Optical fiber cable

Abstract

This optical fiber cable (1) comprises: at least one optical fiber unit (5) that includes a plurality of optical fiber core wires (2); and a cable jacket (8) that covers the at least one optical fiber unit (5). The plurality of optical fiber core wires (2) constitute an intermittent connection-type optical fiber tape core wire (3). In the at least one optical fiber unit (5), the optical fiber tape core wire (3) is provided in plurality and twisted at intervals of a first period along the longitudinal direction. At a low temperature of -30°C or less, the plurality of optical fiber tape core wires (3) are displaced in the circumferential direction from the position at room temperature while periodically inverting at intervals of a second period different from the first period.

Description

fiber optic cable

[0001] The present disclosure relates to fiber optic cables.

[0002] The spread of information communications such as the Internet has led to faster communication speeds and an increase in the amount of information transmitted, and the construction of optical fiber networks is progressing to accommodate two-way communication and large-capacity communication. The expansion of such networks is increasing the demand for optical fiber cables with high-density optical fibers.

[0003] For example, Patent Document 1 discloses an optical fiber cable including an SZ-twisted optical fiber unit.

[0004] International Publication No. 2023 / 120727

[0005] The optical fiber cable according to the present disclosure is an optical fiber cable comprising at least one optical fiber unit including a plurality of optical fiber cores, and a cable jacket covering the at least one optical fiber unit, wherein the plurality of optical fiber cores are arranged in parallel in a direction perpendicular to the longitudinal direction, and among some or all of the plurality of optical fiber cores, connected sections in which adjacent optical fiber cores are connected and non-connected sections in which adjacent optical fiber cores are not connected are intermittently provided in the longitudinal direction, forming an intermittently connected optical fiber ribbon core, wherein at least one of the optical fiber units has the plurality of optical fiber ribbon cores twisted at a first period along the longitudinal direction, and at low temperatures of -30°C or less, the plurality of optical fiber ribbon cores periodically reverse at a second period different from the first period, and their circumferential positions are displaced compared to those at room temperature.

[0006] FIG. 1 is a perspective view showing an example of an optical fiber cable according to an embodiment of the present disclosure. FIG. 2 is a plan view showing the configuration of some optical fiber ribbons included in the unit shown in FIG. 1. FIG. 3 is a block diagram showing the configuration of an internal observation system for an optical fiber cable. FIG. 4 is a graph showing the trajectories of the optical fiber ribbon at room temperature and at low temperatures. FIG. 5 is a cross-sectional view showing the state change of the optical fiber ribbon at room temperature when the unit is SZ-twisted at a first period. FIG. 6 is a cross-sectional view showing the state change of the optical fiber ribbon when a unit made of an optical fiber ribbon without an intermittent structure is placed in a low-temperature environment of −30° C. FIG. 7 is a cross-sectional view showing the state change of the optical fiber ribbon when the optical fiber cable according to an embodiment of the present disclosure is placed in a low-temperature environment of −30° C.

[0007] [Problem to be solved by the present disclosure]

[0008] Ribbon fibers that do not have an intermittent connection structure and are commonly used in optical fiber cables have greater rigidity in the width direction than in the thickness direction, and therefore tend to meander in the thickness direction when the jacket or tube of the optical fiber cable shrinks at low temperatures. Ribbon fibers with an intermittent connection structure also have lower rigidity than general ribbon fibers, but there is a risk that the ribbon fiber will meander in the thickness direction within the optical fiber cable. If a lateral pressure load is applied to the ribbon fiber while it is meandering in the thickness direction, the transmission loss of the optical fiber cable may increase. In order to prevent such an increase in transmission loss, design constraints arise, such as increasing the inner diameter of the cable or tube in advance or using a low-shrinkage material for the jacket or tube of the optical fiber cable. [Effects of the Present Disclosure]

[0009] According to the present disclosure, an optical fiber cable can be provided that suppresses an increase in transmission loss at low temperatures.

