KR100382162B1 - 1 by N optical switch - Google Patents

Abstract

The 1 × N optical switch according to the embodiment of the present invention includes one input port, N output ports, and first and second photorefractive plates. Among them, the input port is composed of an input optical fiber which receives the light into the optical switch and a parallel optical lens for preventing the incident light emitted from the input optical fiber from spreading to make parallel light, and the output port is parallel to the optical refraction plate. It consists of a condensing lens for condensing one transmitted light to one focal point and an output optical fiber for transmitting the condensed light condensed by the condensing lens to the outside of the optical switch. The first and second optical refraction plates each include a transparent medium plate having a refractive index of N and an antireflection film formed on the incident and transmissive surfaces of the transparent medium plate, respectively, and the rotation axes of the first and second optical refraction plates are perpendicular to each other. . By rotating the first and second optical refraction plates, the path of transmitted light is selected two-dimensionally.

Description

One by n optical switch {1 by N optical switch}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switch for use in optical communication, and more particularly, to a 1 × N optical switch capable of selectively supplying an optical signal transmitted through one optical fiber to one of N optical fibers.

Optical switch structures include directional coupling switches, Mach-Zehnder interferometer switches, and Y-shaped branch optical switches. Among them, the directional coupling switch is an element that switches the path of the optical wave by adjusting the coupling phenomenon between two adjacent optical waveguides with an external control signal. The Mach-Zehnder interferometer switch switches the path by adjusting an external signal to the relative phase difference of light waves passing through different paths. Finally, the Y-shaped branch optical switch switches the path by using the mode evolution of light waves occurring in the branch region. The mode evolutionary phenomenon refers to a phenomenon in which a local normal mode distribution changes in response to a change of structure at each point of a branched optical waveguide structure whose structure changes along the direction of propagation of light waves.

The directional coupling switch and the Mach-Zehnder interferometer switch are switched by the change of the relative phase difference of the light waves. Therefore, there is a disadvantage in that the switching characteristic is sensitive to a change in external environment such as temperature or humidity. On the other hand, the Y-shaped branch optical switch is insensitive to changes in the external environment because the switching occurs due to the mode evolution of light waves. Therefore, in most cases, it is common to adopt a Y-shaped branch optical switch as an optical switch structure. However, the method of extending the Y-shaped branch into a 1 × N optical switch by serially parallel connection has the following problems. First, as the number of outlets increases, the overall device length increases almost linearly. This increase in device length can limit the expansion of the number of outlets. Second, the number of electrodes used for switching also increases linearly. This increase in the number of electrodes complicates the overall device when expanding to 1 x N optical switches.

The technical problem to be achieved by the present invention is to provide a 1 × N optical switch of a simple structure.

1 is a configuration diagram of a 1 × N optical switch according to a first embodiment of the present invention,

2 is a perspective view of an optical refraction plate of the 1 x N optical switch according to the first embodiment of the present invention,

3a and 3b is a conceptual diagram for explaining the operating principle of the optical switch according to the present invention,

4 is a conceptual diagram showing Snell's law,

5 is a configuration diagram of a 1 × N optical switch according to a second embodiment of the present invention,

6 is a layout cross-sectional view of an output optical fiber of a 1 x N optical switch according to a second embodiment of the present invention;

7A is a graph showing reflectance according to an incident angle when light is incident on a refraction plate in air,

7B is a graph showing reflectance according to an incident angle when light is incident on the refracting plate into the air.

In order to solve this problem, the present invention adjusts the optical path by changing the rotation angle of the refracting plate.

Specifically, an input port for receiving incident light, N output ports for emitting transmitted light, disposed between the input port and the output port, rotated about a first axis, refracting the incident light, and the path is first. A first optical refraction plate which is moved in parallel in the direction, the first light refraction plate and the output port, the incident light passing through the first optical refraction plate and rotating about a second axis perpendicular to the first axis A 1 x N optical switch is provided that includes a second optical refraction plate for moving the paths in parallel in the second direction.

