JP5112373B2 - Optical fiber cord - Google Patents

Description

  The present invention relates to an optical fiber cord incorporating a plurality of optical fiber strands or optical fiber core wires.

  In the present invention, “optical fiber” is a glass fiber having a core and cladding structure, “optical fiber” is an optical fiber coated with UV resin or the like, and “optical fiber core” is an optical fiber strand that is UV-coated. “Optical fiber cord” is defined as an optical fiber or an optical fiber core coated with a high-strength fiber such as an aramid fiber and an outer coating such as a polyimide resin. Note that the present invention includes a case where the optical fiber is not formed as a core wire but is installed in an optical fiber cord in the state of a strand, so that it will be described together with the optical fiber strand or the optical fiber core wire.

  In recent years, with the rapid penetration of optical fiber communication, optical fibers are spreading not only in offices but also in general homes. In a house, wiring the optical fiber cord along the wall may cause a sharp bend and increase the bending loss, which may affect communication. Therefore, the bending loss characteristics of the optical fiber included in the optical fiber cord The hole assist fiber (HAF: Hole Assisted Fiber) which is excellent in this is adopted. In the future, it is expected to be introduced not only in the home but also in various fields. However, since it becomes difficult to distinguish individual wirings at high-density wiring, it is expected to have a core-line control technology that identifies the desired optical fiber. ing.

  In conventional single mode fiber, optical fiber can be contrasted by inputting control light having a wavelength longer than the signal wavelength band into the optical fiber, bending the optical fiber, and monitoring the control light leaking (for example, non-patent document). 1). However, the holey fiber (HAF, photonic crystal fiber, photonic bandgap fiber) has a structure in which bending loss is unlikely to occur, so that the reference light does not leak and the cords are difficult to control. A similar problem seems to exist not only in holey fibers but also in other low bending loss optical fibers.

  2 (a) and 2 (b) show the cross-sectional structure of a conventional two-core optical fiber cord and the state of the optical fiber or the core when bent. In FIG. 2, 11 is a holey fiber or core, 12 is a solid fiber or core, 13 is a tube, 14 is an aramid fiber, and 15 is an outer coating.

  As shown in FIGS. 2 (a) and 2 (b), in an optical fiber cord using a holey fiber strand or a core wire 11, a holey fiber strand or a core wire as an optical fiber strand or a core wire for contrasting the core wires By adding a solid fiber strand or a core wire 12, for example, which easily leaks propagating light from 11, the core wire contrast is realized.

  However, if the optical fiber cord is bent in the vertical direction at the time of the core wire contrast, the holey fiber strand or core wire 11 and the solid fiber strand or core wire 12 in the optical fiber cord are overlapped, and the bending radius is in that state. If the bending becomes excessively large (the bending is large), the holey fiber strand or the core wire 11 is broken, and conversely, the bending becomes excessively small (when the bending is excessively large). (Small curve) may cause problems such as insufficient power (small leakage) of the solid fiber or the light for contrasting from the core 12.

Masahito Ari, Yuji Higashi, Tomotaka Enomoto, Katsaki Suzuki, Noriyuki Araki, Shigenori Uruno, Tsuneichi Watanabe, “Optical Media Network Operation Technology Supporting Expanding Optical Access Networks”, NTT Technical Journal, vol. 18, no. 12, December 2006 pp. 58-61

  The problem to be solved by the present invention is that when a fiber optic cord is bent at the time of optical fiber cord comparison, a plurality of optical fibers existing in the same optical fiber cord are overlapped to break the optical fiber, It is to avoid the lack of power.

In order to solve the above-described problems, the present invention provides an optical fiber cord in which a plurality of optical fiber strands or optical fiber core wires are incorporated, and the plurality of optical fiber strands or optical fiber core wires are optical fiber cords. The cross-sectional shape of at least one optical fiber strand or optical fiber core wire is a shape obtained by drawing two tangent lines from one external point to one circle. When the optical fiber or the optical fiber is moved, a tangent portion of the optical fiber or the optical fiber is in contact with another optical fiber or the optical fiber in an oblique direction. It is what.

  According to the present invention, in the optical fiber cord, the arrangement of the plurality of optical fiber strands or the optical fiber core wires is such that the apex portions of the cross-sectional shapes of the optical fiber strands or the optical fiber core wires are directed in opposite directions. It is characterized by.

  According to the present invention, in the optical fiber cord, a cladding diameter of at least one optical fiber or an optical fiber in the optical fiber core is 100 μm or less.

  In the optical fiber cord, the present invention is characterized in that a plurality of optical fiber strands or optical fiber core wires are housed in a tube having a telescopic function.

