JP2003177438A - Optical switch and driving method of the switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical switch in which switching time is reduced, manufacturing is made easy and the cost is reduced and to provide a driving method of the switch in which reliability is secured. <P>SOLUTION: When a phase varying film of an optical path switching means 25 of an optical switch 20 becomes a crystal state i.e. a first switching state, light beams L1 being inputted into a first input connector section 21 are led to a first output connector section 23 and light beams L2 inputted into a second input connector section 22 are led to a second output connector section 24. When the phase varying film of the means 25 becomes an amorphous state i.e. a second switching state, the light beams L1 being inputted into the section 21 are led to the section 24 and the light beams L2 being inputted into the section 22 are led to the section 23. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switch and a method for driving the optical switch.

[0002]

2. Description of the Related Art Conventionally, optical communication using optical fibers, which has been mostly used for trunk lines connecting countries, is spreading not only to trunk lines but also to general households with the spread of the Internet in recent years. Is starting to appear. As the laying of optical fibers progresses, not only high performance is required for each component used for optical communication, including a single optical fiber, but also cost reduction is required. Above all, at the branch point in the optical fiber network, the optical switch is used to switch the signal, which was conventionally performed by replacing the optical signal with an electrical signal and then converting the electrical signal into light again. It is being studied to make it happen.

As described below, as a configuration of an optical switch, a configuration is considered in which an optical component such as a prism is arranged in the optical path to spatially switch the propagation direction of light. FIGS. 15A and 15B are explanatory views showing an example of a cross-connect type optical switch. The optical switch 10 has two optical fibers (shown as fiber in the figure).
The ends of I1 and I2 are combined to form each of these optical fibers I.
Light is input from the optical fibers O1 and I2, and the ends of the two optical fibers O1 and O2 are coupled to output light to the optical fibers O1 and O2. The optical switch 10 includes an optical fiber I by mounting a prism 12 on a linear actuator composed of an electromagnetic actuator (not shown).
The light L1 from the optical fiber O1 is guided to the optical fiber O1, and the light L2 from the optical fiber I2 is guided to the optical fiber O2.
When the light is guided to, the prism 12 is retracted to a position deviated from the optical path. On the other hand, when the light from the optical fiber I1 is guided to the optical fiber O2 and the light from the optical fiber I2 is guided to the optical fiber O1, the prism 12 is inserted at the position in the optical path, so that each optical fiber I1, The light output from I2 is refracted.

As an example of an optical switch having another structure, there is a system using an active mirror which is being studied by Lucent, and the introduction of an optical switch using a micromachine technology, which has been remarkably developed in recent years, is also considered. Has been done. The optical switch using the active mirror is one in which a mirror formed on a silicon substrate moves in response to an electric signal to change its reflection angle, thereby changing the propagation direction of light. Since this mirror is very fine, the switching time is greatly shortened to about 20 μsec.

[0005]

However, in the optical switch using the prism described above, the time required for switching is large because the heavy optical component called the prism must be actually moved by a distance on the order of mm. As a result, it takes several tens of msec. Furthermore, because it is not easy to downsize the optical components such as prisms that can change the traveling direction of light and the actuators equipped with those optical components to the optical fiber diameter level, array them at the array pitch of the optical fibers. Since there is a drawback that it is difficult to do so, there is a drawback that the size of the device is eventually increased. Further, although the optical switch using the method using the active mirror described above can shorten the switching time, it is stable in driving because the configuration and the process for manufacturing the mirror are complicated. Arranging multiple mirrors is not easy. Further, since it is not easy to do so, high cost is a concern. Also,
It is required to improve reliability when such an optical switch is used for a long period of time or when the environment in which it is used changes greatly. The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical switch that can shorten the switching time, is easy to manufacture, and is low in cost. Another object of the present invention is to provide a method of driving an optical switch, which is advantageous in ensuring reliability.

[0006]

In order to achieve the above object, the present invention provides a first input connector section to which light is input,
First and second output connector sections that output the light input to the first input connector section, and the first and second output connector sections that output the light input to the first input connector section In an optical switch provided with an optical path switching means for switching and guiding to either one of the
A multilayer film configured to be switchable between two states, a first state of transmitting light and a second state of reflecting light, is provided when the multilayer film is in the first state. The light input from the first input connector unit is transmitted through the multilayer film and guided to the first output connector unit, and the first film is formed when the multilayer film is in the second state. The light input from the input connector unit is reflected by the multilayer film and the second
It is characterized in that it is configured so as to be guided to the output connector section of. Therefore, according to the present invention, by switching the multi-layer film of the optical path switching means to the first and second states, the light input to the first input connector section can be transmitted to the first and second output connector sections. The output is switched to either one.

