JP3830181B2 - Manufacturing method of optical interconnection cable - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an information communication device that handles optical signals and electric signals at the same time. More specifically, the present invention is used to transmit signals between computers, between boards in computers, or between other devices and / or elements. The present invention relates to an optical interconnection cable.
[0002]
[Prior art]
An interconnection cable is used to transmit signals between computers or between boards in a computer. Conventionally, what is generally used for this purpose is an electric conducting wire such as a twisted pair wire or a coaxial cable. However, the use of such conductors composed of electrical conductors has become limited as the signal transmission rate increases. This is because the electric conductors used have performance limitations such as a narrow band, a short transmission distance, a large amount of crosstalk, a large cable volume, and the like. Therefore, in recent years, it has been proposed to use an optical interconnection system using light instead of an electrical conductor, particularly in a region where a high transmission rate is required.
[0003]
Optical interconnection systems currently in practical use generally transmit light from a light source such as an LD (laser diode) or LED (light emitting diode) via a multimode optical fiber, and further transmit the transmitted light. It is configured to be received by a light receiving element such as a PD (photodiode) and output as an electrical signal. By comprising in this way, the above faults of the electric conducting wire conventionally used for the same purpose can be solved.
[0004]
[Problems to be solved by the invention]
In the optical interconnection system as described above, if high-density wiring is desired, it can be dealt with by preparing a combination of light source elements, optical fibers, and light receiving elements for the necessary channels. However, in order to apply this system to a field where higher performance is required, such as connection between boards in a supercomputer, it is desirable to solve the following problems.
[0005]
(1) To achieve high speed, transmission in single mode rather than multimode is possible.
(2) In the case of transmission in single mode, the core diameter of the optical fiber or optical waveguide used is reduced to a fraction of that of multimode, so that the alignment between the element and the fiber or waveguide is easy. Be possible.
(3) The wiring density can be improved.
[0006]
[Means for Solving the Problems]
According to the present invention, the above-described problem is a light source element, an optical waveguide for transmitting light from the light source element, and a light receiving element for receiving light transmitted through the optical waveguide and outputting it as an electrical signal. An optical interconnection cable having a combination of a light source element, an optical waveguide, and a light receiving element. This can be solved by an optical interconnection cable characterized in that an optical coupler made of a refractive index distribution-forming material capable of generating a refractive index distribution corresponding to the strength is provided.
[0007]
Further, according to the present invention, a light source element, an optical waveguide for transmitting light from the light source element, and a light receiving element for receiving light transmitted through the optical waveguide and outputting it as an electrical signal are combined. In manufacturing an optical interconnection cable having
The one end face of the optical waveguide and the end face of the light source element and the other end face of the optical waveguide and the end face of the light receiving element are arranged to face each other with a predetermined gap therebetween,
Supplying each of the gaps formed between the end faces with a refractive index distribution-forming material capable of generating a refractive index distribution corresponding to the intensity of the light upon irradiation with light of a specific wavelength band; and
Each of the refractive index distribution forming materials is irradiated with light of the specific wavelength band from at least one end face of the optical waveguide and / or element adjacent to the material, and corresponds to the intensity of the light. Forming an optical coupler having a refractive index profile;
A method for manufacturing an optical interconnection cable is also provided.
[0008]
Furthermore, according to the present invention, at least one common light source, a multi-branch waveguide for branching light from the light source into two or more lights, and light from the multi-branch waveguide as electrical signals A light source element including a light modulator for modulating the light, a simple waveguide for transmitting each light from the light source element, and receiving the light transmitted through the simple waveguide and outputting it as an electrical signal In manufacturing a multi-branch optical interconnection cable having a combination with a light receiving element for
Forming a waveguide forming layer and a modulator forming layer on the same or different substrates;
The waveguide forming layer and the modulator forming layer are processed to form the multi-branch waveguide, the optical modulator, and the simple waveguide linearly in a predetermined pattern, provided that the multi-branch waveguide The number of light branches in the light receiving element is adjusted to be at least one greater than the number of the light receiving elements arranged,
Attach the light receiving element to the light emitting end from the simple waveguide with a predetermined gap between them,
Refraction capable of generating a refractive index distribution corresponding to the intensity of light in each gap formed between the end face of the simple waveguide and the end face of the light source element when irradiated with light of a specific wavelength band. Supply rate distribution forming material,
An optical coupler having a refractive index distribution corresponding to the intensity of the light by irradiating each of the refractive index distribution forming materials with light of the specific wavelength band from an incident end of the multi-branch waveguide. Formed in a lump,
Attach the common light source to the light incident end of the multi-branch waveguide with a predetermined gap between them,
A refractive index capable of generating a refractive index distribution corresponding to the intensity of light in a gap formed between the end face of the multi-branch waveguide and the end face of the common light source when irradiated with light of a specific wavelength band. Supplying a distribution-forming material, and
Corresponding to the intensity of light by irradiating light of the specific wavelength band from the output end of the multi-branch waveguide that is not coupled to the light receiving element to the refractive index profile forming material. Forming an optical coupler having a refractive index profile,
A method for manufacturing a multi-branch optical interconnection cable is also provided.
