JP2004252368A - Optical fiber connecting member and optical fiber connecting device and optical fiber connecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber connecting member which can suppress the connection loss due to difference in MFDs (mode field diameters) not completely but to some extent when connecting the optical fibers different in the MFDs from each other and which has excellent working property on site and an optical fiber connecting device and an optical fiber connecting method. <P>SOLUTION: The optical fiber connecting member 26 used for connection of the optical fibers 20 and 22 different in the MFDs from each other is equipped with a single and short-length built-in optical fiber 21 having an MFD which is the intermediate of the MFDs of both optical fibers. A front end side 29 of the optical fiber 21 is formed of a connecting end surface to be butt connected separably to one of the optical fibers and a rear end side 30 thereof is formed of a juncture 28 to be mechanically splice-connected to the other of the optical fibers. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical fiber connecting member, an optical fiber connecting device, and a connecting method for connecting optical fibers having different mode field diameters.
[0002]
[Prior art]
In optical communications using optical fibers, the introduction of WDM (wavelength multiplexing) optical transmission has been progressing with the increase in the amount of information and the number of communication lines, and DWDM optical transmission that performs multiplexing at high density to enable large capacity transmission. The introduction of is also being considered. For this reason, small diameter bending is required for the optical fiber of the optical cable used for the optical wiring in the optical communication device in order to increase the storage density. In addition, as the number of communication lines increases, a large number of optical fibers become congested.Therefore, it is necessary to use an optical fiber that can be handled easily from a wiring rack to a cabinet, and in particular, that can suppress an increase in loss in handling in a live state. ing.
[0003]
As an optical fiber that can meet such demands, an optical fiber that is resistant to bending and that can suppress bending loss to 1.0 dB or less even when bent at a bending radius of about 15 mm has been developed. However, since such an optical fiber has a small mode field diameter, when it is connected to a normal single mode optical fiber, a loss increases due to a difference in the mode field diameter.
[0004]
Conventionally, when optical fibers having different mode field diameters (hereinafter referred to as MFDs) are connected to each other, an increase in loss is suppressed by interposing an intermediate fiber having an intermediate value of the MFD of both optical fibers. Is known (for example, see Patent Document 1). FIG. 8 is a diagram showing the technique disclosed in Patent Document 1, wherein C is an optical fiber cable, P is an optical waveguide, 1 and 2 are optical fibers, 1a and 2a are core portions, 1b and 2b are clad portions. Reference numeral 3 denotes a reinforcing tube (or ferrule), 4 denotes an adhesive, 5, 6, and 7 denote intermediate optical fibers, and 5a, 6a, and 7a denote core portions.
[0005]
FIG. 8 shows a case where the optical fiber cable C and the optical waveguide P having different MFDs are connected to each other, and the optical fiber cable C has its distal end portion removed to expose the internal optical fiber 1. The optical fiber 1 includes a core 1a and a clad 1b, and the MFD of the core 1a is, for example, 10 μm. The optical fiber 2 on the optical waveguide P side includes a core 2a and a clad 2b, and the MFD of the core 2a is, for example, 5 μm.
[0006]
The difference between the MFDs of the optical fibers 1 and 2 is 5 μm, and when directly connected, the connection loss is 1.94 dB in theory. This connection loss increases as the difference between the MFDs increases. In FIG. 8, intermediate optical fibers 5, 6, 7 having an MFD having an intermediate value of the MFD of the optical fibers 1 and 2 are interposed between the optical fibers 1 and 2, and the optical fibers 1 The MFD is made closer to the MFD of the optical fiber 2.
[0007]
The intermediate optical fibers 5, 6, and 7 have, for example, the same outer diameter as that of the optical fiber 1 and the core portions 5a, 6a, and 7a have MFDs of 8 μm, 7 μm, and 6 μm. As a connection procedure, first, the intermediate optical fiber 5 is spliced at the end of the optical fiber 1, cut off leaving about 10 mm, and the intermediate optical fiber 6 is spliced at that portion. Similarly, the intermediate optical fiber 7 is spliced to the intermediate optical fiber 6. A reinforcing tube 3 made of stainless steel, ceramic, or the like is attached to the surfaces of the optical fiber 1 and the intermediate optical fibers 5, 6, and 7 with an adhesive 4, thereby maintaining the strength of the optical fiber.
[0008]
With the above configuration, the connection loss between the optical fiber 1 and the intermediate optical fiber 5 is 0.21 dB, the connection loss between the intermediate optical fibers 5 and 6 is 0.08 dB, and the connection between the intermediate optical fibers 6 and 7 is The loss is 0.10 dB, and between the intermediate optical fiber 7 and the optical fiber 2 is 0.14 dB. The total connection loss is 0.53 dB, and the connection loss based on the difference in the MFD can be significantly reduced as compared with the connection loss of 1.94 dB when the optical fiber 1 and the optical fiber 2 are directly connected.
