JPS6046683B2 - Manufacturing method of optical branching coupler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an optical branching coupler for branching and coupling optical signals in an optical fiber communication circuit.

In optical fiber communication lines, for example, when branching and inserting optical signals for CATV, branching and inserting optical signals in data links, or branching signals to monitoring circuits, fault detection circuits, error rate measurement circuits, etc. An optical branching coupler is used.

FIG. 1 shows an example of an optical branching/coupling device conventionally used for such a purpose. It consists of a splitter 2 and lenses 3 to 6. The lenses 3 and 4 are connected to optical fibers 7 and 8 that constitute the main transmission path.
The output end face of the optical fiber 9 to which the optical signal to be inserted into the main transmission line is provided is arranged so as to face the lens 5, and the branched optical signal from the main transmission line is The input end face of the optical fiber 10 into which the light is input is placed opposite the lens 6 . Therefore, the optical signal from the optical fiber 7 is converted into parallel light beams by the lens 3, a part of which passes through the beam splitter 2 and is input to the end face of the optical fiber 8 by the lens 4, and the remaining part is converted into parallel light beams by the beam splitter 2. It is reflected and branched, and is input to the optical fiber 10 via the lens 6 as a branched output. On the other hand, the inserted optical signal from the optical fiber 9 is turned into a parallel beam by the lens 5, a part of which is reflected and inserted into the main transmission path, and the remaining part is input into the optical fiber 10. As mentioned above, conventional optical branching couplers consist of a combination of a beam splitter and a lens, which are formed by forming a dielectric multilayer film on a transparent plate such as glass. Therefore, the optical path of the optical signal is shifted by passing through the beam splitter, and it is necessary to make extremely troublesome adjustments to align the optical axis accordingly.Secondly, in order to eliminate aberrations, It has the disadvantage that insertion loss increases unless an aspherical lens is used as the lens, and the third disadvantage is that it is extremely difficult to assemble these optical system components with precision and hold them stably. are doing. Therefore, in order to eliminate such drawbacks, optical branching couplers having configurations as shown in FIGS. 2 to 5 have been considered.

That is, in FIG. 2, the optical branching coupler 11 is connected to the base 12.
and a concave recess 13 provided approximately in the center of the base 12.
and a prism assembly 14 secured therein. The prism assembly 14 includes two right-angled prisms 15 of the same shape.
, 16 are bonded to each other via a beam splitter surface 17, and this beam splitter surface 17 is formed by depositing a dielectric multilayer film on the bonded surface 15a of one of the rectangular prisms 15. The prisms can be bonded together using an optically transparent adhesive such as balsam resin. On the other hand, on the base surface 12a on which the prism assembly 14 is provided, ■-shaped grooves 18 to 21 are provided as guide and storage grooves for guiding and storing optical fibers, corresponding to the surfaces 15b, 15c, 16a, and 16b of each prism. It is being The groove 18 is formed such that its axis is perpendicular to the surface 15b and has an angle of 45 with respect to the beam splitter surface 17, so that the optical fiber 2
2 is housed in the ■-shaped groove 18, the axis of the optical fiber 22 becomes parallel to the axis of the V-shaped groove 18, and the optical fiber 22
The optical signal transmitted from the end face is transmitted to the prism face 1.
5b and strikes the beam splitter surface 17 at an angle of 45°. The other V-shaped grooves 19 to 21 are also formed at similar angles to the opposing prism surfaces. Reference numerals 23 to 25 indicate optical fibers that are guided and housed in the square grooves 19 to 21, respectively. FIG. 3 shows the arrangement of the prism assembly 14 and the optical fibers 22 to 25 guided and housed in each of the square grooves.

Each of the optical fibers 22 to 25 consists of a core portion 22a to 25a and a cladding portion 22b to 25b, and the optical signal propagates within the core portion while being reflected at the interface between the core portion and the cladding portion of the optical fiber. The end surface of each optical fiber facing the prism surface is spherically treated, for example by heating it with a Bunsen burner for several seconds, so that the optical signal input to or output from the optical fiber does not diverge to the outside and cause loss. It's becoming like that. According to such a configuration, for example, an optical signal propagated within the optical fiber 24 is output as a parallel light beam parallel to the axis of the optical fiber from the spherically treated end face, and is incident perpendicularly to the prism surface 16a. It propagates inside the prism 16 and hits the beam splitter surface at an angle of 45 degrees, and part of the signal goes straight as it is and enters the prism 15. This straight signal Kg travels from the prism surface 15b perpendicular to the prism surface 15b. and enters into the optical fiber 22 from the end faces of the optical fibers 22 arranged opposite to each other.

