JPH0731330B2 - Matrix switch and driving method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a matrix switch for arbitrarily switching and connecting a plurality of input signal paths and output signal paths and a driving method thereof.

(Prior art and its problems) Due to the rapid development of optical communication systems, the capacity of transmission lines has been increased, and further advanced systems have been developed. In order to expand the functions of communication systems, new functions such as exchange of various signals and high-speed switching of transmission line networks are being demanded, and the need for an optical switching network that enables them is increasing. As a method of exchanging optical signals and switching transmission paths, (1), a method of switching by switching the optical path while keeping the light state, (2) converting an optical signal into an electrical signal once and switching in the state of the electrical signal And convert it again to an optical signal. (3) Select the signal to be output by turning ON / OFF the bias voltage to the photodetector installed at the end of the branched optical transmission line, and select the output terminal. A method of connecting to is proposed.

First, in the optical path switching type switch of (1), there are a mechanical optical switch using mechanical movement of a prism or a mirror by an electromagnet or the like and a waveguide type optical switch constituted by an optical waveguide provided on a substrate, The latter is superior in terms of reliability and possibility of multi-channelization. The waveguide type optical switch has the advantage that the optical signal can be switched at high speed as it is, but in general it is difficult to obtain normal operation unless the incident light is linearly polarized light, so it can be applied directly to ordinary single-mode optical fibers and multimode optical fiber systems. There are drawbacks such as not being possible, it is difficult to obtain sufficient crosstalk characteristics and loss characteristics, and the shape becomes large when the number of channels is increased. In the method using the electric switching circuit of (2),
Since it is a regenerative amplification system, there is no need to consider insertion loss, and it has the advantage that it does not depend on the type of optical fiber, but since signal delay and interference between signals occur in a complicated electric circuit due to stray capacitance etc. There is a drawback that it is difficult to obtain sufficient crosstalk characteristics for a wideband signal.

The method (3) has an advantage that the crosstalk can be made relatively low for a wideband signal and the electric circuit is not so complicated. FIG. 1 is a diagram for explaining the method (3). The optical signals transmitted by the input optical transmission lines 1a and 1b are branched by the optical branches 2a and 2b, and received by the photodiodes 3a, 3b, 4a and 4b, respectively. Here, the electric signal output to the output branches 5a and 5b can be switched by switching the bias applied to the photodiode according to the control signal and operating only the desired photodiode. Although this method has the above-mentioned advantages, it has a major drawback that it requires an optical branch circuit as shown in FIG. At present, the optical branch circuit is mainly manufactured by a method of bundling and fusing a plurality of optical fibers.
Generally, in the case of multiple branches, the loss becomes large,
It is difficult to obtain a small branch circuit. In addition, the method (3) has a drawback that the switching voltage of the photodiode is large and high-speed switching is difficult.

(Object of the Invention) The object of the present invention is to be compact and suitable for integration, except for the drawbacks of the various conventional optical switches described above, and to switch multi-channel wideband signals at high speed with low crosstalk. Matrix switch and its driving method.

(Structure of the Invention) In the matrix switch of the present invention, M and N are replaced by M1 and N.
When the integer is 1, M × N light emitting elements and a total of M × optically coupled to each of the light emitting elements M ×
N light control elements and 1 for M light control elements
M, consisting of a total of N photodetectors optically coupled to each other
The matrix switch has the input and N output terminals. The driving method is such that, in the matrix switch, one light emitting element is electrically connected to one of the N light emitting elements from the M input terminal. Of the light control element, the light control element is controlled to pass or block the modulated light generated by the light emitting element according to the connection state of the input and output terminals, and the light control element, The light emitting element is modulated by an input signal from an M input terminal electrically connected to one of the N light control elements, and the light emitting element emits light in accordance with a connection state of input / output terminals.
It is a driving method that is controlled so as to turn off.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram showing a 2 × 2 matrix switch which is an embodiment of the matrix switch according to the present invention and a driving method thereof. In FIG. 2, four light emitting elements 11a, 12a, 1
Light control elements 13a, 14a, 13b, and 14 for 1b and 12b, respectively.
b are optically coupled by optical transmission lines 15a, 16a, 15b, 16b, respectively, and the optical control elements 13a and 14a are connected to the photodetector 17a and the optical control elements 13b and 14b are connected to the optical detector 17b. Are optically coupled by. Here, the light emitting element is a semiconductor laser or a light emitting diode, and the photodetector is an avalanche photodiode (APD) or P
An IN photodiode or the like can be used. The light control element may be a waveguide type optical switch or optical modulator formed by an optical waveguide on the substrate, or an element that controls transmitted light by switching the injection current of a semiconductor laser (hereinafter
LD switch) can be used. FIG. 3 is a plan view showing an example of the waveguide type optical switch. Optical waveguides 21 and 22 are formed on a dielectric or semiconductor substrate that exhibits an electro-optical effect, such as lithium niobate or an InP substrate, by metal diffusion, crystal growth, or the like, and the optical waveguides 21 and 22 are placed close to each other by about several μm. The control electrode 23 is installed on the adjacent optical waveguide, and the light amount or the optical path of the transmitted light is controlled by the voltage applied to the control electrode 23. The incident light 24 to the optical waveguide 21 is coupled to the optical waveguide 22 and becomes the emitted light 27 when the applied voltage to the control electrode 23 is 0. At an appropriate applied voltage, the incident light 24 is re-coupled to the optical waveguide 21 and emitted light 25. Becomes Also,
The emitted light 25 can be modulated by applying a modulation voltage to the control electrode 23. FIG. 4 is a sectional view showing an example of the LD switch. In FIG. 4, when the injection current to the semiconductor laser 30 having a normal Pn junction is turned on, the semiconductor laser 30 functions as an optical amplifier and the incident light 31 is amplified and emitted. When the injection current is turned off, the incident light 31 is absorbed and the outgoing light 32 becomes zero. That is, in this LD switch, incident light can be transmitted or blocked by turning on or off the injection current, or transmitted light can be modulated by modulating the injection current.

The embodiment shown in FIG. 2 has two input terminals 10a and 10b and two output terminals 20a and 20b, and the signal input to the input terminal 10a is amplified by the amplifier 18a and applied to the light emitting elements 11a and 11b. The signal input to the input terminal 10b is amplified by the amplifier 18b and applied to the light emitting elements 12a and 12b. as a result,
The light emitting elements 11a, 11b are modulated by the signal inputted to the input terminal 10a, the light emitting elements 12a, 12b are respectively modulated by the signal inputted to the input terminal 10b, and the modulated lights thereof are respectively light control elements 13a, 13b, 14a, It is incident on 14b. Here, all of the above four light control elements are connected to the controller 19 and are controlled by a control voltage or a control current generated by the controller 19 so as to independently transmit or block incident light. The controller 19 is a device that drives four light control elements based on a command from a central control device (omitted in FIG. 2). For example, when a light control element that transmits or blocks incident light according to the magnitude of the applied voltage as shown in FIG. 3 is used, two voltages are independently applied to the four light control elements. Occur.
As the simplest example, one for one light control element
It can be composed of a circuit using two transistors. For example, the collector of the transistor is connected to the power source of the voltage V ₁ through the resistor R, the emitter is grounded, the base is the input terminal of the control signal, and the output voltage terminal is output from the collector. In this circuit, the output voltage is V ₁ when the control signal voltage is 0, and the output voltage is 0 when the control signal voltage is positive.
Becomes When using a light control element that transmits or blocks incident light depending on the presence or absence of an injection current as shown in FIG. 4, the controller 19 controls the four light control elements based on a command from the central controller. Two independent currents,
That is, the current 0 or an arbitrary current I ₁ is generated. The simplest configuration for one light control element is a circuit using one transistor. For example, the n side of the Pn junction of the LD switch, which is an optical control element, is connected to the collector side of the transistor via the resistor R _1.
Side is connected and the P side is grounded. Also, connect the emitter side of the transistor to the negative power supply voltage -V _1, the input terminal of the base control signal. When the base potential of the transistor is 0, the transistor is turned on, so a current I ₁ = V ₁ / (R ₁ + r ₁ + r ₂ ) flows through the LD switch. Where r ₁
Is the resistance of the LD / switch and r ₂ is the resistance of the transistor. On the other hand, when a sufficiently large negative voltage is applied to the base of the transistor, the transistor is turned off and the current becomes zero. The optical signal passing through the light control elements 13a and 14a is detected by the photodetector 17a and transmitted to the output terminal 20a, and the light passing through the light control elements 13b and 14b is detected by the photodetector 17b and output to the output terminal 20b. Transmitted. As an example of the connection between the input and output terminals, for example, the light control elements 14a, 13b in the cutoff state,
If the other is made transparent, the input terminal 10a is connected to the output terminal 20a and the input terminal 10b is connected to the output terminal 20b. Also, the light control element
If input 13a and 13b are transmitted and the others are cut off, input terminal 10a
A so-called broadcast mode connection in which both output terminals 0a and 20b are connected is also possible.

