating having a self-expanding structure.

It should be noted that, when the optical fiber to be monitored is heated, the heated preset area should be smaller than the preset grating pitch.

In the above heating process, the degree of expansion of the apertured fiber is changed by adjusting parameters such as heating temperature and number of heating in real time. Due to the different degrees of expansion, the structure inside the apertured fiber is different, so that the refractive index inside the apertured fiber is different, and the spectral signal of the apertured fiber is further different. Therefore, by monitoring the spectral signal of the apertured fiber. , to adjust the heating temperature and the number of heating parameters, and finally until a satisfactory fiber grating is obtained.

It should be noted that, in the method for preparing the fiber grating, the CO2 laser may be used as a heating device to heat the apertured optical fiber, or the optical fiber may be heated by a heating device such as an arc discharge or an oxyhydrogen flame or a heating method. . Moreover, the predetermined area during heating may be one-side local heating of the apertured optical fiber, that is, one-side heating, or symmetric heating, or rotational heating. In summary, different heating devices or different heating methods can produce fiber gratings with different self-expanding structures.

Further, the preselected air holes are any one or more air holes of the apertured fiber. The preselected air holes may be all air holes of the apertured fiber or inner ring air holes around the core of the apertured fiber. In the embodiment of the present invention, it is recommended to fill the inner ring air hole, because the fiber grating prepared by filling the inner ring air hole is optimal. As shown in FIG. 3, the preselected air holes of this embodiment are inner ring air holes of the photonic crystal fiber. Since the cladding of the photonic crystal fiber is composed of a multi-circle symmetrical hexagonal air hole from the core, and the closer to the air hole of the core, the refractive index modulation is stronger, and fewer grating points can be used. This results in a larger refractive index modulation, so the refractive index modulation effect caused by the inner ring air holes closest to the core is generally optimal. Therefore, the inner ring air hole is selected as the preselected air hole for preparing the fiber grating, and the writing efficiency of the fiber grating can be further improved. It can be seen from the above that when the air holes of other types of apertured fibers are selected, the air holes closer to the core can be arbitrarily selected, so that the prepared fiber grating is better. It is also within the scope of the present invention to fill any one or more of the air holes of the apertured fiber.

It should be noted that a liquid having a high coefficient of thermal expansion may have various options such as water, or alcohol. Since the degree of thermal expansion of each liquid having a high coefficient of thermal expansion is different, the air holes of the apertured optical fibers are also different in degree of thermal expansion due to the difference in the liquid they are filled in.

In this embodiment, the method is mainly based on photonic crystal fiber for fiber grating preparation, but the preparation method can be applied to various types of apertured fibers, such as solid photonic crystal fiber (PCF), hollow core photon. Crystal Fiber (PBF), Hollow Fiber (HOF), Suspended Fiber (SCF), etc.

In step S101, when a liquid having a high coefficient of thermal expansion is filled into a preselected air hole of the apertured fiber, the air holes of the apertured fiber can be selectively filled in a variety of ways. The following three filling methods are provided in this embodiment:

(1) Full filling method: A liquid having a high coefficient of thermal expansion is directly filled into all the air holes of the apertured optical fiber. It can be filled mainly by siphoning or by high-pressure pumping of liquid.

(2) Inner ring hole filling method: using a glass tube with a certain inner diameter, the inner diameter of the selected glass tube is larger than the inner diameter of the inner ring air hole of the photonic crystal fiber, and smaller than the inner diameter of the inner inner ring of the photonic crystal fiber, and the glass tube The optical fiber is fused to the photonic crystal fiber, so that the inner ring air hole is in communication with the outside, and the other air holes cannot be connected to the outside due to the blockage of the glass tube wall, and the liquid is filled by liquid siphoning or liquid high pressure pumping. In the inner ring air of the photonic crystal fiber, the inner ring air hole of the photonic crystal fiber is filled with a liquid having a high thermal expansion coefficient. As shown in FIG. 3, since the cladding of the photonic crystal fiber is composed of a plurality of symmetrical hexagonal air holes from the core, and the closer to the air hole of the core, the refractive index modulation is stronger. A small number of grating points can cause a large refractive index modulation, so the refractive index modulation effect caused by the inner ring air holes closest to the core is generally optimal. Therefore, the inner ring air hole is selected as the preselected air hole for preparing the fiber grating, and the writing efficiency of the fiber grating can be further improved.

(3) Air hole selective filling method: the single mode fiber is fused with the photonic crystal fiber to be filled, and the single mode fiber is cut by a cutter at a distance of 10-20 μm from the fusion point, and the cutting surface is selectively selected by a femtosecond laser. Opening the hole so that the opening position is connected to the outside, the remaining position is closed to the outside, and then the liquid is filled into the inner ring of the photonic crystal fiber by liquid siphoning or liquid high-pressure pumping to make the selected air hole of the photonic crystal fiber. Fill in a liquid with a high coefficient of thermal expansion.

