JPH04372910A - Photo-coupler with variable photo-branching ratio and photo-coupling ratio - Google Patents

Abstract

PURPOSE:To provide a photo-coupler capable of adjusting the photo-branching ratio and photo-coupling ratio as desired. CONSTITUTION:The outsides of multiple optical fibers 1, 2 in the longitudinal direction are welded at one point, and the paths are continuously changed from a welded section 3 to separation sections 5a, 5b via contact sections 4a, 4b along the optical fibers 1, 2. A variable-pressure means 10 capable of pressurizing from the contact sections 4a to the separation sections 5a from the outsides of the optical fibers 1, 2 in the longitudinal direction is provided. When the variable-pressure means 10 is pressurized, the separation sections 5a are brought into contact with each other, and the length of the contact sections is increased. The photo-branching ratio and photo-coupling ratio of a photo-coupler are determined by the magnitude of welding or contact between the optical fibers 1, 2, and the photo-branching ratio and photo-coupling ratio can be increased when the total length d1 of the welded section 3 and contact sections 4a, 4b is increased by pressurization.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber-type optical coupler in which a plurality of optical fibers are fused together and whose optical branching ratio and optical coupling ratio are variable.

0002

2. Description of the Related Art In optical communication systems, it is necessary to branch and combine optical signals propagated through optical fibers. If the outsides of a plurality of optical fibers are brought into close contact and the cladding at the contact portion is extremely thin, it becomes possible to branch and combine light, and it can be used for such purposes. The rate at which light is split, or the rate at which light is reversibly combined, is a function of the length of the contact area, the thickness of the cladding at that area, the refractive index of the optical fiber core, the refractive index of the cladding, and the wavelength of the light. Become.

[0003] Japanese Unexamined Patent Application Publication No. 142521/1983 has 2
An optical coupler is disclosed in which glass optical fibers are arranged in parallel, parts of both glass optical fibers are fused, and then a predetermined portion is stretched. This optical coupler has little transmission loss at the joint between glass optical fibers and is relatively easy to manufacture. In this optical coupler, the length of the contact portion and the thickness of the cladding at that portion change depending on the stretched length, which determines the light branching ratio. In other words, the control of the light branching ratio is
This is done by the amount of stretching. Therefore, the value of the branching ratio varies depending on the timing of stopping the stretching, making it difficult to obtain an optical coupler having a desired branching ratio. Therefore, this optical coupler is suitable for applications that require equal optical branching, such as optical interferometers and optical gyros that utilize the coherence of light, and systems that combine two optical signals with different optical intensities. It is difficult to use in applications that require light to be coupled to the same level.

[0004] Japanese Patent Application Laid-Open No. 58-60722 discloses an optical coupler in which two optical fibers are bonded together by polishing a portion of their outer sides in the longitudinal direction. By adjusting the position and distance of the bonded surface, that is, the polished surface, the light branching ratio can be adjusted. However, it is necessary to align the bonding surfaces with extremely high precision, and manufacturing requires adjusting each polished surface one by one, which requires skilled technology and a lot of time. It is difficult to say that it is an industrially suitable product.

[0005] Japanese Patent Application Laid-open No. 56-22403 describes a method in which two fibers are brought into contact with each other using fibers having a glass core clad with plastic, and the amount of bonding is controlled by the degree of compression. This method is made possible by using a plastic cladding that can be deformed by compression bonding, and because it is a plastic cladding, the transmission loss of the fiber itself is large. Furthermore, since it is difficult to heat-seal and connect the fiber to a glass clad fiber, its range of applications is limited.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the conventional optical couplers described above. The present invention provides an optical coupler that has low loss and can be used for a wide range of purposes.

[0007]

Means for Solving the Problems The optical coupler of the present invention, which has been made to achieve the above object, will be explained with reference to FIG. 1, which corresponds to an embodiment.

As shown in FIG. 1, the optical coupler of the present invention is a fiber type optical coupler, in which a plurality of single mode optical fibers 1 and 2 are partially fused on the outside in the longitudinal direction. Along the fibers 1 and 2, the fibers continuously change from the fused portion 3 to the contact portions 4a and 4b, and then to the separated portions 5a and 5b. A variable pressurizing means 10 is provided that can pressurize the single mode optical fibers 1 and 2 from the contact portion 4a to the separation portion 5a from the outside in the longitudinal direction.

[0009]

[Operation] With the above optical coupler configuration, when the variable pressure applying means 10 applies pressure, the separating portion 5a comes into contact with the contact portion 4a.
increases in length. In the fiber type optical coupler, the optical branching ratio and the optical coupling ratio are determined by the size of the fusion or contact between the fibers, so the total length d1 of the fused part 3 and the contact parts 4a and 4b is increased by the pressurization. If so, the optical branching ratio and optical coupling ratio can be increased. Therefore, the optical coupler of the present invention can adjust the optical branching ratio and the optical coupling ratio.

0010

EXAMPLES Examples of the present invention will be described in detail below.

FIG. 1 is a schematic diagram showing an embodiment of the optical coupler of the present invention. As shown in the figure, two optical fibers 1
and a part of the longitudinally outer side of 2 is fused. Each of the optical fibers 1 and 2 is made of a silica glass single mode optical fiber. A part of the coating of single mode optical fiber 1 and optical fiber 2 is removed, fixed in a state where they are in contact with each other, and a part of this contact part is heated with flame to fuse the two single mode optical fibers. It has been stretched. During stretching, monitor light is input from one end 1a of the single mode optical fiber 1, and the amount of light emitted from the other end 1b of the single mode optical fiber 1 and the end 2b of the single mode optical fiber 2 is controlled. The degree of stretching is adjusted while sensing to achieve the desired bonding ratio. By such stretching, the single mode optical fibers 1 and 2 are continuously stretched from the fused portion 3 to the contact portion 4a.
and 4b, it changes to separation parts 5a and 5b, forming a coupler part.

