JPH11326660A - Optical branching filter and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-loss optical branching filter by coupling optical elements with each other through optical waveguides and a process for producing the same. SOLUTION: Translucent mirrors 21, 22, 23 respectively varying in reflectivity are erected within a case-like substrate 40. This substrate is immersed into a photosetting resin solution and short wavelength light is introduced from a light inlet port 41 to cure the resin along an optical route and to form the optical waveguides. The inside of the case-like substrate 40 is thereafter packed with a resin of a low refractive index, and the resin is cured. As a result, the optical branching filter of which from the light inlet port 41 to respective exit ports 50 are coupled by the optical waveguides is formed. The light introduced into the light inlet port 41 propagates in the optical waveguides and does not, therefore, diffuse. The light loss by diffusion is thereby obviated. Since the optical branching filter is molded integrally, there is no loss due to the misalignment thereof. Then, the light loss is lessened, and in addition, an assembly cost and parts cost are drastically reduced and the inexpensive optical branching filter can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical demultiplexer using an optical waveguide. In particular, by filling the photocurable resin between a plurality of semi-transparent mirrors, and by injecting short-wavelength light through the plurality of semi-transparent mirrors, the photo-curable resin is cured in the optical axis direction,
The present invention relates to an optical demultiplexer for integrally forming an optical waveguide and a semi-transparent mirror in close contact with each other, and a method for manufacturing the same. INDUSTRIAL APPLICABILITY The present invention can be applied to an inexpensive and low-loss optical demultiplexer / multiplexer in the wavelength division multiplexing optical communication field.

[0002]

2. Description of the Related Art In recent years, there has been developed an optical demultiplexer for outputting light of each wavelength component from wavelength multiplexed light incident on one optical fiber. These are mainly optical elements in which a plurality of interference filters having different selected wavelengths are connected.
There is one disclosed in Japanese Patent Application Laid-Open No. 1-270709. Briefly, as shown in FIG. 8, the glass blocks 102 cut obliquely are arranged in a line so that the cut inclined surfaces are opposed to each other in parallel, and different between the inclined surfaces. An interference film filter for selecting light having a wavelength is interposed and closely attached.

For example, light 114 on which wavelengths λ ₁ ,..., Λ ₅ are superimposed is a rod lens 10 which is an optical waveguide on the incident side.
8, the first interference film filter 103
The light of λ ₂ ,..., λ ₅ is reflected, and only the light of wavelength λ ₁ is transmitted. Then, only the light having the wavelength λ ₁ is output to the outside via the rod lens 109 which is the optical waveguide on the emission side. On the other hand, λ ₂ reflected by the first interference film filter,.
, Λ ₅ is reflected by the second interference film filter 104 at the wavelength λ ₂ , and the third interference film filter 105
Light of the wavelength lambda ₃ is reflected, respectively, are outputted to the outside through the rod lens 110, 111 at. Other wavelength components are selected according to the same principle and output to the outside.

[0004]

A conventional optical demultiplexer is configured using an interference film filter. As shown in FIG. 9, in principle, the interference film filter selects wavelengths based on multiple interference of light, that is, a kind of equi-tilt interference. The interference condition of equitilt interference is that the wavelength of reflected light is λ
_i , the refractive index of the multiple reflection plate is n, the thickness is d _i , and the incident angle is θc, and the interference condition is mλ _{i where} m is an integer.
= 2nd _i cos θc. That is, the wavelength to be reflected is determined strictly the thickness d _i of the multiple reflection plate by the incident angle .theta.c. For example, taking the wavelength multiplexing light incident at a common angle of incidence θc thereto a multilayer film 104 having a thickness d ₂ as an example, as shown in FIG. 9, the interference condition only that conditions the light of the wavelength lambda ₂ The wavelength λ ₂
Is reflected, and the other wavelength components are transmitted. However, the light emitted from the optical fiber exit end has a divergence angle △
Since it has θ, the emitted light cannot be directly incident on this optical demultiplexer. This is because the above interference condition cannot be satisfied for all the outgoing lights having the divergence angle 一部 θ, and a part of the light is transmitted as shown by the dotted line in the figure. Therefore, it becomes an inefficient optical demultiplexer.
The area of the laser beam passing through the exit is proportional to the spread angle △ θ and the diffusion distance to the exit. As the diffusion distance increases, the loss due to the restriction of the exit increases. Therefore, usually, an expensive rod lens is required as an incident waveguide or an exit waveguide.

