JPH0695175A - 4-port optical switch - Google Patents

Abstract

(57) [Summary] (Corrected) [Purpose] Through state, cross state, loopback state
Switchable, low insertion loss, crosstalk
We provide a semiconductor 4-port optical switch with excellent characteristics.
It [Structure] X-cross type optical switch element SW₁Input side optical port
One side WG_1a, WG_1bOther optical switch element SW
₂, SW₃Output side branch optical port one WG_2d, WG_3c
Are optically connected to each other, and the optical switch element SW
₂, SW₃Output side branch optical port other side WG_2c, WG _3d
Is the optical path changing element RM₁, RM₂Optically connected to each other via
The optical switch element SW₂, SW₃Input side light port
WG_2a, WG_3bAnd the X-crossing type optical switch element
Output side optical port WG_1C, WG_1DAre semiconductor optical amplifiers
Vessel element AM₁, AM₂, AM₃, AM_FourThrough the whole
Optical port P₁, P₂, P₃, P_FourOptically connected to 4
Port optical switch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor 4-port optical switch which is entirely composed of a semiconductor and is used in optical communication and the like.

[0002]

2. Description of the Related Art Optical switches, for example, four switches shown in FIG.
Optical port P₁~ P_Four2 inputs and 2 outputs equipped with
In an optical switch (referred to as 2 × 2), the optical path is
Red P ₁→ Optical port P₃(Hereafter, this state is a through state
Optical port P₂→ Optical port P_FourOr light
Port P₁→ Optical port P_Four, Optical port P₂→ Optical port P
₃Switch to (hereinafter, this state is called cross state)
This optical port is switched and connected to one optical port.
The number of optical ports on the other side that can be connected was only two.

In the case of such a 2 × 2 optical switch, one optical port is limited in the number of the other optical ports that can be connected by switching, and in addition to the above connection state, an incident optical port is further provided. None of them also had the function of switching from P _{1 to the} incident light port P ₂ . Therefore, in optical communication, etc., there are problems such as an increase in the number of optical switches and an increase in the size of a switch installed at a relay point, etc., when switching optical paths to realize various communication states. It was

However, recently, in the switching system of the optical communication network, especially the FAM (Fiber Access M) is used.
odule) system, optical port P ₁ → optical port P
₂ (Hereafter, this state is called loopback state) is requested to be switched. As a measure against such a problem, as shown in FIG. 14, the waveguides cross in an X shape,
By arranging four optical switches S for performing one-input / two-output operation in a grid pattern and connecting the respective optical switches with optical ports as shown in the figure, for example, for one optical port P ₁ , An optical switch has been proposed in which the number of switchable optical ports of the other party is set to _three optical ports P ₂ , P ₃ , and P ₄ (see Japanese Patent Application No. 1-137827).

However, the above-mentioned optical switch has a structure in which the connection states of the respective optical ports are not equivalent to each other.
In the loopback state of the optical port P ₁ → the optical port P ₂ and the optical port P ₃ → the optical port P ₄ , the optical path length is
It is about twice as long as in other through states or cross states. Therefore, a problem arises in that there is a difference in the connection state when the optical ports are switched and connected.

In order to solve such a problem, Japanese Patent Application No. 1-306157 proposes a 4-port optical switch as shown in FIG. 15, for example. In this optical switch, four Y-branch type optical switches S ₁ , S ₂ , S ₃ and S that perform 1-input / 2-output (hereinafter referred to as 1 × 2) operation are used.
₄ branch side optical ports p _1a , p _1b , p _2a , p _2b , p _3a ,
p _3b , p _4a and p _4b are connected to each other as shown in the figure to form a 2 × 2 optical switch A surrounded by a dotted line in the figure. On the input side and the output side of this 2 × 2 optical switch A, two 1 × 2 optical switches S ₅ and S ₆ and also S ₇ and S ₈ are arranged side by side to form two optical switch groups B. ₁ and B
₂ disposed, one of the split side optical port p _5a optical port p _1c and the light switch S ₅ of the optical switch S _1; one of the split side optical optical port p _3c and the light switch S ₆ of the optical switch S ₃ port p _6a; optical ports of the optical switch S ₂ p _2c and the optical switch S ₇
One of the split side optical port p _7a of; one of the split side optical port p _8a of the optical switch S ₄ optical ports p _4c and the optical switch S _8;
Connect the door, also other branched side optical port p _6b of the other branch side optical port p _5b and the light switch S ₆ of the optical switch S ₅
And a total reflection type optical path changing unit R ₁ to connect the optical switch S ₇
The other branch-side optical port p _7b of the optical switch S _{8 and} the other branch-side optical port p _{8b of the} optical switch S ₈ are connected by the total reflection type optical path changing unit R ₂ , and the optical port p _5c of the optical switch S ₅ is connected to the optical port p _5c. Port P
_1, optical port p _6c and the optical port P ₂ of the optical switch S _6, the optical port p _7c and optical port P ₃ of the optical switch S _7, and the optical port p _8c and optical port P ₄ of the optical switch S ₈ is connected It is structured.

In the case of the 4-port optical switch having this structure, the optical port P ₁ → optical port P ₄ or the optical port P ₂ → optical port P ₃ is in a cross state, and the optical port P ₁ → optical port P ₃
Or optical port P ₂ → optical port P _{4 in} the through state,
In each of the loopback states of the optical port P ₁ → the optical port P ₂ or the optical port P ₃ → the optical port P ₄ , the light passes through the same number of optical switches from the time it enters to the time it exits. The difference between the two connected routes can be eliminated.