[0009]
According to the present invention, the positioning of the light source controlled by the electrical signal, the optical waveguide, and the light receiving element is facilitated by the coupling portion of the light source and the optical waveguide, and the coupling portion of the optical waveguide and the light receiving device, respectively. This can be solved by applying an optical coupler that generates a refractive index distribution by irradiating light of a specific wavelength band to increase the coupling efficiency.
In addition, the application of the optical coupler may generate a refractive index distribution corresponding to the intensity of light after receiving light of a specific wavelength band after fixing an element such as a light source or a light receiving element on the end face of the optical waveguide. Provide a possible refractive index profile-forming material, and irradiate the refractive index profile-forming material with light of a specific wavelength band from at least one of the optical waveguide and the element. This can be achieved by forming an optical coupler having The refractive index distribution-forming material that can be advantageously used in the present invention and the formation of an optical coupler using the same are described in Japanese Patent Application Laid-Open No. 7-77737, which refers to the preferred examples below. It is disclosed as “material” or “refractive index distribution forming material”.
[0010]
Furthermore, to improve the wiring density, it is effective to make each component constituting the optical interconnection cable planar (waveguide). This planarization uses, in particular, a flexible base film as a substrate, a polymer waveguide and a polymer modulator are linearly formed on the substrate, and an optical coupler as described above is provided at each of both ends thereof. Thus, it can be advantageously realized by mounting the light receiving element and the light source element. Furthermore, if the light source element used here is composed of at least one common light source and a light branching section that splits the light from this light source into two or more lights, the number of parts is reduced, so that higher density is achieved. Can be realized.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with respect to preferred embodiments thereof. However, it should be understood that the optical interconnection cable according to the present invention can be implemented in configurations other than those described.
An optical interconnection cable according to the present invention includes a light source element, an optical waveguide for transmitting light from the light source element, and a light receiving element for receiving light transmitted through the optical waveguide and outputting it as an electrical signal. Have in combination. Here, the light source element is preferably capable of controlling or modulating light emitted therefrom with an electric signal. This light modulation can be performed according to a conventional method. For example, the light source element itself may have a modulation function, or preferably, the light source element may be modulated in the course of branching the light from the light source element. Good. The latter case is preferred in the practice of the present invention, and therefore, in the following description, in particular, at least one common light source and a multi-branch guide for branching light from the light source into two or more lights. The present invention will be described with reference to a light source element configured as a multi-branch structure including a waveguide and an optical modulator for modulating each light from the multi-branch waveguide with an electric signal.
[0012]
The light source used for the light source element is preferably used as a common light source, and the type thereof is not particularly limited in the practice of the present invention, and is generally used in this technical field. Include. Examples of suitable light sources include LDs and LEDs. From the viewpoint of single mode transmission, it is recommended to use an LD as a light source.
[0013]
The light from the common light source is then split into two or more lights. For this optical branching, a multi-branch waveguide conventionally used in this technical field can be advantageously used. An example of a suitable multi-branch waveguide is a star coupler. Here, the number of light branches in the multi-branch waveguide is also important in the present invention. That is, when forming an optical coupler from the above refractive index profile-forming material, the processing is facilitated, and for other purposes, the number of light branches in the multi-branch waveguide is determined by the number of light receiving elements (the number of light receiving elements). It is preferable to make it at least 1 or more than. By adjusting the number of branches of the multi-branch waveguide in this way, a waveguide that is not optically coupled to the light receiving element can be formed. Therefore, the end face of the waveguide is connected to light in a specific wavelength band for forming an optical coupler. It can be used as the incident part.
