Optical fiber ribbon and method for manufacturing optical fiber ribbon

Abstract

Provided is an optical fiber ribbon having a grating formed by a simpler method. The optical fiber ribbon comprises: a plurality of single-core coated optical fibers that are arranged in parallel; and a tape layer that covers the single-core coated optical fibers and that partially connects the adjacent single-core coated optical fibers. The single-core coated optical fibers have, in the longitudinal direction of the single-core coated optical fibers, a grating portion based on a plurality of strain sections formed at fixed intervals in the tape layer.

Description

Optical fiber ribbon and method for manufacturing the same

[0001] The present invention relates to an optical fiber ribbon and a method for manufacturing the optical fiber ribbon.

[0002] In recent years, data traffic has increased dramatically due to the spread of the Internet of Things (IoT), the full-scale commercial launch of 5G services, and autonomous driving of automobiles, and this has led to a growing demand for the development and construction of high-speed, high-capacity optical fiber communication networks to support this. Optical filters are widely used in WDM (Wavelength Division Multiplexing) transmission, which enables the transmission of larger amounts of information in optical communications. Technology using optical fiber gratings as optical filters has also been proposed (see Patent Document 1).

[0003] Patent Document 1 discloses a method for manufacturing an optical fiber having a grating. The method for manufacturing an optical fiber described in Patent Document 1 involves applying resin to the coating of the optical fiber at predetermined intervals and then hardening the resin. Stress is then applied to the optical fiber at the intervals where the resin was applied, and the bending relative to the core is fixed, thereby manufacturing an optical fiber having a grating.

[0004] JP 2018-36340 A

[0005] However, in the optical fiber manufacturing method described in Patent Document 1, a relatively large amount of resin is applied to the coating, resulting in the formation of multiple relatively large protrusions on the surface of the optical fiber. Therefore, the optical fiber described in Patent Document 1 is not suitable for high-speed, high-capacity optical fiber communication networks because it is not possible to accommodate many optical fibers in existing ducts. Furthermore, the multiple protrusions caused by the resin on the coating may exert lateral pressure on other optical fibers, potentially affecting them. Furthermore, the manufacturing process is complex, resulting in high manufacturing costs.

[0006] An object of the present invention is to provide an optical fiber ribbon having a grating formed by a simpler method and a method for manufacturing the same.

[0007] In order to solve the above problems, according to one aspect of the present invention, there is provided an optical fiber ribbon comprising a plurality of mono-coated optical fibers arranged in parallel and a tape layer covering the mono-coated optical fibers and partially connecting adjacent mono-coated optical fibers, wherein the mono-coated optical fibers have grating sections based on a plurality of strain sections formed at regular intervals in the tape layer in the longitudinal direction of the mono-coated optical fibers.

[0008] According to another aspect of the present invention, there is provided a method for manufacturing an optical fiber ribbon, comprising the steps of: preparing a ribbon-shaped optical fiber having a plurality of mono-coated optical fibers arranged in parallel and a tape layer covering the mono-coated optical fibers and partially connecting adjacent mono-coated optical fibers; and forming a grating by dropping a solution containing a volatile liquid at regular intervals in the longitudinal direction of the mono-coated optical fiber or by cooling the mono-coated optical fiber at regular intervals to form a plurality of strained portions in the tape layer with a regular center-to-center distance.

[0009] According to the present invention, it is possible to provide an optical fiber ribbon having a grating portion formed by a simpler method and a method for manufacturing the same.

[0010] 1A and 1B are diagrams showing an optical fiber ribbon according to an embodiment of the present invention. FIG. 2 is a flowchart for explaining a manufacturing method of an optical fiber ribbon. FIG. 3 is a perspective view showing an example of a manufacturing apparatus for an optical fiber ribbon. FIG. 4 is a graph showing the relationship between the center-to-center distance of strained portions and optical transmission loss. FIG. 5 is a graph showing the relationship between the center-to-center distance of strained portions, the wavelength of light incident on the optical fiber ribbon, and optical transmission loss.