  According to the present invention, in the optical fiber cord, at least one holey fiber (hole assist fiber, photonic crystal fiber, photonic bandgap fiber) or trench structure is used as a plurality of optical fiber strands or optical fiber core wires. And at least one or more solid fibers.

  The present invention provides an optical fiber cord using an optical fiber that hardly generates a bending loss even when bending with a small diameter, such as a holey fiber, and by adding a solid fiber for contrasting the core wire in the optical fiber cord. Allows contrast.

  However, if two optical fibers are present in the same cord, there is a concern that the two optical fibers may overlap when bent when the optical fiber is contrasted, and the optical fiber is broken or the optical fiber leakage power is unstable. It is avoided by specializing the shape of the optical fiber. Furthermore, by reducing the cladding diameter of the optical fiber, the mechanical strength against bending can be improved, and the optical fiber breakage can be greatly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS It is related with the 1st Embodiment of this invention, (a) is a cross-sectional view which shows an optical fiber cord, (b) is a side view which shows an optical fiber strand or a core wire. (A) is a cross-sectional view showing a conventional optical fiber cord, and (b) is a side view showing a conventional optical fiber or core. FIG. 4A is a cross-sectional view showing an optical fiber cord, and FIG. 4B is a side view showing an optical fiber or a core wire according to a second embodiment of the present invention. It is a cross-sectional view showing an optical fiber cord according to a third embodiment of the present invention. It is a cross-sectional view showing an optical fiber cord according to a fourth embodiment of the present invention. It is explanatory drawing which shows the number of fracture | ruptures of an optical fiber compared with the conventional optical fiber cord when the optical fiber cord which concerns on embodiment of this invention performs the core line contrast 10,000 times. It is a characteristic view which shows the cladding diameter dependence of the failure rate of HAF. It is a characteristic view which shows the histogram of the optical fiber cord which concerns on embodiment of this invention compared with the conventional optical fiber cord light reception power. It is a characteristic view which shows the tube expansion stress dependence of the optical fiber breaking rate of the optical fiber cord which concerns on embodiment of this invention, and a core line contrast light reception power deviation. It is composition explanatory drawing which shows the connector structure of the optical fiber cord which concerns on embodiment of this invention. It is composition explanatory drawing which shows the optical fiber cord core wire contrast apparatus.

Hereinafter, embodiments of the present invention will be described in detail.
1 (a) and 1 (b) show a special-shaped optical fiber strand or an optical fiber in bending with a specially shaped optical fiber that avoids overlapping at the time of bending of the two-core optical fiber cord according to the first embodiment of the present invention. Shows the condition of the strand or core, 21 is a holey fiber (hole assist fiber, photonic crystal fiber, photonic bandgap fiber), 22 is a holey fiber strand or core, 23 is a solid fiber, and 24 is a solid fiber 25 is a tube, 26 is an aramid fiber, and 27 is an outer coating.

  As shown in FIGS. 1 (a) and 1 (b), in an optical fiber cord using one signal light hole fiber 21, propagating light is likely to leak from the hole fiber 21 as an optical fiber for controlling a core wire. For example, the control of the cords is realized by adding one solid fiber 23 for contrast light.

  As shown in FIG. 1 (a), the cross-sectional shapes of the hollow fiber strand or core wire 22 and the solid fiber strand or core wire 24 are obtained by drawing two tangent lines from one external point to one circle, respectively. is doing. Two hollow fiber strands or core wires 22 and solid fiber strands or core wires 24 are accommodated in a stretchable tube 13. In this case, the holey fiber strands or core wires 22 and the solid fiber strands or core wires 24 are arranged in such a positional relationship that the apex portions of the cross-sectional shape face the opposite direction. Moreover, the cladding diameter of the optical fiber in the holey fiber or core 22 and the solid fiber or core 24 is 100 μm or less. Further, the tube 25 is a tube having an expansion / contraction function.

  In this state, when the optical fiber cord is bent in the vertical direction, if compressive stress is applied in the vertical direction of the holey fiber strands or core wires 22 and the solid fiber strands or core wires 24, one circle is externally attached. Since the asymmetrical and smooth surface obtained by subtracting two tangents from one point is in contact with the diagonal direction, the positions of the holey fiber strand or core wire 22 and the solid fiber strand or core wire 24 are moved up and down. The position is slightly deviated in an oblique direction from the overlapping position, and the difference in curvature radius is reduced. As a result, it is possible to avoid breakage of the optical fiber and to suppress the variation in power of the light for leaking the core wire.