[0014]
The multi-branch waveguide and the simple waveguide described below are respectively similar to the multi-branch waveguide and the simple waveguide commonly used in this technical field, and therefore suitable according to the same technique. It can be mounted on a substrate. Suitable materials for the substrate include a wide range of materials from hard to flexible, with typical examples being glass plates, plastic plates such as acrylic plates, ceramic plates such as alumina plates, metal plates such as molybdenum. A plate or a plastic film, for example, a flexible film such as polyamide, polyethylene, polyethylene terephthalate, polyvinyl chloride, polycarbonate, or polypropylene. Of course, other substrate materials can be used as required. Examples of suitable materials for forming the waveguide include resin materials such as acrylic resin and polyimide resin, glass materials such as quartz glass, and LiNbO._ThreeAnd other ferroelectric materials.
[0015]
In order to modulate each light from the above-mentioned multi-branch waveguide with an electric signal, an optical modulator is arranged. As the light modulator, a light modulator conventionally used in this technical field can be advantageously used. As a suitable optical modulator, for example, a modulation element using an electro-optic effect, that is, an EO element, for example, an E / O switch can be cited. An example of a material suitable for forming an EO element is a resin waveguide material containing at least one of an azo dye, a merocyanine dye, and a stilbene dye, LiNbO,_ThreeAnd other ferroelectric materials.
[0016]
In order to transmit light from the light source element described above, an optical waveguide is used in the present invention. This optical waveguide can also be constructed from those commonly used in this technical field, like the multi-branch waveguide of the light source element described above. This optical waveguide is preferably a simple waveguide.
A light receiving element is disposed in order to receive light transmitted through the optical waveguide and output it as an electrical signal. The light receiving element can be a conventional means such as a PD array.
[0017]
An optical interconnection cable according to the present invention has a combination of a light source element, an optical waveguide, and a light receiving element as described above, and an optical coupler that optically couples the components. As described above, the optical coupler used for optical coupling in the present invention is capable of generating a refractive index distribution corresponding to the intensity of light upon irradiation with light of a specific wavelength band. It is formed from a formable material. Suitable materials for forming a refractive index profile suitable for forming an optical coupler include, for example, those described in JP-A-7-77737 cited above, for example, an alicyclic compound or a chain compound having an epoxy group, Composition comprising an ethylenically unsaturated compound containing an aromatic ring or halogen, a polyfunctional acrylate or methacrylate, a photopolymerization initiator, an organically modified silicone, and an ethylenically unsaturated containing an aromatic ring or halogen A composition containing a compound, a polyfunctional acrylate or methacrylate, and a photopolymerization initiator, a thermosetting copolymer containing in its structural unit an acrylate or methacrylate having a hydroxyl group at its terminal, and an aromatic ring or halogen. Includes a composition containing an ethylenically unsaturated compound, a polyfunctional acrylate or methacrylate, and a photopolymerization initiator, etc. That.
[0018]
In these compositions, the alicyclic compound or chain compound having an epoxy group used as one component thereof is, for example, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate. Further, ethylenically unsaturated compounds containing an aromatic ring or halogen are allyl carbazole, methacryloyloxyethyl carbazole, acryloylethyloxycarbazole, vinyl carbazole, vinyl naphthalene, naphthyl acrylate, tribromophenyl acrylate, dibromophenyl acrylate, phenoxyethyl. Acrylate and the like. Examples of the organically modified silicone include acrylic modified silicone, methacrylic modified silicone, and epoxy modified silicone. Furthermore, the thermosetting copolymer containing an acrylate or methacrylate having a terminal hydroxyl group in the structural unit is, for example, chlorotrifluoroethylene, vinyltrimethyl acetate, and an acrylate or methacrylate having a terminal hydroxyl group in the structural unit. A copolymer comprising a substance contained in Furthermore, the polyfunctional acrylate or methacrylate is, for example, trimethylolpropane, triacrylate, neopentyl glycol diacrylate, or the like. And the photoinitiator used for the photopolymerization of the above components is, for example, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, benzyl, benzoin isopropyl ether or the like.
