JPH07181526A - Optical switch for parallel transmission - Google Patents

Abstract

PURPOSE:To provide an optical switch for parallel transmission which is excellent in switching characteristic, is miniaturized and performs high density transmission. CONSTITUTION:This optical switch is provided with a polarized light separating unit 12 consisting of a polarized light separating means 10 and an optical path converting means 11, a polarized light control element 13 switching the polarized state of P and S polarized light beams separated by the unit 12, a polarized light synthesizing unit 16 consisting of an optical path converting means 14 and a polarized light synthesizing means 15, an input means 17 making light incident on the unit 12 from the outside, and an output means 18 transmitting the light emitted from the unit 16 to the outside. The input and output means 17 and 18 are formed of lenses 19a, 19b, 22a and 22b and plural optical fibers 20 arranged in an array near an optical axis at a focusing position, and provided with an optical fiber connection batch switching means 24 switching the connecting state of the plural optical fibers 20 between the input and the output altogether by electrically controlling the polarized state of the control element 13 from the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to optical communication, optical information processing,
The present invention relates to an optical switch for parallel transmission used in fields such as optical interconnection.

[0002]

2. Description of the Related Art As a conventional optical switch mechanism,
For example, Japanese Unexamined Patent Application Publication No. 2-1000025 discloses a liquid crystal light changeover switch. This is, as shown in FIG. 6, a polarization splitting means comprising a polarization beam splitter 1 and a reflecting prism 2 and liquid crystals arranged at positions where P-polarized light and S-polarized light split by the polarization splitting means can respectively enter. A cell 3, a polarization beam splitter 4 for guiding the light passing through the liquid crystal cell 3, and a polarization prism 5, and optical fibers 6a and 6b and a rod lens 7 arranged on the side of the polarization beam splitter.
a, 7b, an optical fiber 8a, 8b and a rod lens 9a, which are arranged on the polarization combining means side.
9b and the output means.

In such a configuration, by electrically controlling the liquid crystal cell 3 from the outside, the polarization state (P-polarized light, S-polarized light) is controlled and the optical path is switched between the "bar state" and the "cross state". ing. The bar state here means a connection between the optical fiber 6a and the optical fiber 8a or a connection between the optical fiber 6b and the optical fiber 8b. Further, the cross state means a connection between the optical fiber 6a and the optical fiber 8b or a connection between the optical fiber 6b and the optical fiber 8a. Therefore, first, the operation in the bar state will be described. This bar state can be achieved by applying no voltage to the liquid crystal cell 3. That is, the optical signal from the optical fiber 6a is transmitted to the rod lens 7
The polarized film 1a passes through a and is divided into P-polarized light that transmits the polarized film and reflected S-polarized light. Of these, P-polarized light is
After being reflected by the reflection prism 2, it is converted into S-polarized light by passing through the liquid crystal cell 3 in the non-application state, reflected by the polarizing film 4a, passed through the rod lens 9a, and incident on the optical fiber 8a. Further, the S-polarized light which is divided by the polarizing film 1a and reflected is converted into P-polarized light through the liquid crystal cell 3 in the non-application state,
The light is reflected by the reflecting prism 5, passes through the polarizing film 4a, and enters the optical fiber 8a from the rod lens 9a. On the other hand, the optical signal from the optical fiber 6b passes through the rod lens 7b and is divided by the polarizing film 1a into P-polarized light transmitted therethrough and reflected S-polarized light. Of these, P-polarized light passes through the liquid crystal cell 3 in the non-applied state, is converted into S-polarized light, is reflected by the reflecting prism 5, and then is reflected by the polarizing film 4a to be reflected by the rod lens 9
It passes through b and enters the optical fiber 8b. In addition, the polarizing film 1
The S-polarized light divided by a and reflected by the reflecting prism 2 is converted into P-polarized light through the liquid crystal cell 3 in the non-application state, transmitted through the polarizing film 4a, and transmitted from the rod lens 9b to the optical fiber 8b. enter.