[0010] [Description of Embodiments of the Present Disclosure] An outline of an embodiment of the present disclosure will be described below. (1) An optical fiber cable comprising at least one optical fiber unit including a plurality of optical fibers, and a cable jacket covering the at least one optical fiber unit, wherein the plurality of optical fibers are arranged in parallel in a direction perpendicular to a longitudinal direction, and constitute an intermittently connected optical fiber ribbon, in which some or all of the plurality of optical fibers have connected portions where adjacent optical fibers are connected and non-connected portions where adjacent optical fibers are not connected, intermittently provided along the longitudinal direction, and in at least one of the optical fiber units, the plurality of optical fiber ribbons are twisted in a first period along the longitudinal direction, and at a low temperature of −30° C. or less, the plurality of optical fiber ribbons periodically reverse their twists in a second period different from the first period, and their circumferential positions are displaced compared to those at room temperature.

[0011] According to the above configuration, at low temperatures, the optical fiber ribbon periodically reverses its orientation at a second period different from the first period, and its circumferential position is displaced in the longitudinal direction compared to that at room temperature (hereinafter also referred to as SZ meandering). This prevents an increase in the lateral pressure load that the optical fiber units receive from the cable jacket and the inner surface of the tube that surrounds each optical fiber unit, thereby suppressing an increase in transmission loss.

[0012] (2) The optical fiber cable according to item (1), wherein the plurality of optical fiber cores are in the form of an optical fiber ribbon core with each core intermittently intermittent.

[0013] According to the above configuration, since the optical fiber ribbon is in the form of an intermittent type optical fiber ribbon, there is a high proportion of non-connected parts, making it easier for the optical fiber ribbon to meander in an SZ direction, which further prevents an increase in the lateral pressure load received from the cable jacket and the inner surface of the tube that surrounds each optical fiber unit, and suppresses an increase in transmission loss.

[0014] (3) The optical fiber cable according to item (1) or (2), wherein the intermittently connected optical fiber ribbon has an intermittent pitch of 50 mm or more and 150 mm or less in the non-connected portions, and the bonding length of the connected portions is 5 mm or more and 30 mm or less.

[0015] According to the above configuration, since the optical fiber ribbon tends to meander at a period corresponding to the interval pitch of the non-connected portions, it can be made to meander at an appropriate second period. Furthermore, by setting the bonding length to be 5 mm or more and 30 mm or less, the optical fiber ribbon can have appropriate rigidity.

[0016] (4) The optical fiber cable according to any one of items (1) to (3), wherein the second period is shorter than the first period, and the second period is 50 mm or more and 90 mm or less.

[0017] According to the above configuration, the second period is shorter than the first period, and is not less than 50 mm and not more than 90 mm, so that the wire can be made to meander at an appropriate second period.

[0018] (5) An optical fiber cable according to any one of items (1) to (4), wherein the total cross-sectional area of ​​the plurality of optical fiber cores is S1, the cross-sectional area of ​​the inner region of the optical fiber cable surrounded by the cable jacket is S2, and the filling rate of the optical fiber cable is S1 / S2, the filling rate is 30% or more and 60% or less.

[0019] According to the above configuration, the filling rate is 30% or more, so a high-density optical fiber cable can be obtained. Also, since the filling rate is 60% or less, the transmission loss does not increase.

[0020] <Details of the Embodiments of the Present Disclosure> Specific examples of optical fiber cables according to the embodiments of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0021] [Configuration of Optical Fiber Cable] Fig. 1 is a perspective view showing an example of an optical fiber cable 1 according to an embodiment of the present disclosure. As shown in Fig. 1, the optical fiber cable 1 includes a core 6 including a plurality of optical fiber units 5 (hereinafter also referred to as units 5), a holding winding tape 7 wound around the core 6, and a cable jacket 8 covering the holding winding tape 7. The core 6 is a cable core portion of the optical fiber cable 1. Each unit 5 in the core 6 includes an optical fiber ribbon 3 formed by connecting a plurality of optical fiber core wires 2, and the plurality of optical fiber core wires 2 are surrounded by, for example, a hollow tube 4. Note that the tube 4 may be omitted, and the optical fiber ribbon 3 may be in direct contact with the cable jacket 8.

[0022] Fig. 2 is a plan view showing the configuration of some of the optical fiber ribbons 3 included in the unit 5 shown in Fig. 1. In the example shown in Fig. 2, 12 optical fiber core wires 2 are shown, and the 12 optical fiber core wires 2 form the 12-core optical fiber ribbon 3. The 12 optical fiber core wires 2 are intermittently connected to adjacent optical fiber core wires 2.