However, in the above optical switch,
When the optical path is switched, it is
Therefore, the state and number of passing optical switches change. example
For example, in the through state, the light is OF in both paths.
Four optical switches (S_Five-S₁-S₂-S
₇Or S₆-S₃-S_Four-S₈), But
When this goes into a cross state, the light is OF in both paths.
Two optical switches in F state and two in ON state
Optical switch (S_Five-S₁-S_Four-S₈Or S ₆-S₃
-S₂-S₇). That is, the light that the light passes through
The total number of switches is the same as in the through state, but the above switch
Switching involves switching between fully equivalent states.
It cannot be said that

Therefore, in the case of the 4-port optical switch having the above structure, a slight difference occurs in the insertion loss and the crosstalk characteristic between the three switching states of the cross state, the through state and the loopback state. Further, although the 4-port optical switch is made of a semiconductor, in general, in a semiconductor optical waveguide type optical switch, the emitted light intensity is significantly weaker than the incident light intensity, that is, the insertion loss is significant. Is unavoidable.

In the above-mentioned 4-port optical switch,
In order to solve such a problem, the structure shown in FIG.
Optical switch has been proposed (Japanese Patent Application No. 3-5274).
(See Japanese Patent Publication No. 7). This optical switch is the optical switch shown in FIG.
A semiconductor optical amplifier C is provided in each optical path of the switch. ₁, C₂，
C₃, C_Four, C_Five, C₆It has a structure with.
Therefore, cross state, through state, loopback state
In any of the state switching states, light is emitted from the incident.
Since it always passes through the semiconductor optical amplifier in the process of irradiation,
Input loss is compensated and the power injected into the semiconductor optical amplifier is compensated.
Select the operating condition by adjusting the flow value appropriately
Then, 3 of cross state, through state, loopback state
Differences between types of states can be resolved.

[0011]

However, as shown in FIG.
The following problem also occurs in the case of the 4-port optical switch shown in. That is, first, in the case of this optical switch, at least eight optical switch elements constituting the optical switch are required, which causes a problem that the overall shape becomes large.

Further, the total reflection type optical path changing portions R ₁ and R ₂ arranged to realize the loopback state have an extremely large optical path changing angle. Therefore, in the vicinity of the optical path changing portion, the mutual distance between the waveguide that guides the light to the optical path changing portion and the waveguide through which the reflected light propagates is very short. Therefore, the light that has entered the optical path changing unit causes a coupling with the adjacent reflected light waveguide before being reflected by the optical path changing unit, and the optical waveguide for reflected light that is optically connected. It does not propagate to the optical path, and the loss due to the optical path change becomes extremely large.

When such a state is caused, even if the light whose optical path has been changed is amplified by the semiconductor optical amplifier, it cannot be actually used in optical communication. The present invention provides a 4-port optical switch that can solve the above-mentioned problems in the optical switch while suppressing the abnormal increase in loss due to optical path change, while taking advantage of the advantages of the 4-port optical switch shown in FIG. To aim.

[0014]

In order to achieve the above-mentioned object, in the present invention, a semiconductor optical switch device having two input ports and two output ports and performing one input / two output operation is provided. In a 4-port optical switch formed by integrating at least three optical switching elements including at least one X-crossing type optical switching element having two input-side optical ports and two output-side optical ports. Place the above X
One of the input side optical ports of the cross-type optical switch element or /
And one of the output side branch optical ports of the other optical switch element is optically connected to one of the output side optical ports,
The other of the output side branch optical ports of the optical switch element is optically connected to each other via an optical path changing element, and the input side optical port of the optical switch element and the output side optical port of the X-crossing type optical switch element are respectively There is provided a 4-port optical switch in which the input port and the output port are optically connected via a semiconductor optical amplifier element.

[0015]

In the four-port optical switch of the present invention, the number of integrated optical switch elements may be at least three, so that the overall shape can be miniaturized. Further, by appropriately setting the mutual arrangement relationship among the optical switch element, the optical path changing element, and the optical amplifier element as described later, the lengths of the optical paths in the through state, the cross state, and the loopback state are made to coincide with each other. It is also possible to eliminate the difference in light output in each state.

Further, in any of the crossing state, the through state, and the switching state of the loopback state, light always passes through the semiconductor optical amplifier element in the process from the incidence to the emission, so that the insertion loss is compensated. Moreover, unnecessary light components are absorbed by the non-operating semiconductor optical amplifier element, so that the crosstalk characteristic is improved. Further, the operating condition is selected by appropriately adjusting the current value to be injected into the semiconductor optical amplifier element to eliminate the difference in output intensity between the three switching states of the cross state, the through state, and the loopback state. can do.

[0017]

Examples of the invention

Example 1 FIG. 1 is a schematic plan view showing the basic configuration of a 4-port optical switch of the present invention. In the figure, in the center of the optical switch, there are two input side optical ports WG _1a and WG _1b and two output side optical ports WG _1c and WG _1d , and there is an X-crossing for one input and two output operation. The optical switch element SW ₁ is arranged.

Although one input side optical port WG _1a of this X-crossing type optical switch SW ₁ has an X-crossing type structure of a waveguide, it has one input side optical port WG _2a and two output side branching ports. The output side branching optical port WG of the optical switch element SW ₂ having the optical ports WG _2c and WG _2d and performing one-input / two-output operation
_Optically connected to _2d . In addition, the X-crossing type optical switch element S
The other input side optical port WG _1b of W ₁ is optically connected to one output side branching optical port WG _3c of the optical switch element SW ₃ which has the same structure as the optical switch SW _{2 and} has the same function.