[0009]
FIG. 9 shows a case where optical fibers having different MFDs are directly connected to each other by a mechanical splice, and the optical fiber having a smaller MFD is enlarged by heating to abut the optical fiber having a larger MFD. FIG. 8 is a diagram showing an example (for example, refer to Patent Document 2). In the figure, 11 and 12 are optical fibers, 11a and 12a are core portions, 11b and 12b are clad portions, 11c is an MFD enlarged portion, 13 is a fiber coating, 14 is a ferrule, and 15 is a split sleeve.
[0010]
In FIG. 9, the MFD of the core portion 11a at the connection end portion of the optical fiber 11 having the smaller MFD (expressed as the core diameter in Patent Document 2) is locally heated with a burner or the like to remove the dopant of the core portion 11a. The heat is diffused toward the clad portion 11b. Due to this heat diffusion, the MFD of the connection end of the optical fiber 11 is partially enlarged so as to be close to the MFD of the core portion 12a of the other optical fiber 12 (Thermally-diffused Expanded Core, hereinafter referred to as TEC). it can.
[0011]
As the TEC method, the fiber coating 13 in the middle of the optical fiber 11 having the smaller MFD is removed, and the optical fiber 11 itself does not melt, but the temperature of the optical fiber 11 is reduced at a temperature at which the dopant of the core 11a diffuses toward the cladding 11b. And heat. The central portion of the MFD enlarged portion 11c where the MFD is enlarged is cut by stress rupture to form a connection end surface. The connection ends of the optical fiber 11 and the optical fiber 12 are housed in a ferrule 14 and bonded and integrated, and then mechanically spliced using a split sleeve 15 or the like.
[0012]
As described above, by butt-connecting optical fibers having different MFDs, it is possible to reduce the difference in the MFD at the butt end and suppress an increase in connection loss. It is also known that by increasing the MFD at the connection end, it is possible to reduce an increase in loss due to shaft deviation during connection.
[0013]
[Patent Document 1]
JP-A-6-43332
[Patent Document 2]
Japanese Patent No. 2619130
[0014]
[Problems to be solved by the invention]
In general, the wiring of the optical cable in the apparatus or the premises is often performed using an optical connector. In particular, when the wiring length cannot be specified before construction, an optical connector may be attached after laying an optical cable on site.
[0015]
When the MFDs of the optical cables connected to each other are different, as shown in FIG. 8 described above, the difference between the MFDs can be reduced stepwise by connecting the intermediate optical fiber to a plurality of optical fibers having an intermediate MFD between the two optical cables. . However, if a plurality of optical fibers are sequentially connected and the MFD is adjusted stepwise, the entire length of the intermediate optical fiber becomes longer, and the axial length of the optical connector becomes longer. Further, since it is necessary to sequentially connect and configure short optical fibers by fusion, the manufacturing cost increases, which is not practical. Especially at the local work site, the MFD of the other optical cable used for the existing equipment may be known for the first time at the start of construction, and there may be no point in finding a high-precision MFD for the intermediate optical fiber in advance. is there.
[0016]
As shown in FIG. 9, it is useful to expand the MFD by performing TEC processing on the connection end side of the optical cable having the smaller MFD of the optical cables connected to each other to suppress an increase in loss due to the difference in the MFD of the optical cable. However, there is a problem in terms of working and cost in connecting the connection end of the optical cable by TEC processing, and in particular, performing TEC processing or polishing the end face of an optical fiber on site is not good in workability. I can not say it and it is not efficient. As an optical connector for on-site assembly, a short optical fiber is built in advance, and one end of this built-in optical fiber is polished with a ferrule so that a low-loss connection can be obtained by mating with the optical connector on the other side. Some are configured in The other end of the built-in optical fiber is connected to the optical cable by fusion or mechanical splice.
[0017]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and in order to locally connect optical fibers having different MFDs to an optical connector, connection loss due to a difference in the MFD can be suppressed to some extent, but not completely. An object of the present invention is to provide an optical fiber connecting member and an optical fiber connecting method which are excellent in performance.
[0018]
[Means for Solving the Problems]
The optical fiber connecting member according to the present invention is an optical fiber connecting member used to connect optical fibers having different mode field diameters, and has a single short length having a mode field diameter intermediate between the mode field diameters of both optical fibers. The optical fiber has a built-in optical fiber, the front end portion is formed with a connection end surface that is separably butt-connected to one of the optical fibers, and the rear end portion is formed with a connection portion that is mechanically spliced with the other optical fiber. Things. In addition, the built-in optical fiber can be a short built-in optical fiber having a mode field diameter at both ends that matches or approximates the mode field diameter of both optical fibers.