According to the present invention, there is provided a first input connector section for receiving light, first and second output connector sections for outputting the light input to the first input connector, and the first and second output connector sections. An optical path switching unit that guides light input to one input connector unit by switching to one of the first and second output connector units, the optical path switching unit being in a first state of transmitting light. And a second state in which light is reflected, the multilayer film is configured to be switchable between two states, and when the multilayer film is in the first state, an input is made from the first input connector unit. Light transmitted through the multilayer film to be guided to the first output connector section, and the light input from the first input connector section when the multilayer film is in the second state. Is reflected by the multilayer film and guided to the second output connector section. It is configured so that, the multilayer film,
In the first state, the first refractive index has a high transmittance and a low reflectance, and in the second state, the second refractive index has a low transmittance and a high reflectance. And a second conductive layer made of a conductive material on both sides in the thickness direction of the thin film, respectively. The capacitance generated between the two conductive layers is measured,
A first layer of the multilayer film based on the measured capacitance,
It is characterized in that the second state is monitored. for that reason,
According to the present invention, by monitoring the first and second states of the multilayer film based on the capacitance generated between the first and second conductive layers provided in the optical switch, The state of the refractive index in the multilayer film can be monitored.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an optical switch and a driving method thereof according to the present invention will be described below in detail with reference to the drawings. 1A and 1B are explanatory views showing the configuration of the optical switch according to the first embodiment. As shown in FIG. 1, the optical switch 20 includes two optical fibers I1 and I2.
Of the first input connector portion 21 and the second input connector portion 22 to which the ends of the optical fibers O1 and O2 are coupled, and the second output connector portion 24 and the first output connector portion 23 to which the ends of the optical fibers O1 and O2 are coupled. And the first and second input connector portions 22
And an optical path switching means 25 for switching and guiding the lights L1 and L2 introduced to the first and second output connector sections.

The two optical fibers I1 and I2 are for inputting the lights L1 and L2 to the first and second input connector portions 21 and 22, respectively.
1, O2 are the first and second output connector portions 23, 2
Lights L1 and L2 output from the optical fiber 4 are output. The first input connector portion 21 and the first output connector portion 23, and the second input connector portion 22 and the second output connector portion 24 are the optical path switching means 25.
Are sandwiched between. And the optical switch 20
The light L1 input from the first input connector section 21 is transferred to the first output connector section 2 by the optical path switching means 25.
3 or the second input connector section 24 and the second input connector section 24.
The light L2 inputted from 2 is switched and guided by the optical path switching means 25 to the first output connector section 23 or the second output connector section 24.

FIG. 2 is a sectional view showing the structure of the optical path switching means 25, and FIG. 3 is a plan view of the optical path switching means 25. The optical path switching means 25 includes a multilayer film 26, two glass substrates 27 and 28 sandwiching the multilayer film 26, and two conductor patterns 29 connected to the portion of the multilayer film 26. As shown in FIGS. 2 and 3, the multilayer film 26 is formed in a rectangular plate shape in plan view. The multilayer film 26 includes a silicon layer 260.
2, and silicon oxide layers 2604 and 2606 formed on both surfaces of the silicon layer 2602, respectively, and phase change films 2608 and 2610 formed of a phase change material formed on outer surfaces of the silicon oxide layers 2604 and 2606, respectively.
(Corresponding to a thin film in claims) and the phase change film 26
08 and 2610, and silicon nitride layers 2612 and 2614 formed on the outer surfaces of the silicon nitride layers 26 and 26, respectively.
Silicon layers 2616 and 2618 formed on the outer surfaces of the glass substrates 12 and 2614 and facing the glass substrates 27 and 28, respectively.
It has and.

The refractive index n and the dimension t in the thickness direction in this example are as follows. Glass substrate 27, 28: n = 1.5 Silicon layer 2602: n = 3.5, t = 240 nm Silicon oxide layer 2604, 2606: n = 1.47, t
= 100 nm Phase change films 2608 and 2610: t = 25 nm Silicon nitride layers 2612 and 2614: n = 2.0, t =
230 nm silicon layers 2616, 2618: n = 3.5, t = 24
0 nm

Here, the phase change films 2608 and 2610 are used.
The phase change material constituting the will be described. In this example, the phase change film is made of a phase change material made of Ge2Sb2Te5. The phase change material made of Ge2Sb2Te5 is a material that can be in a plurality of states such as a crystallized state and an amorphous state depending on the difference in heat treatment temperature and the cooling rate after heating, and is also used as a recording material for optical disk devices. is there. FIG. 4A shows the phase change films 2608 and 26.
10 is a characteristic diagram showing the measurement results of the refractive index (n, k) when the wavelength is changed (350 nm to 1700 nm) in the case where the phase change material constituting 10 is in an amorphous state, FIG. It is a characteristic diagram which shows the measurement result of the refractive index (n, k) when changing a wavelength (350 nm-1700 nm) in the case where the phase-change material which comprises the change films 2608 and 2610 is in a crystalline state. The refractive index of the phase change film is expressed as a complex number, that is, n-ik. It is shown that the larger the value of the imaginary part k, the larger the light absorption in the film, and the smaller the value of k in the imaginary part, the smaller the light absorption in the film.

Then, the phase change films 2608 and 2610 are used.
Has a refractive index of n = 5.622 in the amorphous state.
4-0.9461i (corresponding to the first refractive index in the claims), and n = 7.8361-2.
7961i (corresponding to the second refractive index in the claims) (however, the wavelength is 1550 nm). Further, the glass substrates 27 and 28, the silicon layer 2602, the silicon oxide layers 2604 and 2606, the phase change films 2608 and 2610, the silicon nitride layers 2612 and 2614, and the silicon layer 261.
Reference numerals 6 and 2618 have a function of enhancing (enhancing) the change in the refractive index of the phase change films 2608 and 2610.

