JPH0876037A - Production of polarization plane-maintaining optical fiber switch - Google Patents

Abstract

PURPOSE: To obtain a polarization plane-maintaining optical fiber switch which is small in size, low in loss and reflection and has low polarization crosstalk by subjecting a moving fiber to a specific rotation adjustment. CONSTITUTION: Panda fibers 21 are arranged in half-split ferrules 4 and the end faces of the ferrules 4 are made flush with the end faces of the fibers 21 at the time of fixing two pieces of the panda fibers 21 as static fibers 2 into V-grooves. A hairline 22 is perpendicularly moved from the flat faces of the V-grooves and the fibers 21 are rotationally adjusted so as to bring the outer periphery of the right and left circular stress imparting parts 21a of the panda fibers 21 into contact with this hairline 22. A main axis X-X' and the flat plane 23 of the V-grooves are paralleled by this operation. Further, the static fibers 21 are retreated by a prescribed length and are adhered and fixed into the V-groove parts after the end of the position adjustment of the main axis X-X' and the flat plane 23 of the V-grooves. The other static fibers 21 are similarly adhered and fixed to the V-grooves of the ferrules 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be applied to an optical communication system and an optical information processing system for transmitting and receiving or controlling an optical signal while preserving the plane of polarization, an optical measuring system and a polarization control optical device. The present invention relates to a method of manufacturing a wavefront preserving optical fiber switch.

[0002]

2. Description of the Related Art In an optical communication system and various optical sensor devices using a polarization-maintaining optical fiber, the polarization state is maintained, that is, crosstalk between two polarization main axes of the polarization-maintaining optical fiber is prevented. An optical switch that switches the path of light while suppressing it to a low level is useful for greatly expanding the functions of these systems and devices. Such an optical switch is required to have low loss, low reflection, and, above all, a small polarization crosstalk showing polarization maintaining ability.
Conventionally, no optical switch of this type has been found, and an optical connector has been attached and detached instead of the switch. This conventional method has a problem in that it is complicated to attach and detach, and it is difficult to maintain the reproducibility of various optical characteristics associated with a large number of attachments and detachments.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems of the prior art and to obtain a polarization maintaining optical fiber switch having a small size, low loss, low reflection and low polarization crosstalk. It is to provide a manufacturing method capable of

[0004]

According to the method of manufacturing a polarization-maintaining optical fiber switch of the present invention, a plurality of stationary fibers made of polarization-maintaining optical fibers are fixed in a V groove of a ferrule so as to face these stationary fibers. A movable fiber made of a polarization-maintaining optical fiber is disposed in the optical fiber, and the movable fiber is displaced with respect to the stationary fiber by a driving means in order to perform a self-holding type optical switching operation between the movable fiber and the stationary fiber. A method of manufacturing a polarization-maintaining optical fiber switch that allows the above-mentioned static fibers to be housed in a split sleeve, and retains these static fibers when fixing the two static fibers to the V groove of the half-split ferrule. One of the two main axes holding the two polarized waves is arranged so as to be parallel or perpendicular to the predetermined surface of the V-groove and adhered to the lower portion of the V-groove. Then, when the movable fiber and the stationary fiber are connected to each other, while switching the movable fiber to the stationary fiber, the polarization crosstalk is observed each time, and the movable fiber is set so as to minimize the value. The ferrule in which the root of the movable fiber is inserted is adhesively fixed to the split sleeve after rotation adjustment, and the refractive index of the core of the fiber is equal to the gap between the movable fiber and the stationary fiber facing each other. Is filled with a non-volatile refractive index matching liquid having a predetermined viscosity.

[0005]

As described above, according to the present invention, in the manufacture of a movable fiber type optical switch composed of a polarization-maintaining optical fiber, a plurality of static fibers, whose polarization plane principal axes are V-grooves for optical axis matching, are used. To be parallel or perpendicular to the plane of, the main axes that hold the polarized waves between the plurality of stationary fibers by fixing them in the V groove are parallel or perpendicular to each other,
It is characterized in that the movable fiber facing the stationary fiber with a predetermined gap is rotationally adjusted so that the main axis of polarization thereof is parallel or perpendicular to those of the stationary fiber to assemble the optical switch. Therefore, as compared with the conventional method in which the polarization-preserving fiber is switched by attaching and detaching the optical connector, it is different from the conventional technology in that the switching operation can be speeded up and excellent reproduction characteristics of optical characteristics can be obtained at the time of switching. .

