JP2001083362A - Method for connecting multiple fiber array and waveguide element and its connecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for connecting a multiple fiber array and a waveguide element capable of reducing a deviation of a connection loss. SOLUTION: When a multiple fiber array 5 having a large number of optical fibers is connected to a waveguide element 2 having a large number of waveguides, the positions of the multiple fiber array where the connection loss with a waveguide corresponding to at least three optical fibers of the multiple fiber array 5 becomes minimum are respectively obtained as a coordinate point by moving the abutting position between the multiple array 5 and the waveguide element 2. The optimal coordinate point wherein the deviation of the connection loss becomes small is derived from at least these three coordinate points, and the multiple fiber array is connected to the waveguide element by being positioned to the optimal coordinate point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for connecting a multi-core fiber array for signal transmission and a waveguide type optical component (waveguide element), and in particular, to reduce the deviation of connection loss. The present invention relates to a method for connecting a multi-core fiber array to a waveguide element and a connection device therefor.

[0002]

2. Description of the Related Art With the practical use of optical communication systems, there is a strong demand for higher performance and lower cost of optical components used for optical communication. Against this background, waveguide type optical components have been actively developed. Waveguide optical components can form optical circuits having various functions on a substrate and are relatively easily mass-produced. Therefore, they are being put to practical use as high-performance, low-cost optical communication components.

In general, a waveguide-type optical component requires a connection between a waveguide and an optical fiber which is a transmission medium for communication signals. Several methods have been studied for the connection between the waveguide and the optical fiber.Among them, a butt coupling (a butt coupling that connects an optical fiber array in which optical fibers are arranged on a substrate and a waveguide element by abutting each other) is used. Butt coupling) method is widely used.

[0004] The procedure of the butt coupling method removes the terminal coating of the optical fiber. An optical fiber is made to extend along a V-groove block having a V-groove formed on a substrate. An adhesive is applied and fixed with a holding plate. The end face of the optical fiber array is ground or polished. Through the above steps, an optical fiber array is created. A reinforcing block is fixed to the waveguide with an adhesive. The end face of the waveguide element is ground or polished. The waveguide element and the optical fiber array are butted and aligned. An adhesive is applied to the connection between the end face of the waveguide and the end face of the optical fiber array, and the adhesive is cured. Through the above steps, the waveguide type optical component and the optical fiber array are integrally assembled.

In connection between a waveguide and an optical fiber, it is important to minimize connection loss at a connection portion. In the connection between a multi-core optical fiber array having a large number of optical fibers and a waveguide element having a large number of waveguides, each port (ports are numbered optical fibers and waveguides corresponding to each other). Since connection loss occurs in each case, it is desirable that variation in connection loss of the entire port be small.

One of the main causes of the connection loss is a shift of the optical axis at the connection portion. In a single mode, when the mode field diameters of the waveguide and the optical fiber match, α = −1010 g10 [exp− (d / ω) ² ] (α: connection Loss, d: optical axis shift amount, ω: mode field radius) When the mode field radius is 5 μm, α = about 1.7d
² (dB). As described above, in the connection between the waveguide and the optical fiber, the deviation of the optical axis greatly affects the connection loss.

In the multi-core connection between the optical fiber array and the waveguide element, the deviation of the connection loss between the ports increases unless the optical axis deviation is reduced in all the ports (the dispersion of the connection loss of the entire port is large). Problem).

In the conventional connection method, as shown in FIG. 6, the multi-core fiber array is moved in the X and Y directions of the bonding surface, and the two light beams at both ends of the multi-core fiber array with respect to the two ports at both ends of the waveguide element. After the fiber alignment is performed and the rotation is adjusted so that the connection loss at both ports is reduced, the coordinate points (X1, Y1) (X2, Y2) at which the connection loss is minimized for each port.
By moving the multi-core fiber array to the middle point (Xa, Ya) of these two points, the deviation of the total connection loss is reduced.

[0009]

However, in the conventional connection method, when the waveguide element or the multi-core fiber array is warped, the deviation of the connection loss sometimes becomes large. The warpage of the waveguide element or the multi-core fiber array may be caused by a warp existing on a substrate such as quartz glass or Si used for the waveguide element or the multi-core fiber array, or a warp due to heating during manufacturing. It is difficult to eliminate the warpage because it is necessary to control a minute change in shape to eliminate the warpage. As described above, since the warpage is inevitable, the conventional connection method has a large connection loss deviation due to the influence of the warp or the like.