[0019]
The refractive index profile-forming material is usually used in a liquid state, and can be supplied by various means. However, in forming the optical coupler, since such a material must be supplied in a small amount and accurately, a dropping means such as a dropping pipette can be advantageously used. The gap between the parts to which the refractive index distribution-forming material is to be supplied can be various sizes depending on the characteristics of the material used and other factors, but is generally about 0. Advantageously, it is 1 mm or more. If the gap is too narrow, the material cannot be supplied reliably and accurately. On the other hand, if the gap is too large, a satisfactory optical coupler cannot be provided. After supplying the refractive index distribution-forming material, converting it into an optical coupler can be advantageously performed by irradiating light of a specific wavelength band from a component adjacent thereto. However, depending on the material used, treatment such as heating may be performed instead of light irradiation.
[0020]
The optical interconnection cable according to the present invention can be manufactured by arbitrarily using a technique generally used in this technical field. However, it can be preferably manufactured by the following procedure.
After fixing the element that is to be optically coupled to the end face of the optical waveguide, a refractive index distribution forming material that generates a refractive index distribution by the intensity of light in a specific wavelength band is supplied to the gap between the optical waveguide and the element. Then, the refractive index distribution-forming material is irradiated with light of a specific wavelength band from at least one of the optical waveguide / element to be cured, and at the same time, a refractive index distribution is generated to produce an optical coupler.
[0021]
Moreover, when manufacturing a multi-branch optical interconnection cable, preferably, the following steps can be followed.
(1) forming a waveguide forming layer and a modulator forming layer on the substrate;
(2) A step of linearly forming a multi-branch waveguide, a modulator and a simple waveguide, provided that the number of branches of the waveguide is one or more than the number of light receiving elements (photo detectors, etc.)
(3) A step of attaching a light receiving element to an emission end of light from a simple waveguide formed on the substrate,
(4) A step of dropping the refractive index distribution forming material into the gap between the simple waveguide and the light receiving element, and entering light of a specific wavelength band from the incident end of the multi-branch waveguide to manufacture an optical coupler in a lump;
(5) A step of attaching a common light source to the incident end of the multi-branch waveguide formed on the substrate,
(6) A refractive index distribution forming material is dropped into the gap between the multi-branch waveguide and the common light source, and a specific wavelength band is formed from the outgoing end (incident end) that is not coupled to the light receiving element among the outgoing ends of the multi-branched waveguide. A step of producing an optical coupler by injecting the light of
(7) A step of forming an electric I / O terminal.
[0022]
As can be easily understood, these optical interconnection cables can be manufactured in an order other than that described above, if necessary.
[0023]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a principle configuration diagram showing a preferred embodiment of an optical interconnection cable according to the present invention. The illustrated interconnection cable has a substrate 10 made of a flexible plastic film (here, a PET film). A multi-branch waveguide 3 (here a star coupler), an optical modulator 4 (here an E / O switch as a polymer modulator) and a simple waveguide 6 (here a polymer waveguide) 6 are linear as shown. The common light source 1 (here, LD) and the light receiving element 8 (here, PD array) are mounted on both ends thereof via optical couplers 2 and 7, respectively. A modulation signal can be input to the optical modulator 4 from a signal input terminal 15 (here, flip chip). Each buffer layer 11 is made of polyimide. The light receiving element 8 has a signal output lead 9 connected thereto. In the present invention, the light source 1, the multi-branch waveguide 3, and the optical modulator 4 may be collectively referred to as a light source element.
[0024]
In this configuration, all the optical connection portions are on the connector, and input / output with the outside is only an electric signal. Therefore, when the connector is mounted on a substrate or the like, the optical axis alignment, which has been conventionally complicated, becomes unnecessary. In addition, since an optical coupler using a refractive index distribution-forming material is applied to the optical connection portion inside the connector, positioning can be performed easily and accurately.
[0025]
Further, since the planar type optical waveguide is used and the light source is shared in this way, extremely high density wiring is possible as compared with the conventional multi-fiber connection system. For example, multi-channeling with a pitch of about 50 μm can be realized relatively easily.
[0026]
Example 1
In this example, the manufacture of the optical interconnection cable (2-channel waveguide) shown in FIG. 2 will be described with reference to FIGS. FIG. 3 shows the optical modulator plate manufacturing process, FIG. 4 shows the waveguide plate manufacturing process, and FIG. 5 shows the optical coupling process.
