JPH09203815A - Positioning method for polarization maintaining optical fiber and polarization maintaining optical fiber array - Google Patents

Abstract

(57) Abstract: It is possible to easily align the direction connecting two stress applying portions of a polarization maintaining optical fiber with a predetermined direction. SOLUTION: A cylindrical ferrule 6 having a flat portion 6a on a part of the outer circumference of the cylinder is fixed in a direction in which two stress applying portions 5c of the polarization maintaining optical fiber 5 are connected and the flat portion 6a of the ferrule 6 is constant. Is fixed to the end of the polarization-maintaining optical fiber 5 such that the ferrule 6 is rotated or rolled on the flat member, and the ferrule 6 is rotated.
The two stress applying portions 5 of each polarization-maintaining optical fiber 5 are obtained by aligning the flat portion 6a of the above with the flat portion of the flat member.
A method for aligning a polarization-maintaining optical fiber, characterized in that the directions connecting c and 5c are aligned in a fixed direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a polarization-maintaining optical fiber array in which the two stress applying portions of a polarization-maintaining optical fiber used in optical fiber communication are aligned in a fixed direction. The present invention relates to a polarization-maintaining optical fiber alignment method and a polarization-maintaining optical fiber array in which the directions connecting the two stress applying portions of each polarization-maintaining optical fiber are aligned in a fixed direction.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional two-dimensional optical fiber array A.
1 is an optical fiber, 2 is a ferrule attached to the end of the optical fiber 1, 3a is an inner side in which the ferrules 2 attached to the end of a large number of optical fibers 1 are aligned and incorporated. Frame plates 3b are outer frame plates provided on the outer side of the inner frame plate 3a, and 4 is an adhesive that bonds the ferrules 2 together. The two-dimensional optical fiber array A has a simple structure in which the ferrules 2 mounted on the ends of the optical fiber 1 are in contact with each other vertically and horizontally. There are no manufacturing problems with the optical fiber array.

[0003]

The polarization-maintaining optical fiber 5 shown in FIG. 1 has a core (for example, GeO ₂ -doped silica glass) 5b at the center of a clad (for example, silica glass) 5a, which is symmetrical on both sides thereof. There are stress applying portions (for example, B ₂ O ₃ -doped quartz glass) 5c and 5c one at each position. The polarization plane of light of the polarization-maintaining optical fiber 5 is held in the direction connecting the two stress applying portions 5c, 5c or in the direction perpendicular thereto.

When a two-dimensional polarization-maintaining optical fiber array is manufactured by using such a polarization-maintaining optical fiber 5, the manufacturing situation is different from that of the above-mentioned optical fiber. That is, in the production of a one-dimensional polarization-maintaining optical fiber array in which a plurality of polarization-maintaining optical fibers 5 are arranged on one plane or a two-dimensional polarization-maintaining optical fiber array in which a plurality of polarization-maintaining optical fibers 5 are further laminated, Must be aligned in a certain direction, that is, in the direction in which the stress applying portions are connected to each other in a predetermined direction. The arrangement of the stress applying portions in the connecting direction cannot be judged from the appearance of the polarization maintaining optical fiber except by directly observing the end face of the polarization maintaining optical fiber.

Therefore, in manufacturing a two-dimensional polarization-maintaining optical fiber array, while observing the end face of the polarization-maintaining optical fiber directly through a television (TV) monitor or the like, the direction in which the stress applying portions are connected is a predetermined direction. In order to align all the polarization-maintaining optical fibers with each other, the positioning was manually adjusted one by one.
Moreover, the array spacing of the polarization maintaining optical fibers is 0.25 mm.
Alternatively, when the width is as narrow as 0.5 mm, the polarization maintaining optical fiber, which has already been positioned during the positioning adjustment work, may be touched to disturb the array in which the directions of connecting the stress applying portions are aligned in a certain direction.

Due to such a situation, the production of the two-dimensional polarization-maintaining optical fiber array has to rely on manual work, the production efficiency is low, and automation of the assembling apparatus is difficult. was there. SUMMARY OF THE INVENTION It is an object of the present invention to provide a polarization maintaining optical fiber alignment method and a polarization maintaining optical fiber array that solve the above problems.