[0023] Specifically, between adjacent optical fiber cores 2, connected portions 41 in a connected state along the longitudinal direction and non-connected portions 42 in an unconnected state are alternately provided.

[0024] The 12-fiber ribbon 3 is not limited to the configuration shown in FIG. 2, and for example, the non-connected portion 42 may be provided for every two or more optical fibers 2.

[0025] 1 includes, for example, six 12-fiber ribbons 3. That is, each unit 5 includes 72 optical fibers 2. The six optical fiber ribbons 3 included in each unit 5 may be pre-twisted (twisted together), or may be bundled together without pre-twisting.

[0026] The core 6 shown in FIG. 1 includes, for example, six units 5, and these units 5 are periodically twisted together. The final twist may be a spiral twist or an SZ twist. Alternatively, each unit 5 may be twisted individually. The twist angle of the final twist (the maximum twist angle in the case of an SZ twist) is θ1, and the period of the final twist is the first period T1. The number of units 5 may be one, in which case the period of twisting each unit 5 alone is the first period T1.

[0027] The holding winding tape 7 is wound longitudinally along the length of the optical fiber cable 1. The holding winding tape 7 is wound so that, for example, the ends in the width direction overlap each other to form an overlapping portion. The holding winding tape 7 may be, for example, a nonwoven fabric made of fibers such as polyester, polyethylene, or polypropylene.

[0028] The cable jacket 8 is formed by extruding a resin around the holding and wrapping tape 7. The resin used to form the cable jacket 8 is made of, for example, PVC (polyvinyl chloride), polyethylene, or the like.

[0029] [Internal Observation System for Optical Fiber Cable] An example of an internal observation system 1000 for observing the inside of an optical fiber cable at low temperatures will be described. Fig. 3 is a block diagram showing the configuration of the internal observation system 1000 for an optical fiber cable. The internal observation system 1000 observes the internal structure of an optical fiber cable 1 using X-rays, and is thereby able to observe the internal structure of the optical fiber cable 1 at room temperature and at low temperatures. The internal observation system 1000 includes, for example, a room-temperature X-ray device 100A, a low-temperature X-ray device 100B, an image processing device 200, and an observation device 300.

[0030] The room-temperature X-ray device 100A includes an X-ray imaging device, and performs X-ray CT imaging of the optical fiber cable 1 placed in a room-temperature environment to generate and output room-temperature X-ray images 10(i) (i = 1 to N) of multiple cross sections perpendicular to the longitudinal direction of the optical fiber cable 1. The room-temperature X-ray images 10(i) are a group of cross-sectional images for each length α in the longitudinal direction of the optical fiber cable 1, and are acquired for a portion of approximately 10 to 20 cm of the entire sample. N is approximately several thousand.

[0031] The low-temperature X-ray device 100B includes an X-ray imaging device and a cooling container, and performs X-ray CT imaging of the optical fiber cable 1 in a low-temperature environment to generate and output low-temperature X-ray images 20(i) (i = 1 to N) of multiple cross sections perpendicular to the longitudinal direction of the optical fiber cable 1. The low-temperature X-ray images 20(i) are a group of cross-sectional images for each length α in the longitudinal direction of the optical fiber cable 1, and are obtained for a portion of approximately 10 to 20 cm of the entire sample.

[0032] The image processing device 200 performs correction on the low-temperature X-ray image 20(i) of the optical fiber cable 1 to make the image clearer, thereby generating and outputting a low-temperature corrected X-ray image 30(i).

[0033] The observation device 300 detects the center position of the cross section of each optical fiber of the optical fiber cable 1 included in the input room temperature X-ray image 10(i) or the low temperature corrected X-ray image 30(i) (hereinafter collectively referred to as X-ray image 30(i)). As a method for detecting the center position, for example, a method is used in which the image is binarized, then subjected to distance conversion processing, and the pixel with the highest value in the image after distance conversion is determined to be the center position of each object.

[0034] [Trajectory of Optical Fiber Unit] The trajectory of the optical fiber unit at room temperature and at low temperature will be described. The trajectory of the optical fiber unit can be determined, for example, by averaging the center positions of the cross sections of the optical fibers 2 observed using the internal observation system 1000.

