JP2804122B2 - Optical matrix switch device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical matrix switch device for electrically controlling a transmission path of an optical signal.

(Prior Art) Conventionally, research and development of an optical matrix switch in which a waveguide and a plurality of optical switch elements (control optical switches) are provided on a substrate have been actively performed. In an optical matrix switch using a substrate exhibiting an electro-optic effect, light having a polarization axis in a direction in which the electro-optic effect is large and a polarization axis in a direction orthogonal to the polarization axis of the light and in which the electro-optic effect is small are used. It is known that light having the light is excited in the waveguide.

Light that has not been subjected to sufficient switching control by the optical switch element becomes crosstalk light, thus deteriorating the crosstalk characteristics of the optical matrix switch. In order to reduce such crosstalk light, if an optical switch element is created under such a condition that switching control can be sufficiently performed on light with a small electro-optic effect, regardless of the magnitude of the electro-optic effect, Although the light switching control can be sufficiently performed, in this case, the operating voltage of the optical switch element increases.

Accordingly, the inventors of the present application have proposed an optical matrix switch device having a configuration capable of reducing crosstalk light even when operated at a low operating voltage, as disclosed in Japanese Patent Application Laid-Open No. 1-118822. In this optical matrix switch device, for example, a directional coupler type 2
Using a × 2 optical switch, this optical switch element is made such that switching control can be performed on light having a large electro-optical effect, and the same function as passive branching can be performed on light having a small electro-optical effect. Under the conditions.

(Problems to be Solved by the Invention) However, when the 2 × 2 directional coupler type optical switch is adopted as the optical switch element, there has been a problem that the above-mentioned preparation conditions become severe.

An object of the present invention is to solve the above-mentioned conventional problems and to provide an optical matrix switch device using an optical switch element whose manufacturing conditions are more moderate.

(Means for Solving the Problems) In order to achieve this object, an optical matrix switch device according to the present invention is provided on a first substrate and is provided in a stage before two lights having deviated directions orthogonal to each other are input. An optical matrix switch, a subsequent optical matrix switch that is provided on the second substrate, and outputs two lights having deviated directions orthogonal to each other, and A polarization rotator for changing the direction of polarization of the output light from the output surface of the matrix switch to a direction different from that of the output light of the matrix switch. In an optical matrix switch device in which the control optical switch of the switch is an optical switch that selects the propagation path of the other light, the control optical switch is For light having a polarization axis in the direction in which the aero-optic effect becomes large, light switching is performed, and for light having a polarization axis in a direction in which the electro-optic effect becomes small, Y functions like a passive branch. An optical switch including a branch structure is provided.

(Operation) According to the optical matrix switch device having such a configuration, the control optical switch is an optical switch including a Y-branch structure.

The inventors of the present application use an optical switch having a Y-branch structure to perform switching control on light having a large electro-optical effect and to perform passive control on light having a small electro-optical effect. It was found that a control optical switch functioning as described above could be formed.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. It should be noted that the drawings are only schematically shown to the extent that these inventions can be understood, and therefore the dimensions, shapes, arrangement relations, and numerical conditions of the respective components are not limited to the illustrated examples.

FIG. 1 is a plan view schematically showing an entire configuration of an embodiment of the present invention.

The optical matrix switch device 8 of this embodiment is provided on a first substrate 10 and has two deflected directions orthogonal to each other.
A first-stage optical matrix switch (first-stage switch) 12 to which two lights are input, and a second-stage optical matrix switch (second-stage switch) that is provided on the second substrate 1 and outputs two lights having deviated directions orthogonal to each other. 16 and rear switch
Polarization rotating means 18 for changing the direction of deflection at the input surface of the switch 16 to a direction different from the direction of deflection at the output surface of the front-stage switch 12. And the control light switch 20 of the front switch 12
Is an optical switch that selects the propagation path of one light, the control optical switch 20 of the subsequent switch 16 is an optical switch that selects the propagation path of the other light, and the pre-stage and post-stage switches
The 12 and 16 control optical switches 20 are configured as optical switches including a Y-branch structure.

 This embodiment will be described in more detail below.

In this embodiment, the front-stage switch 12 is composed of N 1 × N-tree optical switches 22 and the rear-stage switch 16 is
It is composed of N × 1 tree type optical switches 24.