Next, how the reflectance and transmittance of the multilayer film 26 change depending on the states (amorphous state and crystalline state) of the phase change films 2608 and 2610 will be described. FIG. 5 is a characteristic diagram showing how the reflectance of the multilayer film 26 changes with the thickness of the phase change films 2608 and 2610. FIG. 6 shows the phase change films 2608 and 261.
FIG. 6 is a characteristic diagram showing how the transmittance of the multilayer film 26 changes with respect to the thickness of 0. Here, each phase change film 26
The thicknesses of 08 and 2610 were assumed to be equal, and calculation was performed using the thicknesses as parameters. The wavelength is 1550n
m, the input angle (the angle formed by the axial directions of the optical fibers I1, I2, O1 and O2 with respect to the glass substrates 27 and 28 is 10 deg, and the light is P-polarized).
The configuration example described above (the thickness of each phase change film is 25 n
m), the reflectance in the amorphous state is 0.9% and the transmittance in the amorphous state is 26.5.
%, The reflectance in the crystalline state is 33%, and the transmittance in the crystalline state is 1.4%.
The extinction ratio is more than double.

The silicon layer 2602 of the multi-layer film 26 is formed by adding, for example, boron or the like, and when the current is supplied to the silicon layer 2602, heat is generated to heat the phase change films 2608 and 2610. Are configured. As shown in FIG. 3, one end of each conductor pattern 29 is connected to each end of two opposite sides of the silicon layer 2602 of the multilayer film 26, and the other end of each conductor pattern 26 is Connected to the current supply circuit of the abbreviation,
It is configured to supply a current pulse described later to the silicon layer 2602. In addition, each of the conductor patterns 2
9 is preferably formed in a portion where the light output from each of the optical fibers I1 and I2 is not applied. Since each conductor pattern 29 is not required to have optical characteristics, a metal material such as aluminum can be used.

Next, a method of switching the phase change films 2608 and 2610 between the crystalline state and the amorphous state will be described. The subsequent state of the phase change material is switched to the crystalline state or the amorphous state due to the difference in the cooling rate after it is heated. In order to bring the phase change material into an amorphous state, it may be cooled rapidly after heating. That is, the phase change film is likely to be rapidly cooled to a high temperature and then rapidly cooled, so that the phase change film can be brought into an amorphous state by rapidly increasing the temperature. In order to bring the phase change material into a crystalline state, it takes time for the crystal nuclei to be formed after heating and for the crystal to grow. That is, the crystalline state can be obtained by heating the phase change film to a temperature lower than that in the case of making it in an amorphous state and then slowly cooling it. Therefore, the state of the phase change film can be switched depending on the difference in the heating temperature, that is, the difference in the amount of heat supplied to the phase change film.

FIG. 7 is a waveform diagram of the energy supplied from the current supply circuit to the phase change film. The horizontal axis represents time, and the vertical axis represents the energy supplied to the phase change film. This supplied energy corresponds to the amount of current supplied to the silicon layer 2602. In FIG. 7, P1 is a range of energy required to heat the phase change film to an amorphous state after cooling, and P2 is a temperature to heat the phase change film to a crystalline state after cooling. Indicates the required energy range. However, P1> P2.

As shown in FIG. 7A, in order to make the phase change film amorphous, the energy range P1
In order to apply the energy of 2 to make the phase change film into an amorphous state as shown in FIG. 7B, the energy in the energy range P2 may be applied. In this example, by supplying a plurality of short pulse energy, that is, a plurality of short pulse currents to the silicon layer 2602, the heat distribution in the in-plane direction of the silicon layer 2602 is made uniform and the phase change film. Is heated evenly. As a result, the variation in the change of the refractive index within the plane of the phase change film is suppressed.

Next, the operation of the optical switch according to the first embodiment configured as described above will be described. Figure 1
As shown in (a), it is assumed that the light L1 is input from the optical fiber I1 to the first input connector section 21 and the light L2 is input from the optical fiber I2 to the second input connector section 22. And in the initial state,
Phase change film 260 of the multilayer film 26 of the optical path switching means 25
8, 2610 is in a crystalline state. The light L1 input to the first input connector unit 21 passes through the glass substrate 27 of the optical path switching unit 25 and enters the multilayer film 26, and the light L2 input to the second input connector unit 22 is an optical path. It passes through the glass substrate 28 of the switching means 25 and enters the multilayer film 26. As shown in FIGS. 5 and 6, the phase change films 2608 and 2610 in the crystalline state have a reflectance of 33 in the crystalline state.
%, And the transmittance is 1.4%, the lights L1 and L2 are reflected by the phase change films 2608 and 2610 and guided to the first output connector unit 23 and the second output connector unit 24, respectively.

Next, when a short pulse current (energy) as shown in FIG. 7A is supplied to the silicon layer 2602 of the multilayer film 26 by the current driving circuit, each phase change film 2608. , 2610 is the energy range P
By applying energy up to 1, heating, and then rapid cooling, the crystalline state is changed to the amorphous state. The light L1 input to the first input connector unit 21 is
The multilayer film 2 is passed through the glass substrate 27 of the optical path switching means 25.
The light L2 that enters 6 and enters the second input connector unit 22 passes through the glass substrate 28 of the optical path switching unit 25 and enters the multilayer film 26. As shown in FIGS. 5 and 6, the phase-change films 2608 and 2610 in the crystalline state have a reflectance of 0.9% and a transmittance of 26.5% in the amorphous state. These phase change films 2608, 2
610, and the second output connector section 24 and the first output connector section 2 via the glass substrates 28 and 27, respectively.
Guided by 3.