The coupler portion is placed in a holding frame 11 to protect it from damage caused by external vibrations. A micrometer 10, which is a variable pressure means, is attached to the holding frame 11 so that pressure can be applied from the outside from the contact portion 4a to the separation portion 5a. That is, the fixed surface 12 of the holding frame 11 is used as an anvil, and the spindle 13 of the micrometer 10 is used as an actuator to sandwich and apply pressure to the optical fibers 1 and 2, and the displacement amount of the applied pressure can be measured.

When the thimble 14 of the micrometer 10 is rotated in the direction of the arrow, the spindle 13 advances and pushes the optical fiber 1, and the contact portion 4a changes from the state shown in FIG. 1 to the state shown in FIG.
The situation will be longer as shown in . That is, the total length of the contact part 4a, the fused part 3, and the contact part 4b is from d1 to d2.
becomes longer. The total length is a parameter that determines the optical branching ratio and optical coupling ratio of the optical coupler, so by adjusting the amount of displacement of the spindle 13 while reading it on the scale, the optical branching ratio and optical coupling ratio can be determined with reproducibility. The combination ratio can be adjusted.

Monitor light is input from one end 1a of the single mode optical fiber 1, and while reading the amount of displacement of the spindle 13 on the scale, the other end 1b of the single mode optical fiber 1 and the single mode optical fiber The intensity of light emitted from the end 2b of 2 was measured using a photoelectric converter. The results are shown in FIG. Initially, it was an optical coupler with a branching ratio of 50%,
As the amount of displacement increases, the light intensity emitted from the single mode optical fiber 2 decreases, but on the contrary, the light intensity emitted from the single mode optical fiber 1 increases, increasing the overall light intensity. It was possible to change the branching ratio without changing the When the amount of displacement was set to 0.4 mm, the change could be made to 67%.

For comparison, a micrometer was provided to apply pressure to the fused portion 3 of the optical coupler, and measurements were made in the same manner as in Example 1. As a result, it was found that the light intensity emitted from the single mode optical fiber 1 and the single mode optical fiber 2 decreased almost uniformly as shown in FIG. That is, in this case, the overall light intensity decreases without changing the branching ratio. This only increased the insertion loss of the optical coupler and did not produce any beneficial effect.

FIG. 5 shows another embodiment, in which a bolt 15 is attached to the holding frame 11 as variable pressure means. A piezoelectric element 16 is attached to the tip of the bolt 15. An amplifier 17 and a meter 18 are connected to the piezoelectric element 16 . By screwing in or loosening the bolt 15, the length of the contact portion 4a changes, and the optical branching ratio and optical coupling ratio of the optical coupler can be changed. At this time, the pressure detected by the piezoelectric element 16 is read by the meter 18 to know the pressurized state by the bolt 15, and the optical branching ratio and optical coupling ratio can be adjusted with reproducibility.

[0017]

As described above in detail, the optical coupler of the present invention allows the optical branching ratio and optical coupling ratio to be finely adjusted as desired and easily. Applications that require equal optical branching, such as optical interferometers and optical gyros that utilize the coherence of light, and systems that combine two optical signals with different light intensities, which combine mixed light to the same level. It can be used in a wide range of applications, including applications that require

[Brief explanation of the drawing]

FIG. 1 is a schematic front view showing an embodiment of an optical coupler to which the present invention is applied.

FIG. 2 is an optical coupler to which the present invention is applied; FIG.

FIG. 3 is a diagram showing the relationship between the amount of displacement when pressure is applied to the optical coupler to which the present invention is applied and the intensity of light emitted from the optical fiber.

FIG. 4 is a diagram showing the relationship between the amount of displacement due to pressure and the intensity of light emitted from an optical fiber when pressure is applied to an optical coupler to which the present invention is not applied.

FIG. 5 is a schematic front view showing another embodiment of an optical coupler to which the present invention is applied.

[Explanation of symbols]

1 and 2 are optical fibers, 1a, 1b, 2a, and 2b are the ends of the optical fibers, 3 is a fused portion, 4a and 4b are contact portions, and 5a
・5b is a separation part, 10 is a micrometer, 11 is a holding member, 12 is a fixing surface, 13 is an actuator, 14 is a thimble, 15 is a bolt, 16 is a piezoelectric element, 17 is an amplifier,
18 is a meter.

Claims (5)

[Claims] Claim 1: A fiber-type optical coupler, in which a portion of the longitudinally outer sides of a plurality of optical fibers are fused together, and the fusion part changes continuously along the optical fibers through a contact part and into a separation part. The optical fiber is provided with a variable pressure means capable of applying pressure from the contact portion to the separation portion from the outside in the longitudinal direction of the optical fiber, and the optical branching ratio and the optical An optical coupler characterized by an adjustable coupling ratio. 2. Means for measuring the amount of displacement generated in the longitudinal direction of the optical fiber due to the pressure applied by the variable pressure means is attached, and the optical branching ratio and the optical coupling ratio due to increase/decrease of the contact portion are measured. The optical coupler according to claim 1, wherein the optical coupler can be adjusted by changing the amount of displacement. 3. The optical coupler according to claim 2, wherein the means for measuring the amount of displacement is a micrometer. 4. Means for measuring the pressure by the variable pressure means is provided, and the light branching ratio and the light coupling ratio by increasing and decreasing the contact portion can be adjusted from changes in the pressure force. The optical coupler according to claim 1. 5. The optical coupler according to claim 4, wherein the means for measuring pressure is a pressure detection circuit including a piezoelectric element.