[0019] Then, another output side branching optical port WG _3d of another output branch optical port of the optical switch SW ₂ WG _2c and the optical switch SW _3, the optical path changing element RM ₁ having, for example, reflection surface RM _1a And an optical path changing element RM ₂ having a reflecting surface RM _2a , and these optical path changing elements RM ₁ and RM
_They are optically connected to each other by forming an optical port WG _R1 connecting the _two reflecting surfaces.

Therefore, the optical switch element SW₂And light
Switch element SW₃Closed optical path (optical port WG
_2c-Optical path changing element RM₁-Optical port WG_R1− Optical path changing element
Child RM₂-Optical port WG_3d) Is formed, the optical port WG
_2cTo reflective surface RM_1aIncident light on the change angle φ (rad)
At optical port WG_3dIs being led to. Also,
Optical switch element SW₂Input side optical port WG_2aIs the whole
Input port P ₁Semiconductor optical amplifier device AM optically connected to
₁Optical switch element SW₃Input side optical port
WG_3bIs the total input port P₂Semiconductor light that is optically connected to
Amplifier element AM₂Optically connected with.

Finally, the X-crossing type optical switch SW ₁
One of the output side branch optical ports WG _1c and the other of the output side branch optical ports WG _1d are respectively a semiconductor optical amplifier element AM ₃ optically connected to the whole output port P ₃ and a whole input port P ₄ . Optically connected semiconductor optical amplifier element AM ₄
Optically connected to. Optical switch elements SW ₁ , SW ₂ ,
As shown in the plan view of FIG. 2, each of SW ₃ and SW ₄ has two optical ports intersecting in an X-shape so that input side optical ports A and B and output side branching optical ports C and D Is formed and the upper electrode 10 is loaded at the crossing portion thereof, and the upper electrode 10 is operated to perform the 1-input / 2-output operation.

Here, each of these optical ports A, B, C, D
As shown in FIG. 3 which is a sectional view taken along line III-III of FIG. 2, the lower electrode 2 is formed of a material such as AuGeNi / Au on the lower surface, and is formed of, for example, n ⁺ InP. A buffer layer 3 made of a semiconductor material such as n ⁺ InP, a lower clad layer 4, and a core layer 5 made of a semiconductor material such as n ⁻ InGaAsP are sequentially formed on a substrate 1 made of a semiconductor material. N on the core layer 5
^A ridge-shaped upper clad layer 6 made of a semiconductor material such as InP and a cap layer 7 made of a semiconductor material such as n ⁻ InGaAs are formed, and the entire upper surface thereof is covered with an insulating thin film 8.

The cross-sectional structure of the intersection is shown in FIG.
4, which is a cross-sectional view taken along line IV-IV of FIG. 4, a part of the insulating thin film 8 covering the intersection is removed in a slit shape in the optical path direction to form a window 8a. For example, Zn is diffused in the layer 6 to the interface of the core layer 5 to form a Zn diffusion region, and for example, Ti / Ti is formed on the window 8a.
The upper electrode 10 is loaded by depositing a material such as Pt / Au.

In the optical switch element SW ₂ ,
The part corresponding to the optical port B in FIG. 2 does not function as an optical port, and the part corresponding to the optical port A in the optical switch element SW ₃ does not function as an optical port. In the optical switch element shown in FIG. 2, without applying any electric signal to the upper electrode 10,
For example, when light enters from the input side optical port A, the light goes straight and goes out from the output side branching optical port D. However, when a current of a predetermined value is injected from the upper electrode 10, the refractive index of the Zn diffusion region 9 decreases and a total reflection surface appears in that portion,
Light incident on the optical port A is reflected at the intersection and is reflected on the optical port C.
The optical path is changed to and the light is emitted from there. That is, since a switching function is exhibited by the ON / OFF operation of the current to the upper electrode 10, this optical switch element performs the 1-input / 2-output operation.

Next, the optical path changing element will be described.
FIG. 5 is a schematic diagram showing the positional relationship between the optical path changing elements RM ₁ and RM ₂ , the output side branch optical ports WG _2c and WG _2d, and the optical port WG _R1 in FIG. In the figure, the optical ports WG _2c , WG _2d , and WG _R1 all have the cross-sectional structure shown in FIG.
It is as shown in.

Each of the optical path changing elements RM ₁ and RM ₂ is formed as a reflecting mirror portion having reflecting surfaces RM _1a and RM _2a . In the reflecting surface RM _1a , as shown by the phantom line in FIG. 1, the optical port WG _R1 is bent such that the optical port WG _2c and the optical port WG _R1 intersect at the intersection angle θ ₁ , and the reflecting surface RM _1a is bent. _{In 2a} , as indicated by the phantom line in FIG. 1, the optical port WG
_The optical port WG _3d is bent such that _R1 and the optical port WG _3d intersect at an intersection angle θ ₂ .

[0027] Thus, the reflecting surface imaginary crossing angle theta ₁ optical port WG _2c and the optical port WG _R1 in RM _1a, the reflecting surface of optical ports in RM _2a WG _R1 and virtual crossing angle theta ₂ of the optical ports WG _3d In both cases, the critical angle of light on these reflecting surfaces is larger than that on the other side, and the light propagating from each optical port to the reflecting surface is totally reflected on these reflecting surfaces.