Next, when a short pulse current (energy) as shown in FIG. 7B is supplied to the silicon layer 2602 of the multilayer film 26 by the current driving circuit, each phase change film 2608. , 2610 is the energy range P
By applying energy up to 2, heating and then slowly cooling, the amorphous state is changed to the crystalline state. As a result, the initial state described above is restored.

Therefore, when the phase change films 2608 and 2610 of the optical path switching means 25 are in a crystalline state, the optical switch 20 outputs the light L1 input to the first input connector section 21 to the first output connector section. In the first switching state, the light L2 input to the second input connector section 22 is guided to the second output connector section 24 while being guided to the second input connector section 23.
When the phase change films 2608 and 2610 of the optical path switching means 25 are in an amorphous state, the light L1 input to the first input connector section 21 is transmitted to the second output connector section 2
The second switching state in which the light L2 input to the second input connector unit 22 is guided to the first output connector unit 23 while being guided to the first input connector unit 23. Therefore, according to the optical switch of the present embodiment, the phase change films 2608 and 2610 are heated to heat the phase change films 2608 and 2610 during the switching time for switching the first and second switch states. This is advantageous in shortening the switching time because it requires only a short time. Further, the optical path switching means 25 does not require a prism or an actuator for moving the prism,
Since it is easy to manufacture unlike an active mirror, it is advantageous in reducing the size and cost of the optical switch.

Further, in the first embodiment, since the multilayer film 26 is composed of symmetrical layers on both sides of the silicon film 2602 with respect to the silicon film 2602, as shown in FIG. By inputting light from two input connector portions respectively located on both sides of the multilayer film 26, one multilayer film 26 switches the light input from these two input connector portions to two output connector portions and outputs the cross. A connect type optical switch can be constructed.

In the first embodiment described above, the light input from the optical fibers I1 and I2 to the switching means 25 is directly guided to the multilayer film 26.
In practice, the light guided to the multilayer film 26 is applied to the multilayer film 26 portion by making it into a collimated state by using an optical lens or condensing the light on the multilayer film 26 by an optical lens having a low NA. It is desirable that the emitted light be in a state close to a plane wave. The reason is that it is not easy to equalize the reflectance or the transmittance when light having various angle components is input to the multilayer film 26. Further, by making the number of layers constituting the multilayer film 26 larger than that in the example shown in FIG. 2, the reflectance or the transmittance is made uniform even if the light irradiated to the portion of the multilayer film 26 is not a plane wave. It is also possible to do so.

Further, the optical path switching means 2 shown in FIG.
It is needless to say that the material of each part constituting 5 is merely an example, and it is not necessary to limit to these materials. For example, it is possible to replace one or both of the glass substrates 27 and 28 in FIG. 2 with a UV curable resin.

Next, a second embodiment will be described. The second embodiment differs from the first embodiment in the configuration of the heating means for heating the phase change film. As shown in FIG. 8, the heating means 30 includes a semiconductor laser 32,
The collimator lens 34 and the condenser lens 36 are provided. The laser light 38 emitted from the semiconductor laser 32 is collimated by the collimator lens 34, converged by the condenser lens 36, and applied to the portion of the multilayer film 26. The phase change films 2608 and 2610 may be heated by the focused laser light 38. The energy applied to the phase change films 2608 and 2610 is as shown in FIG.
The same energy as the short pulse energy as shown in (a) and (b) can be adopted. As shown in FIG. 8, since the portion (layer or film) having the absorptance of the laser beam in the multilayer film 26 is only the phase change film,
Since only the phase change film can be effectively heated,
Rapid cooling can be easily performed when the phase change film is made amorphous.

The light emitted from the semiconductor laser 32 used in the example shown in FIG. 8 can be light having a shorter wavelength than the light guided through the optical fiber which propagates data. Is. And specifically,
By using the semiconductor laser 32 that outputs a wavelength near 650 nm, in addition to the advantage that the light source can be obtained at low cost, it can be seen from the refractive index characteristics of the phase change material shown in FIGS. 4 (a) and 4 (b). And the absorption rate of the phase change material is 6
Since it is high in the wavelength range around 50 nm, it is effective from the viewpoint of energy utilization.

As shown in FIG. 8, in the second embodiment, the light guided from the optical fiber is not used, and another light source (semiconductor laser 32) and another optical component (collimator lens 34, An example using a condenser lens 36) is shown, but the state of the phase change film is switched by guiding the power for changing the state of the phase change material from an optical fiber and irradiating and heating the phase change film. It can also be configured as follows.

Next, a third embodiment will be described.
Due to the difference in the state of the phase change material, the electrical characteristics (specifically, the dielectric constant) of the phase change material change along with the change of the refractive index.
Therefore, the optical state of the phase change films 2608 and 2610, that is, the state of the refractive index, can be monitored by measuring the dielectric constant, that is, the capacitance, which is the electrical characteristic of the phase change film. As a means for measuring the capacitance of the phase change film, a conductive film may be arranged so as to sandwich the phase change film, and the capacitance between the films may be measured. Thereby, the refractive index of the phase change film can be monitored with high accuracy. With such a configuration, since the operation of the optical switch is also electrically monitored, when the switching of the optical switch fails, the failure can be easily detected. If the switching fails, the failure can be detected before the light is input from the optical fiber to the optical switch.Therefore, switch the optical switch again before inputting the light to the optical switch. You can also Therefore, it is advantageous in improving the reliability of the operation of the optical switch.

