JPH11183743A - Optical branching/connecting unit and optical transmission equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical branching/connecting unit reducing losses in a transmitting optical signal and a received optical signal and capable of efficiently supplying especially a received optical signal to an optical signal receiving part. SOLUTION: The optical branching/connecting unit has an input end face 7 opposed to an optical signal transmission part 10, an output end face 8 opposed to an optical signal receiving part 11, an I/O end face 9 connected to an optical transmission line 12, a 1st optical waveguide 2 of which one end is connected to the input end face 7, a 2nd optical waveguide 3 of which one end is connected to the output end face 8, and a common optical waveguide 4 of which one end is connected to the I/O end face 9 and other end is connected to the other ends of the 1st and 2nd optical waveguides 2, 3. The cross- sectional areas of the 1st optical waveguide 2 on respective connection parts 5 of the 1st, 2nd and common optical waveguides 2 to 4 are smaller than the cross-sectional area of the 2nd optical waveguide 3, the cross sectional area of the 2nd optical waveguide 3 is maximum on the connection part 5 and is successively reduced in the direction of the output end face 8.

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 device using the same, and more particularly to an optical splitter / coupler which is supplied from an optical transmission line during bidirectional transmission of an optical signal using the optical splitter / coupler. The present invention relates to an optical splitter / coupler capable of efficiently transmitting a received optical signal to an optical signal receiver, and an optical transmission device using the same.

[0002]

2. Description of the Related Art Hitherto, various types of optical branching couplers for transmitting an optical signal in two directions have been known. Among them, there is a synthetic resin optical branching coupler disclosed in Japanese Patent Application Laid-Open No. Hei 9-159863. Proposed.

A synthetic resin optical branching coupler proposed in Japanese Patent Application Laid-Open No. 9-159863 has an optical transmission line in which two core portions branched and coupled at one end are surrounded by a cladding portion. The first optical transmission line composed of one core portion has a tapered shape whose cross-sectional area is sequentially narrowed along the optical transmission direction, and the second optical transmission line composed of the other core portion is formed in the optical transmission direction. The optical signal emitting end face of the second optical transmission line is formed in a lens shape along a straight shape having a constant cross-sectional area.

In this synthetic resin optical branching coupler, the first optical transmission line is formed in a tapered shape, so that a light emitting element (optical signal transmitting section) for generating an optical signal and the first optical transmission line are connected. The optical coupling efficiency of the second optical transmission path can be increased, and the light signal emitting end face of the second optical transmission path is formed in a lens shape, so that the optical path between the second optical transmission path and the light receiving element (optical signal receiving unit) can be improved. Can increase the optical coupling efficiency of

[0005]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. Hei 9-159 is disclosed.
In the synthetic resin optical branching coupler proposed in No. 863, the first optical transmission line has a tapered shape whose cross-sectional area is sequentially narrowed along the optical transmission direction. When an optical signal is transmitted, the probability that the optical signal hits the tapered portion and is reflected is large, and each time the optical signal is reflected by the tapered portion, the incident angle to the interface between the core portion and the clad portion increases, and If the angle exceeds the critical angle, the optical signal is transmitted from the core to the clad without being reflected by the core, and there is a problem that the loss of the optical signal increases accordingly.

Further, in the synthetic resin optical branching coupler proposed in Japanese Patent Application Laid-Open No. 9-159863, the cross-sectional area ratio of the first and second optical transmission lines in the branch-coupled portion is approximately one.
Since it is configured to be one-to-one, not only is the rate at which the optical reception signal is transmitted to the second optical transmission line side relatively low, but also the light reception signal is transmitted after being transmitted to the second optical transmission line side. Since the rate of incidence on the element is relatively low, even if the optical signal emitting end face of the second optical transmission path is formed in a lens shape, there is a problem that the number of received optical signals supplied to the light receiving element is considerably reduced. .

That is, when the cross-sectional area ratio of the first and second optical transmission lines in the branch-coupled portion is approximately 1: 1, about 50% of the optical reception signal is transmitted to the first optical transmission line side. And
Only about 50% of the remaining optical reception signal is transmitted to the second optical transmission line side. On top of that, the optical splitter / coupler has an inherent optical signal loss in the part where it is split / coupled, and the optical signal transmitted to the second optical transmission line side also has an interface between the core part and the clad part. When the angle of incidence to the light increases and the angle of incidence exceeds the critical angle, optical signal loss occurs due to the transmission of the optical signal from the core to the cladding without being reflected by the core. The incident optical signal is 50% of the received optical signal input to the optical branching coupler.
It will be below.

In view of these points, Japanese Patent Application Laid-Open No. 9-15598
In the synthetic resin optical branching coupler proposed in No. 63, a relatively large optical signal loss occurs not only when transmitting an optical signal but also when receiving an optical signal. When used in an optical transmission device for transmitting an optical signal, there is also a problem that it can be used only for an optical transmission device with a short communication distance.

On the other hand, a single-mode waveguide (transmission optical signal transmission line) having a small cross-sectional area is coupled to a multi-mode waveguide (reception optical signal transmission line) having a large cross-sectional area to form a bidirectional optical signal transmission line. Japanese Patent Application Laid-Open No. 62-291604 proposes an optical branching coupler that transmits most of the received optical signal transmitted to the multimode waveguide (received optical signal transmission line) to reduce optical branching loss. Have been.

In the optical branching coupler proposed in Japanese Patent Application Laid-Open No. 62-291604, the cross-sectional area of the multimode waveguide (received optical signal transmission line) at the output end face remains large. It is necessary to arrange an optical signal receiving unit having a light receiving unit having a size corresponding to the cross-sectional area of the (received optical signal transmission line), and the light receiving unit of the optical signal receiving unit is connected to a multi-mode waveguide (the received optical signal transmission line). ), It is necessary to separately arrange a lens for converging the optical signal to the light receiving unit, and as a result,
There is a problem that the configuration of the optical branching coupler becomes complicated.

The present invention effectively solves these problems, and its main object is to reduce the loss to a transmission optical signal and a reception optical signal, and to efficiently receive an optical signal with a simple configuration. It is an object of the present invention to provide an optical branching coupler which can be supplied to a section.

It is another object of the present invention to provide an optical transmission apparatus capable of reducing a loss of a transmission optical signal and a reception optical signal in an optical branching coupler and extending a communicable distance. .

