JP4360632B2 - Fiber optic connector. - Google Patents

Description

  The present invention relates to an optical fiber connector in which a fusion spliced portion in which optical fibers having different outer diameters are fusion-connected is disposed inside.

  SC connectors (Square-shaped Snap-on Plastic Connectors) and FC connectors (F01 type single-core optical fiber connectors defined in JIS C 5970) are representative of those that can easily connect and disconnect optical fibers. Various optical fiber connectors have been proposed.

  FIG. 3 shows an SC connector 10 which is a kind of single-core optical connector. A normal SC connector 10 includes a ferrule 11 made of zirconia at the tip, a spring 12 that applies pressure to the ferrule 11 at the rear, and a housing 13 that contains the ferrule 11 and the spring 12. As shown in FIG. 4, a normal optical fiber 21 of a normal optical fiber core wire 20 is bonded and fixed to the fine hole 11 ′ of the ferrule 11, and a tip portion 21 ′ of the normal optical fiber 21 is an outlet of the fine hole 11 ′. Flat or oblique polishing is performed at the end 11'a. Normally, the optical fiber 21 has a portion 22 positioned at the inlet portion 11′b of the fine hole 11 ′ of the ferrule 11 when the coating layer is removed. The optical fiber core wire 20 and the ferrule 11 are positioned by abutting against “b”.

These optical connectors are mainly for connecting the same type of optical fibers.
On the other hand, as a single mode optical fiber, a standard optical fiber having an outer diameter of 125 μφ and a mode field diameter of about 10 μm has been widely used so far and has been laid in a trunk line (underground) or aerial. Furthermore, with the spread of FTTH (Fiber To The Home) in recent years, optical fibers have been laid in the home.

It is known that microbending loss occurs when the standard optical fiber is bent to a small diameter (especially a radius of 30 mm or less). Considering handling and wiring in the home, it is required that microbending loss does not occur even when bent to a smaller diameter. For this reason, in recent years, small-diameter bendable optical fibers having a large relative refractive index difference Δ between the core and the clad have been used for home wiring and the like. However, such a small-diameter bending-compatible optical fiber has a small MFD (Mode Field Diameter), and connection with a standard optical fiber becomes a problem.
Therefore, as a technique for connecting two types of single-mode optical fibers having different MFDs as described above, for example, the following method has been proposed. (For example, Non-Patent Document 1, Patent Document 1)

2003 IEICE General Conference C-3-63 JP-A-2004-4389

  That is, in the invention disclosed in Non-Patent Document 1, an MFD conversion unit configured by a so-called TEC (Thermally Difused Expanded Core) process in which a core diameter of an optical fiber is diffused by heat treatment is used. It is the method of arrange | positioning between these and comprising a connector. However, when making a connector using a conversion part that has converted MFD by TEC, the core part in the optical fiber gradually expands with respect to the outer diameter by TEC, so the conversion part at the part that matches the core diameter of SMF to be connected, for example The optical fiber must be cut. Therefore, there has been a problem that the cutting position of the optical fiber constituting the TEC-treated conversion unit must be managed with high accuracy.

  The invention disclosed in Patent Document 1 is a technique for matching core diameters by fusion-splicing optical fibers having different mode fields and then performing heating with a burner or the like. This method is less expensive than the core diameter conversion method using TEC. However, after fusing, there is a problem that an apparatus for heating the optical fiber is necessary.

Also, according to the above method, in order to position the fused portion inside the ferrule, the position of the fused portion is accurately grasped, and the optical fiber is bonded at a position where the fused portion does not protrude from the tip of the ferrule. And ferrule polishing must be done.
That is, a fused optical fiber has a bare optical fiber of several millimeters between the fused portion and the clothes being peeled off due to the convenience of a fusing machine. If the optical fiber core wire is inserted into the optical fiber 26, the fused portion 28 between the small-diameter bending-supporting optical fiber 26 and the standard optical fiber 27 may jump out from the outlet end 11'a of the fine hole 11 'as shown in FIG. there were.
Therefore, in order to fit the fusion part 28 in the connector, it has been necessary to manage the length from the time when the clothes are peeled off by the fusion machine to the fusion point, the length of the fine holes, and the like with high accuracy.
The object of the present invention is to solve the above problems.