[0027]
Optical modulator plate manufacturing
First, an optical modulator plate of Mach-Zehnder type with a modulation portion length of 60 mm and a thickness of 3 μm was manufactured. In this optical modulator plate, a splitter portion for bifurcating light from the light source is provided immediately before the modulating portion, and the interval between the waveguides is 0.05 mm. A soda glass plate having a length of 100 mm, a width of 30 mm, and a thickness of 1 mm was prepared as a substrate 20 as shown in Step A1 of FIG. Next, as shown in step A2, a lower electrode 21 having a thickness of 0.2 μm was formed by sputtering of chromium. Thereafter, as shown in Step A3, a polyimide resin was spin coated to form a lower cladding layer 22 having a thickness of 3 μm. Subsequently, as shown in Step A4, the conductive core 23 was formed with a film thickness of 3 μm. In order to form a conductive core, a polyimide resin having an azo dye in a side chain molecule was spin-coated and further etched (RIE). Next, an upper cladding layer 24 having a thickness of 3 μm was formed by the same method as in step A3 (see step A5). After the formation of the upper cladding layer, as shown in Step A6, an upper electrode 25 having a thickness of 0.2 μm was formed by sputtering of chromium and subsequent selective etching. Finally, the end faces of the respective waveguides were formed with an excimer laser to obtain the target optical modulator plate.
[0028]
Manufacture of waveguide plates
In the same manner as the manufacture of the optical modulator plate, a waveguide plate was manufactured by the method shown in order in FIG. In this figure, the steps B2 and B6 are missing in order to clarify the correspondence with FIG.
[0029]
First, as shown in step B1 of FIG. 4, a soda glass plate having a length of 100 mm × width of 30 mm × thickness of 1 mm was prepared as the substrate 30. Next, as shown in Step B3, a polyimide resin was spin-coated to form a lower cladding layer 32 having a thickness of 3 μm. Subsequently, as shown in Step B4, two parallel channel waveguides 33 having a width of 10 μm, a thickness of 8 μm and a line spacing of 1 mm were formed. In order to form a channel waveguide, a fluorinated polyimide resin was spin-coated and further etched (RIE). Next, an upper cladding layer 34 having a thickness of 3 μm was formed by the same method as in step B3 (see step B5). After the formation of the upper clad layer, the end faces of the respective waveguides were formed with an excimer laser to obtain a target waveguide plate.
[0030]
Optical coupling process
Next, using the obtained optical modulator plate and waveguide plate, an optical interconnection cable was manufactured as shown in FIG.
Step C1:
A glass plate having a length of 250 mm, a width of 30 mm, and a thickness of 3 mm is prepared as a substrate (not shown, corresponding to the substrate 10 in FIG. 1), and the optical modulator plate and the waveguide plate previously manufactured thereon are respectively provided. The corresponding waveguides were attached so that they were connected to each other. The gap between the end faces of the waveguide was 100 μm. In this gap, a refractive index profile-forming material having the following composition:
Alicyclic epoxy resin (EHPE-3150, 50% by weight
(Daicel UCB)
Allylcarbazole (manufactured by Nippon Distillation Co., Ltd.)
Biimidazole (B1225, manufactured by Tokyo Chemical Industry Co., Ltd.) 5% by weight
Filled. Then, an argon laser beam was incident from the incident end of the optical modulator 4 as shown by an arrow in the figure to form a waveguide in the resin portion, and the resin was cured by irradiation with ultraviolet rays. An optical coupler 5 was formed.
[0031]
Step C2:
An MSM type photodetector 8 having a sensitivity of 0.1 mW was attached to one of the output ends of the waveguide 6. The gap between the end face of the waveguide and the photodetector was 100 μm. This gap is filled with a refractive index distribution-forming material having the same composition as described above, and an argon laser beam is incident from the incident end of the optical modulator 4 as indicated by an arrow in the figure, and a waveguide is formed in the resin portion. Then, the resin was cured by ultraviolet irradiation. An optical coupler 7 was formed.
[0032]
Step C3:
A bare-chip laser diode 1 having an output of 40 mW and an oscillation wavelength of 1.3 μm was attached to the input end of the optical modulator 4. It fixed to the board | substrate using the adhesive agent, and the electrode was formed by wire bonding. The gap between the end face of the waveguide and the laser diode was 100 μm. The gap is filled with a refractive index distribution-forming material having the same composition as described above, and an argon laser beam is incident from the empty exit end of the waveguide 6 as shown by the arrow in the figure and guided to the resin portion. A waveguide was formed, and the resin was further cured by irradiation with ultraviolet rays. An optical coupler 2 was formed.
