JPH0159563B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement of a reinforcing member for an optical fiber connecting portion, which is easy to work with and has excellent reliability. Compared to conventional metal transmission lines, optical fiber cores are
It has various features such as being light, capable of large-capacity transmission, excellent flexibility, and small diameter, but it is necessary to remove a certain length of the coating when connecting, so the tensile strength is originally around 7 kg. However, the weight at the connection part is 1Kg.
It has the disadvantage that it drops below. For this reason, after connecting the optical fibers, it is essential to integrate the connecting portion and the coating layers at both ends of the connecting portion to form a reinforcing portion to protect the connecting portion. Conventionally used reinforcing members include reinforcing members in which the connection part is housed in a sleeve made of plastic or the like and fixed using a reactive bonding agent such as epoxy or silicone, and reinforcing members in which a heat-melt adhesive is used as the reinforcing member. There are reinforcing members, etc. that are used and heated to integrate them with the connecting parts. The former has the advantage of not requiring special equipment during reinforcement, but the connection strength may vary depending on the work environment and the skill level of the worker. The latter requires equipment to heat the adhesive, but provides a more reliable reinforcement. As mentioned above, high-capacity transmission is possible by using optical fibers, but if the optical fiber connections break, the area affected will be large, and the reliability of the connections will be affected. Security has become an important factor. Therefore, the latter is attracting more attention, and a typical reinforcing member is a reinforcing member using a heat-shrinkable tube. As shown in Figure 1, this is done at the connection part of the optical fiber.
A tube 1 made of hot-melt adhesive such as EVA (ethylene vinyl acetate) or nylon is covered, and a tensile strength member 2 made of stainless steel or other material is placed along the tube 1 to protect the connection from external forces. A shrinkable tube 3 is placed over the tube and heated from the outside to shrink the heat-shrinkable tube, and at the same time, the heat-melt adhesive inside is melted and reinforced. In addition, in this method, when the heat-shrinkable tube is shrunk, if air bubbles remain inside the tube, the reliability will be significantly reduced. For this purpose, a divided heater as shown in FIG. 2 is used to gradually shift the heated portion from the center of the connection portion to both ends. In FIG. 2, 3 is a heat shrink tube, B is a coated optical fiber core, 4,
4' is a heater, 5 and 5' are timers, and 6 and 6' are power supplies. In this way, as shown in Figure 3a, the contraction starts from the center, as shown in Figure 3b, the contraction progresses while expelling the bubbles to both ends, and finally as shown in Figure 3c. The contraction is complete. By the way, the metallic tensile strength body inside the heat shrink tube also serves as a heat conduction medium to smoothly transfer heat from the center of the connection part to both ends, so even if the heater structure is simple, heat conduction is difficult. This is done smoothly, and the shrinkage of the heat shrink tube progresses as described above. When reinforced in this manner, as shown in FIG. 4a, the heat-shrinkable tube 3, the tensile strength member 2, and the connecting portion C of the optical fiber core are tightly bonded, and the reinforcement is completed. Note that FIG. 4b is a cross-sectional view taken along line D-D' in FIG. 4a, where A is a bare optical fiber and B is a coated optical fiber. In addition, as another reinforcing member using a hot-melt adhesive, as shown in FIG.
There is a reinforcing member with a heat-melting adhesive 9 applied thereto. When two of these reinforcing members are used to sandwich the optical fiber connection portion in a sandwich-like manner and then heated and compressed from the outside, a reinforcing portion is formed as shown in FIG. 6a. In addition, Fig. 6b is the 6th
FIG. The connecting portion of the optical fiber core fits into the groove 8 shown in FIG. 6b, and does not come into direct contact with the metallic tensile strength member. However, no matter which reinforcing member is used, there is a large difference in thermal expansion coefficient between the metal used for the tensile strength body (stainless steel, zinc alloy) and the optical fiber core, and when used outdoors, Due to monthly and yearly temperature fluctuations or temperature fluctuations due to weather changes, for example, in reinforced parts using heat-shrinkable tubes, optical fiber connections may repeatedly bend or expand and contract like bimetals. do. In addition, it goes without saying that the sandwich-like reinforcing part can cause expansion and contraction of the optical fiber connection part due to temperature fluctuations, and if two reinforcing members are connected with a misalignment or if the adhesiveness is poor, it is especially likely that repeated causes bending. As a result, both of the reinforcing members had the drawback of being unavoidably reduced in long-term reliability. On the other hand, in order to eliminate the influence of such thermal expansion,
If materials other than metals, such as quartz glass or plastic, are used as the tensile strength material, these materials generally have low thermal conductivity, so they transmit almost no heat.
The drawback was that the heating time required to melt the hot-melt adhesive was long, resulting in poor workability. In addition, especially in the method using a heat shrink tube, the shrink position is gradually shifted from the center of the connection part to both ends as described above, so if the tensile strength member does not function as a heat conduction medium, the structure of the heater becomes extremely complicated. It had the disadvantage of becoming. The present invention can also be used as a tensile strength member of an optical fiber core reinforcement member, since the coefficient of thermal expansion is comparable to that of the optical fiber core wire, and
Moreover, it is characterized by the use of a metal with high thermal conductivity, and its purpose is to eliminate repeated bending, expansion and contraction of the optical fiber core connection portion caused by temperature fluctuations, and to shorten the heating time. FIG. 7 shows one embodiment of the present invention, 1 is an EVA
As shown in Table 1, 10 is a metal tensile strength body with a coefficient of thermal expansion comparable to that of the glass optical fiber core and a high thermal conductivity, and 3 is a heat-melting adhesive tube such as It is a shrink tube and is structurally the same as the conventional reinforcing member shown in FIG. 1, and the heating method is also the same. The heating temperature and heating time are selected depending on the type of metal used, and the heating area is gradually moved from the center to both ends of the reinforcing member. Figure 8a shows the structure after completion of reinforcement. Figure 8b
is a sectional view taken along line FF' in FIG. 8a. FIG. 9a is a perspective view of another embodiment of the present invention, and FIG. 9b shows its cross section, 11 is a metal rectangular plate having a coefficient of thermal expansion and thermal conductivity as shown in Table 1, 8 9 is the groove in which the optical fiber connection part is placed.
is a hot-melt adhesive, which is structurally the same as the conventional reinforcing member shown in Figure 5, and the heating and compression method is the same as the conventional one, but depending on the metal used, Select temperature and heating time.
Figure 10a shows the structure after completion of reinforcement. FIG. 10b is a sectional view taken along line GG' in FIG. 10a.