These reflection mirror parts are provided at predetermined positions.
For example, it may be formed by applying a normal dry etching method and usually by engraving a recess having a depth reaching the lower cladding layer 4 in FIG. Reflective surfaces RM _1a , RM existing as interfaces between the semiconductor material and the air in the recess
_This is because the difference in refractive index becomes large in _2a . In addition,
When the crossing angle θ ₁ or θ ₂ is smaller than the critical angle of light, a suitable metal may be vapor-deposited on the reflecting surfaces RM _1a and RM _2a to increase the difference in the refractive index of light on the reflecting surfaces.

Thus, the optical switch element SW₂Output side of
Branch optical port WG_2cArrow p₁Light that has gone straight like
Is the reflection mirror section RM₁Reflective surface RM_1aWith total reflection at the arrow
Mark p ₂Like optical port WG_R1Change the optical path to
Ra part RM₂Reflective surface RM_2aWith total reflection at arrow p₃No
Sea urchin light port WG_3dThe optical path is changed to the optical switch element S
W₃Incident on the optical path changing angle φ.

By the way, the above-mentioned behavior related to the progress of light
At the optical port WG_2cThe light propagating through the
θ₁First optical port WG that virtually intersects at_2cAnd number 2
Eye light port WG_R1Reflective surface RM_1a, And
Difference angle θ₂Second optical port WG that virtually intersects at_R1When
Third optical port WG_3dReflective surface RM_2aTwice all
The light path is reflected by an angle φ with respect to the direction of travel of the first light.
Change the optical port WG _3dPropagate.

Therefore, when the light from the optical switch element SW ₂ propagates to the optical switch element SW ₃ at the optical path changing angle φ, both θ ₁ and θ ₂ described above are θ
_This means that ₁ and θ ₂ ≤ φ must be satisfied. More generally, when the optical path changing angle φ is in the range of 0 to mπ (m is a positive integer), the number of optical ports virtually intersecting on the reflecting surface is 2 to n (n is 2 or more). Large integer), the intersection angle θ _i (i = 1, 2, ... N−) at which the i-th optical port and the i + 1-th optical port virtually intersect.
In 1), all must satisfy the relationship of θ _i ≦ φ.

Next, the semiconductor optical amplifier element will be described. These semiconductor optical amplifier elements AM ₁ , AM ₂ , A
Each of M ₃ and AM ₄ has a sectional structure as shown in FIG. That is, the lower electrode 12 is formed on the lower surface of the semiconductor substrate 11 such as n ⁺ InP, and the semiconductor substrate 1
1, a lower clad layer 13 made of a semiconductor such as n ⁺ InGaAsP, an active layer 14 made of a semiconductor such as n ⁻ InGaAsP, a clad layer 15 made of a semiconductor such as p ⁺ InGaAsP, and p ⁺ InGaAs. A cap layer 16 made of a different semiconductor is sequentially stacked, and the upper surface thereof is entirely covered with an insulating thin film 17. And
A part of the insulating thin film 17 is removed in a slit shape in the optical path direction to form a window 17a, and a metal such as Zn is diffused from the window 17a to the active layer 14 to form a Zn diffusion region 18. The upper electrode 19 is formed by evaporating a metal, for example. In the method of manufacturing the semiconductor optical amplifier element, the lower clad layer to the cap layer can be entirely formed by epitaxial growth without using the diffusion as described above.

In this structure, by adjusting the composition of the active layer 14 so as to obtain a forbidden band width corresponding to the wavelength of light used, when a current of a predetermined value is injected from the upper electrode 19, the active layer 14 is activated. It is possible to amplify the light propagating in, and to strongly absorb the light when no current is injected. Now, in this 4-port optical switch, if all the optical switch elements SW ₁ , SW ₂ , and SW ₃ are turned off, the optical port P ₁ -optical amplifier element AM
₁ - optical switch SW ₂ - optical switch elements SW ₁ - optical amplifier element AM ₄ - light path of the optical port P _4, or optical port P ₂ - optical amplifier element AM ₂ - optical switch SW ₃ - optical switch elements SW ₁ - an optical amplifier device AM ₃ - optical port P ₃
One or both cross states consisting of the optical paths of

In conjunction with this operation, the optical amplifier element AM ₁
And AM ₄ or the optical amplifier elements AM ₂ and AM ₃ are operated, the insertion loss can be compensated in the above path. When one optical path is operating, the other optical path is always provided with an optical amplifier element that is not operating. Therefore, unnecessary optical components are absorbed here, and the crosstalk characteristics are remarkably increased. improves.

Next, when the optical switch element SW ₁ is turned off and the optical switch elements SW ₂ and SW ₃ are turned on, the optical port P ₁ -optical amplifier element AM ₁ -input side optical port WG _2a -optical switch element SW ₂ - output optical port WG _2c - optical path changing element RM ₁ - optical port WG _R1 - optical path changing element RM ₂ - output branch optical port WG _3d - optical switch SW ₃ - input branch optical port WG _3b - optical amplifier device AM ₂ -optical port P ₂
A loopback state consisting of the optical paths of

In conjunction with this operation, the optical amplifier element A
By operating M ₁ and AM ₂ , the insertion loss can be compensated for in the above path. When this optical path is operating, the other optical paths are provided with the optical amplifier elements AM ₃ and AM ₄ which are not operating, so that unnecessary optical components such as leaked light are generated here. It is absorbed and the crosstalk characteristic is significantly improved.

