JP2002031746A - Optical branching/coupling device and optical transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a crosstalk, in which an optical signal from a light source creeps into a photodetector, and to guide an optical signal from an optical fiber effectively to the photodetector. SOLUTION: A bi-directional optical waveguide 18 is coupled with a connector 16, this waveguide 18 is constituted of optical waveguides 42, 44; the waveguide 42 is coupled with a photodetector 20 while the waveguide 44 is coupled with a semiconductor laser 30 through an optical waveguide 26; and a male connector 38 is freely detachably connected to the connector 16, while an optical fiber 40 for bi-directional transmission is connected to the connector 38. By using one having a numerical aperture of 0.3 for the optical fiber 40, using one having 0.5 for the waveguides 42, 44, and using one having 0.1 for the waveguide 26, the optical signal from the optical fiber 40 is effectively guided to the photodetector 20 through the waveguide 42; simultaneously, the optical signal from the semiconductor laser 30 is made to enter by the waveguide 26 of the smaller numerical aperture; the optical signal passing through the waveguide 26 is thereby reduced in the widening angle, reducing the crosstalk of the optical signal entering the photodetector 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical splitter / coupler and an optical transmission apparatus, and more particularly to an optical splitter / coupler suitable for transmitting and receiving optical signals using a single-core optical fiber. Related to the device.

[0002]

2. Description of the Related Art Conventionally, a bidirectional optical communication device for transmitting and receiving an optical signal using an optical fiber is disclosed in, for example,
As described in Japanese Patent Application Laid-Open No. 1-271548, a main waveguide that is optically coupled to an optical fiber and guides light incident from the optical fiber to a light receiving element, and a main waveguide at a side of the main waveguide with respect to the optical axis direction. 2. Description of the Related Art There is known a device having a sub-waveguide optically coupled to guide light emitted from a light-emitting element to an optical fiber via a main waveguide.

[0003]

In a conventional bidirectional optical communication device or optical coupler, an optical fiber and a photodetector are required to sufficiently confine received light from the optical fiber in an optical waveguide and guide the light to the photodetector with high efficiency. A configuration is adopted in which the numerical aperture of the optical waveguide that optically couples with the optical fiber is equal to or larger than that of the optical fiber. Therefore, a main waveguide for guiding light incident from the optical fiber to the light receiving element,
In an optical coupler of a type that simultaneously forms a sub waveguide that guides light emitted from a light emitting element to an optical fiber, the main waveguide and the sub waveguide have the same numerical aperture, and the sub waveguide also has a large numerical aperture. It has become. In particular, when a plastic optical fiber (hereinafter abbreviated as POF) is used as an optical signal transmission medium, the numerical aperture of the POF is 0.3 to 0.5.
Since it is as large as 5, the numerical aperture of the optical coupler also needs to be increased. When the numerical aperture of the optical waveguide forming the optical coupler is the same as the numerical aperture of the POF, the optical waveguide of the optical coupler becomes 17 °.
Light rays incident at an angle of about 30 ° can be confined and propagated.

However, when a light beam from a light source is incident on a sub-waveguide having the same numerical aperture as the main waveguide, the light beam enters the sub-waveguide at a wide angle. As a result, scattering / leakage light easily occurs in the sub-waveguide, resulting in stray light. Furthermore, the light beam emitted from the optical coupler with a large divergence angle is not coupled to the optical fiber, and the reflection at the end face of the optical coupler and the optical fiber increases.
Part of these reflected light / stray light reaches the photodetector through the main waveguide, and causes crosstalk. For this reason,
A conventional bidirectional optical communication device or optical coupler using an optical coupler has a problem that crosstalk is large.

As described above, since crosstalk occurs in a conventional bidirectional optical communication device or optical coupler, it is difficult to perform full-duplex optical communication in which transmission and reception are simultaneously performed between optical communication devices having a bidirectional optical communication device. And each optical communication device performs half-duplex communication in which transmission and reception are performed alternately.

When the numerical aperture of the entire optical waveguide is reduced in order to reduce the crosstalk of the bidirectional optical communication device, the light transmission efficiency is reduced when a photodetector is coupled to the optical waveguide, and the optical signal is reduced. There is a problem that the transmission distance is shortened.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical splitter / coupler capable of reducing crosstalk in which an optical signal from a light source goes around a photodetector and efficiently guiding an optical signal from an optical fiber to the photodetector. A transmission device and an optical communication device are provided.

Another object of the present invention is to provide an optical branching coupler capable of reducing crosstalk in which an optical signal from a light source goes around a photodetector and efficiently guiding an optical signal from an optical fiber to the photodetector. It is to provide a manufacturing method of.

[0009]

In order to achieve the above object, the present invention provides an optical signal transmission medium for connecting an optical fiber and a photodetector, which guides an optical signal from the optical fiber to a photodetector. An optical branching / coupling device having an optical waveguide unit and a second optical waveguide unit that branches from the first optical waveguide unit and guides an optical signal from a light source to the optical fiber. It is composed.

(1) The first optical waveguide means has a numerical aperture larger than that of the optical fiber, and at least a part of the second optical waveguide means has an aperture larger than that of the first optical waveguide means. It is composed of a small number of optical waveguide members.

(2) The first optical waveguide means has a numerical aperture larger than that of the optical fiber, and the second optical waveguide means has an optical waveguide having a larger numerical aperture than the optical fiber; An optical waveguide member coupled to the optical waveguide and the light source and having a smaller numerical aperture than the first optical waveguide means.

In this case, the numerical aperture of the optical fiber is set to NA
1, the numerical aperture of the first optical waveguide means is NA2,
When the numerical aperture of the optical waveguide member is NA3, each numerical aperture is set to a value that satisfies the relationship NA3 <NA1 <NA2.

(3) The first optical waveguide means is coupled to the first optical waveguide having a larger numerical aperture than the optical fiber, the first optical waveguide and the photodetector, and A second optical waveguide having a larger numerical aperture than the optical fiber, and a second optical waveguide having a larger numerical aperture than the optical fiber; and a second optical waveguide having a larger numerical aperture than the optical fiber. It is composed of a second optical waveguide member coupled to the wave path and the light source and having a smaller numerical aperture than the first optical waveguide means.

In this case, the numerical aperture of the optical fiber is NA
1, the numerical aperture of the first optical waveguide is NA2, the numerical aperture of the first optical waveguide member is NA4, and the numerical aperture of the second photoconductive member is NA5. The number is set to a value that satisfies the relationship of NA5 <NA1 <NA2 ≦ NA4.

(4) The first optical waveguide means comprises a first optical waveguide having a first core and a clad covering the first core, and the second optical waveguide means comprises A second optical waveguide having a second core and a cladding covering the second core, wherein the first core has a refractive index of n
1, when the refractive index of the second core is n2 and the refractive index of the cladding is n3, the respective refractive indices are n
It is set to a value that satisfies the relationship of 3 <n2 <n1.

In this case, in the first optical waveguide,
The second core is inserted between the first core and the clad.

(4) The first optical waveguide means comprises a first optical waveguide having a first core, a second core covering the first core, and a cladding covering each of the cores. The second optical waveguide means includes a second optical waveguide having the first core and a clad that covers the first core, wherein a refractive index of the first core is n1, and The refractive index of the second core is n2, and the refractive index of the cladding is n2.
When the number is 3, each refractive index is set to a value satisfying the relationship of n3 <n1 <n2.