In this embodiment, as shown in FIG. 4(a), the apertured fiber is selected as a photonic crystal fiber, and the preselected air hole is an inner ring hole of the photonic crystal fiber, and the liquid having a high thermal expansion coefficient is selected as water; As shown in Fig. 4(b), water is filled into the inner ring hole of the photonic crystal fiber, and the CO2 laser is used as a heating device to heat the holed fiber. The power of the CO2 laser heating device is 10w at maximum, and the power stability is 2 About %, the laser focused spot is 30-50μm, each grating pitch is set to 500μm, the photonic crystal fiber is divided into M sub-photonic crystal fibers per 500μm, and then each sub-photon is sequentially used by CO2 laser heating device. The crystal fiber is heated N times; as shown in Fig. 4(c), a long-period fiber grating having a self-expanding structure is obtained after heating. According to the simulation experiment, the grating pitch is generally set at 300-700μm, and the preparation effect of the fiber grating is optimal. A fiber grating having a self-expanding structure prepared by the method provided by the embodiment of the present invention has a wide range of applications, for example, (1) a filter and a gain flattener fabricated based on the fiber grating of the self-expanding structure. Among them, by adjusting the parameters of the preselected air holes, filling liquid, heating times, heating temperature, heating device and the like in the preparation process of the fiber grating, a filter with lower insertion loss and higher extinction ratio can be obtained. (2) Temperature, strain, pressure sensor, etc., produced by the fiber grating of the self-expanding structure. (3) A polarizer, a polarization interferometer, or the like fabricated based on the fiber grating of the self-expanding structure. Among them, the fiber grating prepared by the one-side preparation method has a very large polarization-dependent loss, and can be used as a polarizer, and two fiber grating cascades having a self-expanding structure can form a polarization interferometer.

In summary, the method provided by the second embodiment of the present invention fills a liquid having a high coefficient of thermal expansion into a preselected air hole of the apertured optical fiber; and heats a predetermined area of the apertured optical fiber that has been filled with the liquid. So that the air hole that has been filled with the liquid expands due to thermal expansion of the liquid to squeeze the air hole that is not filled with the liquid, thereby obtaining a fiber grating having a self-expanding structure. The fiber grating is fabricated by the method or the device, and the high expansion coefficient liquid is filled inside the optical fiber, so the structure has a good integration feature, the expansion is naturally heated by the internal expansion, and the method is simple, and the method is simple; The grating has high mechanical strength, controllable expansion position, strong applicability and is not easy to be damaged; and the fiber grating preparation method, filled liquid with high thermal expansion coefficient, preselected air hole, heating temperature, heating times, heating method, heating device, heating The position can be adjusted, and the expansion size, shape and distribution of the air hole inside the fiber can be flexibly changed, so that the flexibility is higher; and the method for preparing the fiber grating is low in cost, good in repeatability, and greatly improves the preparation efficiency of the fiber grating.

As a third embodiment of the present invention, as shown in FIG. 5 and FIG. 6, the present invention further provides a fiber grating monitoring device, comprising: a first single mode fiber 22, a second single mode fiber 44, and a light source. 11 and spectrometer 55;

One end of the first single mode fiber 22 is fused to one end of the apertured fiber 33 to be monitored, and the other end of the first single mode fiber 22 is connected to the light source 11;

One end of the second single mode fiber 44 is fused to the other end of the apertured fiber 33 to be monitored, and the other end of the second single mode fiber 44 is connected to the spectrometer 55;

Wherein, the preselected air holes of the apertured fiber 33 to be monitored have been filled with a liquid having a high coefficient of thermal expansion.

In summary, the monitoring device provided by the second embodiment of the present invention has a simple structure, and can monitor the change of the fiber grating at any time, thereby adjusting the preparation process of the fiber grating according to the change, so that the user can obtain a satisfactory fiber grating.

As a fourth embodiment of the present invention, as shown in FIG. 5 and FIG. 7, the present invention further provides a fiber grating monitoring device, comprising: a first single mode fiber 22, a second single mode fiber 44, and a light source. 11 and spectrometer 55;

Further, the monitoring device further includes a heating device 66 for heating the apertured optical fiber 33 to be monitored, so that the air hole of the apertured optical fiber 33 to be monitored that has been filled with the liquid is Expanded by thermal expansion to cause extrusion of air holes that are not filled with the liquid, resulting in a fiber grating having a self-expanding structure.

The first single-mode optical fiber 22 is used to transmit the light emitted by the light source 11 to the optical fiber 33 to be monitored; The light source 11 is configured to transmit light through the first single mode fiber 22 to the heated apertured fiber 33 to be monitored to generate a spectral signal for the apertured fiber 33 to be monitored; and the second single mode fiber 44 to The signal is transmitted to the spectrometer 55; the spectrometer 55 is configured to monitor the spectral signal in real time during the heating of the apertured fiber 33 to be monitored, and to determine whether the apertured fiber 33 to be monitored reaches the preset fiber grating standard based on the spectral signal.

Further, in the process of heating the apertured optical fiber 33 to be monitored, the heating device 66 repeatedly heats the preset area of the apertured optical fiber 33 to be monitored M times, wherein M is a positive integer;

It should be noted that the monitoring device provided by the embodiment of the present invention can be used as a device for preparing the fiber grating in the practical application, that is, during the preparation process of the fiber grating, while preparing, monitoring, and finally preparing the conformance. Fiber grating required by the user.