When the optical switch elements SW ₂ and SW ₃ are turned off and the optical switch element SW ₁ is turned on, the optical port P
₁ - optical amplifier device AM ₁ - optical switching element SW ₂ - the output optical port WG _2d - input optical port WG _1a - optical switch SW ₁ - output optical port WG _1c - optical amplifier device AM
₃ - optical port P ₂ of the optical path, or optical port P ₂ -
The optical amplifier device AM ₂ - input optical port WG _3b - optical switching element SW ₃ - output optical port WG _3c - input optical port WG _1b - optical switch SW ₁ - output optical port WG _1d
- an optical amplifier element AM ₄ - one or both the through state and an optical path of the optical port P ₄ is obtained.

In conjunction with this operation, the optical amplifier element AM ₁
And AM ₃ or the optical amplifier elements AM ₂ and AM ₄ are operated, the insertion loss can be compensated in the above path. When one optical path is operating, the other optical path is always provided with an optical amplifier element that is not operating. Therefore, unnecessary optical components are absorbed here, and the crosstalk characteristics are remarkably increased. improves.

As described above, the 4-port optical switch can realize any of the cross state, the through state, and the loopback state. In any case, the insertion loss can be compensated by operating the optical amplifier element of each optical path, and at that time, the non-operational optical amplifier element interposed in the other optical path. The crosstalk characteristic is improved by the action of.

Further, in any of the above-mentioned states, the length of the optical path in each state can be made equal by appropriately selecting the arrangement relation of each element, and therefore the gain of the optical amplifier element is 0 dB. Even in such a case, the light output intensities in each state can be made to match, and the difference in light output due to the change in the switching state can be eliminated.

Embodiment 2 FIG. 7 is a schematic plan view showing another 4-port optical switch. This is the same as the 4-port optical switch shown in FIG. 1, except that the X-crossing type optical switch elements SW ₂ and SW ₃ are Instead of the Y-branch optical switch elements SW ₄ and SW ₅ that perform 1-input / 2-output operation, other elements and optical ports have the same structure as that shown in FIG.

In the optical switch elements SW ₄ and SW ₅ , as shown in the plan view of FIG. 8, one input side optical port A'is Y.
It has a structure in which two output side branching optical ports B ′ and C ′ are branched to form the output side branching optical ports B ′ and C ′, and the upper electrodes 20a and 20b are respectively loaded. Further, the cross-sectional structure is shown in FIG. 9 is a sectional view taken along the line IX-IX in FIG. 8, the lower electrode 12 is formed of a material such as AuGeNi / Au on the lower surface, for example, n ⁺ InP
N ⁺ In on a substrate 11 made of a semiconductor material such as
A buffer layer 13 made of a semiconductor material such as P, n ⁺ I
a lower cladding layer 14 made of a semiconductor material such as nP,
A core layer 15 made of a semiconductor material such as n ⁻ InGaAsP is sequentially formed, and n ⁻ I is further formed on the core layer 15.
A ridge-shaped upper clad layer 16 made of a semiconductor material such as nP and a cap layer 17 made of a semiconductor material such as n ⁻ InGaAs are formed, and the entire upper surface thereof is covered with an insulating thin film 18, and a part thereof is appropriately formed. Remove by size and window 1
After forming 8a, Zn is diffused from here into the cap layer 17 and the upper cladding layer 16 to an appropriate depth to form a Zn diffusion region 19, and, for example, Ti / Pt / Au is formed on the window 18a. Electrode 20a, 2 for current injection (or voltage application) by depositing a material such as
0b is loaded respectively.

In the optical switch element shown in FIG. 8,
When light is input from the input side optical port A ′ without applying an electric signal to either of the upper electrodes 20a and 20b, light of the same output is emitted from the output side branching optical ports B ′ and C ′. Then, when the upper electrode 20b is made non-driving and a current of, for example, a predetermined value is injected only from the upper electrode 20a, the entire refractive index of the portion of the output side branching optical port B ′ located immediately below that lowers and propagates there. Since the optical mode is cut off, all the light incident from the input side optical port A ′ propagates only through the output side branching optical port C ′ and exits from there. When the upper electrode 20a is not driven and a current of a predetermined value is injected only from the upper electrode 20b, the output side branching optical port C'is in the mode cutoff state, and the light is output side branching optical port B '. Propagate only to and exit from there. That is, the upper electrodes 20a, 2
If the current injection to 0b is performed alternately, the input side optical port A '
The light incident on the optical path is alternately switched to the output-side branch optical port B ′ and the output-side branch optical port C ′ and emitted, so that the switching operation occurs.

In this 4-port optical switch, the optical switch
Switch SW₁To turn off the optical switch element SW_FourOut of
Power side branch optical port WG_4cDrive the upper electrode loaded in
The optical switch element SW_FiveOutput side branch optical port
WG_5dIf only the upper electrode loaded on the
Port P₁-Optical amplifier element AM₁-Input side optical port WG
_4a-Output side branch optical port WG_4d-Input side optical port WG_1a
-Optical switch element SW ₁-Output side branch optical port WG_1d
-Optical amplifier element AM_Four-Optical port P_FourThe light path of
Is the optical port P₂-Optical amplifier element AM₂-Input side optical port
WG_5b-Optical switch element SW_Five-Output side optical port
WG_5c-Input side optical port WG_1b-Optical switch element SW₁
-Output side branch optical port WG_1c-Optical amplifier element AM₃-Light
Port P₃One or both cross states consisting of optical paths
Is obtained.