(5) The cross-sectional area of the first optical waveguide is larger than the cross-sectional area of the second optical waveguide.

The present invention also provides an optical branching coupler coupled to an optical fiber, a photodetector coupled to the optical branching coupler to detect an optical signal from the optical branching coupler, A light source that is coupled to a coupler and outputs an optical signal to the optical branching coupler; and as the optical branching coupler, an optical transmission device including any one of the optical branching couplers is configured. is there.

The present invention also provides an optical splitter / coupler coupled to an optical fiber serving as a communication path, and a photodetector coupled to the optical splitter / coupler and detecting an optical signal from the optical splitter / coupler. A light source coupled to the optical splitter / coupler to output an optical signal to the optical splitter / coupler; a plurality of demodulation circuits for demodulating an optical signal detected by the photodetector; A plurality of modulation circuits that output signals to the light source; and a control that controls operations of the demodulation circuits and the modulation circuits based on signals from the plurality of demodulation circuits and outputs data to the plurality of modulation circuits. Circuit, the control circuit is an optical communication device that switches between control by full-duplex optical communication and control by half-duplex optical communication in accordance with the state of the optical signal detected by the photodetector, the As the optical branching coupler, It is obtained by constituting the optical communication device comprising a deviation of the optical branching coupler.

In configuring the optical communication device, the following elements can be added.

(1) The control circuit executes control by full-duplex optical communication when the light amount of the optical signal detected by the photodetector is larger than a predetermined light amount, and otherwise executes control by half-duplex optical communication. And run.

The present invention further provides a first cylinder, a second cylinder branched from the first cylinder and having a smaller sectional area than the first cylinder, The first cylindrical body and the first cylindrical body from an opening side of the first cylindrical body in the injection mold having a combined body that connects an axial end of the cylindrical body and an axial end of the second cylindrical body. A core member is formed by injecting a core material into the second cylindrical body and the combined body, and a clad material is formed by filling a clad material on an outer peripheral side of the core portion, and then a core corresponding to the combined body is formed. The method employs a method of manufacturing an optical branching coupler that manufactures an optical branching coupler by removing a portion and a clad portion.

According to the above-mentioned means, since the numerical aperture of the first optical waveguide is made larger than the numerical aperture of the optical fiber, light loss in the first optical waveguide is reduced, and Can be efficiently coupled to the photodetector. Further, at least a part of the second optical waveguide means may be composed of an optical waveguide member having a smaller numerical aperture than the first optical waveguide means, or of the second optical waveguide means which is coupled to the light source. Since the numerical aperture is smaller than the numerical aperture of the first optical waveguide means, the divergence angle of the optical signal introduced from the light source to the optical waveguide member is small, and the first optical waveguide means has a smaller divergence angle. Crosstalk of the optical signal entering the photodetector through the means can be reduced.

Further, by making the step area of the first optical waveguide means larger than the step area of the second optical waveguide means, the optical signal introduced from the optical fiber is branched to the first optical waveguide means. The generated loss can be reduced, and the optical signal from the optical fiber can be efficiently guided to the photodetector.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. 1A and 1B are configuration diagrams of an optical transmission device according to a first embodiment of the present invention, in which FIG.
(B) is a side sectional view. In FIG. 1, an optical transmission device 10 is a resin module package 12 having a rectangular parallelepiped shape.
A rectangular opening 14 is formed at an axial end of the module package 12, and a female connector 16, a bidirectional optical waveguide 18, a photodetector 20, a pedestal 22, and a light-shielding film 24 are formed therein. , Optical waveguide 26, preamplifier 28,
The semiconductor laser 30, the pedestal 32, and the circuit board 34 are housed. On the circuit board 34, the female connector 16, the bidirectional optical waveguide 18, the pedestal 22, the preamplifier 28, the pedestal 32,
The light shielding film 24 is attached and the circuit board 34
A plurality of electric terminals 36 are attached to the end of the. Each of the electrical terminals 36 has an end protruding outside from the bottom side of the module package 12 so as to be connected to a power supply and other devices.

The female connector 16 has an opening 1 at its end.
4 is fixed on a circuit board 34 in a state inserted therein. A male connector 38 composed of an optical connector such as a mini jack is detachably attached to the female connector 16. A bidirectional transmission optical fiber 40 is connected to the male connector 38 as a single-core (single-core) optical fiber serving as a communication path. As the optical fiber 40,
For example, a POF having a core diameter of 0.98 mm and a numerical aperture of 0.3 is used. The optical signal transmitted through the optical fiber 40 is input to the optical transmission device 10 via the male connector 38, and the bidirectional optical waveguide 18 is coupled to the male connector 38.

The bidirectional optical waveguide 18 is provided with a photodetector coupling optical waveguide 42 and a light source coupling optical waveguide 44 as a main body of an optical branching coupler which is one element of a bidirectional optical communication device. The periphery of each of the optical waveguides 42 and 44 is covered with a cladding material (cladding). The optical waveguide 42 fetches an optical signal from the optical fiber 40 from the male connector 38 as an optical signal transmission medium connecting the optical fiber 40 and the photodetector 20, and guides the optical signal to the photodetector 20. As the wave means, for example, a core material is used. The optical waveguide 42 has a diameter of 1.1 mm on a surface facing the male connector 38 and a diameter of 0.6 mm on a surface facing the photodetector 20. It is formed in a tapered shape in which the diameter gradually decreases toward the detector 20 side. With this tapered shape,
The beam diameter can be reduced to 55%, and the energy density of light can be improved 3.3 times. The numerical aperture of the optical waveguide 42 is set to 0.5. The light detector 20 is coupled to an end of the optical waveguide 42.
The photodetector 20 is adhered and fixed to the pedestal 22 so as to face the light emitting end of the optical waveguide 42. The photodetector 20 detects an optical signal transmitted through the optical waveguide 42, converts the detected optical signal into an electric signal, and outputs the electric signal to the preamplifier 28. The preamplifier 28 amplifies the electric signal and outputs the amplified electric signal (received electric signal) from an electric terminal 36 to an external device.

On the other hand, the optical waveguide 44 is formed integrally with the waveguide 42 using a core material having a diameter of 0.25 mm as a branching path having a numerical aperture of 0.5, and is joined to the side surface of the optical waveguide 42. An optical waveguide 2 is provided at an axial end of the optical waveguide 44.
6 are connected. The optical waveguide 26 is configured using a rectangular optical waveguide member having a side of 0.1 mm, and the numerical aperture is set to 0.1. A semiconductor laser 30 as a light source is coupled to an end of the optical waveguide 26 in the axial direction. The semiconductor laser 30 is fixed on a pedestal 32 so as to have the same height as the optical waveguide 26. The semiconductor laser 30 receives a transmission electric signal from the electric terminal 36 and emits an optical signal according to the transmission electric signal to the optical waveguide 26. This optical signal is guided to the optical fiber 40 via the optical waveguide 26, the optical waveguide 44, and the male connector 38. That is, the optical waveguide 44,
Reference numeral 26 denotes a second optical waveguide unit which branches the optical signal from the optical waveguide 42 and guides an optical signal from a semiconductor laser (light source) to the optical fiber 40 via the male connector 38.
Further, since the cross-sectional area of the optical waveguide 44 is smaller than the cross-sectional area of the optical waveguide 42, that is, the cross-sectional area of the optical waveguide 42 is larger than the cross-sectional area of the optical waveguide 44. The loss of the optical signal introduced into the optical waveguide 42 can be set to 0.23 dB.

