JPS59109022A - Optical wave guide circuit - Google Patents

Abstract

PURPOSE:To obtain an optical waveguide circuit simple in structure, small in light loss and suitable for a multiplexer and demultiplexer by providing a V- shaped or W-shaped light waveguide passage having larger refractive index than a base plate in the transparent base plate and exposing both ends and bent parts on the opposed side of the base plate. CONSTITUTION:An optical waveguide passage 12 consisting of W-shaped domain having a refractive index larger than the base plate is provided in the transparent base plate 11 made of glass, plastics etc. The optical waveguide passage 12 has a circular sectional form, and has maximum refractive index at the center. Refractive index decreases toward periphery gradually to refractive index of the base plate 11. Optical fiber 13A is directly connected to both ends and 13B-13E are connected through interference filters 17B-17E at bent parts 12A-12E. When composite light lambda1+lambda2+lambda3+lambda4 is sent to the fiber 13A, monochromatic light of wavelength lambda1-lambda4 is emitted from fibers 13B-13C respectively. Conversely, it is possible to send the light and composit. Thus, an optical waveguide circuit for a multiplexer and demultiplexer simple in structure and small in light loss can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a leading waveguide, and more particularly to an optical waveguide suitable as an element constituting a demultiplexer/multiplexer or a branch/combiner.

Optical demultiplexers and multiplexers are important devices in optical communication systems.

Conventionally, a demultiplexer that separates mixed light of 3 to 1 different wavelengths into single wavelength light uses an interference filter, and
As a demultiplexer capable of multiplexing the /Q wave to a large degree, a demultiplexer using a diffraction grating is used. This is because when using interference filters, the structure of the demultiplexer becomes more complex as multiplexing increases.

For example, as shown in the figure, a demultiplexer using an interference filter has a refractive index distribution in which the refractive index is maximum at the central axis and decreases unevenly toward the outer circumferential surface.
A pair of wedge-length gradient refractive index lenses /// are joined with their central axes aligned through an interference filter film, and a plurality of such single demultiplexing elements 31, 3B are arranged with their axes shifted from each other. Join each element, ? A...? B interference) Filters 2A and 2'f3 each have a specific wavelength λ1. By using a filter that reflects λ2 and transmits light of other wavelengths, seven optical transmission fibers can be constructed.
The wavelength λ1. transmitted through lA. λ2. The mixed light of λ3 is transmitted through optical transmission fibers connected to each demultiplexing element 3A, 3B.
IB.

1. +D to a single wavelength λ1. λ2. A branching filter that extracts light of λ3 is known.

When constructing a demultiplexer that separates the 3 to 1 waves using this method, it is necessary to connect the lens systems in series with their optical axes shifted, which not only complicates the structure and makes assembly difficult.
There is a problem in that one end of the incident light transmission fiber connected to the lens is not a point light source and the optical loss is relatively large due to the aberration of the lens.

In addition, as shown in the diagram, a triangular prism stand S is bonded to a pair of parallel planes A and B of the transparent substrate A, and a gradient index lens with a Kupinoch length and an incident light transmission fiber block are attached to the triangular prism stand S. A and connect this fiber 414
The light transmitted by the lens is converted into parallel light by a lens and is incident obliquely into the substrate 6, and a prism stand S and a refractive index distribution type are placed on the opposite surface 6B of the substrate and at the reflection position from this surface, respectively, in the same manner as above. Connect the lenses and attach each prism...
A specific single wavelength λl is applied to the interface between ... and the substrate A.
, λ2゜λ3. An interference filter having the property of transmitting light of λ4 and reflecting light of other wavelengths is interposed, and the wavelengths transmitted through each filter are λl, λ2. Each light of λ3゜λ4 is passed through a lens/...
Optical transmission fiber 'i'B, 4'O, l connected to...
A duplexer that extracts signals by ID and IIE is known.