Next, the operation in the cross state will be described. This crossing state can be achieved by applying a voltage to the liquid crystal cell 3. That is, the optical signal from the optical fiber 6a is transmitted to the rod lens 7
The polarized film 1a passes through a and is divided into P-polarized light that transmits the polarized film and reflected S-polarized light. Of these, P-polarized light is
After being reflected by the reflection prism 2, the liquid crystal cell 3 in the applied state
Passing through the polarizing film 4a while remaining P-polarized, and enters the optical fiber 8b through the rod lens 9b. In addition, the S-polarized light that is separated and reflected by the polarizing film 1a is
After passing through the liquid crystal cell 3 in the applied state and being reflected by the reflecting prism 5 while being S-polarized, it is reflected by the polarizing film 4a and enters the optical fiber 8b from the rod lens 9b. On the other hand, the optical signal from the optical fiber 6b passes through the rod lens 7b and the polarizing film 1
At a, it is divided into P-polarized light that transmits the light and S-polarized light that reflects the light. Of these, the P-polarized light passes through the liquid crystal cell 3 in the applied state, is reflected by the reflection prism 5 as it is as P-polarized light, passes through the polarizing film 4a, passes through the rod lens 9a, and enters the optical fiber 8a. The S-polarized light separated by the polarizing film 1a is reflected by the reflecting prism 2, then passes through the liquid crystal cell 3 in the applied state, is reflected by the polarizing film 4a as it is, and is reflected by the rod lens 9a. Fiber 8
Enter a. Therefore, by electrically controlling the liquid crystal cell 3 from the outside in this way, it is possible to switch the optical path between the bar state and the cross state. In this case, in either case, the path length (optical path length) of the P and S polarized light from the input port (on the side of the optical fibers 6a and 6b) to the output port (on the side of the optical fibers 8a and 8b) in the optical switch passes. Therefore, the pulse width is not widened due to the shift of the optical pulse at the output port.

[0005]

In the above-mentioned conventional example, basically, one-to-one optical fiber switching (bar state, cross state) is performed. For example, the connection between the optical fiber 6a and the optical fiber 8a in the bar state is made by connecting the optical fiber 6a and the optical fiber 8a in the cross state.
The connection between the optical fiber 6b and the optical fiber 8b in the bar state is switched to the connection between the optical fiber 6b and the optical fiber 8b in the cross state. Therefore, by arranging a plurality of rod lenses and optical fibers in parallel in an array based on such a one-to-one optical fiber switching mechanism, switching of the plurality of optical fibers is performed at once. Then, the invention can be applied to a parallel switching mechanism that can switch simultaneously. However, in this case, simply arranging a plurality of optical fibers in an array causes deterioration of the optical coupling efficiency due to a phenomenon such as diffraction, and it is attempted to increase the beam diameter of the collimated light in order to suppress such deterioration. Then, there is a problem that the optical system of the input / output section becomes large. Moreover,
At present, there is no optical switch mechanism for parallel transmission capable of collectively switching between a plurality of optical fibers, which is realized by high coupling efficiency and high-density mounting.

[0006]

According to a first aspect of the present invention, there is provided polarization separating means for separating light into P-polarized light and S-polarized light, and optical path changing means for changing the optical paths of these separated P and S-polarized light. A polarization separation unit, a polarization control element for switching the polarization states of the P and S polarizations separated by the polarization separation unit, and an optical path conversion means for changing the optical paths of the P and S polarizations guided from the polarization control element. A polarization combining unit including a polarization combining unit that combines P and S polarized lights whose optical paths are changed, an input unit that allows light to enter the polarization separation unit from the outside, and a light emitted from the polarization combining unit to the outside. In an optical switch for parallel transmission equipped with output means for transmitting to each of the input means and the output means, each of the input means and the output means is arranged in an array in the vicinity of an optical axis of a focal position of the lens. Formed by a plurality of optical fibers arranged in a row, the polarization state of the polarization control element is electrically controlled from the outside to collectively switch the connection state of the plurality of optical fibers between the input and output. Means were provided.

According to a second aspect of the present invention, in the first aspect of the invention, the optical path lengths on the optical axes of P and S polarized light in the optical system from the polarization separation unit to the polarization combining unit are input / output. The sizes and arrangements of the optical components in the optical system were set so that they would be equal to or close to the total value of the focal lengths of the pair of lenses corresponding to each other.

According to a third aspect of the present invention, in the first aspect of the present invention, a polarization beam splitter is used as the polarization splitting means and the polarization synthesizing means, and the entrance surface and the exit surface of this polarization beam splitter are connected to the input / output means. It was arranged to be inclined with respect to the optical axis of each light.

According to a fourth aspect of the present invention, in the first aspect of the invention, a plurality of sets of input / output means each including a lens and a plurality of optical fibers are arranged in a one-dimensional or two-dimensional array.

According to a fifth aspect of the present invention, in the invention according to the fourth aspect, the element surface of the polarization control element is divided and formed in correspondence with the number of a pair of optical fiber arrays between the input and the output, and the plurality of them are formed. Element plane control means for individually controlling the polarization state of the divided element planes from the outside is provided.