In conjunction with this operation, the optical amplifier element AM ₁
And AM ₃ or the optical amplifier elements AM ₂ and AM ₄ are operated, the insertion loss can be compensated in the above path. When one optical path is operating, the other optical path is always provided with an optical amplifier element that is not operating. Therefore, unnecessary optical components are absorbed here, and the crosstalk characteristics are remarkably increased. improves.

Next, the optical switch element SW₁Off, light
Switch element SW_FourOutput side branch optical port WG_4dLoaded on
Drive only the upper electrode, and also the optical switching element
SW _FiveOutput side branch optical port WG_5cLoaded on
When the partial electrodes are driven, the optical port P₁-Optical amplifier element AM
₁-Input side optical port WG_4a-Optical switch element SW_Four− Out
Power side branch optical port WG_4c-Optical path changing element RM₁-Light port
WG_R1-Optical path changing element RM₂-Output side branch optical port W
G_5d-Optical switch element SW_Five-Input side optical port WG_5b
-Optical amplifier element AM₂-Optical port P₂Consisting of the light path of
A loopback state is obtained.

In conjunction with this operation, the optical amplifier element A
M₁, AM₂By operating the above optical path
Can compensate for insertion loss. And this light sutra
When the light path is working, the other light path is
Not optical amplifier element AM₃, AM _FourMust be installed
Unwanted light components are absorbed here and crosstalk
The characteristics are significantly improved.

Further, the optical switch element SW ₁ is turned on,
Only the upper electrode loaded in the output side branching optical port WG _4c of the optical switch element SW ₄ is driven, and only the upper electrode loaded in the output side branching optical port WG _5d of the optical switch element SW ₅ is driven. Then, the optical port P ₁ -optical amplifier element AM ₁ -input side optical port WG _4a -optical switch element S
W ₄ -Output side optical port WG _{4d -Input} side optical port WG
_1a -Optical switch element SW ₁ -Output side branch optical port WG _1c
- an optical amplifier device AM ₃ - optical port P ₃ of the optical path, or optical port P ₂ - optical amplifier element AM ₂ - input optical port WG _5b - optical switch SW ₅ - output branch optical port WG _5c - Input Side optical port WG _1b -Optical switch element SW ₁
- the output branch optical port WG _1d - optical amplifier element AM ₄ - one or both the through state and an optical path of the optical port P ₄ is obtained.

In conjunction with this operation, the optical amplifier element AM ₁
And AM ₃ or the optical amplifier elements AM ₂ and AM ₄ are operated, the insertion loss can be compensated in the above optical path. Then, when one optical path is operating, the optical amplifier elements AM ₂ and AM ₄ which are not operating are always provided in the other optical path, so that unnecessary optical components are absorbed here, Crosstalk characteristics are significantly improved.

As described above, also in the case of this 4-port optical switch, any of the cross state, the through state, and the loopback state can be realized. And in any case, the insertion loss can be compensated by operating the optical amplifier element of each optical path, and at that time, due to the function of the optical amplifier element interposed in the other optical path. An improvement in crosstalk characteristics is achieved.

Further, in any of the above-mentioned states, the length of the optical path in each state can be made equal by properly selecting the arrangement relationship of each element, so that the gain of the optical amplifier element is 0 dB. Even in such a case, the light output intensities in each state can be made to match, and the difference in light output due to the change in the switching state can be eliminated.

Embodiment 3 FIG. 10 shows a schematic plan view of a 4-port optical switch of another embodiment. This 4-port optical switch has a structure in which the respective elements shown in FIG. 1 are arranged symmetrically with the optical switch element SW ₁ as the center. In this 4-port optical switch, the optical switch elements SW ₁ , SW ₂ , SW ′ ₂ , S
W _3, Turning off all SW _'3, the optical port P ₁ - optical amplifier device AM ₁ - input optical port WG _2a - optical switching element SW ₂ - output branch optical port WG _2d - input optical port WG _1a - optical switch SW ₁ - output branch optical port WG _1d - input optical port WG _'3c - optical switching element S
W ′ ₃ −Output side branch optical port WG ′ _3b −Optical amplifier element AM
₄ - While cross state consisting of the light path of the optical port P _4, or optical port P ₂ - optical amplifier element AM ₂ - input optical port WG _3b - optical switching element SW ₃ - output branch optical port WG _3c - Input Side optical port WG _1b -Optical switch element SW
₁ -Output side optical port WG _1c -Input side optical port WG '
_2d -Optical switch element SW ' ₂ -Output side branch optical port WG'
_2a - optical amplifier device AM ₃ - one is cross state obtained consisting of the light path of the optical port P _3.

Next, the optical switch elements SW ₁ , SW ′ ₂ ,
When SW ′ ₃ is turned off and the optical switch elements SW ₂ and SW ₃ are turned on, the optical port P ₁ -optical amplifier element AM ₁ -input side optical port WG _2a -optical switch element SW ₂ -output side branch optical port WG _2c -Optical path changing element RM ₁ -Optical port WG _R1
- the optical path changing element RM ₂ - output branch optical port WG _3d - optical switching element SW ₃ - input optical port WG _3b - the optical amplifier element AM ₂ - loopback state consisting of optical ports P ₂ of the optical path is obtained, In addition, the optical switch elements SW ₁ , SW
₂ and SW ₃ are turned off, and the optical switch elements SW ' ₂ and SW' ₃
Is turned on, the optical port P ₃ − optical amplifier element AM ₃ −
Output side branch optical port WG ′ _2a − Optical switch element SW ′ ₂ −
Input side optical port WG ' _2c -Optical path changing element RM' ₁ -Optical port WG ' _R1 -Optical path changing element RM' ₂ -Input side optical port W
G _'3d - optical switch SW' ₃ - output branch optical port W
G _'3b - optical amplifier element AM ₄ - another loop-back state consisting of the light path of the optical port P ₄ is obtained.