Further, the switching state of the phase change film can be electrically detected without performing an optical evaluation of the energy required to switch the phase change film between the crystalline state and the amorphous state. Therefore, when the optical switch is used for a long period of time, or when the optical switch is used in an environment where the ambient temperature is different, it is advantageous in adjusting the conditions necessary for reliably switching the state of the phase change film. .

Specifically, the amount of input energy required to crystallize the phase change film or the amount of input energy required to bring it into an amorphous state changes due to the influence of the external environment or changes due to long-term use. Even in such a case, the state of change in the refractive index of the phase change film can be electrically evaluated. Therefore, it is possible to easily adjust the amount of input energy for bringing the phase change film into the crystalline state or the amount of input energy for bringing the phase change film into the amorphous state. Further, in the structure of the multilayer film of the optical switch shown in FIG. 2, the phase change films 2608 and 261 are used.
Silicon layers 2602, 2616, 261 so as to sandwich 0
8 is provided. Therefore, when these silicon layers are made of a conductive material, the capacitance (dielectric constant) between these silicon layers can be detected to detect the state of the phase change film.

Next, a fourth embodiment will be described.
FIG. 9 is an explanatory diagram showing a configuration in which a plurality of optical switches are integrally provided. As shown in FIG. 9, the optical switch 30 is
Four first input connector parts (not shown) to which the four optical fibers I11 to I14 are coupled, and four first output connector parts (not shown) to which the four optical fibers O11 to O14 are coupled. And four optical fibers I21 to I2
4 second input connector parts (not shown) to which 4 is connected
By providing four second output connector parts (not shown) to which the four optical fibers O21 to O24 are coupled and four optical path switching means 20, four independent optical switches are integrated. Are configured as

The optical path switching means 20 comprises a single substrate 32.
It is composed of four optical path switching means provided above. The substrate 32 is the glass substrate 27 in FIG.
It corresponds to 28. The part of the optical switch 30 that needs to be patterned is a silicon layer as a heating means for heating the phase change film, a wiring part for supplying a current to the silicon layer as the heating means, and a capacitance of the phase change film. Such as the electrical wiring part for monitoring
Its configuration is simple. Therefore, the fabrication thereof is very easy, and it is not difficult to stabilize the operation, and thus it is easy to form the optical switches in multiple arrays. Therefore, the optical switch of the present invention is advantageous in integrating a large number of optical switches.

Next, a fifth embodiment will be described. FIG. 10 is an explanatory diagram showing the configuration of the optical switch according to the fifth embodiment. The fifth embodiment is different from the first embodiment in that light is input to the optical switch from only one side of the multilayer film, and the multilayer film to which light is input is connected to the number of output connector units. The same number is provided. That is, as shown in FIG. 10A, the optical switch 40
Is a first input connector section 41 and a second input connector section 42 to which the ends of the two optical fibers I1 and I2 are coupled.
And a first output connector section 43 and a second output connector section 44 to which the ends of the optical fibers O1 and O2 are coupled, and the light L1 input to the first input connector section 41 to the first and second output connector sections 43 and 44, respectively. Optical path switching means 45A for switching and guiding to the second output connector portions 43 and 44, and the second input connector portion 4
The optical path switching means 45B is provided for switching and guiding the light L2 input to the first and second output connector portions 43 and 44.

As shown in FIG. 11, the optical path switching means 4
5A and 45B include a multilayer film 46 and two glass substrates 47 and 48 sandwiching the multilayer film 46. Multilayer film 4
6 is formed in a rectangular plate shape in a plan view. The multilayer film 46
Is a silicon nitride layer 46 formed on the glass substrate 47 side.
02, a silicon layer 4604 formed on the silicon nitride layer 4602, a silicon nitride layer 4606 formed on the silicon layer 4604, and a phase change film 4608 formed on the silicon nitride layer 4606. And a silicon nitride layer 4610 formed between the phase change film 4608 and the glass substrate 48. The refractive index n and the dimension t in the thickness direction in this example are as follows. Glass substrate 47, 48: n = 1.47 Silicon nitride layer 4602: n = 2.0, t = 140 nm Silicon layer 4604: n = 3.5, t = 250 nm Silicon nitride layer 4606: n = 2.0, t = 50 nm Phase change film 4608: t = 150 nm Silicon nitride layer 4610: n = 2.0, t = 400 nm The refractive index of the phase change film 4608 and the wavelength of the target light are the first.
This is the same as the embodiment.

Next, how the reflectance and transmittance of the multilayer film 46 change depending on the state (amorphous state and crystalline state) of the phase change film 4608 will be described. FIG. 12 is a characteristic diagram showing how the reflectance of the multilayer film 46 changes with respect to the thickness of the phase change film 4608.
FIG. 13 shows that the thickness of the phase change film 4608 is different from that of the multilayer film 46.
FIG. 6 is a characteristic diagram showing how the transmittance of γ changes. Here, calculation was performed using the thickness of each phase change film 4608 as a parameter. The wavelength is 1550 nm, and the input angle (the angle formed by the axial directions of the optical fibers I1, I2, O1 and O2 with respect to the glass substrates 47 and 48 is 10d).
and the light is P-polarized. In the above-described configuration example (thickness of the phase change film is 15 nm), the reflectance in the amorphous state is 0.3%, the transmittance in the amorphous state is 21%, and the reflectance in the crystalline state is 19.5%. The transmittance in the crystalline state is 1.5%, and the extinction ratio is 10 times or more.