[0019]
An optical fiber connection device according to the present invention is an optical fiber connection device for connecting optical fibers having different mode field diameters to each other with an optical connector, wherein the optical connector has a mode field diameter intermediate between the mode field diameters of both optical fibers. It has a single short built-in optical fiber that has a connecting end face that can be connected to one end of the optical fiber in a separable manner at the front end, and a mechanical splice that connects and fixes the other end of the optical fiber at the rear end. One of the optical fibers is connected to the distal end of the optical connector via another optical connector, and the other of the optical fibers is mechanically spliced to the rear of the optical connector. In addition, the built-in optical fiber can be a short built-in optical fiber having a mode field diameter at both ends that matches or approximates the mode field diameter of both optical fibers.
[0020]
The optical fiber connection method according to the present invention is an optical fiber connection method for connecting optical fibers having different mode field diameters to each other with an optical connector, and the optical connector has an intermediate mode field diameter between the mode field diameters of both optical fibers. Holds a single, short built-in optical fiber that has the front end of the optical connector with a connection end face that is separably butt-connected to one of the optical fibers, and the rear end is connected and fixed to the other of the optical fibers. Formed by a mechanical splice, one end of the optical fiber is connected to the front end of the optical connector via another optical connector, and the other end of the optical fiber is connected to the rear end of the optical connector by a mechanical splice. It is. In addition, the built-in optical fiber can be a short built-in optical fiber having a mode field diameter at both ends that matches or approximates the mode field diameter of both optical fibers.
[0021]
Another optical fiber connection method according to the present invention is an optical fiber connection method for connecting optical fibers having different mode field diameters to each other with an optical connector. It has a connection end face that is separably butt-connected to one of the optical fibers, and a mechanical splice that is connected and fixed to the other end of the optical fiber on the rear end side. Prepare an optical connector, select the type of optical connector that minimizes the loss according to the mode field diameter of both optical fibers connected to each other, and connect one end of the optical fiber to the other end of the optical connector. The optical fiber is connected via a connector, and the other end of the optical fiber is mechanically spliced to the rear end of the optical connector.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. 1 (A) and 1 (B) are diagrams illustrating a connection form of an optical cable, FIG. 2 (A) is a diagram illustrating a connection member used for an optical connector for on-site assembly, and FIG. 2 (B) is a factory-installed optical connector. It is a figure which shows the connection member of. In the figure, 20 and 22 are optical fibers, 21 is a built-in optical fiber, 23 is an optical connector for on-site assembly, 24 is a connection adapter, 25 is a factory shipping optical connector, 26 is a connection member, 27 is a ferrule, 28 is a mechanical splice, 29 is a front end, 30 is a rear end, 31 is a ferrule holder, and C1 and C2 are optical cables.
[0023]
In the example shown in FIG. 1A, the on-site optical connector 23 is attached to the optical cable C1, the factory shipping optical connector 25 is attached to the optical cable C2, and the on-site assembly optical connector 23 and the factory shipping optical connector 25 are connected, for example. A mode in which they are detachably interconnected via a connection adapter 24 is shown. The optical cable C1 contains, for example, an optical fiber 20 having an MFD of 9.2 μm, and the optical cable C2 contains, for example, an optical fiber 22 having an MFD of 6.3 μm.
[0024]
As shown in FIG. 2A, the on-site assembling optical connector 23 is one that is assembled using a connecting member 26 containing the built-in optical fiber 21 and is connected to the optical cable C1 on site. The factory-shipped optical connector 25 is a state in which the optical fiber 22 of the optical cable C2 is directly inserted into the connecting member 26a as shown in FIG. 2B, and is previously assembled to the optical cable C2 in the manufacturing factory. Shall say.
[0025]
As shown in FIG. 2A, the connection member 26 includes a ferrule 27 and a ferrule holder 31, and is configured by storing and fixing the short built-in optical fiber 21 in advance therein. The front end 29 is formed of a polished connection end face that is butt-connected to a mating connector, and the rear end 30 is formed of a connection portion that is connected to the optical fiber 20 in the optical cable C1 by fusion or mechanical splice. . At the local installation site, after connecting the optical cable C1 to the connection member 26, a connector housing and a boot (detailed description is omitted) are attached to the connection member 26 to form the on-site assembly optical connector 23.
[0026]
The factory-shipped optical connector 25 has the same configuration as the on-site optical connector 23, but as shown in FIG. 2B, the end of the optical fiber 22 in the optical cable C2 is directly inserted into the connecting member 26a. In a state where the cable C2 is attached in advance, the cable C2 is prepared at a local installation site. Therefore, there is no work for assembling the optical connector on site, and it is only necessary to arrange the optical connector for connection to the connection adapter 24. In other words, it can be said that an already installed optical connector may be used.