[0011]

According to the first aspect of the invention, it is possible to collectively switch the connection states of the optical fibers arranged in a plurality of arrays with a compact optical system without deteriorating the optical coupling efficiency. .

According to the second aspect of the invention, since the optical path lengths of the P-polarized light and the S-polarized light are the same in the optical system in the optical switch, the pulse width of the optical signal on the input side is maintained as it is on the output side. As a result, even if a plurality of such optical switches are connected in series and used in multiple stages, the pulse width of the signal is not widened and a code error does not occur. It is possible to deal with processing sufficiently.

According to the third aspect of the present invention, the signal light from the input / output means is obliquely incident on the incident surface and the emission surface of the polarization beam splitter, so that the refraction at the incident interface is converted into an optical path. Since it is made to function as a means, an optical part as a substantial optical path changing means becomes unnecessary, and the number of parts can be reduced accordingly.

According to the invention described in claim 4, by arranging a plurality of sets of the input / output means in one dimension or two dimensions,
The light from the end of the optical fiber array does not enter and exit the end of the lens, and characteristics such as optical coupling efficiency are not deteriorated even when a large number of optical fibers are arranged. As a result, it becomes possible to realize a configuration capable of transmitting a large amount of signals with improved switching characteristics.

In the fifth aspect of the present invention, the polarization state of each element plane of the polarization control element is separately controlled, so that the plurality of parallel optical transmission lines can be switched individually, and the control range can be further expanded. It becomes possible.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the configuration of an optical switch module for parallel transmission. This module includes a polarization beam splitter 10 as a polarization separating means for separating light into P-polarized light and S-polarized light, and a reflection prism 11 as an optical path changing means for changing the optical paths of the separated P- and S-polarized light. The unit 12 and the polarization control element 1 for switching the polarization states of the P and S polarized lights separated by the polarization separation unit 12.
3, a reflection prism 14 as an optical path changing means for changing the optical paths of the P and S polarized light guided from the polarization control element 13, and a polarization beam splitter as a polarization combining means for combining the P and S polarized lights having the changed optical paths. A polarization synthesizing unit 16 composed of 15; an input means 17 for allowing light to enter the polarization splitting unit 12 from the outside; and a polarization synthesizing unit 1
And an output means 18 for transmitting the light emitted from 6 to the outside. In this case, the polarization control element 13 is composed of a liquid crystal cell of TN which can be driven with low power, and the alignment state of the liquid crystal cell is changed by electrical control from the outside.

In this embodiment, in such an optical switch module for parallel transmission, the input means 17 is composed of a single low-aberration lens 19a, 19b, and these lenses 1 are used.
An optical fiber array 2 including a plurality of optical fibers 20 arranged in an array near the optical axis of the focal positions of 9a and 19b.
1a and 21b, and the output means 18 is a single low-aberration lens 22a and 22b, and these lenses 2
An optical fiber array 2 including a plurality of optical fibers 20 arranged in an array near the optical axis of the focal positions of 2a and 22b.
3a and 23b. Furthermore, here, the polarization state of the polarization control element 13 is electrically controlled from the outside to collectively switch the connection state of the optical fiber arrays 21a, 21b, 23a, 23b consisting of a plurality of optical fibers 20 between the input and the output. A switching circuit 24 is provided as a means for collectively switching the optical fiber connections. The switching circuit 24 includes an AC power supply 25, a switch 26, and a control circuit (not shown).