Next, the operation of the optical switch according to the fifth embodiment configured as described above will be described. Figure 1
As shown in 0 (a), it is assumed that the light L1 is input from the optical fiber I1 to the first input connector unit 41 and the light L2 is input from the optical fiber I2 to the second input connector unit 42. Then, in the initial state, the phase change film of the multilayer film 46 of the optical path switching unit 45A is in an amorphous state, and the phase change film of the multilayer film 46 of the optical path switching unit 45B is in a crystalline state.

The light L1 input to the first input connector section 41 passes through the glass substrate 47 of the optical path switching means 45A and enters the multilayer film 46. The light L2 input to the second input connector unit 42 passes through the glass substrate 47 of the optical path switching unit 45B and enters the multilayer film 46. 12 and 13
As shown in FIG.
The light L1 is 3%, the transmittance in the amorphous state is 21%, the reflectance in the crystalline state is 19.5%, and the transmittance in the crystalline state is 1.5%.
After passing through, the light L2 is reflected by the phase change film 4608 and guided to the second output connector section 44 and the first output connector section 43, respectively.

Next, the phase change film 460 of the optical path switching means 45A and 45B is heated by the same heating means as in the first embodiment.
Each of 8 is heated to a crystalline state and an amorphous state. Then, as shown in FIG. 10B, the light L1 input to the first input connector unit 41 is
It passes through the glass substrate 47 of the optical path switching means 45A and enters the multilayer film 46. The light L2 input to the second input connector unit 42 passes through the glass substrate 47 of the optical path switching unit 45B and enters the multilayer film 46. As shown in FIGS. 12 and 13, the reflectance in the amorphous state is 0.3%, the transmittance in the amorphous state is 21%, the reflectance in the crystalline state is 19.5%, and the transmittance in the crystalline state is 1.5%. %, The light L1 is reflected by the phase change film 4608, the light L2 passes through the phase change film 4608, and the first output connector unit 43 and the second output connector unit 44 respectively.
Be led to.

Therefore, when the phase change films of the optical path switching means 45A and 45B are in the amorphous state and the crystalline state, the optical switch 40 outputs the light L1 input to the first input connector section 41 to the second state. While being guided to the output connector section 44, the light L2 input to the second input connector section 22 is guided to the first output connector section 43 in the first switching state, and the optical path switching means 45A, 45B.
When the phase change film of (1) becomes a crystalline state and an amorphous state, respectively, the light L1 input to the first input connector section 41 is guided to the first output connector section 43 and input to the second input connector section 42. The second switching state is introduced in which the generated light L2 is guided to the second output connector section 44.
Therefore, even in the optical switch of the present embodiment, the first
A cross-connect type optical switch can be configured as in the above embodiment. Further, the optical switch of this embodiment can also achieve the same effects as those of the first embodiment.

Next, a sixth embodiment will be described. The sixth embodiment differs from the fifth embodiment in that the two lights input to the two input connector units are output to one output connector unit. That is, as shown in FIG. 14 (a), the optical switch 50 includes a first input connector section 51, a second input connector section 52 to which the ends of two optical fibers I1 and I2 are coupled, and an optical fiber. The first output connector section 53 and the second output connector section 54, to which the ends of O1 and O2 are coupled, and the light L1 input to the first input connector section 51, are output to the first and second outputs. An optical path switching unit 55A that switches and guides to the connector portions 53 and 54, and the light L2 input to the second input connector portion 52 is the first and second output connector portions 53 and 54.
And an optical path switching means 55B for switching and guiding the optical path.
The optical path switching means 55A and 55B are the same as the optical path switching means 45A and 45B in FIG.

Next, the operation of the optical switch according to the sixth embodiment having the above structure will be described. Figure 1
As shown in FIG. 4A, it is assumed that the light L1 is input from the optical fiber I1 to the first input connector unit 41 and the light L2 is input from the optical fiber I2 to the second input connector unit 42. Then, in the initial state, it is assumed that the phase change films of the multilayer films of the optical path switching means 55A and 55B are both in an amorphous state. The light L1 input to the first input connector unit 41 receives the light path switching unit 55.
Enter A. The light L2 input to the second input connector unit 42 enters the optical path switching unit 55B. As shown in FIGS. 12 and 13, since the reflectance in the amorphous state is 0.3% and the transmittance in the amorphous state is 21%, the lights L1 and L2 pass through the phase change film 4608,
It is guided to one second output connector section 44. That is, the two lights L1 and L2 are emitted from the second output connector section 44.
Are mixed and output.

Next, the phase change film 460 of the optical path switching means 55A and 55B is heated by the same heating means as in the first embodiment.
Both 8 are heated so as to be in a crystalline state. Then, as shown in FIG. 14B, the light L1 input to the first input connector unit 51 enters the optical path switching unit 55A.
The light L2 input to the second input connector unit 52 enters the optical path switching unit 55B. As shown in FIG. 12 and FIG. 13, since the reflectance in the crystalline state is 19.5% and the transmittance in the crystalline state is 1.5%, the lights L1 and L2 are reflected by the phase change film, respectively, Output connector section 43
Be led to. That is, a mixture of the two lights L1 and L2 is output from the first output connector unit 53.