In this case, the first axis is a straight line passing on the incident point of the incident light and the incident light is incident on the surface of the first optical refraction plate, the second axis is the incident light transmitted through the first optical refraction plate is the second optical refraction plate It is preferably a straight line on the incident surface and passing through the incident point of the incident light. In addition, the input port may include a parallel light lens for preventing the spread of the incident light emitted from the input side optical fiber and the input side optical fiber, the parallel light lens is preferably coated with an anti-reflection film on the surface. The output port may include a condensing lens for condensing the transmitted light transmitted through the optical refraction plate and an output optical fiber for transmitting the transmitted light condensed by the condensing lens to the outside, and the condensing lens may coat an anti-reflection film on the surface thereof. It is desirable to. The photorefractive plate is preferably made by forming an antireflection film on the incident surface and the transmissive surface of the transparent medium plate, respectively. The N output ports may be two-dimensionally arranged.

Next, an optical switch according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a schematic diagram of a 1 x N optical switch according to a first embodiment of the present invention, Figure 2 is a perspective view of an optical refractive plate of the 1 x N optical switch according to a first embodiment of the present invention.

The 1 x N optical switch according to the first embodiment of the present invention includes one input port, N output ports, and an optical refractive plate. Among them, the input port consists of an input optical fiber 4 which receives the light into the optical switch and a parallel light lens 6 for preventing the incident light 1 emitted from the input optical fiber 4 from spreading to make parallel light. The output port receives the condensing lens 7 and the condensed light 3 which are agglomerated by the condensing lens 7 for condensing the parallel transmitted light 3 passing through the optical refraction plate at one focal point to the optical fiber core portion. It consists of an output optical fiber 5 for transmitting to the outside of a switch. At this time, the optical fibers 4 and 5 use a single mode or a multi mode optical fiber for transmission of an optical signal carrying information. In addition, as the parallel light lens 6, a GRIN (Gradient Refractive Index) lens or a ball lens is used to reduce the volume of the optical switch. The photorefractive plate is composed of a transparent medium plate 2 having a refractive index N and an antireflection film 8 formed on the incident and transmissive surfaces of the transparent medium plate 2, respectively. At this time, the transparent medium plate 2 is preferably parallel to the incident surface and the transmissive surface, the anti-reflection film 8 is light due to the difference in refractive index between the medium at the incident surface and the transmissive surface of the transparent medium plate (2) In order to prevent the loss due to reflection, the coating may be a single layer, but may be formed as a multilayer if necessary. In addition, an anti-reflection film (not shown) may be coated on the end surfaces of the optical fibers 4 and 5, the parallel light lens 6, and the condenser lens 7 to minimize the loss of an optical signal due to reflection.

On the other hand, the optical refraction plate is capable of rotating with a straight line lying on the incident surface of the transparent medium plate 2 as the rotation axis. At this time, the straight line serving as the rotation axis passes through the incident point of the incident light 1 incident from the input port (the center point because the incident light is parallel light) and is perpendicular to the arrangement direction of the N output ports. For example, as shown in FIG. 2, the optical refraction plate is formed by controlling the rotation axis 9 having the rotation axis as the center line on both sides of the optical refraction plate, and connecting the rotation axis 9 to an external power source (not shown). By applying a signal, it is possible to rotate the required angle. In the present invention, the output port to which the transmitted light 3 is incident is selected by adjusting the rotation angle of the optical refraction plate.

Then, the operating principle of the optical switch according to the present invention will be described.

3A and 3B are conceptual views illustrating the operating principle of the optical switch according to the present invention, and FIG. 4 is a conceptual diagram illustrating Snell's law.

First, as shown in FIG. 3A, when the incident light 1 is incident perpendicularly to the incident surface of the transparent medium plate 2 (incident along the normal of the incident surface), the light is refracted in the process of passing through the transparent medium plate 2. It doesn't work. Therefore, the transmitted light 3 travels in the same path as the incident light 1.

