TWI418865B - Manufacturing method of a fiber grating and structure thereof - Google Patents

Description

Fiber grating manufacturing method and structure thereof

The invention relates to a method for fabricating a fiber grating and a structure thereof, in particular to a method for fabricating a fiber grating capable of improving measurement accuracy and a structure thereof.

The manufacturing method of the conventional fiber grating mainly comprises the following steps: (1) peeling off the coating layer of the outermost layer of an optical fiber in advance, so that the coating layer of the optical fiber is exposed; (2) Uniformly coating a photoresist layer on the coating layer and heating the photoresist layer; (3) partially exposing the photoresist layer to cause the exposed photoresist layer to generate a photopolymer chain, and the fiber of the fiber The core is simultaneously formed with a plurality of portions having different refractive indices; (4) removing the unexposed photoresist layer to form a protective layer on the coating layer of the optical fiber; (5) the pair is not subjected to the protective layer The covered cladding layer is etched to form a recess structure on the cladding layer of the optical fiber; (6) the protective layer is removed to obtain a fiber grating 9 having a sawtooth geometry.

Referring to FIG. 1 , the above-mentioned structure of the conventional fiber grating 9 is mainly formed by a core 91 having a coating layer 92 and a sawtooth portion 93 sequentially outward.

The conventional fiber grating 9 is usually fixed to a surface of an object to be tested by an adhesive, and the adhesive is easily filled into the space between the saw teeth 93, which is easy to cause. Conventionally, the measurement signal of the fiber grating 9 is weak, and even completely blocks the measurement signal, which seriously affects the measurement result; further, since the saw tooth portion 93 and the object to be tested have only a small contact area, The poor bonding strength between the conventional fiber grating 9 and the object to be tested is likely to cause damage or breakage of the conventional fiber grating 9.

For the above reasons, it is indeed necessary to further improve the above-described conventional fiber grating 9.

The object of the present invention is to improve the above disadvantages, and to provide a method for fabricating a fiber grating and a structure thereof, which can achieve the purpose of improving measurement accuracy.

The object of the present invention is to provide a method for fabricating a fiber grating and a structure thereof, which can achieve the purpose of improving the structural strength.

In order to achieve the foregoing object, the technical means and the achievable effects of the present invention include: a method for fabricating a fiber grating, the steps comprising: (1) pre-removing at least one fiber layer of the fiber And etching to reduce the thickness of the coating layer of the optical fiber to 10 to 125 μm; (2) forming a metal layer on a surface of the substrate by physical or chemical vapor deposition; (3) coating at least one surface of the metal layer a photoresist material to form at least one photoresist layer; (4) heating the photoresist layer to a glass transition temperature or higher to volatilize a solvent remaining in the photoresist layer and hardening the photoresist layer; (5) partial exposure The photoresist layer, and heating the photoresist layer to a temperature above the glass transition temperature after the exposure is completed; (6) removing the unexposed photoresist layer via a developing solution to develop the photoresist layer; (7) Fixing the optical fiber that completes step (1) above the photoresist layer that completes step (6); (8) coating another photoresist layer over the optical fiber and the photoresist layer, and the other photoresist layer Repeating the above steps (4) to (6), so that the two photoresist layers together form a sawtooth structure covering The outer surface of the optical fiber, and then performing the step (9); (9) heating the optical fiber of the step (8) and the photoresist layer on the outer surface of the optical fiber to volatilize the solvent in each of the photoresist layers, and let the photoresist The flow fills the void; (10) separating the photoresist layer of the outer surface of the optical fiber from the metal layer by using a separating liquid; and (11) covering a high polymer polymer on the outer surface of the optical fiber and filling the sawtooth A gap formed by the structure to form a protective layer.

A fiber grating structure comprises: an optical fiber having a core and a coating layer, the coating layer covering the outer peripheral surface of the core; and a plurality of photoresist layers covering the outer peripheral surface of the coating layer And a gap is formed between each of the photoresist layers; and a protective layer is coated on the outer peripheral surface of the cladding layer and fills the plurality of gaps.