Therefore, in the optical switch 50, when both the phase change films of the optical path switching means 55A and 55B are in the amorphous state, the light L1 input to the first input connector portion 51 and the second input connector portion are input. The first switching state is in which both the light L2 input to 52 is guided to the second output connector section 54. When the phase change films of the optical path switching means 55A and 55B are in a crystalline state, respectively, the light L1 input to the first input connector section 51 and the light L2 input to the second input connector section 52 are both changed to the first state. The second switching state is introduced to the first output connector section 53. Therefore, in the optical switch of the present embodiment, the light input to the two input connector units can be output from one output connector unit. Further, the optical switch of this embodiment can also achieve the same effects as those of the first embodiment.

Further, in order to realize the same function as that of the sixth embodiment, when the prism is moved as in the conventional case, a demultiplexer, a mixer, etc. are additionally required,
Its configuration becomes extremely complicated. On the contrary,
The sixth embodiment can be easily realized with an extremely simple structure, which is advantageous in comparison with the conventional art in this respect. In the fifth and sixth embodiments, since light is input only from one side of the multilayer film, it is not necessary to make the multilayer film structure symmetrical.

In the fifth and sixth embodiments as well, the above-mentioned heating means can be arbitrarily adopted. Also, the state of the refractive index of the phase change film can be monitored by measuring the capacitance of the phase change film that constitutes the optical path switching means, as in the above-described embodiment. Further, a plurality of optical switches can be arranged to form a multi-array optical switch, as in the above-described embodiment.

In each of the embodiments, Ge2Sb2Te5 is used as an example of the phase change material, but the optical switch and the method for driving the optical switch of the present invention are not limited to Ge2Sb2Te5 as the phase change material. However, since the transmittance and reflectance of the multilayer film can be optimally designed, the material of the phase change material is Ge2Sb2Te5.
Not limited to. Furthermore, in each of the embodiments, the wavelength of 1550 nm has been described as an example, but the applicable range of the wavelength in the optical switch of the present invention is not limited to the wavelength range of 1550 nm. It is also possible to use in the 1300 nm band by performing the optimum design for the 1300 nm band.

Further, in the above-described first to fifth embodiments, the first and second input connector sections have the first and second input connector sections and the first and second output connector sections. The optical switch of the cross-connect type has been described as an example, in which the light input to the unit is switched from the first and second output connector units and output, but the present invention is not limited to this.
The optical switch of the present invention has at least one first input connector section and first and second output connector sections, and switches the light input to the first input connector section from the output connector section to output the light. It is widely applicable to optical switches.

[0049]

As described above, according to the optical switch of the present invention, since the optical path is switched by the multilayer film of the optical path switching means, the switching time can be shortened.
In addition, it is possible to provide an optical switch that is easy to manufacture and low in cost. Further, according to the optical switch driving method of the present invention, the first and second multilayer films are formed based on the capacitance generated between the first and second conductive layers provided in the optical switch. Since the state of the refractive index in the multilayer film can be monitored by monitoring the state of, the reliability can be ensured by constantly monitoring the operating state of the optical switch.

[Brief description of drawings]

1A and 1B are explanatory diagrams showing a configuration of an optical switch according to a first embodiment.

FIG. 2 is a sectional view showing a configuration of an optical path switching unit.

FIG. 3 is a plan view of an optical path switching unit.

FIG. 4A is a characteristic diagram showing the measurement results of the refractive index when the wavelength is changed when the phase change material forming the phase change film is in an amorphous state, and FIG. 4B is the phase change. It is a characteristic diagram which shows the measurement result of the refractive index when changing the wavelength when the phase change material which comprises a film | membrane is in a crystalline state.

FIG. 5 is a characteristic diagram showing how the reflectance of the multilayer film changes with respect to the thickness of the phase change film.

FIG. 6 is a characteristic diagram showing how the transmittance of the multilayer film changes with respect to the thickness of the phase change film.

FIG. 7A is a waveform diagram of energy supplied from the current supply circuit to the phase change film when the phase change film is in an amorphous state, and FIG. 7B is a current supply circuit when the phase change film is in a crystalline state. It is a wave form diagram of the energy supplied from the to the phase change film.

FIG. 8 is a configuration diagram showing a configuration of heating means.

FIG. 9 is an explanatory diagram showing a configuration in which a plurality of optical switches are integrally provided.

10A and 10B are explanatory diagrams showing a configuration of an optical switch according to a fifth embodiment.

FIG. 11 is a cross-sectional view showing a configuration of an optical path switching unit.

FIG. 12 is a characteristic diagram showing how the reflectance of the multilayer film changes with respect to the thickness of the phase change film.

FIG. 13 is a characteristic diagram showing how the transmittance of the multilayer film changes with respect to the thickness of the phase change film.

14A and 14B are explanatory views showing the configuration of the optical switch according to the sixth embodiment.

15A and 15B are configuration diagrams showing a configuration of a conventional optical switch.

[Explanation of symbols]

20, 30, 40, 50 ... Optical switch, 21, 41,
51 ... First input connector section 22, 42, 52 ...
2nd input connector part, 23, 43, 53 ... 1st output connector part, 24, 44, 54 ... 2nd output connector part, 25, 45A, 45B, 55A, 55B ... Optical path switching means, 26, 46 ... Multilayer film, L1, L2 ... Light.