In the above configuration, the optical signal transmitted through the bidirectional transmission optical fiber 40 is input to the optical transmission device 10 connected by the male connector 38. This optical signal is transmitted through the optical waveguide 42 and is detected by the photodetector 20, and the detected optical signal is converted into an electric signal. The electric signal is amplified by the preamplifier 28, and is then received as an electric signal by the electric terminal 36. Is transmitted to an external device via On the other hand, when a transmission electric signal transmitted from an external device is input to the semiconductor laser 30 via the electric terminal 36, an optical signal according to the transmission electric signal is emitted from the semiconductor laser 30 to the optical waveguide 26. . This optical signal is transmitted through the optical waveguide 2
After transmitting the signals 6, 44, they are coupled to the male connector 38 and transmitted from the optical fiber 40 to other devices.

As described above, in this embodiment, since the numerical aperture (0.5) of the optical waveguide 42 is larger than the numerical aperture (0.3) of the optical fiber 40, the light in the optical waveguide 42 is The loss can be reduced, and the received light from the optical fiber 40 can be efficiently coupled to the photodetector 20. Further, since the numerical aperture of the optical waveguide 26 is set to 0.1 and the optical signal is made to enter the optical waveguide 44 having a large numerical aperture from the optical waveguide 26 having a small numerical aperture, the spread angle of the optical signal passing through the optical waveguide 44 is reduced. It becomes smaller and the optical fiber 40
The optical signal can be efficiently coupled to the optical waveguide 42, and the optical waveguide 42 can be coupled with the reflection at the end faces of the optical waveguide 42 and the optical fiber 40 and the scattering of light in the optical waveguide 44.
The crosstalk of the optical signal entering the photodetector 20 through the optical signal can be reduced.

In the present embodiment, the optical waveguide 2
6 has a small numerical aperture of 0.1.
The divergence angle of the light emitted from the semiconductor laser 30 is larger than the divergence angle of the light beam that can be confined in the waveguide 6, and a light beam that is not coupled to the waveguide 26 is generated. But,
A light-shielding film 24 is disposed between the photodetector 20 and the optical waveguide 26, and can absorb light beams that are not coupled to the optical waveguide 26.
Crosstalk associated with leakage to zero can be suppressed. When the optical waveguide 26 is composed of a core portion and a clad portion, crosstalk can be suppressed by using a material that absorbs light as the clad portion of the optical waveguide 26.

In the present embodiment, the optical waveguide 4
2 is larger than the cross-sectional area of the optical waveguide 44, the optical loss received when the optical signal received from the optical fiber 40 is branched from the male connector 38 to the optical waveguide 42 is reduced. An optical signal can be efficiently guided to Further, since the optical waveguide 42 has a tapered shape, light can be efficiently coupled to the high-speed photodetector 20 having a small light receiving diameter. Further, since the numerical aperture (0.5) of the optical waveguide 42 is larger than the numerical aperture (0.3) of the optical fiber 40, even if the optical waveguide 42 has a tapered shape,
Light loss in the optical waveguide 42 can be reduced.

Further, since the optical waveguide 26 is a rectangular waveguide having a side of 0.1 mm, the optical waveguide 26 is
(0.25 mm). Further, the diameter of the optical waveguide 44 is about 0.1 mm with respect to 0.25 mm.
Since there is latitude in the alignment of the optical waveguides, the alignment between the optical waveguides 44 and 26 can be easily performed. Similarly, the alignment between the optical waveguide 26 and the semiconductor laser 30 has a margin in the alignment, so that the alignment can be easily performed. Since the female connector 16, the bidirectional waveguide 18, the optical waveguide 26, and the pedestal 32 are mounted on the same circuit board 34, the height of the circuit board 34 can be adjusted by adjusting the heights of the optical axes. There is no need for position adjustment in the vertical direction.

As the bidirectional optical waveguide 18, for example, a light separating / coupling device described in JP-A-11-183743 can be used.

In forming the bidirectional optical waveguide 18,
When the numerical aperture of the optical waveguide 42 is set to 1.5 times or more the numerical aperture of the optical fiber 40 coupled to the optical waveguide 42, the reduction ratio of the beam diameter may be 0.5 or less and the area ratio may be 0.25 or less. Desirably, when the numerical aperture of the optical waveguide 42 is at least twice the numerical aperture of the optical fiber 40, the area ratio is desirably 0.1 or less. The POF has a numerical aperture of 0.3 for high-speed communication.
The numerical aperture of 2 is preferably 0.6 or more if 0.45 or more is possible. Also, the wavelength normally used for optical communication is 57
It is about 0 nm to 1550 nm, and it is sufficient if the numerical aperture is equal to or larger than the numerical aperture at a wavelength used within this range.

As described above, when forming the optical branching coupler including the bidirectional optical waveguide 18 and the optical waveguide 26, the numerical aperture of the optical fiber 40 is set to NA1, the numerical aperture of the optical waveguides 42 and 44 is set to NA2, and the optical waveguide is set to NA2. By setting each numerical aperture to a value satisfying the relationship of NA3 <NA1 <NA2...
0 can be efficiently coupled to the photodetector 20, the optical signal from the semiconductor laser 30 can be efficiently coupled to the optical fiber 40, and the optical signal incident on the photodetector 20 Crosstalk can be reduced.

It should be noted that the numerical aperture NA is such that the refractive index of the core is n
1, it is possible to determine the refractive index of the cladding is taken as n2, by ^{NA = (n1 2 -n2 2)} 1/2 ...... (2).

As described above, for the optical fiber 40 having a numerical aperture of 0.3, the numerical aperture of the optical waveguide 42 is preferably 0.45 or more, and preferably 0.6 or more. On the other hand, the optical waveguide 2
The numerical aperture of 6 suppresses optical signal crosstalk,
It is desirable that the distance between the optical waveguide 42 and the optical waveguide 44 be small.
Since the ratio of the light amount of the light beam coupled to the optical waveguide 26 in the light amount of the light beam emitted from the
It is desirable to be 5 or more. By setting the numerical aperture of the optical waveguide 26 to 0.05 or more, the light utilization efficiency becomes 10% or more when a general edge emitting semiconductor laser is used as the semiconductor laser 30, and a general optical output 5 mW semiconductor laser is used. Even when used, an optical output of 0.5 mW can be obtained. When the numerical aperture of the optical fiber 40 is 0.3, the optical waveguide 2
6, the optical waveguide 42 and the optical waveguide 44 are too close to each other, and the photodetector 20 and the optical waveguide 2
Since it becomes difficult to set the numerical aperture 6, the numerical aperture of the optical waveguide 26 is desirably 0.25 or less.

In the above embodiment, the semiconductor laser 30 and the optical waveguide 44 are connected using the rectangular optical waveguide 26, but an optical fiber can be used instead of the optical waveguide 26. In this case, what satisfies NA3 of the equation (1) should be selected as the numerical aperture of the optical fiber.