FIG. 7 shows connection loss of each port connected by a conventional connection method. In this example, the warpage of the element is 3 μm. While monitoring the optical output at the ports at both ends, the coordinates of the position of the multi-core fiber array at which the optical output becomes maximum were obtained, and the connection method of moving the multi-core fiber array to the middle point of the two coordinates was used. When the connection is performed in this manner, if the waveguide element or the multi-core fiber array is warped as in this example, the connection loss increases according to the shape of the waveguide element or the multi-core fiber array. However, it occurs. Therefore, the deviation of the connection loss increases.

To reduce the deviation of the connection loss, there is a method of adjusting the positioning in the connection. However, it is necessary to adjust the positioning in consideration of the shapes of the waveguide element and the multi-core fiber array, which is very complicated. It takes time.

As described above, in the conventional connection method, the deviation of the connection loss increases as the shape of the waveguide element or the multi-core fiber array changes, such as warpage. Further, the adjustment for correcting the deviation of the connection loss is very complicated and time-consuming.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for connecting a multi-core fiber array to a waveguide element, which can solve the above-mentioned problems and can reduce the deviation of connection loss.

[0014]

In order to achieve the above object, a method of the present invention is used for connecting a multi-core fiber array having a large number of optical fibers to a waveguide element having a large number of waveguides. By moving the abutting position between the core fiber array and the waveguide element, the position of the multi-core fiber array at which the connection loss with the corresponding waveguide is minimized for at least three optical fibers in the multi-core fiber array is set as a coordinate point. Are derived from these at least three coordinate points to derive an optimal coordinate point at which the deviation of the connection loss is reduced, and connect the multi-core fiber array to the waveguide element by adjusting the position to the optimal coordinate point.

[0015] Of the at least three optical fibers,
For the two optical fibers near both ends of the multi-core fiber array, the minimum connection loss coordinate point is determined, and
For the optical fiber between the two optical fibers, a coordinate point with the minimum connection loss may be obtained, and the center of gravity of at least three coordinate points may be set as the optimal coordinate point.

[0016] Of the at least three optical fibers,
Finding the minimum connection loss coordinate point for the two optical fibers near both ends of the multi-core fiber array, finding the minimum connection loss coordinate point for the optical fiber between the two optical fibers, The optimum coordinate point may be a midpoint between a midpoint of a line segment connecting them and a straight line passing through another coordinate point and parallel to the line segment.

Further, according to the present invention, there is provided an apparatus for connecting a multi-core fiber array having a large number of optical fibers to a waveguide element having a large number of waveguides. Alignment stage for adjusting the abutting position of the alignment stage and the waveguide element, movement amount detection means for detecting the movement amount of the alignment stage, and the multi-core fiber array position represented by coordinate points based on the movement amount, at least 3 points. Calculation means for deriving another coordinate point for moving the multi-core fiber array from one coordinate point.

[0018] The moving amount detecting means may be constituted by a laser measuring device facing the alignment stage.

[0019]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

According to the connection method of the present invention, while monitoring the optical output of the port, the multi-core fiber array is moved in the XY biaxial directions (X; horizontal, Y; vertical) of the joint surface and abuts the waveguide element. For each of the at least three ports, a multi-core fiber array position at which the connection loss is minimized is determined by using XY coordinates, and an optimum coordinate point at which the deviation of the connection loss is reduced is derived from the at least three coordinate points. By connecting the multi-core fiber array to the waveguide element while adjusting the position to the optimum coordinate point, the deviation of the connection loss between the ports is reduced.

As a specific method for deriving the optimum coordinate point, as shown in FIG. 1, first, as shown in FIG. 1, two optical fibers (near both ends of a waveguide element) near both ends of a multi-core fiber array are used. , The coordinate points (X1, Y1) and (X2, Y2) at which the connection loss is minimized. Rotation adjustment is performed around the center of these two coordinate points around the center of rotation, and then the coordinate points at which the connection loss is minimized for 1 to n (n is a natural number) optical fibers between the two optical fibers. (X3, Y3) is obtained. Assuming a polygon A connecting at least three coordinate points consisting of the two coordinate points obtained first and the coordinate points 1 to n obtained later, the center of gravity (Xb, Yb) of the polygon A is determined as the optimum coordinate point. And

In the second method, as shown in FIG. 2, first, the connection loss of two optical fibers near both ends of a multi-core fiber array (two waveguides near both ends of a waveguide element) is reduced. Coordinate points (X1, Y1), (X2, Y
2) is obtained respectively. Rotation adjustment is performed around the center of these two coordinate points around the center, and then the coordinate points (X3, Y3) at which the connection loss is minimized for 1 to n optical fibers between the two optical fibers. Ask for. A line segment B connecting the two coordinate points obtained first is assumed, and a straight line C passing through the coordinate points 1 to n obtained later and parallel to the line segment B is assumed. An intermediate point (Xc, Yc) between the middle point of the line segment B and the parallel straight line C is defined as an optimum coordinate point.