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an example of a polarization-maintaining optical fiber switch manufactured by the method of the present invention, the structure of a 1 × 2 optical switch composed of a polarization-maintaining optical fiber is shown in FIGS.
Shown in Fig. 1 is a side view of a partial cross section of this switch.
2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a schematic enlarged view of a portion III surrounded by a dotted line in FIG. This optical switch has one movable polarization-maintaining fiber 1, two stationary polarization-maintaining fibers 2, a ferrule 3 that fixes the root of the movable fiber, and a set of two Vs on which the stationary fiber 2 is fixed. It is composed of a grooved half-split ferrule 4, a fine magnetic film pipe 5 fixed near the tip of the movable fiber, a solenoid coil 6 for driving the movable fiber, permanent magnets 8a and 8b, and a split sleeve 7 which also serves as a housing.
In this configuration, the solenoid coil 6 and the permanent magnet 8
Reference characters a and 8b constitute a drive means for the movable fiber 1. The tip of the movable fiber 1 is inserted into the V-groove of the above-mentioned half-split ferrule 4 for several mm, and the upper and lower permanent magnets 8a are arranged in accordance with the longitudinal magnetization polarity of the magnetic film pipe 5.
Or 8b, for example, one of the permanent magnets 8a is attracted to the tip thereof, and the tip of the permanent magnet 8a is placed in the V groove.
One of them is connected with a gap of several tens of μm. By reversing the magnetization polarity of the magnetic film pipe 5 with the solenoid coil 6, the movable fiber 1 is attracted to the other permanent magnet 8b and switched to the other stationary fiber 2. It suffices to energize the coil 6 only when reversing the magnetization polarity of the magnetic film pipe 5, and even after the energization is stopped, the movable fiber 1 is pressed against the V groove of the half ferrule 4 by the permanent magnets 8a and 8b, and the stationary fiber 2 is formed. A good connection is maintained. Such a switch operation is called a self-holding type.

In the polarization-maintaining optical fiber, it is necessary to maintain the polarization state of the optical signal propagating through the core well between the input and the output. Although there are several types of polarization-maintaining fibers, this embodiment describes a method of assembling an optical switch using a panda fiber having stress applying portions formed on both sides of a core portion as shown in FIG. To do.

FIG. 4 shows a cross section of the panda fiber 10. In the figure, 10a indicates a stress applying portion and 10b indicates a core. In this fiber 10, there are two main axes XX 'and YY' for holding the plane of polarization, and the linearly polarized optical signal input along one polarization axis is in the polarization state. Is output while maintaining. The polarization crosstalk Pcr, which represents the degree to which the optical power moves from one main axis to the other main axis as it propagates, is an important parameter of the polarization-maintaining optical fiber. When connecting panda fibers, it is required to have low loss and low reflection, as in the case of connecting ordinary single-mode optical fibers, but it is also important to suppress the above polarization crosstalk. The deterioration factors of the polarization crosstalk include the lateral pressure on the fiber and the angle deviation between the main axes of the opposing Panda fibers. On the other hand, in the optical switch shown in FIGS. 1 to 3, the tip of the movable fiber 1 is pressed against the V groove of the ferrule 4.
The force is several tens of mgf, and the deterioration of polarization crosstalk caused by this is negligible. Therefore, in this optical switch, it is important to control the angular deviation between the main shafts when the switch is assembled.

As shown in FIG. 5, the polarization crosstalk Pcr when there is an angle deviation θ between the opposing panda fibers 20 and 21 is Pcr = −10 log (tan ² θ).
The angle deviation is 0 °, 90 ° is the minimum, and
Maximum at °. That is, if there is an angle deviation of 45 °, the plane of polarization cannot be maintained, and the depolarizer is used. Therefore, when assembling a 1 × 2 optical switch using a panda fiber, a highly accurate optical axis adjustment is performed between the movable fiber and the two stationary fibers, and at the same time, the stationary fiber or Optimal placement of moving fibers is required. In FIG. 5, reference numeral 20a,
21a is a stress applying portion of each of the fibers 20 and 21,
20b and 21b are cores.