However, as shown in FIG. 3B, when the incident light 1 is incident at an angle of θ with respect to the normal of the incident surface, it is refracted once in the incident surface and once again in the transmission surface according to Snell's law shown in FIG. ) Is moved in parallel by Δ from the light path of the incident light 1. Here, the path change amount Δ of the transmitted light 3 is N, and the thickness t is the refractive index of the transparent medium plate 2,

It is expressed as

According to Equation 1, it can be seen that the change amount Δ of the optical path can be adjusted by changing the refractive index N, the thickness t, and the inclination angle θ of the transparent medium plate 2. However, in order to change the refractive index (N) or the thickness (t) of the transparent medium plate (2), it is cumbersome because it is necessary to replace the transparent medium plate or change the properties of the medium. Therefore, in the present invention, the refractive index N and the thickness t are fixed and the method of adjusting Δ by changing the inclined angle θ is adopted.

FIG. 5 is a configuration diagram of a 1 × N optical switch according to a second embodiment of the present invention, and FIG. 6 is a cross-sectional view of an output optical fiber of the 1 × N optical switch according to the second embodiment of the present invention.

The 1 × N optical switch according to the second embodiment of the present invention includes one input port, N output ports, and two optical refractive plates. Among them, as in the first embodiment, the input port prevents the input side optical fiber 4, which receives the light into the optical switch, and the incident light 1 emitted from the input side optical fiber 4 from spreading, thereby making parallel light. It consists of a parallel light lens (6). The individual configuration of the output port is also the same as in the first embodiment. That is, the light condensing lens 7 and the light condensed by the light condensing lens 7 for condensing the parallel transmitted light 3 passing through the optical refraction plate at one focal point to the optical fiber core portion are directed out of the optical switch. It consists of an output optical fiber 5 for transmission. In addition, antireflection films (not shown) may be coated on the end surfaces of the optical fibers 4 and 5, the parallel light lens 6, and the condenser lens 7 to minimize the loss of the optical signal due to reflection. However, unlike the first embodiment, the condenser lens 7 and the optical fiber 5 constituting the output port are arranged in a matrix form. That is, in the first embodiment, the output ports are arranged in one line on a one-dimensional straight line, but in the second embodiment, they are arranged on the two-dimensional plane. At this time, the arrangement of the output ports does not necessarily have to be a matrix shape, but may be circular or other shape. In addition, the spacing between output ports may not be constant.

The photorefractive plate consists of two first and second photorefractive plates, and the structure of each photorefractive plate is the same as in the first embodiment. That is, the antireflection films 81 and 82 are formed on the transparent medium plates 21 and 22 having the refractive index N and the incident and transmissive surfaces of the transparent medium plates 21 and 22, respectively. In this case, the transparent medium plates 21 and 22 are preferably parallel to the incident surface and the transmissive surface, and the antireflection films 81 and 82 are formed between the medium at the incident and transmissive surfaces of the transparent medium plates 21 and 22. In order to prevent the light from being lost due to the difference in refractive index, the coating may be a single layer, but may be formed as a multilayer if necessary.

Each of the optical refraction plates is capable of rotating with a straight line lying on the incident surface of the transparent medium plate 2 as the rotation axis. At this time, the straight line which becomes the rotation axis (first rotation axis) of the first optical refraction plate passes through the incident point of the incident light 1 incident from the input port (the center point because the incident light is parallel light) and in the horizontal direction (on the drawing). The straight line (the incident light 1 whose optical path is changed by the first optical refraction plate is drawn on the incidence plane of the second optical refraction plate) extending to become the rotation axis (the first rotation axis) of the second optical refraction plate is the incident light ( Passes the incident point of 1) and is perpendicular to the axis of rotation of the first optical refraction plate. As shown in FIG. 2, the 1st and 2nd optical refraction plate respectively forms the rotation axis 9 in which the 1st and 2nd rotation axis becomes a center line on both sides of the optical refraction plate, and forms this rotation axis 9, respectively. It can be rotated by the required angle by connecting to an external power source (not shown) and applying a control signal. At this time, the first light refraction plate and the second light refraction plate may be disposed at different positions.

In the second embodiment of the present invention, the output ports to which the transmitted light 3 is incident are selected by adjusting the rotation angles of the first and second optical refraction plates. At this time, the first optical refraction plate moves the optical path in the vertical direction (directions ① and ② in Figs. 5 and 6), and the second optical refraction plate moves the optical path in the horizontal direction (directions ② and ③ in Fig. 6). The optical path is moved two-dimensionally up, down, left and right. In this case, the amount of change in the optical path due to the first and second optical refraction plates can be calculated by Equation 1.

