JPS638710A - Optical multiplexer/demultiplexer for distribution coupled single mode and its production - Google Patents

Abstract

PURPOSE:To improve the crosstalk characteristic of an optical multiplexer/ demultiplexer to suppress increase of the insertion loss by inserting a wavelength selective filter to at least one of plural optical fibers which are welded and drawn of the optical multiplexer/demultiplexer. CONSTITUTION:Wavelength selective filters 7 and 8 are inclined at a prescribed angle to axes of optical fibers 2 and 3 and are inserted near an end part 5b in a third port side of a first optical fiber 2 and an end part 6b in a fourth port side of a second optical fiber 3. The wavelength selective filter 7 inserted to the first optical fiber permits the optical signal having a wavelength lambda1 to pass through, but reflects the optical signal having a wavelength lambda2, and the wavelength selective filter 8 permits the optical signal having the wavelength lambda2 to pass through, but reflects the optical signal having the wavelength lambda1. The crosstalk is reduced by >=30dB because of insertion of wavelength selective filters 7 and 8, and the reflected light is eliminated from optical fibers because these filters are inclined at the prescribed angle and are inserted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a distributed coupling type single mode optical multiplexer/demultiplexer and a method for manufacturing the same.

(Prior Art and its Problems) A two-wavelength single-mode optical multiplexer/demultiplexer is commercially available, in which two optical fibers are fused and stretched and the wavelength dependence of the electric field in the fused and stretched portion is utilized. The optical multiplexer/demultiplexer using this method has a low insertion loss of 0.5 dB or less; It is stable and has excellent characteristics against temperature changes, polarization dependence, etc.

However, the Kukostalk characteristic, which is one of the important characteristics in an optical multiplexer/demultiplexer, is currently only about -17 dB. Generally, in a digital wavelength division multiplexing transmission system, a crosstalk of about -30 dB is required, and conventional commercially available optical multiplexer/demultiplexers cannot meet this requirement. Conventionally, in order to meet this requirement, a wavelength selective filter, which is a separate component, was connected to the optical multiplexer/demultiplexer to reduce crosstalk. When a wavelength selective filter as a separate component is connected to an optical multiplexer/demultiplexer, although it is possible to reduce cocoon talk, there is a problem in that the loss of transmitted light increases and the cost increases.

The present invention has been made to solve such problems, and provides a distributed coupling type single mode optical multiplexer/demultiplexer that does not require a wavelength selective filter as a separate component and has improved crosstalk characteristics. The purpose is to provide a method for producing the same.

(Means for solving the problem) According to the first invention, in order to solve the above-mentioned problem,
An optical multiplexer/demultiplexer formed by fusing and stretching a plurality of optical fibers, characterized in that a wavelength selective filter is interposed in at least one of the plurality of optical fibers. Wave equipment is provided.

According to the second invention, in order to produce this distributed coupling type single mode optical multiplexer/demultiplexer, a plurality of optical fibers are fused and stretched, and a plurality of fused and stretched optical fibers are fused and stretched on a substrate. Among the optical fibers, a guide groove is carved for placing and fixing at least a first optical fiber in which a wavelength selective filter is to be interposed, and the first optical fiber is placed on the guide groove so that its end surface is on the guide groove. 1.
After the end face of a second optical fiber to be butt-connected to the end face of the optical fiber is butt-connected to the end face of the second optical fiber with the wavelength selective filter interposed therebetween, these first and second optical fibers are connected to the end face of the second optical fiber on the guide groove. Provided is a method for manufacturing a distributed coupling type single mode optical multiplexer/demultiplexer characterized in that the optical multiplexer/demultiplexer is fixed to .

Further, according to the third aspect of the present invention, a plurality of optical fibers are fused and stretched, and among the plurality of optical fibers fused and stretched on a substrate, at least the first optical fiber to be interposed with a wavelength selective filter is After carving a guide groove for placing and fixing the optical fiber and placing and fixing the first optical fiber on the acid guide groove,
A distributed coupling type single, characterized in that a cut groove into which the wavelength selective filter is to be fitted is formed in the optical fiber on the guide groove, and the wavelength selective filter is fitted and fixed in the cut groove. A method for manufacturing a mode optical multiplexer/demultiplexer is provided.