[0005] The interference film filter is formed on an optical prism-shaped glass block precisely cut out at an angle of 45 degrees with respect to the optical axis and assembled. Therefore, it becomes a very expensive optical element. Further, a deviation between the optical axis of the rod lens and the optical axis of each reflected light also occurs as an assembly error. This has a great effect on the propagation loss of light. Therefore, it did not become a low-loss optical demultiplexer.
Further, in order to avoid this loss, more precise assembly is required, resulting in a great increase in cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to connect an optical inlet, a specific wavelength separating means, and an output port with an optical waveguide, and to perform optical demultiplexing with less optical loss. Is to provide equipment. Another purpose is to make the optical waveguide and the specific wavelength separating means integrally in accordance with the actual use situation, so that the optical loss is small,
An object of the present invention is to provide an inexpensive manufacturing method in which assembly costs and parts costs are significantly reduced.

[0007]

In order to achieve this object, an optical demultiplexer according to claim 1 of the present invention comprises:
An optical demultiplexer that separates wavelength-multiplexed light into each wavelength component by a plurality of filters and outputs the separated light of each wavelength component to the outside, and has a case shape having a light inlet and a plurality of outlets. The substrate, at a predetermined angle with respect to each incident light in the case-shaped substrate, a plurality of specific wavelength separation means erected so as to be connected to the plurality of exits, the first from the light inlet A first optical waveguide that is formed in close contact with the specific wavelength separating unit, and is formed in close contact between the plurality of specific wavelength separating units;
A second optical waveguide for guiding and transmitting the light transmitted by the specific wavelength separating means to the adjacent specific wavelength separating means, and filling the case-shaped substrate with the first and second optical waveguides and the specific wavelength separating means embedded therein Low refractive index light transmitting resin.

As described above, the optical demultiplexer having the above structure has a structure in which the optical waveguide is formed in close contact from the inlet to the outlet, and the periphery thereof is filled with a low refractive index light transmitting resin. . Therefore, the optical waveguide is a step index type optical waveguide. Therefore, the wavelength-multiplexed light introduced into the waveguide is totally reflected in the waveguide and propagates without being diffused. The wavelength-division multiplexed light introduced from the light introduction port propagates through the first optical waveguide and is incident on the first specific wavelength separation means provided upright in the case-shaped substrate. In the specific wavelength separating means, the specific wavelength light is separated and extracted, and a part of the wavelength multiplexed light is transmitted. The transmitted wavelength-division multiplexed light propagates through the second optical waveguide and enters the next specific wavelength separating means. The wavelength multiplexed light transmitted in this way is sequentially incident on each specific wavelength separating means, and the specific wavelength light is separated. Each light separated by each specific wavelength separating means propagates through an optical waveguide constituting a part of the specific wavelength separating means and is output to the outside.

The specific wavelength separating means comprises, for example, a semi-transmissive mirror, a color filter and an optical waveguide connecting them. Part of the wavelength-multiplexed light that has entered is partially branched by the semi-transparent mirror, propagates through the coupled optical waveguide, and enters a filter provided at the exit. Thereby, only the specific wavelength is extracted and output from the exit. Alternatively, the specific wavelength separating means is also formed by, for example, an optical waveguide connected to the specific wavelength reflection filter and the emission port. In that case,
The reflected light of the specific wavelength propagates through the optical waveguide and is output to the outside through the light exit.

The optical demultiplexer according to the first aspect of the present invention has a structure in which a step index type optical waveguide is formed in close contact from the inlet to the outlet. Wavelength multiplexed light propagating in the waveguide is confined in the waveguide and does not diffuse. Therefore, there is no loss depending on the diffusion distance of the incident light, and the optical demultiplexer is efficient. In addition, since the optical waveguide is formed in close contact with the inlet and the outlet, a collimator lens that converts diffused light into parallel light at the inlet and the outlet is not required. Therefore, it becomes an inexpensive optical demultiplexer.