[0027]
FIG. 1B is a diagram illustrating an example in which the on-site optical connectors 23 are attached to both the optical cable C1 and the optical cable C2 and connected to each other. Therefore, as the optical cable C1 and the optical cable C2, those locally procured can be used. Then, an on-site assembling optical connector 23 accommodating the built-in optical fiber 21 suitable for connection with the optical fibers 20 and 22 of each optical cable is prepared. These on-site optical connectors 23 may be the same for the optical cable C1 and the optical cable C2, but may be different. The connection between the on-site assembling optical connectors 23 attached on site is removably interconnected via a connection adapter 24 as in FIG. 1A.
[0028]
When connecting the built-in optical fiber 21 and the optical fiber 20 in the on-site assembly optical connector 23, the connection loss can be minimized by fusion splicing. It takes time and effort. For this reason, as a form that can be easily connected on site, a ferrule with a mechanical splice that has been easily assembled has recently been developed, and its connection accuracy has been improved and low loss has been realized. Have been. FIG. 2A shows an example in which a mechanical splice 28 is provided at the rear part of the ferrule 27. In the present invention, however, a configuration intended for a mechanical splice connection which is easy to assemble on site and has excellent workability. And
[0029]
The same type of optical fiber as the optical fiber 20 connected to the rear end is usually used as the built-in optical fiber 21 of the optical connector 23 for on-site assembly. However, if the MFDs of the optical cables C1 and C2 connected via the optical connector are different as described above, the connection loss due to the MFD difference increases. Therefore, in the present invention, a single short optical fiber having an MFD intermediate between the MFD of the optical cable C1 and the MFD of the optical cable C2 is used as the optical fiber 21 built in the ferrule 27 of the optical connector 23 for on-site assembly.
[0030]
FIG. 4 is a diagram illustrating a relationship between a connection loss (hereinafter, referred to as a mismatch loss) caused by a difference in MFD and a difference in MFD when connecting optical fibers having different MFDs. FIG. 4 shows the mismatch loss when the MFD of one optical fiber L is 9.2 μm and the MFD of the optical fiber S connected thereto is changed. According to this drawing, the MFD of the connection optical fiber S is 0.2 dB when the MFD is 7.4 μm, 0.6 dB when the MFD is 6.3 μm, and 1.0 dB when the MFD is 5.65 μm.
[0031]
FIG. 5 shows the total mismatch loss and the intermediate optical power at two locations on both sides of the intermediate optical fiber M when the intermediate optical fiber M is connected between two optical fibers L and S having different MFDs. FIG. 3 is a diagram illustrating a relationship between a fiber M and an MFD. FIG. 5A shows a case where the right optical fiber L has a MFD of 9.2 μm and the left optical fiber S has a MFD of 6.3 μm. FIG. 5B shows a case where the right optical fiber L has a MFD of 9.2 μm and the left optical fiber S has a MFD of 7.5 μm.
[0032]
As shown in FIG. 4, for example, when the optical fiber L having an MFD of 9.2 μm and the optical fiber S having an MFD of 6.3 μm are directly connected, a mismatch loss of 0.6 dB occurs at the connection portion. As shown in (A), by connecting an intermediate optical fiber M having an MFD in the range of 6.8 μm to 8.5 μm, for example, between the two optical fibers L and S, the number of connection points increases to two. However, the total mismatch loss at the two locations can be 0.4 dB or less.
[0033]
As shown in FIG. 4, when the optical fiber L having an MFD of 9.2 μm and the optical fiber S having an MFD of 7.5 μm are directly connected, a mismatch loss of 0.18 dB occurs at the connection portion. As shown in (B), by connecting an intermediate optical fiber M having an MFD in the range of 8.0 μm to 8.7 μm between the two optical fibers L and S, the number of connection points increases to two. However, the total mismatch loss at the two locations can be 0.12 dB or less.
[0034]
As described above, a single intermediate optical fiber M having an MFD value intermediate between the MFD values of the optical fibers L and S is interposed in the connection between the optical fiber L and the optical fiber S having different MFDs. And it is possible to connect different kinds of optical fibers at about 0.5 dB. In addition, the intermediate optical fiber M and one of the optical fibers L are mechanically spliced by a well-known mechanism for releasing / executing a clamp by, for example, inserting / removing a wedge member from the outside, so that a connection operation on site can be performed. Can be easier.