[0011] An optical fiber ribbon and a method for manufacturing the same according to an embodiment of the present invention will be described below. In this specification, the lower and upper limits of a numerical range indicated by "to" are included in the numerical range.

[0012] (Configuration of the Optical Fiber Ribbon) Fig. 1A is a schematic plan view of an optical fiber ribbon 10. Fig. 1B is a cross-sectional view taken along line AA in Fig. 1A.

[0013] As shown in Figures 1A and 1B, the optical fiber ribbon 10 of this embodiment has a plurality of mono-coated optical fibers (hereinafter also simply referred to as "optical fibers") 20 and a tape layer 40 including a plurality of connecting portions 30.

[0014] The optical fibers 20 are arranged in parallel. The number of optical fibers 20 is not particularly limited as long as it is plural. The number of optical fibers 20 included in one optical fiber ribbon 10 is appropriately selected depending on the application of the optical fiber ribbon 10. The number of optical fibers 20 included in one optical fiber ribbon 10 is, for example, 2 to 12. In this embodiment, six optical fibers 20 are arranged in parallel in one optical fiber ribbon 10.

[0015] 1B , the optical fiber 20 includes an optical fiber strand 21, a primary coating layer 22, and a secondary coating layer 23. The optical fiber strand 21, the primary coating layer 22, and the secondary coating layer 23 may be similar to the optical fiber strand, the first coating layer, and the second coating layer of a known optical fiber. A colored layer may be further formed on the secondary coating layer 23 of the optical fiber 20. The colors of the colored layers are preferably different from one another within the optical fiber ribbon 10. This allows multiple optical fibers 20 to be distinguished within one optical fiber ribbon 10. The optical fiber 20 also includes a grating section 50.

[0016] The tape layer 40 covers the optical fibers 20 and intermittently connects adjacent optical fibers 20. In this embodiment, a region where the tape layer 40 is disposed between adjacent optical fibers 20 is referred to as a connection portion 30, and a region where the tape layer 40 is not disposed between adjacent optical fibers 20 is referred to as a separation portion 41. In the optical fiber ribbon 10 of this embodiment, the connection portions 30 and the separation portions 41 are alternately disposed between adjacent optical fibers 20 in the longitudinal direction of the optical fiber ribbon 10. In the short direction (width direction) of the optical fiber ribbon 10, it is preferable that the separation portions 41 are disposed so that adjacent separation portions 41 partially overlap each other.

[0017] The width W of the connecting portion 30 when the optical fiber ribbon 10 is viewed in a plan view, i.e., the distance between adjacent optical fibers 20, is not particularly limited and is, for example, in the range of more than 0 mm and not more than 0.04 mm. The length L of the connecting portion 30 when the optical fiber ribbon 10 is viewed in a plan view is also not particularly limited and is, for example, in the range of 10 mm to 47 mm. The thickness T of the connecting portion 30 is also not particularly limited and is, for example, in the range of 0.2 mm to 0.3 mm. When the width W, length L, and thickness T of the connecting portion 30 are within the above ranges, the strength of the connecting portion 30 is increased, and the connecting portion 30 is less likely to tear even when the optical fiber ribbon 10 is wound along the longitudinal direction or twisted as needed. Meanwhile, the length B of the separating portion 41 when the optical fiber ribbon 10 is viewed in a plan view is not particularly limited and is, for example, in the range of 50 mm to 103 mm. If the length L of the separation portion 41 is within this range, the optical fiber ribbon 10 can be easily wound or twisted along the length direction when the optical fiber ribbon 10 is housed in a cable.

[0018] The grating section 50 is formed within the optical fiber 20. The position of the grating section 50 in the longitudinal direction of the optical fiber 20 is set appropriately depending on the intended use of the optical fiber 20. The grating section 50 may be formed at one location in one optical fiber 20, or at multiple locations. The grating section 50 is formed based on multiple strain sections 51 formed at regular intervals within the optical fiber 20 in the longitudinal direction of the optical fiber 20. Specifically, the grating section 50 is formed by stress being applied to the core of the optical fiber 20 by the strain sections 51 formed at regular intervals in part of the outermost layer of the optical fiber 20 (the tape layer 40 in this embodiment). Preferably, the multiple strain sections 51 are formed in positions directly above the optical fiber 20 within each portion of the tape layer 40.

[0019] The "distorted portion 51" refers to a portion that is distorted to the extent that it can impart stress to the core of the optical fiber 20, and in this case refers to a portion where the hardness differs between the distorted portion 51 and the adjacent region (non-distorted portion).

[0020] The shape of the strained portion 51 in plan view is not particularly limited. The shape of the strained portion 51 in plan view may be circular, polygonal, or another shape. In this embodiment, the multiple strained portions 51 are substantially circular and have the same size. The size of the strained portion 51 is such that two adjacent strained portions 51 do not overlap in the longitudinal direction of the optical fiber 20. For example, the size of the strained portion 51 is approximately 0.25 mm.

[0021] The surface of the strained portion 51 may be colored. In the present embodiment, the plurality of strained portions 51 are arranged on only one surface of the optical fiber ribbon 10, but they may be arranged on both surfaces of the optical fiber ribbon 10. The method of forming the grating portion 50 will be described in detail later.

[0022] The center-to-center distance of the strained portions 51 in the longitudinal direction of the optical fiber 20 is not particularly limited as long as it can exhibit the grating function. The center-to-center distance of two adjacent strained portions 51 is set appropriately depending on the intended use of the optical fiber 20 having the grating portion 50. The center-to-center distance of the strained portions 51 does not necessarily have to be constant. For example, if the center-to-center distance of each strained portion 51 is within a range of ±0.05 mm of the average value of the center-to-center distance of the strained portions 51, it can be said that the multiple strained portions 51 are formed at regular intervals. Note that if the center of the strained portion 51 cannot be determined based on the shape of the strained portion 51 in a planar view, the center of gravity of the strained portion 51 when viewed in a planar view is used.

[0023] For example, the plurality of distortion sections 51 may be arranged so that the wavelength of light entering the optical fiber 20 does not overlap with the wavelength of light attenuated by the grating section 50. In such a case, the wavelength of light used can be matched with the optical communication band while intentionally excluding the attenuated wavelength of light from the optical communication band (see Examples).

[0024] Conversely, the plurality of strain portions 51 may be arranged so that the wavelength of light used to enter the optical fiber 20 overlaps with the wavelength of light attenuated by the grating portion 50. In such a case, the wavelength of light used and the wavelength of light attenuated can be intentionally overlapped, allowing the optical fiber 20 having the strain portions 51 formed therein to exhibit an optical filtering function (see Examples). For example, when light of a plurality of wavelengths is input to the optical fiber 20 as in WDM transmission and the optical fiber 20 is used as a wavelength filter on the output side, the plurality of strain portions 51 are formed so that the wavelength of unnecessary light (the wavelength of light to be attenuated) among the wavelengths of light used to enter the optical fiber 20 coincides with the wavelength of light to be attenuated by the grating portion 50. This makes it possible to block the wavelength of light to be attenuated, thereby filtering light passing through the grating portion 50.

[0025] The plurality of strained portions 51 may be formed on all of the optical fibers 20 constituting the optical fiber ribbon 10 (see FIG. 1), on only one optical fiber 20, or on any number of optical fibers 20 (2 to 5 in the example of FIG. 1). The number of strained portions 51 in each optical fiber 20 may also be the same for all the optical fibers 20 (see FIG. 1), or may differ for each optical fiber 20.

