JP3253472B2 - Non-reflective termination of optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-reflection terminal of an optical fiber in a system using the optical fiber.

[0002]

2. Description of the Related Art For example, as shown in FIG. 6, light from one transmission device 16 is split by an optical splitter 12 into three optical fibers 14A, 14B, and 14C, and the optical fibers 14A,
B, the other transmission device 16 is connected.
In some cases, nothing is connected to 4C. In such a case,
It is necessary to perform anti-reflection processing on the end of the optical fiber 14C.

FIG. 7 shows a conventional non-reflection processing method. (1) Refractive index matching method: A matching agent 18 is attached to the end face of the optical fiber 14 as shown in FIG. (2) End-surface irregular reflection method: As shown in FIG. 3B, the end surface of the optical fiber 14 is crushed with pliers or the like. (3) Oblique polishing method: A connector 20 is attached to the end of the optical fiber 14 as shown in FIG.
Is polished obliquely (for example, 8 °).

[0004]

[Problems to be solved by the invention]

(1) In the case of the refractive index matching method: Since the matching material is in the form of oil or grease, it may flow out, and a countermeasure is required. The characteristics are degraded by the inclusion of foreign matter. (2) In the case of the end surface irregular reflection method: If foreign matter adheres to the end surface, the characteristics are deteriorated. Since the end face is fragile, there is a possibility that chipping may proceed, the characteristics may be degraded, or the chip may damage other parts. (3) Also in the case of the oblique polishing method: If foreign matter adheres to the end face, the characteristics are deteriorated.

[0005]

SUMMARY OF THE INVENTION One of the major features of the present invention is that an optical fiber connector is used to solve the problem. Therefore, a brief description of the optical fiber connector is considered to be useful for understanding the present invention.

As an example, FIG. 8 shows an MT (Mechanically
Transferable) connector (Fujikura Technical Report, No. 8)
No. 4, p.58-63). (A) is an assembly structure diagram,
(B) is a structural diagram of the plug. 22 is an optical fiber tape core, 24 is an optical fiber (glass part excluding coating)
It is. 32 is a plastic ferrule. The optical fiber 24 is inserted into the main body 320, fixed with an adhesive, and the end face 322 where the optical fiber 24 is exposed is polished. In addition, 25 is a fiber hole, 26 is a boot. At the time of connection, guide pin 34 is inserted into guide pin hole 3
6, the end faces 322 are butted against each other, and the state is held by the clamp spring 38. FIG. 8 shows a multi-core connector. There are also single-core connectors and various connectors other than the MT type, which are widely known.

Next, means for solving the problem will be described. The following diagram is an example in which the above-described MT connector is used. Of course, it is not limited to the MT type.
The type of connector does not matter. As illustrated in FIG.
(1) The optical fiber 24 is inserted and fixed in the connector ferrule 32 of the optical fiber, (2) the optical fiber 24 in the ferrule 32 is cut obliquely, and a gap 40 is formed between the cut surfaces. (3) Fill the gap 40 formed between the cut surfaces with a resin, for example, an optical adhesive 42. Numeral 30 indicates the entire non-reflection terminal.

The above-described non-reflective terminal 30 is manufactured as follows. (1) The optical fiber 24 is inserted into a connector ferrule 32 of an optical fiber integrally formed with a predetermined mold, and an adhesive is injected from a central window 323 to fix the optical fiber 24. (2) From the side surface of the ferrule body 320, a groove 41 having a depth exceeding the optical fiber is cut obliquely to the optical fiber. Thereby, a gap 40 is formed between the optical fibers 24. Here, the fiber groove 3 in the connector ferrule is used.
Since the optical fiber 24 is located on the optical fiber 24 (FIG. 8),
The setting of the cut depth of the groove 41 is easy. (3) Resin, for example, optical adhesive 42 in the groove 41
Insert

[0009]

[Operation] FIG. 1 (c) will be mainly described. (1) Since the optical fiber 24 is obliquely cut, if the angle φ1 is 8 ° or more, the end face 3 of the ferrule 32
The light 44 incident from the side 22 does not return to the optical fiber 24 when reflected by the first cut surface 241 of the optical fiber 24. (2) Refractive index n of optical adhesive 42 filling gap 40
When 2 is close to the refractive index n1 of the optical fiber 24, the reflected light becomes very small. (3) When the light transmitted and refracted by the first cut surface 241 is incident on the second cut surface 242, the refractive index n2 of the optical adhesive 42 is applied to the angle φ1 of the gap 40,
Due to the three factors of the width p of the gap 40, a considerable axial deviation d occurs. Therefore, light does not propagate to the optical fiber 24 ahead of the second cut surface 242 (right side in the figure). Therefore, there is no reflected return light from the optical fiber 24 after the second cut surface 242.