[0035]
In FIG. 2A, the intermediate optical fiber M shown in FIG. 5 is the built-in optical fiber 21 housed and fixed in the ferrule 27 of the connection member 26 of the on-site assembly optical connector 23. If one optical fiber L is an optical fiber 20 that is mechanically spliced with the built-in optical fiber 21, the other optical fiber S is a ferrule 27 of a connecting member 26a of a factory-shipped optical connector 25 that is the other optical connector. Can be made to correspond to the optical fiber 22 housed and fixed in the optical fiber. The optical fiber L side in FIG. 5 may be used as the optical fiber 22 and the optical fiber S side may be used as the optical fiber 20. If the combination of the optical fibers to be connected is determined, it can be used for attaching an optical connector to any optical fiber. Therefore, convenience in construction can be improved.
[0036]
Further, as shown in FIG. 1B, when the on-site optical connector 23 is used for both the optical cables C1 and C2 connected to each other, when connecting the optical cables C1 and C2 having different MFDs, both of them are used. An intermediate optical fiber M having an intermediate MFD may be used for one of the built-in optical fibers 21 of the on-site optical connector 23. However, a similar result can be obtained even when the same intermediate optical fiber M is housed and used in both the optical connectors 23 for field assembly. In this case, two intermediate optical fibers M are connected in series, but the effect of reducing the mismatch loss is the same as described above. By using the connection member 26 containing the same intermediate optical fiber M as the on-site assembling optical connector 23 and sharing it with both the optical cables C1 and C2, it is possible to reduce the types of parts to be prepared in advance.
[0037]
However, as the built-in optical fiber 21 of the on-site assembly optical connector 23, an optical fiber having different MFDs for the optical cable C1 and the optical cable C2 may be used. In this case, the different MFDs of the built-in optical fiber 21 are both at an intermediate value between the MFDs of the optical cables C1 and C2, and the optical connectors 23 for on-site assembly are combined so that the difference between the MFDs of the optical cables C1 and C2 is reduced. . For example, when the MFD on the optical cable C1 side is 9.2 μm and the MFD on the optical cable C2 side is 6.3 μm, the built-in optical fiber 21 of the on-site assembly optical connector 23 connected to the optical cable C1 is 8.0 μm, and the optical cable C2 The built-in optical fiber 21 of the on-site assembly optical connector 23 connected to is set to 7.0 μm. Thereby, the mismatch loss can be further reduced.
[0038]
In the above configuration, for example, a normal single mode optical fiber having an MFD of about 9.2 μm is used for the optical cable C1. As the cable C2, an optical fiber having a characteristic that it can be bent with a small diameter and the wiring in the device can be made compact, or a loss fluctuation at the time of handling in a congested state or an access system is small.
[0039]
For the latter optical fiber, for example, the MFD defined by Petermann-I at a wavelength of 1.55 μm is 8 μm or less, and the absolute value of the chromatic dispersion at both 1.3 μm and 1.55 μm is 12 ps. An optical fiber having an MFD of not more than / nm / km, a cable cutoff wavelength of not more than 1.26 μm, and an MFD of not less than 6 μm as defined by Peterman-I at a wavelength of 1.3 μm has recently been developed. An optical fiber cable using this optical fiber core wire does not cause a loss increase of 1.0 dB or more even when bent at a bending radius of about 15 mm, so that the wiring operation can be performed with ease and ease.
[0040]
The connection member 26 is in a state where assembly in a necessary range has been completed in the factory in advance, and connection work without bonding and polishing can be performed on site. The connecting member 26 is provided with a mechanical splice 28, and the short built-in optical fiber 21 having an MFD intermediate between the MFD values of the optical cable C 1 (optical fiber 20) and the optical cable C 2 (optical fiber 22) is stored and fixed in the ferrule 27. The tip portion 29 is prepared by polishing the end surface.
[0041]
In addition, since the type of the optical cable used on site is not clear and its MFD cannot be specified in some cases, a connection member containing a built-in optical fiber having several types of MFDs may be prepared in advance within the expected range. Good. Preferably, each connection member is identified for each type of built-in optical fiber or for each type of optical fiber to be connected. These can be identified by marking and color-coding the housing, boots, and the like.
[0042]
3A and 3B show a second embodiment according to the present invention. FIG. 3A shows a connection member for on-site assembly, and FIGS. 3B and 3C show an example of manufacturing a built-in optical fiber. FIG. In the figure, 32 and 33 are optical fibers, 32a and 33a are core portions, 32b and 33b are clad portions, 34 is an MFD enlarged portion, 35 is a fusion spliced end, and 21'a and 21'b are ends of a built-in optical fiber. Indicates a part. The reference numerals in the other drawings are used by adding “′” to the reference numerals used in FIG. 1 and FIG.
[0043]
The embodiment shown in FIG. 3 is different from the embodiments of FIGS. 1 and 2 in that the built-in optical fiber 21 'uses an optical fiber subjected to TEC processing, but the optical fiber 20' and the optical fiber 22 'having different MFDs. And is common in that mismatch loss due to a difference in MFD is reduced.