According to a second aspect of the present invention, there is provided a method for manufacturing an optical demultiplexer, wherein a plurality of specific wavelength separating means provided upright in a case-like substrate are surrounded by a liquid or gel monomer during manufacturing. Having. By introducing predetermined short-wavelength light from the light introduction port, a photopolymerization reaction occurs in the liquid or gel-like monomer along the optical axis and is cured. As a result, the first and second optical waveguides and the optical waveguide that guides light, which is a part of the specific wavelength separating means, to the outside are formed. The first and second lights are introduced simply by introducing predetermined short-wavelength light from the inlet.
Are collectively formed, and the light introduction port, the specific wavelength separation means, and the emission port are integrally formed in close contact with each other. Accordingly, there is no optical axis shift between the light entrance, each specific wavelength separating means, and the exit. Therefore, an excellent method for manufacturing an optical demultiplexer having no optical loss due to optical axis shift can be provided. In addition, since a single short-wavelength light is introduced only through the inlet, the light-emitting device can be molded in a lump.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. The present invention is not limited to the following examples. (First Embodiment) FIG. 1 is a sectional view showing the structure of an optical demultiplexer according to the present invention, and FIG. 2 is a front view thereof. In this embodiment, for the sake of simplicity, an optical demultiplexer in which light in which three wavelengths λ ₁ , λ ₂ , and λ ₃ are multiplexed is decomposed into respective components will be described as an example.

An optical demultiplexer according to the present invention comprises: a case-shaped substrate 40 having a light inlet 41 and a plurality of outlets 50 on a side surface;
The specific wavelength separating devices 71, 72, 73, which are the specific wavelength separating means provided on the bottom plate of the case-like substrate 40, are formed so as to connect the light inlet 41 to the first specific wavelength separating device 70. A first optical waveguide 10 and a second optical waveguide 11 connecting the specific wavelength separation devices 70, 71, 72 thereto.
And a low-refractive-index light-transmitting resin 42 filled in the case-shaped substrate.

The case-shaped substrate 40 is formed by molding a resin into a box shape so as to be filled with a low-refractive-index light-transmitting resin 42 later.
Is provided. Specific wavelength demultiplexers 71, 72, 73
Are semi-transparent mirrors 21 and 2 each set to a predetermined reflectance.
2, 23 and a color filter 5 for extracting light of a specific wavelength
A third optical waveguide 12 connecting both 1, 52, 53 and
It is composed of The semi-transparent mirrors 21, 22, 23 are installed at 45 degrees to the respective incident light, and the color filters 51, 52, 53 are installed at the exit 50. That is, the specific wavelength demultiplexers 71, 72, and 73 have a structure connected to the respective output ports 50, and the specific wavelength light is output from the output ports 50. In addition, semi-transparent mirror 2
In order to make the reflection intensities the same, the number of semi-reflective mirrors is N and the reflectivity of the i-th semi-transparent mirror is R.
_Assuming that _i , it is determined by the equation of _Ri = 1 / (N-i + 1).

The optical waveguides 10, 11, and 12 have a structure in which the optical waveguides are closely adhered from the light introduction port 41 to each of the emission ports 50, and are made of polymethyl methacrylate (PMMA) having a refractive index of 1.49. Have been. Further, the periphery thereof is filled or coated with, for example, a Teflon-based low refractive index light transmitting resin 40 having a refractive index of 1.34. Therefore, the optical waveguides 10, 11, and 12 are step index type optical waveguides. The wavelength-multiplexed light introduced into the waveguide propagates while being totally reflected in the waveguide. Therefore, it is propagated without spreading.