  The present invention has been made in view of the above points, and in order to solve the above-described problems, in the present invention, two types of single-mode optical fibers are fused, and the fused portion is slightly smaller than a normal optical fiber diameter. It is characterized by an inflated shape so that it does not enter the fine holes of the ferrule.

  In other words, when the two optical fibers are butted and fused, the discharge is usually started at a distance of several microns, they are completely aligned during heating, and finally the longitudinal shape of the optical fiber is uniform. The process of pulling each other's optical fiber to several μm so as to become, but by adjusting the amount of pulling the optical fiber, which is the last process here, it was larger than the diameter of the micro-hole of the optical connector It is possible to finish the fusion in the state. Further, it is characterized in that the creation of the MFD conversion part is completed only by overheating by additional discharge of the fusion rather than heating with a burner after the fusion.

  The optical fiber thus fused does not enter the fine hole of the ferrule because the fused part, that is, the conversion part of the core swells. Therefore, when assembling this optical fiber in the optical connector, the optical fiber that swells immediately before the minute hole stops, so that it is possible to position the fusion part, that is, the MFD conversion part, and from the ferrule tip to the fusion part. Will not jump out.

Further, if the fine holes of the ferrule made of zirconia are formed over almost the entire length, the distance from the connector tip to the fused portion becomes large. Considering the peeling length of the coating layer of the optical fiber due to the fusion, the state of the optical fiber extends to the rear in the connector, and there is a possibility that the assembly by the same method as that of a normal single-core connector cannot be performed. Therefore, when the fused optical fiber according to the present invention is made into a connector, the following method can be used in addition to using a normal zirconia ferrule.
That is, a ferrule formed so as to leave only a small number of fine holes from the connector end face is used. According to this method, the fused portion can be positioned inside the ferrule, and the optical fiber can be peeled off at the connector end face side from the above method. Even in consideration of the length, it can be assembled by the same method as a normal single-core connector.

  According to the connector having the fused optical fiber according to the present invention, the MFD conversion portion can be reliably retained in the ferrule and can be easily positioned.

The ferrule is characterized in that it has a tapered portion with an increased inner diameter at the inlet end of the small-diameter hole.
The optical fiber ferrule is characterized in that an enlarged diameter hole having an inner diameter larger than the inner diameter of the fine hole is arranged at the inlet end of the fine hole.
The ferrule is characterized in that a V-groove substrate is disposed at the inlet end of the microhole.
The fine holes of the ferrule are characterized by being made of zirconia.
The length of the micropore is 1 to 2 mm.

The present invention will be described below with reference to illustrated embodiments.
In FIG. 1, 11, 11 ′, 11 ′ a, and 11 ′ b are a ferrule made of zirconia, a fine hole, an outlet end, and an inlet portion, respectively, as in FIG. 4. 30 is a standard optical fiber, 40 is a small-diameter bending-supported optical fiber, and 50 is a fused portion.
The standard optical fiber 30 has an outer diameter of 125 μmφ and a mode field diameter of about 10 μm, and can tolerate optical transmission loss with respect to a bending of a radius of about 30 mm. The small-diameter bendable optical fiber 40 is formed by coating a small-diameter bendable optical fiber 41 with a coating layer 42, and the small-diameter bendable optical fiber 21 has an outer diameter of 125 μmφ and a mode field diameter of about 6 μm. Thus, the optical transmission loss can be tolerated with respect to the bending with a bending radius of about 7.5 mm.