On the other hand, a part of the optical signal that has hit the beam splitter surface is reflected by the beam splitter surface, changes the optical path by 900 degrees, is extracted from the prism surface 16b as an optical signal, and enters the optical fiber 25. The ratio of the magnitude of the signal Kg to the reflected light signal ■ is determined by the formation state of the beam splitter surface, that is, the thickness of the dielectric multilayer film, etc., so the dielectric multilayer film can be adjusted according to the desired splitting ratio. The formation state of the optical fiber 24 can be determined.The case where the optical signal from the optical fiber 24 is branched into the optical fibers 22 and 25 has been described above, but as will be readily understood from the above explanation, the formation state of the optical signal from any one optical fiber can be determined. The signal can be branched to the other two optical fibers. Therefore, in the above case, if there is an optical signal % from the optical fiber 23, the optical signal a is branched to the optical fibers 22 and 25, so each branched light The signals Al, a2 are superimposed on the respective branch signals Bl, Y)2, and an optical signal can be inserted.The state of branching and insertion of this optical signal is similar to that of the conventional branching shown in Fig. 1. Although it is similar to a coupler, the optical splitter coupler shown in FIGS. 2 and 3 does not require alignment of the optical fiber and the prism assembly, but simply stores the optical fiber in a pre-prepared square groove. In addition, since the axis of each optical fiber is perpendicular to the prism surface of the prism assembly, the transmission of optical signals between the end surface of the optical fiber and the opposing prism surface is performed without reflection, and the optical path is Insertion loss can be made extremely small without any modification.In addition, in the optical fiber shown in Figures 2 and 3 above, since the end face of the optical fiber is treated to be spherical, the maximum diameter at the end becomes large. When the optical fiber is housed in the ■-shaped groove, there is a possibility that the axis of the optical fiber and the axis of the ■-shaped groove will not be parallel to each other.

Therefore, as shown in FIGS. 4 and 5, the prism assembly attached to the recess 13 and the terminal end 18a of the ■-shaped groove 18 are
The end portion 22c of the optical fiber 22 is formed between the V-shaped groove 18 and the prism assembly 14 by providing a space between the two and making the depth of the recess 13 deeper than the bottom wall of the V-shaped groove 18. It can also be accommodated in the recess 13.
The same applies to other optical fibers. Although the case has been described in which the end face of the optical fiber is treated to have a spherical surface, it is not necessarily necessary to perform a spherical treatment, and the fiber may simply be cut perpendicular to the axis.

In this case, it is obvious that the base 12 and the prism assembly 14 may be made of a transparent plate made of glass or the like, and the base 12 and the prism assembly 14 may be integrated, without having to separate the base 12 and the prism assembly 14. It is. An object of the present invention is to be able to mass-produce such an optical branching coupler, and to eliminate the need for troublesome positional adjustment by making the positional relationship between the prism assembly and the guide storage groove extremely accurate and manufacturing it in a single process. The object of the present invention is to provide a manufacturing method that can significantly reduce assembly costs.
The features of the present invention for achieving the above object include the step of forming a beam splitter surface on one side of a transparent rectangular plate, and the step of forming a beam splitter surface on one side of the transparent rectangular plate; spaced apart prisms, each of the plurality of prisms having an axis of 45° with respect to the beam splitter plane and perpendicular to any other plane; forming a first connecting prism block by forming a guide and storage groove for guiding and storing an optical fiber on the transparent rectangular plate; and forming a first connecting prism block along one side of another transparent rectangular plate; a plurality of prisms are formed at intervals, and at the same time, each of the plurality of prisms has an axis having 45 angles with respect to the one side and perpendicular to any other surface; forming a second connecting prism block by forming a guide storage groove for guiding and storing an optical fiber on the other transparent rectangular plate; A step of cutting and separating into required blocks, and a step of cutting and separating the first prism block obtained by cutting the first connected prism block and a second prism block obtained by cutting the second connected prism block into the beam splitter. The present invention provides a method of manufacturing an optical branching coupler, which includes a step of overlapping and bonding via surfaces.

The present invention will be described in detail below with reference to embodiments shown in FIG. 6 and below.

FIG. 6 shows the steps of a method for manufacturing an optical branching coupler as an embodiment of the present invention.

First, an elongated rectangular transparent plate 30 as shown in FIG. 6a is prepared.
is prepared, and a dielectric multilayer film is deposited on one side 31 of the plate 30 by appropriate known means such as vapor deposition, as shown in FIG. 6B, to form a beam splitter surface 32. In this drawing, the thickness of the multilayer film is exaggerated and shown to be extremely thick, but in reality, an extremely thin film is formed. As the plate 30, for example, a transparent glass plate or a plastic plate can be used. Next, as shown in FIG. 6c, one side 3 of this plate 30 is
1, right angle prisms 33a, 33B, . . . are provided at intervals, and at the same time, square grooves 34a, 34b, 34c, . . . are formed corresponding to the prism surfaces of these right angle prisms. Each of these right angle prisms 33a is formed so that one side surface becomes the beam splitter surface 32, and the remaining two side surfaces are formed as prism surfaces facing the V-shaped groove. Each of the square grooves is formed so that its axis is perpendicular to the corresponding prism surface and has an angle of 45 perpendicular to the beam splitter surface 32. The formation of each prism and the ■-shaped groove can be performed by appropriate means such as etching or pressing. In the illustrated example, the prism block consisting of two ■-shaped grooves corresponding to the prisms is formed by connecting three prisms. Although the case in which the number of the number of the number of the number of the number of the number of the number of number of number of number of number of number of number of number of number of number is provided is provided is shown in FIG. After a large number of prism blocks are connected and formed as described above, they are separated into individual prism blocks by cutting as shown by the dashed line in FIG. 6c. FIG. 7 shows the prism block 35 after being separated.

