JPS6216402B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is a method for setting the zero spacing, which is important when fusion splicing optical fibers, that is, setting the end face spacing of the optical fibers to be connected to zero. Regarding the method.

(Prior art) The main steps in fusion splicing optical fibers are alignment of the optical fiber ends, setting of the distance between the optical fiber end faces, butt movement of the optical fiber ends, and provision of discharge heat to the optical fiber ends. etc., and the others are steps incidental to the above steps.

Even in the current situation where optical fiber fusion splicing is moving towards full automation, the main point remains the same.
The steps shown in Figures I to B are taken.

To explain this below, the optical fibers 1A and 1B each have a coating layer on the outer periphery, and the coating layer is removed at the end portions 2A and 2B, resulting in a bare state, and these end portions 2A and 2B are trimmed by appropriate cutting means. It will be done.

Optical fiber ends 2A, 2 thus pretreated
B is fitted into the V-groove of the shaft mating stand, and the coated portions of the optical fibers 1A, 1B that are continuous with these end portions 2A, 2B are clamped via a known slip-type holder.

As a result, the optical fiber ends 2A and 2B are aligned in a straight line, and their end faces 3A and 3B are opposed to each other.

Figure 1A shows optical fibers 1A and 1B in the above
This diagram schematically shows a state in which the primary end face spacing G ₁ is set, and in this case, the optical fiber ends 2A, 2
B is moved in the direction of the spacing setting plate 4 via the slip type holder, and its end faces 3A and 3B collide with both sides of the spacing setting plate 4, thereby setting a primary end face spacing _G1 of about 0.5 mm. Ru.

Next, the spacing setting plate 4 is removed from between the optical fiber end faces 3A and 3B, and then, as shown in FIG. A secondary end face spacing _G2 is set.

After setting the second end face distance, the axes of both the optical fiber ends 2A and 2B are aligned (to align the cores with each other) as shown in FIG. This is done by adjusting the optical fibers 2A and 2B horizontally, vertically, etc. At this time, the optical signal is passed across the optical fibers 1A and 1B, and the maximum received light power is determined by monitoring on the receiving side. When this can be confirmed, the cores can be considered to match each other.

After the cores are aligned with each other as described above, one optical fiber end 2A is moved toward the other optical fiber end 2B, and the optical fiber end surfaces 3A and 3B are butted against each other, as shown in FIG. 1D. As a result, the distance between the end faces becomes 0.

After that, one optical fiber end 2B is moved by a predetermined amount in a direction away from the other optical fiber end 2B, thereby creating a tertiary end face spacing of about 10 μm.
G ₃ is set.

This tertiary end face spacing G ₃ is a suitable spacing for starting a discharge, and at this point, a known discharge device, that is, a discharge mainly using a pair of discharge electrodes 5M and 5N, is generated as shown in Fig. 1. At the same time, one optical fiber end 2A is moved again toward the other optical fiber end 2B, and thus the optical fiber ends 2A and 2B absorb the discharge heat at this time (discharge time is about 1 second). Butt movement (travel amount > 10μ)
(m) are fused to each other, and the connection work is completed as shown in Fig. 1 (g).

In addition, in a recent proposal, a matching liquid (glycerin dissolved in alcohol) having optical coupling properties is applied to either or both of the optical fiber end faces 3A and 3B between A and B in Figure 1. , during alignment in Figure 1C, the matching liquid 6 optically couples both optical fiber end faces 3A and 3B as shown in Figure 2A, so that the received light power can be detected with high sensitivity during alignment. .

In addition, both optical fibers 1A, 1 in FIG.
By aligning the axes of B, the aforementioned maximum received light power can be detected, but when the end faces 3A and 3B of both optical fibers are brought into contact with each other in the subsequent step of FIG. 1D, that is, as shown in FIG. When the end faces 3A and 3B of the fibers 2A and 2B are brought into contact with each other while maintaining a straight line between them (contact pressure is assumed to be 0), the received light power at this point is such that the cores of both optical fibers 1A and 1B are in direct contact with each other. This exceeds the maximum received light power during the axis alignment.

Therefore, by detecting the peak of the received light power, it can be seen that the distance between the optical fiber end faces 3A and 3B has become 0, but the peak occurs when the received light power changes from an increasing trend to a decreasing trend. Therefore, it is necessary to temporarily maintain a state in which the received light power shows a decreasing tendency.

