TWI394993B - Method for manufacturing a tunable long-period fiber grating - Google Patents

Description

Adjustable variable length period fiber grating manufacturing method

The invention relates to a method for fabricating a variable length-changing fiber grating, in particular to a method for improving the dimensional accuracy of a variable-length variable-length fiber grating.

Referring to FIG. 1 , the manufacturing method of the conventional variable length and long-period fiber grating mainly comprises the following steps: pre-stripping one of the outermost layers of a fiber, and coating one of the fibers (Cladding). Forming an exposed; then, uniformly coating a photoresist layer directly on the coating layer of the optical fiber, and heating the photoresist layer for soft baking; using the ultraviolet light to match a photomask to complete the soft-baking partial photoresist layer Exposing, the exposed partial photoresist layer produces a photopolymer chain, and a core of the fiber is also formed into a plurality of portions having different refractive indices after being irradiated by ultraviolet light; The unexposed photoresist layer is removed by a developing solution, so that the photoresist layer can form a protective layer on the coating layer of the optical fiber; and then, the optical fiber is covered by the protective layer without using an etching solution. The coating is etched to etch a groove structure on the cladding layer of the optical fiber; finally, the protective layer is removed by another etching solution, thereby forming a tunable change with a zigzag geometry on the outer surface of the optical fiber. Long period fiber light Finished.

The method for fabricating the variably variable length period fiber grating is mainly to form the zigzag geometry by using the developer and different etching liquids to directly etch from the surface of the photoresist layer to the fiber core. The developer etching time directly affects the size of the zigzag geometry. Further, since the etching time and the etching depth are related to the developer type, the photoresist material, and other environmental parameters (for example, temperature, etc.), The mastering of the etching time is extremely difficult, resulting in a deviation of the finished product size when forming the zigzag geometry in a conventional manner, especially when forming the concave portion of the zigzag geometry (the recess between the tooth portions) If the etching time is too long, the coating layer of the optical fiber is damaged, or the etching time is too short, resulting in a disadvantage that the dimensional accuracy of the concave portion is insufficient and the dimensional accuracy is low. For the above reasons, the fabrication method of the aforementioned variable length-period fiber grating does have to be improved.

The invention provides a method for fabricating a variable length and long period fiber grating, which is to improve the dimensional precision of the adjustable variable length fiber grating product, which is the object of the invention.

The invention provides a method for fabricating a variable length-period fiber grating, which is to improve the detection sensitivity of the adjustable variable-length fiber grating product, and is another object of the invention.

The present invention provides a method for fabricating a variable length-period fiber grating, which can form teeth and recesses having different sizes on the outer peripheral surface of the optical fiber according to requirements, which is another object of the present invention.

The present invention provides a method for fabricating a variable length-period fiber grating, which is a zigzag geometric structure in which at least one photoresist material is stacked to form an outer peripheral surface of the optical fiber, which is a further object of the present invention.

A method for fabricating a variable length-period fiber grating comprises the steps of: removing a fiber layer of an optical fiber in advance, and etching and reducing a thickness of the coating layer of the fiber to 10 to 125 μm; or physically or chemically vapor deposition Forming a metal layer on the surface of the material; coating at least one photoresist material on the surface of the metal layer to form at least one photoresist layer; heating the photoresist layer to a temperature above the glass transition temperature to volatilize the solvent remaining in the photoresist layer And hardening the photoresist layer; exposing the photoresist layer by using ultraviolet light and a mask, and heating the photoresist layer to a temperature above the glass transition temperature after the exposure is completed; removing the unexposed layer by a developer solution a partial photoresist layer to develop the photoresist layer into a lower geometry; the optical fiber is fixed to the lower geometry; at least one layer of another photoresist layer is overcoated over the optical fiber and the lower geometry, and Exposing and developing the other photoresist layer to form an upper geometry over the lower geometry, thereby causing the upper geometry and the lower geometry to be on the outer surface of the fiber a zigzag geometry; heating the fiber and the geometry on the outer surface of the fiber to volatilize the solvent in each of the photoresist layers and allowing the photoresist to fill the void; and finally, using a separating liquid to make the outer surface of the fiber The photoresist layer is separated from the metal layer to obtain a finished variable length period fiber grating product.