In the above embodiment, the optical waveguide 4
Since the light rays from the two end faces are coupled to the photodetector 20,
There is no need to form a mirror on the end face of the optical waveguide 42,
The production of the optical waveguide 42 becomes easy.

Next, a method of manufacturing the bidirectional optical waveguide 18 constituting the main body of the optical branching coupler will be described with reference to FIG.

First, as shown in FIGS. 2A and 2B,
A first cylindrical body corresponding to the shape of the core portion 50;
And a resin liner 46 and a combined body corresponding to the shape of the bridge portion 54 connecting the axial end of the first cylindrical body and the axial end of the second cylindrical body. A resin as a core material is injected into the injection mold from the resin liner 46 into the first cylinder of the injection mold, and the resin liner 46, the cores 50 and 52 are prepared. , The bridge portion 54 is formed. FIG. 2 shows a state in which each injection mold is removed. The core part 50 is the optical waveguide 4
As a second core portion, the core portion 52 is formed as a core portion of the optical waveguide 44, and axial ends of the core portions 50 and 52 are joined by a bridge portion 54. That is, since the injection molded resin from the core portion 50 passes around the core portion 52 through the bridge portion 54, the resin can be sufficiently injected also into the core portion 52 having a smaller diameter than the core portion 50.

Subsequently, the resin liner 46, the core portions 50, 5
2. After removing the mold of the bridge portion 54, FIG.
As shown in (d), the molded core portions 50, 52 are sandwiched between a pair of substrates 56, 58, and the resin liner 46 and the bridge portion 54 are fitted into a mold 60 formed of a transparent material, thereby forming the core portion 50. , 52 are fixed. By using the mold 60, the core portions 50 and 52 can be
And the substrate 58.

Subsequently, an ultraviolet curable resin 62 is filled between the substrate 56 and the substrate 58 and irradiated with ultraviolet light 64 through the substrates 56, 58 and the mold 60, thereby curing the ultraviolet curable resin 62, The cladding of the wave path 18 is used. In this case, the substrates 56 and 58 may be made of a material that transmits ultraviolet light, and a glass plate, a transparent plastic plate, or the like can be used. Further, in order to determine the positions of the core portions 50 and 52 more accurately, the core portions 50 and
A groove may be provided in advance in accordance with the shape of FIG.

Finally, as shown in FIGS. 2 (e) and 2 (f), the resin liner 46 and the bridge portion 54 are cut out of the clad portion 66 formed around the core portions 50, 52, and the substrate 56, In accordance with 58, the end faces in the axial direction of the core portions 50 and 52 are polished as light input / output surfaces. Then, after the end faces are polished, the substrates 56 and 58 are cut and separated for each optical waveguide 18. In this case, the core part 50 forms the optical waveguide 42, and the core part 52 forms the optical waveguide 44.
Further, one end of the core 50 is connected to the optical fiber coupling end 68,
The other end surface of the core part 50 becomes the light emitting end 70, and one end of the core part 52 becomes the light incident end 72.

In this embodiment, PMMA having a refractive index of 1.49 is used as the injection molding resin, and the ultraviolet curing resin 6 is used.
2. Since an optical waveguide having a refractive index of 1.40 was used for the optical waveguide 4,
The numerical aperture of 2,44 is 0.5.

In the present embodiment, a plurality of core portions 50 and 52 can be simultaneously formed by one injection molding, and the substrates 56 and 58 which are previously adjusted to the lengths of the core portions 50 and 52 are used. Thus, the optical waveguide 42,
It is possible to reduce the error in the length of the axis 42 in the axial direction.
When molding the core portions 50 and 52, a bridge portion 54 is formed, the core portion 50 and the core portion 52 are fixed by the bridge portion 54, and the periphery of the core portions 50 and 52 is cured by an ultraviolet curable resin 62.
After the fixing, the bridge portion 54 is cut, so that the positions of the optical waveguide 42 and the optical waveguide 44 can be accurately determined without a displacement of the core portion 50 and the core portion 52 after the cutting. .

In the present embodiment, the core 50
Although the resin is injected from the optical fiber coupling end 68 side of the mold, the resin can be injected from the bridge portion 54 side, and when the mold surface on the optical fiber coupling end 68 side is smoothed, the optical fiber There is no need to grind the coupling end 68.

Further, in the present embodiment, the center line of the optical waveguide 42 and the center line of the optical waveguide 44 are connected at an angle at the joint between the optical waveguide 42 and the optical waveguide 44. The optical waveguide 42 or the optical waveguide 44 has a certain curvature, and the center line of the optical waveguide 42 and the center line of the optical waveguide 44 are substantially parallel to each other at the coupling portion between the optical waveguide 42 and the optical waveguide 44 so that the optical fiber coupling end 68 It can also be vertical. In this case, the optical waveguide 44
Is transmitted almost perpendicularly to the optical fiber coupling end 68, and the male connector 38 and the optical connector 44 are compared with the case where the center line of the optical waveguide 44 is inclined with respect to the center line of the optical waveguide 42. Of the optical signals reflected at the end face of the fiber 40, the amount of the optical signal incident on the optical waveguide 42 is reduced, and the crosstalk of the optical signal during transmission can be further reduced.

As described above, since the optical waveguide 18 in this embodiment can be manufactured by injection molding, it can be manufactured in a large amount in a short time, and the bidirectional optical waveguide 18 has a larger diameter than that manufactured by photography. Optical waveguide 1
8 can be manufactured, and the transmission efficiency of the received light can be increased. Further, the optical waveguide 42 having a circular cross section similar to the cross sectional shape of the optical fiber 40 can be manufactured.
Therefore, the bidirectional optical waveguide 18 shown in the present embodiment is suitable for a plastic optical fiber having a large diameter. However, the bidirectional optical waveguide 18 used in the present invention is not limited to the manufacturing method shown in the present embodiment, and the optical waveguide 4 may be used as in the case where the diameter of the optical fiber 40 is small.
In the case where the cross-sectional shape of 2, 44 can be reduced, a light branching method is appropriately selected by a manufacturing method such as an ultraviolet curing method, a wet etching method, a reactive ion etching method, a photopolymerization method, or a method of bonding an optical fiber. A coupler can be manufactured.

The bidirectional optical waveguide 18 in the present embodiment is suitable for an optical fiber 40 having a large diameter, and is not limited to a plastic optical fiber in which the core and the clad are formed of plastic, but only the clad is formed of plastic. Things can also be targeted.

The material of the core (core portion) and the cladding (cladding portion) used in the optical branching coupler according to the present invention is selected from acrylic, methacrylic, carbonate, non-magnetic, and so on so as to have a desired numerical aperture. Amorphous olefin-based, sulfone-based, silicone-based, vinyl-based, fluorine-based compounds, and the like can be appropriately used in combination. in this case,
The material is not limited to an organic material, and glass may be used. For the cladding, a transparent inorganic material such as silicon oxide or silicon nitride, or a thin film material may be used.