Furthermore, according to the fourth aspect of the present invention, a plurality of optical fibers are fused and stretched, and at least a wavelength selective filter is interposed among the plurality of optical fibers fused and stretched on the first substrate. After forming a guide groove for placing and fixing the first optical fiber on the acid guide groove and placing and fixing the first optical fiber on the acid guide groove, the side surface of the first substrate and the first optical fiber are polishing the end surface of the second substrate so that it is flush with the side surface of the first substrate, and carving a second guide groove on the second substrate at a position corresponding to the guide γ register of the first substrate; After placing and fixing the second optical fiber in the second guide groove, the end surface of the second optical fiber is polished so that it is flush with the side surface of the second substrate, and the first optical fiber is A method for manufacturing a distributed coupling single mode optical multiplexer/demultiplexer is provided, which comprises butt-connecting an end face of a fiber and an end face of the second optical fiber with the wavelength selective filter interposed therebetween.

(Function) Crosstalk can be reduced by integrally interposing a wavelength-selective filter in the optical fiber that constitutes the optical multiplexer/demultiplexer, and insertion loss can be reduced by interposing the wavelength-selective filter. The increase in insertion loss is suppressed to a minimum.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a two-wavelength optical multiplexer/demultiplexer. Reference numeral 1 is an optical multiplexer/demultiplexer, and the first optical fiber 2 and the first optical fiber 2 of this optical multiplexer/demultiplexer 1 are 2 optical fiber 3 2
Wooden optical fibers (each with an outer diameter of 125 μm and a core diameter of 10 μm)
m) are bonded by a known fusion drawing method. These optical fibers 2.3 have two wavelengths λ1 (e.g.
The length of the fused portion 4 is optimized so as to obtain required characteristics such as insertion loss when dividing and combining wavelengths 1.3 μm) and λ2 (for example, 1.55 μm). The ends 5a and 6a of the first and second optical fibers 2 and 3 on the left side in the figure are called the first port and the second port side, and the ends 5b and 6b on the right side in the figure are called the third port side. This will be referred to as a port and a fourth port side. Then, the third optical fiber of the first optical fiber 2
near the port side end 5b of the second optical fiber 3 and the fourth
A wavelength selective filter 7 is provided near the port side end 6b of each
．． 8 are interposed at a predetermined angle (for example, 8°) with respect to the central axis of each optical fiber 2.3.

A wavelength selective filter 7 interposed on the first optical fiber 2 side has a property of transmitting an optical signal of wavelength λ1 and reflecting an optical signal of wavelength λ2, and a wavelength selective filter 7 interposed on the second optical fiber 3 side The optical filter 8 has a characteristic of transmitting an optical signal having a wavelength λ2 and reflecting an optical signal having a wavelength λ1.

From the first port side to the first optical fiber 2, the wavelength λ1. λ
When the optical signal of the second optical fiber is inputted, most of the optical power of the optical signal with the wavelength λl propagates through the first optical fiber 2 as it is due to the wavelength selectivity of the fusion part 4, but some of the optical power is transferred to the second optical fiber. Most of the optical power of the optical signal having the wavelength λ2 propagates to the optical fiber 3 and propagates to the second optical fiber 3, while a part of the optical power propagates through the first optical fiber 2 as it is. At this time, the crosstalk at the fused portion 4 is about -17 dB. However, due to the wavelength selectivity of the wavelength selective filter 7.8 interposed in each optical fiber 2.3, the wavelength selective filter 7 interposed on the first optical fiber 2 side reflects the optical signal of wavelength λ2. Therefore, only the optical signal with the wavelength λ1 is emitted to the third port side of the first optical fiber 2, and the wavelength selective filter 8 interposed on the second optical fiber 3 side outputs the optical signal with the wavelength λ1.
Since the optical signal of wavelength λ2 is reflected, only the optical signal of wavelength λ2 is emitted to the fourth port side of the second optical fiber 3. As described above, crosstalk is expected to be reduced by 30 dB or more by the wavelength selective filters 7.8 interposed near each end 5b, 6b of the first and second optical fibers 2, 3. The crosstalk characteristics of the duplexer can be improved to -47d8 or higher. Further, since each wavelength selective filter 7.8 is inclined at a predetermined angle with respect to each optical fiber 2.3, the reflected light reflected by the wavelength selective filter 7.8 is transmitted to the optical fiber 2.3. will be removed from.