[0013]

In order to achieve the main object, an optical branching coupler according to the present invention comprises a first optical waveguide serving as a transmission optical signal transmission line and a second optical waveguide serving as a reception optical signal transmission line. An optical waveguide, and a common optical waveguide that becomes a transmission and reception optical signal transmission line by branching and coupling the first and second optical waveguides,
In each of the coupling portions of the first, second, and common optical waveguides, the cross-sectional area of the first optical waveguide is smaller than the cross-sectional area of the second optical waveguide;
The second optical waveguide has a first section in which the cross-sectional area is the largest at the coupling portion and gradually decreases toward the output end face.

According to another aspect of the present invention, there is provided an optical transmission apparatus according to the present invention, comprising:
An optical waveguide, a second optical waveguide serving as a reception optical signal transmission path,
A first and second optical waveguides are branched and coupled to each other, and a common optical waveguide serving as a transmission / reception optical signal transmission path is provided. In each of the first, second, and common optical waveguide coupling sections, the cross-sectional area of the first optical waveguide is 2
The cross-sectional area of the second optical waveguide is smaller than the cross-sectional area of the optical waveguide, and the cross-sectional area of the second optical waveguide is the largest at the coupling portion. A second means having a larger numerical aperture;

According to the first means, the cross-sectional area of the first optical waveguide at each coupling portion of the first, second, and common optical waveguides is made smaller than the cross-sectional area of the second optical waveguide. Since the cross-sectional area of the coupling portion is maximum and gradually decreases toward the output end face, most of the received optical signal supplied to the common optical waveguide is guided to the second optical waveguide side,
The signal can be supplied to the signal light receiving section through the output end face as it is, and the loss of the optical reception signal in the optical branching coupler can be greatly reduced with a simple configuration.

Further, according to the second means, since the optical branching coupler according to the first means is used for coupling and branching the transmission / reception optical signal, the received optical signal is transmitted to the optical branching coupler via an optical fiber. Is supplied, the loss of the received optical signal in the optical branching coupler can be greatly reduced, and as a result, the effective communication distance of the optical transmission device can be set long.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a first embodiment of the present invention, an optical branching coupler includes an input end face facing an optical signal transmitting section, an output end face facing an optical signal receiving section, and an optical transmission line. An input / output end face to be coupled, a first optical waveguide having one end coupled to the input end face, a second optical waveguide having one end coupled to the output end face, one end coupled to the input / output end face, and the other end coupled to the first input / output end face. And a common optical waveguide coupled to each other end of the second optical waveguide, wherein the cross-sectional area of the first optical waveguide at each coupling portion of the first, second, and common optical waveguides is the second optical waveguide. And the cross-sectional area of the second optical waveguide is the maximum at the coupling portion, and gradually decreases toward the output end face.

In one of the first embodiments of the present invention, the optical branching / coupling device is constituted by a core portion in which the first, second and common optical waveguides are disposed in a cladding portion, and the core portion has a refraction. Assuming that the index is n _co and the refractive index of the cladding is n _CL , for an optical signal within the wavelength range of 570 to 1550 nm,

[0019]

(Equation 1)

It satisfies the following.

In a specific example of the first embodiment of the present invention, in the optical branching coupler, the cross-sectional area of the output end face of the first optical waveguide is not more than 0.25 times the cross-sectional area of the coupling portion. The cross-sectional area of the coupling part of the two optical waveguides is 0.1 times or less the cross-sectional area of the coupling part of the common optical waveguide.

In another specific example of the first embodiment of the present invention, in the optical branching coupler, the cross-sectional area of the common optical waveguide is changed so that the input / output end face is reduced following the reduction of the cross-sectional area of the second optical waveguide. At the maximum, they become smaller in order toward the joint.

In the second embodiment of the present invention, the method for manufacturing an optical branching coupler is such that the cross-sectional area decreases in a tapered manner from one end to the other end, and the tapered shape extends from one end to a wall surface. A large-diameter cylindrical first slide pin having a small-diameter pin hole and a small-diameter cylindrical second slide pin that can be fitted into the pin hole, respectively;
A step of fitting the second slide pin into the pin hole of the first slide pin, a step of forming a clad portion around the first slide pin in which the second slide pin is fitted by injection molding, A step of pulling out the first slide pin in which the slide pin is fitted, and injecting a core material having a higher refractive index than the clad part into the middle hole part after pulling out the first and second slide pins. And a step of forming a core portion in the hole portion to manufacture the optical branching coupler.

Further, in the third embodiment of the present invention, the optical transmission device transmits at least an optical signal transmitting unit, an optical signal receiving unit, an optical fiber, and a transmission optical signal from the optical signal transmitting unit to the first optical signal transmitting unit. An optical branching coupler for transmitting an optical signal received from the optical fiber to the optical fiber via the optical waveguide and the common optical waveguide, and transmitting the received optical signal from the optical fiber to the optical signal receiving unit via the common optical waveguide and the second optical waveguide; The optical device has an input end face facing the optical signal transmitting section, an output end face facing the optical signal receiving section, and an input / output end face coupled to the optical fiber, one end of the first optical waveguide being the input end face, One end of the two optical waveguides is coupled to the output end face, one end of the common optical waveguide is coupled to the input / output end face, and the other end is coupled to the other ends of the first and second optical waveguides, respectively. Of the first optical waveguide at each coupling portion The cross-sectional area of the second optical waveguide is smaller than the cross-sectional area of the second optical waveguide, and the cross-sectional area of the second optical waveguide is maximum at the coupling portion and gradually decreases toward the output end face. Is larger than the numerical aperture.

In a specific example of the third embodiment of the present invention, the optical transmission device is such that the numerical aperture of the common optical waveguide is at least 1.5 times the numerical aperture of the optical fiber.

According to each of the first embodiments of the present invention, the cross-sectional area of the first optical waveguide is equal to that of the second optical waveguide at the coupling portion where the first, second, and common optical waveguides are coupled to each other. , And the cross-sectional area of the second optical waveguide is configured such that the coupling portion is maximum and gradually decreases toward the output end face. Most of the received optical signal supplied to the common optical waveguide via the second optical waveguide is guided to the second optical waveguide side, and then transmitted through the second optical waveguide with relatively low loss, and supplied to the optical signal receiving unit through the output end face. With a simple configuration, it is possible to greatly reduce the loss of the optical reception signal in the optical branching coupler.