  In the case where the optical fiber cord is bent in the left-right direction or other directions, the above-described problem is unlikely to occur because a plurality of optical fibers do not exist within the same curved surface (surface in the curved radial direction). Become. Further, the distance between the curved surfaces can be made larger than the outer diameter of the clad of the optical fiber by the method of the present embodiment. Optical fiber is mainly made of quartz glass with high hardness, so if the gap between the curved surfaces is larger than the cladding diameter of the optical fiber, it will be flexible even if the optical fiber strands or core wires partially overlap each other. The coated portion of the high optical fiber or the core wire can be deformed to make the bending radius the same.

  3 (a) and 3 (b) show a special-shaped optical fiber strand or a core wire that is bent to avoid overlapping of the optical fibers when the two-core optical fiber cord according to the second embodiment of the present invention is bent. , 31 is a holey fiber, 32 is a holey fiber or core (circular type), 33 is a solid fiber, and 34 is a solid fiber or core (non-wire). (Circular type), 35 is a tube, 36 is an aramid fiber, and 37 is an outer coating.

  As shown in FIGS. 3 (a) and 3 (b), the cross-sectional shape of the solid fiber strand or core wire 34 is a shape obtained by drawing two tangent lines from one external point to one circle. Two hollow fiber strands or cores 32 and solid fiber strands or cores 34 are accommodated in a stretchable tube 35.

  In this state, when the optical fiber cord is bent in the vertical direction, if a compressive stress is applied in the vertical direction of the holey fiber strand or core wire 32 and the solid fiber strand or core wire 34, the solid fiber strand Alternatively, since the oblique surface, which is a shape obtained by drawing two tangents from one external point to one circle of the core wire 34, is in contact with the surface of the hollow fiber strand or the arc of the core wire 32, the solid fiber The position of the strands or the cores 34 is slightly shifted in an oblique direction from the position where they overlap vertically, and the difference in the radius of curvature is reduced. As a result, it is possible to avoid fiber breakage and to suppress the power variation of the light for contrast control.

  In this embodiment, the contact area between the two curved surfaces is small and difficult to slide, and the non-round solid fiber or the portion that is not a flat portion of the core 34 can be a contact point with the circular holey fiber or core 32. For example, the tangential curved surfaces may coincide with each other, and therefore the reliability is inferior to that of the optical fiber cord of FIG. However, the reliability is higher than that of the optical fiber cord of FIG.

  FIG. 4 shows a special-shaped optical fiber or core that avoids overlapping of optical fibers when the three-core optical fiber cord according to the third embodiment of the present invention is bent. 41 is a holey fiber, 42 is a holey fiber or core (non-circular), 43 is a solid fiber, 44 is a solid fiber or core (non-circular), 45 A holey fiber, 46 is a holey fiber or a core wire (circular shape), 47 is a tube, 48 is an aramid fiber, and 49 is an outer coating.

  As shown in FIG. 4, the holey fiber core or core wire 42 and the solid fiber core or core wire 44 are the same as 22 and 24 in FIG. 1 and have the same function. The holey fiber or core 46 has a circular cross-sectional shape.

  When such a three-core optical fiber cord is bent in the vertical direction, the three holey fiber strands or core wires 42 and 46 and the solid fiber strand or core wire 44 move to different curved surfaces. It is possible to avoid a plurality of optical fibers existing in the same optical fiber cord from overlapping each other and causing the optical fiber to break or insufficient power of leaking light for core control.

  Similarly, when the three-core type optical fiber cord is bent in the left-right direction or in other directions, the same curved surface is not formed, so that a plurality of optical fibers existing in the same optical fiber cord are overlapped with each other. Can be prevented from being broken or the power of the light for contrast control is insufficient.

  FIG. 5 shows a special-shaped optical fiber or core that avoids overlapping of the optical fibers during bending of the four-core optical fiber cord according to the fourth embodiment of the present invention, and the optical fiber or core when bent. The state of the wire is shown, 51 is a holey fiber, 52 is a holey fiber or core (non-circular type), 53 is a solid fiber, 54 is a solid fiber or core (non-circular), 55 Holey fiber, 56 holey fiber or core (circular), 57 holey fiber, 58 holey fiber or core (circular), 59, tube, 60, aramid fiber, 61 outer coating is there.

  As shown in FIG. 5, the holey fiber core or core 52 and the solid fiber core or core 54 are the same as 22 and 24 in FIG. The hollow fiber strands or cores 56 and 58 have a circular cross-sectional shape. The holey fiber strands or cores 56 and 58 are arranged on the left and right sides so as to sandwich the holey fiber strands or cores 52 and the solid fiber strands or cores 54 arranged vertically.