Next, a method for manufacturing a two-wavelength optical multiplexer/demultiplexer 1 as shown in FIG. 1 will be described.

2 to 4 show a first method of manufacturing an optical multiplexer/demultiplexer according to the present invention. First, a mounting board 10 as shown in FIG. 2 is prepared. This board 10 is a rectangular block in plan view (for example, 5IIIll+ in height and 40Ilffl in width).
, height 3 mm) 11, and a rectangular hole (for example, 5 vertical 31, horizontal 201, depth 1 m) in the center of the upper surface of the block body 11.
+++) 12, and the four circumferences are bank-like side walls 1
1a, llb and left and right end walls 11c.

A lid is formed to surround the rectangular hole 12.

The left end wall 11C has an end portion 5a of each optical fiber 2.3 of the optical multiplexer/demultiplexer 1 shown in FIG. 6
a guide groove (for example, depth 140 μm
, groove wall inclination angle of 60° on both sides) 13a and 13b are carved in a V-shaped cross section. A side wall 11a is provided on the right end wall lid so as to cross the right end wall lid similarly to the left end wall 11c.

11b, the ends 5b, 6b of each optical fiber 2, 3 of the optical multiplexer/demultiplexer l shown in FIG. Two guides iJ$13c and 13d to be placed are carved with a V-shaped cross section.

On the other hand, each end portion 5b, 6b of the fused and stretched first and second optical fibers 2, 3 of the optical multiplexer/demultiplexer 1 is cut at a position where the wavelength selective filter 7.8 is interposed. , each end face 5c, 6c is obliquely polished to the predetermined angle to form an inclined end face.

Each end portion 5a, 5b of each optical fiber 2.3 is arranged such that each inclined end surface 5C and 6C is disposed approximately at the center of the guides 113c and 13d of the substrate 10.

5a and 5b are placed on the corresponding guides 413a-13d and fixed (see FIG. 3).

Next, optical fibers 2a and 3a are prepared to connect the end surfaces 5c and 6c of the optical fibers 2 and 3 to the third and fourth ports, respectively, and each end surface 5c of each optical fiber 2a and 3a is prepared.
d and 6d are obliquely polished so as to match with the end faces 5c and 6c, respectively, and the end face 5d is provided with a wavelength selection filter 7 that transmits the wavelength λ1 and reflects the wavelength λ2, and the end face 6d is provided with the wavelength selection filter 7 that transmits the wavelength λ1.
A wavelength selection filter 8 that reflects the wavelength λ2 and transmits the wavelength λ2 is formed by vapor deposition. Then, the end surface 5d of the optical fiber 2a formed with the wavelength selection filter 7 is connected to the end surface 5C of the optical fiber 2, and the end surface 6d of the optical fiber 3a formed with the wavelength selection filter 8 is connected to the end surface 6C of the optical fiber 3. Butt bonding and bonding using an adhesive that also serves as a refractive index matching agent
(see FIG. 4), the optical multiplexer/demultiplexer 1 is realized.

FIGS. 5 and 6 show the second part of the optical multiplexer/demultiplexer according to the present invention.
First, a mounting board 10 as shown in FIG. 2 is prepared in the same manner as the first @th manufacturing method, and fusion and extension are performed on each guide groove 13a to 13d of this board 10. Each end 5a, 5 of the first and second optical fibers 2 and 3
Place and fix b, 6a, and 6b. And the first and second
The upper surface of the right end wall lid on which the optical fiber 2.3 of A cut groove (for example, depth 300 μm, width 40 μm) 14 is formed in each optical fiber 2.
The ends 5b and 6b of each optical fiber are formed to be inclined at a predetermined angle in the axial direction of each optical fiber. Then, the wavelength selective filter 7 is fitted in the cut groove 14 at a position crossing the first optical fiber 2, and the wavelength selective filter 8 is fitted in a position crossing the second optical fiber 3. The optical multiplexer/demultiplexer 1 is realized by embedding and fixing with an adhesive or the like which also serves as a refractive index matching agent (see FIG. 5).

