JP2004077658A - Optical connector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an optical connector which can be used for splicing of single mode optical fibers for high power transmission. <P>SOLUTION: A connection part 10 wherein a plurality of grated index optical fibers 12 and 13 having different core diameters are arranged in the ascending order of core diameter from the front end of the single mode optical fiber 11 toward the connection end face 15 is provided between the front end of a single mode optical fiber 11 and a connection end face 15, and thus a spot size on the connection end face 15 is enlarged, and optical power per unit area is reduced, and a high power optical signal (or exciting light) can be propagated. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, in a transmission method using WDM, Raman amplification, or the like, even when a high-power (for example, 1 W or more) optical signal (or pumping light) propagates in an optical fiber, light that can be used at a connection portion thereof is used. It is about connectors.
[0002]
[Prior art]
In recent years, communication systems using optical fibers have been increasingly demanded. Various optical fibers such as a multi-mode optical fiber and a single-mode optical fiber are used, and various optical connectors are used in connection portions thereof.
[0003]
Optical connectors have been designed so as to reduce the axial loss, inclination, and gap between optical fibers when connected, in order to reduce the optical loss. By controlling these parameters, various low-loss optical connectors have been realized.
[0004]
FIG. 1 shows an example of a main portion of a conventional optical connector, here an example of a connecting portion including an end of an optical fiber to be connected. An optical fiber 1 (outer diameter of about 125 μm) is a ferrule 2 (in the case of an SC connector, It is housed in a tubular member called an outer diameter of about 2.5 mm and an inner diameter of about 125 μm), and its tip forms a flush connection end face 3 with the ferrule 2.
[0005]
The optical fiber 1 includes a core 4 and a clad 5, and an optical signal (or pump light) propagates while being confined in the core 4.
[0006]
[Problems to be solved by the invention]
By the way, single mode optical fibers are mainly used for optical fibers currently used for optical communication because of the possibility of large capacity communication. Since the single mode optical fiber has a very small core diameter of about 10 μm, the power density becomes very large when a large-capacity optical signal (or pumping light) is propagated, and the end face may be damaged at the connection part of the optical connector. However, there is a problem that a fatal defect (such as a fiber fuse phenomenon) of the optical fiber starting from that portion may occur.
[0007]
An object of the present invention is to realize an optical connector that can be used for connecting a single mode optical fiber for high power transmission.
[0008]
[Means for Solving the Problems]
Apart from the optical connector, as a technology related to optical fibers, as a technology for connecting fibers with different core diameters, or as a technology for realizing a collimator, the core diameter of a single mode optical fiber is expanded and propagated in the optical fiber. Under the appropriate conditions, a technology to spread or restore the intensity distribution of the optical signal in a plane perpendicular to the axial direction of the optical fiber or to restore the original (TEC optical fiber technology), and a single mode optical fiber and a graded index type optical fiber A technique of spreading or returning the intensity distribution of an optical signal propagating in an optical fiber in a plane perpendicular to the axial direction of the optical fiber by connecting the optical signals (IEICE Technical Report 2002-7, pp. 33) has been developed. Exists.
[0009]
In the present invention, in order to solve the above-mentioned problems, the technology for combining the above-mentioned graded index type optical fibers is employed to increase the spot size at the connection portion, reduce the optical power per unit area, and provide a high-power light. An optical connector capable of transmitting a signal (or excitation light) without any problem is realized.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 2 shows an outline of a connecting portion in a first embodiment of the optical connector of the present invention, here, an embodiment corresponding to claim 1. In the drawing, reference numeral 11 denotes a high-power optical signal (or pump). A single mode optical fiber for transmitting light, 12 is a graded index (GI) optical fiber for spot size expansion, 13 is a graded index (GI type) optical fiber for spot size expansion transmission, and 14 is a tube (In the case of an SC connector, an outer diameter of about 2.5 mm, an inner diameter of about 125 μm, and ferrules of other sizes are also applicable).
[0011]
The three optical fibers are housed in a ferrule 14 in the order of a single mode optical fiber 11, a GI type optical fiber 12, and a GI type optical fiber 13 such that their central axes are coincident and their end faces are in contact with each other. The distal end of the mold optical fiber 13 forms a flush connection end face 15 together with the ferrule 14, and these constitute a connection portion 10 of the optical connector.
[0012]
Here, the outer diameters of the single mode optical fiber 11, the GI type optical fiber 12, and the GI type optical fiber 13 are all about 125 μm, which is almost equal to the inner diameter of the ferrule 14, and the core diameters a1, a1 of the respective cores 111, 121, 131. a2 and a3 are in a relationship of a1 <a2 <a3, and are arranged so that the core diameters are arranged from small to large from the tip of the single mode optical fiber 11 toward the connection end face 15. Thereby, the spot size diameter of the optical signal transmitted from the direction of the optical fiber 11 is enlarged.
[0013]
The light that has propagated through the optical fiber 11 is propagated to the GI optical fiber 13 and then to the GI optical fiber 13 in the connection portion 10 of the optical connector. At this time, the length of the GI optical fiber 12 is designed to be 1/4 pitch of the wavelength of the optical signal (or the excitation light) (the length of the GI optical fiber 13 is not particularly limited, and the mounting operation is not limited. The optical signal that has propagated through the optical fiber 11 in a Gaussian distribution in a plane perpendicular to the axial direction of the optical fiber while maintaining the shape of the Gaussian distribution. It is possible to propagate the GI optical fiber 13 in the spread state.
[0014]