[0044]
It is a known technique to reduce the loss by connecting the optical fibers having different MFDs to expand the MFD of the optical fiber having the smaller MFD by heating to reduce the loss, as described in Japanese Patent Application Laid-Open No. H11-163,873. However, this TEC processing requires a long working time and requires skill, especially at a site where the working environment is not constant, so that it is difficult to obtain a connection of constant quality.
[0045]
The connection member 26 'shown in FIG. 3A includes a ferrule 27' and a mechanical splice 28 ', as in the case shown in FIG. It is composed. The front end portion 29 'is formed by a polished connection end surface for butt connection with a mating connector, and the rear end portion 30' is formed by a connection portion for mechanical splice connection with the optical fiber 20 'in the optical cable C1. At the local installation site, after the optical cable C1 is connected to the connection member 26 ', a connector housing and a boot (not shown) are attached to form the on-site optical connector 23 shown in FIG.
[0046]
In the example shown in FIG. 3 (B), the built-in optical fiber 21 ′ is an optical fiber having a smaller MFD (for example, 20 ′) among optical fibers 20 ′ and 22 ′ having different MFDs to be connected to each other. An optical fiber 32 having an MFD close to (or the same as) is used. The optical fiber 32 includes a core portion 32a and a clad portion 32b, and the MFD enlarged portion 34 does not melt the optical fiber itself, as described with reference to FIG. The intermediate portion of the optical fiber 32 is partially heated at a temperature at which the optical fiber 32 diffuses.
[0047]
The central portion of the MFD enlarged portion 34 is cut by stress rupture to match the tip portion 29 'as one end portion 21'a, and is stored and fixed in the ferrule 27', and then the end surface is polished to form a connection end surface. The other end 21'b of the built-in optical fiber 21 'is placed in a mechanical splice 28' integrally provided at the rear of the ferrule 27 '.
[0048]
In the example shown in FIG. 3 (C), the built-in optical fiber 21 'is an optical fiber 32 having an MFD close to (or the same as) each of the optical fibers 20' and 22 'to be connected to each other. 33 are used. The optical fibers 32 and 33 are composed of core portions 32a and 33a and cladding portions 32b and 33b, respectively, and are fusion-bonded with their fusion-spliced ends 35 being aligned. After the fusion splicing, the fusion spliced portion is subjected to TEC heating in the same manner as in FIG. Both sides of the MFD enlarged portion 34 are cut to a desired length by stress rupture, and different ends 21'a and 21'b of the MFD are formed at both ends.
[0049]
As described above, the built-in optical fiber 21 ′ that has been subjected to the TEC processing is stored and fixed in the ferrule 27 ′, and the connection member 26 ′ whose end surface is polished is manufactured in a factory. At the site, the optical fiber 20 'prepared on site is mechanically spliced to the end 21'b of the built-in optical fiber 21' in the connecting member 26 'without TEC, no polishing, and no bonding.
[0050]
As the optical fiber 20 ′ prepared locally, for example, an optical fiber having a small MFD, strong resistance to small-diameter bending, and small loss increase can be used. As the optical fiber 22 'butt-connected to the tip portion 29', a normal single mode optical fiber having an MFD of about 9.0 μm can be used. As the built-in optical fiber 21 ', an optical fiber having the same MFD as the optical fiber having the smaller MFD may be used. For example, an optical fiber that is resistant to the above-described small-diameter bending and has a small loss increase is used, and the distal end portion 29 'is enlarged to an MFD having a value close to the MFD of the optical fiber 22'.
[0051]
As shown in FIG. 3A, the end 21a 'of the built-in optical fiber 21' with the MFD enlarged is not the front end 29 'of the connecting member 26' but the opposite rear end 30 '. You may do so. In this case, a normal single mode optical fiber having an MFD of about 9.0 μm is connected to the optical fiber 20 ′ by a mechanical splice. Then, an optical fiber having a small MFD, strong against small-diameter bending, and small loss increase may be used on the optical fiber 22 'side.
[0052]
In the above-described configuration of FIG. 3 as well, the connection member 26 ′ containing the short-length built-in optical fiber 21 ′ that has been subjected to the TEC processing is manufactured in advance at a factory, and this is assembled as an optical connector on-site. However, it is possible to reduce the mismatch loss between the optical fibers different from each other and to facilitate the connection work in the field. Note that the MFDs at both ends of the built-in optical fiber 21 'do not need to completely match the MFDs of the optical fibers to be connected. That is, the mismatch loss due to the difference between the MFDs shown in FIGS. 4 and 5 is set within a range allowed in the transmission path, and therefore, there may be a difference within this range.
[0053]
FIG. 6 is a diagram for explaining a flow of selecting an optical connector type to be used based on MFD information of an optical cable connected on site and performing optical fiber connection with a predetermined loss or less. First, in step S1, MFD information of the optical cables C1 and C2 to be connected is obtained and used as input information. If there is a difference between the MFDs of the optical fibers to be connected, an allowable mismatch loss due to the difference is set as input information.