FIG. 7 shows the third manufacturing method of the optical multiplexer/demultiplexer l according to the present invention. First, like the first and second manufacturing methods, the mounting board lO Prepare each guide groove 13a of this substrate 10.

The ends 5a, 5b, 6a, and 6b of the first and second optical fibers 2 and 3, which have been fused and drawn, are mounted and fixed on the optical fiber 13d. and the ends 5 of the first and second optical fibers 2.3.
b and 6b i! The outer surface lie of the right end wall lid placed in the second position is polished obliquely at a predetermined angle with respect to the axial direction of each optical fiber, together with the first and second optical fibers 2.3. Next, a block body 20 having the same vertical length and height as the substrate 10 and an appropriate horizontal length is prepared, and on the upper surface 21 of this block body 20, guide grooves 13c and 13d of the substrate 10 are formed with the same cross-sectional shape, respectively. In addition, guide grooves 22 and 23 are formed to be spaced apart by the same distance, and an optical fiber 2b whose one end is connected to the third port is placed on the guide groove 22.
Optical fibers 3b, one end of which is connected to the fourth port, are placed and fixed on each of the optical fibers 3b. And block 20
, the side surface 24 opposite to the outer surface lie of the group +fi, lO
and the other ends of each of the optical fibers 2b and 3b are polished at a predetermined angle so as to align with the outer surface lie.

Then, for example, the outer surface l of the substrate 10 is attached to either the outer surface lie of the substrate 10 or the side surface 24 of the block body 20.
ie, the wavelength selective filter 7 is formed on the end face of the first optical fiber 2 and the wavelength selective filter 8 is formed on the end face of the second optical fiber 3 by means of tricks or the like, and then the substrate is The outer surface 11e of 10 and the side surface 2 of block body 20
4 are butted and fixed so that the core of the first optical fiber 2 and the core of the optical fiber 2b are aligned with the core of the second optical fiber 3 and the core of the optical fiber 3b, respectively (see FIG. 7), and optical multiplexing is performed. A duplexer 1 is realized.

In each of the above-mentioned three manufacturing methods, the fused and stretched portion 4 of the optical fiber is molded with a molding agent such as a synthetic resin (for example, Epotec 301) and then repaired, and then the wavelength selective filter is attached. etc., a mounting board 10" as shown in FIG. 8 may be used. More specifically, after fusion-stretching the first and second optical fibers 2.3, Only the stretched portion 4 is molded with an appropriate molding agent, and the fused stretched portion 4 is embedded in a mold 20 solidified into a rectangular parallelepiped block.Then, a hole is made in the center of the upper surface of the mounting board 10° as shown in FIG. The mounting board l shown in FIG.
The rectangular hole 12 of O has a longer length in the vertical direction (the length between the side wall 11a' and the side wall 11b'). It is sufficient to fit it into the hole 12".

It goes without saying that the structure of the substrates 10 and 10'' is not limited to that of the above-mentioned embodiments, but may be any structure as long as it has the same function as the above-mentioned function when producing an optical multiplexer/demultiplexer.

Further, in the above embodiment, a two-wavelength optical multiplexer/demultiplexer was explained as an example, but it goes without saying that the present invention is also applicable to an optical multiplexer/demultiplexer with three or more wavelengths.