The above and other objects, features and advantages of the present invention will become more <RTIgt; The manufacturing method of the adjustable variable length fiber grating of the first embodiment of the present invention comprises the following steps: a fiber forming step S1, a metal layer forming step S2, a lower photoresist forming step S3, a soft baking step S4, and an exposure. Step S5, a developing step S6, a fiber fixing step S7, an upper photoresist forming step S8, a hard baking step S9, and a dividing step S10.

Referring to FIGS. 2 and 3, the fiber forming step S1 of the present invention removes at least one of the fibers 1 from the fiber layer 11 and then etches one of the fibers 1 by an etching solution (BOE). The thickness of the cladding layer 12 is reduced to 10 to 125 μm, wherein the thickness of the cladding layer 12 is preferably 85 μm, thereby improving the sensitivity of the optical fiber 1 when relatively measuring an amount of strain or other physical quantity.

Referring to Figures 2 and 4, the metal layer forming step S2 of the present invention forms a metal layer 3 on the surface of a substrate 2. More specifically, the substrate 2 is preferably selected from the group consisting of a germanium wafer substrate or a glass substrate. In this embodiment, a germanium wafer is selected as the substrate 2, and the surface of the substrate 2 is surface-treated in advance. For example, cleaning the surface of the substrate 2 with ethanol or acetone to remove impurities on the surface of the substrate 2, and improving adhesion to the metal layer 3; then, using physical vapor deposition (PVD) or chemical vapor deposition The metal layer 3 is formed on the surface of the substrate 2 by means of (CVD) or the like. In this embodiment, copper is selectively formed on the surface of the substrate 2 by sputtering to form a copper layer as the metal layer 3.

In the photoresist forming step S3 of the present invention, a photoresist material is uniformly spun on the surface of the metal layer 3 by spin coating to form a lower photoresist layer 4, and the lower photoresist layer 4 has A predetermined thickness T1 (as shown in Fig. 10). In addition, the photoresist material of the embodiment is selected as a commercial negative photoresist SU-8 series, but the photoresist material is not limited to the SU-8 series, and may also be selected as other photoresist materials, for example: XBH HR Series, Kodak747 or JSR 151N, etc.

The soft baking step S4 of the present invention heats the temperature of the photoresist layer on the substrate 2 to a temperature above its own glass transition temperature (Tg) to volatilize the solvent remaining in the lower photoresist layer 4. In more detail, in this embodiment, the soft baking step S4 is performed on the lower photoresist layer 4, wherein the soft baking step S4 of the present invention is divided into two stages, and the first stage is pre-transmitted by the heating element. The photoresist layer 4 under the surface of the substrate 2 is heated above the glass transition temperature of the SU-8 photoresist material. Since the glass transition temperature of the SU-8 is about 55 ° C, the present embodiment is in the soft baking step S4. In one stage, the temperature of the lower photoresist layer 4 is heated to 65 ° C in advance, so that the lower photoresist layer 4 is transformed into a microfluidic state, so that the lower photoresist layer 4 can fill the lower photoresist by its own fluidity. The unevenness of the surface of the layer 4 enhances the surface flatness of the lower photoresist layer 4. Furthermore, the second stage further increases the temperature of the lower photoresist layer 4 to a temperature above a volatilization temperature, which is the volatilization temperature of the solvent remaining in the photoresist layer, and is selected in the second stage of the embodiment. The temperature of the lower photoresist layer 4 is heated to 95 ° C so that the solvent remaining in the lower photoresist layer 4 is volatilized into the air, and the lower photoresist layer 4 is hardened.