Similar to the one in Fig. 7, in the demultiplexer with the above structure, as the multiplicity of wavelengths to be separated increases, the light beam emitted from the optical transmission fiber is not a point light source and the aberration of the lens causes the light beam to pass through the substrate glass. As the beam spreads as it propagates, there is a problem in that extra optical loss increases.

Further, as shown in FIG. 3, the fiber 7A that transmits the mixed light is cut at the +j0 plane, and a specific wavelength λ1. λ2゜・・
Interference filter that reflects the light of...-1! A
+ -2B... are interposed, and each wavelength λ reflected by these interference filters, 2A, lJ'B...
1. A fiber that transmits light of λ2.../<-
7B, 7G...... Mixed optical transmission fiber 7
A duplexer connected to the side of A is known.

In the above structure, the remaining wavelength light extraction fiber is connected in the axial direction to the mixed optical transmission fiber 7A.
Although the insertion loss when transmitted to 7D is relatively small, the beam is diffused when reflected into the fibers 7B, 7G, etc. connected to the side, so there is still a problem that the insertion loss becomes large. .

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to provide an optical waveguide circuit which is simple in structure and has low optical loss and is suitable as an element for configuring a demultiplexer/multiplexer.

The optical waveguide circuit of the present invention, which achieves the above object, has a transparent substrate formed in a substantially single V-shape or a zigzag shape in which two or more 7-shapes are connected in plan view, and has a refractive index higher than that of the substrate. A continuous light guide path is provided, and both ends and bent portions of the light guide path are exposed on opposing sides of the substrate.

When the circuit of the present invention is used as a demultiplexer/multiplexer, the end of the incident light transmission fiber is directly connected to one end of the light guide exposed on one surface of the substrate, and the other end of the light guide and the bent part are An interference filter that transmits light of a predetermined ni-wavelength is provided on the substrate surface, and the ends of optical transmission fibers that transmit the extracted light of each wavelength are connected thereto.

Instead of providing the interference filter on the substrate surface, it may be provided on the 'Atf surface side of the reporter fiber that is bonded to the substrate surface.

Further, in the present invention, the light guide path embedded in the substrate may have a uniform refractive index distribution within the entire cross section of the light guide path, or as shown in the embodiments described below. It may have a refractive index gradient such that the refractive index is maximum at the center and gradually decreases toward the outer periphery. In the case of the former, which has a uniform refractive index distribution, the light travels through the light guide while undergoing repeated total reflection at the interface between the light guide and the bulb part of the substrate that surrounds it; Within the light guide path, light travels in a sine curve.

The demultiplexer/multiplexer using the optical waveguide circuit of the present invention only needs to directly connect the optical transmission fiber to the surface of the substrate on which the interference filter is provided on the main part of the surface. Since there is no need for a lens to convert light into parallel light, the structure can be made extremely simple, and the number of bonding interfaces is also much smaller than in conventional products, so optical loss at the bonding interfaces can be kept small.

Furthermore, since the diffused output light from the fiber is transmitted to one end of the demultiplexed light extraction fiber through a light guide path that has the same optical transmission function as the optical transmission fiber provided in the substrate, it is possible to reduce the number of bonding interfaces mentioned above. Together, the overall optical loss is greatly reduced compared to the conventional method, and a high-noise, high-precision nine-wavelength multiplexer can be constructed.

The leading wave circuit of the present invention is an optical branching/combining device that splits transmitted light based on light intensity rather than wavelength, in addition to the splitting/multiplexing device.

It can be used as a component of various optical devices such as an optical switch element and a magnetic sensor.

Hereinafter, embodiments of the present invention shown in the drawings will be described in detail.

FIG. 1 shows a plan view of a duplexer using a waveguide circuit according to the present invention, and FIG. 5 shows a sectional view taken along the line v-■ in the Oda diagram.

In the figure, 70 is an optical waveguide circuit according to the present invention, which is a parallelepiped transparent substrate made of glass, plastic, etc.
A continuous light guide path 7.2 is provided inside the substrate parallel to the substrate surface and in a W-shape when viewed from above, which is made up of a region having a refractive index lower than that of the substrate.

