JPS6216424B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is effective in one step in the optical fiber fusion splicing method, that is, in the step of optically connecting the end faces of optical fibers to each other via a matting liquid. Concerning methods for carrying out.

When fusion splicing optical fibers in the longitudinal direction, an appropriate length of the coating is removed from each end of a pair of optical fibers to be spliced, and these removed portions are trimmed to form optical fiber ends, and then, The end faces of both optical fibers are opposed to each other, and the end faces of both optical fibers are abutted against each other, and the pair of optical fibers are fused and spliced by discharge heating (or laser heating).

When connecting optical fibers as described above,
After setting the distance between the end faces of both optical fibers appropriately, the provision of fusion heat to the ends of these optical fibers is started, and the resulting heating state is maintained for a certain period of time while the end faces of the optical fibers are butted against each other. However, before setting the end face spacing at this time, an alignment process is performed to align the cores of both optical fibers with each other, and this alignment process is important for ensuring a low-loss optical fiber connection. It is said that

A common alignment method is to pass a light pulse across both optical fibers facing each other with a predetermined distance between their end faces, and in this state of passing, the end of one or both optical fibers is moved horizontally or vertically. Methods such as displacing the
In addition, when the light receiving power in the light receiving side optical fiber reaches its maximum value, it is assumed that the cores have coincided with each other due to the above-mentioned end operation.

During alignment, that is, alignment, sufficient detection output (received light power) is obtained by efficiently transmitting light from the transmitting side optical fiber to the receiving side optical fiber, and in the following process, the source level and The maximum value of received light power (received light power when the axes are aligned) should also be accurate.

By the way, as a preliminary measure when setting the end face spacing for alignment, the end face spacing for discharging, etc., if the received light level, source level, etc. at these end face spacings can be accurately determined, the accuracy can be determined using that level as the reference value. It is possible to achieve high optical fiber alignment, fusion splicing, etc.

Therefore, a recently proposed means, that is, a means for interposing a matching liquid having the same refractive index as the core between the end faces of both optical fibers and optically connecting the cores to each other via the matching liquid, is as described above. It can be said that it is effective in satisfying technical matters.

That is, since the means for optically connecting cores to each other via a matching liquid with a predetermined refractive index is equivalent to fusion splicing optical fibers to each other, the above-mentioned accurate level is determined in such a state, and this If the optical fibers are aligned with each other using the reference value, a more accurate alignment state can be obtained, and the following optical fiber fusion splicing can also be performed with high precision.

By the way, the distance between the end faces when optically connecting the end faces of the optical fibers with each other using a matching liquid, that is, the interval when aligning the end faces with the matching liquid in a bridging state, is usually 10 μm.
However, due to errors in the amount of movement of the optical fiber end (approximately ±4 μm) when setting the alignment distance, errors in the amount of matching liquid applied, etc., it becomes difficult to obtain a good bridging state of the matching liquid. Due to this, it has become impossible to set an accurate source level, making it impossible to realize a low-loss optical fiber connection.

(Object of the Invention) In view of the above-mentioned problems, the present invention, when optically connecting the end faces of optical fibers to each other via a matching liquid, determines the connection state using a determination means in several stages to accurately determine the source level. The purpose is to enable configuration and, ultimately, low-loss optical fiber connections.

(Structure of the Invention) The present invention allows the end faces of a pair of optical fibers to face each other, optically connects these end faces with a matching liquid to align the axes of the optical fibers, and then In a method of longitudinally fusion splicing optical fibers by abutting the end faces of the fibers against each other, the end faces of these optical fibers are opposed to each other so that light is propagated across the pair of optical fibers. A matching liquid having a refractive index approximately equal to that of the cores of the optical fibers to be connected is applied to the end face of at least one of the optical fibers facing each other at intervals. relatively moving the ends of the pair of optical fibers in a butting direction along their axes so that the light receiving power of the light receiving side optical fiber reaches a predetermined level when light is transmitted across the fibers,
The ends of the optical fibers are connected to each other using a matching liquid, and if the received light power at the predetermined level cannot be detected, the level is changed, and the ends of the optical fibers are aligned in the direction of these axes so that the received light power is at the changed level. If the received light power at the changed level cannot be detected, move the optical fiber ends relatively in the matching direction to connect the optical fiber end faces to each other using a matching liquid. While making contact, the received light power in the same state is detected and used as a reference value, and then the end of the optical fiber is moved in its axial direction, and the received light power due to the movement becomes a predetermined value with respect to the reference value. May it be,
It is characterized in that the end faces of the optical fibers are connected to each other using a matching liquid.

(Example) Examples of the present invention will be described below with reference to the drawings.

Figures 1A to 1H show an outline of the method of the present invention in the order of steps, and in these figures 1A and 1B are
2A and 2B are the ends of the optical fibers 1A and 1B, and 3A and 3B are the end faces thereof.

4 is the end face 3A, 3 of the optical fiber 1A, 1B.
This is an applicator for applying matching liquid to B, and this applicator 4 also serves as an end face spacing setting tool (abutment plate), and has a thin plate-like small protrusion 5 at its tip.
is formed.

Reference numeral 6 denotes a matching liquid having a refractive index almost equal to that of the cores of the optical fibers 1A and 1B, and this is made of, for example, glycerin dissolved in alcohol.

In the present invention, when each step shown in FIG. 1 is carried out, the optical fibers 1A and 1B each have a coating layer on their outer periphery, and the coating layer is removed at the end portions 2A and 2B so that the optical fibers become bare. 2
B is trimmed by suitable cutting means.

Optical fiber ends 2A and 2B treated in this way
are fitted into the V-groove of the shaft mating base, and these ends 2
The coated portions of optical fibers 1A and 1B that are continuous with A and 2B are clamped using known slip-type holders.

FIG. 1A shows a state in which the predetermined portions of the optical fibers 1A and 1B are set as described above, so that the optical fiber ends 2A and 2B are aligned in a straight line, and the end faces 3A and 3B are aligned with each other. opposite.

On the other hand, the applicator 4 has advanced to a predetermined position so that the small protrusion 5 at its tip is located between the optical fiber end surfaces 3A and 3B, and the matching liquid 6 is applied to one side of the small protrusion 5. .

FIG. 1B shows a state in which the optical fiber ends 2A, 2B are moved toward the small protrusion 5 of the applicator 4, so that the optical fiber end surfaces 3A, 3B abut against both surfaces of the small protrusion 5. FIG. 1C shows a state in which the small protrusion 5 of the applicator 4 has retreated from between the end surfaces 3A and 3B after the collision.

As described above, by going through the steps shown in FIG. applied.

FIG. 1D shows that at the same time as the applicator 4 is removed, one optical fiber end 2A is transferred to the other optical fiber end 2B.
The optical fiber end face 3A is
shows a state in which the movement of the end portion is stopped before it comes into contact with the matching liquid 6 on the optical fiber end surface 3B side.

FIG. A detection means is employed.

First, the step moving means moves the clamping table of the optical fiber coating part forward (in the butting direction) or backward (in the anti-butting direction) one step at a time along the optical fiber axis direction, as shown in FIG. A drive system 7 consisting of a pulse motor capable of forward and reverse rotation and a precise transmission mechanism is provided on the clamping table 8 side of one optical fiber 1A.

The measuring means is installed in advance on the optical fibers 1A and 1B when carrying out the above steps, and the measuring means may be a known transmission method, backscattering method, etc.
The appropriate one will be adopted.

A specific example of the measuring means will be briefly described with reference to FIG. 2. On the input end side of the optical fiber 1A, which is the transmitting side, there is an LED stabilized light source, an LD stabilized light source, etc.
A suitable light source 9 is connected, and a photodetector 1 such as a PD, APD, general-purpose photovoltaic meter, high-sensitivity photovoltaic meter, etc. is connected to the output end side of the optical fiber 1B, which is the receiving side.
0 is connected.

Furthermore, the number of step movements of the drive system 7 mentioned above,
Both 7 and 10 are connected to the controller 11 so that the measured values of the photodetector 10 and the like are input to the controller 11.

In the present invention, when the optical fiber end faces 3A and 3B are optically connected to each other by the matching liquid 6,
The drive system 7 moves one optical fiber end 2A toward the other end 2B in small steps, and at this time, the light source 9 moves the optical fibers 1A and 1B to the photodetector 10. While transmitting an optical signal (light pulse) and detecting the received light power by the photodetector 10, the optical fiber end faces 3A, 3
It is determined whether B is optically connected to each other by the matching liquid 6.

Note that light passing through both optical fibers 1A and 1B, which will be described later, is possible only when both optical fiber end faces 3A and 3B are facing each other and the cores of these optical fibers 1A and 1B are at least partially coincident. .

Therefore, as mentioned above, both optical fiber end faces 3
When A and 3B are opposed, both optical fibers 1A,
The state is such that light can pass through 1B.

As mentioned above, when one optical fiber end 2A is stepped forward toward the other optical fiber end 2B, the distance between the end faces 3A and 3B narrows, and the received light power increases as shown in Figure 3A. breath,
Immediately before the end surface 3A contacts the matching liquid 6 on the end surface 3B side, the received light power becomes _P1 .

When the step is further advanced, the end faces 3A and 3B
The matching liquid 6 creates a cross-linked state between them.
At the moment when this bridging state occurs, the matching liquid 6 on the end surface 3B side, which had a hemispherical shape, is transferred to the end surface 3A.
When it comes into contact with the object, it is deformed and temporary light scattering occurs, so the received light power drops to the level P ₂ in Figure 3A.

In the subsequent forward movement, the matching liquid 6 between the end surfaces 3A and 3B converges into a stable shape (shape of shaft), so that the received light power increases to level _P3 in FIG. 3A.

In the first judgment according to the present invention, when the difference between P _{3 and P 1} in FIG. 6, the matching liquid connection is completed.

In this case, the difference in received power (0.3 dB or more) occurs when there is air between the two optical fiber end faces 3A and 3B (with Fresnel reflection loss), and when there is a matching liquid connection between the two optical fiber end faces 3A and 3B. (without Fresnel return loss).

Next, if the above judgment cannot be made, the level is changed to see if P ₃ -P ₁ satisfies 0.2 dB or more, as shown in Figure 3 B, and in this state, the optical fiber end 2A is stepped a predetermined number of times. By moving forward, a state in which P ₃ −P ₁ is 0.2 dB or more is searched.

In this case, 0.2 dB or more is a level value when setting the splice loss after optical fiber fusion splicing to, for example, 0.3 dB, and by setting such a level value, the 0.2 dB or more
If the above requirements are met, a connection loss of 0.3dB can be achieved.

This level (0.2 dB or more) is a value based on a rule of thumb.

When a state that satisfies the above-mentioned set value is detected in this second judgment, the optical fiber end 2A is moved back in steps to match the position, and a correction movement to deal with the drive system backlash is also performed. completes the predetermined matching fluid connection.

Furthermore, when the first and second judgments cannot be made, the state in which the optical fiber end faces 3A and 3B are in contact with each other is detected, and when the step moves forward in this case, the moment when the end faces 3A and 3B come into contact, the first As shown in Figure 3C, the received light power level drops to _P4 , and then stabilizes to _P5 in Figure 3C.

After detecting the contact state between the end surfaces 3A and 3B, the third judgment is performed to search for _P3 such that _P3 - _P5 is 0.05 dB or more.For example, by moving forward M times, light is received. When the power _P5 can be detected, the optical fiber end 2A is stepped forward (M-1) times to detect a state that satisfies the above set value, and thus a predetermined state can be detected. When this happens, the optical fiber end 2A is stepped back to match that position, and the same backlash correction movement as described above is also performed, thereby completing the predetermined matching fluid connection.

0.05dB in the above means both optical fiber end faces 3
This is the level down when the optical fibers A and 3B come into contact with each other, and this is the level down caused by the bending of the optical fiber at the moment when the end faces 3A and 3B of both optical fibers are brought into contact.

Therefore, when a level drop of 0.05 dB or more is detected, the state of contact between the optical fiber end surfaces 3A and 3B can be confirmed.

This level (0.05 dB or more) is also a value based on empirical rules.

In addition, in the above, an example was described in which the matching liquid 6 is applied only to one optical fiber end face 3B, but the matching liquid 6 may be applied to both optical fiber end faces 3A and 3B and the above-mentioned method is carried out. In such a case, the matching liquid 6 may be applied to both sides of the small protrusion 5 of the applicator 4, and the steps A to E in FIG. 1 may be performed.

Next, programming for automating the above method will be explained with reference to FIG.

The characters and symbols shown in Figure 4 have the following meanings.

New: Latest light receiving power.

ld: Received light power one level before New.

Power( ): Read the new received light power at x=Power( ) and assign that value to x.

Pwr [φ]: Pwr is an abbreviation of Power, and φ is zero.

N ₁ : Step unit in the first judgment.

M: Default number of steps.

ZF: Step forward.

N ₂ : Step unit in the second judgment.

ZR: Step backward d ₁ : Backlash correction amount.

N ₃ : Step unit in the third judgment.

_d2 : Backlash correction amount.

In FIG. 4, the system advances step by step after being in the state shown in FIG. 1D, and the matters described in FIG. 3A are carried out as follows.

In the system, in No. 11, the received light power in D of FIG. 1 is set to New, and since step forward movement has not started, Pwr[φ]=New is maintained.

N ₁ =1 in No. 12 indicates that the following operations, processing, etc. are performed for each step.

Since N ₁ in number 13 is initially 1 and M is set to, for example, 5, N ₁ ≦M becomes Yes and ZF in number 14 is executed.

In No. 15, the received light power when the optical fiber end 2A is advanced by one step by ZF is New,
In No. 16, a comparison calculation is made to determine whether New satisfies New > ld + 0.3 dB, that is, whether or not it satisfies the matters described in Figure 3 A. If this is satisfied, select Yes to perform the specified operation. Complete.

If No in No. 16, N ₁ of No. 17 = N ₁ + 1
1 more step is added, and this command becomes 13
By entering the number, steps 14 to 16 will be executed again, and these will be repeated unless you say yes at number 16, but N ₁ = N ₁ + 1 at number 17
is added by 1 step, N ₁ = 1 + 1 (2
(3rd time), N ₁ = 2 + 1 (3rd time), N ₁ =
The number of steps increases like 5+1 (6th time),
Therefore, if M is 5, even if you try to move forward for the 6th time, M at No. 13 will be 5 and N ₁ will be 6, so N ₁ ≦ M will not be satisfied, and No. Get out.

When No. 13 is obtained in the system, the matters described in the system, that is, in Figure 3 (b) are carried out.

In this system, as before, a check is made to determine whether or not No. 24 is satisfied in M steps forward (the step is N ₂ ), and when this is detected, the result is Yes at No. 24, and the operation No. 26 is performed. .

That is, in No. 26, if M is set to 5 and No. 24 is satisfied by the second step forward (N ₂ = 2), it is sufficient to move backward by (M-N ₂ ) = (5-2) = 3 steps. Therefore, in No. 26, which executes step retraction, the optical fiber end 2A is retracted by 3 steps by ZR (M-N ₂ ) + d ₁ .
Further, the backlash correction amount _d1 of the drive system is also set back to complete the predetermined work.

By advancing M steps in the system,
When No. 24 cannot be satisfied, the system performs the steps described in Figure 3 C.

At number 31 in the system, New = Pwr [M]
Here, New is the received light power when the end surfaces 3A and 3B come into contact with each other by moving forward M times (the step is N ₃ ).

No. 32, N ₃ =M-1, indicates that the following operations and calculations are performed by step backwards with M as the reference.

If M at No. 32 is 5, N ₃ at No. 33 becomes 4, and if N ₃ ≧φ is satisfied, the result is Yes.

In No. 34, the received light power according to the above is set as New, and 35
At the turn, a comparison calculation is made to determine whether or not the New satisfies New>ld+0.05dB, that is, whether or not it satisfies the matters stated in Figure 3 C.
If No, one step is subtracted by N ₃ = N ₃ -1 in No. 36, and this command enters No. 33.
Numbers 34 and 35 will be executed again.