Table 1 shows a case in which light having a wavelength of 1.3 μm, which is mainly used in optical communication, enters, and a transparent medium plate having a refractive index (N) of 1.5 and a thickness (t) of 20 mm is used. An example in which the first and second optical refraction plates are rotated for the selection of each output port in the case of arrangement in a 3 x 3 matrix at intervals of 占 퐉 is illustrated. In Table 1, x represents a horizontal coordinate, y represents a vertical coordinate, and a unit is mm.

Rotation angle of the second optical refraction plate (°) Rotation angle of the second optical refraction plate (°) -2.147 0 2.147 -2.147 x = -0.25 y = -0.25 x = 0y = -0.25 x = + 0.25y = -0.25 0 x = -0.25y = 0 x = 0y = 0 x = + 0.25y = 0 2.147 x = -0.25y = + 0.25 x = 0y = + 0.25 x = + 0.25y = + 0.25

FIG. 7A is a graph showing reflectance according to an incident angle when light is incident on the refracting plate in air, and FIG. 7B is a graph showing reflectance according to an incident angle when light is incident on the refracting plate into air.

When light is incident from medium 1 to medium 2 at an angle of theta _1 with respect to the interface, the amount of reflection R (theta _1) is

r_s (theta _1) is the reflection coefficient of S wave, r_p (theta _1) is the reflection coefficient of P wave

It is expressed as

FIG. 7A illustrates a change in reflectance (R (theta _1) × 100) when theta _1 varies from 0 ° to 40 ° when n_1 is 1.0 and n_2 is 1.5. FIG. 7B shows that n_1 is 1.5 and n_2 is 1.0. In this case, the reflectance (R (theta _1) × 100) is shown when theta _1 varies from 0 ° to 40 °. As can be seen in FIGS. 7A and 7B, when the incident angle varies between 0 ° and 30 °, the reflectance does not increase significantly at about 4%. Therefore, in this range, switching is possible without a large loss of the optical signal. In addition, the optical signal loss is further reduced by forming the antireflection film.

In this embodiment, the axis of rotation is represented by a straight line lying on the surface (incident surface) of the transparent medium plate 2, which is a transparent medium having an antireflection film 8 having a thickness of several thousand angstroms to several micrometers (μm). Since the plate 2 is very thin compared to the thickness (tens of millimeters (mm)), the optical path change caused by the antireflection film 8 is ignored. However, if necessary, the rotation axis is positioned on the surface of the antireflection film 8, and the optical path change caused by the antireflection film 8 can also be considered.

According to the present invention, a 1 × N optical switch having a very simple structure can be formed using the refraction of light.

Claims (8)

An input port for receiving incident light, N output ports emitting transmitted light, A first optical refraction plate disposed between the input port and the output port and rotating about a first axis and refracting the incident light to move the path in parallel in a first direction, A path disposed between the first optical refraction plate and the output port and rotating about a second axis perpendicular to the first axis to move the incident light passing through the first optical refraction plate in a second direction in parallel; Second photorefractive plate 1 × N optical switch comprising a. In claim 1, The first axis is a straight line passing through the incident point of the incident light and the incident light is on the surface incident to the first optical refraction plate, the second axis is the incident light transmitted through the first optical refraction plate is incident to the second optical refraction plate 1 x N optical switch on the surface and a straight line passing through the incident point of the incident light. The method of claim 1 or 2, And the input port comprises a parallel light lens for preventing the spread of incident light emitted from the input optical fiber and the input optical fiber. In claim 3, The parallel optical lens is a 1 × N optical switch is coated with an anti-reflection film on the surface. The method of claim 1 or 2, And the output port includes a condensing lens for condensing transmitted light transmitted through the optical refraction plate and an output side optical fiber for transmitting the transmitted light condensed by the condensing lens to the outside. In claim 5, The condenser lens is a 1 × N optical switch is coated with an anti-reflection film on the surface. The method of claim 1 or 2, And the optical refraction plate is formed of a transparent medium plate and an antireflection film formed on the incident surface and the transmissive surface of the transparent medium plate, respectively. The method of claim 1 or 2, And the N output ports are two-dimensionally arranged.