According to the second embodiment of the present invention, two slide pins are used in a state where the second slide pin is fitted in the pin hole of the first slide pin, and the two slide pins are used. After injection molding of the clad portion having the pin arrangement portion as the middle hole portion, and after extracting two slide pins, the core material is injected and filled into the middle hole portion of the clad portion, and the first and second cladding portions are filled in the clad portion. 2. Since the core portion serving as the common optical waveguide is arranged and formed, an optical branching coupler having a configuration in which the first, second, and common optical waveguides are branched and coupled to each other at the coupling portion can be formed accurately and simply. It becomes possible to manufacture.

Further, according to each of the third embodiments of the present invention, the optical branching coupler obtained by the first embodiment of the present invention, that is, the optical branching coupler obtained by the first embodiment of the present invention, when performing the coupling and branching of the transmission / reception optical signal, Since the optical splitter / coupler that can greatly reduce the loss of the received optical signal is used, when the received optical signal is supplied to the optical splitter / coupler via the optical fiber,
It is possible to supply the signal light receiving unit in a state where the loss of the received optical signal transmitted through the optical branching coupler is greatly reduced,
As a result, the effective communication distance of the optical transmission device can be set longer.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B are configuration diagrams showing a first embodiment of an optical branching / coupling device according to the present invention, wherein FIG. 1A is a perspective view and FIG. 1B is a sectional view.

In FIGS. 1A and 1B, reference numeral 1 denotes an optical branching coupler, 2 denotes a first optical waveguide (core section) for transmitting a transmission optical signal, and 3 denotes a second optical waveguide (core) for transmitting a receiving optical signal. Department),
4 is a common optical waveguide for transmitting and receiving optical signals (core portion), 5 is a coupling portion where the first, second and common optical waveguides 2, 3, and 4 are mutually coupled, 6 is a cladding portion, 7 is an input end face, 8 Is an output end face, 9 is an input / output end face, 10 is a semiconductor laser element (optical signal transmitting section), 11 is a light receiving element (optical signal receiving section), 12 is an optical fiber, 12a is a core section of the optical fiber 12, 1
2b is a cladding part of the optical fiber 12.

The optical splitter / coupler 1 has a substantially rectangular parallelepiped clad portion 6 and a long cylindrical first portion formed in the clad portion 6 and having a constant longitudinal cross-sectional area.
An optical waveguide 2, a substantially conical second optical waveguide 3 in which the cross-sectional area in the length direction changes in a tapered shape, and a second optical waveguide 3 connected to the second optical waveguide 3; A common optical waveguide 4 having a substantially conical shape changing in a tapered shape, and an input end face 7 provided at an optical signal input end of the first optical waveguide 2
And an output end face 8 provided at the optical signal output end of the second optical waveguide 3 and an input / output end face 9 provided at the optical signal input / output end of the common optical waveguide 4.

In this case, in the coupling section 5, the cross-sectional area of the first optical waveguide 2 is reduced so that the cross-sectional area of the first optical waveguide 2 is smaller than the cross-sectional area of the second optical waveguide 3. The second optical waveguide 3 and the common optical waveguide 4 are configured to be 0.1 times or less the cross-sectional area of the second optical waveguide 3.
Are configured such that the cross-sectional area decreases in a tapered shape from the input / output end face 9 to the output end face 8.

The optical branching coupler 1 has a semiconductor laser element (light emitting element of an optical signal transmitting section) 10 at a position facing the input end face 7 and a light receiving element (optical signal receiving section) at a position facing the output end face 8. Of the optical fiber 12 are connected to the input / output end face 9 and the clad part 12b of the optical fiber 12 is connected to the clad part 6 on the periphery of the input / output end face 9. Has become.

In the above structure, the semiconductor laser device 1
The optical signal obtained by the light emission of 0 is input to the first optical waveguide 2 through the input end face 7 of the optical branching coupler 1 facing the optical signal, and then transmitted through the first optical waveguide 2 and the common optical waveguide 4 respectively. Is supplied to the optical fiber 12 through the input / output end face 9 and transmitted through the optical fiber 12 as a transmission optical signal. On the other hand, the received optical signal transmitted through the optical fiber 12 is transmitted through the input / output end face 9 to the common optical waveguide 4.
Is transmitted through the common optical waveguide 4 and the second optical waveguide 3 respectively, and supplied to the opposing light receiving element 11 through the output end face 8.

Next, FIGS. 2 (a) and 2 (b) correspond to FIG.
FIGS. 4A and 4B are cross-sectional views for explaining a transmission state of an optical signal in the optical branching coupler 1 according to the first embodiment shown in FIGS. 4A and 4B, wherein FIG. 4A mainly relates to the second optical waveguide 3; FIG. 2B is an explanatory diagram of a portion, and FIG. 2B is an explanatory diagram of a portion related to the first optical waveguide 2.

In FIGS. 2A and 2B, 3c is the second
The center line of the optical waveguide 3, α is the center line 3c of the second optical waveguide 3.
Is the angle between the taper surface of the second optical waveguide 3 and β
The angle formed between the tapered surface of the optical waveguide 3 and the first optical waveguide 2, l is the optical path length of the optical branching coupler 1, R is the radius of the common optical waveguide 4 at the input / output end face 9, and r is the second at the output end face 8. The radius of the optical waveguide 3, s is the radius of the first optical waveguide 2 at the input end face 7, ψ is the maximum angle of the optical signal that can propagate through the optical fiber 12 with respect to the center line 12 c of the optical fiber 12, and FIG. ) And (b) are denoted by the same reference numerals.

As shown in FIG. 2A, the second optical waveguide 3 has a tapered cross-sectional area gradually decreasing from the coupling portion 5 with the common optical waveguide 4 to the input end face 8 side. Then, by this tapered cross-sectional area reduction,
The transmission path of the received optical signal is sequentially narrowed. For this reason, the optical fiber 12 having the core portion 12a having a relatively large cross-sectional area is used.
When the light receiving element 11 having a relatively small light receiving area is used, the received optical signal can be transmitted and supplied from the optical fiber 12 to the light receiving element 11 with high efficiency.