That is, the end face spacing > 0 (state in Fig. 2 A),
End distance = 0 (state in Figure 2 B), end distance <0
The received light power is changed to an increasing trend, a peak, and a decreasing trend through the operation (state shown in Fig. 2 C). At this time, when the end face spacing is <0 as shown in Fig. 2 C, the end faces 3A and 3B are in strong contact with each other. At the same time, the optical fiber ends 2A and 2B are bent to each other, and the received light power is reduced due to the resulting loss.

Thereafter, in order to return the state shown in FIG. 2C to the end face distance = 0 shown in FIG. 2B, the optical fiber ends 2A and 2B are
is relatively moved by a predetermined amount in the opposite direction.

By the way, as a means of confirming the above-mentioned end face spacing = 0, conventionally there was a method using a microscope, but when using this method, even if the end face distance is enlarged with a microscope, the end face distance can be determined with the naked eye with low resolution. Since it is necessary to identify, there will be variations,
In particular, when a matching liquid is applied to the end face of an optical fiber, this tendency for variation increases.

On the other hand, it is also possible to set the end face spacing = 0 while monitoring the received light power as described above.
In this case as well, there is an error when measuring the received light power.
Also, even if the peak of the received light power is detected,
It is necessary to confirm whether the end face spacing is actually 0 or not, and technical considerations including these points are required.

As a matter of course, if the end face interval = 0 cannot be set accurately, the tertiary end face interval during discharge
_G3 will also go awry, and low-loss optical fiber connections can no longer be expected.

(Object of the Invention) In view of the above-mentioned problems, the present invention provides a method in which the end face spacing = 0 can be accurately set during optical fiber fusion splicing, and the setting operation can be automated.

(Structure of the Invention) The present invention involves, after the ends of a pair of optical fibers are made to face each other, the axes of these optical fiber ends are aligned, the distance between the optical fiber end faces is set, the optical fiber ends are butted and moved, and the optical fibers are brought into contact with each other. In a method of fusion splicing the ends of paired optical fibers to each other by a necessary process such as applying discharge heat to the ends, light is passed across the paired optical fibers, and in the light-passing state, these The ends of the optical fibers are relatively moved in the abutting direction, and a tendency of the maximum received light power to decrease is detected by measurement on the light-receiving optical fiber, and at the time of this detection, the abutting movement of the optical fiber ends is stopped. After the end surfaces of the optical fibers are brought into contact with each other, the ends of the optical fibers are relatively moved in the opposite direction while the received light power is being detected;
These operations of relatively moving the ends of the optical fibers in the direction of axis deviation are performed at least once in any order, thereby creating a state in which the distance between the end faces of the optical fibers becomes 0, and the axis of the ends of the optical fibers. The method is characterized in that a misaligned state is created, and then the ends of these optical fibers are aligned with each other.

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

The specific example of the optical fiber fusion splicing method on which the present invention is based is as described in the steps of FIG. Only the following will be extracted and explained.

In the present invention, the distance between the end faces 3A and 3B of the optical fibers is set to 0 after the axis alignment step shown in FIG. At this time, the received light power is measured in advance by measuring means provided in the optical fibers 1A and 1B.

As the measuring means, any known means such as a known transmission method or a backscattering method may be employed.

A specific example of the measuring means will be briefly described with reference to FIG.
Connect an appropriate light source 7, such as an LED stabilized light source or LD stabilized light source, to the optical fiber 1B that will be the receiving side.
A photodetector 8 such as a general-purpose optical power meter such as a PD or APD, or a high-sensitivity optical power meter is connected to the output end side of the detector.

Further, the measurement values from the photodetector 8 are inputted to the optical fiber feeding mechanism 10, alignment mechanism 11, etc. via the controller 9, so that these devices 8, 9,
10 and 11 are connected to each other.

When setting the end face distance = 0 in the present invention, the measurement means described above sends an optical signal (light pulse) from the light source 7 to the optical fibers 1A, 1B and the photodetector 8, and the photodetector 8 measures the received light power. To detect.

Next, the operation for setting the end face interval to 0 will be explained.

Optical fiber end 2 as shown in Figure 1C and Figure 2B
When the axes A and 2B are aligned, the maximum received light power due to the axis alignment becomes _P1 in FIG. 4.

After that, when one optical fiber end 2A is moved toward the other optical fiber end 2B, the received light power gradually increases and the distance between the optical fiber end faces 3A and 3B becomes 0 as shown in FIG. At this time, the received light power reaches a peak as shown at _P2 in FIG.

If the optical fiber end 2A is still moved in the above-mentioned direction, the received light power will drop to _P3 in FIG. 4 due to excessive pushing as shown in FIG. 2C.

In this way, by matching the optical fiber ends 2A and 2B over the increasing and decreasing trends of the received light power, the peak P ₂ of the received light power, that is, the end face spacing=0, can be determined.