Next, a second embodiment of the optical transmission device according to the present invention will be described with reference to FIG. FIG. 3A is a top sectional view of the optical transmission device, and FIG. 3B is a side sectional view of the optical transmission device. In FIG. 3, the optical transmission device 1 according to the present embodiment
0a is provided with a resin module package 12a whose dimension in the height direction is larger than the module package 12, and a female connector 16a whose dimension in the height direction is larger than the female connector 16 is mounted in the opening 14. ing.
A male connector 38 is detachably attached to the female connector 16a, and a bidirectional transmission optical fiber 40 having a numerical aperture of 0.3 is attached to the male connector 38 similarly to the above embodiment.
Is connected. The female connector 16a is connected to the circuit board 34.
Fixed above, the male connector 38 is coupled to the bidirectional optical waveguide 18. The bidirectional optical waveguide 18 is configured in the same manner as in the above embodiment, and includes an optical system pedestal 74.
And is fixed on the circuit board 34 via the. An optical fiber (P) having a core diameter of 0.7 mm and a numerical aperture of 0.6 is provided on the light emitting end side of the optical waveguide 42 in the bidirectional optical waveguide 18.
OF) 76 is coupled, and the axial end face of the optical fiber 76 is coupled to a photodetector package 80 via a lens 78. The photodetector package 80 contains a photodetector and a preamplifier, and the photodetector package 80 is fixed to a substrate 82. The board 82 is fixed to the circuit board 34 so as to be substantially perpendicular to the circuit board 34, and the electric circuit 8 on the circuit board 34.
4, connected to the electrical terminal 36;

On the other hand, the optical waveguide 4 as the first optical waveguide
2 is coupled with an optical fiber 76 as a first optical waveguide member, whereas in the present embodiment, the second optical waveguide member is provided on the axial end face of the optical waveguide 44 as a second optical waveguide. The light source coupling optical fiber 86 is coupled. Each of the optical fibers 76 and 86 is fixed by a V-groove substrate 88, and the V-groove substrate 88 is fixed on the optical system pedestal 74. The light source coupling optical fiber 86 is, for example,
A hard polymer clad optical fiber (HPCF) having a core diameter of 0.2 mm and a numerical aperture of 0.1 is used. The end face in the axial direction of the optical fiber 86 is coupled to the semiconductor laser package 92 via the lens 90. A semiconductor laser as a light source is housed in the semiconductor laser package 92 as in the above embodiment, and the semiconductor laser package 92 is fixed to the substrate 82 so that the optical axis is substantially parallel to the circuit board 34. I have. The semiconductor laser housed in the semiconductor laser package 92 is also connected to the electric circuit 84 and the electric terminal 36 via the circuit wiring of the substrate 82.

In the optical transmission device 10a having the above configuration, when receiving the optical signal transmitted through the optical fiber 40, the optical signal transmitted through the optical fiber 40 is input to the optical transmission device 10a via the male connector 38. This optical signal is incident on the bidirectional optical waveguide 18. This optical signal is coupled to the optical fiber 76 via the optical waveguide 42, detected by the photodetector in the photodetector package 80 via the lens 78, and the detected optical signal is converted into an electric signal. And is output from the electric terminal 36 to another device or the like as a received electric signal. In this case, since the lens 78 is fixed to the photodetector package 80, the optical signal from the optical fiber 76 can be efficiently coupled to the photodetector.

On the other hand, when transmitting an optical signal, when a transmission electric signal is input to the electric terminal 36 from another device or the like, an optical signal according to the electric signal is transmitted from the semiconductor laser in the semiconductor laser package 92 to the lens 90. Is emitted into the optical fiber 86 via the optical fiber 86. After transmitting the optical signal through the optical fiber 86, the optical signal is coupled to the optical waveguide 42 via the optical waveguide 44, and further coupled to the male connector 38 and the optical fiber 40 to transmit the optical fiber 40. In this case, since the lens 90 is fixed to the semiconductor laser package 90, an optical signal from the semiconductor laser can be efficiently coupled to the optical fiber 86.

As described above, in the present embodiment, when forming the optical branching coupler using the bidirectional optical waveguide 18 and the optical fibers 76 and 86, the numerical aperture of the fiber 40 is set to NA.
1. The numerical aperture of the bidirectional optical waveguide 18 is NA2, the numerical aperture of the optical fiber 76 is NA4, and the numerical aperture of the optical fiber 86 is NA.
By setting each numerical aperture to a value satisfying the relationship of NA5 <NA1 <NA2 ≦ NA4 (3), the optical fiber 4
0 can be efficiently detected by the photodetector, and the optical signal from the semiconductor laser can be efficiently coupled to the optical fiber 40. In addition, the optical signal can be transmitted from the optical waveguide 44 to the photodetector via the optical waveguide 42. Crosstalk of an incident optical signal can be reduced.

By making the numerical aperture of the optical fiber 76 larger than the numerical aperture of the bidirectional optical waveguide 18, the optical signal from the optical waveguide 42 can be efficiently coupled to the optical fiber 76.

For the optical fiber 40 having a numerical aperture of 0.3, the numerical aperture of the bidirectional optical waveguide 18 and the optical fiber 76 is preferably 0.45 or more, and preferably 0.6 or more.

In the present embodiment, the bidirectional optical waveguide 18 and the semiconductor laser are coupled using the optical fiber 86,
Since the bidirectional optical waveguide 18 and the photodetector are coupled using the optical fiber 76, the positions of the photodetector package 80 and the semiconductor laser package 92 are adjusted according to the lengths of the optical fibers 76 and 86. Each package can be installed in a place where there is room. The semiconductor laser package 9
By disposing the photodetector package 80 apart from the photodetector package 80, electrical crosstalk can be reduced.

Even if the optical waveguides 42 and 44 are close to each other, the optical fibers 76 and 86
And the angle between the optical waveguide 42 and the optical waveguide 44 does not need to be increased.

Therefore, according to the present embodiment, it is possible to reduce the crosstalk of the optical signal as compared with the above embodiment.

The diameter of the optical fiber 86 is made smaller than that of the optical waveguide 44, and the diameter of the optical fiber 76 is made smaller than that of the optical waveguide 42.
The diameter of the optical waveguides 42, 4
4. The tolerance of the installation place of the optical fibers 76 and 86 is increased and the alignment is easy. Furthermore, by using a smaller diameter than the bidirectional transmission optical fiber 40 as the optical fiber 76, a photodetector having a smaller light receiving diameter can be used as the photodetector, and the signal pass band of the optical transmission device 10 can be reduced. Can be bigger.

In this embodiment, since the photodetector package 80 in which the photodetectors are hermetically sealed and the semiconductor laser package 92 in which the semiconductor lasers are hermetically sealed are used, the module housing 12a has an airtight structure. Therefore, the optical transmission device 10 can be easily assembled. Further, since the semiconductor laser and the photodetector are hermetically sealed in the package, the crosstalk of the optical signal directly entering the photodetector package 80 from the semiconductor laser package 92 is reduced. In the present embodiment,
Although the bidirectional optical waveguide 18, the semiconductor laser, and the photodetector are connected using the optical fibers 76 and 86, respectively, an optical waveguide may be used instead of the optical fibers 76 and 86. In this case, the position of the optical waveguide can be precisely formed, and the connection margin with the bidirectional optical waveguide 18 can be designed to be small. In addition,
Instead of hermetically sealing the semiconductor laser and the photodetector with a package, the semiconductor laser element and the photodetector can be directly attached to the optical fiber. In this case, the size of the optical transmission device 10 can be reduced. However, in this case, it is necessary to hermetically seal the module package 12a.