The above and other objects, features and advantages of the present invention will become more <RTIgt; The method for fabricating the fiber grating of the first embodiment of the present invention comprises the following steps: a preset step S1, a metal layer forming step S2, a first photoresist forming step S3, a soft baking step S4, an exposure step S5, A developing step S6, a fiber fixing step S7, a second photoresist forming step S8, a hard baking step S9, a separating step S10, and a protective layer forming step S11. Through the above steps, in addition to effectively improving the measurement accuracy of the fiber grating, the structural strength of the fiber grating can be simultaneously improved.

Referring to FIG. 2 and FIG. 3, the preset step S1 of the first embodiment of the present invention removes at least one fiber layer 11 of at least one optical fiber 1 to expose one of the optical fibers 1 to the exposed layer 12; The thickness of the cladding layer 12 is reduced by an etching solution (BOE) to between 10 and 125 μm, and preferably 85 μm, thereby effectively improving the sensitivity of the optical fiber 1 in measuring strains or other physical quantities. .

Referring to FIGS. 2 and 4, the metal layer forming step S2 of the first embodiment of the present invention forms a metal layer 3 on the surface of a substrate 2 (for example, a germanium wafer substrate or a glass substrate). More specifically, the metal layer forming step S2 is divided into two stages. The first stage is to treat the surface of the substrate 2 in advance to remove impurities on the surface of the substrate 2, thereby lifting the substrate 2 and The adhesion between the metal layers 3; wherein, in this embodiment, it is preferred to clean the surface of the substrate 2 with ethanol or acetone. Then, in the second stage, the metal layer 3 is formed on the surface of the substrate 2 by physical vapor deposition (PVD) or chemical vapor deposition (CVD). In this embodiment, the system selects Copper is formed on the upper surface of the substrate 2 in a sputtering manner to form a copper layer as the metal layer 3.

Referring to Figures 2, 5, 6 and 7, the first photoresist forming step S3 of the first embodiment of the present invention is preferably formed by spin coating on the upper surface of the metal layer 3. At least one photoresist layer; for example, in the embodiment, the first photoresist forming step S3 is divided into two stages. In the first stage, please refer to the fifth and sixth figures, which is a photoresist in advance. The material is evenly swirled on the upper surface of the metal layer 3 to form a base layer 4; then the base layer 4 is heated to form a base layer 4, and then the base layer 4 is exposed by ultraviolet light with a mask to make the base layer 4 exposed. A photopolymer chain in the base layer 4. In the second stage, as shown in FIG. 7, the photoresist material which is the same or different from the base layer 4 is evenly spread on the upper surface of the base layer 4 to form a first photoresist layer 5. The photoresist material of the present embodiment is selected as the commercial negative photoresist SU-8 series as an embodiment, but is not limited thereto. The photoresist material may also be selected as XBH HR series, Kodak 747 or JSR. 151N and so on.

Referring to FIGS. 2 and 7, the soft baking step S4 of the first embodiment of the present invention heats the temperature of the photoresist layer to a temperature above its own glass transition temperature (Tg) to volatilize and remain in the photoresist layer. The solvent inside. More specifically, at this time, the present invention first performs the soft baking step S4 on the first photoresist layer 5; wherein the soft baking step S4 is divided into two stages, due to the glass transition temperature of the SU-8 photoresist material. Approximately 55 ° C, therefore, the first stage is preferably selected to heat the first photoresist layer 5 to 65 ° C, the first photoresist layer 5 is transformed into a microfluidic, whereby the first photoresist layer 5 can fill the unevenness of its own surface by its own fluidity, and effectively improve the flatness of the surface of the first photoresist layer 5. Next, the second stage further increases the heating temperature of the first photoresist layer 5 to above a volatilization temperature, which refers to the volatilizable temperature of the solvent remaining in the first photoresist layer 5; Preferably, the heating temperature of the first photoresist layer 5 is increased to 95 ° C so that the solvent remaining in the first photoresist layer 5 can be volatilized into the air, and the first photoresist layer 5 is caused. Hardened forming.

Referring to FIGS. 2 and 8, the exposure step S5 of the first embodiment of the present invention partially exposes the photoresist layer by ultraviolet light, and heats the temperature of the photoresist layer to its own after the exposure is completed. Above the glass transition temperature. More specifically, at this time, the present invention first performs the exposure step S5 on the first photoresist layer 5; wherein the exposure step S5 is divided into three stages, and the first stage preferably selects an adjacent printer. (Proximity Printer) for providing ultraviolet light having a specific wavelength while using a photomask having a geometric pattern to be formed; thereby, when ultraviolet light passes through the photomask and is projected on the first photoresist layer 5, A part of the photopolymers in the first photoresist layer 5 can be linked. The second stage is to heat the temperature of the exposed first photoresist layer 5 to its own glass transition temperature. In this embodiment, the first photoresist layer 5 is preferably heated to 65 ° C for 1 minute. In order to improve the flatness of the surface of the first photoresist layer 5. The third stage is preferably selected to further increase the heating temperature of the first photoresist layer 5 to 95 ° C for 8 minutes, so that the solvent remaining in the first photoresist layer 5 can be volatilized into the air, and The first photoresist layer 5 is hardened and formed; thereby, the first photoresist layer 5 can be provided with sufficient energy to effectively promote the thermal motion of the photoresist molecules, so that the overexposed or underexposed photoresist molecules are rearranged. Average standing wave effect and increase resolution.

Referring to FIGS. 2 and 9, the developing step S6 of the first embodiment of the present invention selectively removes the unexposed photoresist layer by a developing solution (for example, EPD1000 or EPD2000, etc.) to form a light having a geometric structure. Resistance layer. More specifically, at this time, the present invention first performs the developing step S6 on the first photoresist layer 5; since the first photoresist layer 5 is exposed to ultraviolet light, a photopolymer chain is formed, so that the The developer can only remove the unexposed first photoresist layer 5 from the base layer 4; thereby, the first photoresist layer 5 remaining on the surface of the base layer 4 is developed corresponding to the geometric pattern of the mask. The first photoresist layer 5 having a geometric structure is formed, and the geometric structure of the first photoresist layer 5 of the embodiment is a rectangular block arranged at equal intervals. .

The fiber fixing step S7 of the first embodiment of the present invention places the at least one optical fiber 1 that completes the preset step S1 on the metal layer 3 via a fixing component 6 and Above the first photoresist layer 5. In more detail, the fixing component 6 has a positioning seat 61 and two positioning keys 62 for fixing the optical fiber 1; the positioning keys 62 are disposed opposite to the side of the optical fiber 1 It is used to calibrate the relative position between the optical fiber 1 and the first photoresist layer 5 to avoid the deviation of the alignment in the subsequent process.

Referring to FIGS. 12 to 15, the second photoresist forming step S8 of the first embodiment of the present invention again selects to rotate the photoresist material similar to the first photoresist layer 5 by spin coating. The optical fiber 1 and the first photoresist layer 5 fixed to the optical fiber 1 are formed to form a second photoresist layer 7, and the distance R2 between the top surface of the second photoresist layer 7 and the axis of the optical fiber 1 is equal to a distance R1 between the bottom surface of the second photoresist layer 5 and the axis of the optical fiber 1 (as shown in FIG. 13); then, repeating the soft baking step S4, the exposing step S5, and the second photoresist layer 7 The step S6 is developed so that the second photoresist layer 7 is formed on the first photoresist layer 5, and the second photoresist layer 7 of the embodiment is selected to be the same. The rectangular blocks of the first photoresist layer 5 are equally spaced, so that the first and second photoresist layers 5 and 7 are in a zigzag structure with equal pitch at the side view angle (as shown in FIG. 15).