[0007]

In order to achieve the above object, the present invention provides a cylindrical ferrule 6 having a flat portion 6a on a part of the outer circumference of a cylinder, and applies two stresses to a polarization maintaining optical fiber 5. The direction connecting the parts 5c, 5c and the ferrule 6
Is fixed to the end portion of the polarization-maintaining optical fiber 5 so that the flat portion 6a of the ferrule 6 has a fixed positional relationship, and then the ferrule 6 is rotated or rolled on the flat member so that the flat portion 6a of the ferrule 6 is Of the polarization maintaining optical fiber 5 by aligning the two stress applying portions 5c, 5c of the respective polarization maintaining optical fibers 5 with each other in a fixed direction. This is a positioning method.

A cylindrical ferrule 6 having two flat portions 6a and 6a 'facing each other in parallel to the outer circumference of the cylinder is connected to the ferrule with a direction connecting the two stress applying portions 5c and 5c of the polarization maintaining optical fiber 5. The flat parts 6a and 6a 'of 6 are fixedly attached to the end of the polarization-maintaining optical fiber 5 so as to have a fixed positional relationship, and then the ferrule 6 is rotated or rolled on the flat member to make the ferrule 6 Flat part 6a of
By combining 6a 'and the flat part of the flat member, the two stress applying parts 5c, 5 of each polarization maintaining optical fiber 5 can be obtained.
This is a method for aligning polarization maintaining optical fibers characterized in that the directions connecting c are aligned in a fixed direction.

Further, the cylindrical ferrule 6 having a flat portion 6a on a part of the outer circumference of the cylinder is connected to the direction in which the two stress applying portions 5c, 5c of the polarization-maintaining optical fiber 5 are connected and the flat portion 6a of the ferrule 6. The polarization-maintaining optical fiber 5 is attached and fixed to the end portion of the polarization-maintaining optical fiber 5 so that a fixed positional relationship is established. A polarization-maintaining optical fiber array is characterized in that a large number of polarization-maintaining optical fibers 5 are assembled by aligning the directions connecting the two stress-applying portions 5c and 5c in a fixed direction.

A cylindrical ferrule 6 having two flat portions 6a, 6a 'facing each other in parallel to the outer circumference of the cylinder is connected to the ferrule in the direction connecting the two stress applying portions 5c, 5c of the polarization maintaining optical fiber 5. The flat parts 6a and 6a 'of 6 are mounted and fixed to the ends of the polarization maintaining optical fiber 5 so that the flat parts 6a and 6a' of the ferrule 6 are aligned with the flat parts of the assembly parts. A plurality of polarization-maintaining optical fibers 5 are assembled by aligning the directions that connect the two stress applying portions 5c, 5c of the respective polarization-maintaining optical fibers 5 in a fixed direction. It is a fiber array.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. FIG. 1 is a perspective view of an end portion of a polarization maintaining optical fiber.
There is a core 5b at the center of the clad 5a, and stress applying portions 5c and 5c are provided at symmetrical positions on both sides of the core 5b. The polarization plane of light of the polarization-maintaining optical fiber 5 is held in the direction connecting the two stress applying portions 5c, 5c or in the direction perpendicular thereto.

FIG. 2 is a perspective view in which a ferrule is attached to the end of the polarization maintaining optical fiber as described above, and 6 is a cylindrical ferrule having a flat portion 6a on a part of the outer circumference of the cylinder.
The ferrule 6 is polarized such that the direction connecting the two stress applying portions 5c, 5c of the polarization-maintaining optical fiber 5 and the flat portion 6a of the ferrule 6 have a fixed positional relationship, which is parallel in this embodiment. It is attached and fixed to the end of the holding optical fiber 5.

FIG. 3 is a diagram for explaining a method of aligning the polarization maintaining optical fiber. First, as shown in FIG. 3A, the polarization maintaining optical fiber 5 is mounted on the end portion as described above. When the fixed ferrule 6 is arbitrarily placed on the flat portion 7a of the guide rail 7 which is a flat member and the ferrule 6 is rolled in the direction indicated by the arrow, the ferrule 6 goes through (b) in FIG. 3 and then (c) in FIG.
When the flat portion 6a of the ferrule 6 comes into contact with the flat portion 7a of the guide rail 7 as shown in Fig. 1, rolling stops and the stationary state is most stable, and even if a predetermined force is continuously applied, the polarization maintaining optical fiber 5 The ferrule 6 attached to the end of the slides only slides on the flat portion 7a of the guide rail 7, and the state shown in FIG. 3C does not change.