A method of aligning the main axes will be described below with reference to FIG. Since the fibers 20 and 21 have the same structure, the fiber 21 is used in the drawing. First, when fixing two panda fibers 21 as the stationary fiber 2 to the V groove, the bare panda fiber 21 is arranged in the V groove of the half-divided ferrule 4, and the end surface of the ferrule 4 and the end surface of the fiber 21 are aligned with each other. Both ends are observed from the front with a microscope. Since the main axis of the panda fiber 21 is naturally invisible, the horizontal hairline 22 of the television monitor screen connected to the microscope is arranged on the flat surface 23 of the V groove, for example. Next, the hairline 22 is vertically moved from the V-groove flat surface 23 and the fiber 21 is rotationally adjusted so that the outer circumferences of the left and right circular stress applying portions 21 a of the panda fiber 21 are in contact with the hairline 22. By the above operation, the main axis XX ′ and the V-groove flat surface 23 become parallel. As shown in FIGS. 1 to 3, in the optical switch, the tip of the movable fiber 1 is several meters.
It is inserted into the V groove by m, and is connected to the stationary fiber 21. For this reason, as shown in FIG.
After the position adjustment between the V groove flat surface 23 and the V groove flat surface 23 is completed, the stationary fiber 21 is retracted by a predetermined length and is adhesively fixed to the V groove portion. The other stationary fiber 21 is also V of ferrule 4 similarly.
It is adhesively fixed to the groove. The stationary fiber 21 is arranged and fixed in the V-shaped groove by temporarily fixing the fiber 21 to a fine movement table which can be horizontally / vertically moved and rotated. In this way the stationary fiber 2
The two semi-cylindrical ferrules 4 and 4 in which 1 is fixed in the V groove are inserted and fixed in the split sleeve 7, and as shown in FIG.
The main axes of the upper and lower stationary fibers 21, 21 are parallel to each other. After inserting the coil 6 into the split sleeve 7, the movable fiber 1 whose root is fixed to the ferrule 4 is inserted, the permanent magnets 8a and 8b are arranged, and the coil 6 is also energized. In this state, the movable fiber 1
The ferrule 4 fixing the root of the can be moved back and forth and rotated. Finally, the main axis of the movable fiber 1 and the
The alignment work between the main axes of the stationary fibers 21 and 21 of the book is performed in the following manner.

That is, the tip of the movable fiber 1 is inserted into the V groove portion so as to face the stationary fibers 21 and 21, and the coil 6 is energized to perform a self-holding type switch operation, while the movable fiber 1 and the movable fiber 1 are vertically stationary. Polarization crosstalk at the time of connection between the fibers 21 and 21 is observed, the movable fiber 1 is rotated so as to minimize them, and the ferrules 4 and 4 which fix the root of the movable fiber 1 at the best position. Adhesively fixed to the split sleeve 7. The polarization crosstalk is measured by making the light emitted from the light source enter the movable fiber 1 of the optical switch via the polarizer, and the output light from the stationary fibers 21 and 21 facing each other via the analyzer. Observe at. The polarization crosstalk is found from the ratio of the two by observing the maximum and minimum values of the optical power by rotating and adjusting the polarizer and the analyzer.

FIG. 9 shows the result of measuring the polarization crosstalk when the movable fiber 1 is rotated in this measurement system while being connected to the upper and lower stationary fibers 21 and 21. The polarization crosstalk between the two stationary fibers shown is shown. The movable fiber 1 is fixed at the position where the crosstalk is minimized. Table 1 shows various characteristics of the panda fiber switch manufactured in this way.
Summarized in. In this switch, the opposing fiber gap is filled with a refractive index matching liquid having the same refractive index as the core, and as shown in the table, it has extremely low loss and low reflection optical characteristics. .

[0013]

[Table 1]

Further, the polarization crosstalk did not deteriorate before and after the filling of the liquid, was almost the same value as that of the connector, and the deterioration before and after the switch assembly was not observed.

The present embodiment is an example of a 1 × 2 optical switch, and the main axes of the two stationary fibers in the same direction are adjusted to be parallel when the V groove is fixed. Polarization crosstalk can be suppressed even by rotating one of the main axes of the two stationary fibers 31, 31 by 90 ° as shown in FIG. Further, according to such a method of adjusting the main axes, not only the 1 × 2 optical switch,
For example, as shown in FIG. 11, one movable fiber 40
On the other hand, a configuration of a 1 × 4 optical switch in which four static fibers 41 are arranged is also possible. The arrows in both figures indicate the movement of the movable fiber.