Furthermore, referring to FIGS. 11 and 15, when the exposure step S5 is repeated, the embodiment determines whether the portion of the second photoresist layer 7 to be exposed is the first portion through the positioning button 62. The photoresist layers 5 are aligned with one another, thereby ensuring that the second photoresist layer 7 can be accurately stacked over the first photoresist layer 5.

Referring to Figures 2 and 15, the hard baking step S9 of the first embodiment of the present invention reheats the optical fiber 1 and the first and second photoresist layers 5, 7 which complete the second photoresist forming step S8 to Above the volatilization temperature, in the present embodiment, it is preferred to selectively heat to 150 °C. Thereby, in addition to volatilizing the solvent remaining in the first and second photoresist layers 5, 7 into the air, the first and second photoresist layers 5, 7 can be converted into a microfluidic state, thereby further The first and second photoresist layers 5, 7 can be filled with minute pores in themselves. Further, the hard baking step S9 of the present invention may be optionally performed before or after the separating step S10, and the implementation time point of the hard baking step S9 is not limited by the embodiment.

Referring to Figures 2, 11 and 16, the separation step S10 of the first embodiment of the present invention selectively uses the separation liquid (for example, a ferric chloride solution) to disengage the base layer 4 and the positioning seat 61 from the metal layer 3. . More specifically, the separation step S10 is divided into two stages. The first stage preliminarily immerses the metal layer 3, the base layer 4 and the positioning seat 61 in the separation liquid, thereby enabling the base layer 4 and positioning. The seat 61 is separated from the metal layer 3. In the second stage, it is preferred to use a chemical liquid (for example, sulfuric acid, hydrochloric acid, hydrofluoric acid, photoresist removal solution or developer) for impregnation or physical cutting (laser cutting or cutter cutting, etc.) to The positioning seat 61 is removed and the impurities remaining in the fiber 1 or its surface geometry are removed.

Referring to Figures 2, 17 and 18, the protective layer forming step S11 of the first embodiment of the present invention forms a polymer layer on the outer surface of the optical fiber 1 as a protective layer 8, so that the protective layer 8 can be Filling the gap formed by the sawtooth structure to obtain the finished product of the fiber grating structure. More specifically, the protective layer forming step S11 is preferably divided into three stages. The first stage is to immerse the optical fiber 1 and the first and second photoresist layers 5 and 7 which complete the separating step S10 in a polymer. In the polymer treatment tank, the polymer of the present embodiment is preferably selected as PDMS (polydimethylsiloxane) as an embodiment. In the second stage, the high molecular polymer is selected to be attached to the outer surface of the optical fiber 1 in an air-drying manner, so that the protective layer 8 forms an equidistant arrangement of geometric structures at a side view angle; thereby, the protective layer 8 can be formed on The sawtooth structures of the first and second photoresist layers 5 and 7 effectively enhance the overall structural strength and provide a better protection effect of the fiber grating structure. In the third stage, the size of the protective layer 8 is adjusted by physical cutting, so that the outer peripheral surface of the protective layer 8 and the outer peripheral surfaces of the first and second photoresist layers 5 and 7 are aligned with each other, thereby preventing the protective layer 8 from being avoided. A measure of the accuracy of the measurement of the fiber grating structure.

Referring to Figures 3 and 16, the fiber grating structure of the first embodiment of the present invention is fabricated by the above steps. The fiber grating structure comprises the optical fiber 1, a plurality of photoresist layers and a protective layer 8. The optical fiber 1 includes the cladding layer 12 and a core 13 which is coated on the outer peripheral surface of the core 13; the plurality of photoresist layers are formed by the first and second photoresist layers 5, 7 stacked, and the base layer 4 is disposed on the lower surface of the first photoresist layer 5, such that the first photoresist layer 5 is interposed between the optical fiber 1 and the base layer 4; wherein the first light The cross-sectional shapes of the resistive layer 5 and the second photoresist layer 7 are both in a zigzag structure, and the two are aligned with each other, thereby separating the outer peripheral surface of the optical fiber 1 by a plurality of gaps 14; the protective layer 8 is coated The outer peripheral surface of the cladding layer 12 is filled in the plurality of gaps 14.