Referring to FIGS. 2 and 5, the exposure step S5 of the present invention exposes the photoresist layer with ultraviolet light and reheats the temperature of the photoresist layer to its own glass transition temperature after the exposure is completed. More specifically, in this embodiment, the exposure step S5 is performed on the lower photoresist layer 4, wherein the embodiment uses an adjacent printer to provide ultraviolet light having a specific wavelength, and cooperates with A reticle having a geometric pattern to be formed, through which the ultraviolet light is projected, and then projected onto the lower photoresist layer 4 to cause a portion of the photopolymers in the lower photoresist layer 4 to be linked. Next, the temperature of the lower photoresist layer 4 that has been exposed to exposure is again heated to its own glass transition temperature, and the post-exposure baking operation is performed.

The post-exposure baking operation is divided into two stages. In the first stage, the photoresist layer 4 is heated to 65 ° C in advance and maintained for 1 minute to enhance the surface flatness of the lower photoresist layer 4. Next, the second stage further heats the temperature of the lower photoresist layer 4 to 95 ° C for 8 minutes, so that the solvent remaining in the lower photoresist layer 4 is volatilized into the air to make the lower photoresist layer 4 The hardening is formed, and at the same time, the lower photoresist layer 4 is provided with sufficient energy to cause the photoresist molecules to generate thermal motion so that the overexposed or underexposed photoresist molecules are rearranged, thereby averaging the standing wave effect and increasing the resolution.

Referring to Figures 2 and 6, the developing step S6 of the present invention removes the unexposed photoresist layer via a developer such that the photoresist layer forms the photoresist layer having a geometric configuration. More specifically, in this embodiment, the developing step S6 is performed on the lower photoresist layer 4 in which the exposure step S5 has been completed, wherein the developer can be selected from conventional developing solutions (for example, EPD1000 or EPD2000, etc.). Since the portion of the lower photoresist layer 4 that is irradiated with ultraviolet light forms a photopolymer chain, the developer can only form the portion of the lower photoresist layer 4 that does not form a photopolymer chain (ie, is not exposed). The lower photoresist layer 4) is removed from the metal layer 3, whereby the lower photoresist layer 4 remaining on the surface of the metal layer 3 is developed to correspond to the geometric pattern of the photomask to form the lower photoresist layer 4 having a geometric configuration. (hereinafter referred to as the lower geometry), wherein the geometry below this embodiment is a rectangular block arranged at equal intervals.

Referring to Figures 2, 7 and 8, the fiber fixing step S7 of the present invention places at least one optical fiber 1 completing the fiber forming step S1 on the metal layer 3 and the lower geometric structure via a fixing assembly 5 . The fixing component 5 has a positioning base 51 and two positioning coordinates 52. The two ends of the optical fiber 1 are fixed on the positioning base 51, and the positioning coordinates 52 are disposed opposite to the side of the optical fiber 1. The positioning coordinates 52 are used to calibrate the relative position between the optical fiber 1 and the lower geometry to avoid deviations in the alignment of subsequent processes.

Referring to FIGS. 7-11, the photoresist forming step S8 of the present invention is again applied to the optical fiber 1 and the photoresist layer fixed to the optical fiber 1 to selectively apply the same photoresist as the lower photoresist layer 4. Material to form at least one upper photoresist layer 6 and repeating the foregoing steps S4 to S6 for the upper photoresist layer 6 so that the upper photoresist layer 6 is also formed with a geometrically structured upper photoresist layer 6 stacked on the lower geometry Constructive. More specifically, in this embodiment, the upper photoresist layer 6 is coated on the optical fiber 1 and the lower photoresist layer 4 by spin coating, and the upper photoresist layer 6 has a predetermined thickness T2. The thickness T2 of the upper photoresist layer 6 is greater than the thickness T1 of the lower photoresist layer 4, but the distance R1 between the top surface of the upper photoresist layer 6 and the axis of the optical fiber 1 is equal to the bottom surface of the lower photoresist layer 4 to the optical fiber. 1 distance between the axes R2. Then, the soft-baking step S4, the exposing step S5, and the developing step S6 are repeated on the upper photoresist layer 6, and the upper photoresist layer 6 having a geometric structure (hereinafter referred to as the upper geometric structure) is aligned and developed. Geometrically constructed. Since the upper geometrical structure is the same rectangular block formed by the lower geometrical structure, and the upper geometrical configuration has the same planar shape as the lower geometrical configuration, the embodiment is formed on the outer surface of the optical fiber 1. The shape of the photoresist layer is an uneven pitch in the side view angle (as shown in Fig. 12). Wherein, when the exposure step S5 is repeated, the positioning coordinates 52 are used to confirm whether the relative position between the portion to be exposed of the upper photoresist layer 6 and the lower geometry is aligned, so as to ensure that the upper geometric structure can be accurately stacked. Above the lower geometry.