  When such a four-core type optical fiber cord is bent in the vertical direction, the three holey fiber strands or core wires 52, 56, 58 and the solid fiber strand or core wire 54 move to different curved surfaces. For this reason, it is possible to avoid that the plurality of optical fibers existing in the same optical fiber cord are overlapped and the optical fiber is broken, or the power of leakage light for controlling the core wire is insufficient.

  Also, when bending the 4-core type optical fiber cord in the left-right direction (the non-circular holey fiber or core 52 and the solid fiber or the top of the core 54 does not overlap) or in other directions In the same way, since the same curved surface is not maintained, it is possible to maintain a certain distance, so that a plurality of optical fibers existing in the same optical fiber cord are overlapped, and the optical fiber is broken or the light for detecting the core wire is leaked. Can be avoided.

  When the four-core optical fiber cord is bent in the left-right direction, as long as the non-circular holey fiber or core 52 and the solid fiber or the top of the core 54 do not overlap, The left and right dents formed by combining the two holey fiber strands or cores 52 and the solid fiber strands or cores 54 are displaced in the vertical direction, so the circular holey fiber strands or cores 56, 58 on the left and right Do not have the same curved surface.

  FIG. 6 shows a configuration of the optical fiber cord shown in FIGS. 1 to 5 with a diameter of 125 μm, which is a cladding diameter of a normal optical fiber, when the optical fiber cord is bent 10,000 times using a curved-type optical fiber contrast device. The result of the number of optical fiber breaks with a diameter of 80 μm is shown.

  FIG. 11 shows an optical fiber cord core wire contrast device, 71 is an optical fiber cord to be measured, 72 is a curved core wire contrast device, 73 is a light receiver, 74 is a solid fiber or core wire, 75 is Holy fiber strand or core wire. That is, the signal light is incident on the holey fiber strand or the core wire 75 of the wired optical fiber cord 71 to be measured, and the reference light is incident on the solid fiber strand or core wire 74. The middle part is curved to cause the reference light to leak, and the light-receiving part 73 receives the leaked control light to perform the contrast control.

  As shown in FIG. 6, 30 or more optical fiber breaks occurred in the configuration of the optical fiber cord of FIG. 2 when the cladding diameter of the optical fiber was 125 μm. By adopting the configuration of the optical fiber cord of FIGS. The optical fiber breakage was 0-2, and a significant improvement was observed. Furthermore, when the clad diameter of the optical fiber was 80 μm, a significant improvement was observed. In the optical fiber cords of FIGS. The optical fiber cord of FIG. 3 was improved over the optical fiber cord of FIG. 2 though the clad diameter of the optical fiber was 80 μm or 125 μm, which was not equivalent to those of FIGS.

  From the above, it has been found that by using the special cross-sectional shape of the optical fiber strand or the core wire and the reduction in the diameter of the optical fiber, which are the constituent requirements of the present invention, highly reliable core wire contrast becomes possible.

  FIG. 7 is a diagram showing an experimental result of the dependency of the failure rate on the cladding diameter when the HAF is wound around a round bar having a radius of 2 mm. As can be seen from FIG. 7, the failure rate rapidly decreases from around the cladding diameter of 100 μm, and it is desirable to make the cladding diameter 100 μm or less. However, since HAF has holes, the HAF cannot be manufactured in the vicinity of the cladding diameter of 50 μm. Therefore, it is desirable to set the cladding diameter to 50 to 100 μm.

  FIG. 8 shows the configuration of the optical fiber cord shown in FIGS. 1 and 2 when 100-core alignment (wavelength: 1650 nm, input signal light power: 0 dBm, cord length: 5 m, clad diameter: 80 μm) (the experimental system is shown in the figure). 11 shows a histogram of received light power of the core contrast device of 11).

  As can be seen from FIG. 8, in the case of the configuration of the optical fiber cord of FIG. 2, the light receiving power is generally low and the variation in the light receiving power is large, so that the core contrast cannot monitor the control light in the low power region. there is a possibility. On the other hand, the configuration of the optical fiber cord of FIG. 1 has a high light receiving power and within a deviation of 20 dB, and enables highly accurate control of the cores. The stretchability of the tube containing the optical fiber or the core also affects the fiber breakage and the stability of light leakage power.

  FIG. 9 is a graph plotting the tube expansion / contraction stress with respect to the deviation of the optical fiber breaking rate and the light receiving power of the core wire contrast device for the optical fiber cord of FIG. As can be seen from FIG. 9, in a region where the tube stretching stress is low to some extent, the deviation between the optical fiber breaking rate and the optical power of the cord contrast tends to decrease as the stretching stress increases. This is because when the optical fiber cord is bent, stress is applied to the internal optical fiber or core due to the elasticity of the tube, and the movement of the optical fiber or core shown in FIG. 1 occurs. . The direction of stress applied to the optical fiber or the core coincides with the direction of the curved surface.