In the method for fabricating the fiber grating of the present invention and the structure thereof, since the gap formed by the photoresist layer of the zigzag geometry is provided with the protective layer, the fiber grating structure of the present invention is attached to the fiber by using an adhesive When the surface of the object is measured, the adhesive can be prevented from being filled into the gap, thereby preventing the adhesive from affecting the measurement signal, so that the invention can effectively achieve the effect of improving the measurement accuracy.

The manufacturing method and structure of the fiber grating of the present invention, because the gap formed by the photoresist layer of the zigzag geometry is provided with the protective layer, the bonding strength between the photoresist layer and the optical fiber can be effectively improved, Achieve the effect of increasing structural strength. Moreover, the design of the base layer facilitates the packaging operation process, and simultaneously increases the contact area with the object to be tested, thereby further enhancing the bonding strength between the fiber grating structure and the object to be tested. Effectively avoid damage or breakage of the structure.

Referring to FIGS. 2 and 19, a method for fabricating a fiber grating according to a second embodiment of the present invention and a structure thereof are disclosed. Compared with the first embodiment, the first photoresist forming step S3 of the second embodiment is The step of forming the base layer 4 is omitted, and the first photoresist layer 5 is formed directly on the upper surface of the metal layer 3, and then the soft baking step S4 is performed. Therefore, the structure formed by the manufacturing method of the second embodiment is such that the base layer 4 is omitted as shown in FIG. 19, but only by the optical fiber 1, the first photoresist layer 5, and the second photoresist layer 7. And the protective layer 8 is formed in common. In this way, the second embodiment can also effectively achieve the effect of improving the measurement accuracy.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

[this invention]

1. . . optical fiber

11. . . Fiber coating

12. . . Cladding layer

13. . . Heart

14. . . gap

2. . . Substrate

3. . . Metal layer

4. . . Base layer

5. . . First photoresist layer

6. . . Fixed component

61. . . Positioning seat

62. . . Positioning button

7. . . Second photoresist layer

8. . . The protective layer

R1, R2. . . distance

[customary]

9. . . Fiber grating

91. . . Core

92. . . Cladding layer

93. . . Serrated

Figure 1: Schematic diagram of a conventional fiber grating.

Fig. 2 is a flow chart showing the steps of a method for fabricating a fiber grating according to a first embodiment of the present invention.

Fig. 3 is a partially cutaway perspective view of an optical fiber in a method of fabricating a fiber grating according to a first embodiment of the present invention.

Fig. 4 is a cross-sectional view showing the metal layer forming step of the method for fabricating the fiber grating of the first embodiment of the present invention.

Fig. 5 is a cross-sectional view (1) showing a first photoresist forming step of the method for fabricating the fiber grating of the first embodiment of the present invention.

Fig. 6 is a cross-sectional view showing the first photoresist forming step of the method for fabricating the fiber grating of the first embodiment of the present invention (2).

Fig. 7 is a cross-sectional view showing the first photoresist forming step of the method for fabricating the fiber grating of the first embodiment of the present invention (3).

Fig. 8 is a cross-sectional view showing the exposure step of the method for fabricating the fiber grating of the first embodiment of the present invention.

Fig. 9 is a cross-sectional view showing the developing step of the method for fabricating the fiber grating of the first embodiment of the present invention.

Fig. 10 is a cross-sectional view showing the fiber fixing step of the method for fabricating the fiber grating of the first embodiment of the present invention.

Figure 11 is a perspective view showing the fiber fixing step of the method for fabricating the fiber grating of the first embodiment of the present invention.

Fig. 12 is a cross-sectional view showing the second photoresist forming step of the method for fabricating the fiber grating of the first embodiment of the present invention.