On the other hand, apart from the step of making the prism block with the splitter surface formed from the transparent rectangular plate described above, from another transparent rectangular plate, in exactly the same manner as explained above,
Form a prism block on which a beam splitter surface of the same size is not formed, and make the prism block on which this beam splitter surface is not formed and the prism block on which the above beam splitter surface is formed symmetrically through the beam splitter surface. By bonding with balsam resin or the like, the optical branching coupler shown in FIG. 2 can be formed.

With this method, a large number of prism blocks can be made from a single transparent plate at once, and the positional relationship between the prisms and V-grooves can be extremely accurate and they can be made at the same time, eliminating the need for troublesome position adjustments. Therefore, the assembly cost can be significantly reduced.

FIG. 8 shows another embodiment of the manufacturing method according to the present invention. In this embodiment, first, the beam splitter surface 3 is
The rectangular transparent plates 30 on which the beam splitter surface 32 is formed are aligned so that the surface on which the beam splitter surface 32 is formed faces the side surface of the other plate 30 on which the beam splitter is not formed. In this state, paste them first.

In this case, the thickness of each plate 30 is made the same in advance, and the flatness, straightness, and parallelism of the end faces are finished to optical precision. After the strip-shaped plates are bonded together to form one plate in this manner, they are divided as shown by dotted lines so that the bonded surface becomes the bonded surface of the two prisms. Next, in each section, a square area 3 of a predetermined size with the bonding surface as a diagonal line is set as illustrated in FIG.
Etching is performed except for 6 to form a square region in a convex shape higher than other surfaces. Next, only the peripheral edge 37 of this square area is etched to form a prism assembly 14 in which a recess 13 is formed around the periphery so as to be lower than the flat area 38 etched in the previous step (Fig. 10). reference). Subsequently, a square groove is formed in the flat portion 38 in the same manner as shown in FIG. 6, and then each section is cut out to complete a predetermined optical branching coupler. Even when using this method, the positional relationship between the prism and the ■-shaped groove is made extremely accurate, and the process is made in a single process, which eliminates the need for troublesome positional adjustment, so the assembly cost can be significantly reduced. This has the advantage of simplifying the bonding work. According to the present invention, it is possible to mass-produce an optical branching coupler that does not require optical axis alignment of optical fibers and has extremely low insertion loss. By making it in a single process, there is no need for troublesome position adjustment, and assembly costs can be significantly reduced.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a conventional optical branching coupler, and Figure 2 is a schematic diagram of a conventional optical branching coupler.
FIG. 3 is an explanatory diagram for explaining the operation of the optical branching coupler shown in FIG. 2; FIG. 4 is an optical branching coupler shown in FIG. 2. FIG. 5 is a plan view of the modification of FIG. 4, and FIGS. 6a to 6c are one implementation of the manufacturing process according to the manufacturing method of the present invention. FIG. 7 is a perspective view of a prism block completed by the process shown in FIG. 6, and FIGS. 8 to 10 are illustrations for explaining other embodiments according to the manufacturing method of the present invention. There is a diagram. 11... Optical branching coupler, 12... Base, 13... Dent, 14... Prism assembly, 15, 16... Prism, 17 ...Beam splitter surface, 18 to 21...V-shaped groove,
22 to 25... Optical fiber, 30...
...Plate, 31...One side, 32...Beam splitter surface, 33a, 33b...Right angle prism, 34a, 35a...■-shaped groove, 35... ...
prism block.

Claims (1)

[Claims] 1. A step of forming a beam splitter surface on one side of a transparent rectangular plate, and spacing a plurality of prisms having the beam splitter surface as one side along the one side of the transparent rectangular plate. At the same time, each of the plurality of prisms has an axis at an angle of 45° with respect to the beam splitter surface and perpendicular to any other surface, for guiding and storing an optical fiber. forming a guide storage groove on the transparent rectangular plate to form a first connecting prism block; and forming a plurality of prisms at intervals along one side of another transparent rectangular plate with the one side as one side. At the same time as forming an opening, the prism has an angle of 45 degrees to the one side surface and an axis perpendicular to any other surface, and is for guiding and storing an optical fiber. forming a guide storage groove on the other transparent rectangular plate to form a second connecting prism block, and cutting and separating the first connecting prism block and the second connecting prism block into required blocks, respectively. a step of overlapping a first prism block obtained by cutting the first connected prism block and a second prism block obtained by cutting the second connected prism block via the beam splitter surface; A method for manufacturing an optical branching coupler, comprising the step of bonding. 2. Claim 1, characterized in that the step of forming the first connecting prism block and the step of forming the second connecting prism block are performed by etching.
A method for manufacturing the optical branching coupler described in Section 1. 3. The method of manufacturing an optical branching coupler according to claim 1, wherein the step of forming the first connecting prism block and the step of forming the second connecting prism block are performed by a press.