[0026] (Method of manufacturing optical fiber ribbon) Next, a method of manufacturing the optical fiber ribbon 10 will be described. Fig. 2 is a flowchart for explaining the method of manufacturing the optical fiber ribbon 10. Fig. 3 is a perspective view showing an example of a manufacturing apparatus 100 for manufacturing the optical fiber ribbon 10. Note that, here, a method of forming a grating section 50 based on a strain section 51 formed by dropping a solution containing a volatile liquid at regular intervals will be described as an example.

[0027] As shown in FIG. 2, the method for manufacturing the optical fiber ribbon 10 of this embodiment includes a step of preparing the ribbon-shaped optical fiber 160 (S110) and a step of forming the grating section 50 (S120).

[0028] In the ribbon-shaped fiber 160 preparation step (S110), a ribbon-shaped fiber 160 having the optical fibers 20 described above is prepared. The ribbon-shaped fiber 160 may be manufactured by any method. For example, the ribbon-shaped fiber 160 may be prepared using the manufacturing apparatus 100 shown in FIG. 3 . Specifically, while the optical fibers 20 are transported in the transport direction A, a tape die 120 applies uncured photocurable resin to the optical fibers 20 in a tape-like manner to form the tape layer 40. Thereafter, the separation needles 132, 134, and 136 of the separation die 130 are raised and lowered relative to the tape layer 40 to remove portions of the tape layer 40 and form the separation portion 41 (and the connection portion 30). Additionally, a resin suction device 138 suctions excess photocurable resin blocked by the lowering of the separation needles 132, 134, and 136. Next, the tape layer 40 is irradiated with light by the light irradiation device 140 to semi-cure the uncured photocurable resin, and finally, the semi-cured photocurable resin is completely cured by further irradiating with light by the light irradiation device 150. Note that the integrated irradiation amount of each of the upstream light irradiation device 140 and the downstream light irradiation device 150 is adjusted so that the integrated irradiation amount of the upstream light irradiation device 140 is smaller and the integrated irradiation amount of the downstream light irradiation device 150 is larger.

[0029] In the step of forming the grating section (S120), as shown in FIG. 3 , the ribbon-shaped fiber 160 manufactured in the step of preparing the ribbon-shaped fiber 160 (S110) is further transported in the length direction (direction indicated by A in the figure) by the above-described manufacturing apparatus 100. Then, the outermost layer of the optical fiber 20 is partially cooled in a predetermined region of the optical fiber 20 in the longitudinal direction of the optical fiber 20. The method for partially cooling the outermost layer of the optical fiber 20 is not particularly limited. Examples of methods for partially cooling the outermost layer of the optical fiber 20 include a method of dripping a solution containing a volatile liquid at regular intervals and a method of cooling at regular intervals using a predetermined method. In this embodiment, a solution containing a volatile liquid is dripped at regular intervals from a strain-generating device 170. The volatile liquid in the solution is then vaporized. The strain-generating device 170 is, for example, an inkjet droplet ejection device. Examples of volatile liquids include methyl ethyl ketone and ethanol. The solution containing a volatile liquid may also contain a dye or a pigment. At this time, the heat of vaporization generated when the volatile liquid evaporates cools and shrinks (distorts) the outermost layer of the optical fiber 20. At this time, the temperature of the outermost layer of the optical fiber 20 is, for example, in the range of 37.3°C or higher, preferably in the range of 50°C or higher, with the lower limit being adjusted depending on the type of volatile liquid. As a result, a strained portion 51 is formed in the optical fiber 20. In this way, stress is applied to the core of the optical fiber 20 based on the strained portion 51 formed in the optical fiber 20, and a grating portion 50 is formed.

[0030] When cooling is performed at regular intervals, a device that partially cools the optical fiber 20 is used as the strain forming device. In this case, the outermost layer of the optical fiber 20 is cooled and contracts (strains). As a result, stress is applied to the core of the optical fiber 20 based on the strained portion 51 formed in the optical fiber 20, and the grating portion 50 is formed. In the device that partially cools the optical fiber 20, the optical fiber 20 may be partially cooled using, for example, liquid nitrogen.