[0035] The optical fiber cable sample to be observed includes six units 5, each unit 5 including 72 optical fibers 2, each including six 12-fiber ribbons 3. The optical fiber ribbon 3 has a single-fiber intermittent structure in which a non-connected portion 42 is provided for each optical fiber 2, the intermittent pitch of the non-connected portions 42 being 50 mm or more and 150 mm or less, and the bonding length of the connected portion 41 being 5 mm or more and 30 mm or less. Furthermore, the six units 5 are periodically twisted with an SZ twist at a first period T1. Specifically, the first period T1 is 1000 mm or more and 1500 mm or less, and the twist angle θ1 is 250° or more and 300° or less.

[0036] 4 is a graph showing the trajectories of the optical fiber ribbon 3 at room temperature and at low temperatures. The horizontal axis represents the longitudinal position Z of the optical fiber ribbon 3, and the vertical axis represents the twist angle θ relative to the longitudinal direction of the optical fiber ribbon 3. The waveform W1 shown by the solid line represents the twist angle θ of the optical fiber ribbon 3 at room temperature, and the waveform W2 shown by the dashed line represents the twist angle θ of the optical fiber ribbon 3 at a low temperature of −30° C.

[0037] Comparing waveforms W1 and W2, waveform W1 has a sine wave shape and indicates that the units 5 are twisted together with a first period T1 and a first twist angle θ1. In contrast, waveform W2 has a shape in which a shorter-period sine wave is superimposed on waveform 1. At low temperatures, the optical fiber ribbon 3 periodically reverses its orientation along the inner surface of the tube 4 with a second period T2 different from the first period T1, and its circumferential position is displaced in the longitudinal direction (SZ meandering) compared to waveform W1 at room temperature. Specifically, the second period T2 is 50 mm or more and 90 mm or less, and the optical fiber ribbon 3 performs SZ meandering in the longitudinal direction while fluctuating between +50° and +70° and between -50° and -70° with respect to the first twist angle θ1 in the second period. In this case, the second period T2 was approximately 1 / 17 of the first period.

[0038] How the position of the optical fiber ribbon 3 changes within the unit 5, such as SZ meandering, will be described in detail with reference to Figures 5 to 7. Note that Figures 5 to 7 show cross sections along the longitudinal direction, and for simplification, there is only one unit 5, and the tube 4 is not included. Also, the black dots shown in Figures 5 to 7 represent the same optical fiber in the same optical fiber ribbon 3.

[0039] 5 is a cross-sectional view showing the state change of the optical fiber ribbon 3 at room temperature when the unit 5 is SZ-twisted at the first period T1. It can be seen that the circumferential position of the optical fiber ribbon 3 moves along the longitudinal direction in accordance with the twisting direction indicated by the arrow A1.

[0040] 6 is a cross-sectional view showing the change in state of the optical fiber ribbon 3 when a unit 5 including the optical fiber ribbon 3 having a non-intermittent structure is placed in a low-temperature environment of −30° C. The optical fiber ribbon 3 moves along the longitudinal direction in the twisting direction indicated by the arrow A1 at a first circumferential position T1, and also meanders in the radial direction A2 of the unit 5. In the example shown in FIG. 6, the optical fiber ribbon 3 meanders in the vertical direction A2 on the page. As a result, the optical fiber ribbon 3 comes into contact with the cable jacket 8, and the lateral pressure load received from the inner surface of the cable jacket 8 increases the transmission loss.

[0041] 7 is a cross-sectional view showing a change in the state of the optical fiber ribbon 3 when the unit 5 of the optical fiber cable 1 according to the embodiment of the present disclosure is placed in a low-temperature environment of −30° C. The optical fiber ribbon 3 not only moves in the circumferential direction along the longitudinal direction in accordance with the twisting direction indicated by the arrow A1 at a first period T1, but also finely fluctuates (oscillates) in the direction indicated by the arrow A3 at a second period T2. In this way, the optical fiber ribbon 3 meanders in an SZ pattern along the inner surface of the cable jacket 8, so transmission loss does not increase.