In this case, the second optical waveguide 3 has a center line 3c.
Are arranged so as to be substantially at the same position as the center line 12 c of the optical fiber 12, and the optical signal propagating in the optical fiber 12 propagates while being totally reflected at the interface between the core 12 a and the clad 12 b of the optical fiber 12. Only an optical signal traveling at an angle equal to or less than a certain angle with respect to the center line 12 c of the optical fiber 12 can propagate through the optical fiber 12.

Now, let the numerical aperture of the optical fiber 12 be N
A _f , the refractive index of the core 12 a of the optical fiber 12 is n _cf
Assuming that the maximum angle of the optical signal that can propagate in the optical fiber 12 with respect to the center line 12c of the optical fiber 12 is ψ, the maximum angle ψ is given by the following equation (1).

[0041]

(Equation 2)

Is represented by In the equation (1), the received optical signal propagating in the optical fiber 12 at an angle within the maximum angle ψ is input to the optical branching coupler 1 and the common optical waveguide 4
3 shows conditions under which the light is totally reflected and propagated by the common optical waveguide 4 and the second optical waveguide 3 when the light propagates through the second optical waveguide 3.

In the optical branching coupler 1, the numerical aperture N
A, the first optical waveguide 2, the second optical waveguide 3 and a common waveguide 4 a refractive index of the (core portion) n _co, the refractive index of the cladding portion 6 and n _CL, the following equation (2)

[0044]

(Equation 3)

Is represented by

When the received optical signal propagating in the optical fiber 12 is input to the optical branching coupler 1 and propagates through the common optical waveguide 4 and the second optical waveguide 3, the received optical signal enters the common optical waveguide 4. The angle is represented by π− (ψ + α). Then, the numerical aperture NA _f of the optical fiber 12
If the numerical aperture NA _W of the common optical waveguide 4 of the optical branching coupler 1 is equal to that of the common optical waveguide 4, the received optical signal does not undergo total reflection in the common optical waveguide 4 and the second optical waveguide 3, and most of the received optical signal does not.
And from the second optical waveguide 3.

However, in the first embodiment, the numerical aperture NA _W of the common optical waveguide 4 of the optical branching coupler 1 is configured to be larger than the numerical aperture NA _f of the optical fiber 12. Here, when the received optical signal causes the n-th reflection at the interface between the core part and the clad part 6 constituting the common optical waveguide 4 and the second optical waveguide 3, the incident angle of the received optical signal to the interface is , Π − {+ (2n−1) α}. In order for the received optical signal to undergo total reflection at the interface, if the refractive index of the core portion of the common optical waveguide 4 and the core portion of the second optical waveguide 3 is n _CW , the following equation (3) is obtained.

[0048]

(Equation 4)

It is necessary to satisfy the following. In order for the number of reflections of the received optical signal propagating at an angle に 対 し て with respect to the center line 12c of the optical fiber 12 to be n or less at the interface, the optical path length l of the optical branching coupler 1 is expressed by the following equation (4).

[0050]

(Equation 5)

It is necessary to satisfy the following. Here, the joining surface between the optical fiber 12 and the optical branching coupler 1, that is, the input / output end 9
Is obtained, the di in the equation (4) becomes ζ = ψ + (2
i-1) α... (5), the following equation (6)

[0052]

(Equation 6)

Where yi is the following recurrence (7):
Equation (8)

[0054]

(Equation 7)

Is obtained by using At this time, the radius r of the output end face 8 of the optical branching coupler 1 is expressed by the following equation (9).

[0056]

(Equation 8)

The angle α and the optical path length l are set so that the radius r becomes as small as possible.

In the first embodiment, equations (3) and (4)
If the shapes and optical constants of the common optical waveguide 4 and the second optical waveguide 3 are selected so as to satisfy the formula, in an ideal case,
The received optical signal incident on the optical branching coupler 1 from the optical fiber 12 propagates while causing total reflection in the common optical waveguide 4 and the second optical waveguide 3, and most of the received optical signal is supplied to the light receiving element 11. Can be increased.

In the optical branching coupler 1 of the first embodiment, as the diameter of the core portion 12a of the optical fiber 12 to be coupled is larger, the degree of improvement of the optical receiving sensitivity by reducing the propagation path of the received optical signal is greater. Particularly, good results can be obtained if the core 12a is coupled to the plastic optical fiber 12 having a diameter of 0.5 to 1.0 mm.

Next, FIG. 3 is a characteristic diagram showing the relationship between the propagation path reduction ratio of the numerical aperture NA _f and the optical signal of the optical waveguide in the optical branching coupler 1 of the first embodiment.

In FIG. 3, the ordinate represents the reduction ratio of the propagation path of the optical signal, the abscissa represents the numerical aperture of the optical waveguide, and the number of reflections n of the optical signal is expressed as a parameter.

[0062] As shown in FIG. 3, the larger the numerical aperture NA _f of the optical waveguide, the propagation path reduction ratio of the optical signal increases. Further, with respect to the numerical aperture NA _f of the same optical waveguide, the more reflective the number n of the optical signal is small, the propagation path reduction ratio of the optical signal increases.

FIG. 4 is a characteristic diagram showing the relationship between the taper angle α of the optical waveguide and the reduction ratio of the optical signal propagation path in the optical branching coupler 1 of the first embodiment.

In FIG. 4, the vertical axis represents the propagation reduction ratio of the optical signal, and the horizontal axis represents the taper angle of the optical waveguide. The number of reflections n of the optical signal is expressed as a parameter.

As shown in FIG. 4, in order to obtain the same reduction ratio of the propagation path of the optical signal, the larger the number n of reflections of the optical signal,
The taper angle of the optical waveguide can be reduced. It is preferable that the taper angle is small because the manufacture of the optical branching coupler 1 is facilitated.

From the characteristics shown in FIGS. 3 and 4, the number of reflections n of the optical signal is desirably 1 to 3 times.
Preferably, the number of reflections n is two.

In FIG. 3, the number of reflections n of the optical signal is n.
Is one time, if the numerical aperture of the optical waveguide of the optical branching coupler 1 is selected to be 1.5 times or more of the numerical aperture of the core portion 12a of the optical fiber 12, the reduction ratio of the propagation path of the optical signal is set to 0.1. 5 or less, and the area ratio can be 0.25 or less. Similarly, when the number of reflections n of the optical signal is one, the optical branching coupler 1
The numerical aperture of the optical waveguide is set to the core 12a of the optical fiber 12.
It is preferable to select the numerical aperture to be 2.0 times or more of the numerical aperture of the optical signal because the area ratio of the propagation path reduction ratio of the optical signal can be 0.1 or less. If the optical fiber 12 is a plastic optical fiber having a numerical aperture of 0.3 for communication, the numerical aperture of the optical waveguide of the optical branching coupler 1 should be 0.45 or more, preferably 0.65. It is preferable to use the above.