Next, a process in which the wavelength division multiplexed light is decomposed into respective wavelength components by the present optical demultiplexer will be described.
The components of the wavelength multiplexed light are respectively λ ₁ = 850 ± 20n
m, λ ₂ = 780 ± 20 nm, λ ₃ = 660 ± 20 nm
It is. The multiplexed light is transmitted from the optical inlet 41 to the fiber 6
When the wavelength component is introduced by 0, each wavelength component is incident on the first specific wavelength separation device 71 while being totally reflected in the first optical waveguide 10. The reflectance of the semi-transparent mirror 21 of the specific wavelength separation device 71 is set to 33% according to the above equation. Therefore, all the wavelength components incident on the specific wavelength separation device 71 are reflected according to the reflectance, propagate through the third optical waveguide 12, and enter the color filter 51. The color filter 51 is an absorption type filter, and has wavelengths λ ₂ , λ
_{The three} components are absorbed. Therefore, it is not transmit only the component of the wavelength lambda _1. Thus, in the specific wavelength demultiplexer 71, only the specific wavelength λ ₁ is separated.

The light transmitted through the specific wavelength demultiplexer 71 propagates through the second optical waveguide 11 and is incident on the adjacent specific wavelength demultiplexer 72. The reflectance of the semi-transparent mirror 22 of the specific wavelength separation device 72 is set to 50% according to the above equation. Accordingly, all the wavelength components of the light intensity (66% of the incident light) incident on the specific wavelength separation device 72 have a light intensity of 33% of the incident light according to the reflectance, and propagate through the third optical waveguide 12 to be colored. It enters the filter 52, similarly lambda ₂
Are separated. The same applies to the specific wavelength separation device 73. However, the reflectance of the last semi-transmissive mirror 23 is a total reflection mirror having a reflectance of 100%. In this way,
In the optical demultiplexer according to the present invention, the wavelength components λ ₁ , λ ₂ , λ ₃ are separated into light of the same intensity by the specific wavelength separation devices 71, 72, 73 connected by the optical waveguide. Light does not diffuse in the optical waveguide. Therefore, there is no loss due to the diffusion distance as in the related art. In the conventional example, an interference film filter is used to separate a specific wavelength component.
In this embodiment, an ordinary inexpensive semi-transparent mirror is used. The reflectivity of this semi-transparent mirror does not depend on the spread angle △ θ as in the prior art. Therefore, branching can be performed efficiently. Therefore, an inexpensive and low-loss optical demultiplexer can be obtained.

(Second Embodiment) FIG. 3 is a sectional view showing the structure of a second embodiment. The feature of the second embodiment is that one optical element replaces the separating function by the semi-transparent mirror and the color filter. The optical element is a so-called two-color filter that reflects / transmits light of a predetermined wavelength or less, is made of a dielectric multilayer film, and is usually called a dichroic mirror. Here, the dichroic mirror 31 is attached to the specific wavelength separation device 71.
The dichroic mirror 32 is used for the specific wavelength separating device 72 and the dichroic mirror 33 is used for the specific wavelength separating device 73.

When the wavelength multiplexed light on which three wavelengths are superimposed similarly enters the optical fiber 60 and the first optical waveguide 10, the dichroic mirrors 31 and 32 are designed to have the transmittance distribution shown in FIG. First, only light having a wavelength of λ ₁ (850 nm) or more is reflected by the dichroic mirror 31, and the remaining lights of λ ₂ and λ ₃ are transmitted. The transmitted light of λ ₂ and λ ₃ is similarly transmitted to the dichroic mirror 32.
Reflects only the wavelength λ ₂ (780 nm), and the last dichroic mirror 33 reflects the wavelength λ ₁ .
Each reflected light component propagates through the third optical waveguide 12 and is output from each output port 50 as in the first embodiment.
Therefore, the optical demultiplexer according to the present embodiment has a smaller number of parts than the first embodiment, and is an optical demultiplexer having high assembling efficiency.
The color filter 50 of the first embodiment is an optical element having a large loss that absorbs other wavelengths. In this embodiment,
Instead, a dichroic mirror that rarely absorbs other wavelengths and separates only light in a specific wavelength region is used. Therefore, light loss due to the optical element is avoided.
Therefore, an optical demultiplexer with lower loss can be obtained.