Figure 13 is a rear elevational view showing the second photoresist forming step of the method for fabricating the fiber grating of the first embodiment of the present invention.

Fig. 14 is a cross-sectional view showing the exposure step of the second photoresist layer of the method for fabricating the fiber grating of the first embodiment of the present invention.

Fig. 15 is a cross-sectional view showing the second photoresist layer of the method for fabricating a fiber grating according to the first embodiment of the present invention.

Figure 16 is a cross-sectional view showing the separation step of the method for fabricating the fiber grating of the first embodiment of the present invention.

Fig. 17 is a cross-sectional view showing the step of forming a protective layer of the method for fabricating the fiber grating of the first embodiment of the present invention.

Figure 18 is a cross-sectional view showing the structure of a fiber grating of a first embodiment of the present invention.

Figure 19 is a cross-sectional view showing the structure of a fiber grating of a second embodiment of the present invention.

Claims (23)

A method for fabricating a fiber grating, the method comprising the steps of: (1) pre-removing a fiber layer of at least one fiber, and etching to reduce a thickness of the coating layer of the fiber to 10 to 125 μm; (2) depositing by physical or chemical vapor deposition Forming a metal layer on a surface of the substrate; (3) coating at least one photoresist material on the surface of the metal layer to form at least one photoresist layer; (4) heating the photoresist layer to a temperature above the glass transition temperature to volatilize Residing in the photoresist layer and hardening the photoresist layer; (5) partially exposing the photoresist layer and heating the photoresist layer to a temperature above the glass transition temperature after completion of the exposure; (6) via a The developer removes the unexposed photoresist layer to develop the photoresist layer; (7) fixes the optical fiber that completes step (1) above the photoresist layer that completes step (6); (8) The optical fiber and the photoresist layer are coated with another photoresist layer, and the other photoresist layer repeats the above steps (4) to (6), so that the two photoresist layers together form a sawtooth structure covering the optical fiber. Surface, and then performing step (9); (9) heating the fiber of step (8) and the photoresist located on the outer surface of the fiber , to volatilize the solvent in each of the photoresist layers, and let the photoresist flow fill the gap; (10) using a separating liquid to separate the photoresist layer on the outer surface of the optical fiber from the metal layer; and (11) The polymer polymer covers the outer surface of the fiber and fills the gap formed by the sawtooth structure to form a protective layer. The method for fabricating a fiber grating according to claim 1, wherein the step (11) is to cover the outer surface of the optical fiber into two stages, and the first stage is to complete the step (10). The optical fiber and the photoresist layer are immersed in a polymer processing tank; the second stage is to air-dry the macropolymer to the outer surface of the optical fiber to form the protective layer. The method for fabricating a fiber grating according to claim 2, wherein the step (11) further comprises a third stage, wherein the outer peripheral surface of the protective layer and the outer periphery of the photoresist layer are physically cut. The faces are aligned with each other. The method for fabricating a fiber grating according to claim 1, 2 or 3, wherein the step (2) forms the metal layer on the surface of the substrate by physical or chemical vapor deposition, which is performed by sputtering. A copper cloth is provided on the surface of the substrate to form a copper layer. The method for fabricating a fiber grating according to claim 4, wherein the step (2) is to clean the surface of the substrate with ethanol or acetone before the copper layer is formed by sputtering to remove the substrate. Impurities on the surface. The method for fabricating a fiber grating according to the first, second or third aspect of the patent application, wherein the step (4) heating the photoresist layer to a glass transition temperature is divided into two stages, the first stage is the photoresist The layer is heated to 65 ° C to convert the photoresist layer into a microfluidic shape to fill the unevenness of the surface of the photoresist layer; the second stage further heats the photoresist layer to 95 ° C to volatilize the residual photoresist A solvent in the layer and hardening the photoresist layer. The method for fabricating a fiber grating according to the first, second or third aspect of the patent application, wherein the step (7) fixes the optical fiber that completes the step (1) above the