  However, as shown in FIG. 9, if the tube stretching stress becomes too high, the stretching stress in the direction orthogonal to the curved surface also increases, and conversely, the degree of freedom of the optical fiber or core is lost, and the optical fiber Breakage and instability of light leakage power occur. Therefore, it is necessary to optimize the stretchability of the tube. The tube stretchability can be optimized by changing the tube material, tube thickness, and tube structure (such as mesh).

  FIGS. 10A, 10B and 10C show the structure of a connector which is a light introducing portion for signal light and control light to the optical fiber cord according to the embodiment of the present invention. 10 (a), 10 (b), and 10 (c), 81 is a connector, 82 is a ferrule, 83 is a fiber for controlling a core wire, 84 is an optical fiber for signal light propagation, and 85 is an optical fiber cord. The outer sheath 86 is a core-contrast optical bypass.

  In FIG. 10A, the reference light is input / output from the side surface of the connector 81 to the optical fiber 83 for optical fiber comparison. In FIG. 10B, an input / output port is provided on the end face of the connector 81 so that the reference light and the signal light are input / output in correspondence to the optical fiber strand 83 for optical fiber comparison and the optical fiber strand 84 for signal light propagation. ing. In FIG. 10 (c), when two optical fiber cords with an optical connector having the structure shown in FIG. 10 (a) are connected, the reference light emitted from the optical fiber strand 83 for optical control on the side of the connector 81 The light enters the control light input port of the optical fiber strand 83 for the optical fiber 83 on the side of the other connector 81 through the line control light bypass path 86.

  In the embodiment of the present invention, as the special covering shape of the optical fiber or the core, the cross-sectional shape is a shape obtained by drawing two tangents from one external point to one circle, but the same function is obtained. Includes structure. For example, the apex portion of the cross-sectional shape is slightly rounded, or the flat portion where the optical fiber strand or the core wire contacts is slightly rounded. Further, it is desirable that the surface material of the optical fiber or the core is as slippery as possible.

  Furthermore, although the maximum four-core type optical fiber cord has been shown, it goes without saying that the present invention can be applied to a multi-core type optical fiber cord having more than that. Further, although a holey fiber is used as a low bending loss optical fiber for signal light propagation, it can be replaced with a trench structure optical fiber having the same effect.

  Furthermore, not only infrared light but also light having a wide wavelength can be used as the reference light. When visible light is used, it is possible to perform the contrast control by visual recognition without using an instrument such as a core contrast device. Further, when the connector has an exit for the reference light, the connector can be illuminated to make a determination. The results shown above are results under limited conditions, and the scope of the present invention is not limited to these results.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DESCRIPTION OF SYMBOLS 21 ... Holy fiber, 22 ... Holy fiber strand or core, 23 ... Solid fiber, 24 ... Solid fiber or core, 25 ... Tube, 26 ... Aramid fiber, 27 ... Outer coating

Claims (5)

An optical fiber cord containing a plurality of optical fiber strands or optical fiber core wires,
The plurality of optical fiber strands or optical fiber core wires are disposed so as to be movable in the radial direction within the tube of the optical fiber cord, and at least one optical fiber strand or optical fiber core wire has one cross-sectional shape. Ri shape der obtained by subtracting 2 tangent from a point external to the circle, upon movement of the optical fiber or optical fiber, tangential portion of the optical fiber or optical fiber is another optical fiber An optical fiber cord which is in contact with an element wire or an optical fiber core wire in an oblique direction .   2. The light according to claim 1, wherein the arrangement of the plurality of optical fiber strands or the optical fiber cores is such that the apex portions of the cross-sectional shapes of the optical fiber strands or the optical fiber core wires face in opposite directions. Fiber cord.   The optical fiber cord according to claim 1 or 2, wherein a clad diameter of at least one optical fiber strand or an optical fiber in the optical fiber core is 100 µm or less.   The optical fiber cord according to claim 1, 2, or 3, wherein a plurality of optical fiber strands or optical fiber core wires are accommodated in a tube having a telescopic function.   At least one or more holey fibers (hole assist fiber, photonic crystal fiber, photonic bandgap fiber) or at least one optical fiber having a trench structure as a plurality of optical fiber strands or optical fiber cores The optical fiber cord according to claim 1, wherein the optical fiber cord includes a type fiber.

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