Further, the optical switch element SW₁Turn on,
Optical switch element SW₂, SW₃ , SW '₂, SW '₃All of
Turn off the light port P₁-Optical amplifier element AM₁−
Input side optical port WG_2a-Optical switch element SW₂-Output side
Branch optical port WG_2d-Input side optical port WG_1a-Light switch
Chi element SW₁-Output side branch optical port WG_1c-Input side optical port
WG '_2d-Optical switch element SW '₂-Output side branch optical port
WG '_2a-Optical amplifier element AM₃-Optical port P₃Light of
Path or optical port P₂-Optical amplifier element AM₂-Enter
Power side light port WG_3b-Optical switch element SW₃-Output side
Gikou Port WG _3c-Input side optical port WG_1b-Optical switch
Element SW₁-Output side branch optical port WG_1d-Input side optical port
To WG '_3c-Optical switch element SW '₃− Output side branch optical port
To WG '_{3 b}-Optical amplifier element AM_Four-Optical port P_FourLight sutra
One or both slews of roads are obtained.

As described above, also in the case of this 4-port optical switch, any of the cross state, the through state, and the loopback state can be realized. And in any case, the insertion loss can be compensated by operating the optical amplifier element of each optical path, and at that time, due to the function of the optical amplifier element interposed in the other optical path. An improvement in crosstalk characteristics is achieved.

Further, in any of the above-mentioned states, the length of the optical path in each state can be made equal by appropriately selecting the arrangement relationship of each element, so that the gain of the optical amplifier element is 0 dB. Even in such a case, the light output intensities in each state can be made to match, and the difference in light output due to the change in the switching state can be eliminated.

[0057] Example 4 FIG. 11 is a schematic plan view showing still another embodiment, the 4-port optical switch, the 4-port optical switch shown in FIG. 10, four optical optical switch element SW ₂ port input optical ports that are not involved in the propagation of light out of the GW _2b (referred dummy light port), four input optical ports that are not involved in the propagation of out of light ports of the optical switch SW ₃ (dummy optical port The optical path changing element (reflection mirror section) RM ₃ is extended to each of the GW _3a to be optically connected, and is involved in the propagation of light among the four optical ports of the optical switch element SW ′ _2. Output side branching optical port (called dummy optical port) GW ′ _2b and output side branching optical port (called dummy optical port) GW ′ that does not participate in light propagation among the four optical ports of the optical switch element SW ′ _{3 3a,} respectively Mashimashi the light path changing element also has the (reflective mirror)
The structure is such that RM ' ₃ is optically connected.

This 4-port optical switch can switch between the through state, the cross state, and the loopback state by performing the same operation as that of the 4-port optical switch of the third embodiment (FIG. 10). In this 4-port optical switch, the optical path changing elements RM ₃ and RM ′ ₃ are newly arranged, so that crosstalk or stray light during switching operation can be effectively attenuated or guided to a position to be propagated. The ability to do it is added.

This effect will be described below. For example, in the 4-port optical switch shown in Example 3 (FIG. 10),
When the optical switches SW ₁ , SW ′ ₂ and SW ′ ₃ are turned off and the optical switch elements SW ₂ and SW ₃ are turned on, as described in the third embodiment, the optical port P ₁ -optical amplifier element AM ₁ -optical switching element SW ₂ - optical path changing element RM ₁ - optical path changing element RM ₂ - optical switch elements SW ₃ - optical amplifier element AM ₂
A loopback optical path (hereinafter referred to as optical path 1) that connects the optical ports P ₂ is formed.

[0060] At this time, the light passing through the optical switch element SW _2, corresponding to the crosstalk characteristics of the optical switching elements SW _2, a part of the light output is leaked. Then, a part of the leaked light is generated by the optical switch element SW ₂ −optical switch element SW.
₁ - optical switching element SW _'2 - optical amplifier device AM ₃ - light path connecting the optical port P ₃ (hereinafter, referred to as an optical path 2) and the optical switch element SW ₂ - optical switch elements SW ₁ - optical switch elements SW' ₃ -Optical amplifier element AM _4- Propagate through an optical path connecting the optical port P ₄ (hereinafter referred to as optical path 3).

These leaked lights reach the optical port P ₃ and the optical port P ₄ before reaching the inactive optical amplifier element A.
There is no problem because it will be absorbed by M ₃ and AM ₄ . However, when the light propagating through the optical path 1 reaches the optical switch element SW ₃ , a part of the light is
Corresponding to the crosstalk characteristic of _3, a part of the output power is slightly propagated to the dummy optical port GW _3a and emitted from the tip of the dummy optical port to become stray light. Since this stray light cannot be absorbed by the optical amplifier element, it affects the crosstalk characteristics of the optical switch element SW ₃ .

However, in the structure shown in FIG. 11, the leaked light propagating to the dummy optical port GW _3a enters the optical switch element SW ₁ again via the optical path changing element RM ₃ -dummy optical port GW _2b. . Most of the incident light propagates through the optical path 1, but a part thereof propagates to the optical path 2 or the optical path 3 and propagates to the optical amplifier element AM ₃ based on the crosstalk characteristic of the optical switch element SW _1. Or absorbed by AM ₄ .