[0016]

As described above, the present invention adjusts the polarization maintaining main axis between the movable fiber and the stationary fiber with high accuracy when manufacturing a self-holding type panda fiber switch which is not found in the prior art. It is possible to manufacture a practical polarization-maintaining optical fiber switch by using a switch manufactured by this method. It is possible to improve the configurations and functions of wave control optical devices and polarization-based optical sensors, and the effects are great.

[Brief description of drawings]

FIG. 1 is a side view in partial cross-section showing a structure of a 1 × 2 optical switch composed of a polarization-maintaining optical fiber.

FIG. 2 is a sectional view taken along line II-II in FIG.

3 is a schematic enlarged view of a portion III surrounded by a dotted line in FIG.

FIG. 4 is a cross-sectional configuration diagram of a panda fiber which is a stress imparting polarization maintaining fiber.

FIG. 5 is a view for explaining a method of aligning polarization-maintaining main axes of two stationary fibers when manufacturing a panda fiber switch, and is an end view of two fibers whose main axes are deviated.

FIG. 6 is a view for explaining a method of aligning the polarization plane-maintaining spindles of two stationary fibers when manufacturing a panda fiber switch, and is an end view showing a state where the fiber is arranged in a V groove of a ferrule.

FIG. 7 is a perspective view for explaining a method of aligning polarization-maintaining principal axes of two stationary fibers when manufacturing a panda fiber switch, and is a perspective view showing a state where the fibers are arranged in a V groove of a ferrule.

FIG. 8 is a view for explaining a method of aligning polarization-maintaining main axes of two stationary fibers when manufacturing a panda fiber switch, after the two stationary fibers are arranged in the V groove of each ferrule. FIG. 3 is an end view showing a state in which ferrules are combined.

FIG. 9 is a graph showing an evaluation result of polarization crosstalk and an angle error between main axes of a movable fiber and a stationary fiber when manufacturing a panda fiber.

FIG. 10 is an end face configuration diagram of a main part for explaining a method of aligning the polarization plane-maintaining spindles of two stationary fibers when manufacturing a panda fiber switch.

FIG. 11 is an end face configuration diagram showing the positional relationship of the polarization plane-maintaining spindle between one movable fiber and four stationary fibers when configuring a 1 × 4 panda switch.

[Explanation of symbols]

 1 Movable polarization-maintaining fiber 2 Static polarization-maintaining fiber 3 Ferrule that fixes the base of movable fiber 4 Half-grooved ferrule with V groove 5 Magnetic film pipe 6 Hollow solenoid coil 7 Split sleeve 8 Permanent magnet 9 Optical connector 10 Panda fiber cross section 10a, 20a, 21a Panda fiber stress applying part 10b, 20b, 21b Panda fiber core 20, 30, 40 Movable panda fiber 21, 31, 41 Static panda fiber 22 Monitor TV camera Hairline 23 V groove flat part

Claims (1)

[Claims] 1. A plurality of stationary fibers made of a polarization-maintaining optical fiber are fixed in a V groove of a ferrule, and a movable fiber made of a polarization-maintaining optical fiber is arranged so as to face these stationary fibers. A polarization-maintaining optical fiber switch in which the movable fiber is displaceable with respect to the stationary fiber by a driving means in order to perform a self-holding type optical switching operation with the stationary fiber, and these are housed in a split sleeve. A method of manufacturing, wherein, when fixing the two stationary fibers to the V groove of the half ferrule, one of the two main axes that retains the two polarizations of these stationary fibers is provided in the V groove. When arranged so as to be parallel or perpendicular to a predetermined surface and adhesively fixed to the lower portion of the V groove, when the movable fiber and the stationary fiber are connected to face each other, While switching the movable fiber to the stationary fiber, the polarization crosstalk is observed each time, the movable fiber is rotationally adjusted so that the value is minimized, and then the ferrule in which the root of the movable fiber is inserted. Adhesively fixing to the split sleeve, the gap portion between the movable fiber and the stationary fiber facing each other, filled with a nonvolatile refractive index matching liquid having a predetermined viscosity equivalent to the refractive index of the core of the fiber, A method of manufacturing a polarization-maintaining optical fiber switch, comprising: