JP2005208113A - Mode field converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mode field converter capable of easily splicing, with a small loss, two optical fibers having a different mode field diameter. <P>SOLUTION: Two optical fibers 1, 2 having a different mode field diameter are fusion-spliced and the vicinity 4 of the fusion-spliced part is thermal diffusion-processed using a heat source such as a burner. A fusion heating part 5 is thickened by surface tension accompanying the melting of the fiber at the time of the fusion (a). The thickened portion of the fusion heating part 5 is heated and drawn (refer to the heating drawing part 6) using the heat source such as the burner, making the clad outer diameter in the vicinity 4 of the fusion spliced part not more than the inner diameter of a ferrule 7, and enabling the fusion spliced part to be inside a ferrule 7 (b). Reinforcement can be performed by storing the fusion spliced part inside the ferrule 7, and also the part can be incorporated in an optical connector component 8, two connector-attached optical fiber cords having two different mode field diameters are connected at both ends of the optical connector component (c). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a mode field converter for easily connecting two optical fibers having different mode field diameters with low loss.

  An erbium-doped fiber widely used as an optical amplifier in the 1550 nm communication wavelength band in optical communication, a dispersion-shifted optical fiber in which the wavelength dispersion characteristic of the optical fiber is changed, etc. have a mode field diameter that is larger than that of a normal single mode optical fiber. small.

  The mode field diameter of a normal single mode optical fiber is 9 to 10 μm, the mode field diameter of an erbium-doped fiber is 4 to 5 μm, and the mode field diameter of a dispersion shifted optical fiber is 7 to 8 μm. When such optical fibers having different mode field diameters are connected to each other, connection loss occurs. A conventional example for reducing this connection loss is shown below.

FIG. 6A is a diagram showing a first conventional example.
As shown in the figure, the optical fiber having the smaller mode field diameter is heated, and the core additive material (eg, germanium (Ge)) or the cladding additive material (eg, fluorine (F)) constituting the optical fiber is heated. By diffusing, the mode field diameter of the optical fiber is enlarged, the difference from the mode field diameter of the optical fiber on the other side is reduced, this part is fixed to a ferrule, and it is easily made with low loss by making it a connector Can be connected.

FIG. 6B is a diagram showing a second conventional example.
As shown in the figure, after fusion-bonding optical fibers having different mode field diameters, the vicinity of the connection part is heated, and the additive material of both optical fibers is diffused to match the mode field diameters. It is fixed to a ferrule and is made into a connector so that it can be easily connected with low loss.

  A conventional example of connecting two optical fibers having different core diameters is described in Japanese Patent No. 261913 (Patent Document 1). Here, after the core diameter is expanded by locally heating the intermediate portion of the optical fiber with the smaller core diameter in a temperature range where the additive material diffuses but the optical fiber does not melt, the expanded portion is subjected to stress fracture Both are connected to each other, and this makes it possible to connect single mode optical fibers having different core diameters with low loss without using a lens.

Japanese Patent No. 261913

However, the conventional method has the following problems.
In the first conventional example, since the mode field diameter after thermal diffusion is different at the cut position of the optical fiber, when fixed to the ferrule and polished, the probability that the end face matches the mode field diameter of the other side is sufficiently large. There was no yield.

  In the second conventional example, since the optical fiber having the same mode field diameter as the counterpart is used, the problem of the first conventional example can be solved. However, since the optical fiber is pushed in the direction of abutment during fusion. The clad outer diameter of the optical fiber after fusion is larger than that before fusion.

  For example, the outer diameter of the clad is 127 μm or more in the vicinity of the fused portion, and as a result, it cannot be inserted into the ferrule 7 having an inner diameter of 125 μm. Therefore, there is a problem that reliability is deteriorated because the fusion heating part 5 is positioned outside the ferrule 7.

  Further, as a method for solving this problem, among the optical fibers to be connected as shown in FIG. 5C, the cladding outer diameter of the other optical fiber to which the cladding outer diameter of one optical fiber is to be connected. By setting the optical fiber thinner by several μm, it is possible to prevent the clad outer diameter of the fusion splicing portion from being enlarged. However, the cladding diameter of the optical fiber that is normally used is manufactured to 125 ± 1 μm, and if an optical fiber having a small cladding outer diameter is to be used, a new manufacturing process is required, which increases the cost.

  Further, in the above conventional example, there is a problem that the loss is not sufficiently reduced when the multimode optical fiber and the single mode optical fiber are connected.

  An object of the present invention is to provide a mode field converter capable of easily connecting two optical fibers having different mode field diameters with low loss.

  The present invention employs the following configuration in order to achieve the above object. Hereinafter, the structure for each claim will be described.