(Effects of the Invention) As described in detail above, according to the distributed coupling type single mode optical multiplexer/demultiplexer of the present invention, the optical multiplexer/demultiplexer is configured and a number of fused and stretched optical fibers are connected. Since a wavelength-selective filter is interposed in at least one of the optical fibers, the crosstalk characteristics of the optical multiplexer/demultiplexer can be significantly improved compared to conventional ones.Moreover, the wavelength-selective filter is interposed between the optical fibers. Therefore, the only loss is due to the inclusion of this wavelength selective filter, and compared to the case where the wavelength selective filter is connected to the optical multiplexer/demultiplexer as a separate component, the insertion is much easier. It has various effects such as being able to suppress the increase to a low level and being advantageous in terms of manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the main parts showing the configuration of a distributed coupling type single mode optical multiplexer/demultiplexer according to the present invention, and FIG. A perspective view of the mounting board to be used, FIGS. 3 and 4 are assembly process diagrams showing the first manufacturing method of the distributed coupling type single mode optical multiplexer/demultiplexer according to the present invention, and FIG. FIG. 6 is a partial cross-sectional view along the line VT-V [FIG. 7], and FIG. FIG. 8 is an assembly diagram showing the third manufacturing method of such a distributed coupling type single mode optical multiplexer/demultiplexer, and shows how a fused and drawn optical fiber is fixed to a mold and this is attached to a mounting board. FIG. 1... Optical multiplexer/demultiplexer, 2.3... Optical fiber, 4...
・・Fusion stretching part, 7.8 ・・Wavelength selective filter, 1
0°10'... Mounting board, 13a-13d... Guide groove, 14... Cut groove. Applicant Furukawa Electric Co., Ltd. Agent Patent Attorney Kan Nagado Santsutsu Figure 1 Figure 2 + 1b Figure 4 Figure 5 Figure 6

Claims (7)

[Claims] (1) An optical multiplexer/demultiplexer formed by fusing and stretching a plurality of optical fibers, characterized in that a wavelength selective filter is interposed in at least one of the plurality of optical fibers. Optical multiplexer/demultiplexer. (2) The distributed coupling type single mode optical multiplexer/demultiplexer according to claim 1, wherein the wavelength selective filter is interposed at an angle with respect to the longitudinal axis direction of the optical fiber. . (3) It has two ports on each side with the fused and stretched portion in between, and multiplexes or demultiplexes two optical signals having different wavelengths, or 2. Distributed coupling type single mode optical multiplexer/demultiplexer according to item 2. (4) The distributed coupling type single mode optical multiplexer/demultiplexer according to any one of claims 1 to 3, wherein the fused and stretched portion is molded with a molding agent. (5) A guide for fusion-stretching a plurality of optical fibers, and placing and fixing a first optical fiber among the fusion-stretched optical fibers on a substrate, in which at least a wavelength-selective filter should be interposed. A groove is carved, and the first groove is formed on the guide groove.
An optical fiber is placed so that its end face lies on the guide groove, and the end face of a second optical fiber to be butt-connected to the end face of the first optical fiber is placed on the wavelength selective filter. 1. A method for manufacturing a distributed coupling single mode optical multiplexer/demultiplexer, characterized in that the first and second optical fibers are fixed on the guide groove after butt-connecting with a . (6) A guide for fusion-stretching a plurality of optical fibers, and placing and fixing a first optical fiber among the fusion-stretched optical fibers on a substrate, in which at least a wavelength selective filter should be interposed. A groove is carved, and the first groove is formed on the guide groove.
After mounting and fixing the optical fiber, a cut groove in which the wavelength selective filter is to be fitted is bored in the optical fiber on the guide groove, and the wavelength selective filter is fitted and fixed in the cut groove. A method for manufacturing a distributed coupling single mode optical multiplexer/demultiplexer characterized by: (7) A plurality of optical fibers are fused and drawn, and a first optical fiber among the plurality of fused and drawn optical fibers that is to be interposed with at least a wavelength selective filter is placed on a first substrate. After cutting a guide groove to be fixed and placing and fixing the first optical fiber on the guide groove, the side surface of the first substrate and the end surface of the first optical fiber are aligned with the side surface of the first substrate. A second guide groove is carved on the second substrate at a position corresponding to the guide groove of the first substrate, and a second optical fiber is inserted into the second guide groove. is placed and fixed, the end face of the second optical fiber is polished so that it is flush with the side surface of the second substrate, and the end face of the first optical fiber and the end face of the second optical fiber are polished. A method for producing a distributed coupling type single mode optical multiplexer/demultiplexer, characterized in that the two are butt-connected with the wavelength selective filter interposed therebetween.