The hard baking step S9 of the present invention reheats the optical fiber 1 and the upper and lower photoresist layers 6 and 4 which complete the upper photoresist forming step S8 to above the volatilization temperature, and the hard baking step S9 of the embodiment selects the The optical fiber 1 and the upper and lower photoresist layers 6, 4 are heated to 150 ° C, so that the solvent remaining in the upper and lower photoresist layers 6 and 4 is volatilized and removed, and the upper and lower photoresist layers 6 and 4 can be further removed. It is transformed into a microfluidic shape to further fill the minute pores in the upper and lower photoresist layers 6, 4. In addition, the hard baking step S9 may be optionally performed before or after the stripping step S10, and the implementation time point of the hard baking step S9 is not limited by the embodiment.

Referring to FIGS. 8 and 12, the dividing step S10 of the present invention utilizes a separating liquid to separate the lower photoresist layer 4 and the positioning block 51 from the metal layer 3 to obtain a finished product of the adjustable variable length period fiber grating. . More specifically, the dividing step S10 of the present invention is divided into two stages, wherein the first stage is to immerse the metal layer 3, the lower photoresist layer 4 and the positioning block 51 in the separating liquid in advance, wherein the separating liquid is preferably It is selected from a ferric chloride solution, whereby the lower photoresist layer 4 and the positioning block 51 are separated from the metal layer 3. Furthermore, since the optical fiber 1 is positioned by the positioning block 51 in the fiber fixing step S7, the second stage is required to remove the optical fiber 1 from the positioning seat 51 by chemical liquid immersion or physical cutting. The impurities remaining in the optical fiber 1 or its surface geometry are removed to obtain a finished product of the tunable variable length period fiber grating. The chemical liquid may be selected from the group consisting of sulfuric acid, hydrochloric acid, hydrofluoric acid, photoresist removal liquid or developer, and the physical cutting method may be selected from the group consisting of laser cutting or cutting.

The main technical feature of the method for fabricating the variable length-period fiber grating of the present invention is that the present invention directly pre-forms the lower geometry having a predetermined thickness on the substrate 2, and then aligns the optical fiber 1 and the upper geometric structure. Stacked above the lower geometry, a photoresist layer having a sawtooth geometry is formed on the outer surface of the fiber 1. Since the upper and lower photoresist layers 6 and 4 of the present invention can precisely control the thickness of the upper and lower photoresist layers 6 and 4, respectively, and directly remove the unexposed photoresist layer during development, The zigzag geometry can be controlled to have the same distance from the top end of each tooth to the axis of the optical fiber 1, and the depth of each recess (the recess between the teeth) of the zigzag geometry is equal to the thickness of the tooth ( That is, the thickness of the photoresist layer).

Therefore, the user can control the thickness of the lower and upper photoresist layers 4 and 6 in the lower photoresist forming step S3 and the upper photoresist forming step S8 according to the size of the zigzag geometry required. The zigzag geometry can be further controlled to maintain the desired dimensions, helping to improve the measurement accuracy of subsequent metrology applications.

In addition, since the optical fiber 1 of the present invention reduces the thickness of the cladding layer 12 by etching in advance, thereby improving the measurement sensitivity of the optical fiber 1 when relatively measuring an amount of strain or other physical quantity.