[Table] Next, calculate the stress caused by temperature fluctuations within the optical fiber connection. The reinforcement section is modeled as shown in FIG. A ₁ is the cross-sectional area of the optical fiber model 14, and A ₂ is the tensile strength body model 1.
3, E ₁ and E ₂ are the Young's moduli of the optical fiber model 14 and the tensile strength body model 13, respectively, and α ₁ and α ₂ are the optical fiber model 1, respectively.
4 and the coefficient of thermal expansion of model 13 of the tensile strength body. Initially, there is no stress and both ends are free. When the temperature is increased by t (°C) from this state, the stress generated in the optical fiber model 14 and the tensile strength body model 13 is σ ₁ ,
If σ ₂ , there is no external force, so from the force balance of the entire model, σ ₁ A ₁ +σ ₂ A ₂ = 0 (1) On the other hand, the following occurs in model 14 of the optical fiber core and model 13 of the tensile strength body. The strains ε are equal and consist of one strain due to stress and one due to thermal expansion. ε=σ ₁ /E ₁ +α ₁ t=σ ₂ /E ₂ +α ₂ t (2) When σ 1 , σ ₂ and ε are calculated from equations (1) and ( ₂ ), σ ₁ =E ₁ (α ₂ −α ₁ )t/{1+E ₁ A ₁ /E ₂ A ₂ }, σ ₂ =−E ₂ (α ₂ −α ₁ )t/{1+E ₁ A ₁ /E ₂ A ₂ }=
−σ ₁ A ₁ /A ₂ (3) ε=E ₁ A ₁ α ₁ +E ₂ A ₂ α ₂ /(E ₁ A ₁ +E ₂ A ₂ )t (4). The tensile force f generated on the optical fiber is f=A ₁ σ ₁ = A ₁ E ₁ A ₂ E ₂ (α ₂ −α ₁ )t/(A ₁ E ₁ +A ₂ E ₂
)(5) becomes. FIG. 12 shows the tensile force generated at the optical fiber connector due to temperature fluctuations when stainless steel, tin, or invar is used as the tensile strength member.
As can be found from Figure 12, the temperature at the connection part is 0.
The tensile force that occurs when the temperature changes from ℃ to 40℃ is
Approximately 60g when using stainless steel, approx. 17g when using tin
g, and about 2 g for Invar, so it is more stable against temperature fluctuations if a metal with a small coefficient of thermal expansion is used. However, A ₁ =0.012mm ² and A ₂ =1.8mm ² . Furthermore, metals with high thermal conductivity transfer heat from the outside quickly, reducing heating time.
Improves work efficiency. As explained above, the reinforcing member of the optical fiber connection part of the present invention uses a metal having a coefficient of thermal expansion similar to that of the optical fiber core and a high thermal conductivity as the tensile strength member, so that the reinforcing member can be reinforced. It is possible to eliminate repeated bending and expansion/contraction of the optical fiber connecting portion caused by internal temperature fluctuations, thereby increasing long-term reliability. Also, since heat is conducted quickly during heating, the heating time is shortened. Furthermore, since it is structurally similar to conventional reinforcing members, it has the advantage that heat-melt adhesive tubes such as EVA, heat-shrinkable tubes, etc. can be used as is.