The cross section of this light guide path /2 is approximately circular, and for example, the refractive index no at the center of the cross section is maximum, and the refractive index gradually decreases from the center to the periphery, and at a position sufficiently far from the center, the refractive index no. A refractive index gradient is provided that is the same as the refractive index n'' of /.

One end of the light guide path /2, 2A is exposed on one side surface //A of the pair of parallel sides of the substrate //A, //B, and after that, the light guide path /2 is bent in the middle. Part/, 2B,
/, 2C, /, 2D and the other end /2E are alternately exposed to a pair of parallel sides //B, //A of the substrate, respectively.

Each bending part of the light guide path /,2 /jB, /,20,
/, 2D, and 72E, the inclination angle θ of the light guide with respect to the normal to the side surface of the substrate is all set to the same angle.

Then, at the light guide end 7.2A on the side surface of the embedded planar waveguide 10 having the above structure, a core part /j having a diameter approximately equal to the diameter of this light guide /2 and a low refractive index cladding /B surrounding this core part /j are formed. The end face of the input optical fiber /3A is cut obliquely so that the axes of the core part /S and the light guide path 7.2 coincide with each other, and the optical fiber /3A is joined with an adhesive or the like.

Another light guide! 2 (D each bending part/, 2B, /, 2G
l/, 2D, /, 2E also -F end/
With the same diameter as 2A, expose it on the side of the board, and bend the bent part 7 of the
．． On the substrate surface of 2B, an interference filter film/773 that has the property of transmitting light of a specific wavelength λ1 and reflecting light of other wavelengths is provided by vapor deposition on the substrate, and the tip is filtered through this filter film/7B. Obliquely cut fiber/? The same structure as A is provided with an interference filter film /7Q that transmits light with wavelength λ2 and reflects light of other wavelengths, and the tip is obliquely cut through this filter film /7c. 2E is an interference filter film that transmits light with a wavelength of λ3 / 7D, and the other end of the light guide path 12 / 3D is an optical transmission fiber that transmits light with a wavelength of λ3 / 7E. Connect fiber/3E.

In the above device, a wave of 1λ1°λ is transmitted to the fiber 73A.
2. λ3. When a light mixture of each single wavelength light of λ4 is sent, light of wavelength λ1 is extracted from the fiber /3B opposite to this fiber /3A, and the light of wavelength λ1 is extracted from the fiber /3c.

/3D and /3E each have a wavelength λ2. λ3. It is possible to extract 1li-wavelength light of λ4.

Contrary to the above, 7 fiber/3Bx/3Gr/3D, /3
E through wavelengths λl, λ2 . λ3. By sending the light of λ4, the fiber /3A becomes λ] + λ2
Mixed light of 10 λ3+λ4 can be extracted. It goes without saying that the above-mentioned demultiplexer/multiplexer can be applied to both multimode fibers and single mode core fibers.

FIG. 6 shows another embodiment of the invention.

In this example, a pair of leading wave circuits IOA and 10B having the same structure as the previous example are connected and separated, except that the shape of the light guide path /, 2 in the transparent substrate // is a single 7-shape in plan view. An example of a wave/combiner configuration is shown below.

In other words, the optical fiber 73A is cut obliquely at the tip with the optical axis aligned at both ends of the optical guide path /2 of the optical waveguide circuit IOA.
/3B respectively.

Further, on the exposed surface of the light guide bending portion 7.2B of the waveguide circuit 10A, there is provided an interference film/film A having a property of reflecting light of wavelength λ1 and transmitting light of other wavelengths. One end of the light guide path /, 2 of another optical waveguide circuit 10B is connected therebetween.

In addition, the light guide bending portion/, 2B of the above-mentioned off waveguide circuit 10B
is connected to an optical fiber through an interference filter film that reflects light of wavelength λ2 and transmits light of other wavelengths.
3C is connected to the other end of the light guide path/2, and an optical fiber/3D is connected to the other end of the light guide path/2 without intervening an interference filter film, with its optical axis aligned with the light guide path.