If the matrix optical switch of this embodiment is made of a semiconductor material such as GaAs or InP, all the amplifiers, light emitting elements, light control elements, photodetectors, etc. can be monolithically integrated on the same substrate. The shape can be made small and multi-channel is possible. In addition, since the input signal transmission system and the control circuit part that controls the switch are configured independently, it becomes much easier to control a wideband signal than a switching element using an ordinary electric circuit, and the extinction as an optical control element is possible. By using an element having a high ratio, low crosstalk switching can be performed. Also in FIG.
In the light control element shown in FIG. 4, a switching speed of / nsec or less can be obtained relatively easily.

FIG. 5 is a diagram showing a 2 × 2 matrix switch which is another embodiment of the matrix switch according to the present invention and a driving method thereof. In the embodiment shown in FIG. 5, four light emitting elements 11a and 12 are used.
a, 11b, 12b, four light control elements 13a, 14a, 13b, 14b,
The arrangement and configuration of the two photodetectors 17a and 17b and the elements of the optical transmission line connecting them are exactly the same as those in the embodiment of FIG. However, in this embodiment, the signal input from the input terminal 10a is amplified by the amplifier 40a, and the light control elements 13a and 13b are amplified.
The signal applied to the input terminal 10b is applied to the amplifier 4
It is amplified by 0b and applied to the light control elements 14a and 14b.
Further, the light emitting elements 11a, 12a, 11b, 12b are all the controller 4
It is connected to 1 and is controlled by a control current generated by the controller 41 to turn on or off light emission independently. The configuration of the controller 41 is the same as the case of using the LD switch for the light control element in the embodiment of FIG. 2, and the current is turned on and off independently for each of the four light emitting elements based on a command from the central control unit. To do. Also in the 2 × 2 matrix switch of this embodiment, input / output terminals can be arbitrarily connected as in the embodiment of FIG. For example, the light emitting elements 12a and 11b
Is turned on and the other light emitting elements are turned off, the input terminal 10a is connected to the output terminal 20b and the input terminal 10b is connected to the output terminal 20a.

The matrix switch of the present embodiment is smaller and more suitable for integration than the conventional matrix switch, as in the example of FIG. 2, and can switch multi-channel wideband signals at high speed with low crosstalk. Compared with the embodiment of FIG. 2, this embodiment generally provides a higher extinction ratio when the light emitting element is turned on and off than the light transmission and cutoff control of the light control element. It can be said that this embodiment is more advantageous.