The tree type optical switch 22 has a tree-like propagation path that branches from one input port to N output ports. In order to form this propagation path, a plurality of control optical switches 20 are provided between the input and output ports of the tree type optical switch 22. Each stage is provided with any suitable number of control optical switches 20. Then, one input port and N output ports of the tree type optical switch 22 are
The connection is made via the control optical switch 20 and the waveguide 26 provided on the first substrate 10. The propagation path branches in a tree shape by connecting the output of the control optical switch 20 to the input of the control optical switch 20 in the next stage one after another. As a result, one input of the tree type optical switch 22 is input. A propagation path from the port to the N output ports is formed. First stage control optical switch
The 20 input ports are used as input ports of the tree-type optical switch 22, and the output ports of the final plurality of control optical switches 20 are used as output ports of the tree-type optical switch 22.

The tree-type optical switch 24 has a tree-like propagation path that merges from N input ports to one output port. In order to form this propagation path, a plurality of control optical switches 20 are provided between the input and output ports of the tree type optical switch 24. Each stage is provided with any suitable number of control switches 20. Then, the N input ports and one output port of the tree type optical switch 24 are connected via the control optical switch 20 of a plurality of stages and the waveguide 26 provided on the second substrate 14. The propagation paths are joined in a tree by connecting the output of the control optical switch 20 to the input of the control optical switch 20 at the next stage one after another. A propagation path to the output ports is formed. The input ports of the plurality of first-stage control optical switches 20 are used as input ports of the tree-type optical switch 24, and the last-stage control optical switch 20
Are used as the output ports of the tree type optical switch 24.

The output port of the tree-type optical switch 12 and the input port of the tree-type optical switch 16 are arbitrarily connected via a waveguide 26 so that any input port 28 to any output port 30 of the optical matrix switch device 8 can be connected. Is formed.

Further, in this embodiment, the polarization rotating means is constituted by the first substrate 10 and the second substrate 14 which are coupled so that the crystal axes in the direction in which the electro-optic effect becomes large are substantially orthogonal to each other.

As the substrates 10 and 14, substrates exhibiting an electro-optic effect, for example, ferroelectric crystallizers are used. For example, in a LiNbO ₃ substrate, the electro-optic effect becomes maximum in a direction parallel to the c-axis (optical axis) and becomes small in a direction perpendicular to the c-axis, and the c-axis in the waveguide 26 of the substrates 10 and 14. An eigenmode having a deviating direction (polarization axis direction) in a direction parallel to the above and an eigenmode having a deviating direction perpendicular to the c-axis are excited.

FIGS. 2A and 2B show the output end face 10a of the first substrate 10 and the input end face 14a of the second substrate 14 when the substrates 10, 14 are, for example, LiNbO ₃ substrates.

As shown in FIG. 2, the c-axis of the substrate 10 and the substrate surface 10b
When the angle between the c-axis of the substrate 14 and the substrate surface 14b is substantially (θ−90 °), the angle between the c-axis and the substrate surface 14b is substantially (θ−90 °). They can be combined so as to be orthogonal. The substrates 10 and 14 are joined using, for example, a resinous adhesive, and the waveguide 26 and the substrate
The fourteen waveguides 26 are optically coupled.

The angle θ ゜ can be set to any suitable value.
For example, a -Z plate can be used as 10 and a Y plate or X plate can be used as the substrate 14, for example. If θ = 45 °, substrate 10,
14 can be the same substrate, and in this case, there is an advantage that the conditions for forming the control optical switch and the waveguide can be the same in the former-stage switch 12 and the latter-stage switch 16.

Next, a configuration example of the control optical switch 20 will be described with reference to the drawings.

3 (A) to 3 (C) are diagrams showing a configuration example of a control optical switch, wherein FIG. 3 (A) is a plan view of a configuration example of the control optical switch 20, and FIGS. II in FIG.
FIG. 3 is a cross-sectional view taken along lines IB-IIIB and IIIC-IIIC.