[0023] The connection device for performing the first and second methods is as follows.
As shown in FIG. 3, a fixed stage 3 which is installed on the horizontal base 1 and fixes the waveguide element 2 and moves on the horizontal base 1 while holding the single-core or multi-core fiber arrays 4 and 5. Alignment stages 6 and 7, moving amount detecting means such as laser length measuring devices 8 and 9 for detecting the amount of movement of the aligning stages 6 and 7, and arithmetic means (not shown).

The alignment stages 6 and 7 are arranged on both sides in the longitudinal direction of the fixed stage 3, that is, on both the left and right sides in the figure. In the example of FIG. 3, the left side of the waveguide element 2 is a single-core fiber array (optical fiber) 4. The connection is made, and the right side is connected to the multi-core fiber array 5. The alignment stages 6 and 7 are X,
An orthogonal movement stage that moves in three orthogonal axes, Y and Z, and a rotational movement stage that rotates about each axis, θx, θy, and θz, are provided. The laser length measuring device 8 is for the X axis, and the laser length measuring device 9 is for the Y axis.

A detailed connection method according to the first method will be described with reference to FIG.

First, the multi-core fiber array 5 is set to θx, θ
After adjusting the angle of the abutting surface by rotating each axis of y and θz, monitor light is input to the waveguide element 2 or the single-core fiber array 4, and light from each port of the multi-core fiber array 5 is input. While monitoring the output, the multi-core fiber array is moved in the X-axis and Y-axis directions to perform alignment. That is, first, the multi-core fiber array 5 is moved to a position where the optical output is maximized (the connection loss is minimized) in order to align one end port, and the coordinate points of the multi-core fiber array 5 are stored. Next, in order to adjust the center of the port at the opposite end, the multi-core fiber array 5 is located at the position where the optical output is maximized.
Is moved, and the coordinate points of the multi-core fiber array 5 are stored. The rotation direction θ is defined around the center of these two points as the rotation center.
z, and the angle is adjusted so that the connection loss is reduced at both points. Further, the multi-core fiber array 5 is connected to the X-axis and Y-axis.
By moving in the axial direction, the coordinate points (X1, Y1), (X2, Y
2) is obtained and stored. Thereafter, the multi-core fiber array 5 is moved to the midpoint between these two coordinate points. In this state, connection loss is measured for all ports. From the connection loss measurement results of all the ports, a port near the center where the connection loss is larger than the other ports is selected, and the multi-core fiber array 5 is moved along the X-axis so that the optical output of that port is maximized. And moving in the Y-axis direction to align the coordinate points (X3,
Y3) is stored. The center of gravity (Xb, Yb) of the three coordinate points (X1, Y1), (X2, Y2), and (X3, Y3) stored in this manner is obtained. This center of gravity (Xb, Yb)
The multi-core fiber array 5 is moved to and connected.

FIG. 4 shows the connection loss characteristics of the ports in the multi-core fiber array 5 and the waveguide element 2 connected by the above method. The black dots indicate the connection loss of each port according to the present invention. As shown in the figure, the connection loss deviation defined by the difference between the maximum value and the minimum value of the connection loss is 0.4 dB, which is smaller than the conventional connection loss deviation of 1.0 dB. .

Next, a detailed connection method according to the second method will be described with reference to FIG.

First, the multi-core fiber array 5 is set to θx, θ
After adjusting the angle of the abutting surface by rotating each axis of y and θz, monitor light is input to the waveguide element 2 or the single-core fiber array 4, and light from each port of the multi-core fiber array 5 is input. Alignment is performed by moving the multi-core fiber array while monitoring the output. That is, first, the multi-core fiber array 5 is moved to a position where the optical output is maximized (the connection loss is minimized) in order to align the one end port, and the coordinate points of the multi-core fiber array 5 are stored. next,
The multi-core fiber array 5 is moved to a position where the optical output is maximized in order to align the ports at the opposite ends, and the coordinate points of the multi-core fiber array 5 are stored. The two points are rotated in the rotation direction θz around the center of the two points, and the angle is adjusted so that the connection loss at both points is reduced. Further, the multi-core fiber array 5 is moved in the X-axis and Y-axis directions, and the coordinate points (X1, Y1) and (X2, Y2) at which the optical output is maximized for the ports at both ends are obtained and stored. A line segment B connecting these two coordinate points is calculated and stored. Thereafter, the multi-core fiber array 5 is moved to the midpoint between these two coordinate points. In this state, connection loss is measured for all ports. From the connection loss measurement results for all ports, a port near the center where the connection loss is larger than the other ports is selected, and the multi-core fiber array 5 is moved along the X-axis so that the optical output of that port is maximized. Then, it is moved in the Y-axis direction and aligned, and the coordinate points (X3, Y3) are stored. A straight line C passing through the coordinate points (X3, Y3) and parallel to the line segment B is obtained. An intermediate point (Xc, Y) between the midpoint of the line segment B and the parallel straight line C
Find c). The multi-core fiber array 5 is moved to the intermediate point (Xc, Yc) and connected.