The operation of this module having such a configuration will be described. Now, for example, the P and S polarized optical signals emitted from the optical fiber array 21a of the input means 17 are transmitted through the lens 19a to the polarization beam splitter 10.
Which is transmitted through the polarizing film 10a of P
The polarized light and the reflected S-polarized light are separated into two orthogonal components.
The P-polarized light goes straight to the polarization control element 13, and the S-polarized light is reflected by the reflection prism 11 to enter the polarization control element 13. In the polarization control element 13, when the electric field is not applied to the liquid crystal cell, each polarization plane is rotated by 90 ° and converted due to the twist of the alignment of the liquid crystal molecules, but when the electric field is applied, the polarization plane does not rotate and the polarization state is changed. Is saved as is.
Now, assuming that the polarization control element 13 here is at the time of applying an electric field, the P-polarized light that has entered the polarization control element 13 maintains its polarization state and goes straight on as it is, and is reflected by the reflection prism 14, and the polarization beam splitter 15 Polarizing film 15
a is transmitted. On the other hand, the S-polarized light reflected by the polarizing film 10a and reflected by the reflecting prism 11 passes through the polarization control element 13 to which an electric field is applied to maintain its polarization state, and is reflected by the polarizing film 15a of the polarizing beam splitter 15. It Then, the P-polarized light transmitted through the polarizing film 15a and the reflected S-polarized light are combined, condensed by the lens 22b as shown in FIG. 2, and correspond to the inverted image on the input side of the optical fiber array 23b. Each optical fiber 20
Be combined with. By setting the polarization control element 13 in the electric field applied state in this way, the P and S polarization states are maintained before and after the incidence, so that an optical signal is transmitted from the optical fiber array 21a to the optical fiber array 23b as shown in FIG. It is possible to achieve the "cross state". In addition to this, in order to achieve the "bar state" in which an optical signal is transmitted from the optical fiber array 21a to the optical fiber array 23a, the polarization control element 13 can be placed in a state in which no electric field is applied. Further, according to a principle similar to this, a cross state from the optical fiber array 21b to the optical fiber array 23a, or a cross state from the optical fiber array 21b to the optical fiber array 23a.
A bar state to b can be achieved. Therefore, as described above, by turning on / off the power supply 25 and controlling the rotation of the liquid crystal cell of the polarization control element 13, the optical fiber arrays 21a and 21b composed of the plurality of optical fibers 20 are provided.
And the optical fiber arrays 23a and 23b can be collectively switched with a compact optical system without deteriorating the optical coupling efficiency.
It is possible to provide an optical switch for parallel transmission, which can transmit a large amount of information at high speed, can be small-sized, and can be packaged with high reliability and high density.

The configuration of this embodiment can be designed to some extent in view of the switch size and the like, but it is equivalent in the optical system between the input and output including the polarization splitting unit 12 and the polarization combining unit 16. Input / output means 17, 1 so as to be equal to the optical system as shown in FIG.
The optical path length on the optical axis between the corresponding pair of lenses (for example, between the lens 19a and the lens 22b) in the input / output unit between the eight lens units is the total value of the focal lengths of the lenses (for example, the lens 19a
Since the same lens is used for the lens 22b and the lens 22b, it is desirable to design the lens 22b to have a value that is twice the focal length of the lens) or a value that is close to it. By designing in this way, it is possible to improve the optical coupling efficiency, extinction ratio, crosstalk, etc., and thereby it is possible to provide an optical switch for parallel transmission that is small and has excellent switching characteristics. Further, the focal lengths of the lenses 19a, 19b, 22a, 22b are preferably as long as possible without impairing the optical characteristics thereof, whereby the polarization control of the polarization signal obliquely incident on the liquid crystal cell of the polarization control element 13 can be controlled. It can be performed more efficiently.

Next, a second embodiment of the present invention will be described with reference to FIG. The description of the same parts as those in the first embodiment described above will be omitted, and the same reference numerals will be used for the same parts. The optical fiber array (optical fiber arrays 21a, 21b, 23a,
If the number of optical fibers 20 constituting 23b) is relatively small, a single lens (lens 19a, 19b, 22) is used.
a, 22b), but the optical fiber 2
If the number of 0's is further increased, the optical coupling efficiency of the light entering and exiting from the vicinity of both end portions of the lens with the single lens alone will increase the optical aberration of the lens. Therefore, there is a concern that the characteristics may deteriorate.
Therefore, in this embodiment, when the number of optical fibers 20 is large, the optical fibers 20 on the side of the input means 17 and the output means 18 are divided into some blocks and arranged in a one-dimensional or two-dimensional array. . Specifically, the optical fiber arrays 21a and 21b on the input side and the optical fiber arrays 23a and 23b on the output side are arranged separately for every two blocks.
Therefore, two lenses 19a, 19b, 22a, 22b are also arranged in each block, so that light from the vicinity of the end of the optical fiber array does not enter or exit from the end of the lens. As a result, characteristics such as optical coupling efficiency will not deteriorate due to optical aberration,
The switching characteristics can be improved and a large amount of signal transmission can be performed.

Further, in this embodiment, the polarization control element 1
3 element planes (not shown) are divided and formed corresponding to the number of a pair of optical fiber arrays (for example, the optical fiber array 21a and the optical fiber array 23a) between the input and output, and divided into a plurality of them. An element surface control means (not shown) for separately controlling the polarization state of the element surface from outside is provided. As a result, a large number of parallel transmission lines can be individually switched.