Here, if the number 32 M is 5, then the first
For number 33, N ₃ = 4, but if number 35 continuously gives No in the first and subsequent operations, then 36
By subtracting N ₃ by one step at the time, N ₃ = 3 (second time), N ₃ = 2 (third time)...
...N ₃ =-1 (sixth time). Therefore, at the sixth time, N ₃ ≧φ at No. 33 becomes No and Err processing is performed.

On the other hand, in No. 35, for example, Yes due to N ₃ = 2
If the number 37 is ZR (M - N ₃ ) + d ₂ , M is 5 and N ₃ is 2, and d ₂ is the backlash correction amount. Complete.

Note that all the numerical values mentioned in the above explanation can be changed and set arbitrarily.

In addition, for the above-mentioned received light power, step forward, step backward, etc., these signals can be input to the controller 11 shown in FIG. 2 and stored and processed electrically and electronically, and based on this, the signals shown in FIG. The drive system 7 can be automatically controlled as shown in FIG.

Furthermore, as described above, the optical fiber end face 3A,
After 3B is optically connected with the matching liquid 6, the axes are aligned (aligned) in the same state, and the source level in the aligned state is set. The distance between the end faces is set, discharge is started, and the ends of the optical fibers are moved to butt each other, and the optical fibers are connected to each other.

(Effects) As explained above, when optical fiber end faces are optically connected to each other via a matching liquid, the method of the present invention has a predetermined level of received light power, a changed level of received light power, and The above-mentioned connection state is created by detecting any of these, such as the received light power in a contact state.
Even if there are initial variations in the distance between the optical fiber end faces, the amount of matching liquid applied, the amount of movement of the optical fiber end, etc., it is possible to achieve a proper matching liquid connection that is not affected by these variations, and therefore the subsequent The source level in the alignment process can be set accurately, and based on this, low-loss optical fiber connections can be made.

Of course, the automation of optically connecting optical fibers to each other via a matching liquid can be easily achieved, and it can also contribute to the complete automation of optical fiber fusion splicing.

[Brief explanation of the drawing]

Fig. 1 A to E are explanatory diagrams showing an overview of the method of the present invention, Fig. 2 is a schematic diagram of the measuring means in the method of the present invention, and Fig. 3 A, B, and C are measurement situations of received light power in the method of the present invention. FIG. 4 is a flowchart showing programming when automating the method of the present invention. 1A, 1B... Optical fiber, 2A, 2B... End of optical fiber, 3A, 3B... End face of optical fiber, 4... Matching liquid applicator, 5... Small protrusion of applicator, 6... Matching liquid, 7... Drive system,
9...Light source, 10...Photodetector.

Claims (1)

[Claims] 1. The end faces of a pair of optical fibers are made to face each other, and these end faces are optically connected to each other using a matching liquid to align the axes of the optical fibers, and then the end faces of the pair of optical fibers are butted against each other. In the method of fusion splicing these optical fibers in the longitudinal direction, the end faces of these optical fibers are opposed to each other so that light is propagated across the optical fibers forming a pair, and the end faces of the optical fibers are arranged to face each other with a distance between the end faces. The end face of at least one of the optical fibers is coated with a matching liquid having a refractive index almost the same as the core of the optical fibers to be connected, and then light is received in a state where light is transmitted across these optical fibers. The end portions of the paired optical fibers are moved relative to each other in the abutting direction along the axial direction so that the received light power of the side optical fibers is at a predetermined level, and the end surfaces of the optical fibers are connected to each other using a matching liquid, and the optical fibers are connected to each other using a matching liquid. If the level of received light power cannot be detected,
The optical fiber end portions are moved in the axial direction again so that the received light power reaches the changed level, the optical fiber end faces are connected with each other using a matching liquid, and the light receiving power is adjusted to the changed level. If the power cannot be detected, the ends of the optical fibers are relatively moved in the direction of alignment so that the end faces of the optical fibers come into contact with each other, and the received light power in the same state is detected and used as a reference value, and then the above An optical fiber end face in an optical fiber fusion splicing method in which the optical fiber ends are moved in the axial direction and the optical fiber end faces are connected using a matching liquid so that the received light power due to the movement becomes a predetermined value with respect to the above reference value. Mutual matching connection method.