Even if the rolling of the ferrule 6 mounted on the end of the polarization maintaining optical fiber 5 is changed to rotation during the series of the alignment operation of the polarization maintaining optical fiber, FIG. Since the state shown has the greatest resistance to rotation, it is clear that the state is stable. The predetermined force for rolling or rotating the ferrule 6 is set so that the flat portion 6a of the ferrule 6 will not roll or rotate further when it comes into contact with the flat portion 7a of the guide rail 7.

By adopting the polarization maintaining optical fiber alignment method as described above, the ferrule 6 mounted and fixed to the end of the polarization maintaining optical fiber 5 is guided as shown in FIG. With a simple operation of rolling or rotating the ferrule 6 by arbitrarily placing it on the flat portion 7a of the rail 7, without directly observing the end face of the polarization maintaining optical fiber 5, Stress applying part 5
The direction connecting c and 5c can be set to a predetermined direction, that is, the horizontal direction in this embodiment. Even if the ferrules attached and fixed to the ends of multiple polarization-maintaining optical fibers are placed on the guide rails, the rolling and rotation of each polarization-maintaining optical fiber do not interfere with each other. It is possible to align the direction in which the stress applying portions of the plurality of polarization maintaining optical fibers are connected to a predetermined direction by the operation of.

FIGS. 4 and 5 employ a polarization maintaining optical fiber alignment method as described above and incorporate four polarization maintaining optical fibers horizontally and vertically four layers of 16 polarization maintaining optical fibers. It is explanatory drawing which manufactures an optical fiber array. First, as described with reference to FIG. 2, the ferrule 6 having the flat portion 6a is attached and fixed to the end portion of the polarization maintaining optical fiber 5, and then, As shown in FIG. 4 (a), one flat member is used for the one end portion 6b in which the flat portions 6a of the four ferrules 6 mounted and fixed to the end portions of the polarization maintaining optical fiber 5 are formed as described above. The other end 6c of the ferrule 6 is arbitrarily placed on the flat portion 7a 'of a certain guide rail 7', and on the flat portion 7a "of the guide rail 7" which is the other flat member.

The flat portion 7a 'of the one guide rail 7'is the flat portion 7a of the other guide rail 7 ".
The height of the flat portion 6a of the ferrule 6 is higher than that of the a "by the cutout amount.
Is the flat portion 6a of one guide rail 7 '.
The ferrule 6 becomes horizontal when the ferrule 6 is in contact with.
Reference numeral 8 is a stopper fixed to one end of the flat portion of the guide rails 7'and 7 ", and 9 is a mounting table on which the guide rails 7'and 7" are mounted.

Next, as shown in FIG. 4 (b), the flat portions 7a ', 7'of the guide rails 7', 7 "are as described above.
The ferrule drive member 10 for rolling the ferrule 6 is placed at a position avoiding the flat portion 6a of the four ferrules 6 arbitrarily placed on the a ", and the ferrule drive member 10 is left as shown by the arrow. When the ferrule 6 is moved toward one side, and the flat portion 6a of the ferrule 6 comes into contact with the flat portion 7a 'of one guide rail 7', the ferrule 6 is moved.
When the flat portions 6a of the four ferrules 6 abut all the flat portions 7a 'of the guide rails 7', the adjacent ferrules 6 come into contact with each other as shown in FIG. 4C. When the stopper 8 provided at one end of the guide rails 7'and 7 "and the stopper 11 provided at one end of the ferrule driving member 10 are pressed against each other, the stress applying portions 5c of the four polarization maintaining optical fibers 5 are All the directions connecting 5c can be aligned in the horizontal direction.

Next, as shown in FIG. 5A, stress is applied to the concave portion of the frame 12 which is an assembly part formed by the bottom frame plate 12a and the side frame plates 12b and 12c as described above. A ferrule 6 mounted and fixed to the ends of four polarization-maintaining optical fibers 5 arranged with all the directions connecting the parts 5c, 5c aligned in the horizontal direction is incorporated.