(Third Embodiment) Next, a method of manufacturing an optical demultiplexer according to the present invention will be described with reference to FIG. The manufacturing method is a so-called stereolithography method using a photocurable resin as a liquid monomer and a short wavelength laser. This liquid photocurable resin includes:
For example, an epoxy-based, acrylic-based, or silicon-based photocurable resin is selected. As a short-wavelength laser for curing, an argon ion laser (λ = 488 nm), a helium cadmium laser (λ = 325 nm), or an ultra-high pressure mercury lamp (λ = 380 nm) is selected.

First, the case-like substrate 40 on which the semi-transparent mirrors 21, 22, and 23 are erected on the bottom plate is immersed in a solution of a photocurable resin. Next, for example, an argon ion laser is introduced from the outside through the light inlet 41 as a short wavelength laser for curing. The introduced short-wavelength laser light 36 is transmitted through the semi-transparent mirror 21 having a reflectance of 33%, the semi-transparent mirror 22 having a reflectance of 50%, and the semi-transparent mirror 2 having a reflectance of 100%.
3, the reflection / transmission is repeated. As a result, the path of the laser light from the light introduction port 41 to each emission port 50, that is, the first optical waveguide 10 and the second optical waveguide 1
The first and third optical waveguides 12 are cured by a photopolymerization reaction, and are formed in a state where the light inlet 41, the semi-transparent mirrors 21, 22, 23, and the respective outlets 50 are in optical contact with each other. When a dichroic mirror is used in place of the semi-transparent mirror, the curing speed differs depending on the above-mentioned route. This is because most of the dichroic mirrors are transmitted because of the short wavelength. That is, curing starts from the transmission path. However, even a dichroic mirror reflects a few percent, so that a similar waveguide is formed at the end. Therefore, this method is effective for both.

After the formation of the optical waveguide, the uncured resin is removed with a solvent such as acetone or toluene. Thereafter, a cladding layer / portion for total reflection in the optical waveguide is formed. The cladding layer / part is made of a resin having a lower refractive index than the above-mentioned photocurable resin.
Or the case-shaped substrate 40 is filled. This may be a thermosetting resin or, similarly, a light curable resin.
As another method, the exposed portion other than the photopolymerized waveguide portion can be polymerized by heating to form a clad portion. In this case, the photopolymerization solution used must be imparted with heat curability. Generally, the refractive index at the site where photopolymerization and thermal polymerization have been performed is highest.

As described above, the optical demultiplexer according to the present invention simply collects the first, second, and third optical waveguides simply by introducing predetermined short-wavelength light from the light introducing port 41. , Semi-transparent mirror 2
1, 22, 23 and the emission port 50 can also be integrally molded. Therefore, the light inlet 41, each semi-transparent mirror 21, 22,
There is no displacement between 23 and the exit 50. Therefore,
An excellent method of manufacturing an optical demultiplexer having no optical loss due to misalignment, as well as an efficient manufacturing method with low assembly cost.

(Fourth Embodiment) In a third embodiment, a case-like substrate 40 is immersed in a solution of a photo-curable resin, and a short-wavelength laser is incident from the outside through a light inlet 41 to form a simple substrate. Production method was shown, but instead of this,
It is also possible to use the photo-curable resin 37 in a gel form. The gel photocurable resin 37 is obtained by, for example, dissolving acryl with a ketone-based solvent, and then semi-drying a dispersion of a styrene monomer. Then, as shown in FIG.
By stacking on top of 2,23 and stacking them,
It can replace the solution. The optical waveguide is formed by injecting the short-wavelength laser light 36, causing a photopolymerization reaction on the optical path, and curing the light. Thereafter, the remaining styrene monomer is removed from the surroundings by vacuum drying or the like, so that the optical waveguide has a relatively high refractive index. Therefore, a step index type optical waveguide equivalent to the first embodiment is obtained. Thereafter, the case-like substrate 40 is ultra-precisionly cut so that the entrance surface and the exit surface are flat.
Installed in Therefore, it becomes a simpler manufacturing method. The effect on loss or the effect on assembly cost is as follows:
This is almost the same as the third embodiment.