photoresist layer of the step (6). A positioning seat is fixed in advance over the metal layer and the photoresist layer, and two positioning keys are disposed adjacent to the side of the optical fiber, so that the two photoresist layers can be aligned with each other when performing the step (8). The method for fabricating a fiber grating according to claim 7, wherein the step (10) uses the separation liquid to separate the photoresist layer on the outer surface of the fiber from the metal layer into two stages, the first stage. The metal layer, the photoresist layer and the positioning seat are immersed in the separation liquid in advance, and the photoresist layer and the positioning seat are separated from the metal layer; the second stage is to use the chemical liquid immersion or physical cutting method to the optical fiber. Remove the positioning seat. According to the method for fabricating a fiber grating according to claim 8, wherein the metal layer, the photoresist layer and the positioning seat are immersed in the ferric chloride solution in the first stage of the step (10). The method for fabricating a fiber grating according to claim 9, wherein in the second stage of the step (10), the optical fiber is removed from the positioning block by a chemical liquid dipping method, and the optical fiber and the positioning seat are immersed in Sulfuric acid, hydrochloric acid, hydrofluoric acid, photoresist removal solution or developer. The method for fabricating a fiber grating according to claim 9, wherein the second stage of the step (10) uses the physical cutting method to light the light The fiber is removed from the positioning seat by means of laser cutting or cutting. The method for fabricating a fiber grating according to claim 1, 2 or 3, wherein the step (9) is performed before or after the step (10). The method for fabricating a fiber grating according to the first, second or third aspect of the patent application, wherein the step (3) is to apply a photoresist material on the surface of the metal layer to form a base layer, and then to the base. A first photoresist layer is formed on the surface of the layer. The method for fabricating a fiber grating according to claim 13 , wherein before the first photoresist layer is formed on the surface of the base layer, the base layer is preheated to be hardened, and a mask is used to match the ultraviolet light. The base layer is exposed to link the photopolymer of the base layer. A fiber grating structure comprising: an optical fiber having a core and a coating layer, the coating layer covering the outer peripheral surface of the core; and a plurality of photoresist layers covering the outer peripheral surface of the coating layer And a gap is formed between each of the photoresist layers; and a protective layer is coated on the outer peripheral surface of the cladding layer and fills the plurality of gaps; wherein the plurality of photoresist layers are first The photoresist layer and the second photoresist layer are formed together, and further comprise a base layer disposed on the surface of the first photoresist layer, such that the first photoresist layer is interposed between the optical fiber and the base layer . According to the structure of the fiber grating described in claim 15 of the patent application, wherein The cross-sectional shapes of the first photoresist layer and the second photoresist layer are all zigzag structures arranged at equal intervals. The structure of the fiber grating according to claim 15, wherein the protective layer is composed of a high molecular polymer. The structure of the fiber grating according to claim 16, wherein the polymer is PDMS. The structure of the fiber grating according to claim 15, wherein the photoresist material constituting the photoresist layer is composed of a commercial negative photoresist SU-8 series, XBH HR series, Kodak 747 or JSR 151N. A fiber grating structure comprising: an optical fiber having a core and a coating layer, the coating layer covering the outer peripheral surface of the core; and a plurality of photoresist layers covering the outer peripheral surface of the coating layer And a gap is formed between each of the photoresist layers; and a protective layer is coated on the outer peripheral surface of the coating layer and fills the plurality of gaps; wherein the outer peripheral surface of the protective layer and the outer periphery of the photoresist layer The faces are aligned with each other. The structure of the fiber grating according to claim 20, wherein the protective layer is composed of a high molecular polymer. The structure of the fiber grating according to claim 21, wherein the polymer is PDMS. The structure of the fiber grating according to claim 20, wherein the photoresist material constituting the photoresist layer is composed of a commercial negative photoresist SU-8 series, XBH HR series, Kodak 747 or JSR 151N. to make.