At the time of this assembling, as shown in FIG. 4C, the stress applying portions 5c, 5c of the polarization maintaining optical fiber 5 are
After removing the ferrule drive member 10 on the four ferrules 6 placed on the guide rails 7 ′ and 7 ″ with all the directions connecting 5c aligned in the horizontal direction,
The ferrule 6 of the book is separated from a stopper 8 provided at one end of the guide rails 7 ', 7 ", and one side frame is provided between the outer ferrule 6 and the guide rails 7', 7" juxtaposed with the stopper 8. The plate 12c is inserted, and the one side frame plate 12c and the other side frame plate 12b are inserted.
While fitting the four ferrules 6 between and,
The other side frame plate 12b is attached to the guide rail 7 ',
After being inserted between the 7 ", the guide rails 7 ', 7" are moved downward as shown by the arrows to pass the bottom frame plate 12a of the frame 12, which is an assembly part.

Then, as shown in FIG. 5B,
The flat portions 6a of the four ferrules 6 are horizontally aligned on the bottom frame plate 12a, that is, two stresses are applied to the polarization maintaining optical fiber 5 having the four ferrules 6 mounted and fixed at the ends. All the directions connecting the parts 5c, 5c are arranged in the horizontal direction.

When the above operation is repeated 4 times, 16
The two polarization maintaining optical fibers 5 are the two stress applying parts 5
The connecting direction of c and 5c can be arranged in the horizontal direction, and as shown in FIG. 5C, the top four ferrules 6 are covered with the top frame plate 12d, and then the ferrule. 6 and each frame plate and between the ferrules 6, for example, an ultraviolet curable adhesive (UV adhesive) 13 is filled,
Irradiate ultraviolet rays to cure the ultraviolet curable adhesive. Finally, the end faces of the polarization maintaining optical fiber 5 and the ferrule 6 are polished to manufacture a polarization maintaining optical fiber array.

FIG. 6 is a view for explaining another alignment method of the polarization-maintaining optical fiber, which is a cylindrical ferrule 6 having two flat portions 6a, 6a 'facing each other in parallel to the outer circumference of the cylinder.
To the two stress applying portions 5c, 5 of the polarization maintaining optical fiber 5.
c direction and flat portions 6a, 6a 'of the ferrule 6
Are fixed to the ends of the polarization-maintaining optical fiber 5 so that they are parallel to each other, and then, as shown in FIG. 6A, the ferrule 6 is flattened on the flat portion 7 of the guide rail 7 which is a flat member.
By rotating or rolling on a, and as shown in FIG. 6 (b), the flat portion 6a (or 6a ') of the ferrule 6 and the flat portion 7a of the guide rail 7 are brought into alignment with each other. Two stress applying parts 5 of the wave holding optical fiber 5
The direction connecting c and 5c can be aligned in the horizontal direction. According to this polarization maintaining optical fiber alignment method,
By rotating the ferrule 6 a half turn, the flat portion 6a or 6a 'of the ferrule 6 and the flat portion 7a of the guide rail 7 can be aligned.

The polarization maintaining optical fiber array employing the polarization maintaining optical fiber alignment method shown in FIG. 6 is manufactured in exactly the same manner as the manufacturing method shown in FIGS. 4 and 5 above. As shown in (a), the four ferrules 6 mounted and fixed to the end of the polarization maintaining optical fiber 5 as described above.
Of the guide rail 7 ', which is one flat member, and the other end 6c of the ferrule 6 is the other flat member. It is arbitrarily placed on the flat portion 7a "of the guide rail 7".

Next, as shown in FIG. 7 (b), the flat portions 7a ', 7a "of the guide rails 7', 7" are as described above.
The ferrule drive member 10 for rolling the ferrule 6 is placed on the four ferrules 6 arbitrarily placed on the ferrule 6, and the ferrule drive member 10 is moved to the left as shown by the arrow, and the ferrule 6 is rotated half a turn. Then, the flat parts 6a and 6a 'of the ferrule 6 are replaced by the flat parts 7 of one guide rail 7'.
When the ferrule 6 comes into contact with a ', the rolling of the ferrule 6 is stopped, and the flat portions 6a (or the flat portions 6) of the four ferrules 6 are stopped.
When the a ') all come into contact with the flat portion 7a' of the guide rail 7 ', as shown in FIG. 7C, the ferrules 6 adjacent to each other are provided on the guide rails 7', 7 ". When pressed by the stopper 8 and the stopper 11 provided on the ferrule drive member 10, the four polarization-maintaining optical fibers 5 are pressed.
All the directions that connect the stress applying portions 5c and 5c can be aligned in the horizontal direction.