  According to the first aspect of the present invention, in the mode field converter using the first optical fiber and the second optical fiber having different mode field diameters as input and output, the first optical fiber and the second optical fiber are fusion spliced. In addition, the additive material of the core or the clad is thermally diffused in the fusion spliced portion, and the connecting portion is stretched and thinned and fixed inside the ferrule.

  The invention according to claim 2 is a mode field converter in which a first optical fiber and a second optical fiber having different mode field diameters are used as input and output, and between the first optical fiber and the second optical fiber, A third optical fiber having a mode field diameter different from the mode field diameter of the first optical fiber and the second optical fiber is fusion-spliced, and the first optical fiber and the third optical fiber 3 are connected. The core or clad additive material is thermally diffused at each of the connecting portion between and the connecting portion between the third optical fiber 3 and the second optical fiber.

  According to a third aspect of the present invention, in the mode field converter of the second aspect, the connection between the first optical fiber and the third optical fiber 3 and the third optical fiber 3 and the second optical fiber are connected. It is characterized in that the connecting portion between them is stretched and thinned and fixed inside the ferrule.

  According to a fourth aspect of the present invention, in the mode field converter according to any one of the first to third aspects, both ends of the ferrule are polished so that the first optical fiber and the second optical fiber are thermally diffused. It is characterized in that the unexposed portions are located on the respective polished surfaces.

  The invention according to claim 5 is the mode field converter according to any one of claims 1 to 4, wherein one of the first optical fiber and the second optical fiber is a single mode optical fiber, and the other Is a single-mode optical fiber or a multi-mode optical fiber.

  According to a sixth aspect of the present invention, in the mode field converter according to any one of the second to fourth aspects, one of the first optical fiber and the second optical fiber is a single mode optical fiber, and the other Is a multimode optical fiber, and the third optical fiber is a single mode optical fiber smaller than the mode field diameter of either the first optical fiber or the second optical fiber.

  According to the present invention, conversion between a single mode optical fiber and a multimode optical fiber can be realized with low loss. The effects for each claim will be described below.

  According to the first aspect of the present invention, the mode field diameter at the connector end face matches the mode field diameter of the optical fiber to be connected, the connection is easy, and the connection can be made with low loss. Furthermore, the outer diameter of the clad of the fusion splicing portion can be reduced by stretching, and the inner diameter of the ferrule can be accommodated.

  According to invention of Claim 2, compared with the invention concerning Claim 1, the 3rd optical fiber fusion-spliced between the 1st and 2nd optical fibers is the 1st and 2nd. The difference in mode field diameter in the connection portion of the optical fiber is alleviated, and a connection with lower loss can be obtained.

  According to the third aspect of the present invention, mode field conversion with lower loss can be performed, and this can be a simple connector connection.

  According to the invention of claim 4, it is possible to produce a component capable of connecting an optical connector to both ends of a short optical fiber, and matches the mode field diameter of each optical fiber, Low loss connection can be realized easily.

  According to the fifth and sixth aspects of the invention, a low-loss connection can be realized by an easy operation between optical fibers having different mode field diameters.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a view for explaining a first embodiment of the present invention and relates to the invention described in claim 1.

  In this first embodiment, as shown in FIG. 1 (a), two optical fibers 1 and 2 having different mode field diameters are fusion-spliced, and the vicinity 4 of the fusion splice is used by using a heat source such as a burner. If only the thermal diffusion treatment is performed, the fusion heating part 5 remains thick due to the surface tension accompanying the melting of the fiber at the time of fusion.

  As shown in FIG. 1 (b), by heating and stretching the thickened portion of the fusion heating part 5 using a heat source such as a burner (see the heating and stretching part 6), the vicinity of the fusion splicing part 4 The outer diameter of the clad was made equal to or smaller than the inner diameter of the ferrule 7 so that the inner surface of the ferrule 7 was made possible.

  Reinforcement can be achieved by making the fusion splicing part in the ferrule 7, and as shown in FIG. 1 (c), two connector-attached optical fiber cords having two different mode field diameters are incorporated into the optical connector part 8. With a simple operation of connecting to both ends, a low-loss connection can be realized.

  FIG. 2 is a view for explaining a second embodiment of the present invention and relates to the invention described in claim 2.

  In the second embodiment, an optical fiber 3 having a mode field diameter different from the mode field diameter of these two optical fibers is fused between the optical fiber 1 and the optical fiber 2 having different mode field diameters to be connected. The mode field diameters are matched by thermal diffusion at each of the connection between the optical fiber 1 and the optical fiber 3 and the connection between the optical fiber 3 and the optical fiber 2.

  For example, in the case of a long wavelength of 1310 nm or 1550 nm used for a communication wavelength, a single mode optical fiber having a mode field diameter of 4.2 μm is applied to the optical fiber 1, and a single mode optical fiber having a mode field diameter of 10.4 μm is applied to the optical fiber 2. When the optical fiber 1 and the optical fiber 2 are fusion-spliced and the vicinity of the fusion splicing part is subjected to a thermal diffusion process using a heat source such as a burner, the connection loss is 0.23 dB (first embodiment; claim) 1).