[0033]
Evaluation test
In order to evaluate the characteristics of the manufactured optical interconnection cable, the laser diode was oscillated, the optical modulator was driven, and the incident intensity to the photodiode was measured. The drive voltage of the modulator was DC 100 volts. As a result, the incident light intensity of the photodiode was 0.2 mW, and the loss of the transmission line was evaluated as 20 dB. It was also confirmed that the modulator operates at 100 Mbps.
[0034]
Example 2
The procedure described in Example 1 was repeated. However, in this example, instead of the glass plate, Mylar (registered trademark, manufactured by EI DuPont) having a length of 250 mm, a width of 30 mm, and a thickness of 3 mm was used as the substrate 10. The obtained optical interconnection cable was confirmed to operate at 1000 Mbps, although the transmission line loss increased to 23 dB.
[0035]
In the above embodiments, the optical interconnection cable having a two-channel waveguide has been described. However, in the present invention, satisfactory results can be obtained even when the number of channels is further increased.
[0036]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the optical interconnection cable which has a high-density wiring can be provided cheaply by easy alignment. Therefore, the present invention can greatly contribute to miniaturization and high performance of information communication equipment.
[Brief description of the drawings]
FIG. 1 is a principle configuration diagram showing a preferred embodiment of an optical interconnection cable according to the present invention.
FIG. 2 is a plan view showing a configuration of an embodiment of an optical interconnection cable according to the present invention.
3 is a cross-sectional view sequentially showing the manufacture of the optical modulator plate of the optical interconnection cable shown in FIG. 2. FIG.
4 is a cross-sectional view sequentially showing the manufacture of the waveguide plate of the optical interconnection cable shown in FIG. 2. FIG.
5 is a plan view illustrating the optical coupling process for completing the optical interconnection cable of FIG. 2 by attaching the optical modulator plate of FIG. 3 and the waveguide plate of FIG. 4 to a common substrate in order.
[Explanation of symbols]
1 ... Light source
2 ... Optical coupler
3. Multi-branch waveguide
4. Light modulator
5 ... Optical coupler
6 ... Optical waveguide
7 ... Optical coupler
8. Light receiving element
9 ... Signal output lead
10 ... Board
11 ... Buffer layer

Claims (1)

At least one common light source, a multi-branch waveguide for branching light from the light source into two or more lights, and an optical modulator for modulating light from the multi-branch waveguide with an electrical signal A simple light guide element for transmitting each light from the light source element, and a light receiving element for receiving the light transmitted through the simple waveguide and outputting it as an electrical signal. In manufacturing the multi-branch optical interconnection cable built on the board,
Forming a waveguide forming layer and a modulator forming layer on the same or different substrates;
The waveguide forming layer and the modulator forming layer are processed to form the multi-branch waveguide, the optical modulator, and the simple waveguide linearly in a predetermined pattern, provided that the multi-branch waveguide The number of light branches in the light receiving element is adjusted to be at least one greater than the number of the light receiving elements arranged,
Attach the light receiving element to the light emitting end from the simple waveguide with a predetermined gap between them,
Refractive index distribution formability in which a gap formed between the end face of the simple waveguide and the end face of the light source element is irradiated with light of a specific wavelength band to generate a refractive index distribution corresponding to the intensity of the light. Supply materials,
An optical coupler having a refractive index distribution corresponding to the intensity of the light by irradiating each of the refractive index distribution forming materials with light of the specific wavelength band from an incident end of the multi-branch waveguide. Formed in a lump,
Attach the common light source to the light incident end of the multi-branch waveguide with a predetermined gap between them,
A refractive index distribution-forming material that generates a refractive index distribution corresponding to the intensity of light when irradiated with light of a specific wavelength band in a gap formed between the end face of the multi-branch waveguide and the end face of the common light source And irradiating the refractive index distribution-forming material with light of the specific wavelength band from the output end of the multi-branch waveguide that is not coupled to the light receiving element. Forming an optical coupler having a refractive index profile corresponding to the intensity of light;
Are implemented in the above order. A method for manufacturing a multi-branch optical interconnection cable.

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