In the above device, λ1゜λ2 is passed through the fiber/JA.
．． Waveguide circuit 1 of OI transmits the mixed light obtained by mixing the single wavelength light of λ3.
When introduced into 0A, light of wavelength λ1 is reflected by fang/nofilter membrane/gA and extracted through fiber/3B. In addition, the mixed light of λ2 and λ3 that has passed through the filter film /gA is transmitted through the light guide path /2 of the second waveguide circuit 10B and reaches the OFF initial filter film /gB, where the light with the wavelength of λ2 is transmitted. is reflected and extracted through a fiber/3D connected to the other end of the light guide 7.2.

Further, the wavelength light of λ3 transmitted through the filter film /gB is extracted through the fiber /30.

In this way, the mixed light of wavelengths λ1, λ2λ3 can be separated into each single wavelength light.

Also, contrary to the above, λ1. λ2. λ], λ2 . A mixture of λδ and λδ can be taken out.

The off-line diagram does not show an example in which the optical waveguide circuit of the present invention is applied to an optical switch; optical switch 2Q is a pair of optical waveguide circuits of the present invention, 2/A.

, 27B are placed as objects, and the liquid crystal 2.2 is sandwiched between them and joined together as a pair, and each waveguide circuit, 2/A,...! Optical fibers, 23A, 23B at each end of the light guide path /2°/2 of /B
, 230.23D are connected.

The optical waveguide circuit /A, , 2/B has a light guide path /2 formed in a transparent substrate made of glass, plastic, etc., having a region having a refractive index lower than that of the substrate, and is formed in a symmetrical V-shape in plan view. A bent portion /2B is exposed on the side surface thereof, and both corner portions of the opposite side surface of the substrate are formed into a corner surface 211.2 that is perpendicular to the axis of the light guide path 7.2. ．． 2'l, and both corner surfaces, xl
The ends of optical fibers 23 and 23B are connected to /, iq, respectively, with their optical axes aligned with light guide path /2.

Then] Optical fibers 23C and 3D are connected to both corner surfaces of the other leading waveguide 2/B having the same structure as in Section 2. It has a structure in which the curved parts are arranged facing each other so as to butt against each other, and a layer of liquid crystal 2- is provided between them with a sole around the periphery, and is joined and integrated.

Although not shown in the figure, a transparent conductive film is formed on the substrate surface of both circuits 2/ and 2/B that sandwich the liquid crystal 22.
The voltage application can be controlled externally.

In the above device, with the liquid crystal 2.2 in a transparent state, J = i
j, γ6 transmitted through fiber 23A is transmitted to 7-eye l<-, 23D, and fiber 23c
The light transmitted through the fiber 23 in the opposite position
It is transmitted to B.

Furthermore, when the liquid crystal 2.2 is made opaque, the light from the fiber 23AIJ) is reflected by the light guide bending part 72B and enters the fiber 23B, while the light from the fiber 23G
The light from is reflected and enters the fiber 23D connected to the same substrate.

The optical switch function is performed as described above.

Next, an example of a preferred method for manufacturing the optical waveguide circuit of the present invention is shown in a diagram.

In the diagram, the surface of the glass substrate 3 is covered with a mask 3-2 made of a substance that has a permeation blocking effect against diffused ions, and a part of the mask 32 is aligned with the planar pattern of the waveguide to form, for example, a figure 7 shape. An aperture 33 is provided, and the mask surface is brought into contact with a molten salt 37 containing ions with high electronic polarizability, such as thallium ions, as shown in FIG. By applying an electric field as shown in FIG. If the width of is made sufficiently narrow, for example, 5 μ or less, the cross section of the high refractive index portion 31 obtained is as follows.
It becomes a semicircle. Next, the mask 32 is removed, and the high refractive index portion 3+! A mask 3 is preferably applied only to the upper surface with a width of 30 to 100% of the width of the high refractive index portion 3 on the substrate surface.
S is placed in contact with the salt that excludes ions with low electronic polarizability, such as sodium ions and (and) potassium ions, the salt and the substrate are heated, and an electric field directed from the mask 35 surface to the opposite side is applied to the salt. When the ions are diffused into the glass portion without a mask, a high refractive index portion 3B having a nearly circular cross section is obtained.