[Brief explanation of drawings]

Figure 1 is a structural diagram of a reinforcing member using a conventional heat-shrinkable tube and a stainless steel tensile strength member, Figure 2 is a conceptual diagram of the heating method for a heat-shrinkable tube, and Figure 3a shows that the shrinkage occurs from the center of the connection. A structural diagram of a reinforcing member using a heat-shrinkable tube that has started, Fig. 3b is a structural diagram of a reinforcing member using a heat-shrinkable tube in which shrinkage is progressing to both ends of the connection part, and Fig. 3c is a structural diagram of a reinforcing member using a heat-shrinkable tube that has completed shrinkage. Structural diagram of a reinforcing member using a heat-shrinkable tube, No. 4
Figure a is a sectional view after reinforcement using Figure 1, Figure 5 a is a perspective view of a conventional Sanderch type reinforcement member,
Fig. 5b is a sectional view of the same, Fig. 6a is a sectional view after reinforcement using Fig. 5, and Fig. 6b is a cross-sectional view of Fig. 6a.
A cross-sectional view at E', Figure 7 is a structural diagram of a reinforcing member using a heat-shrinkable tube and a metal with a low coefficient of thermal expansion and high thermal conductivity is used for the tensile strength body, and Figure 8a is a diagram using Figure 7. Figure 8b is a cross-sectional view taken along F-F' in Figure 8a after reinforcement, Figure 9a is a Sanderch type reinforcement using a metal with a low coefficient of thermal expansion and high thermal conductivity for the tensile strength member. A perspective view of a member for use,
Figure 9b is its cross-sectional view, Figure 10a is a cross-sectional view after reinforcement using Figure 9, Figure 10b is Figure 10a.
FIG. 11 is a model diagram of the reinforcing portion, and FIG. 12 is a diagram showing the relationship between tensile force generated in the optical fiber core due to temperature fluctuation. 1... Heat melt adhesive tube, 2... Stainless steel tensile strength body, 3... Heat shrinkable tube, 4,
4'...Heater, 5,5'...Timer, 6,6'...
...Power source, 7...Rectangular tensile strength body, 8...Groove, 9...
Hot-melt adhesive, 10...Metal tensile strength body with a small thermal expansion coefficient, 11...Metal rectangular tensile strength body with a small thermal expansion coefficient, 12...Rigid body plate, 13...Model of the tensile strength body, 14 ...A model of an optical fiber core, A...A bare optical fiber core, B...A coated optical fiber core wire, C...A connection portion of an optical fiber core wire.

Claims (1)

[Scope of Claims] 1. Reinforcement for reinforcing an optical fiber core connection portion, which is connected by removing the coating layer of the optical fiber core, by heating it from the outside using a hot-melt adhesive and a tensile strength material. 1. A reinforcing member for an optical fiber connection portion, characterized in that the tensile strength member is made of a metal having a coefficient of thermal expansion comparable to that of the optical fiber and a high thermal conductivity. 2. In the reinforcing member for the optical fiber connection portion as set forth in claim 1, the metal tensile strength member is a round bar and is placed along the tube-shaped hot-melt adhesive, and furthermore, the outer part thereof is A member for reinforcing an optical fiber core connection part, characterized in that a heat shrinkable tube is placed over the member. 3. In the reinforcing member for an optical fiber connection part as set forth in claim 1, the metal tensile strength member is in the shape of a rectangular plate with a groove in the center, and a hot-melt adhesive is applied thereon. A reinforcing member for an optical fiber connection part, characterized in that: 4. A reinforcing member for an optical fiber connection portion according to claim 1, wherein the metal tensile strength member is an invar-based metal. 5. A reinforcing member for an optical fiber connection portion according to claim 1, wherein the metal tensile strength member is a Kovar-based metal. 6. In the member for reinforcing the optical fiber connection portion as set forth in claim 1, the metal tensile strength member is any one of tungsten, chromium, gray tin, silicon, ruconium, tantalum, and germanium. A reinforcing member for an optical fiber connection part, characterized by: