JP2001235691A - Optical switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical switch is capable of always efficiently switching routes of light by suppressing the occurrence of insertion loss and reflected return light regardless of a change in an environmental temperature. SOLUTION: Photoconductive cores 41 and 44 of the optical switch are previously offset by as much as an offset quantity Δy calculated by Δy=z.tan(sin-1(c1 sinθ)-θ) when the refractive indices of these cores are defined as c1, the refractive index of air as c0, the polishing angle of an optical fiber end face as θand the distance between the input core 41 and the output core 44 as (z).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an optical communication system,
The present invention relates to an optical switch for switching a path of an optical signal.

[0002]

2. Description of the Related Art In order to switch the propagation path of an optical signal transmitted by a light guide medium such as an optical fiber, an optical waveguide, and a light guide core, an optical switch as disclosed in Japanese Patent Application Laid-Open No. 06-10998 is known. It is known to use

In the optical switch described in Japanese Patent Application Laid-Open No. 06-10998, an end face of one movable optical fiber and each end face of a plurality of fixed optical fibers are arranged to face each other, and the axis of the movable optical fiber is set to a plurality of axes. In order to align the movable optical fiber with the axis of a desired one of the fixed optical fibers, the movable optical fiber is biased in a direction perpendicular to the axis. In this optical switch, the end face of the movable optical fiber and the end face of the fixed optical fiber are parallel to each other, and are inclined with respect to the optical axis (axis). Also, the light emitted from the end face of the optical fiber is refracted by the difference in refractive index (difference between the refractive index of the core of the optical fiber and the refractive index of air), deviates from the optical axis, and the light emitted from the movable optical fiber is fixed light. Filling the gap between the end faces of the optical fiber with a liquid having a refractive index close to the refractive index of the core of the optical fiber (hereinafter referred to as a refractive index matching agent) to prevent the fiber from entering the fiber efficiently are doing.

[0004]

In the above-mentioned conventional optical switch, the use of a refractive index matching agent is indispensable. However, the refractive index of the refractive index matching agent changes with the environmental temperature.
There is a problem that insertion loss and reflected return light increase. Furthermore, at low temperatures, the viscosity of the refractive index matching agent increases, so that the time required for switching the optical switch becomes longer or the switching becomes difficult.

The present invention provides an optical switch that operates normally irrespective of a change in environmental temperature, suppresses the occurrence of insertion loss and reflected return light, and can always efficiently switch the optical path. That is the task.

[0006]

The above object is achieved by the following means.

That is, a plurality of light guide media are arranged on substantially the same plane with an interval on both sides such that their end faces face each other, and one of the light guide media is substantially aligned with the optical axis of the light guide medium. In an optical switch for selectively switching a light guide medium that propagates light by moving the light guide medium in a first direction at a right angle, end faces of a plurality of light guide media are made parallel to each other, and the optical axis of the light guide medium and the second A predetermined angle with respect to a second direction perpendicular to the first direction, the difference between the refractive index of the plurality of light guide media and the refractive index of the environment in which the light guide medium is placed, and the predetermined angle And the optical axis of the light guide medium on one side and the optical axis of the light guide medium on the other side are shifted in the second direction by an amount corresponding to the distance.

The light emitted from the end face of the light guide medium on one side is refracted by the difference between the refractive index of the medium and the refractive index of the environment in which the medium is placed, and travels away from the optical axis. In the above optical switch of the present invention, the light guide medium on the other side for receiving light is placed in advance in a position where the refracted light just enters the end face in consideration of such refraction. Therefore, there is no need to arrange a refractive index matching agent for preventing light from being refracted, which is indispensable in the conventional optical switch, between the end faces of the light guide medium. Therefore, loss and reflection do not increase due to a temperature change, and can be used even at a very low temperature. It is preferable to provide a coating for reducing light reflection on the end face of the light guide medium. By doing so, the return reflected light of the optical switch can be reduced.

FIG. 1 shows a configuration of an optical switch according to an embodiment of the present invention. In the figure, 1 is an input-side optical fiber block, 2 is an input-side waveguide chip, 3 is a single-crystal silicon block, 4 is an output-side waveguide chip, 5 is a single-crystal silicon block, and 6 is a single-crystal ferrite. Block 7, an optical fiber block on the output side, 8
Is an output side optical fiber holding block, 9 and 12 are a pair of side yokes, 10 is a top yoke, 11 is a permanent magnet, 13 is a bridge yoke, 14 is a coil, 15 and 1
6 is a spacer, 17 is an input side optical fiber, 18a, 18
b is an output side optical fiber, and 19 is a base.

An optical fiber block 1 for fixing an optical fiber 17 and a waveguide chip 2 on which one light guide core is formed
Is aligned so that the optical axis of the light guide core and the optical axis of the optical fiber are aligned, and is fixedly arranged on the base 19.

An output side waveguide chip 4 having two parallel light guide cores formed thereon, and two optical fibers 18a,
The optical fiber block 7 for fixing 18b is aligned so that the two optical axes of the two light guide cores and the two optical fibers are respectively aligned, and is movably disposed on the base 19. The optical fibers 18 a and 18 b are fixed by an optical fiber holding block 8 fixed to an end of the base 19.

The output side waveguide chip 4 is moved in a direction perpendicular to the optical axis by an electromagnetic actuator composed of two side yokes 9 and 12, a top yoke 10, a permanent magnet 11, a bridge yoke 13, and a coil 14. It is movable, so that one of the axes of the optical fiber 17 on the input side and the axes of the two light guide cores of the waveguide chip 4 on the output side can be selectively switched to be aligned.

When switching by an electromagnetic actuator,
In order to precisely position the two cores of the optical waveguide chip 4, two pins having a diameter of 250 μm are used for positioning. Each of these pins has a V-groove formed by anisotropic wet etching in a single crystal silicon block 3 bonded and fixed to the upper surface of the waveguide chip 2,
The single crystal silicon block 5 bonded and fixed to the upper surface is arranged so that the cross-sectional shape formed by anisotropic wet etching is located in a trapezoidal sliding groove.

FIG. 5 illustrates the pin in more detail.
In the figure, 32a and 32b are pins, 33a and 3
3b is a sliding groove formed in the silicon block 5, 34a
And 34b are grooves formed in the silicon block 3, 30
Is a light guide core on the input side, and 31a and 31b are light guide cores on the output side. The pin 32a is moved from a groove 34a formed in the fixed block 3 to a sliding groove 33 formed in the movable block 5.
The pin 32b is arranged to extend from the groove 34b formed in the fixed block 3 to the sliding groove 33b formed in the movable block 5. Pin 32
a and 32b are adhesively secured in grooves 34a and 34b, respectively, while these pins are mounted in sliding grooves 34a and 34b.
Within each is slidable.

FIG. 6 shows a cross section of the output side of the waveguide chip 4 and the silicon block 5 as viewed from the fiber 18 side. In this figure, when the block 5 and the waveguide chip 4 are deflected rightward by the action of the electromagnetic actuator, the left surfaces of the pins 32a and 32b are aligned with the left surfaces of the sliding grooves 33a and 33b as shown by solid lines. Positioning is performed by abutting each other. When the block 5 and the waveguide chip 4 are deflected to the left by the action of the electromagnetic actuator, the right surfaces of the pins 32a and 32b abut the right surfaces of the sliding grooves 33a and 33b, respectively, as shown by the dotted lines. Is positioned.

Next, the operation of the electromagnetic actuator will be described. In FIG. 1, it is assumed that the output side waveguide chip 4 is switched in the direction indicated by the arrow A.
In this state, the magnetic flux generated by the permanent magnet 11 flows through the magnetic path of the permanent magnet 11 → bridge yoke 13 → side yoke 9 → single crystal ferrite block 6 → top yoke 10 → permanent magnet 11. It is attracted to the 9 side by magnetic force. Therefore, the chip 4 and the block 5 are held together with the ferrite block 6 at the position on the arrow A side without passing a current through the coil 14.

In order to switch the chip 4 and the block 5 to the position on the arrow B side, a current is applied to the coil 14 of the side yoke 9 in such a direction as to weaken the magnetic flux in the magnetic path.
A current is applied to a coil (not shown) of the side yoke 12 in a direction to increase the magnetic flux in another magnetic path described later. As a result, the ferrite block 6 is attracted to the side yoke 12 by magnetic force, and the chip 4 and the block 5 move to the position on the arrow B side together with the ferrite block 6. In this state,
Permanent magnet 11 → bridge yoke 13 → side yoke 12
Another magnetic path of the single crystal ferrite block 6 → the top yoke 10 → the permanent magnet 11 is formed, and the chip 4 and the block 5 are held together with the ferrite block 6 at the position on the arrow B side without passing a current through the coil.

FIG. 2 is a top view excluding the electromagnetic actuator of the optical switch of the above embodiment. The optical fiber 17 on the input side and the light guide core 30 are aligned and fixed. Two light guide cores 31a and 31b are arranged facing the end face of the light guide core. The two light guide cores are aligned with the light guide cores 30 at the respective switching positions, and can efficiently transfer light.

The output-side optical fibers 18a and 18b held by the output-side optical fiber block 5 are aligned with the light guide cores 31a and 31b, respectively. Since the interval at the tip between the light guide cores 31a and 31b is smaller than the arrangement pitch of the optical fibers 18a and 18b, the switching stroke of the optical switch is small, and can be several tens μm. In addition, by increasing the distance between the light guide cores 31a and 31b toward the fiber 18,
Connection between the core and the optical fiber becomes easy.

The length of the silicon block 3 is made slightly shorter than that of the waveguide chip 2 so that a part of the surface of the chip 2 is exposed. This prevents the adhesive protruding from the groove from flowing into the gap between the waveguide chip 2 and the waveguide chip 4 and being fixed when the pins 32a and 32b are bonded and fixed in the groove formed in the block 3. Therefore, it is a space for storing excess adhesive flowing out from the groove.

Next, with reference to FIG. 3, a description will be given of an arrangement relationship near the end faces of the input light guide core and the output light guide core in the optical switch of the above embodiment. In the figure, 40 and 4
Reference numeral 3 denotes a clad, 41 and 44 denote cores, 42 and 45 denote substrates, 46a, 46b, and 46c denote arrows indicating light propagation directions, and 47 and 48 denote obliquely polished light guide core end faces. In the drawing, light traveling in the direction of arrow 46a in the core 41 from the left side is refracted by the difference between the refractive index of the core 41 and the refractive index of air when exiting from the end face 47 into the air.
Proceed in the direction of 6b. In general, the refractive index of the core 41 is larger than the refractive index of air (approximately 1), so that light emitted from the end face is refracted upward. Accordingly, the core 44 is disposed above the core 41 to receive the light refracted upward. The offset amount between the optical axis of the core 41 and the optical axis of the core 44 is Δy, the distance between the end face 47 and the end face 48 is z, and the angle (polishing angle) between the line perpendicular to the end face and the optical axis is θ, the angle between the optical axis of the core 41 and the traveling direction of the light propagating in the air represented by the arrow 46b is φ, the refractive indexes of the cores 41 and 44 are c ₁ , and the refractive index of the air is c ₀ . Then, c ₁ · sin θ = c ₀ · sin (θ + φ) Δy = z · tan φ is established.

Assuming that c ₀ = 1, the offset amount Δy can be expressed by the following equation from these equations.

Δy = z · tan (sin ⁻¹ (c ₁ sin θ) −θ) The thickness of the cladding 40 is d1, and the thickness of the cladding 43 is d2.
If d1 is larger than d2 by the offset amount Δy, the optical axes of the cores 41 and 44 can be easily adjusted by the necessary amount Δy by positioning the surfaces of the claddings 40 and 43 on the same plane. Offset can be performed with high precision.

FIG. 4 is a front view of the optical switch according to the above-described embodiment excluding the electromagnetic actuator. The waveguide chip 2 on the input side is arranged at a position lower than the waveguide chip 4 on the output side by the above-mentioned offset amount. Base 19
The center of is thinner than both ends,
A gap is formed between the chip 4 and the optical fiber block 7 and the surface of the base 19, and the chip 4 and the block 7 can move without receiving a frictional force from the surface of the base 19 during switching.

As shown in the figure, the end face of the output side silicon block 5 and the input side of the waveguide chip 4 which faces the waveguide chip 2 has an angle with respect to a direction perpendicular to the surface of the base 19. Is polished diagonally so as to have
This is to make it possible to observe the gap between the waveguide chip 2 and the waveguide chip 4 from above when assembling the optical switch, thereby facilitating the operation of assembling the optical switch.

[0025]

According to the present invention, an optical switch that operates normally irrespective of a change in environmental temperature and can always efficiently switch the optical path without generating insertion loss and reflected return light. Is provided.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a structure of an optical switch according to an embodiment of the present invention.

FIG. 2 is a top view of the optical switch of FIG. 1 excluding an electromagnetic actuator.

FIG. 3 is a diagram illustrating an arrangement relationship between light guide core end faces on an input side and an output side of the optical switch of FIG. 1;

FIG. 4 is a front view of the optical switch of FIG. 1 excluding an electromagnetic actuator.

FIG. 5 is a diagram illustrating a configuration of a positioning pin of the optical switch of FIG. 1;

6 is a sectional view of an output side waveguide chip portion of the optical switch of FIG. 1;

[Explanation of symbols]

 1: input side optical fiber block 2: input side waveguide chip 3, 5: single crystal silicon block 4: output side waveguide chip 6: single crystal ferrite block 7: output side optical fiber block 8: output side 9 and 12: side yoke 10: top yoke 11: permanent magnet 13: bridge yoke 14: coil 15, 16: spacer 17: input side optical fiber 18a, 18b: output side optical fiber 19: base 30: Input side light guide cores 31a, 31b: Output side light guide cores 32a, 32b: Pins 40, 43: Cladding 41, 44: Cores 42, 45: Substrate

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shinichi Kajiyama 880 Sunasawa-cho, Hitachi City, Ibaraki Prefecture Inside the Takasago Plant of Hitachi Cable Co., Ltd. (72) Inventor Satoshi Hazegawa 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture No. F-term in the Opto-System Laboratory, Hitachi Cable, Ltd. (reference) 2H041 AA14 AB20 AC05 AZ03

Claims (2)

[Claims] 1. A plurality of light guide media are arranged on substantially the same plane with an interval on both sides so that their end faces face each other, and one of the light guide media is substantially aligned with the optical axis of the light guide medium. In an optical switch for selectively switching a light guide medium that propagates light by moving the light guide medium in a first direction at right angles, end faces of the plurality of light guide media are parallel to each other, and the optical axis of the light guide medium and Forming a predetermined angle with respect to a second direction perpendicular to the first direction, a difference between a refractive index of the plurality of light guide media and a refractive index of an environment in which the light guide medium is placed, and the predetermined angle; And the distance between the optical axis of the light guide medium on one side and the optical axis of the light guide medium on the other side by an amount corresponding to the second distance.
An optical switch characterized by being shifted in the direction of. 2. The optical switch according to claim 1, wherein a coating for reducing light reflection is applied to an end face of the light guide medium.