Claims (21)

[Claims] 1. A first input connector section for inputting light, first and second output connector sections for outputting light input to the first input connector section, and the first input. An optical switch comprising: an optical path switching unit that switches and guides light input to a connector unit to either one of the first and second output connector units, wherein the optical path switching unit is a first unit that transmits light. Has a multilayer film configured to be switchable between two states, a second state that reflects light and a second state that reflects light, and inputs from the first input connector unit when the multilayer film is in the first state. Light is transmitted through the multilayer film and guided to the first output connector unit, and is input from the first input connector unit when the multilayer film is in the second state. Light is reflected by the multilayer film and the second output connector is provided. The optical switch is characterized in that it is configured so as to be guided to a section. 2. The multilayer film has a first refractive index with high transmittance and low reflectance in the first state, and has a low transmittance and high reflectance in the second state. The optical switch according to claim 1, wherein the optical switch has a thin film configured to have a second refractive index. 3. The thin film is made of a phase change material that transitions between an amorphous state and a crystalline state, and the thin film has the first refractive index when in the amorphous state and when in the crystalline state. The optical switch according to claim 2, wherein the optical index has the second refractive index. 4. The optical path switching means includes heating means for heating the thin film, and the transition from the crystalline state to the amorphous state of the thin film is performed by the heating means heating the thin film to a first temperature. The transition from the amorphous state to the crystalline state of the thin film is performed by the heating means heating the thin film to a second temperature lower than the first temperature. The optical switch according to claim 3, wherein 5. The multilayer film includes the thin film and a heater layer formed on the thin film, the heater layer is configured to generate heat when supplied with an electric current, and the heating unit includes: The optical switch according to claim 4, wherein the optical switch is configured by the heater layer. 6. The optical switch according to claim 5, wherein the multilayer film is connected to a conductive portion made of a conductive material, and a current is supplied to the heater layer through the conductive portion. 7. The optical switch according to claim 4, wherein the heating of the thin film by the heating means is performed by irradiating the thin film with a heating light beam. 8. The heating light beam is composed of light generated by a light source different from the light input to the first input connector section and output from the first or second output connector section. 7. The method according to claim 7, wherein
Optical switch described. 9. The heating light beam is configured by light that is input to the first input connector section and is output from the first or second output connector section. Optical switch described. 10. The optical switch according to claim 2, wherein the multilayer film is configured to emphasize, that is, enhance, a change in the refractive index due to the thin film. 11. Electrostatic generated between the first and second conductive layers by providing first and second conductive layers made of a conductive material on both sides of the thin film in the thickness direction. The optical switch according to claim 2, wherein the capacity is measurable. 12. The first input connector section, the first output connector section, the second output connector section and the optical path switching means are provided in N units (N is a natural number of 2 or more), respectively, so that they are independent of each other. The optical switch according to claim 1, wherein the N optical switches are integrally configured, and the N optical path switching means are provided on a single substrate. 13. A first input connector section for inputting light, first and second output connector sections for outputting light input to the first input connector, and the first input connector. An optical path switching unit that guides the light input to the optical unit by switching to one of the first and second output connector units, the optical path switching unit reflecting the first state of transmitting light and the light. A multi-layer film configured to be switchable between two states, that is, a second state and a second state. When the multi-layer film is in the first state, the light input from the first input connector unit is Light input from the first input connector unit when the multilayer film is in the second state is transmitted through the multilayer film and is guided to the first output connector unit. Is reflected by and is guided to the second output connector section. The multilayer film has a first refractive index with high transmittance and low reflectance in the first state, and has a second refractive index with low transmittance and high reflectance in the second state. A method of driving an optical switch having a thin film configured to have a refractive index, wherein first and second conductive layers made of a conductive material are provided on both sides of the thin film in a thickness direction. The capacitance of the multilayer film is provided between the first and second conductive layers, and the capacitance of the multilayer film is measured based on the measured capacitance.
A method of driving an optical switch, comprising: monitoring a second state. 14. The method of driving an optical switch according to claim 13, wherein switching control of the multilayer film is performed based on a monitoring result of the first and second states of the multilayer film. 15. The optical switch according to claim 13, wherein it is determined whether or not the switching of the multilayer film is normally performed based on a monitoring result of the first and second states of the multilayer film. Driving method. 16. The thin film is made of a phase change material that transitions between an amorphous state and a crystalline state, and the thin film has the first refractive index when in the amorphous state and when in the crystalline state. The optical path switching means is configured to have the second refractive index, and the optical path switching means has heating means for heating the thin film. And a transition from an amorphous state to a crystalline state of the thin film is performed by the heating means heating the thin film to a second temperature lower than the first temperature. 14. The method for driving an optical switch according to claim 13, wherein the optical switch is configured as described above. 17. The method of driving an optical switch according to claim 16, wherein heating of the thin film by the heating means is controlled based on the monitoring results of the first and second states of the multilayer film. 18. The multilayer film includes the thin film and a heater layer formed on the thin film, and the heater layer is configured to generate heat when supplied with an electric current, and the heating unit includes: 18. The method of driving an optical switch according to claim 17, wherein the heating of the thin film constituted by the heater layer is controlled by controlling the amount of current supplied to the heater layer. 19. The heating of the thin film by the heating means is carried out by irradiating the thin film with a heating light beam, and the heating of the thin film by the heating means is controlled by the heating light beam irradiated onto the thin film. 18. The method of driving an optical switch according to claim 17, wherein the method is performed by controlling the amount of light. 20. The light beam for heating is composed of light generated by a light source different from the light input to the first input connector section and output from the first or second output connector section. 20. The method for driving an optical switch according to claim 19, further comprising: 21. The heating light beam is configured by light that is input to the first input connector section and output from the first or second output connector section. A method for driving the described optical switch.