In this example, as shown in FIG.
14 and a branch portion 32a and 32b of the Y branch 32.
And parallel waveguides 34 and 36 coupled to
The electrodes 38 and 40 provided above and the waveguide 34
And the electrode 42 provided on the substrate 10 or 14 in the waveguide outside region on the opposite side. As shown in FIGS. 3 (B) and (C), the electrodes 38, 40, 42 are formed in the parallel waveguides 34, 36 so that the intensity of the electric field E increases in the c-axis direction.
38, 40 and 42 are formed. When the control light switch 20 is driven, the electrode 40 may be grounded and a voltage of the same polarity may be applied to the electrodes 38 and 42.

FIG. 4 is a diagram schematically showing the operation characteristics of the example shown in FIG. The vertical axis of FIG. 4 indicates the output power output from one output port in the control optical switch 20 having the Y-branch structure shown in FIG. 3A, and the horizontal axis indicates the drive voltage of the control optical switch 20. A change amount ΔβL / π (Δβ indicates a propagation constant difference and L indicates an element length L) is shown. Curve in the figure,
And creating conditions L / l _c of the optical switch (the l _c indicates the coupling length, the L / l _c represents the element length standardized by coupling length l _c)
Each Characteristic curves for 2, 3, and 4 are shown.

Here, the light whose polarization axis is parallel to the c-axis and therefore exerts a large electro-optical effect is referred to as light e, and the light whose polarization axis is orthogonal to the c-axis and therefore exerts a small electro-optical effect is referred to as light o. For example, in the curve, the drive voltage of the control light switch 20 is controlled so that ΔβL / π for the light e is substantially ΔL / π for light o is almost M
_o1 vary from ~M _o2, this time, the output power of the output power is in the range of approximately 0-1 and the light o light e is almost
0.5.

Me _e1 is ΔβL / π and Me _e2 for light e when the output power of light e is 0, and ΔβL / π for light e when the output power of light e is almost 0; Me _e1 and Me _e2 In either case, the output power of the light o is approximately 0.5.
This means that the control optical switch 20 performs light switching for the light e having the polarization axis in the direction in which the electro-optic effect becomes large, and changes the light o having the polarization axis in the direction in which the electro-optic effect becomes small. On the other hand, it indicates that it can function as a passive branch.

Also in the curve 〜, the output power of the light e is 0 or 1
When .DELTA..beta.L / .pi. For light e is set so that .DELTA..beta.L / .pi. For light o, .DELTA..beta.L / .pi. For light o has a value such that control optical switch 20 functions almost equivalently to a passive branch.

From this, the creation conditions L / L for the light e are set so that the control light switch 20 can perform switching control on the light e.
Set l _c, with respect to the optical o may be appreciated that it is not necessary to consider creating condition L / l _c. Therefore, it is possible to easily create the control optical switch 20 that performs light switching for the light e and functions as a passive branch for the light o.

FIG. 5 is a plan view showing another configuration example of the control optical switch. The control optical switch 20 of this example includes a Y branch 44 provided on the substrate 10 or 14, and one and the other branch portions 44 of the Y branch 44.
a and 44b, and electrodes 46 and 44 provided on the branch portions 44a and 44b.
48, and an electrode 50 provided on the substrate 10 or 14 in the waveguide region opposite to the branch portion 44a with the branch portion 44b interposed therebetween.

As in the above-described example, the electrodes 46, 48, and 50 are connected to the branch portions 44a,
These electrodes 46, 48 and 50 are formed so that the intensity of the electric field formed in 4b increases in the c-axis direction of the substrates 10 and 14. When the control optical switch 20 is driven, the electrode 48 is grounded and the electrode
Voltages of the same polarity may be applied to 46 and 50.

In this example, the branch portions 44a and 44b are formed so as to gradually move away from the electrode start end position A to the electrode end position B. For example, the coupling coefficients of these portions 44a and 44b at the electrode start position S are determined by the electrode end. It is formed so as to be approximately 100 times the coupling coefficient at the position E.

FIG. 6 is a diagram schematically showing operating characteristics of the example shown in FIG. The vertical axis in FIG. 6 shows the output power of light output from one output port in the control optical switch 20 having the Y-branch structure shown in FIG. 5, and the horizontal axis shows ΔβL / π. Curve ,, and is in the figure, the coupling coefficient of the electrode start position S of the branch portions 44a and 44b is approximately 100 times the coupling coefficient at the electrode end position E, the manufacturing conditions L / l _c of the optical switch respectively 1 Characteristic curves for 2, 3, and 4 are shown.

6, the range of ΔβL / π of the light e at which the output power of the light e becomes almost zero is almost _{Me e11} (=
−1.3) to _{Me 12} (= −2), and the range of ΔβL / π of the light o at this time is substantially in the range of _{Mo 11 to Mo 12.}
Has a value near 0.5. The range of ΔβL / π of the light e at which the output power of the light e becomes substantially 1 is substantially M
_In this _case, the range of ΔβL / π of the light o is approximately in the range of _{Mo 21 to Mo 22} , and the output power of the light o is approximately 0.5. Therefore, in this example, similarly to the above-described example, the control optical switch 20 that performs light switching for light e and functions similarly to passive branching for light o can be easily formed.

Moreover, in this example, the branch portions 32a and 32b are gradually moved away from the start position A to the end position B, so that the output power of the light e is almost 0 or 1, as can be understood from FIG. The value of ΔβL / π of light e is in the range _{Me 11} to
It has a width of _Me12 or _{Me21 to Me22} , and therefore has the advantage that it is not necessary to control the drive voltage with higher accuracy than in the case of the above example.

When increasing or decreasing ΔβL / π of light e, ΔβL / π of light o
The change amount of π is almost 1/3 to 1/2 of the change amount of ΔβL / π of the light e, and is small, but the ΔβL / π of the light o also increases and decreases, thereby improving the loss of the optical matrix switch device 8. it can.
For example, in the example of FIG. 3 described above, a loss of 3 · log ₂ (number of ports) occurs, but in the example of FIG. 5, 2 · log ₂ (number of ports).
Only 1.5-log ₂ (number of ports) dB loss is required.

Next, the operation of the optical matrix switch device 8 having the above configuration will be briefly described. When one and the other lights whose polarization axes are orthogonal to each other are input to the pre-stage switch 12, if one light is input to the pre-stage switch 12 in the state of the light e, the one light passes through the pre-stage switch 12 to the light e. State and the rear switch 16 propagate in the state of light o, and the other light propagates in the front switch 12 in the state of light o and in the rear switch 16 in the state of light e.

When one and the other lights are in the state of the light e, the control light switch 20 performs switching control on these lights, inputs the light from the selected input port, and outputs the light from the selected output port. Further, the control light switch 20 functions in the state of light o in the same manner as a passive branch for these lights. Therefore, when one and the other lights are in the state of the light e, the switching control of these lights is performed, so that the one and the other lights are outputted from an arbitrary input port 28 of the optical matrix switch device 8 to an arbitrary output port 30. be able to.
In addition, since the switching control is performed in the state of light e, the operating voltage can be reduced.

Further, since one of the lights is subjected to switching control by the front-stage switch 12, one of the lights is not leaked to the rear-stage switch 16 or is hardly input. Further, the other light passes through the control optical switch 20 of the pre-stage switch 12 which functions in the same manner as the passive branch with respect to the light, and is branched and input to the rear-stage switch 16. The control light switch 20 of the subsequent switch 16 emits the other light input from the unselected input port of the switch 20 to the substrate, and outputs the other light input from the selected input port of the switch 20 to the output of the switch 20. Output from port. Accordingly, it is possible to substantially eliminate one and the other light from being output from the optical matrix switch device 8 as crosstalk light.

The present invention is not limited to the above-described embodiment, and accordingly, the shapes, dimensions, arrangement positions, and numerical conditions of the components can be arbitrarily and suitably changed.

For example, in the above-described embodiment, an example in which a ferroelectric crystal substrate is used has been described. However, a substrate exhibiting an electro-optical effect made of a compound semiconductor or another material may be used.

(Effects of the Invention) As is clear from the above description, according to the optical matrix switch device of the present invention, the control optical switch can perform switching control on light having a large electro-optical effect to perform the electro-optical effect. For light in which is small, it functions in the same way as passive branching.

In addition, one of the lights propagates through the optical matrix switch in the preceding stage in a state where the polarization axis direction of the electro-optical effect is large, and the other light propagates in the optical matrix switch in the subsequent stage in the direction where the electro-optical effect is small. While the other light propagates through the optical matrix switch in the preceding stage in a direction in which the polarization axis direction becomes smaller by electro-optic effect, and the light in the latter stage has an electro-optic effect in the polarization axis direction. Propagation occurs in a state of increasing direction.