Therefore, by arranging the loop path for stray light shown in FIG. 11, the partially leaked light of the optical switch element SW ₃ is effectively attenuated in the process of repeatedly propagating through the loop path. In each of the four types of four-port optical switches described above, an optical switch element including a ridge-shaped optical waveguide made of a semiconductor material is adopted, but the optical waveguide used for these optical switch elements is not limited to this type. Alternatively, for example, as shown in FIG. 12, the core layer 5 may be embedded in the upper clad layer 6, and the Zn diffusion region 9 may be formed in the upper clad layer 6 to be a buried type.

In each embodiment, one optical amplifier element is arranged corresponding to each of the optical ports P ₁ , P ₂ , P ₃ and P ₄ , but the number of these optical amplifier elements and The location is not limited to this,
Any number may be arranged at any place.

[0065]

As is apparent from the above description, the four-port optical switch of the present invention is manufactured by integrating each element using a semiconductor material, so that the overall shape can be miniaturized. The through state, the cross state, and the loopback state can be switched, and insertion loss, stray light, and changes in the crosstalk characteristics do not occur at the time of the switching.

Further, the insertion loss is compensated by the function of the semiconductor optical amplifier element, and the crosstalk characteristic is remarkably improved. Furthermore, by appropriately selecting the arrangement relationship of the respective elements, the lengths of the optical paths due to the switching can be made equal, so that it is possible to suppress the abnormal increase in loss due to the optical path change caused by the switching.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a basic configuration example of a 4-port optical switch of the present invention.

FIG. 2 is a schematic plan view showing an example of an optical switch element used.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a schematic plan view showing an arrangement state of optical path changing elements used.

FIG. 6 is a schematic plan view showing an example of a sectional structure of an optical amplifier element used.

FIG. 7 is a schematic plan view showing another embodiment.

FIG. 8 is a schematic plan view showing another optical switch element.

9 is a sectional view taken along line IX-IX in FIG.

FIG. 10 is a schematic plan view showing another embodiment.

FIG. 11 is a schematic plan view showing still another embodiment.

FIG. 12 is a schematic plan view showing another example of an optical switch element used.

FIG. 13 is a schematic diagram showing a 4-port optical switch.

FIG. 14 is a schematic plan view showing a 4-port optical switch described in Japanese Patent Application No. 1-137827.

FIG. 15 is a schematic plan view showing a 4-port optical switch described in Japanese Patent Application No. 1-306157.

FIG. 16 is a schematic plan view showing a 4-port optical switch described in Japanese Patent Application No. 3-52747.

[Explanation of symbols]

1,11 Semiconductor substrate 2,12 Lower electrode 3 Buffer layer 4,13 Lower clad layer 5,14 Core layer 6,15 Upper clad layer 7,16 Cap layer 8,17 Insulating thin film 8a, 17a Window 9,18 Zn diffusion region 10, 20a, 20b Upper electrode 14 Active layer SW ₁ , SW ₂ , SW ' ₂ , SW ₃ , SW' ₃ 1 Input-2
X-crossing type optical switching element for output operation SW ₄ , SW ₅ Y-branching optical switching element for 1-input and 2-output operation RM ₁ , RM ' ₁ , RM ₂ , RM' ₂ , RM ₃ , RM ' ₃ Optical path change Element (reflection mirror) RM _1a , RM _2a Reflective surface AM ₁ , AM ₂ , AM ₃ , AM ₄ Optical amplifier element WG _1a , WG _1b Input side optical port of optical switch element SW ₁ WG _1c , WG _1d Optical switch element SW ₁ output side optical port WG _2a optical switch element SW ₂ input side optical port WG _2b optical switch element SW ₂ input side optical port (dummy optical port) WG _2c , WG _2d optical switch element SW ₂ output side branch input optical port of the input optical port WG _3b optical switching element SW ₃ optical ports WG _3a optical switching element SW ₃ (dummy optical port) WG _3c, the output-side branched optical ports WG of WG _3d optical switching element SW _{3 '2a} Light switch Element SW _'2 of the output-side branched optical ports WG' _2b optical switching element SW _'2 of the output-side branched optical ports (dummy optical port) WG' _2c, WG _'2d optical switching element SW' ₂ of the input optical port WG ' _3a Optical switch element SW ' ₃ output side branch optical port (dummy optical port) WG' _3b Optical switch element SW ' ₃ output side branch optical port WG' _3c , WG ' _3d Optical switch element SW' ₃ input side light Port WG _4a Optical switch element SW ₄ input side optical port WG _4c , WG _4d Optical switch element SW ₄ output side branch optical port WG _5b Optical switch element SW ₅ input side optical port WG _5c , WG _5d optical switch element SW ₅ output side branch optical ports GW _R1 , GW ' _R1 optical ports

Claims (1)

[Claims] 1. A four-port optical switch having two input ports and two output ports and integrating a semiconductor optical switch element that performs one-input / two-output operation, and two input-side optical ports. And at least three optical switching elements including at least one X-crossing optical switching element having two output-side optical ports are arranged, one of the input-side optical ports of the X-crossing optical switching element, or / And one of the output side optical ports is optically connected to one of the output side branching optical ports of the other optical switching element, and the other of the output side branching optical ports of the optical switching element is connected via an optical path changing element. Are optically connected to each other, and an input side optical port of the optical switch element and an output side optical port of the X-crossing type optical switch element are respectively connected to the input port and the front side via a semiconductor optical amplifier element. A 4-port optical switch that is optically connected to the output port.