Next, when the optical fiber end 2A is moved by inching in the opposite direction, that is, in the anti-butting direction, the received light power gradually increases again, and when the end face distance becomes 0, the received light power increases as shown in Fig. 4, P ₄ . (=
P ₂ ), and therefore the movement of the optical fiber end 2A is stopped at this point.

When this _P4 is detected, it can be said that the state apparently returns from the state shown in Figure 2C to the state shown in Figure 2B.

After that, one of the optical fiber ends, for example 3B, is slightly moved in the direction of axis deviation (direction perpendicular to the optical fiber axis).

When there is no change in the received light power greater than the measurement error, it can be said that the optical fiber end faces 3A and 3B are still in strong contact, and the end face distance has not become exactly zero.

In other words, due to the above-mentioned contact state, the optical fiber ends 2A and 2B are interlocked without being axially misaligned, and therefore, it can be said that the received light power does not change.

On the other hand, when the optical fiber end faces 3A and 3B are in contact with each other with almost zero contact pressure, that is, the end face distance =
When the accuracy of 0 is high, the optical fiber ends 2A and 2B are axially deviated from each other due to the above-mentioned axial deviation movement, and the level of the received light power is reduced as shown in FIG. 4, _P5 .

Therefore, after detecting the received light power P ₄ , it is checked whether the received light power P ₅ appears by the above-mentioned axis shift operation, and if there is no change in the received light power, the light is continued until the above-mentioned P ₅ occurs. The fiber end 2A is moved stepwise in the opposite direction.

In this way, after the received light power _P5 is generated, the optical fiber end 2B is moved in the opposite direction to the direction in which the axis deviation was operated in order to correct the axis deviation state, and thereby, as shown in Fig. 4 P ₆ ( =P ₂ =P ₄ ) is obtained,
The optical fiber ends 2A and 2B are returned to their axially aligned state, and the distance between the end faces assumes an accurate zero state due to the above-described operation.

In addition, in the above, the optical fiber end faces 3A, 3B
When relatively moving in the butting direction, anti-butting direction, or in the axis misalignment direction or alignment direction, it is best to move the end part in small steps in a predetermined direction, and by doing this, each operation can be controlled. Sex increases.

In addition, these measured values, such as the received light power of P ₁ to _{P 6} by the photodetector 8, are input to the controller 9, and further, a predetermined control signal is sent from the controller 9 to the mechanism 1.
By inputting 0 to the axis alignment mechanism 11, it becomes possible to automatically set the end face spacing to 0.

Next, programming for automatically setting the end face interval=0 will be explained with reference to FIG.

In numbers 11 and 13 in Figure 5, P represents the maximum received light power that has been read out (the same applies below), New represents the latest received light power (the same applies below), and ld is 1 greater than New. It represents the previous received light power and Power ( ) is x = Power
( ) indicates reading the new received light power and substituting that value into x (the same applies below).

ZF number 12 means to move the optical fiber ends one step at a time toward abutment.

The 21st max(P, New) is between P and New,
Represents a large value.

No. 31 ZR means to move the optical fiber end in the opposite direction one step at a time.

No. 42 X points the end of the optical fiber in the axial direction 10
It means to move by step.

In Fig. 5, when P at No. 11 is the received light power P ₁ in Fig. 4, New is held at P = P ₁ until the next measured value is input, but P at No. 12 is
When ZF starts, the received light power increases as the step moves, so ld is always replaced with the new New as shown in number 13, and P ₂ and P ₃ in Figure 4 are detected as the step moves. It will be carried out until

Since No. 21 picks up the larger value among the sequentially changing measured values, the peak of the received light power at the time of the step movement, that is, _P3 in FIG. 4 is read.

In No. 22, P ₃ read in No. 21 is set as New, and this New is compared with P-0.05d ^B (P is the reference value for checking the measurement error), and New<P-
If 0.05d ^B is not satisfied, it is assumed that the measurement error is large and an N command is issued to perform ZF again.

When New<P-0.05d ^B is satisfied in No. 22, YES is output.

At No. 31, which receives this YES command, one step movement is performed by ZR, and at No. 32, the received light power increased by this step movement is set as New.

Furthermore, in No. 33, it is determined whether New of No. 32 is the peak of the received light power (tolerance error ^0.02dB ), that is, whether New is within the tolerance range of P4 in Figure _4. New≧P− Perform a comparison operation using 0.02d ^B , and if N, repeat ZR until P ₄ is detected, and if YES, input the instruction to number 41.