Therefore, it is only necessary to perform switching control of these one and the other lights when the polarization axis direction is large in the electro-optic effect, and any input port of the optical matrix switch device regardless of the polarization axis direction of these lights. And propagated to any output port.

Since the switching control is performed when the polarization axis direction of the one and the other light is in a state where the electro-optic effect is large, when a substrate exhibiting the electro-optic effect such as a ferroelectric crystal substrate is used as the substrate, for example, Thus, it is possible to provide a polarization-independent optical matrix switch device capable of lowering the operating voltage than that using a conventional ferroelectric crystal substrate or the like. The operating voltage is equal to or lower than the conventional operating voltage, and can be reduced to, for example, about 1/10 to 1/3 of the conventional operating voltage.

In addition, since the switching control is performed when the polarization axis direction of the one and the other light is in a state where the electro-optic effect is large, when a substrate exhibiting the electro-optic effect such as a compound semiconductor substrate is used as the substrate, for example, It is possible to provide a polarization-independent optical matrix switch device capable of reducing current consumption and increasing operation speed as compared with a conventional device using a compound semiconductor substrate or the like.

In addition, since the control optical switch is an optical switch having a Y-branch structure, switching control is performed on one and the other light when the polarization axis direction has a large electro-optic effect, and the polarization axis direction is electro-optic. When the effect is small, a control optical switch that functions in the same manner as a passive branch can be created under milder conditions than before.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing a configuration of an embodiment of the present invention, and FIGS. 2A and 2B are schematic views showing an output end face of a first substrate and an input end face of a second substrate. FIG. 3 (A) is a plan view schematically showing a configuration example of a control optical switch, and FIGS. 3 (B) and (C) show control optical switches on a first substrate and a second substrate. FIG. 4 is a cross-sectional view schematically showing a state in which the optical switch is provided, FIG. 4 is a view schematically showing operating characteristics of an example of the control optical switch shown in FIG. 3, and FIG. 5 is another configuration example of the control optical switch. FIG. 6 is a schematic plan view, and FIG. 6 is a diagram schematically showing operating characteristics of the example of the control optical switch shown in FIG. 10 First substrate 12 First optical matrix switch 14 Second substrate 16 Second optical matrix switch 18 Polarization rotating means, 20 Control optical switch 22, 24 Tree type Light switch.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-118820 (JP, A) JP-A-1-118822 (JP, A) JP-A-1-114830 (JP, A) JP-A-1-118820 113734 (JP, A) JP-A-2-135426 (JP, A) JP-A-2-114242 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/00-1 / 035 G02F 1/29-1/313 G02B 6/12-6/14

Claims (3)

(57) [Claims] A first optical matrix switch provided on a first substrate to which two lights having deviated directions orthogonal to each other are input; a second optical matrix switch provided on a second substrate and having deviated directions orthogonal to each other; A rear-stage optical matrix switch from which two lights are output; and a polarization rotating unit for changing a bias direction on an input surface of the rear-stage optical matrix switch to a direction different from a bias direction on an output surface of the front-stage optical matrix switch. An optical switch that selects the propagation path of one light as the control optical switch of the preceding optical matrix switch, and an optical switch that selects the propagation path of the other light as the control optical switch of the latter optical matrix switch. In the optical matrix switch device described above, the control optical switch is configured to emit light with respect to light having a polarization axis in a direction in which the electro-optical effect is large. Performs switching,
An optical matrix switch device comprising an optical switch including a Y-branch structure that functions similarly to a passive branch for light having a polarization axis in a direction in which the electro-optic effect becomes small. 2. The optical matrix switch of the preceding stage is composed of N 1 × N-tree optical switches, and the optical matrix switch of the subsequent stage is composed of N N × 1 tree-type optical switches. The optical matrix switch device according to claim 1, wherein the optical matrix switch device is configured. 3. The apparatus according to claim 1, wherein said polarization rotating means comprises said first substrate and said second substrate which are coupled such that crystal axes in a direction in which an electro-optic effect becomes large are orthogonal to each other. 3. The optical matrix switch device according to 1 or 2.