Referring to Figures 14 to 25, there is disclosed a method of fabricating a variable length-length fiber grating of a second embodiment of the present invention. Compared with the first embodiment, the upper and lower photoresist layers 6 and 4 of the second embodiment are of a plurality of layers, and the materials of the upper and lower photoresist layers 6 and 4 can be selected as different photoresist materials. . More specifically, after the foregoing steps S1 and S2 are completed in this embodiment, a first lower photoresist layer 4' is formed on the surface of the metal layer 3 in advance according to the foregoing steps S3 to S6, and the first lower photoresist layer is formed. The layer 4' performs a process of soft baking and exposure development, so that the first lower photoresist layer 4' is developed on the metal layer 3 into a first lower photoresist layer 4' having a geometric configuration (hereinafter referred to as a first lower geometry) , as shown in Figure 14). Then, referring to the steps 15 and 16, repeating the foregoing steps S3 to S6, a second lower photoresist layer 4'' is stacked and coated on the first lower photoresist layer 4', and is soft baked and After the process of exposure development, a second lower photoresist layer 4'' having the same geometrical configuration (hereinafter referred to as a second lower geometry) is stacked and formed on the first lower geometry, the first lower geometry and the second lower The geometrical configuration has the same top view shape to form a plurality of photoresist layers stacked on each other to form a lower geometry.

In addition, after the first lower photoresist layer 4' and the second lower photoresist layer 4'' are completed, the optical fiber fixing step S7 is performed to fix the optical fiber 1 after the first lower photoresist layer 4' and the second lower photoresist layer 4'' are completed. On the lower geometry, and then performing the upper photoresist forming step S8, a first upper photoresist layer 6' is stacked and coated on the optical fiber 1 and the lower geometry, and the first upper photoresist layer 6' is Performing a process of soft baking and exposure development, so that the first upper photoresist layer 6' is aligned in the lower geometry to form a first upper photoresist layer 6' having a geometric configuration (hereinafter referred to as the first upper geometric structure). Further, referring to the 22th to 24th drawings, the upper photoresist forming step S8 is repeated to apply a second upper photoresist layer 6'' on the first upper photoresist layer 6', and is being carried out. After the soft baking and exposure development process, a second upper photoresist layer 6 ′′ (hereinafter referred to as a second upper geometric structure) having the same geometric configuration is stacked on the first upper geometric structure to form a plurality of photoresist layers. Stacked on top of each other to form an upper geometrical structure, wherein the upper geometrical structure is further associated with the lower geometrical structural system An outer peripheral surface of fiber constituting the geometry of the photoresist layer is serrated.

Finally, referring to FIG. 25, the first lower photoresist layer 4', the second lower photoresist layer 4'', the first upper photoresist layer 6', and the second surface are completed on the outer peripheral surface of the optical fiber 1. After the stacking process of the photoresist layer 6'', the present embodiment performs hard baking and cutting of the optical fiber 1 and the photoresist layer according to steps S9 to S10, thereby obtaining the finished product of the adjustable variable length period fiber grating.

Since the present invention pre-forms a plurality of photoresist layers directly on the substrate 2, and exposes them to a plurality of lower layer geometries having a predetermined thickness, and then stacks the optical fibers 1 over the lower geometry, again The optical fiber 1 and the lower geometrical structure are stacked to form the geometrical structure on the plurality of layers, so that a photoresist layer having a sawtooth geometry is formed on the outer surface of the optical fiber 1, whereby the present invention can form the photoresist layer in a stack. According to the requirement, each of the photoresist layers is selected from the same or different photoresist materials, so that the adjustable variable length fiber grating produced by the present invention can have a zigzag geometric structure composed of several different photoresist materials on the outer surface thereof. In order to respond to various usage needs.

In addition, although the distance R3 between the top surface of the second upper photoresist layer 6'' and the axis of the optical fiber 1 in this embodiment is equal to the bottom surface of the first lower photoresist layer 4' to the axis of the optical fiber 1 R4, but the first lower photoresist layer 4', the second lower photoresist layer 4", the first upper photoresist layer 6' and the second upper photoresist layer 6" may also be in respective forming steps The thicknesses are selected to have the same or different thicknesses, and the distance R3 is further adjusted to be different from the distance R4 such that the zigzag geometry has teeth of different sizes to accommodate various usage requirements.