In number 41, when YES comes out in number 33 above.
In response to New, New is entered in No. 41 at No. 42, and movement in the X, ie, axis deviation direction is performed.

Here, when the distance between the end faces becomes 0 due to step movement No. 42, the mutual axes of the ends of the optical fibers will occur, but in order to confirm this, the following
Perform ZR on the turn.

The received light power, that is, the measured value when moving one step at No. 51, enters No. 52 as New, and the difference between New and ld (peak of received light power) at No. 53 is the measurement error (0.02d ^B ). A comparison operation is performed to determine whether or not the value is greater than or equal to the value.

If this number 53 is N, then number 51 is repeated, and if it is YES, it is assumed that P ₅ in Fig. 4 has occurred, that is, the end face spacing is 0, and the instruction is given to fine centering (axis alignment) to number 61. Send your life.

Based on this, in No. 61, the ends of the optical fibers are aligned with each other, and the alignment is completed when _P6 in FIG. 4 is detected, that is, when the cores of the optical fibers 1A and 1B coincide with each other.

In the case of the present invention, after detecting P ₃ in Fig. 4, the movement of the optical fiber end (in the opposite direction) that should detect P ₄ in Fig. 4 may be omitted, and in this case, the axis misalignment may be omitted. The step movement in the direction and the step movement in the opposite direction are performed alternately, and this is repeated as many times as necessary to detect the above-mentioned P ₃ , P ₄ , etc.

To illustrate this in Figure 5, numbers 31 to 33 in the same figure
By omitting the step numbers 51 to 53, the program is programmed so that the step movements numbered 51 to 53 precede, and the step movements numbered 41 and 42 follow, and both of these step movements are repeated as many times as necessary.

All of the values mentioned in FIG. 5 can be changed.

(Effects) As explained above, when using the method of the present invention,
Each predetermined operation is performed while the optical fibers are passing through each other. First, when the end surfaces of a pair of optical fibers are brought into contact with each other, the ends of the optical fibers are kept in contact with each other until the maximum light reception level shows a decreasing tendency. Since the butt movement is performed, it is possible to accurately grasp the peak of the received light power that should be used as a reference for the end face spacing = 0. After that, when setting the end face spacing = 0, the optical fiber end is relatively moved in the opposite direction. In addition to the relative movement in the axis misalignment direction, the end face interval = 0 can be set reliably and accurately, and only the axis alignment operation is required.

Therefore, it becomes possible to accurately set the end face spacing >0 when fusion splicing optical fibers to each other, and it becomes possible to achieve low-loss fusion splicing of optical fibers.

In addition, by inputting the measured values of the received light power during each of the above operations to a predetermined control system, the end face spacing = 0
You can easily automate the settings.

[Brief explanation of the drawing]

Figures 1 to 1 are explanatory diagrams of the process of the optical fiber fusion splicing method on which the method of the present invention is based; Figure 3 is a schematic diagram of the measuring means in the method of the present invention, Figure 4 is an explanatory diagram showing the measured value of the received light power in the method of the present invention, and Figure 5 is a flowchart showing programming when automating the method of the present invention. It's a chat. 1A, 1B... optical fiber, 2A, 2B... end of optical fiber, 3A, 3B... end face of optical fiber, 6... matching liquid, 7... light source, 8... photodetector.

Claims (1)

[Claims] After the ends of a pair of optical fibers are made to face each other, the axes of these optical fiber ends are aligned, the distance between the optical fiber end faces is set, the optical fiber ends are moved to butt each other, and the optical fiber ends are moved. In the method of fusion splicing the ends of the optical fibers forming the pair by a necessary process such as applying discharge heat to relatively moving the end portions of the optical fibers in the abutting direction, detecting a tendency of the maximum received light power to decrease by measurement on the receiving side optical fiber, and stopping the abutting movement of the optical fiber end portions at the time of the detection, After the end surfaces of the optical fibers are brought into contact with each other, the ends of the optical fibers are relatively moved in the opposite direction while the received light power is being detected, and the ends of the optical fibers are moved in the direction of misalignment. The operation of moving the optical fibers relative to each other is performed at least once in any order, thereby creating a state in which the distance between the end faces of the optical fibers becomes 0 and a state in which the ends of the optical fibers are misaligned with each other. A method for setting the spacing between optical fiber end faces in an optical fiber fusion splicing method in which optical fiber ends are aligned with each other. 2. Optical fiber end face spacing in the optical fiber fusion splicing method according to claim 1, in which a matching liquid is applied to the end faces of the optical fibers when the ends of the pair of optical fibers are relatively moved in the abutment direction. Setting method.