JPH0534646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fiber splicing device that can align the core axis of an optical fiber having an eccentric core without monitoring the optical power and guarantees low splicing loss. be.

In order to reduce the loss when connecting fibers (optical fibers) with small core diameters, such as single mode fibers, it is necessary to reduce the misalignment (axis misalignment) between the core centers of the two fibers to be connected. It is necessary to minimize this, and this is called core alignment.

The core axis alignment method using a conventional connecting device is to fix one side 1 of the fibers to be connected to a fixing base 3 as shown in Fig. 1, and fix the other fiber 2 to the , z, and is fixed to a fixed base 4 that can be moved slightly in each direction. Then, the output light from the light source 5 is input to the fiber 1, the power of the light passing through the fibers 1 and 2 and arriving at the light receiver 6 is monitored, and the fixing base 4 is moved so that this power becomes maximum. The axis is being aligned. However, with this method, the location where the light enters, the location where it is connected, and the location where the light is monitored are different, so devices to communicate with each other are required, and workers need to be stationed at each location. In particular, it is very inconvenient to work when the light source location, monitor location, and connection location are separated by several kilometers.

In addition, when connecting in the middle of a transmission line that includes multiple repeaters, it is not possible to input monitoring light into the fiber because there are repeaters on both sides, and even if all repeaters are in operation, Even if the transmitted light was monitored using the repeater, the AGC (automatic gain adjustment) function of the repeater was activated, and the power received at the receiving point did not necessarily provide information on axis misalignment, and high voltage power was applied during the work. Because it is dangerous to do this in close proximity, the method of aligning the axis by essentially monitoring the power of the light has the drawback of being difficult to apply.

The present invention provides a fiber splicing device that eliminates the above-mentioned drawbacks, in which two fibers to be spliced are held on a fiber fixing base, and light is irradiated from a direction perpendicular to the axis of the fibers, and the core of the fibers is By observing the core with a microscope and moving the fiber fixing table, the core can be directly observed and aligned, and the core can be aligned automatically and with high precision. It is characterized by the fact that

Embodiments of the present invention will be described below, but first, FIGS.
This will be explained with reference to the figures.

FIG. 2 is a diagram showing a schematic configuration of the basic device, and in this diagram, the means for fixing the fibers 1 and 2 are the same as those shown in FIG. 1. In this device, in order to observe the core of the fiber from the x-axis and y-axis directions, light sources 11 and 12 for illumination are placed on axes (x-axis, y-axis) perpendicular to the axis (z-axis) of the fiber. A microscope 31 having an objective lens 13 and an eyepiece 14 is placed opposite the light sources 11 and 12 across the fiber.

When the fiber is observed in the state of transmitted light using the above-mentioned apparatus, the outer boundary 16 of the fiber and the boundary 17 of the core as shown in FIG. 3 can be distinguished because the core has a slightly higher refractive index in the fiber.
Therefore, the center position 1 of the core of both fibers
The core axes can be aligned by moving the fixing base 4 in the required directions about the x-axis and the y-axis, respectively, so that the core axes 8 and 19 are aligned.

Figures 4a and 4b show another example of the fiber observation system in this device, in which a mirror 21 is used to bend the transmitted light in the y-axis direction at right angles so that it can be seen with a single microscope. This is what I did.

Figure 5 is another example of the fiber observation system in this device, and by using a mirror 22 with a wedge-shaped depression in the middle, two orthogonal fiber images can be observed in the same microscope as in Figure 4. The difference from Figure 4 is x
Optical path length from fiber to microscope in axial and y-axis directions
₁ and ₂ are equal, and images can be observed within the same field of view and at the same focus.

FIG. 6 shows a schematic configuration of another device that is the basis of the present invention. This device adds an imaging device 32, an image processing device 33, and a moving device 34 to the device shown in FIG. The configuration is such that alignment can be performed automatically. That is, the apparatus shown in this figure is the microscope 3 in the apparatus shown in FIG.
The image obtained in step 1 is converted into a signal by the imaging device 32, the center position of the core is detected from the signal V by the image processing device 33, the deviation of each axis of the connected fibers 1 and 2 is determined, and the deviation is dealt with. The amount Δ is transmitted to a starter device 34 that moves the fiber fixing table 4, and the moving device 34 moves the fiber fixing table 4 by Δ. According to this device, axis alignment can be performed automatically.

When a video camera, for example, is used as the imaging device 32, a light intensity signal is given as an image signal V, and this signal is a-a' with respect to the fiber axis, as shown in FIG. When scanning in the perpendicular direction as shown in FIG. 7, a signal of the form shown in FIG. 7b is obtained. Here, the boundary of the drop to the black level at 36 and 37 indicates the outer diameter of the fiber, and the core boundary is also observed as a drop like 38 and 39, so the core center position 40 can be detected.