It should be noted that, generally, in the preparation process of the fiber grating, the preparation device and the monitoring device can be regarded as the same device, that is, during the preparation process, the fiber grating is monitored to meet the required fiber grating standard, thereby It is judged whether the fiber grating is successfully prepared.

In summary, the monitoring device provided by the fourth embodiment of the present invention has a simple structure, and can monitor the change of the fiber grating at any time, thereby adjusting the preparation process of the fiber grating according to the change, so that the user can obtain a satisfactory fiber grating.

As a fifth embodiment of the present invention, as shown in FIG. 8, the present invention further provides a fiber grating monitoring method, the monitoring method comprising:

Step S201: in the process of heating the optical fiber to be monitored, the light emitted by the light source is transmitted to the heated optical fiber to be monitored via the first single-mode optical fiber to make the hole to be monitored. The optical fiber generates a spectral signal and transmits the spectral signal to the spectrometer through the second single mode fiber;

Step S202: The spectrometer monitors the spectral signal in real time during the heating of the optical fiber to be monitored, and determines whether the optical fiber to be monitored reaches the preset fiber grating standard according to the spectral signal;

And adjusting the heating temperature based on the spectral signal.

In summary, the monitoring method provided by the fifth embodiment of the present invention can monitor the change of the fiber grating at any time, thereby adjusting the preparation process of the fiber grating according to the change, so that the user can obtain a satisfactory fiber grating.

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

Claims

A method for fabricating a fiber grating, characterized in that the method comprises the following steps:

Filling a liquid having a high coefficient of thermal expansion into a preselected air hole of the apertured fiber;

Presetting a predetermined area of the apertured optical fiber that has been filled with the liquid such that the air hole that has been filled with the liquid expands due to thermal expansion of the liquid to cause squeezing of the air hole that is not filled with the liquid Pressing, a fiber grating having a self-expanding structure is obtained.
The method according to claim 1, wherein the step of heating the predetermined area of the apertured optical fiber that has been filled with the liquid comprises:

In the axial direction of the apertured optical fiber that has been filled with the liquid, divided into N sub-band aperture fibers according to a preset grating pitch, where N is a positive integer;

The predetermined area of each of the sub-perforated fibers is sequentially heated.
The method according to claim 2, wherein the sequentially heating the predetermined area of each of the sub-perforated fibers comprises:

The predetermined area of the sub-perforated fiber is sequentially heated M times, wherein M is a positive integer.
The preparation method according to claim 1 or 2, wherein the step of heating the predetermined region of the apertured optical fiber filled with the liquid is based on monitoring the preparation process of the fiber grating The spectral signal adjusts the heating temperature.
The method according to claim 1, wherein the preselected air holes are any one or more of the air holes of the apertured fiber.
A fiber grating monitoring device, comprising: a first single mode fiber, a second single mode fiber, a light source, and a spectrometer;

One end of the first single-mode optical fiber is fused to one end of the optical fiber to be monitored, and the other end of the first single-mode optical fiber is connected to the light source;

One end of the second single-mode fiber is fused to the other end of the optical fiber to be monitored, and the other end of the second single-mode fiber is connected to the spectrometer;

Wherein, the preselected air holes of the optical fiber to be monitored have been filled with a liquid having a high thermal expansion coefficient.
The device of claim 6 wherein said device further comprises a heating device;

The heating device is configured to heat the optical fiber to be monitored, so that the air hole of the optical fiber to be monitored that has been filled with the liquid expands due to thermal expansion of the liquid, so as to The air holes that are not filled with the liquid are pressed to obtain a fiber grating having a self-expanding structure.
The device according to claim 7, wherein in the heating of the optical fiber to be monitored, the heating device repeatedly heats the preset area of the optical fiber to be monitored. Times, where M is a positive integer;

And adjusting the heating temperature based on the spectral signal obtained by monitoring the fiber grating preparation process.
A fiber grating monitoring method, characterized in that the method is applied to the fiber grating monitoring device according to any one of claims 6 to 8, the monitoring method comprising:

During heating of the apertured optical fiber to be monitored, the light emitted by the light source is transmitted to the heated optical fiber to be monitored via the first single mode fiber to generate a spectrum of the optical fiber to be monitored. Signaling and transmitting the spectral signal to the spectrometer via the second single mode fiber;

The spectrometer monitors the spectral signal in real time during the heating of the optical fiber to be monitored, and determines whether the optical fiber to be monitored reaches the preset fiber grating standard according to the spectral signal;

Wherein the apertured optical fiber to be monitored is a perforated optical fiber in which a liquid having a high thermal expansion coefficient has been filled in the preselected air hole.
The method according to claim 9, wherein in the heating of the optical fiber to be monitored, the heating device repeatedly heats the predetermined area of the optical fiber to be monitored M times. Where M is a positive integer;

And adjusting the heating temperature based on the spectral signal.