JP3357979B2 - Optical wavelength multiplexer / demultiplexer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength multiplexer / demultiplexer used for optical communication, and more particularly to an optical wavelength multiplexer / demultiplexer which is easy to manufacture and small.

[0002]

2. Description of the Related Art In optical communication, in order to transmit a large amount of information and to enable simultaneous information transmission in both directions,
2. Description of the Related Art An optical wavelength multiplexing method for transmitting light of a plurality of wavelengths through one transmission line is used. The optical wavelength division multiplexing method requires a wavelength multiplexer that combines light of a plurality of wavelengths coming from different transmission lines into one and a wavelength demultiplexer that separates light of a plurality of wavelengths contained in one transmission line. It has been. By using a wavelength multiplexer / demultiplexer that functions both as a wavelength multiplexer and a wavelength demultiplexer, an optical wavelength division multiplexing system can be efficiently configured. A conventional optical wavelength multiplexer / demultiplexer is shown in FIGS. FIG. 10 shows an optical directional coupler type optical wavelength multiplexer / demultiplexer, in which two optical waveguides 11 a, 1
1b are formed close to each other. The two ends of the optical waveguide 11a reach the two end surfaces of the optical waveguide substrate 10, respectively, and face the respective ends of the core 21a of the optical fiber 20a and the core 21c of the optical fiber 20c. Only one of the ends of the optical waveguide 11b reaches the end face of the optical waveguide substrate 10 and faces the end of the core 21b of the optical fiber 20b. Since the optical waveguide 11a and the optical waveguide 11b are close to each other, light energy exchange (distribution coupling) is performed between them. The distance between the optical waveguides 11a and 11b is adjusted so that all of the light of the first wavelength is transferred from one optical waveguide to the other, and the light of the second wavelength is not transferred. Light obtained by mixing the light of the first wavelength and the light of the second wavelength is injected into the optical waveguide 11a through the optical fiber 20a. Among them, the light of the first wavelength shifts from the optical waveguide 11a to the optical waveguide 11b, and the light radiated from the end is injected into the optical fiber 20b.
On the other hand, the light of the second wavelength passes through the optical waveguide 11a as it is, and light emitted from the end opposite to the optical fiber 20c is injected into the optical fiber 20c. As described above, light of two wavelengths in the optical fiber 20a is split into the optical fiber 20b and the optical fiber 20c, respectively, and the optical waveguide substrate 10 functions as an optical demultiplexer. It is also assumed that light of the first wavelength is injected from the optical fiber 20b and light of the second wavelength is injected from the optical fiber 20c into the optical waveguide 11b and the optical waveguide 11a, respectively. Light of the first wavelength travels from the optical waveguide 11b to the optical waveguide 11a while the second wavelength
The light having the wavelength of passes through the optical waveguide 11a as it is. As a result, both the light of the first wavelength and the light of the second wavelength are injected into the optical fiber 20a through the optical waveguide 11a, and the optical waveguide substrate 10 functions as an optical multiplexer. FIG.
Reference numeral 1 also denotes an optical directional coupler type optical wavelength multiplexer / demultiplexer. The optical waveguide 11a is Y-branched to form an optical waveguide 11c, which reaches the end surface of the optical waveguide substrate 10, and the end surface of the optical waveguide 11c faces the end of the core 21d of the optical fiber 20d. Except for this point, there is no difference from FIG. When light obtained by mixing light of the first wavelength and light of the second wavelength is injected from the optical fiber 20a into the optical waveguide 11a, the light of the first wavelength shifts to 11b, and the light of the second wavelength becomes 11a. Is the same as in FIG. The light of the second wavelength is the optical waveguide 11c because the optical waveguide 11a is Y-branched.
Optical fiber 20c and optical fiber 20d
Is injected into. When functioning as an optical multiplexer, not only the optical fiber 20c but also the optical fiber 20d
Can be injected and multiplexed.