[0042] According to the above configuration, the optical fiber ribbon 3 included in the unit 5 has an intermittent structure, and therefore, it is considered that the difference in rigidity between the width direction and the thickness direction is small. At low temperatures, the optical fiber ribbon 3 displaces along the longitudinal direction (SZ meandering) along the inner surface of the tube 4 while periodically reversing its direction at a second period T2 different from the first period T1. The optical fiber ribbon 3 displaces not only in the thickness direction but also in the width direction, which prevents an increase in the lateral pressure load that the optical fiber ribbon 3 receives from the inner surface of the tube 4 and suppresses an increase in transmission loss. Furthermore, because the optical fiber ribbon 3 has an intermittent fiber-by-fiber configuration, the proportion of non-connected portions 42 is high, making the optical fiber ribbon 3 more likely to undergo SZ meandering. This further prevents an increase in the lateral pressure load that the optical fiber ribbon 3 receives from the inner surface of the tube 4 and suppresses an increase in transmission loss. In addition, when the tube 4 is not provided, the optical fiber ribbon 3 displaces in the longitudinal direction (SZ meandering) while periodically reversing its direction at a second period T2 different from the first period T1 along the inner surface of the cable jacket 8. In this case as well, an increase in the lateral pressure load that the optical fiber ribbon 3 receives from the inner surface of the cable jacket 8 can be prevented, and an increase in transmission loss can be suppressed.

[0043] In addition, in a cross section perpendicular to the longitudinal direction of the optical fiber cable 1, if the total cross-sectional area of ​​the multiple optical fiber cores 2 is defined as S1, the cross-sectional area of ​​the inner region surrounded by the cable jacket 8 of the optical fiber cable 1 is defined as S2, and the filling rate of the optical fiber cable 1 is defined as S1 / S2, the above optical fiber cable sample had a filling rate of 30% or more and 60% or less at room temperature and at low temperatures. In addition, the cable shrinkage amount at low temperature compared to room temperature was approximately 0.5%.

[0044] Although the embodiments of the present invention have been described above, it goes without saying that the technical scope of the present invention should not be construed as being limited by the description of the present embodiments. The present embodiments are merely examples, and it will be understood by those skilled in the art that various modifications of the embodiments are possible within the scope of the invention described in the claims. Thus, the technical scope of the present invention should be determined based on the scope of the invention described in the claims and its equivalents.

[0045] 1: Optical fiber cable 2: Optical fiber core wire 3: Optical fiber ribbon core wire 4: Tube 5: Optical fiber unit 6: Core 7: Holding winding tape 8: Cable jacket 10(i): X-ray image at room temperature 20(i): X-ray image at low temperature 30(i): Corrected X-ray image at low temperature 41: Connected portion 42: Unconnected portion 100A: X-ray device for room temperature 100B: X-ray device for low temperature 200: Image processing device 300: Observation device 1000: Internal observation system θ1: First twist angle T1: First period T2: Second period

Claims

1. An optical fiber cable comprising at least one optical fiber unit including a plurality of optical fiber core wires, and a cable jacket covering the at least one optical fiber unit, wherein the plurality of optical fiber core wires are arranged in parallel in a direction perpendicular to the longitudinal direction, and among some or all of the plurality of optical fiber core wires, connected sections in which adjacent optical fiber core wires are connected and non-connected sections in which adjacent optical fiber core wires are not connected are intermittently provided in the longitudinal direction, forming an intermittently connected optical fiber ribbon, wherein in at least one of the optical fiber units, the plurality of optical fiber ribbon core wires are twisted in a first period along the longitudinal direction, and at low temperatures of -30°C or less, the plurality of optical fiber ribbon core wires periodically reverse their orientation in a second period different from the first period, and the circumferential positions of the plurality of optical fiber ribbon core wires are displaced compared to at room temperature.

2. The optical fiber cable according to claim 1, wherein the plurality of optical fiber core wires are in the form of an optical fiber ribbon core wire with each core intermittently intermittent.

3. The optical fiber cable according to claim 1 or 2, wherein the intermittently connected optical fiber ribbon has an intermittent pitch of 50 mm or more and 150 mm or less in the non-connected portions, and the adhesive length of the connected portions is 5 mm or more and 30 mm or less.

4. An optical fiber cable according to any one of claims 1 to 3, wherein the second period is shorter than the first period, and the second period is not less than 50 mm and not more than 90 mm.

5. An optical fiber cable as described in any one of claims 1 to 4, wherein when the total cross-sectional area of the plurality of optical fiber cores is S1, the cross-sectional area of the inner region of the optical fiber cable surrounded by the cable jacket is S2, and the filling rate of the optical fiber cable is S1 / S2, the filling rate is 30% or more and 60% or less.

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