Next, the propagation of the transmission optical signal in the first optical waveguide 2 will be described with reference to FIG.

When the transmission optical signal propagating through the first optical waveguide 2 is incident on the optical fiber 12 via the common optical waveguide 4, the transmission optical signal incident on the optical fiber 12 is transmitted to the interface between the core 12a and the cladding 12b. Is used to determine the conditions for total reflection. Here, the semiconductor laser element 1 of the transmission optical signal
If the divergence angle from 0 is Θ and NA _s = sin Θ (10), the transmission optical signal having the divergence angle Θ is
Assuming that the divergence angle at the time of incidence is θ, the following (1)
1) Formula

[0070]

(Equation 9)

The transmission optical signal is transmitted to the optical fiber 1
In order to perform total reflection at the interface 2, the following equation (12) is used.

[0072]

(Equation 10)

It is necessary to satisfy the following. Here, if the angle β is increased, the arrangement interval between the semiconductor laser element 10 and the light receiving element 11 can be increased, so that the semiconductor laser element 10 and the light receiving element 11 can be easily mounted. On the other hand, since the divergence angle θ needs to be small, the divergence angle Θ of the transmission optical signal incident on the optical branching coupler 1 in the transmission optical signal radiated from the semiconductor laser element 10 must be small. Is preferred. In this case, as the semiconductor laser element 10 suitable for use, a surface emitting semiconductor laser can be mentioned. Then, as in the case where an edge emitting semiconductor laser or a light emitting diode is used for the semiconductor laser element 10, the semiconductor laser element 1
When the spread angle 光 of the optical signal from 0 is large, a lens may be provided between the semiconductor laser element 10 and the optical branching coupler 1 so that the spread angle 光 of the optical signal is reduced. This lens may be formed on the optical branching coupler 1 side, may be formed on the semiconductor laser element 10 side, or may be provided between the semiconductor laser element 10 and the optical branching coupler 1.

In the first embodiment, by making the diameter s of the first optical waveguide 2 smaller than the diameter R of the input / output end face 9, it is possible to reduce the intensity of the received optical signal incident on the optical branching coupler 1 from the optical fiber 12. Thus, the ratio of the received optical signal that is coupled and transmitted from the coupling section 5 to the second optical waveguide 3 can be increased. In this case, since the coupling transmission ratio of the received optical signal is substantially proportional to the cross-sectional area ratio of the first optical waveguide 2 and the second optical waveguide 3, for example, the diameter of the first optical waveguide 2 is changed to the diameter of the second optical waveguide 3. If the diameter is ４, the ratio of the received optical signal propagated from the coupling portion 5 to the first optical waveguide 2 side and the received optical signal propagated to the second optical waveguide 3 side is substantially 1: 9. Become. in this way,
By making the diameter of the first optical waveguide 2 equal to or less than ４ of the diameter of the second optical waveguide 3, the loss of the received optical signal is reduced to 10% or less, and a favorable result is obtained. Further, the first optical waveguide 2
Is smaller than 1/10 of the diameter of the second optical waveguide 3, the loss of the received optical signal becomes 1% or less, and a more preferable result is obtained.

Next, FIG. 5 is a sectional view showing the configuration of a mold and a slide pin used in the method of manufacturing an optical branching coupler according to the present invention.

In FIG. 5, 13 is a mold, 14 is an injection port, 15 is a tapered slide pin, 15H is a hole, and 16 is a long cylindrical slide pin.

The mold 13 is a hollow body, and has an injection port 14 for injecting a resin at one end. The tapered slide pin 15 is provided with a hole 15H into which a part of the long cylindrical slide pin 16 can be inserted, and the tapered slide pin 15 is provided with the long cylindrical slide pin 16 on the mold 13 side. A hole that can be fitted in the inserted state is opened.

Here, a method of manufacturing the optical branching coupler 1 will be described with reference to FIG.

First, a tapered slide pin 15 and a long cylindrical slide pin 16 are inserted into the holes of the mold 13. At this time, the tapered slide pin 15
A part of the long cylindrical slide pin 16 is inserted into the hole 15H.

Next, the molten clad material (molten resin) is injected from the injection port 14 into the mold 13. After injection, mold 1
3 is cooled to solidify the clad material (molten resin).

After the clad material (molten resin) is solidified, the tapered slide pin 15 and the long cylindrical slide pin 16 are pulled out of the mold 13.

Subsequently, the solidified clad material was put into a core material injection mold (not shown), and the core material (the molten resin) was melted into a hole from which the tapered slide pin 15 and the long cylindrical slide pin 16 were pulled out. Inject). After the injection, the mold is cooled and the core material (molten resin) is solidified.

Lastly, the end face of the core material is polished or heat-treated to flatten the end face of the core material.

In the method of manufacturing the optical branching coupler 1 of the present invention, polystyrene (refractive index 1.59) is used as the core material.
Polymethylpentene (refractive index 1.4) as cladding material
6) is used.

The obtained optical branching coupler 1 has an optical wavelength of 650
In nm, the numerical aperture is 0.63.

The method of manufacturing the optical branching coupler 1 of the present invention includes, in addition to the above-described manufacturing method, manufacturing processes such as an ultraviolet curing method, a wet etching method, a reactive ion etching method, and a photopolymerization method. It is also possible to use a manufacturing process in which each part is separately manufactured and then joined.

The core material and the cladding material used in the method of manufacturing the optical branching coupler 1 according to the present invention are not limited to the above-mentioned materials, but are transparent at the wavelength of the optical signal used. If the refractive index of the material is larger than the refractive index of the cladding material, other materials, i.e., acrylic, methacrylic, carbonate, amorphous olefin, sulfone, vinyl, fluorine compounds, etc. It may be used in combination or an inorganic material such as silicon oxide.

FIG. 6 is a perspective view showing the configuration of a second embodiment of the optical branching / coupling device according to the present invention, and shows only the components of each optical waveguide.