[0031] In addition, in the process of forming the grating section, the grating section 50 based on the strain section 51 may be formed by dripping a solution containing a volatile liquid or by cooling so that the wavelength of light used to be incident on the optical fiber 20 does not overlap with the wavelength of light attenuated by the grating section 50.

[0032] In the above explanation, an example was given in which the device used in the process of preparing the ribbon-shaped core wire (S110) and the device used in the process of forming the grating section (S120) are integrated, but these may also be arranged on separate lines.

[0033] (Effect) As described above, according to the present invention, the grating section 50 is formed by the strain section 51 caused by partially cooling the optical fiber 20, so that an optical fiber ribbon 10 having a grating section 50 formed by a simple method can be obtained.

[0034] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited by these examples, and the embodiments can be modified without departing from the spirit of the present invention.

[0035] (1) Sample Preparation A single-coated optical fiber with an outer diameter of 250 μm was prepared by applying a primary coating made of a urethane acrylate photo-curable resin and a secondary coating made of a urethane acrylate photo-curable resin to a silica glass SM optical fiber with an outer diameter of 125 μm. Twelve single-coated optical fibers were then aligned and coated with a urethane acrylate photo-curable resin to form a tape layer, and joints and separations were formed to obtain a ribbon-shaped optical fiber.

[0036] The optical fiber ribbon was then fabricated by dripping a solution containing a volatile liquid onto the 12 optical fibers of the ribbon at predetermined intervals so that the liquid overlapped the optical fibers, and then drying and cooling the optical fibers to form gratings based on the multiple strained portions. The strained portions were approximately circular in shape and approximately 0.25 mm in size.

[0037] (2) Measurement of Optical Transmission Loss at a Wavelength of 1310 nm Optical transmission loss at a wavelength of 1310 nm was measured. Approximately 3000 m of the manufactured optical fiber ribbon was prepared and wound around a bobbin (assuming it was packed or packaged at high density). In this state, the transmission loss of light at a wavelength of 1310 nm for each optical fiber was measured in accordance with IEC 60793-1-40. Figure 4 shows the relationship between the center-to-center distance of strained portions and optical transmission loss. Figure 4 is a graph showing the relationship between the center-to-center distance of strained portions and optical transmission loss. The horizontal axis of Figure 4 represents the center-to-center distance of strained portions (mm), and the vertical axis represents the optical transmission loss per km (dB / km). The center-to-center distance of the strained portions was set to 0.43 mm, 0.65 mm, 0.86 mm, or 1.29 mm (the minimum center-to-center distance of the strained portions was set to 0.43 mm because this was the lower limit for manufacturing the strain-forming device, and the other center-to-center distances were set to 1.5, 2, or 3 times that value.) As shown in Figure 4, it can be seen that when the center-to-center distance of the strained portions is 0.65 mm, the optical transmission loss of light with a wavelength of 1310 nm can be suppressed.

[0038] It can be seen from FIG. 4 that a grating section based on a plurality of strain sections can be formed by dropping a solution containing a volatile liquid at predetermined intervals and cooling it.

[0039] Next, we investigated the relationship between the center-to-center distance of the strained portions, the wavelength of light incident on the optical fiber ribbon, and the optical transmission loss. Figure 5 shows the relationship between the center-to-center distance of the strained portions 24 hours after the production of the optical fiber ribbon, the wavelength of light incident on the optical fiber ribbon, and the optical transmission loss per km. The upper horizontal axis of Figure 5 represents the center-to-center distance (mm) of the strained portions, the lower horizontal axis represents the wavelength (nm) of light incident on the optical fiber ribbon, and the vertical axis represents the optical transmission loss per km (dB / km). The attenuation wavelength was measured using an OTDR (Optical Time Domain Reflectometer).