FIG. 12 shows a wavelength multiplexer / demultiplexer of a filter insertion type. FIG. 12A shows a plan view and FIG. 12B shows a side view.
The optical waveguides 11a, 11b, 11 are placed on the optical waveguide substrate 10.
c is formed, and the optical filter 30 is inserted and fixed in a groove formed in the longitudinal direction of the optical waveguide substrate 10. The optical waveguide 11a reaches the groove from the left end face of the optical waveguide substrate 10,
It intersects with the groove surface at an angle. The optical waveguide 11b reaches the groove from the left end face of the optical waveguide substrate 10, and the optical waveguide 11a
Is opposite to the normal to the groove surface and intersects the groove surface at the opposite angle. The optical waveguide 11a and the optical waveguide 11b intersect at the groove surface. The optical waveguide 11c extends from the right end surface of the optical waveguide substrate 10 to a groove surface opposite to the groove surface where the optical waveguides 11a and 11b intersect, and intersects with the groove surface so as to be in the extension direction of the optical waveguide 11a. . The optical filter 30 is installed in the groove facing the end where the optical waveguide 11a and the optical waveguide 11b intersect. Furthermore, a core 2 is provided at each end of the optical waveguides 11a, 11b, 11c.
The optical fibers 20a, 20b, 20c are installed such that the ends of 1a, 21b, 21c face each other. Here, the optical filter 30 is prepared so as to reflect light of the first wavelength and transmit light of the second wavelength. Optical fiber 20a
, The light obtained by mixing the light of the first wavelength and the light of the second wavelength is injected into the optical waveguide 11a. Then, the light of the first wavelength is reflected by the optical filter 30, passes through the optical waveguide 11b, and enters the optical fiber 20b. The light of the second wavelength passes through the optical filter 30 and enters the optical fiber 20c via the optical waveguide 11c. In this way, wavelength demultiplexing is performed. Conversely, if light of the first wavelength is passed through the optical fiber 20b and light of the second wavelength is passed through the optical fiber 20c, the multiplexed light will come out to the optical fiber 20a.

[0004]

The conventional wavelength multiplexer / demultiplexer described above has a problem. In the optical directional coupler system, in order to improve the demultiplexing / multiplexing characteristics, the optical waveguide 11 is required.
It was necessary to increase the distance between a and the portion where the optical waveguide 11b was close. For this reason, as the size of the element increases, the loss in the optical waveguides 11a and 11b increases, and the intensity of the demultiplexed and combined light is not sufficient. Further, the relationship between the close distance and the demultiplexing / multiplexing characteristics is extremely delicate. For this reason, light of two wavelengths is not completely separated due to a slight error in the distance, and the wavelength separation characteristic is easily deteriorated. Therefore, it is extremely difficult to manufacture a wavelength multiplexer / demultiplexer having good characteristics. Met. In the filter insertion method, it is necessary to form a groove in the optical waveguide substrate 10, manufacture the optical filter 30 as a separate component, and insert and fix the optical filter 30 in the groove. For this reason, the process is complicated,
It is not suitable for mass production. Moreover, the formation of grooves,
Strict precision is required to fix the filter, and the precision of the groove processing and the angle deviation of the optical filter 30 due to a temporal change during or after the fixing of the optical filter 30 greatly affect the performance.

An object of the present invention is to provide a wavelength multiplexing / demultiplexing device which eliminates the conventional disadvantages, is compact, has high performance , has high coupling efficiency, and is easy to manufacture. According to the present invention, downsizing, high performance, and high coupling efficiency of the wavelength multiplexer / demultiplexer can be achieved . Furthermore, the manufacturing process can be simplified, mass production can be facilitated, and productivity can be improved.

[0006]

SUMMARY OF THE INVENTION Generally, the conventional disadvantages are solved.
In order to determine this, an optical waveguide (11a, 11b) intersecting at the end face is provided on the optical waveguide substrate (10), and a first end face of the optical waveguide substrate (10) intersecting these optical waveguides (11a, 11b) is provided. It is conceivable to provide an optical filter (30) that reflects light of the second wavelength and transmits light of the second wavelength.
Can be The present invention further relates to a fiber and an optical waveguide substrate.
The purpose is to provide a configuration that increases the coupling efficiency.

[0007]

The wavelength multiplexer / demultiplexer according to the present invention can be manufactured without going through the steps of forming grooves that require precision and are difficult to process, and inserting and fixing an optical filter in the grooves.
For this reason, it is possible to provide a wavelength multiplexer / demultiplexer that is easy to manufacture and has high performance .
The coupling efficiency can be improved . Also, look to short optical waveguide, and can be achieved even in size since it reduced the binding moiety.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) FIG. 1 shows a general first embodiment. Optical waveguides 11a and 11b are formed on the optical waveguide substrate 10, and the optical waveguides 11a and 11b reach the right end surface from the left end surface of the optical waveguide substrate 10 and intersect at the right end surface. The ends of the core 21a of the optical fiber 20a and the end of the core 21b of the optical fiber 20b face the left ends of the optical waveguides 11a and 11b, respectively. Optical waveguide 11a, 11b
The end of the core 21c of the optical fiber 20c is opposed to the right end where the optical waveguides 11a and 11b intersect.
An optical filter 30 is provided between the ends of the optical waveguide 1c and on the right end surface of the optical waveguide substrate 10. Here, the optical filter 3
0 reflects light of the first wavelength and transmits light of the second wavelength. Light obtained by mixing light of the first wavelength and light of the second wavelength is injected into the optical waveguide 11a through the optical fiber 20a. This light is separated by the optical filter 30 into reflected light of the first wavelength and transmitted light of the second wavelength, and travels separately to the optical fibers 20b and 20c, respectively. In this way,
Demultiplexing is performed. Also, if light of the first wavelength is injected from the optical fiber 20b and light of the second wavelength is injected from the optical fiber 20c, each light is reflected light and transmitted light is 1 light.
1a, and both are injected into the optical fiber 20a.
In this way, multiplexing is performed.

Various methods can be applied to manufacture the optical waveguide substrate 10. For example, it can be performed by forming a waveguide on a lithium niobate substrate by Ti diffusion. Further, a glass waveguide can be formed on a Si substrate by a flame deposition method. Further, a core layer and a clad layer can be formed from an organic material on a Si substrate to form a waveguide. It is known that any of these methods can utilize a microfabrication technique and can accurately produce a waveguide. As the optical filter 30, for example, an interference filter of a dielectric multilayer film can be used. The installation can be performed by, for example, fixing the separately manufactured optical filter 30 to the optical waveguide substrate 10 as in the conventional example. Further, a dielectric multilayer film can be directly laminated on the end face of the optical waveguide substrate 10 by a film forming method such as vacuum deposition. In this case, the optical filter 3
There is no occurrence of angle shift due to the time 0 is fixed at the time of mounting and change over time. Further, this simplifies the manufacturing process and facilitates mass production. The optical filter 30 can be formed by forming a dielectric multilayer film or the like on the end face of the optical fiber 20c instead of the end face of the optical waveguide substrate 10. In this case, the optical filter 30
And the optical fiber 20c is not displaced, and the optical filter 30 can be formed on a large number of optical fibers 20c at the same time, which is advantageous for mass production. Here, an antireflection film can be formed on the optical filter 30.
By doing so, 1 due to reflection on the optical filter 30
Light loss between 1a and 21c can be reduced. Furthermore, it also prevents that a part of the light of the second wavelength is reflected and enters the optical waveguide 11b and mixes with the first wavelength (crosstalk), that is, prevents the wavelength separation characteristic from being lowered.

[0010]

As a specific example of the optical filter 30, a wavelength 1
An optical filter 30 was designed and manufactured with 300 nm on the reflection side, a wavelength of 1550 nm on the transmission side, and an incident angle of light of 45 °. The fabrication was performed by alternately stacking 47 layers of Ta ₂ O ₅ and SiO ₂ on a glass substrate by vacuum evaporation, and the total number of layers was 1
It was 0.1 μm. As a result, a transmission side isolation value of 1 × 10 ⁻⁴ or less in the wavelength multiplexer / demultiplexer could be achieved. Looking at the relationship of isolation with respect to wavelength, the wavelength range in which the transmission side isolation value is 1 × 10 ⁻⁴ or less is 90 nm in wavelength width (wavelengths 1260 to 1
350 nm). On the other hand, the reflection side isolation at this time does not reach 1 × 10 ⁻⁴ even at the peak value, and is at most about 1 × 10 ⁻² to 1 × 10 ⁻³ , and the isolation value is 1 × 10 ⁻⁴ even in the wavelength range. ^-2 and 15 nm (wavelength 1555 to 1570)
nm). The above materials, the number of layers, and the total film thickness are merely examples, and are values to be designed by those skilled in the art as necessary. For example, if the incident angle of light is small, the number of layers can be reduced and the manufacturing process can be simplified even if the required isolation value is the same. However, even in this case, the isolation value is smaller on the transmission side, and the isolation value can be increased in the wavelength width.

Various methods are used for positioning between the waveguide 11 and the optical fiber 20. For example, by changing the position between the waveguide 11 and the optical fiber 20 while passing light, and detecting a change in the amount of light passing therethrough,
And the optical fiber 20 can be optimally aligned (active alignment). When the optimal alignment is achieved, the waveguide 11 and the optical fiber 2 are maintained in such a state.
What is necessary is just to fix 0. For example, as shown in FIG. 2, an optical adhesive 50 may be used to fix the gap between the waveguide 11 and the optical fiber 20, and this is a first modification. Here, the optical adhesive 5
In the case of 0, the refractive index of the waveguide 11, the optical fiber 20, and the optical filter 30 is taken into consideration, and the refractive index is selected so that the light coupling between the waveguide 11 and the optical fiber 20 is the strongest.
If an optical adhesive having an appropriate refractive index is selected, the waveguide 11,
Connection loss due to light reflection or the like at the end of the optical fiber 20 can be greatly reduced. As a simple means, matching with the refractive index of the core 21 is often performed. Here, it is also possible to use the above-described antireflection film together. In this case, the antireflection film should be designed in consideration of the refractive index of the optical adhesive. The waveguide 11 and the optical fiber 20
Even when the direct connection is not made, the connection loss can be improved by using the refractive index matching material instead of the optical adhesive 50. The refractive index matching material mainly composed of, for example, a silicon-based resin is generally commercially available as a matching oil. As a second modification of the general first embodiment, as shown in FIG.
One that is Y-branched to 1c can be mentioned. FIG. 3 is upside down from FIG. 1, but is substantially the same as FIG. 1 except that the optical waveguide 11b is branched in the Y direction. With this configuration, of the mixed light of the two wavelengths injected into the optical waveguide substrate 10 from the optical fiber 20a, the split light of the first wavelength is transmitted to the optical fiber 20b and the optical fiber 20d.
Can be used by branching. Conversely, when the light of the first wavelength is injected into the optical waveguide substrate 10 and multiplexed, one of the optical fiber 20b and the optical fiber 20d may be arbitrarily selected. Further, FIG. 4 is a general
This is a third modification of the first embodiment , in which a light emitting element 41 and a light receiving element 42 are provided in opposition to the optical waveguide substrate 10 instead of the optical fiber. The light emitting element 41 and the optical fiber 2 for the first wavelength are used instead of the optical fiber 20b of FIG.
The light receiving element 42 for the second wavelength is provided instead of 0c. In this way, light transmission with light of the first wavelength and light reception with light of the second wavelength can be performed simultaneously. The installation of the light emitting element 41 and the light receiving element 42 is the same as in FIG.
This can be performed using an optical adhesive. Here, the optical filter 30
Is laminated on the light receiving element 42,
The advantages in the manufacturing process are the same as those in FIG.