Next, as shown in FIG. 8 (a), between the both side frame plates 12b, 12c of the frame 12 which is an assembly part formed of the bottom frame plate 12a and the both side frame plates 12b, 12c. , The four ferrules 6 mounted and fixed to the ends of the four polarization-maintaining optical fibers 5 are fitted, and the guide rails 7 ′ and 7 ″ are moved downward as shown by arrows to form an assembly part. The bottom frame plate 12a of a certain frame 12 is passed.

Then, as shown in FIG. 8B,
Flat parts 6a, 6a 'of four ferrules 6 are horizontally aligned on the bottom frame plate 12a, that is,
The ferrule 6 of the book is arranged such that all the directions connecting the two stress applying portions 5c, 5c of the polarization maintaining optical fiber 5 mounted and fixed to the end are aligned in the horizontal direction.

When the above operation is repeated 4 times, 16
The two polarization maintaining optical fibers 5 are the two stress applying parts 5
The direction connecting the c and 5c can be aligned in the horizontal direction, and as shown in (c) of FIG. 8, the top four ferrules 6 are covered with the top surface frame plate 12d, and then the ferrule. 6 and each frame plate and between the ferrules 6, for example, an ultraviolet curable adhesive (UV adhesive) 13 is filled,
Irradiate ultraviolet rays to cure the ultraviolet curable adhesive. Finally, the end faces of the polarization maintaining optical fiber 5 and the ferrule 6 are polished to manufacture a polarization maintaining optical fiber array.

In the above embodiment, the direction in which the two stress applying portions 5c, 5c of the polarization-maintaining optical fiber 5 are connected and the flat portion 6a or the flat portion 6a 'of the ferrule 6 are parallel to each other. Although the ferrule 6 is attached and fixed to the end of the polarization maintaining optical fiber 5, the present invention is not limited to this. For example, the two stress applying parts 5c and 5c of the polarization maintaining optical fiber 5 are provided.
The ferrule 6 may be attached and fixed to the end of the polarization maintaining optical fiber 5 so that the direction connecting the c and the flat portion 6a or the flat portion 6a 'of the ferrule 6 are orthogonal to each other. The ferrule 6 is attached and fixed to the end of the polarization-maintaining optical fiber 5 so that the direction connecting the two stress applying portions 5c, 5c of 5 and the flat portion 6a or the flat portion 6a 'of the ferrule 6 is oriented at 45 degrees. You may. In the claims, "... a ferrule is defined as an end portion of a polarization-maintaining optical fiber such that a direction connecting the two stress applying portions of the polarization-maintaining optical fiber and a flat portion of the ferrule have a fixed positional relationship. The above description means that it is attached and fixed to the .... ".

[0030]

According to the present invention, the method for aligning a polarization maintaining optical fiber as described in claim 1 or 2 is adopted, whereby the two stress applying portions of the polarization maintaining optical fiber are connected to each other. Rotate or roll the ferrule mounted and fixed to the end of the polarization-maintaining optical fiber so that the flat portion formed on the ferrule has a fixed positional relationship, and rotate or roll the ferrule on the flat member to move the flat portion of the ferrule to the flat portion of the flat member. Since the alignment in the direction connecting the two stress applying parts of the polarization-maintaining optical fiber can be performed by a simple operation such as contacting the end face of the polarization-maintaining optical fiber with an observation device such as a camera or a television monitor. It is possible to arrange the polarization maintaining optical fiber so that the direction connecting the two stress applying portions is directed to a predetermined direction without directly observing. According to the polarization maintaining optical fiber alignment method as set forth in claim 2, when the ferrule is half-turned on the flat member,
Since the flat portion formed on the ferrule comes into contact with the flat portion of the flat member, the alignment in the direction connecting the two stress applying portions of the polarization maintaining optical fiber becomes easier.