FIG. 6 is a diagram showing a 2 × 2 optical matrix switch according to another embodiment of the present invention. In this embodiment, the 2 × 2 matrix switch shown in FIG. 2 or 5 is combined with a photoelectric converter to form a matrix switch having two optical inputs and two optical outputs. In this embodiment, the input optical signal 60a transmitted through the input optical fiber 51a is detected by the photodetector 52a, and the second optical signal 60a is detected.
It is input to the input terminal 10a of the 2 × 2 matrix switch 50 shown in FIG. The input optical signal 60b transmitted through the input fiber 51b is detected by the photodetector 52b and input to the input terminal 10b of the 2 × 2 matrix switch 50. 2x
Amplifiers 53a and 53b and light emitting elements 54a and 54b are connected to output terminals 20a and 20b of the two-matrix switch 50, respectively, and output optical signals 70 generated by the light emitting elements 54a and 54b, respectively.
The a and 70b are incident on the output optical fibers 55a and 55b, respectively. That is, in this embodiment, the input optical signal transmitted through the input optical fibers 51a and 51b is regenerated, amplified and coupled to any one of the output optical fibers 55a and 55b.
It goes without saying that the 2 × 2 optical matrix switch of this embodiment also has the features of the embodiments of FIGS. 2 and 5 described above.

As described above, according to the present invention, a matrix switch which is small in size, suitable for integration, capable of high-speed switching of multi-channel wideband signals with low crosstalk, and a driving method thereof can be obtained.

The present invention is not limited to the above embodiment. For example, the number of input / output terminals can be increased to 4 × 4, 8 × 8, 32 × 32, and the like. An input signal amplifier may also be provided independently for each light emitting element or each light control element. Further, the photodetectors 17a and 17b are separately installed so as to face the respective light control elements, and they are installed as shown in FIG.
A method of electrically connecting so as to function similarly to the illustrated embodiment is also possible. In the present invention, the photodetectors electrically connected as described above are treated as the same photodetector.

Further, in the embodiments of FIGS. 2 and 5, the light waves emitted from the M light control elements are once combined as a means for coupling the M light control elements forming each row to the photodetector. The effect of the present invention can be obtained by merging the light with a photocoupler and coupling it to the photodetector, or by further emitting the light merging device and then transmitting a light wave through the optical transmission line and then coupling the photowave to the photodetector.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a conventional matrix switch, FIGS. 2, 5, and 6 are diagrams showing an embodiment of a matrix switch according to the present invention, and FIGS. 3 and 4 are used for the present invention. It is a figure which shows an example of a light control element. In the figure, 11a, 1
1b, 12a, 12b are light emitting elements, 13a, 13b, 14a, 14b are light control elements, 17a, 17b are photodetectors, 18a, 18b, 40a, 40b are amplifiers, 19, 41 are controllers, 10a, 10b are inputs Terminal, 20
a and 20b are output terminals.

Claims (5)

[Claims] 1. When M and N are integers such that M ≧ 1 and N ≧ 1, M × N light-emitting elements and a total M optically coupled to each one of the light-emitting elements. × N light control elements,
A matrix switch having M input and N output terminals consisting of N photodetectors optically coupled to M of the light control elements. 2. An M: 1 light combiner is used as a means for optically coupling M light control elements to one photodetector. Matrix switch. 3. An M: 1 optical combiner and an optical transmission line connected to the optical combiner are used as means for optically coupling the M optical control elements to one photodetector. The matrix switch according to claim 1, which is characterized in that. 4. When M and N are integers such that M ≧ 1 and N ≧ 1, M × N light-emitting elements and 1 for each of the light-emitting elements.
M inputs consisting of a total of M × N light control elements optically coupled one by one and N photodetectors optically coupled to M of the light control elements, N inputs, N In a matrix switch having an output terminal, the light emitting element is modulated by an input signal from an M input terminal electrically connected to one of the N light emitting elements, and the light control elements respectively emit the light. A method of driving a matrix switch, wherein modulated light generated by an element is controlled so as to pass or block according to a connection state of input / output terminals. 5. When M and N are integers such that M ≧ 1 and N ≧ 1, M × N light-emitting elements and 1 for each of the light-emitting elements.
M inputs consisting of a total of M × N light control elements optically coupled one by one and N photodetectors optically coupled to M of the light control elements, N inputs, N In a matrix switch having an output terminal, the light control element is modulated by an input signal from an M input terminal electrically connected to one of the N light control elements, and the light emitting element is an input / output terminal. A method for driving a matrix switch, wherein light emission is controlled to be turned on or off according to a connection state of the matrix switch.