[0054]
On the basis of the above input information, in step S2, a data table (for example, data relating to the MFD difference and the mismatch loss as shown in FIGS. 4 and 5) is accessed, and the MFD is connected between different optical fibers. The allowable MFD range of the intermediate optical fiber is calculated. At this time, the optimum MFD and the upper and lower limits may be obtained. When the MFD of the intermediate optical fiber is calculated, in step S3, the stock data of the optical connector is accessed, and whether or not an available optical connector is stocked is checked and selected.
[0055]
In the optical connector inventory data, optical connector types, their MFDs, quantities, and the like are registered and managed. Therefore, from the stock data, in addition to the optical connector 23 for on-site assembly shown in FIGS. 1 to 3, various optical connectors can be included if they can be connected. In the access in step S3, an on-site assembly optical connector having a built-in optical fiber having an optimum MFD is selected from the intermediate MFD calculated in step S2. In addition, the type of the optical connector, such as the shape and size, and the quantity thereof are also collated. In addition, it is preferable that the data table is re-accessed based on the MFD of the optical connector selected and checked to check for a mismatch loss.
[0056]
In step S3, if available optical connectors are stocked, a predetermined amount is arranged on site, and in step 4, optical fibers necessary for laying optical cables are attached and connected. If no usable optical connectors are stocked or the quantity is insufficient in step S3, an instruction such as additional manufacturing is issued in step S5.
[0057]
As described above, in FIGS. 1 to 3, the case where single-core optical fibers having different MFDs are connected to each other has been described. However, with respect to multi-core optical fibers having different MFDs (for example, optical fiber tape or optical multi-core cable). Can also be applied.
[0058]
FIG. 7 is a diagram showing an example of attaching a multi-core optical connector for on-site assembly to a multi-core optical tape cable. 7A is a partially cutaway perspective view, and FIG. 7B is an axial sectional view. In the figure, 36 is an optical fiber, 37 is a built-in optical fiber, 38 is a multi-core connection member, 39 is a multi-core ferrule, 40 is a cavity, 41 is a fiber groove, 42 is a fitting pin insertion hole, 43 is a holding member, 44 Denotes a fixing member, and C3 denotes an optical tape cable.
[0059]
In FIG. 7, only one optical tape cable C3 having a different MFD and the multi-core connecting member 38 connected to the optical fiber 36 are shown. However, as shown in FIG. There is a multi-core connection member (optical connector). The multi-core connecting member 38 accommodates and fixes a plurality of built-in optical fibers 37 in a fiber groove 41 formed in a multi-core ferrule 39, and is assembled as an optical connector for on-site assembly.
[0060]
The built-in optical fiber 37 used here may be a single short optical fiber having an MFD intermediate between the MFDs of both optical fibers, or the MFD of both optical fibers, as described with reference to FIGS. A short optical fiber having MFDs at both ends that match or approximate to the above is used. The multi-core ferrule 39 is provided with fitting pin insertion holes 42 for aligning the position of the connector connection on both sides, and a cavity 40 at the center.
[0061]
The connection between the optical tape cable C3 and the connecting member 38 is such that the optical fiber 36 of the optical tape cable C3 is inserted into the cavity 40 of the multi-core ferrule 39 from the rear port, and butted against the rear end of the built-in optical fiber 37. A mechanical splice connection is used in which the holding member 43 is inserted from above the cavity 40 and clamped using the fixing member 44. The fixing member 44 has a shape for elastically holding the holding member 43, for example, a shape having a U-shaped cross section, and can be used by simply fitting it onto the multi-core ferrule 39. .
[0062]
【The invention's effect】
As described above, according to the present invention, when connecting optical fibers having different MFDs, it is possible to reduce the connection loss caused by the difference in the MFD, and to provide an optical fiber connection excellent in workability in on-site assembly. Can be formed.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a connection form of an optical cable according to the present invention.
FIG. 2 is a diagram illustrating a first embodiment of the present invention.
FIG. 3 is a diagram illustrating a second embodiment of the present invention.
FIG. 4 is a diagram showing a relationship between a difference in MFD and a mismatch loss.
FIG. 5 is a diagram showing a relationship of a mismatch loss when an intermediate optical fiber is interposed.
FIG. 6 is a diagram illustrating a flow of selecting an optical connector according to the present invention.
FIG. 7 is a view showing an example of a multi-core optical connector for on-site assembly.
FIG. 8 is a diagram illustrating a conventional technique.
FIG. 9 is a diagram illustrating another conventional technique.