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. . . Core

2. . . Substrate

3. . . Metal layer

4. . . Lower photoresist layer

4’. . . First lower photoresist layer

4’’. . . Second lower photoresist layer

5. . . Fixed component

51. . . Positioning seat

52. . . Positioning coordinates

6. . . Upper photoresist layer

6’. . . First upper photoresist layer

6’’. . . Second upper photoresist layer

Fig. 1: Schematic diagram of a method for fabricating a conventional variable length and long period fiber grating.

Fig. 2 is a flow chart showing the first embodiment of the method for fabricating the variable length-period fiber grating of the present invention.

3 is a partial cross-sectional view and a perspective view of a fiber according to a first embodiment of the present invention.

Fig. 4 is a cross-sectional view showing the first embodiment of the present invention for coating a metal layer and a photoresist layer on a substrate.

Fig. 5 is a cross-sectional view showing the exposure of the lower photoresist layer in the first embodiment.

Figure 6 is a cross-sectional view showing the development of the photoresist layer of the first embodiment.

FIG. 7 is a perspective view showing the first embodiment of the optical fiber fixed to the lower geometric structure.

Figure 8 is a cross-sectional view showing the first embodiment of the optical fiber fixed to the lower geometric structure.

Fig. 9 is a cross-sectional view showing the first embodiment of the present invention in which a photoresist layer is coated on an optical fiber and a lower geometric structure.

Fig. 10 is a view showing the first embodiment of the present invention in which a photoresist layer is coated on an optical fiber and a lower geometry.

11 is a cross-sectional view showing the exposure of the upper photoresist layer in the first embodiment.

Fig. 12 is a cross-sectional view showing the development of the photoresist layer of the first embodiment.

Figure 13 is a cross-sectional view showing the variably variable length period fiber grating of the first embodiment of the present invention.

Figure 14 is a cross-sectional view showing the second embodiment of the first lower photoresist layer.

Fig. 15 is a cross-sectional view showing the second embodiment of the second lower photoresist layer coated with the second variable embodiment of the present invention.

Figure 16 is a cross-sectional view showing the second lower photoresist layer exposed by the second embodiment of the present invention.

Figure 17: Method for fabricating the variable length-period fiber grating of the present invention. The second embodiment of the second lower photoresist layer is developed and stacked on the first photoresist layer.

Figure 18: Method for fabricating the variable length-period fiber grating of the present invention. The second embodiment is a perspective view of the optical fiber fixed to the lower geometric structure.

Fig. 19 is a cross-sectional view showing the first upper photoresist layer coated on the optical fiber and the lower geometric structure.

Figure 20 is a cross-sectional view showing the exposure of the first upper photoresist layer in the second embodiment.

Fig. 21 is a cross-sectional view showing the development of the photoresist layer of the second embodiment of the present invention.

Fig. 22 is a cross-sectional view showing the second embodiment of the second upper photoresist layer coated with the second variable embodiment of the present invention.

Figure 23 is a cross-sectional view showing the exposure of the second upper photoresist layer in the second embodiment.

Fig. 24 is a cross-sectional view showing the second development of the second upper photoresist layer in the second embodiment.

Figure 25 is a cross-sectional view showing the second embodiment of the variable length-period fiber grating finished product of the second embodiment.