In FIG. 6, reference numeral 17 denotes a first optical waveguide;
Is a second optical waveguide, 19 is a common optical waveguide, 20 is an input end face, 21 is an output end face, 22 is an input / output end face, and 23 is a coupling portion.

As shown in FIG. 6, the first optical waveguide 1
7, the second optical waveguide 18 and the common optical waveguide 19 have a rectangular cross section, and the first optical waveguide 17 has the same cross sectional shape as the input end face 20 as a whole.
The width and the vertical width of the common optical waveguide 19 decrease in a tapered manner from the coupling section 23 to the output end face 21. The horizontal and vertical widths of the common optical waveguide 19 also decrease from the input / output end face 22 to the coupling section 23. It is tapered. The first optical waveguide 17 has a smaller width and height than the second optical waveguide 18, and is configured and arranged to make a certain angle in the width direction with respect to the center axis of the second optical waveguide 18. , And the input / output end face 22 is joined at a position separated by a distance d. At this time,
The distance d is selected to be a length such that the transmission optical signal propagating through the first optical waveguide 17 is incident on the core portion 12a (not shown) of the optical fiber 12 having a circular shape.

The optical branching coupler according to the second embodiment is the same as that of the first embodiment.
It operates in the same manner as the optical branching coupler 1 of the embodiment,
Thereby, the same operation and effect as those of the optical branching coupler 1 of the first embodiment can be obtained, and the junction of the first optical waveguide 17 with the common optical waveguide 19 can be connected to the input / output end face 2.
2, the first optical waveguide 17 and the second optical waveguide 1 each having a rectangular cross section are selected.
Even when the common optical waveguide 8 and the common optical waveguide 19 are used, an optical signal can be efficiently coupled with the core portion 12a of the optical fiber 12 having a circular cross section. In this case, the vertical width and the horizontal width of the input / output end face 22 correspond to the core 1 of the optical fiber 12.
It may be larger than the diameter of 2a.

FIG. 7 is a perspective view showing the configuration of a third embodiment of the optical branching / coupling device according to the present invention, and shows only the components of each optical waveguide.

In FIG. 7, reference numeral 24 denotes a first optical waveguide;
Is a second optical waveguide, 26 is a common optical waveguide, 27 is an input end face, 28 is an output end face, 29 is an input / output end face, and 30 is a coupling portion.

As shown in FIG. 7, the first optical waveguide 2
4, the second optical waveguide 25 and the common optical waveguide 26 have a rectangular cross section, and the first optical waveguide 24 has the same cross sectional shape as the input end face 27 as a whole.
Is such that only the lateral width decreases in a tapered manner from the coupling section 30 to the output end face 28, and only the lateral width decreases in the tapered shape from the input / output end face 29 to the coupling section 30. Is what it is. Then, the first optical waveguide 24 and the second optical waveguide 25
Have the same vertical width and are arranged and arranged so as to form a constant angle in the horizontal width direction with respect to the central axis of the second optical waveguide 25.

The optical branching coupler of the third embodiment is also the same as that of the first embodiment.
It operates in the same manner as the optical branching coupler 1 of the embodiment,
Thereby, the same operation and effect as those of the optical branching coupler 1 of the first embodiment can be obtained. At the time of manufacturing, it is preferable to apply a manufacturing method using etching, and it is possible to manufacture a large amount at the same time. There is an advantage that can be.

FIG. 8 is a top view showing the configuration of a fourth embodiment of the optical branching / coupling device according to the present invention, showing an example in which the optical branching / coupling device is formed in a pentagonal shape. .

In FIG. 8, reference numeral 31 denotes a first optical waveguide;
Is a second optical waveguide, 33 is a common optical waveguide, 34 is an input end face, 35 is an output end face, 36 is an input / output end face, 37 is a coupling portion, and others are shown in FIGS. 1 (a) and 1 (b). The same components as those described above are denoted by the same reference numerals.

As shown in FIG. 8, the first optical waveguide 3
The first, second and common optical waveguides 32 and 33 have a circular cross section.
4, and the second optical waveguide 32 is
The cross section becomes smaller in a tapered shape from the coupling portion 37 to the output end face 35. Further, while the center line of the second optical waveguide 32 and the common optical waveguide 33 is linear, the center line of the first optical waveguide 31 is bent in an arc shape outward with respect to the second optical waveguide 32. Is what it is.

The optical branching / combining device of the fourth embodiment also operates in the same manner as the optical branching / combining device 1 of the above-described first embodiment. The same effect can be obtained, and furthermore, there is an advantage that the coupling between the input end face 34 and the semiconductor laser element 10 is facilitated.

FIG. 9 is a top view showing the structure of a fifth embodiment of the optical branching / coupling device according to the present invention, in which interference between the semiconductor laser device 10 and the light receiving device 11 is eliminated. This is an example.

In FIG. 9, reference numeral 38 denotes a first optical waveguide;
1 is a second optical waveguide, 40 is a common optical waveguide, 41 is an input end face, 42 is an output end face, 43 is an input / output end face, 44 is a coupling portion, 45 is a reflection face, and FIG.
The same components as those shown in (b) are denoted by the same reference numerals.

As shown in FIG. 9, the first optical waveguide 3
8, the second optical waveguide 39 and the common optical waveguide 40 are circular in cross section, and the first optical waveguide 38 is entirely formed on the input end face 4.
The second optical waveguide 39 has the same cross-sectional area as that of the first optical waveguide 39, and has a tapered cross section as it goes from the coupling portion 44 to the output end face 39. In addition, the center line of the second optical waveguide 39 and the common optical waveguide 40 is linear, whereas the center line of the first optical waveguide 38 is bent outward at a substantially right angle. The reflection surface 45 is formed at the bent portion.

The optical branching / combining device of the fifth embodiment operates in the same manner as the optical branching / combining device 1 of the above-described first embodiment. The same effect can be obtained, and furthermore, the coupling between the input end face 34 and the semiconductor laser element 10 is facilitated, and the interference between the semiconductor laser element 10 and the light receiving element 11 is eliminated. There is an advantage that you can.

Next, FIG. 10 is a block diagram showing a main configuration of an embodiment of an optical transmission device using any one of the optical branching couplers 1 in the first to fifth embodiments.