In addition, in this device, by setting the scanning direction of the imaging device 32 in the axial direction of the fiber, it is also possible to determine the end face spacing of the fibers to be connected, and by slightly moving the fixed base 4 in the z-axis direction, the end face spacing can be determined. It is also possible to automatically adjust the value to the optimum value.

The optimum value for the end face spacing is usually around 10μm, but
Conventionally, adjustments were made visually through a microscope, which was a factor in the dispersion of loss after connection, but by constantly adjusting to the optimum value with this device, one of the causes of such dispersion in loss could be eliminated. is possible.

By the way, sometimes the core is eccentric within the fiber (that is, the center of the fiber does not match the center of the core), and the alignment of such eccentric fibers is shown in Figures 2 and 6 above. It was found that when using the apparatus shown in Figure 1, the center position of the core was observed to be shifted from its actual position due to the lens effect of the cladding part of the fiber.
For this reason, it has been found that the above-mentioned apparatus cannot necessarily perform highly accurate axis alignment of the core. This will be explained with reference to FIG.

As shown in Fig. 8, the eccentricity of the actual core center position with respect to the fiber center is d ₁ , and the observed eccentricity of the core center position with respect to the fiber center is d ₂
Then, the deviation D between the observed center position of the core and the actual core center position is D=d ₂ - d ₁ ≒ (n-1) d ₁ = where n is the refractive index of the cladding part. It is given by n-1/nd ₂ ...(1). When the two fibers are aligned, the deviation between the actual center position and the observed center position remains as an axis deviation, depending on the positional relationship of the eccentricities of the fibers to be connected. For example, if the eccentricity of two fibers is 2% and they are relatively eccentric in opposite directions with respect to the fiber center, the alignment error is 0.8 μm, and the resulting misalignment loss exceeds 0.1 dB. It turns out. Therefore,
Observed deviation between the center of the core and the center of the fiber
Considering that the actual core center deviates from d ₂ by the amount given by equation (1), find the positional deviations D ₁ and D ₂ for each of the connected fibers, and calculate only the difference D ₁ − _{D 2} It is necessary to move the fixed base 4 and correct the shift.

The present invention has been made in consideration of the above points, and is capable of calculating the true eccentricity value of the core even when the core is eccentric within the fiber, thereby achieving highly accurate alignment of the core axis. It has been made possible to do so. Hereinafter, the operation of the present invention will be explained with reference to FIG. 8b, and one embodiment of the present invention will be explained with reference to FIG. 9.

The device of this embodiment shown in FIG. 9 is the basic device shown in FIG. 6 with the addition of an eccentricity correction device 41 for correcting the positional deviation of the core of the eccentric fiber. This eccentricity correction device 41 is
Observation error Δ′= from the amount of eccentricity within the core fiber
The purpose is to find D ₁ − _{D 2} . In the apparatus of this embodiment, the truly necessary movement is determined from the value of Δ' obtained by the eccentricity correction device 41 and the value of the signal Δ corresponding to the deviation of the core axis output from the image processing device 33. The amount Δ-Δ' is determined, and the moving device 34 is driven based on the output, thereby accurately aligning the cores.

According to the device of this embodiment, the center position of the core is determined by directly observing the core, and the movement amount of the fixing table is corrected based on the eccentricity of the core.
Even when connecting eccentric fibers, the center positions of the cores can be matched with high precision.

On the other hand, it is well known that connection loss can usually be reduced if connections are made with the axis aligned with high precision.

However, connection loss may increase due to minute defects in the state of the end faces of the fibers to be connected before connection, poor end face spacing, etc.

Although these losses could be directly known from the amount of power using the connection method that performs power monitoring, they cannot be directly known using the present invention that observes the core.

Therefore, it is necessary to determine whether the connection loss satisfies the connection loss standard for the system.

FIG. 10 shows another embodiment of the present invention, and based on the above points, the device of the embodiment shown in FIG. Processing device 51 and display device 52
is added. The pass/fail processing device 51 includes an image processing device 33 for core position detection and an eccentricity correction device 4 for correcting observation errors due to core eccentricity.
From the information on the core position obtained in step 1, determine the amount of axis deviation, angular deviation, amount of bending, etc. near the connection point, estimate the connection loss from these quantities, and the estimated value is determined by the standard value of connection loss. It determines whether specific pass/fail criteria are met.
The determination result is output to the display device 52 mentioned above.

According to the device of this embodiment, in addition to the effects achieved by the device of the embodiment shown in FIG. 9, it is also possible to automatically determine whether the connection state is good or bad.

The embodiments of the present invention have been described above, but an image processing device for extracting the distance between the end faces of the two fibers to be connected is added to the apparatuses of both of the above embodiments, and the scanning direction of the imaging device 32 is adjusted. The distance between the end faces of the fibers to be connected is determined in the axial direction of the fiber (z-axis direction) using the attached image processing device, and the distance between the fiber end faces is set to the optimum value based on the obtained end face distance signal. It is also possible to configure the fixing base to move slightly in the z-axis direction. By doing so, it is possible to reduce variations in loss after connection due to improper end face spacing.

As explained above, according to the present invention, the core inside the fiber to be connected is directly observed using a transmitted light source, and the fixing base that holds the fiber to be connected is operated based on this observation. In addition, in order to correct the observation error of the core position due to the lens effect of the cladding part, the true eccentricity value of the core is determined by the eccentricity correction device and the fixing table is moved. Since the structure is configured to correct the amount, even if the fiber is eccentric, the core axis can be aligned with high precision.

In addition, by adding a pass/fail processing device and a display device, it is possible to estimate splicing loss by evaluating axis misalignment, angular misalignment, bending, etc. near the connection point based on the state of the core after connection, and make pass/fail judgments. can be done automatically. Furthermore, by adding an image processing device that extracts the distance between the end faces of the fibers to be connected, it becomes possible to automatically adjust the end face distance.

By applying a connection device including a series of alignment and inspection mechanisms to the connection of single-mode fibers, a power monitor is not required, and it can be applied to connections between fibers where power cannot be inserted into the fibers. This has the advantage that the work only needs to be done at the connection point, which greatly simplifies the connection work.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a conventional single mode fiber connection device, and FIGS. 2 to 8 are diagrams for explaining the basic device of the present invention, and FIG. 2 is a schematic diagram of the device. The configuration diagram, Figure 3 is a contour diagram of each part of the fiber showing the results of observing the fiber with the device, and Figures 4a, b, and 5 are the different types of fiber observation systems of the basic device. FIG. 6 is a schematic configuration diagram of another device that is the basis of the present invention, FIG. 7a is a diagram showing the direction in which the fiber is observed by the device, and FIG. Figure 8a is an explanatory diagram showing the positional relationship of each part of the fiber when the fiber is eccentric, and Figure 8b is an explanatory diagram showing the axis alignment of two eccentric fibers. be. FIGS. 9 and 10 are schematic configuration diagrams showing embodiments of the present invention, respectively. 1, 2... Fiber to be connected, 3, 4... Fiber fixing stand, 11, 12... Light source, 21, 22...
Mirror, 31...Microscope, 32...Imaging device, 3
3...Image processing device, 34...Movement device, 41...
...Eccentricity correction device, 51... Pass/fail processing device, 52...
...display device.

Claims (1)

[Claims] 1. A fixing base that holds the ends of two fibers to be connected having eccentric cores in a straight line so that these fiber ends can be moved relative to each other; A light source that shines light onto the fiber from a direction perpendicular to its axis, a microscope for observing the core placed opposite the light source across the fiber, and an image of the fiber obtained by the microscope. an image processing device that extracts the observed core center position for each of the two fibers based on the core boundary of the imaged screen obtained by this imaging device; an eccentricity correction device that determines the deviation between the observed core center and the actual core center for each of the two fibers based on the deviation between the core center and the fiber center, and calculates an observation error of the difference;
a moving device that moves the fixed base based on an output signal of the difference between the core center deviation between the two fibers observed by the image processing device and the observation error, and A fiber connecting device characterized in that the fixing base is operated to align the core axes of the fibers based on a true eccentricity value obtained by a correcting device, thereby achieving axial alignment. 2 Extract the core positions of the two connected fibers from the image capture screen near the connection point of the fibers after connection, estimate the splice loss at the connection point from the axis misalignment, angular misalignment, and bending of the cores, and calculate the splice loss according to the splice loss standard. The fiber connection device according to claim 1, further comprising a pass/fail processing device for determining pass/fail, and a display device for displaying the pass/fail judgment based on the output of the pass/fail processing device. 3. Add an image processing device that extracts the distance between the end faces of two fibers to be connected from the imaging screen, and adjust the distance between the fiber end faces to an appropriate end face distance based on the end face distance signal obtained by this image processing device. 3. The fiber connecting device according to claim 1, wherein the fiber connecting device is configured to operate a fixed base.