(2) FIG. 5 shows a general second embodiment. Here, the right end surface of the optical waveguide substrate 10 is oblique to the side surface of the optical waveguide substrate 10. In the figure, the optical waveguide 11a is formed parallel to the side surface of the optical waveguide substrate 10. The optical waveguide 11b is composed of the optical waveguide 11a and the optical waveguide substrate 1.
0, and the angle with respect to the normal of the right end face of the optical waveguide substrate 10 is opposite to that of the optical waveguide 11a. The end face of the core 21c faces the right end face of the optical waveguide 11a at an angle so that the optical fiber 20c is on the extension of the optical waveguide 11a. With this configuration, light that has traveled straight from the end face of the optical waveguide 11a can be directly used as the core 21.
c, and conversely, the light emitted from the core 21c goes straight and is injected into the optical waveguide 11a. As a result, light loss between the optical waveguide 11a and the optical fiber 20c can be reduced, and the optical coupling efficiency can be improved. (3) FIG. 6 shows an embodiment of the present invention. Here, the right end face of the optical waveguide substrate 10 is oblique to the side face in FIG. 5, whereas the end face of the optical waveguide where the two optical waveguides intersect is smaller than the outer diameter of the optical fiber. Diagonal in range
To form a triangular wedge. This makes it easier to make the space between the optical waveguide substrate 10 and the optical fiber 20c closer. As a result, general example 2
Furthermore, the efficiency of optical coupling between the optical waveguide 11a and the optical fiber 20c can be improved. As shown in the case of FIG. 2, it is needless to say that the optical coupling can be improved by using the refractive index matching material. Here, the optical waveguide 1
A method for easily performing the alignment between the optical fiber 1 and the optical fiber 20 will be described. This is shown in FIGS. FIG. 7 shows an optical fiber fixing substrate 6 to which an optical waveguide substrate 10 and an optical fiber 20 are fixed.
FIG. 0 is a perspective view showing a state where the holding plate 70 is joined. FIG. 8 shows the optical waveguide substrate 10 and the optical fiber fixing substrate 60.
9 is a plan view, and FIG. 9 is an enlarged perspective view of the optical waveguide substrate 10 and the optical fiber fixing substrate 60 near the optical filter 30. Although the optical waveguide substrate 10 itself is not different from FIG. 6, it is formed integrally with the optical fiber fixing substrate 60 with the groove 80 as a boundary. The optical fiber fixing substrate 60 has a V-shaped groove 61 for fixing the optical fiber.
Is formed. The one-body structure, for example, a V groove is formed by performing a fine processing to the semiconductor material such as a Si substrate can be created by dicing the thereafter groove 80. The formation of the waveguide 11 can be performed before or after the formation of the V-groove 61. Since the microfabrication technology is used for forming both the V-groove 61 and the waveguide 11, the positioning of the optical fiber can be performed with extremely high precision. In addition, the optical waveguide substrate 1
0, a large number of integrated structures of the optical fiber fixing substrate 60 are formed on a Si substrate and cut off, so that a large number of optical fibers can be mass-produced at a time. The optical fiber 20 can be fixed to the V-groove 61 by, for example, bonding it with an adhesive. Further, by using the holding plate 70 shown in FIG. 7, the optical fiber can be fixed more uniformly. Although not shown in the drawing, this can be achieved by, for example, fastening the optical fiber fixing substrate 60 and the holding plate 70 with screws or the like. This can be used in combination with the above-mentioned fixing with an adhesive. An optical fiber fixing groove 71 is formed in the holding plate 70 where the optical fiber 20 hits. As compared with the case where the optical fiber fixing groove 71 is not provided, the optical fiber 20 comes into contact with the optical fiber 20 over a wider area. As a result, it is possible to maintain good coupling efficiency between all the optical fibers 20 and the optical waveguide 11. In addition, when the optical fiber fixing groove 71 and the protruding portion therebetween are made of an elastic body, the force applied to the optical fiber 20 can be made more uniform, and the coupling efficiency can be improved.