In FIG. 10, reference numeral 46 denotes a first optical transmission device;
47 is a second optical transmission device, 48 is a transmission medium (optical fiber), 49 is an optical communication device, 50 is a drive unit, 51 is a detection unit, 52 is a connector, 53 is a modulation unit, 54 is a demodulation unit, and others. The same components as those shown in FIGS. 1A and 1B are denoted by the same reference numerals.

The first optical transmission device 46 includes the optical branching coupler 1, the semiconductor laser device 10, and the light receiving device 11
And a driving unit 50 connected to the semiconductor laser element 10
A detection unit 51 connected to the light receiving element 11; and a connector 53 coupled between the optical branching coupler 1 and the transmission medium 48.
The second optical transmission device 47 also has the same configuration as the first optical transmission device 46. In addition, the optical communication device 4
9 is a first optical transmission device 46, a modulation unit 53, and a demodulation unit 5
4 is provided.

The first optical transmission device 46 having the above configuration is
In general, it operates as follows.

The received optical signal propagated from the second optical transmission device 47 through the transmission medium 48 enters the optical branching coupler 1 through the connector 53, and the second optical waveguide 3 (not shown) of the optical branching coupler 1 And is supplied to the light receiving element 11. The light receiving element 11 converts the incident optical signal into a corresponding electric signal, and the detecting unit 51 supplies a digital signal obtained by shaping the waveform of the electric signal to a demodulating unit 54, and the demodulating unit 54 demodulates the digital signal to obtain a data signal. The signal is extracted and supplied to a utilization circuit (not shown). On the other hand, when the data signal is supplied, the modulation unit 53 modulates the data signal, converts the data signal into a digital signal, and supplies the digital signal to the driving unit 50. The driving unit 50 drives the semiconductor laser device 10 with the digital signal. An optical signal corresponding to the digital signal is generated from the semiconductor laser device 10 and is incident on the optical branching coupler 1. Next, this optical signal propagates through the first optical waveguide 2 (not shown) of the optical branching coupler 1 and then through the connector 53 to the transmission medium 48.
And propagates through the transmission medium 48 as a transmission optical signal,
The signal is supplied to the second optical transmission device 47.

In this case, the transmission and reception timing of the optical signal between the modulation unit 53 and the demodulation unit 54 is planned, and the transmission medium 48
The collision between the transmission optical signal and the reception optical signal in the inside is avoided.

FIG. 11 is an explanatory diagram showing an example of a state of transmission and reception of various signals between the first optical transmission device 46 and the second optical transmission device 47 in the optical transmission device of the present embodiment. .

As shown in FIG. 11, when an optical signal is not transmitted and received between the first optical transmission device 46 and the second optical transmission device 47, that is, when the transmission medium 48 is open, For example, an idler signal is transmitted from the first optical transmission device 46 to the second optical transmission device 47 for a certain period of time. The second optical transmission device 47 waits for the transmission of the idler signal to end, and then transmits the idler signal from the second optical transmission device 47 to the first optical transmission device 46 for a certain period of time. Thereafter, an idler signal is transmitted again from the first optical transmission device 46 side to the second optical transmission device 47 for a certain period of time, and transmission and reception of such an idler signal are repeatedly performed. Then, while the transmission and reception of the idler signal are performed, the second optical transmission device 46 receives the second
When it becomes necessary to transmit the optical data signal to the optical transmission device 47, the first optical transmission device 46 waits until the transmission of the idler signal supplied from the second optical transmission device 47 ends,
The transmission permission signal is transmitted to the second optical transmission device 47 side. Second
Upon receiving the transmission permission signal, the optical transmission device 47 transmits a transmission permission request signal to the first optical transmission device 46 if reception is possible. When the reception of the transmission permission request signal is confirmed, the first optical transmission device 46 transmits the optical data signal to the second optical transmission device 47 side. When the transmission of the optical data signal is completed, the first optical transmission device 46 again transmits the second optical transmission signal. An idler signal indicating that the transmission medium 48 is open is transmitted to the device 47 side.

As described above, the optical transmission device of the present embodiment constantly transmits and receives the idler signal between the first optical transmission device 46 and the second optical transmission device 47 when the transmission medium 48 is open. Since the transmission is performed, it is possible to prevent a collision between the transmission optical data signal and the reception optical data signal on the transmission medium 48 beforehand. Further, by reproducing the synchronization signal by transmitting and receiving the idler signal, it becomes possible to synchronize the first optical transmission device 46 and the second optical transmission device 47.

Further, the optical transmission apparatus of the present embodiment is not limited to the above-described optical signal collision avoidance means, but also detects an optical signal collision as in the CSMA / CD system, If there is no response to the request signal, transmission of a signal or the like may be started again after waiting for a random time.

Further, when the crosstalk between the semiconductor laser element 10 and the light receiving element 11 in the optical branching coupler 1 is small, when one optical transmission apparatus is transmitting an optical signal through the transmission medium 48, The optical signal supplied from the medium 48 may be detected by the light receiving element 11.

[0115]

As described above, according to the optical branching coupler of the present invention, the sectional area of the first optical waveguide is made smaller than the sectional area of the second optical waveguide, and the sectional area of the second optical waveguide is made smaller. Since the coupling portion is configured to be sequentially smaller at the maximum in the direction of the output end face, the received optical signal supplied to the common optical waveguide via the optical transmission line is mostly guided to the second optical waveguide side,
Thereafter, the light is transmitted through the second optical waveguide with a relatively low loss and is supplied to the optical signal receiving unit through the output end face. With a simple configuration, the loss of the optical received signal in the optical branching coupler can be significantly reduced. This has the effect.

According to the method of manufacturing an optical branching coupler of the present invention, two slide pins are used in a state where the second slide pin is fitted in the pin hole of the first slide pin. After injection molding of the clad portion having the pin arrangement portion as the middle hole portion, and pulling out two slide pins, the core material is injected and filled into the middle hole portion of the clad portion, and the first, second, and Since the core portion serving as the common optical waveguide is arranged and formed, an optical branch coupler having a configuration in which the first, second, and common optical waveguides are branched and coupled to each other at the coupling portion can be manufactured accurately and easily. Has the effect of becoming

Further, according to the optical transmission apparatus of the present invention, when performing the coupling and branching of the transmission and reception optical signals, the optical branching coupler which can greatly reduce the loss of the reception optical signal of the present invention is used. When the received optical signal is supplied to the optical branching coupler via the optical branching coupler, the signal can be supplied to the signal light receiving unit with greatly reduced loss of the received optical signal transmitted through the optical branching coupler. As a result, the optical transmission There is an effect that the effective communication distance of the device can be set long.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a first embodiment of an optical branching coupler according to the present invention.