Further, by adopting the above-described polarization maintaining optical fiber alignment method in which the direction connecting the two stress applying portions of the polarization maintaining optical fiber is oriented in a predetermined direction,
It is also possible to automate the production of the polarization-maintaining optical fiber array as set forth in claim 3 or claim 4, the production efficiency is high, and the production cost can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of an end portion of a polarization maintaining optical fiber.

FIG. 2 is a perspective view in which a ferrule having a flat portion at an end is attached and fixed to a polarization maintaining optical fiber.

FIG. 3 is a diagram illustrating a method of aligning a polarization maintaining optical fiber according to the present invention.

FIG. 4 is a diagram for explaining the manufacture of the polarization maintaining optical fiber array of the present invention.

FIG. 5 is a diagram for explaining the manufacture of the polarization maintaining optical fiber array of the present invention.

FIG. 6 is a diagram illustrating another method for aligning a polarization maintaining optical fiber according to the present invention.

FIG. 7 is a diagram for explaining the manufacture of another polarization maintaining optical fiber array of the present invention.

FIG. 8 is a diagram for explaining the manufacture of another polarization maintaining optical fiber array of the present invention.

FIG. 9 is a perspective view showing a structure of a conventional polarization maintaining optical fiber array.

[Explanation of symbols]

 1 optical fiber 2 ferrule 3a inner frame plate 3b outer frame plate 4 adhesive A two-dimensional optical fiber array 5 polarization maintaining optical fiber 5a clad 5b core 5c stress applying part 6 ferrule 6a flat part 6a 'flat part 6b one end part 6c and others End 7 Guide rail 7'Guide rail 7 "Guide rail 7a Flat portion 7a 'Flat portion 7a" Flat portion 8 Stopper 9 Mounting table 10 Ferrule drive member 11 Stopper 12 Frame 12a Bottom frame plate 12b Side frame plate 12c Side frame plate 12d Top surface frame plate 13 UV curable adhesive

Claims (4)

[Claims] Claim: What is claimed is: 1. A cylindrical ferrule having a flat portion on a part of the outer circumference of a cylinder, wherein the flat portion of the ferrule and the direction connecting the two stress applying portions of the polarization maintaining optical fiber have a fixed positional relationship. Attached and fixed to the end of the polarization maintaining optical fiber,
Next, by rotating or rolling the ferrule on a flat member, and by aligning the flat portion of the ferrule with the flat portion of the flat member, the direction connecting the two stress applying portions of each polarization maintaining optical fiber, respectively. A polarization-maintaining optical fiber alignment method characterized by aligning in a fixed direction. 2. A cylindrical ferrule having two flat portions facing each other in parallel to the outer circumference of the cylinder is arranged in a fixed positional relationship between the direction connecting the two stress applying portions of the polarization maintaining optical fiber and the flat portion of the ferrule. By mounting and fixing to the end of the polarization maintaining optical fiber, then rotating or rolling the ferrule on a flat member, by aligning the flat portion of the ferrule and the flat portion of the flat member, A method for aligning a polarization-maintaining optical fiber, characterized in that the directions connecting the two stress applying portions of the polarization-maintaining optical fiber are aligned in a fixed direction. 3. A cylindrical ferrule having a flat portion on a part of the outer circumference of the cylinder, wherein the flat portion of the ferrule and the direction connecting the two stress applying portions of the polarization-maintaining optical fiber have a fixed positional relationship. Attached and fixed to the end of the polarization maintaining optical fiber,
A large number of polarization-maintaining optical fibers were assembled by aligning the flat part of the ferrule and the flat part of the assembly component so that the directions connecting the two stress applying parts of each polarization-maintaining optical fiber were aligned in a constant direction. A polarization maintaining optical fiber array characterized by the above. 4. A cylindrical ferrule having two flat parts facing each other in parallel to the outer circumference of the cylinder is arranged in a fixed positional relationship between the direction connecting the two stress applying parts of the polarization maintaining optical fiber and the flat part of the ferrule. Attached and fixed to the end of the polarization maintaining optical fiber so that the flat part of the ferrule and the flat part of the assembly part are aligned, and the directions connecting the two stress applying parts of each polarization maintaining optical fiber are respectively A polarization-maintaining optical fiber array characterized by assembling a large number of polarization-maintaining optical fibers aligned in a fixed direction.