(4) The refractive index of the optical fiber 24 is n1, the refractive index of the optical adhesive 42 is n2, the incident angle of light on the first cut surface 241 is φ1 (equal to the inclination angle of the first cut surface 241), If the refraction angle is φ2,

(Equation 1) From these equations, if the refractive index n2 of the angle φ1 and the angle 2 of the gap 40 and the width p of the gap 40 are appropriately selected, the size of d becomes very large, and light does not propagate through the optical fiber 24.

(5) In the manufacturing method, the groove 4 having a depth exceeding the optical fiber 24 from the side surface of the ferrule main body 320.
By cutting 1 obliquely to the optical fiber,
The anti-reflection terminal 30 having the above structure can be easily obtained. (6) When the optical adhesive 42 exists in the gap 40 between the optical fibers 24, the first cut surface 241 and the second cut surface 242
No dirt, dust, etc.

[Optical fiber 2 ahead of second cut surface 242]
Regarding 4] The optical fiber 24 beyond the second cut surface 242 (on the right side in FIG. 1C) is essentially unnecessary. But,
It is very difficult to remove this due to manufacturing reasons. However, even if it remains, there is no influence on the reflected light by performing the above.

[0013]

Embodiment 1 Referring to FIG. This is a single core type. The above-mentioned MT type was used as the ferrule 32.
(A) is a plan view, (b) is a side view, and a part of the CC cross section is enlarged and shown in (c). The optical fiber 24 is an SM (Single Mode) single-core optical fiber made of quartz and has a refractive index n1 of 1.47. The inclination angle φ1 of the groove 41 is 45 °, the width p of the gap 40 (the groove 41) is 200 μm, and the refractive index n
2 was filled with 1.56 resin, for example, epoxy-based optical adhesive 42 (trade name: 353ND, manufactured by Epoxy Technology, USA). However, the resin used is the wavelength used (for example, 1.3
μm), and is not particularly limited as long as compatibility with the optical connector resin, viscosity, workability, and the like are good.

The light 44 incident from the end face 322 of the ferrule 32 is reflected by the first cut surface 241 of the optical fiber 24 and does not return to the optical fiber 24. Also, the first cut surface 24
The axis deviation d of the light when it is transmitted and refracted at 1 and enters the second cut surface 242 is 15.44 μm, and the radius of the core 240 (10 μm)
The optical fiber 24 before the second cut surface 242
Light does not propagate to Therefore, there is no reflected return light from the optical fiber 24 after the second cut surface 242.

The above-described non-reflective terminal 30 was manufactured as follows. (1) As in the case of normal connector assembly, the optical fiber core 22 is inserted and fixed in the ferrule 32, and the end face 322
Was polished. (2) The groove 41 having a width of 200 μm was cut from the side surface of the main body 320 of the ferrule 32 with a thin blade cutter, and the optical fiber 24 was also cut. (3) The cut surface was polished, washed with an ultrasonic cleaner, and dried. (4) The optical adhesive 42 was dropped into the groove 41 and placed in a vacuum oven so that the optical adhesive 42 was filled into the groove 41 without any gap and was cured. Incidentally, the standard effect conditions of the engineering adhesive of this example are 120 ° C. for 10 minutes and 80 ° C. for 15 minutes.

[Example of use place] The non-reflection end 30 is used in the following places. (1) FIG. 2 shows a case where the present invention is used in a reflection measurement system. Reference numeral 50 denotes a light source, 52 denotes a power meter, and 54 denotes an object to be measured. Unused terminal 58 of directional coupler 56 is connected to connector ferrule 6
0, and the non-reflective end 30 is connected to the connector. A matching oil is applied to the contact surface between the non-reflective end 30 and the connector ferrule 60. As described above, reflection from the unused terminal 58 is prevented.

As can be seen from this example, the anti-reflection termination 30 of the present invention is used in a state where a connector is connected in combination with another connector ferrule.

(2) FIG. 3 shows a case where the splitter 62 is used. Transmission devices 64 are connected to the ports 621 to 623 of the splitter 62 by connectors. Port 624 is unused. The anti-reflection terminal 3 of the present invention
If 0 is connected to the connector, there will be no reflection. If it becomes necessary to connect the transmission device 64 to the port 624 in the future, the reflectionless end 30 may be pulled out and the transmission device 64 may be connected to the connector.