FIG. 2 is a cross-sectional view for explaining a transmission state of an optical signal in the optical branching coupler of the first embodiment.

FIG. 3 shows the numerical aperture of the optical waveguide in the optical branching coupler according to the first embodiment. FIG. 3 is a characteristic diagram showing a relationship between the optical signal propagation path reduction ratio and the optical signal.

FIG. 4 is a characteristic diagram illustrating a relationship between a taper angle of an optical waveguide and a reduction ratio of a propagation path of an optical signal in the optical branching coupler of the first embodiment.

FIG. 5 is a cross-sectional view showing a configuration of a mold and a slide pin used in the method of manufacturing an optical branching coupler according to the present invention.

FIG. 6 is a perspective view showing a configuration of a second embodiment of the optical branching coupler according to the present invention.

FIG. 7 is a perspective view showing a configuration of a third embodiment of the optical branching / coupling device according to the present invention.

FIG. 8 is a top view showing the configuration of a fourth embodiment of the optical branching / coupling device according to the present invention.

FIG. 9 is a top view showing the configuration of a fifth embodiment of the optical branching / coupling device according to the present invention.

FIG. 10 is a block diagram showing a configuration of a main part of an embodiment of an optical transmission device using an optical branching coupler of any of the first to fifth embodiments.

FIG. 11 is an explanatory diagram showing an example of a state of transmission and reception of various signals between the first optical transmission device and the second optical transmission device in the optical transmission device of the present embodiment.

[Description of Signs] 1 Optical branching coupler 2, 17, 24, 31, 38 First optical waveguide (core) 3, 18, 25, 32, 39 Second optical waveguide (core) 4, 19, 26, 33, 40 Common optical waveguide (core part) 5, 23, 30, 37, 44 Coupling part 6 Clad part 7, 20, 27, 34, 41 Input end face 8, 21, 28, 35, 42 Output end face 9, 22, 29, 36, 43 Input / output end face 10 Semiconductor laser element (optical signal transmitting section) 11 Light receiving element (optical signal receiving section) 12, 48 Optical fiber (transmission medium) 12a Core section 12b Cladding section 13 Mold 14 Injection 15 Tapered shape Slide pin 15H hole 16 long cylindrical slide pin 45 reflecting surface 46 first optical transmission device 47 second optical transmission device 48 transmission medium 49 optical communication device 50 drive unit 51 detection unit 52 Kuta 53 modulator 54 demodulator

Claims (7)

[Claims] 1. An input end face facing an optical signal transmitting section, an output end face facing an optical signal receiving section, an input / output end face coupled to an optical transmission line, and a first end coupled to the input end face. An optical waveguide, a second optical waveguide having one end coupled to the output end face, and a common optical waveguide having one end coupled to the input / output end face and the other end coupled to each other end of the first and second optical waveguides. A cross-sectional area of the first optical waveguide at each coupling portion of the first, second, and common optical waveguides is smaller than a cross-sectional area of the second optical waveguide; The optical branching coupler, wherein the cross-sectional area of the two optical waveguides is maximum at the coupling portion and gradually decreases toward the output end face. 2. The optical waveguide according to claim 1, wherein the first, second, and common optical waveguides include a core disposed in the cladding, wherein the refractive index of the core is n _co and the refractive index of the cladding is n _CL . Then, for an optical signal within the wavelength range of 570 to 1550 nm, The optical branching coupler according to claim 1, wherein 3. The first optical waveguide, wherein a cross-sectional area of the output end face is 0.25 times or less a cross-sectional area of the coupling section, and wherein the second optical waveguide has a cross-sectional area of the coupling section. 2. The optical branching / coupling device according to claim 1, wherein a size of the optical waveguide is 0.1 times or less of a cross-sectional area of the coupling portion of the common optical waveguide. 4. The common optical waveguide has a cross-sectional area having a maximum at the input / output end face following a decrease in the cross-sectional area of the second optical waveguide, and gradually decreasing toward the coupling portion. The optical branching coupler according to claim 1, wherein: 5. A large-diameter cylindrical first slide pin having a small-diameter pin hole extending from one end side to the wall surface while the cross-sectional area decreases in a taper shape from one end to the other end. A step of preparing a small-diameter cylindrical second slide pin that can be fitted into the pin hole, and fitting the second slide pin into the pin hole of the first slide pin; and forming the second slide pin into the pin hole of the first slide pin. Forming a clad portion around the one slide pin by injection molding; pulling out the first slide pin fitted with the second slide pin from the clad portion; and removing the first and second slide pins. Inject the core material with a higher refractive index than the cladding part into the middle hole part after drawing,
Forming a core portion in the middle hole portion of the clad portion; and manufacturing the optical branching coupler through: 6. transmitting at least an optical signal transmitting unit, an optical signal receiving unit, an optical fiber, and a transmission optical signal from the optical signal transmitting unit to the optical fiber via a first optical waveguide and a common optical waveguide; An optical splitter / coupler for transmitting a received optical signal from the optical fiber to the optical signal receiver via the common optical waveguide and the second optical waveguide, wherein the optical splitter / coupler faces the optical signal transmitter. Input end face
An output end face facing the optical signal receiving portion, and an input / output end face coupled to the optical fiber, one end of the first optical waveguide being the input end face, and one end of the second optical waveguide being the output end face. And one end of the common optical waveguide is coupled to the input / output end face, and the other end is coupled to the other end of each of the first and second optical waveguides. The cross-sectional area of the first optical waveguide is the second optical waveguide.
The cross-sectional area of the optical waveguide is smaller than the cross-sectional area of the second optical waveguide, and the cross-sectional area of the second optical waveguide is maximum at the coupling portion, and gradually decreases toward the output end face, and the numerical aperture of the common optical waveguide is An optical transmission device characterized by having a numerical aperture larger than an optical fiber. 7. The optical transmission device according to claim 6, wherein a numerical aperture of the common optical waveguide is at least 1.5 times a numerical aperture of the optical fiber.