On the other hand, when fixing the V-groove substrate 88, the relative position with respect to the bidirectional optical waveguide 18 is adjusted and then fixed to the optical system pedestal 74.

More specifically, as shown in FIG.
The optical fibers 76 and 86 are sandwiched between the groove substrates 88a and 88b,
The optical fiber 76 is mounted in the optical fiber V-grooves 94a and 96b, and the optical fiber 86 is mounted on the optical fiber V-grooves 96a and 96b.
6b, the optical fibers 76 and 86 are fixed. The optical fiber V-grooves 94a, 94b, 96a, 96b are formed in accordance with the diameters of the optical fibers 76, 86, respectively.
The distance between the grooves 96a and 96b is set to be the same as the distance between the end faces of the optical waveguide 42 and the optical waveguide 44. Further, since the bidirectional optical waveguide 18 is connected to the semiconductor laser and the photodetector by using the optical fibers 76 and 86, respectively, the cross-sectional shape can be made the same as that of the bidirectional optical waveguide 18 having a circular cross section. It will be easier.

In the present embodiment, when forming the bidirectional waveguide 18 shown in FIG. 2, the core portions 50 and 52 provided with the bridge portions 54 are used.
And the position of the optical waveguide 44 can be accurately determined.
Further, since the alignment accuracy between the bidirectional optical waveguide 18 and the optical fibers 76 and 86 is not strict, the accuracy of the shape required for the V-groove substrate 88 is not strict, and the V-groove substrate 88 can be formed by injection molding. . In addition, the alignment accuracy between the bidirectional optical waveguide 18 and the V-groove substrate 88 is low, and
Easy alignment. That is, the bidirectional optical waveguide 18 and the V-groove substrate 88 can be positioned and fixed by abutting each other. In this case, if the height of the center of the bidirectional optical waveguide 18 and the thickness of the V-groove substrate 88 are accurately adjusted, the alignment can be performed only in the horizontal direction. Alternatively, a guide for positioning may be provided on the bidirectional optical waveguide 18 and the V-groove substrate 88 so that the assembly can be performed without adjustment.

Next, another embodiment of the optical branching coupler according to the present invention will be described with reference to FIG. FIG. 5A is a perspective view of the optical branching coupler, and FIG. 5B is a cross-sectional view of the optical branching coupler. In the optical branching coupler according to the present embodiment, the core (core portion) of the bidirectional optical waveguide 18 is formed by using two types of core materials as equivalent to the bidirectional optical waveguide 18.
That is, a first core (core portion) 100 that forms the optical waveguide 42 of the bidirectional optical waveguide 18 and a second core (core portion) 102 that mainly forms the optical waveguide 44 are formed on the substrate 98. The second core 1 is also provided around the first core 100.
02 is formed. A clad (cladding portion) 104 using a clad material is formed around each second core 102 so as to cover the entirety. The first core 100 and the second core 102 are formed using a photolithography process, and the clad 104 is formed using an ultraviolet curable resin.

In this embodiment, when the refractive index of the first core 100 is n1, the refractive index of the second core 102 is n2, and the refractive index of the cladding 104 is n3, each refractive index is n3 <N2 <n1... (4) For this reason, the numerical aperture of the optical waveguide 44 by the second core 102 is the first core 1
02 is smaller than the numerical aperture of the optical waveguide 42.

Therefore, by using the bidirectional optical waveguide 18 in this embodiment, the light source coupling optical waveguide 4
The numerical aperture of the light beam passing through 4 can be made smaller than that of the optical waveguide 42 for coupling a photodetector. Therefore, the optical fiber 7
6, 86, the optical waveguide 4 without using the optical waveguide 26.
The semiconductor laser as a light source can be directly coupled to the light incident end 106 of the optical waveguide 4, and the photodetector 20 can be directly coupled to the light emitting end 108 of the optical waveguide 42.

As described above, according to the optical branching coupler of the present embodiment, it is possible to reduce the crosstalk in which the optical signal from the light source goes around the photodetector and to efficiently receive the light from the optical fiber. It can lead to a light detector.

In the present embodiment, the first core 100
, The second core 102 is formed so that no gap is formed between the first core 100 and the second core 102. Further, the first core 100 constituting the optical waveguide 42 is composed of the second core 102 and the clad 1
04 and the first core 1
Since the light is confined at the interface between the first core 100 and the second core 102, the light having a numerical aperture determined by the first core 100 and the clad 104 can be substantially confined.

In this embodiment, the cross section of the bidirectional optical waveguide 18 has a rectangular shape, but the length of one side at the joint 110 with the optical fiber is made larger than the diameter of the optical fiber 40 and the optical waveguide 44, the optical waveguide 4
The optical waveguide 42 is shifted so that all the light beams emitted from the optical fiber 4 enter the circular optical fiber 40.
Can be combined with By shifting in this manner, light can be efficiently coupled to the optical fiber 40 having a circular cross-sectional shape even if a square cross-sectional shape is used.

Next, another embodiment of the optical branching coupler according to the present invention will be described with reference to FIG.

FIG. 6A is a perspective view of a first core constituting a bidirectional optical waveguide, FIG. 6B is a perspective view of a first core and a second core of the bidirectional optical waveguide, and FIG. It is sectional drawing of a bidirectional optical waveguide. In FIG. 6, the optical branching coupler according to the present embodiment is a bidirectional optical waveguide corresponding to the bidirectional optical waveguide 18, in which the core of the bidirectional optical waveguide 18 is formed using two types of core materials. That is, as shown in (a), the first cores 112 and 114 are integrally formed on the optical waveguide substrate 98. The first core 112 corresponds to the optical waveguide 44, and the first core 114 corresponds to the optical waveguide 42. A second core 116 is formed around the first core 114. further,
A cladding 118 is formed so as to cover the periphery of the first core 112 and the second core 116. First core 11
2, 114 and the second core 116 are made using a photolithographic process and the cladding 118
Are formed using an ultraviolet curable resin.

In the present embodiment, the first core 11
Assuming that the refractive indices of 2, 114 are n1, the refractive index of the second core 116 is n2, and the refractive index of the cladding 118 is n3, the respective refractive indices have a relationship of n3 <n1 <n2 (5). It is set to a value that satisfies. Therefore, in the second core 116 and the clad 118 constituting the optical waveguide 42, an optical waveguide having a large numerical aperture can be formed between the second core 116 and the clad 118, and the optical waveguide 44 can be formed.
In the first core 112 and the cladding 118 constituting the optical waveguide, an optical waveguide having a small numerical aperture can be formed by the first core 112 and the cladding 118.

Therefore, also in the bidirectional optical waveguide 18 of this embodiment, a semiconductor laser as a light source is directly coupled to the light incident end 120 of the bidirectional optical waveguide 18 without using the optical fibers 76, 86 and the optical waveguide 26. And a photodetector can be directly coupled to the light exit end 122.