[Explanation of symbols]
20, 20 ', 22, 22' ... optical fiber, 21, 21 '... built-in optical fiber, 21'a, 21'b ... end of built-in optical fiber, 23 ... field-installed optical connector, 24 ... connection adapter, 25: factory shipping optical connector, 26, 26 ': connecting member, 27, 27': ferrule, 28, 28 ': mechanical splice, 29, 29': front end, 30, 30 ': rear end, 31: ferrule Holders, 32 and 33 are optical fibers, 32a and 33a are core portions, 32b and 33b are clad portions, 34 is an MFD enlarged portion, 35 is a fusion spliced end, 36 ... optical fiber, 37 ... built-in optical fiber, 38 ... Multi-core optical connector for on-site assembly, 39: multi-core ferrule, 40: cavity, 41: fiber groove, 42: fitting pin insertion hole, 43: holding member, 44: fixing member, C1, C2: optical cable, C3: optical Tape case Bull.

Claims (7)

An optical fiber connecting member used for connecting optical fibers having different mode field diameters,
A single, short built-in optical fiber having a mode field diameter intermediate between the mode field diameters of the two optical fibers is provided, and a tip end side is formed with a connection end face that is buttably connected to one of the optical fibers in a separable manner. An optical fiber connecting member, wherein an end portion is formed by a connecting portion for mechanical splice connection with the other of the optical fibers. An optical fiber connecting member used for connecting optical fibers having different mode field diameters,
A short built-in optical fiber having a mode field diameter that is the same as or close to the mode field diameter of the two optical fibers at both ends is provided, and a distal end portion is formed with a connection end face that is buttably connected to one of the optical fibers in a separable manner, An optical fiber connecting member, wherein a rear end portion is formed with a connecting portion for mechanical splice connection with the other of the optical fibers. An optical fiber connection device for connecting optical fibers having different mode field diameters to each other with an optical connector,
The optical connector includes a single, short-length built-in optical fiber having a mode field diameter intermediate between the mode field diameters of the two optical fibers, and has a front end connected to one of the optical fibers in a separable butt connection. It has an end face, and has a mechanical splice connected and fixed to the other end of the optical fiber on the rear end side,
One end of the optical fiber is connected to the front end of the optical connector via another optical connector, and the other end of the optical fiber is mechanically spliced to the rear side of the optical connector. Connection device. An optical fiber connection device for connecting optical fibers having different mode field diameters to each other with an optical connector,
The optical connector includes a short built-in optical fiber having a mode field diameter that is equal to or close to the mode field diameter of the two optical fibers at both ends, and is connected to the tip end side so as to be separably butt-connected to one of the optical fibers. It has an end face, and has a mechanical splice connected and fixed to the other end of the optical fiber on the rear end side,
One end of the optical fiber is connected to the front end of the optical connector via another optical connector, and the other end of the optical fiber is mechanically spliced to the rear side of the optical connector. Connection device. An optical fiber connection method for connecting optical fibers having different mode field diameters to each other with an optical connector,
A single, short built-in optical fiber having a mode field diameter intermediate between the mode field diameters of the two optical fibers is housed in the optical connector,
The front end of the optical connector is formed with a connection end face that is buttably connected to one of the optical fibers in a separable manner, and the rear end is formed with a mechanical splice that is connected and fixed to the other of the optical fibers.
An optical fiber, wherein one end of the optical fiber is connected to the front end of the optical connector via another optical connector, and the other end of the optical fiber is mechanically spliced to the rear end of the optical connector. Connection method. An optical fiber connection method for connecting optical fibers having different mode field diameters to each other with an optical connector,
The optical connector accommodates a short built-in optical fiber having a mode field diameter at both ends that matches or approximates the mode field diameter of the two optical fibers,
The front end of the optical connector is formed with a connection end face that is buttably connected to one of the optical fibers in a separable manner, and the rear end is formed with a mechanical splice that is connected and fixed to the other of the optical fibers.
An optical fiber, wherein one end of the optical fiber is connected to the front end of the optical connector via another optical connector, and the other end of the optical fiber is mechanically spliced to the rear end of the optical connector. Connection method. An optical fiber connection method for connecting optical fibers having different mode field diameters to each other with an optical connector,
As the optical connector, a built-in optical fiber is provided, a front end side has a connection end face that is separably butt-connected to one of the optical fibers, and a rear end side has a mechanical splice that is connected and fixed to the other of the optical fibers. With the configuration having, prepare a plurality of types of optical connectors having various mode field diameters in the built-in optical fiber,
Select the type of the optical connector that has an appropriate allowable loss range according to the mode field diameter of the two optical fibers connected to each other,
An optical fiber, wherein one end of the optical fiber is connected to the front end of the optical connector via another optical connector, and the other end of the optical fiber is mechanically spliced to the rear end of the optical connector. Connection method.

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