  The fused portion 50 is obtained by fusion-connecting the standard optical fiber 30 and the small-diameter bending-compatible optical fiber 41. In the fusion, the discharge time is made longer than the conditions for fusing ordinary standard single mode optical fibers. By increasing the discharge time, more heat is applied to the optical fiber, and the additive of the small-diameter optical fiber is thermally diffused to form the MFD conversion portion. In the fusion splicing, the diameter of the optical fiber is usually constant over the entire length, but according to the fusing in this embodiment, the MFD conversion section is made possible by extending the discharge time and optimizing the amount of tension. The optical fiber in can be slightly inflated. Or, in normal fusion splicing, A. Start discharge in a state separated by several μm before fusing, b) Match the optical fibers while the optical fibers are heated, c. To make the diameter of the optical fibers uniform Whereas the fused portion is formed through a process of pulling at least one of the optical fibers, in the fusion and MFD conversion portion creation in the present embodiment, the fusion is performed by appropriately adjusting the process C. The unit, that is, the MFD conversion unit can be inflated.

In this embodiment, the optical fiber connected in this way is made into an SC connector. The ferrule 11 made of zirconia used for a single-core connector such as an SC connector has a fine hole 11 ′ through which the standard optical fiber 30 passes at the tip, and the diameter is from φ125 μm of the bare optical fiber of the standard optical fiber 30. Is also formed slightly thicker. According to the present embodiment, the fused portion is characterized by being in a state of being swollen more than the diameter of the standard optical fiber 30, and the maximum diameter is formed to be approximately 126 to 127 μm. Therefore, the fused part 50 cannot enter the fine hole 11 ′ and is positioned in a state where it is in contact with the inlet 11 ′ b of the fine hole 11 ′.
Further, by shortening the fine hole 11 ′ of the ferrule 11 to about 1-2 mm, the coating layer 42 of the small-diameter bending-supporting optical fiber core wire 40 can be shifted to the outlet end 11′b side from the first embodiment.

  In addition to using the two types of optical fibers described above, the MFD can use an intermediate optical fiber to further reduce transmission loss. For example, when a small-diameter bendable optical fiber is used for home wiring, and SM optical fiber is used for in-home equipment, the MFD6 optical fiber and MFD8 optical fiber are fused and connected by the above method. This is a method of making a connector and connecting it to a normal SM optical fiber.

ｗ_１：モードフィールド半径１
ｗ_２：モードフィールド半径２
ｄ ：軸ズレ量 The connection loss L when two types of optical fibers having different mode field diameters are connected is generally expressed as follows.
L = −10 · log ₁₀ T (dB)
here

w ₁ : Mode field radius 1
w ₂ : Mode field radius 2
d: Axis misalignment

For this reason, when a standard optical fiber with a mode filled radius of 5 μm is connected to a small-diameter bending-compatible optical fiber with a mode filled radius of 3 μm, the amount of misalignment between the mutual optical fibers is 0.5 μm.
T = 0.7672
L = 1.1510
It becomes. Therefore, the estimated mismatch loss is formed to 1.15 dB. Similar results were also obtained in an example in which a standard optical fiber having the above values and a small-diameter bending-compatible optical fiber were connected.

When an intermediate optical fiber having a mode filled radius of 4 μm is disposed between a standard optical fiber having a mode filled radius of 5 μm and a small-diameter bendable optical fiber having a mode filled radius of 3 μm (axial deviation of 0.5 μm), the standard optical fiber is used. And the connection with the intermediate optical fiber,
T1 = 0.9403
L1 = 0.2674
In addition, in the connection between the intermediate optical fiber and the small-diameter bendable optical fiber,
T2 = 0.9034
L2 = 0.4414
It is represented by Therefore, the total loss is L1 + L2 = 0.71 dB. This value was also confirmed in the example, and a transmission loss smaller than that in the example 1 could be obtained.