Claims (16)

A method for fabricating a variable length-period fiber grating comprises the steps of: (1) pre-removing at least one fiber layer of the fiber, and etching to reduce the thickness of the fiber layer to 10 to 125 μm; (2) physically or Forming a metal layer on the surface of a substrate by chemical vapor deposition; (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 glass conversion Above the temperature, to volatilize the solvent remaining in the photoresist layer, and to harden the photoresist layer; (5) exposing 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 partial photoresist layer via a developer to develop the photoresist layer into a lower geometry; (7) fixing the fiber completing step (1) above the lower geometry; Applying at least one layer of another photoresist layer over the fiber and the lower geometry again, and the other photoresist layer repeats steps (4) through (6) above to form an upper layer over the lower geometry a geometric configuration, and the upper geometric configuration is covered with the lower geometric configuration The outer surface of the optical fiber; (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 flow fill the gap; and (10) The photoresist layer on the outer surface of the optical fiber is separated from the metal layer by a separating liquid to obtain a variably variable length period fiber grating finished product. According to the manufacturing method of the adjustable variable length fiber grating according to the first aspect of the patent application, in the step (2), a copper cloth is disposed on the surface of the substrate by sputtering to form a copper layer. The method for fabricating a variable length-length fiber grating according to the second aspect of the patent application, wherein the step (2) is to clean the surface of the substrate with ethanol or acetone before removing the copper layer by sputtering. Impurities on the surface of the substrate. The method for fabricating a variable length-period fiber grating according to the first aspect of the patent application, wherein the lower geometric structure is formed on the metal layer according to the steps (3) to (6), and the lower geometric structure is This step (3) to (6) is repeated again to facilitate stacking and forming another lower geometry having the same top view shape on the lower geometry. The method for fabricating a variable length-length fiber grating according to claim 1 or 4, wherein the step (8) is formed by stacking the upper geometric structure over the optical fiber and the lower geometric structure, and is attached to the upper geometric structure. A photoresist layer is again applied over and the steps (4) through (6) are repeated to facilitate stacking the upper geometry to form another upper geometry having the same top view shape. According to the manufacturing method of the adjustable variable length fiber grating according to Item 5 of the patent application scope, each of the upper geometric structure and the lower geometric structure is composed of different photoresist materials. According to the manufacturing method of the adjustable variable length period fiber grating according to the fifth aspect of the patent application, wherein the upper geometric structure and the lower geometric structure are composed of the same photoresist material. The method for manufacturing the variable length-length fiber grating according to claim 6 of the patent application scope, wherein the upper geometric structure and the lower geometric structure have different thicknesses. The method for fabricating a variable length-length fiber grating according to claim 7 of the patent application scope, wherein the upper geometric structure and the lower geometric structure have different thicknesses. According to the manufacturing method of the adjustable variable length fiber grating according to the first aspect of the patent application, wherein the photoresist material is a commercial negative photoresist SU-8 series, the step (4) is divided into two stages, first The step of heating the photoresist layer to 65 ° C, the photoresist layer is transformed into a microfluidic shape to fill the unevenness of the surface of the photoresist layer; the second stage reheats the photoresist layer to 95 ° C to volatilize The solvent remaining in the photoresist layer hardens the photoresist layer. According to the manufacturing method of the adjustable variable length fiber grating according to the first aspect of the patent application, wherein the fiber (7) is fixed to the metal layer and the lower geometric structure by a fixing seat, and is close to the The side edge of the fiber is provided with a positioning coordinate so that the upper geometry can be positioned opposite the lower geometry when performing step (8). According to the manufacturing method of the variable length-period fiber grating according to Item 11 of the patent application, wherein the step (10) is divided into two stages, the first stage is to immerse the metal layer, the photoresist layer and the positioning seat in the first stage. In the separating liquid, the photoresist layer and the positioning seat are separated from the metal layer; in the second stage, the optical fiber is removed from the positioning seat by chemical liquid impregnation or physical cutting to obtain the finished variable length period fiber grating finished product. . The method for manufacturing the variable length long-period fiber grating according to claim 1 or 12, wherein the separating liquid is a ferric chloride solution. The method for manufacturing the variable length-changing fiber grating according to claim 12, wherein the chemical liquid is selected from the group consisting of sulfuric acid, hydrochloric acid, hydrofluoric acid, photoresist removal liquid or developer. The method for manufacturing the variable length-changing fiber grating according to claim 12, wherein the physical cutting method is laser cutting or cutting. The method for fabricating a variable length-length fiber grating according to claim 1 of the patent application, wherein the step (9) is performed before or after the step (9).