JP2611812B2 - Optical splitter / combiner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical fiber loop network,
The present invention relates to an optical branching / combining device called an optical accessor having a passing function for securing an input / output of an optical signal between a terminal device and a trunk optical fiber cable and a trunk loop.

(Prior Art) Conventionally, this type of optical accessor has a configuration as shown in FIG. In the figure, 41 and 42 are beam splitters, 43 and 44 are interference films, 45 to 50 are optical fibers, 51 to 56 are rod lenses, 57 is an optical fiber fusion spot, and 58 to 61.
Is an optical path.

FIG. 4 is a schematic diagram illustrating the configuration of the optical fiber loop network and the optical input / output unit of the terminal device. In the figure, 71 is a trunk optical fiber, 72 is a terminal device, 73 is an optical accessor, 74 to 78 are optical transmission lines provided in the optical accessor 73, 79
Is the transmission direction of the transmitted optical signal, and 80 (80a, 80b, 80
c) is a terminal device.

Optical fiber loop network, trunk optical fiber
Communication is performed by transmitting and receiving an optical signal transmitted through the terminal 71 between the terminal device 72 and the terminal device 80.

The optical signal passing through the dry-wire optical fiber 71 reaches the optical fiber 74 and is split into two.
Input to 72 (branch). The light that has traveled to the optical fiber 75 travels to the optical fiber 76 and is then transmitted (passed) to the trunk optical fiber 71.

By providing the optical coupling component with the passing function in this way, even if the terminal device 72 fails, the trunk optical fiber 71 always forms a loop, so that communication between the other terminal devices 80 is possible. Become.

The light output from the terminal device 72 to the optical fiber 78 is coupled to the optical fiber 76 of the optical accessor 73 and transmitted to the trunk optical fiber 71 (coupling).

The function and configuration of the optical accessor used here were as follows.

The light emitted from the optical fiber 45 is converted into parallel light by the rod lens 51, and is half-reflected by the interference film 43 of the beam splitter 41. The reflected light passes through the optical path 58 and the rod lens 52
After being condensed by the optical fiber 46, the light enters the optical fiber 46 (branch).

On the other hand, the light transmitted through the interference film 43 passes through the optical path 59, is condensed by the rod lens 53, enters the optical fiber 47, and is further connected to the optical fiber 47 at the fusion spot 57.
It is incident on 48. The light emitted from the optical fiber 48 is converted into parallel light by the rod lens 54, and after passing through the interference film 44,
The light is focused by the rod lens 55 through the optical path 60 and
It is incident on 49 (pass).

On the other hand, the light incident from the optical fiber 50 is
Is converted into parallel light by the optical path 61, and travels along the optical path 61.
After about half of the light is reflected by the interference film 44, the light condensed by the rod lens 55 through the optical path 60 enters the optical fiber 49 (coupling).

With the above operation, three functions of branching, passing, and coupling are realized between the terminal device and the trunk optical fiber.

(Problems to be Solved by the Invention) In the above-described conventional configuration, two optical splitters are required to connect the trunk optical fiber and the terminal device. Therefore, the respective optical splitters and these are connected. Space was required for fixing the optical fiber.

In addition, since two light splitters that divide the light quantity into one-to-one light are connected and used, the light passing through the two light splitters is less than a quarter. Furthermore, since a large number of optical path components are used to construct two optical splitters, there is a disadvantage that the optical coupling components are very expensive.

SUMMARY OF THE INVENTION An object of the present invention is to solve the conventional disadvantages and to provide an optical coupling component having a small number of components and having functions of branching, coupling, and passing and having a small insertion loss.

(Means for Solving the Problems) An optical branching / combining device according to the present invention includes a pair of hexagonal prisms whose diagonals are at right angles and three pairs of parallel sides, and two sides that do not form a right angle of the hexagonal prism. The two half mirrors provided on the (face) and the two half mirrors are brought into close contact with each other,
An optical member including two right-angled triangular prisms whose outer shape combined with a hexagonal prism is quadrilateral, a pair of rod lenses sandwiching the optical member, and provided with the optical axes thereof coincident with each other, and a pair of optical fibers. And two sets of optical collimator systems. Light output from one rod lens of one of the optical collimator systems is sequentially reflected by the two half mirrors, and then one rod of the other optical collimator system. Two optical collimator systems are arranged so as to be input to a lens, and one pair of the hexagonal prisms has a diagonal of 90 degrees or more and less than 135 degrees.

(Operation) According to the above configuration, since the optical coupling component is composed of the optical collimator system and the rectangular prism, the shape can be reduced. Furthermore, since the angle of incidence of the light on the half mirror is less than 45 degrees, it is not much affected by the polarization of the light, and since the passing function unit is composed of one optical collimator, the insertion loss is reduced. Will be able to do that.

(Embodiment) An embodiment of the present invention will be described with reference to FIG. 1 and FIG.

FIG. 1 is a configuration diagram showing an optical accessor of the present invention.
In the figure, 1-4 are optical fibers, 5-8 are rod lenses, 9 is a hexagonal prism, 10 is the internal angle of the hexagonal prism, 1
1,12 are half mirrors, 13,14 are right triangle prisms, 15
Is the internal angle of the right-angled triangular prism, 16-19 are the optical paths, 20
Is a transparent resin.

Before describing the configuration and function of the optical branching / combining device, the effect of polarization on light transmittance due to the angle of incidence of light on the half mirror will be described.