FIG. 2 shows another embodiment of the present invention, and shows a case where the present invention is applied to a built-in optical fiber of a simple connection type optical connector. In FIG. 2, 60 is a ferrule, 60 'is a fine hole, 70 is an optical fiber mounting substrate, 71 is a core wire cover lid, 72 is a fiber cover lid, and 80 is a built-in optical fiber.
The ferrule 60 is fixed to one end of the optical fiber mounting substrate 70. The built-in optical fiber 80 is configured by fusing and connecting the standard optical fiber 30 and the small-diameter bending-supporting optical fiber 41 in the first embodiment at the fusion part 50, and the fusion part 50 is an entrance part of the fine hole 60 ′. The standard optical fiber 30 is disposed in the fine hole 60 ′, and the small-diameter bending-supporting optical fiber 41 is further mounted on a part of the optical fiber mounting substrate 70.
The optical fiber placement substrate 70 and the core wire cover lid 71, and the optical fiber placement substrate 70 and the fiber cover lid 72 are arranged so as to approach each other by a fastener (not shown) to form a simple connection type optical connector. Yes.

Reference numeral 90 denotes a small-diameter bendable optical fiber core wire attached to the simple connection type optical connector, and the small-diameter bendable optical fiber core wire 90 is formed in the same manner as the small-diameter bendable optical fiber 41. 91 and a coating layer 92 coated thereon.
In order to arrange the small-diameter bendable optical fiber 90 in the simple connection type optical connector as shown in the figure, the optical fiber placement substrate 70, the core wire cover lid 71, the optical fiber placement substrate 70, and the fiber are used by a diameter expanding tool (not shown). The space between the cover lid 72 and the cover lid 72 is widened and disposed at a predetermined position, and thereafter the diameter expansion tool is removed, and the small-diameter bending-supporting optical fiber 90 and the small-diameter bending-supporting optical fiber 91 are disposed on the optical fiber mounting substrate 70. .

The principal part sectional drawing which shows one Example of this invention. The other Example of this invention is shown, A is principal part sectional drawing, B is principal part expanded sectional view. The connector in an example of the prior art is shown. A is a plan view, B is a left side view, C is a partially sectional front view, and D is a right side view. The principal part sectional drawing in an example of the past. Sectional drawing of the principal part in the other conventional example.

Explanation of symbols

11 Ferrule 11 ′ Fine hole 11′a Outlet end 11′b Inlet part 30 Standard optical fiber 40 Small-diameter bendable optical fiber core wire 41 ′ Small-diameter bendable optical fiber 42 Coating layer 50 Fusion part 60 Ferrule 60 ′ Fine hole

Claims (7)

A first optical fiber;
A second optical fiber;
A first microfiber extending between an inlet end and an outlet end, passing through the first optical fiber, communicated with the inlet end of the microhole, and larger than the inner diameter of the first microfiber. And a ferrule formed with an enlarged hole having an inner diameter that allows the second optical fiber to pass therethrough,
A fusion part in which one end face of the first optical fiber and one end face of the second optical fiber are fusion-bonded to each other is disposed in the enlarged-diameter hole;
In the optical fiber connector arranged so that the other end face of the first optical fiber faces the exit end of the microhole,
The optical fiber connector, wherein the fused portion has an outer diameter larger than an inner diameter of the fine hole and smaller than an inner diameter of the enlarged hole . 2. The optical fiber connector according to claim 1, wherein the ferrule has a tapered portion whose diameter is increased from an inner diameter of the minute hole toward an inner diameter of the enlarged hole at an inlet end of the minute hole .   The optical fiber connector according to claim 1 or 2, wherein the ferrule has a V-groove substrate disposed at an entrance end of a microhole. The optical fiber connector according to any one of claims 1 to 3 , wherein the ferrule is made of zirconia. The optical fiber connector according to any one of claims 1 to 4 , wherein a length of the fine hole is 1 to 2 mm.   6. The optical fiber connector according to claim 1, wherein the optical fiber connector is an SC connector.   The light according to any one of claims 1 to 6, wherein either one or both of the first optical fiber and the second optical fiber is an intermediate optical fiber for MFD conversion. Fiber connector.

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