(Modifications) In addition, various modifications can be considered in this embodiment. For example, in the third embodiment, the short-wavelength laser light 36 is introduced through the optical fiber 60 provided outside, but the optical fiber 60 is directly fitted into the light introduction port 41 and the end face of the optical fiber 60 It may be manufactured integrally with the first optical waveguide of the wave device. It becomes a more efficient manufacturing method. In the first and second embodiments, the semi-transmissive mirrors or the dichroic mirrors are arranged at regular intervals and the emission ports are arranged in a row. However, as shown in FIG. 6, the transmitted light path may be arranged in a rectangular shape. good. This results in a more compact optical demultiplexer.

In the first embodiment, a color filter is provided at each of the exit ports 50 to separate a specific wavelength. However, an interference film filter may be used instead of the color filter.
This is because the transmission wavelength error of the interference filter is the incident angle θ
Because it is proportional to When this is used for the exit port, the angle of incidence is 0 degrees, so that error reflection due to Δθ is extremely small. Therefore, it becomes a very effective specific wavelength separating means.
Although the above-described optical waveguide was created using a short-wavelength laser, the light from the ultrahigh-pressure mercury lamp (having a peak wavelength of 380 nm) was used.
m) may be collimated, and then passed through a pinhole having a diameter of 1 mm to be replaced with the short wavelength laser.

Although various other modifications are conceivable, an optical demultiplexer that reduces the loss due to diffusion or optical axis shift by connecting the light entrance, the specific wavelength separation means, and the exit with an optical waveguide. If there is any kind. Also,
In the optical shaping method for producing the optical demultiplexer, in accordance with an actual use situation, a short wavelength light is introduced along an incident optical axis, and the light is cured sequentially according to the path, thereby producing an optical waveguide. If there is any kind.

[0028]

[Brief description of the drawings]

FIG. 1 is a configuration sectional view of an optical demultiplexer shown in a first embodiment.

FIG. 2 is a front view of the optical demultiplexer shown in the first embodiment.

FIG. 3 is a configuration sectional view of an optical demultiplexer shown in a second embodiment.

FIG. 4 is a transmittance distribution diagram of a dichroic mirror.

FIG. 5 is an explanatory view of a production method using the photocurable resin solution of the present invention.

FIG. 6 is an explanatory view of a production method using the gel-like photocurable resin of the present invention.

FIG. 7 is a modified example of an optical duplexer in which semi-transparent mirrors are arranged in four directions.

FIG. 8 is a configuration sectional view of an optical demultiplexer using a conventional glass block.

FIG. 9 is a diagram showing the relationship between wavelength-multiplexed light and interference filters.

[Explanation of symbols]

 10, 11, 12 Optical waveguide 21, 22, 23 Semi-transparent mirror 31, 32, 33 Dichroic mirror 35 Photocurable resin solution 36 Short wavelength laser light 37 Gel photocurable resin 40 Case substrate 41 Light inlet 42 Low Refractive index light transmitting resin 50 Outgoing port 51, 52, 53 Color filter 60 Optical fiber 70, 72, 73 Specific wavelength separation device

Claims (2)

[Claims] An optical demultiplexer that separates wavelength-multiplexed light into respective wavelength components by a plurality of filters and outputs the separated light to the outside, a case-like substrate having a light inlet and a plurality of outlets. A plurality of specific wavelength separating means provided at a predetermined angle with respect to each incident light in the case-shaped substrate and connected to the plurality of emission ports, A first optical waveguide which is formed in close contact with the specific wavelength separating means, and which is formed in close contact between the plurality of specific wavelength separating means and guides light transmitted by the specific wavelength separating means to the adjacent specific wavelength separating means. A second optical waveguide to be incident; and a low-refractive-index light-transmitting resin that fills the case-shaped substrate and embeds the first and second optical waveguides and the specific wavelength separating unit. Is the specific wavelength Optical demultiplexer, wherein the output from said exit coupled with the release means. 2. The specific wavelength separation means has a liquid or gel-like monomer around the specific wavelength separation means, and introduces light of a predetermined wavelength from the light introduction port to photopolymerize the monomer along the optical axis. The light component according to claim 1, wherein a reaction is caused to cure to form an optical waveguide for guiding the reflected light of the first and second optical waveguides and the specific wavelength separating means to the outside. Method of manufacturing a corrugator.