[0014]

The wavelength multiplexer / demultiplexer according to the present invention has a groove,
It can be manufactured without going through the steps of inserting and fixing the optical filter in the groove. Further, no optical waveguide is required between the optical filter and the optical fiber. Further, since an optical waveguide having a long distance close to each other at a minute interval is not required, there is an effect that productivity can be improved by simplifying a manufacturing process and facilitating mass production. Furthermore, the present invention is miniaturization of the wavelength division multiplexer, it is possible to improve the performance
This has the effect of improving the coupling efficiency between the fiber and the optical waveguide substrate .

[Brief description of the drawings]

FIG. 1 is a plan view showing a general first embodiment .

FIG. 2 is a plan view showing a first modification of the general first embodiment .

FIG. 3 is a plan view showing a second modification of the general first embodiment .

FIG. 4 is a plan view showing a third modification of the general first embodiment .

FIG. 5 is a plan view showing a general second embodiment .

FIG. 6 is a plan view showing an embodiment of the present invention .

FIG. 7 is a perspective view illustrating an alignment method of an optical fiber.

FIG. 8 is a plan view showing an integrated structure of an optical waveguide substrate and an optical fiber fixing substrate.

FIG. 9 is an enlarged perspective view of a part of FIG. 7;

FIG. 10 is a plan view showing a first conventional example using a directional coupler system.

FIG. 11 is a plan view showing a second conventional example using a directional coupler system.

FIG. 12 is a diagram showing a conventional example using a filter insertion method.

[Explanation of symbols]

 10: Optical waveguide substrate 11, 11a, 11b, 11c: Waveguide 20, 20a, 20b, 20c, 20d: Optical fiber 21, 21a, 21b, 21c, 21d: Core 30: Optical filter 41: Light emitting element 42: Light Light receiving element 50: Optical adhesive 60: Optical fiber fixing substrate 61: V groove 70: Holding plate 71: Optical fiber fixing groove 80: Groove

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-223705 (JP, A) JP-A-4-175705 (JP, A) JP-A-5-60941 (JP, A) JP-A-9-99 73019 (JP, A) JP-A-10-1345 (JP, A) JP-A-10-160962 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/12, 6 / 293,6 / 30

Claims (3)

(57) [Claims] 1. An optical wavelength multiplexer / demultiplexer for multiplexing or demultiplexing light of a plurality of wavelengths , comprising an optical waveguide substrate (10), provided on the optical waveguide substrate (10), and at least one intersecting with the end face light guide (11a, 11b) of the optical <br/> waveguide substrate (10) includes two, said two optical waveguides (11a, 11b) optical waveguide end faces which intersect provided And reflects the light of the first wavelength to produce the second light.
Has an optical filter that transmits light of a wavelength (30), said optical guiding the front <br/> SL two optical waveguides (11a, 11b) intersect
The size of the waveguide end face is smaller than the outer diameter of the optical fiber.
Characterized by being formed obliquely with respect to the side surface of the optical waveguide substrate. 2. The optical wavelength multiplexer / demultiplexer according to claim 1, wherein a V-groove is formed, and an end of the V-groove is formed in the optical waveguide (1).
An optical wavelength multiplexer / demultiplexer further comprising: an optical fiber fixing substrate facing the end of 1a) ; and an optical fiber fixed on the V-groove. 3. A optical wavelength demultiplexer according to claim 2, the optical wavelength multiplexing and demultiplexing, characterized in that it is one body formed by the optical waveguide substrate and the optical fiber fixing substrate Si group Version vessel