The spot size radius w of an optical signal (or pump light) propagating in the GI optical fiber 13 is:
w = {(λ / πn) · Ag} ^1/2
However, Ag = r / (2Δ) ^1/2
Is reported. Here, r is the radius of the core 131 of the GI optical fiber 13, Δ is the relative refractive index difference between the core and the clad of the GI optical fiber 13, λ is the wavelength of the optical signal (or pump light), and n is the GI light. This is the refractive index of the core 131 of the fiber 13.
[0015]
The spot size radius w of the optical signal propagating in the GI optical fiber 13 is determined from the radius r of the core, the relative refractive index difference Δ, the signal light wavelength λ, and the refractive index n. This makes it possible to make the spot size of the optical signal (or the excitation light) in the GI optical fiber 13 several times larger than that in the case where the light signal propagates through the single mode optical fiber 11. Since the end of the GI optical fiber 13 forms the connection end face 15 together with the ferrule 14, the optical connector according to the present invention can reduce the peak power of the optical power at the connection portion 10.
[0016]
When manufacturing the optical connector of the present invention, the connection surface 16 between the transmission optical fiber 11 and the spot-size expanding GI optical fiber 12 and the spot-size expanding GI optical fiber 12 and the spot-size expanding GI light By assembling the connection surface 17 with the fiber 13 without any gap and maintaining the state fixed to the ferrule 14, it is possible to prevent problems from occurring at the connection surfaces 16 and 17.
[0017]
Here, since the length of the representative optical connector ferrule 14 in the axial direction is 8 mm or more, a part of the transmission optical fiber 11, the GI optical fiber 12 for increasing the spot size, the connection surface 16 thereof, and the spot size are increased. GI optical fiber 12 for transmission and GI optical fiber 13 for spot size expansion transmission and its connection surface 17 can be incorporated in optical connector ferrule 14, realizing an optical connector that is not different from ordinary optical connector in appearance. It is possible to
[0018]
On the other hand, as shown in FIG. 3, when the above-mentioned connecting portions 10 are connected to each other via an optical connector plug, an adapter or the like (not shown), the connecting portion 21 is very unstable due to frequent attachment and detachment. is there. However, in the case of the optical connector of the present invention, the peak power of the signal light at the connection portion 21 is reduced due to the expansion of the mode field diameter of the signal light at each connection end face 15. Is designed to have no problems.
[0019]
As shown in FIG. 4, there is a type of optical connector in which a refractive index matching agent 22 is applied to the connection portion 21 in order to reduce the influence of the gap. When an ordinary optical fiber is used, the peak power is large, so that there is a high possibility that the refractive index matching agent 22 applied to the connection portion 21 is damaged. However, in the optical connector of the present invention, the peak power is small. Therefore, no problem occurs even if the refractive index matching agent 22 is applied to the connection portion 21.
[0020]
FIG. 5 shows an outline of a connecting portion in an optical connector according to a second embodiment of the present invention, here, an embodiment corresponding to claim 2, which is formed by a tip of a GI optical fiber 13 and a ferrule 14. By polishing the connection end face of the connection portion 10 to a spherical surface 15 ′, it is possible to design so that the connection portion 21 can be connected without any gap.
[0021]
FIG. 6 shows an example of an entire optical connector to which the present invention is applied, and an optical fiber 11 for transmitting an optical signal (or pumping light) (in FIG. In this case, the coated state of the optical fiber is referred to as an optical fiber 11), and an optical connector plug 31 having the connecting portion 10 of the present invention and a pair of optical connectors An adapter 32 for detachably connecting a plug 31 (however, only one is shown in the drawing). This optical connector has almost the same components as the conventional optical connector except for the connection portion 10. By applying the present invention, a high-power optical connector having the same structure as the conventional optical connector is realized. It is possible.
[0022]
【The invention's effect】
As described above, according to the present invention, an optical signal (or pump light) having a high peak power incorporating the technology of the present invention is provided at a connection portion of an optical transmission line for transmitting an optical signal having a high optical power. By using an optical connector that can withstand the above, the optical connector technology will be used even in places where connection was originally regarded as dangerous.
[Brief description of the drawings]
FIG. 1 is a schematic view of a connection part showing an example of a conventional optical connector. FIG. 2 is a schematic view of a connection part showing a first embodiment of the optical connector of the present invention. FIG. FIG. 4 is a schematic view of a connection in the first embodiment. FIG. 4 is a schematic view of a connection in the first embodiment of the optical connector of the present invention. FIG. 5 shows a second embodiment of the optical connector of the present invention. FIG. 6 is an explanatory diagram showing an example of the entire optical connector to which the present invention is applied.
10: connection part, 11: single mode optical fiber, 12: GI optical fiber for spot size expansion, 13: GI optical fiber for spot size expansion transmission, 14: ferrule, 15, 15 ': connection end face, 16, 17 : Connection surface, 21: connection portion, 22: refractive index matching agent, 31: optical connector plug, 32: adapter, 111, 121, 131: core.

Claims (2)

An optical connector for connecting a single mode optical fiber for high power transmission,
A plurality of graded index optical fibers with different core diameters are arranged between the tip of the single mode optical fiber and the connection end face so that the core diameters are arranged from smaller to larger diameter from the tip of the single mode optical fiber toward the connection end face. An optical connector characterized by having a connection portion formed as described above. The optical connector according to claim 1, wherein the connection end surface is polished to a spherical surface.

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