FIG. 2 shows the angle of incidence of light on the half mirror and the transmittance when light is incident on the half mirror. In the figure, 21 is a half mirror (formed on a glass substrate having a refractive index of 1.5), 22 is incident light, 23 is transmitted light, 24 is reflected light,
25 is a component (S wave) in which the electric field component of the incident light 22 is parallel to the half mirror 21, 26 is a component (P wave) in which the electric field component of the incident light 22 is perpendicular to the half mirror 21, and θ is a half mirror. twenty one
Is the angle of incidence of light on R, R _S is the power transmittance of the S-wave, R _P
Is the power transmittance of the P wave.

Power transmittance for S-wave and P-wave when the incident light 22 is incident at an angle θ to the half mirror 21 in the case of S-wave, the power transmittance R _S for an incident angle of 0 degree is 4%, the angle As the power becomes larger, the power transmittance R _S also increases. On the other hand, P
If the wave, but the power transmission R _P for an incident angle of 0 degree is 4%, the power transmission R _P when near the incident angle θ is 45 degrees is extremely small (for Brewster angle exists ). Furthermore, as the angle of incidence increases, the power transmittance
R _P increases rapidly.

As described above, the power transmittances of the S wave and the P wave when the incident angle of the light of the half mirror is around 45 degrees are different. Therefore, when the half mirror is formed of a dielectric multilayer film,
It is extremely difficult to manufacture a half mirror having the same transmittance for both the S wave and the P wave with the current technology.

In FIG. 1, the internal angle 10a of the hexagonal prism 9 is 90 degrees,
The inner angle 10b is 112.5 degrees. The half mirror 11 and the half mirror 12 are provided on sides (surfaces) not in contact with a right angle.
Furthermore, a right-angled triangular prism 1 with one inner angle 15 of 22.5 degrees
The oblique sides (inclined surfaces) of 3,14 are bonded on the half mirrors 11,12 to form a square prism.

The light output from the optical fiber 1 is converted into parallel light by the rod lens 5, passes through the optical path 16, passes through the half mirror 11 having a transmittance of 40%, and the right-angled triangular prism 13, and is condensed by the rod lens 6. Input to the optical fiber 2 (branch).

On the other hand, 60% of the light reflected by the half mirror 11
After passing through the optical path 17 at 45 degrees, 60% of the light has a transmittance of 40.
Is reflected by the half mirror 12 and forms an optical path 17 and 45 degrees,
Further, the light travels along an optical path 18 parallel to the optical path 16, is condensed by the rod lens 7, and enters the optical fiber 3 (passes).

40% of the light transmitted through the half mirror 12 travels along the optical path 19,
The light leaks out of the prism 14 through the transparent silicon resin 20. As described above, since extra light is emitted to the outside of the hexagonal prism 9 and the right-angled triangular prism 14, the leakage of the optical signal is extremely small.

After the light emitted from the optical fiber 4 is converted into parallel light by the rod lens 8, 40% of the light transmitted through the half mirror 12 travels along the optical path 18, is collected by the rod lens 7, and enters the optical fiber 3. (Join).

Although the half mirror transmittance is set to 40%, the transmittance of the half mirror may not be 40% because the insertion loss can be controlled by the light transmittance of the half mirror.

(Effects of the Invention) According to the present invention, a half mirror is provided on two sides (surfaces) of a hexagonal prism in which one set of diagonals is a right angle and three sets of opposite sides are not parallel to each other. After a rectangular prism is formed by providing a right-angled triangular prism, the shape can be reduced by providing two optical collimator systems composed of two rod lenses with the rectangular prism interposed therebetween. Also, the angle of incidence of light on the half mirror is
Since it is smaller than 45 degrees, there is almost no change in reflectance due to polarized light. Furthermore, by changing the transmittance of the semi-permeable membrane used for branching / coupling, each insertion loss of branching / coupling / passing can be set freely, and the practical effect is great.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical accessor according to an embodiment of the present invention, FIG. 2 is a diagram showing the effect of polarization on transmittance when light is incident on the half mirror, and FIG. 3 is a conventional optical fiber loop. FIG. 4 is a schematic diagram showing connection between a terminal device and a main optical fiber cable in a network and input / output of an optical signal, and FIG. 4 is a configuration diagram of the optical accessor. 1-4 optical fiber, 5-8 rod lens, 9
... Hexagonal prism, 10 ... Inner angle of hexagonal prism, 11, 12, 21
…… half mirror, 13,14 …… right triangle prism, 15
…… Inner angle of right triangle prism, 16-19 …… Optical path, 20…
... Silicone resin, 22 ... Incident light, 23 ... Transmitted light, 24 ...
Reflected light, 25... S wave, 26... P wave, θ.

Claims (2)

(57) [Claims] 1. A set of hexagonal prisms whose diagonals are at right angles and three sets of opposite sides are parallel, two half mirrors provided on two sides (surfaces) of the hexagonal prism that do not form a right angle, and An optical member having two right-angled triangular prisms, which are in close contact with the two half mirrors and combined with the hexagonal prism and whose outer shape is a quadrangle, is provided with the optical member interposed therebetween with the optical axis interposed therebetween. It has a pair of rod lenses and two sets of optical collimator systems composed of a pair of optical fibers, and light output from one rod lens of the one optical collimator system is sequentially reflected by the two half mirrors. After a while
An optical splitter / combiner comprising two optical collimator systems arranged so as to be input to one rod lens of another optical collimator system. 2. A set of hexagonal prisms having a diagonal of 90 degrees or more,
The optical splitter / combiner according to claim 1, wherein the angle is less than 5 degrees.