[0040] As shown in Figure 5, when the wavelength of the incident light was short (1310 nm, 1383 nm), the optical transmission loss was small when the center-to-center distance between the strained portions was 0.52 mm or more. On the other hand, when the center-to-center distance between the strained portions was 0.43 mm, the optical transmission loss was large. Also, as shown in Figure 5, when the wavelength of the incident light was long (1550 nm, 1625 nm), the optical transmission loss was small when the center-to-center distance between the strained portions was 0.65 mm or more or less than 0.43 mm. On the other hand, when the center-to-center distance between the strained portions was 0.52 mm, the optical transmission loss was large. As such, it can be seen that the attenuation wavelength can be adjusted by controlling the center-to-center distance between the strained portions.

[0041] The optical fiber ribbon obtained by the present invention is useful, for example, as an optical fiber to be used in a high-speed, large-capacity optical fiber communication network.

[0042] REFERENCE SIGNS LIST 10 Optical fiber ribbon 20 Single-coated optical fiber 21 Optical fiber strand 22 Primary coating layer 23 Secondary coating layer 30 Connection section 40 Tape layer 41 Separation section 50 Grating section 51 Strain section 100 Manufacturing device 120 Tape die 130 Separation die 132, 134, 136 Separation needle 138 Resin suction device 140 (Upstream) light irradiation device 150 (Downstream) light irradiation device 160 Ribbon-shaped fiber 170 Strain forming device

Claims

1. An optical fiber ribbon core wire having a plurality of single-core coated optical fibers arranged in parallel, and a tape layer covering the single-core coated optical fibers and partially connecting adjacent single-core coated optical fibers, wherein the single-core coated optical fibers have grating portions based on a plurality of strain portions formed at regular intervals in the longitudinal direction of the single-core coated optical fibers in the tape layer.

2. The optical fiber ribbon core wire according to claim 1, wherein the plurality of strain portions are formed such that the wavelength of light used for the light incident on the single-core coated optical fiber does not overlap with the attenuation wavelength of light by the grating portion.

3. The optical fiber ribbon core wire according to claim 1, wherein the plurality of strain portions are formed such that the wavelength of light different from the wavelength of light used for the light incident on the single-core coated optical fiber overlaps with the attenuation wavelength of light by the grating portion.

4. The optical fiber ribbon core wire according to any one of claims 1 to 3, wherein the plurality of strain portions are formed so as to overlap the single-core coated optical fiber.

5. A step of preparing a tape-shaped core wire having a plurality of single-core coated optical fibers arranged in parallel, and a tape layer covering the single-core coated optical fibers and partially connecting adjacent single-core coated optical fibers, and in the longitudinal direction of the single-core coated optical fibers, dropping a solution containing a volatile liquid at regular intervals or cooling at regular intervals to form a plurality of strain portions at regular intervals in the tape layer so that the center-to-center distance is constant to form a grating. A method for manufacturing an optical fiber ribbon core wire, characterized by including the steps of:

6. The method for manufacturing an optical fiber ribbon core wire according to claim 5, wherein in the step of forming the grating portion, a solution containing a volatile liquid is dropped or cooled so that the wavelength of light used for the light incident on the single-core coated optical fiber does not overlap with the attenuation wavelength of light by the grating portion.

7. In the method for manufacturing an optical fiber ribbon core wire according to claim 5, in the step of forming the grating portion, a solution containing a volatile liquid is dropped or cooled so that the wavelength of light incident on the single-core coated optical fiber overlaps with the wavelength of light attenuation by the grating portion. A method for manufacturing an optical fiber ribbon core wire, characterized by this.

8. In the method for manufacturing an optical fiber ribbon core wire according to any one of claims 5 to 7, the plurality of strain portions are formed so as to overlap the single-core coated optical fiber. A method for manufacturing an optical fiber ribbon core wire, characterized by this.

Images