FIG. 5 shows connection loss characteristics between the multi-core fiber array 5 and the waveguide element 2 connected by the above method. The black dots indicate the connection loss of each port according to the present invention.
As shown in the figure, the connection loss deviation defined by the difference between the maximum value and the minimum value of the connection loss is 0.25 dB, which is smaller than the conventional connection loss deviation of 1.0 dB. .

As described above, the present invention derives the optimum tangent coordinate point from at least three coordinate points having the minimum connection loss, so that the connection loss deviation can be reduced and the X-axis and Y-axis coordinates can be reduced. Since the movement amount is measured by the laser length measuring device, the coordinate point measurement can be performed accurately and with good reproducibility, and the alignment accuracy is improved. As a result of repeatedly performing the alignment connection according to the method of the present invention in the apparatus of the present invention, the fluctuation of the connection loss deviation is:
Conventional connection loss deviation variation of the same sample ± 0.2 dB
To ± 0.05 dB or less.

[0032]

The present invention exhibits the following excellent effects.

(1) Even if the waveguide element or the multi-core fiber array is warped, the connection loss deviation can be reduced.

(2) Since the amount of movement is detected by the laser length measuring device, connection can be made accurately and with good reproducibility.

[Brief description of the drawings]

FIG. 1 is a coordinate diagram showing a first method of the present invention.

FIG. 2 is a coordinate diagram showing a second method of the present invention.

FIG. 3 is a perspective view showing a connection device of the present invention.

FIG. 4 is a connection loss characteristic diagram when connection is performed by the method of the present invention.

FIG. 5 is a connection loss characteristic diagram when connection is performed by the method of the present invention.

FIG. 6 is a coordinate diagram showing a conventional method.

FIG. 7 is a connection loss characteristic diagram when connection is performed by a conventional method.

[Explanation of symbols]

 2 Waveguide element 3 Fixed stage 5 Multi-core fiber array 7 Alignment stage 8, 9 Laser length measuring device (movement amount detecting means)

Claims (5)

[Claims] When a multi-core fiber array having a large number of optical fibers is connected to a waveguide element having a large number of waveguides, a position at which the multi-core fiber array and the waveguide element are abutted is moved. The position of the multi-core fiber array where the connection loss with the corresponding waveguide for at least three optical fibers in the multi-core fiber array is minimized is determined as a coordinate point, and the deviation of the connection loss from these at least three coordinate points is small. A method for connecting a multi-core fiber array to a waveguide element, which derives an optimal coordinate point and connects the multi-core fiber array to the waveguide element by adjusting the position to the optimum coordinate point. 2. A coordinate point at which the connection loss is minimized for two optical fibers near both ends of a multi-core fiber array among the at least three optical fibers, and a light beam between the two optical fibers is determined. 2. The method of connecting a multi-core fiber array to a waveguide element according to claim 1, wherein a coordinate point at which the connection loss is minimized for the fiber is determined, and a center of gravity of the at least three coordinate points is set as the optimum coordinate point. 3. An optical fiber between the two optical fibers, wherein a coordinate point of the minimum connection loss is determined for two optical fibers near both ends of a multi-core fiber array among the at least three optical fibers. Determining a coordinate point having the minimum connection loss, and setting an intermediate point between a midpoint of a line segment connecting the two coordinate points and a straight line passing through the other coordinate points and parallel to the line segment as the optimal coordinate point. The method for connecting a multi-core fiber array and a waveguide element according to claim 1, wherein: 4. An apparatus for connecting a multi-core fiber array having a large number of optical fibers to a waveguide element having a large number of waveguides, wherein the multi-core fiber array is moved so that the multi-core fiber array is connected to the waveguide element. Alignment stage for adjusting the butting position, movement amount detection means for detecting the amount of movement of the alignment stage, and the multi-core fiber array position represented by coordinate points based on the movement amount, and multi-core fiber positions from at least three coordinate points. A connection device between a multi-core fiber array and a waveguide element, comprising: a calculation unit for guiding another coordinate point for moving the fiber array. 5. The connecting device according to claim 4, wherein said moving amount detecting means is constituted by a laser length measuring device facing said alignment stage.