Here, the cross section of the high refractive index portion 3B becomes almost circular because ions with low electronic polarizability diffuse from the periphery of the mask 3S not only outside the mask but also into the glass under the mask. The proportion is small at the central plane F of the mask 35, and the proportion increases at the periphery of the mask, and the portion of ions with high electronic polarization that forms the high refractive index portion 3G is due to the movement of ions in the glass. Since the concentration of ions with high electronic polarizability is lower than that of other parts, the concentration of ions with high electronic polarization is high directly under the center of the mask, and because the depth is deep, the mobility of ions with high electronic polarization in this area is lower than that around the mask periphery. This is thought to be because it is large.

The refractive index distribution of the high refractive index portion B obtained at this stage changes stepwise because it is manufactured by applying an electric field.

Therefore, the substrate is heated to a temperature at which the substrate glass does not undergo thermal deformation, and 7 of the ions with high electronic polarization that form the high refractive index region 3 are surrounding ions with low electronic polarization, that is, the degree of increase in refractive index is small. By interdiffusion with the optical axis, a refractive index distribution is formed in which the refractive index gradually decreases with distance from the optical axis.

In addition, in this process, the cross-sectional shape of the high refractive index portion 3B becomes even closer to a perfect circle.

In the off-line diagram, 3g is a conductive paste layer made of a clay layer and KNO3 in paste form. 39. '10 is an electrode plate, g/ is a molten salt bath, and q is a DC power supply.

Although the case where glass is used as the substrate material has been described above, the guiding waveguide of the present invention can also be manufactured using a synthetic resin substrate.

In this case, a partially polymerized resin substrate is used instead of the glass substrate in Example F, and a monomer that forms a polymer with a higher refractive index than the substrate resin is used instead of ions to be diffused into the substrate. .

In addition to the above, C is used in the production of optical fibers.
Various methods can be used, such as forming a light guide on a quartz substrate using VD technology.
Figures 7 to 3 are longitudinal sectional views showing a conventional demultiplexer/combiner;
The figure is a cross-sectional view taken along the line V-■ in Figure 1, the O-figure is a cross-sectional plan view showing another embodiment of the present invention, and the Off-line view is a cross-sectional plane view showing an example in which the present invention is applied to an optical switch. Diagram, Oza diagram (a)
2) is a cross-sectional view showing step-by-step an example of the manufacturability of the leading waveguide of the present invention, and FIG. It is a front view.

10, IOA, 10B, 2/A, 2/B...
Medium optical waveguide circuit／／、3／・・・・・・・・・Substrate／／
2...Light guide path/, 2 B, /20.
/2D, /, 2F...1 bending part 3 /3A, 4B, /3G, /3D, /3E, 23, 23
B, 23G, 23D...Optical fiber /7A, /7B, /7G, /7D, /7E, /zaA, /zaB ・S...Song...Interference filter membrane 1st Figure 2 Figure 3 Figure 4 Factor 5 +2 12 12 12 Figure 8

Claims (1)

[Scope of Claims] C) A continuous region consisting of a region having a refractive index lower than that of the substrate, in a transparent substrate, in a substantially single 7-shape or in a zigzag shape in which two or more 7-shapes are connected in plan view. 1. An optical waveguide circuit characterized in that a light guide path is provided, and both ends and bent portions of the light guide path are exposed on opposing sides of a substrate. 2. In the claims (e)/(e), different wavelengths are transmitted through the substrate surface at the ends and bent portions of the light guide (
An optical waveguide circuit equipped with a filter film that has reflective properties.