Next, an embodiment of the optical communication apparatus will be described with reference to FIG. FIG. 7 is a block diagram showing an embodiment of an optical communication device using the optical transmission device 10 or 10a. In FIG. 7, an optical communication device 200 is an optical transmission device 10.
Or 10a, and the physical layer circuit 20
2. The female connector 16 or 16 of the optical transmission device 10 or 10a
A male connector 38 is detachably mounted on a, and an optical fiber 40 is connected to the male connector 38. The bidirectional optical waveguide 18 is coupled to the male connector 38, and the photodetector 20 and the semiconductor laser 30 are coupled to the bidirectional optical waveguide 18. The photodetector 20 is connected to a preamplifier 28 that amplifies an electric signal generated by the output of the photodetector 20, and the semiconductor laser 30 is connected to an electric circuit (drive circuit) 84 that drives the semiconductor laser 30. The optical transmission device 10 or 10a performs optical communication with the optical transmission device of the other party, receives an optical signal from the optical transmission device of the other party,
The received optical signal is converted into an electric signal and converted into a physical layer circuit 202.
, And converts an electrical signal from the physical layer circuit 202 into an optical signal and transmits the optical signal to the optical transmission device on the other side via the optical fiber 40.

The physical layer circuit 202 includes a plurality of modulation circuits 206 and 208 for modulating an input signal, and a plurality of demodulation circuits 210 and 21 for demodulating and outputting a signal from the optical transmission apparatus 10.
2, each modulation circuit 206, 208 and each demodulation circuit 21
0, 212 and a control circuit 214 for controlling the operation of the control circuit. The control circuit 214 controls each demodulation circuit 210,
A control signal for controlling each of the modulation circuits 206 and 208 and the demodulation circuits 210 and 212 is generated according to a signal from the signal 212 and a control signal and data from the link layer circuit 204, and the data for transmitting information is modulated by the modulation circuit. 206 and 208.

More specifically, the physical layer circuit 202 performs coding suitable for optical communication, arbitration for determining a node to transmit a signal when a plurality of nodes are connected, optical transmission device 10 or 10
Control such as connection management for managing whether or not a partner optical transmission device is connected to a is performed. Specifically, this encoding is performed so that the clock signal can be reproduced.
It is converted into a 4B / 5B or 8B / 10B code to which a code has been added. On the other hand, in the link layer circuit 204, the optical communication device 2
The host that connects 00 and the physical layer circuit 202 are interfaced to transmit and receive packets.

For example, by using the optical transmission device 10, crosstalk in bidirectional communication can be reduced, so that full-duplex optical communication can always be performed. For this reason,
When performing full-duplex communication, encoding and arbitration are performed by the modulation circuit 206. In this case, by performing data communication and performing full-duplex communication as communication for arbitration using the other communication path, the utilization efficiency of the transmission path can be improved. The received signal is demodulated by the demodulation circuit 210, and data and an arbitration signal are detected.

On the other hand, when performing half-duplex communication, encoding and arbitration are performed by the modulation circuit 208. In this case, arbitration is performed at a time when data communication is not performed. This arbitration code is transmitted using a code not used for data. The demodulation circuit 212 demodulates the received signal, and detects data and an arbitration signal. Switching between full-duplex communication and half-duplex communication is performed by the control circuit 214.

The switching between the full-duplex communication and the half-duplex communication is determined by negotiating the communication system between the optical communication devices when the optical communication device 200 is connected to another optical communication device. A factor that makes full-duplex communication impossible is that the length of the optical fiber becomes longer and the amount of received light decreases, so that the influence of crosstalk becomes relatively large.

Therefore, the amount of received light is detected at the time of initial connection, and when the amount of light is more than a certain value, full-duplex communication is selected.
If the amount of light is insufficient, the half-duplex communication method is selected.
In other words, when the amount of received light is large and crosstalk is not a problem and the occurrence of errors is small, optical communication is performed in full duplex,
Conversely, when the amount of received light is small and an error occurs due to crosstalk, half-duplex optical communication is performed.
Further, the POF has a large transmission loss and a large change in the amount of light depending on the transmission distance. Therefore, this embodiment is effective when switching between full-duplex communication and half-duplex communication, particularly when optical communication is performed using a POF.

Further, for half-duplex communication, it can be connected to a conventional optical communication device having large crosstalk. Furthermore, by enabling full-duplex communication,
It can also be connected to an optical communication device for a two-core optical fiber. When connecting an optical communication device for a two-core optical fiber, a single-core / two-core optical fiber converter may be formed and connected using an optical demultiplexer / coupler. Either one may be selected depending on the error occurrence status at the time of initial connection other than the received light amount. The error rate can be determined by the frequency of error correction by the error correction code. Alternatively, the communication method may be determined by calculating the transmission delay time. The arbitration method can be changed in accordance with the switching of the communication method.
The switching of the communication method may be such that an error occurrence situation is measured at regular time intervals even after the communication is started, and the communication method is dynamically changed.

By performing bidirectional communication using one optical fiber, the number of optical fibers is reduced as compared with the case where one optical fiber is used for each of transmission and reception. Optical fibers can be laid.

Further, the optical transmission device and the optical connector can be reduced in size, and the transmission speed can be increased by performing full-duplex communication.

[0089]

As described above, according to the present invention,
Since the numerical aperture of the first optical waveguide is made larger than the numerical aperture of the optical fiber, the optical loss in the first optical waveguide is reduced, and the optical signal from the optical fiber is efficiently transmitted to the photodetector. Since the light guide member can be coupled and at least a part of the second optical waveguide means is constituted by an optical waveguide member having a smaller numerical aperture than the first optical waveguide means, the light introduced from the light source into the optical waveguide member is provided. The spread angle of the signal is reduced, and the crosstalk of the optical signal entering the photodetector from the second optical waveguide through the first optical waveguide can be reduced.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing a first embodiment of an optical transmission device according to the present invention, wherein FIG. 1A is a top sectional view and FIG. 1B is a side sectional view.

FIGS. 2A to 2F are process explanatory views for explaining a method for manufacturing a bidirectional optical waveguide.

3A and 3B are diagrams illustrating a second embodiment of the optical transmission device according to the present invention, wherein FIG. 3A is a top cross-sectional view and FIG. 3B is a side cross-sectional view.

FIG. 4 is a sectional view of a V-groove substrate.

FIGS. 5A and 5B are diagrams showing one embodiment of the optical branching coupler according to the present invention, wherein FIG. 5A is a perspective view and FIG.

6A and 6B are diagrams illustrating another embodiment of the optical branching coupler according to the present invention, wherein FIG. 6A is a perspective view of a first core, and FIG. 6B is a perspective view of a first core and a second core. , (C) is a sectional view.

FIG. 7 is a block diagram of an optical communication device according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 optical transmission device 12, 12a module package 14 opening 16, 16a female connector 18 bidirectional optical waveguide 20 photodetector 22 pedestal 24 light shielding film 26 optical waveguide 28 preamplifier 30 semiconductor laser 32 pedestal 34 circuit board 36 electric terminal 38 male Type connector 40 Optical fiber for bidirectional transmission 42 Optical waveguide for photodetector coupling 44 Optical waveguide for light source coupling 46 Resin liner 48 Resin inflow 50, 52 Core section 54 Bridge section 56, 58 Optical waveguide board 60 Mold 62 UV curing Resin 64 Ultraviolet light 76 Optical fiber 78 Lens 80 Photodetector package 82 Substrate 84 Electrical circuit 86 Light source coupling optical fiber 88 V-groove substrate 100 First core 102 Second core 104 Clad 112, 114 First core 116 Second Core 118 clad 20 Optical communication device 202 physical layer circuit 204 link layer circuit 206, 208 modulating circuit 210, 212, demodulation circuit 214 control circuit

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) H04B 10/02 H04B 9/00 U 10/24 G (72) Inventor Tomiya Abe 5-chome, Hidakacho, Hitachi City, Ibaraki Prefecture No. 1-1 Hitachi Cable, Ltd. Research Institute of Technology (72) Inventor Mitsuki Hirano 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Cable, Ltd. Research Institute of Technology CA07 5F073 AB25 FA23 FA29 FA30 5F088 BA16 BB01 EA07 EA09 EA11 JA03 JA14 5F089 AA01 AC10 AC11 AC16 AC17 CA03 5K002 AA01 AA03 BA04 BA13 BA31 DA05 DA42 FA01

Claims (13)

[Claims] A first optical waveguide means for guiding an optical signal from the optical fiber to a photodetector as an optical signal transmission medium connecting the optical fiber and the photodetector; and a first optical waveguide means branched from the first optical waveguide means. Second optical waveguide means for guiding an optical signal from a light source to the optical fiber, the first optical waveguide means having a larger numerical aperture than the optical fiber, and the second optical waveguide means. An optical splitter / coupler wherein at least a part of the means is constituted by an optical waveguide member having a smaller numerical aperture than the first optical waveguide means. 2. An optical signal transmission medium for connecting an optical fiber and a photodetector, a first optical waveguide means for guiding an optical signal from the optical fiber to the photodetector, and a first optical waveguide means branched from the first optical waveguide means. Second optical waveguide means for guiding an optical signal from a light source to the optical fiber, the first optical waveguide means having a larger numerical aperture than the optical fiber, and the second optical waveguide means. The optical branching means comprises an optical waveguide having a larger numerical aperture than the optical fiber, and an optical waveguide member coupled to the optical waveguide and the light source and having a smaller numerical aperture than the first optical waveguide means. Combiner. 3. The numerical aperture of the optical fiber is NA1,
When the numerical aperture of the first optical waveguide means is NA2 and the numerical aperture of the optical waveguide member is NA3, each numerical aperture is set to a value satisfying a relationship of NA3 <NA1 <NA2. The optical branching coupler according to claim 2, wherein: 4. An optical signal transmission medium for connecting an optical fiber and a photodetector, a first optical waveguide means for guiding an optical signal from the optical fiber to the photodetector, and a first optical waveguide means branched from the first optical waveguide means. Second optical waveguide means for guiding an optical signal from a light source to the optical fiber, wherein the first optical waveguide means has a first optical waveguide having a larger numerical aperture than the optical fiber, A first optical waveguide member having a larger numerical aperture than the first optical waveguide coupled to the optical waveguide and the photodetector, wherein the second optical waveguide means is larger than the optical fiber. A light constituted by a second optical waveguide having a large numerical aperture, and a second optical waveguide member coupled to the second optical waveguide and the light source and having a smaller numerical aperture than the first optical waveguide means. Branch coupler. 5. The numerical aperture of the optical fiber is NA1,
When the numerical aperture of the first optical waveguide is NA2, the numerical aperture of the first optical waveguide member is NA4, and the numerical aperture of the second photoconductive member is NA5, the respective numerical apertures are: N
The optical branching coupler according to claim 4, wherein the value is set to satisfy a relationship of A5 <NA1 <NA2≤NA4. 6. An optical signal transmission medium for connecting an optical fiber and a photodetector, a first optical waveguide means for guiding an optical signal from the optical fiber to the photodetector, and a first optical waveguide means branched from the first optical waveguide means. A second optical waveguide means for guiding an optical signal from the light source to the optical fiber, the first optical waveguide means having a first core and a clad covering the first core. An optical waveguide, wherein the second optical waveguide means is constituted by a second optical waveguide having a second core and a clad covering the second core, and a refractive index of the first core. Where n1 is the refractive index of the second core, n2 is the refractive index of the cladding, and n3 is the refractive index of the clad, the light having a refractive index set to satisfy a relationship of n3 <n2 <n1. Branch coupler. 7. The optical branching coupler according to claim 6, wherein the second core is inserted between the first core and the clad in the first optical waveguide. . 8. An optical signal transmission medium connecting an optical fiber and a photodetector, a first optical waveguide means for guiding an optical signal from the optical fiber to the photodetector, and a first optical waveguide means branched from the first optical waveguide means. Second optical waveguide means for guiding an optical signal from a light source to the optical fiber, wherein the first optical waveguide means includes a first core, a second core covering the first core, and each of the first core and the second core. It is constituted by a first optical waveguide having a clad covering a core, and the second optical waveguide means is constituted by a second optical waveguide having the first core and a clad covering the first core. When the refractive index of the first core is n1, the refractive index of the second core is n2, and the refractive index of the cladding is n3, the respective refractive indices are n3 <n1 <
An optical splitter / coupler set to a value satisfying the relationship of n2. 9. The optical branching device according to claim 1, wherein a cross-sectional area of the first optical waveguide is larger than a cross-sectional area of the second optical waveguide. Combiner. 10. An optical coupler coupled to an optical fiber, a photodetector coupled to the optical coupler for detecting an optical signal from the optical coupler, and coupled to the optical coupler. And a light source for outputting an optical signal to the optical branching / coupling device, wherein the optical branching / coupling device includes the optical branching / combining device according to any one of claims 1 to 9. Characteristic optical transmission device. 11. An optical splitter / coupler coupled to an optical fiber serving as a communication path; a photodetector coupled to the optical splitter / coupler for detecting an optical signal from the optical splitter / coupler; A light source coupled to a coupler for outputting an optical signal to the optical branching coupler; a plurality of demodulating circuits for demodulating an optical signal detected by the photodetector; and a light source for modulating data and modulating the signal. A plurality of modulation circuits that output data to the plurality of demodulation circuits, and a control circuit that controls operations of the demodulation circuits and the modulation circuits based on signals from the plurality of demodulation circuits and outputs data to the plurality of modulation circuits. The control circuit is an optical communication device that switches between control by full-duplex optical communication and control by half-duplex optical communication in accordance with the state of an optical signal detected by the photodetector, wherein the optical branching coupler As
An optical communication device comprising the optical branching coupler according to any one of claims 1 to 9. 12. The control circuit executes control by full-duplex optical communication when the light amount of the optical signal detected by the photodetector is larger than a predetermined light amount; otherwise, the control circuit performs control by half-duplex optical communication. The optical communication device according to claim 11, wherein the optical communication device is executed. 13. A first cylinder, a second cylinder branched from the first cylinder and having a smaller sectional area than the first cylinder, and an axial direction of the first cylinder. The first cylindrical body and the second cylindrical body from the opening side of the first cylindrical body in the injection molding die having an end portion and a combined body connecting an axial end portion of the second cylindrical body. And forming a core portion by injecting a core material into the combined body, forming a clad portion by filling the outer peripheral side of the core portion with a clad material, and then forming a core portion and a clad portion corresponding to the combined body. A method of manufacturing an optical branching coupler that removes the optical branching coupler.