  However, a single mode optical fiber having a mode field diameter of 7.1 μm is applied as the optical fiber 3, and the single mode optical fiber 1, the single mode optical fiber 3, and the single mode optical fiber 2 are configured according to the second embodiment. When connected, the connection loss is 0.11 dB, and the connection can be further reduced.

  FIG. 3 is a view for explaining a third embodiment of the present invention, and relates to the invention described in claim 3.

  In the second embodiment, as shown in FIG. 3, the fusion heating part 5 between the optical fiber 1 and the optical fiber 3 and the fusion heating part 5 between the optical fiber 3 and the optical fiber 2 are provided with ferrules. Heat-stretched (see the heat-stretching portion 6) so as to be thinner than the hole diameter. Thereby, an optical connector can be formed, and the low-loss connection of the second embodiment can be realized by an easy operation.

  FIG. 4 is a view for explaining a fourth embodiment of the present invention, and relates to the invention described in claim 4.

  In this embodiment, as shown in the figure, a ferrule 7 whose both ends are polished is housed in an optical connector member 8 constituted by a housing, a plug frame or the like. In this way, if two connectors having different mode field diameters to be optically connected are connected from both ends, a low-loss connection can be easily realized with small components.

  FIG. 5 is a diagram showing the effect of the present invention, and relates to the invention described in claims 5 and 6.

  This figure shows the effect when a single mode optical fiber having a mode field diameter of 10.4 μm is applied to the optical fiber 1 and a multimode optical fiber having a mode field diameter of 44 μm is applied to the optical fiber 2. FIG. (B) shows the state of claim 1, (c) shows a single mode optical fiber having a length of 10 mm and a mode field diameter of 7.1 μm as the optical fiber 3. 3 shows the effect in the case of the connection loss when the single mode optical fiber 1, the single mode optical fiber 3, and the multimode optical fiber 2 are connected as shown in FIG.

  From FIG. 5, (b) connected as in claim 1 rather than (a) simply connected by connector, and (c) connected as in claim 6 from (b) connected as in claim 1. ) Shows that the connection loss is lower. Further, a small component can be realized by combination with claim 4.

It is a figure for demonstrating the 1st Example of this invention. It is a figure for demonstrating the 2nd Example of this invention. It is a figure for demonstrating the 3rd Example of this invention. It is a figure for demonstrating the 4th Example of this invention. It is a figure which shows the effect of this invention. It is a figure which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical fiber which has mode field diameter 1 2 ... Optical fiber which has mode field diameter 2 3 ... Optical fiber which has mode field diameter 3 4 ... Fusion splicing part vicinity 5 ... Fusion heating part 6 ... Heat extending | stretching part 7 ... Ferrule 8 ... Optical connector member 9 ... Mode field diameter enlarged portion 10 ... Optical fiber having a mode field diameter 2 and a smaller cladding outer diameter than the optical fiber having the mode field diameter 1

Claims (6)

In a mode field converter having a first optical fiber and a second optical fiber having different mode field diameters as input and output,
The first optical fiber and the second optical fiber are fusion-spliced, and a core or cladding additive material is thermally diffused in the fusion-spliced portion, and the connection portion is drawn and reduced in diameter. A mode field converter characterized by being fixed inside. In a mode field converter having a first optical fiber and a second optical fiber having different mode field diameters as input and output,
A third optical fiber having a mode field diameter different from the mode field diameter of the first optical fiber and the second optical fiber is fused between the first optical fiber and the second optical fiber. A core or a clad of each of the connecting portion between the first optical fiber and the third optical fiber 3 and the connecting portion between the third optical fiber 3 and the second optical fiber. A mode field converter characterized in that the additive substance is thermally diffused. The mode field converter of claim 2,
The connecting portion between the first optical fiber and the third optical fiber 3 and the connecting portion between the third optical fiber 3 and the second optical fiber are stretched and thinned and fixed inside the ferrule. A mode field converter characterized in that The mode field converter according to any one of claims 1 to 3,
A mode field converter characterized in that both ends of the ferrule are polished and portions of the first optical fiber and the second optical fiber that are not thermally diffused are located on the respective polished surfaces. The mode field converter according to any one of claims 1 to 4,
One of the first optical fiber and the second optical fiber is a single mode optical fiber, and the other is a single mode optical fiber or a multimode optical fiber. The mode field converter according to any one of claims 2 to 4,
One of the first optical fiber and the second optical fiber is a single mode optical fiber, the other is a multimode optical fiber, and the third optical fiber is the first optical fiber and the first optical fiber. A mode field converter characterized by being a single mode optical fiber smaller than any mode field diameter of the two optical fibers.

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