[0019]

Embodiment 2 Referring to FIG. This is an example of a four-core non-reflection end 31. A four-core optical fiber tape is used as the optical fiber core 22, and a four-core ferrule 32 is used. Except for this, the configuration is the same as that of the single core of the first embodiment. The manufacturing method is the same.

The above embodiment relates to an MT connector made of a plastic ferrule as described above. Other connectors to which the present invention is applied include, for example, an SC having a zirconia ceramic ferrule.
(Sinple Contact) It is possible to apply to a terminal part such as a connector.

[Test Results] FIG. 5 shows a measurement system. Applying matching grease to the contact surface and applying non-reflective termination 30 (31)
Combined with a connector ferrule 66
With the high precision reflectometer 68 made by Packard,
The amount of return loss was measured. Non-reflective termination 3 for single core of embodiment 1
Table 1 below shows the measurement results of 0. "From the end face"
This is the return loss from the end face of the connector ferrule 66, and "from the gap" means the non-reflection end 3
This is the return loss from the gap 40 of 0.

[0022]

[Table 1]

Table 2 below shows the measurement results in the case of four cores according to the second embodiment.

[0024]

[Table 2]

In Tables 1 and 2, <-80 (1.31 μm
m) and <−55 (1.55 μm) indicate that the measured wavelength is below the measurement limit of the high-precision reflectometer 68 used.

[0026]

【The invention's effect】

(1) The optical fiber is inserted and fixed in the connector ferrule of the optical fiber, and the optical fiber in the ferrule is cut obliquely and a gap is formed between the cut surfaces. A connector-type non-reflection terminal is obtained, which is easy to attach and detach, and enables easy handling. (2) When the gap formed between the cut surfaces of the optical fiber is filled with an optical adhesive, the principle portion that becomes non-reflective (first
Since the cut surface 241, the second cut surface 242, etc.) are sealed with an adhesive, they are resistant to dust and dirt and have high reliability.

(3) An optical fiber is inserted and fixed in a connector ferrule of the optical fiber, and a groove having a depth exceeding the optical fiber is cut obliquely from the side surface of the ferrule main body with respect to the optical fiber. Non-reflective terminations can be easily manufactured. According to this method, the optical fiber 24 remains ahead of the second cut surface 242 (on the right side in FIG. 1C), but as described above, this effect can be eliminated.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an example of a use place of a non-reflection terminal 30 of the present invention.

FIG. 3 is an explanatory diagram of another example of a use location example of the non-reflection terminal 30 of the present invention.

FIG. 4 is an explanatory diagram of a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a non-reflective termination test circuit according to the present invention.

FIG. 6 is a general explanatory diagram when a non-reflection terminal is used.

FIG. 7 is an explanatory diagram of a conventional non-reflection terminal.

FIG. 8 is an explanatory diagram of an example of an optical fiber connector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Optical branching device 14 Optical fiber 16 Transmission device 18 Matching agent 20 Connector 200 Connector end surface 22 Optical fiber core wire 24 Optical fiber 240 Optical fiber core 241 First cut surface 242 Second cut surface 30, 31 Non-reflective termination 32 Ferrule 320 Ferrule main body 322 Ferrule end face 34 Guide pin 36 Guide pin hole 38 Clamp spring 40 Gap 41 Groove 42 Optical adhesive 44 Light 50 Light source 52 Power meter 54 Device under test 56 Directional coupler 58 Unused terminal 60 Connector ferrule 62 Splitter 621- 624 port 64 transmission device 66 connector ferrule 68 high precision reflectometer

Continuing on the front page (72) Michio Akiyama 1440, Mitsuzaki, Sakura-shi, Chiba Prefecture Inside Fujikura Sakura Plant (72) Inventor Shinji Nagasawa Nippon Telegraph and Telephone Corporation 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo (56) References JP-A-5-40210 (JP, A) JP-A-2-119613 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/00-6 / 02 G02B 6/10 G02B 6/16-6/26 G02B 6/30-6/44

Claims (2)

(57) [Claims] [Claim 1] A optical fiber connector ferrule of the optical fiber is inserted and fixed, from the body side surface of the ferrule, beyond the optical fiber
Groove at an angle to the optical fiber.
Wherein the optical fiber within the ferrule is cut obliquely, and a gap is formed between the cut surface I, the gap
Is the light transmitted and refracted by the first cut surface on the ferrule end surface side.
From the second cut surface facing the first cut surface due to axial misalignment
A non-reflective end of an optical fiber that is formed so that light does not propagate to the previous optical fiber . 2. The non-reflection end portion of the optical fiber according to claim 1, wherein a resin is filled in a gap formed between the cut surfaces.