Next, a third embodiment of the present invention will be described with reference to FIG. The description of the same parts as those of the first and second embodiments described above will be omitted, and the same reference numerals will be used for the same parts. In this embodiment, the incident surfaces A and the exit surfaces B of the polarization beam splitters 10 and 15 used as the polarization splitting means and the polarization synthesizing means are tilted with respect to the optical axes of the respective lights from the input means 17 and the output means 18. It has been arranged. By obliquely inputting each light to the incident surface A and the exit surface B in this way, the refracting action at the interface can be used as an optical path changing function. This allows
Reflecting prisms 11 and 14 as substantial optical path changing means
Is unnecessary, the number of parts can be reduced accordingly, and a compact structure can be achieved.

Instead of using the TN liquid crystal cell as the polarization control element 13, other electric and magneto-optical elements such as a ferroelectric liquid crystal element, a PLZT element and a Faraday element can be used. Further, as the lens, not only a single convex lens but also a combination of a plurality of lenses or an aspherical lens may be used.

[0024]

According to the invention described in claim 1, the light is P-polarized light and S-light.
A polarized light separating means for separating the polarized light and the separated P,
A polarization separation unit including an optical path changing means for changing the optical path of S-polarized light, a polarization control element for switching the polarization states of the P and S polarizations separated by the polarization separation unit, and the P derived from the polarization control element. , S polarization changing means for changing the optical paths of the S and S polarizations, and a polarization synthesizing unit for synthesizing the P and S polarizations having the changed light paths, and an input means for making light incident from the outside into the polarization separating unit. A parallel transmission optical switch including output means for transmitting the light emitted from the polarization combining unit to the outside, wherein each of the input means and the output means is provided with a lens and an optical axis near a focal position of the lens. It is formed by a plurality of optical fibers arranged in an array, and the polarization state of the polarization control element is electrically controlled from the outside to control the plurality of light beams between the input and output. Since the optical fiber connection batch switching means for collectively switching the fiber connection status is provided, the connection status of the optical fibers arranged in a plurality of arrays can be collectively controlled by a compact optical system without deteriorating the optical coupling efficiency. Thus, it is possible to provide a parallel transmission optical switch that can be switched by means of a switch and thereby can transmit small-sized and high-density information.

According to a second aspect of the present invention, in the first aspect of the invention, the optical path lengths on the optical axes of P and S polarized light in the optical system from the polarization separation unit to the polarization combining unit are input / output. Since the size and the arrangement of each optical component in the optical system are set so as to be equal to or close to the total value of the focal lengths of the pair of lenses corresponding to each other, the optical system in the optical switch. Since the P-polarized light and the S-polarized light have the same optical path length, the pulse width of the optical signal on the input side is sent as it is on the output side, which allows a plurality of such optical switches to be transmitted. Even when they are connected in series and connected in multiple stages, the pulse width of the signal is not widened and a code error does not occur.
It is possible to provide a configuration that can sufficiently support high-speed processing with excellent switching characteristics.

According to a third aspect of the present invention, in the first aspect of the present invention, a polarization beam splitter is used as the polarization splitting means and the polarization synthesizing means, and the entrance surface and the exit surface of this polarization beam splitter are connected to the input / output means. Since it is arranged so as to be inclined with respect to the optical axis of each light, it is possible to cause the refracting action at the incident interface to function as an optical path converting means,
As a result, an optical component as a substantial optical path changing means is not required, and a compact structure with a reduced number of components can be realized.

According to a fourth aspect of the present invention, in the first aspect of the invention, there is provided an input / output device comprising a lens and a plurality of optical fibers.
Since a plurality of sets of output means are arranged in a one-dimensional or two-dimensional array, light from the end of the optical fiber array does not enter or exit the end of the lens, and a large number of optical fibers are arranged. Even in such a case, characteristics such as optical coupling efficiency are not deteriorated, whereby the switching characteristics can be improved and a much larger amount of signal transmission can be processed at high speed.

According to a fifth aspect of the present invention, in the invention according to the fourth aspect, the element surface of the polarization control element is divided and formed corresponding to the number of a pair of optical fiber arrays between the input and the output, and the plurality of them are formed. Since the element plane control means for separately controlling the polarization state of the divided element planes from the outside is provided, a plurality of parallel optical transmission lines can be individually switched and the control range can be further expanded. .

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an optical switch for parallel transmission which is a first embodiment of the present invention.

FIG. 2 is an optical path diagram showing a changed state of an optical path between a pair of lenses.

FIG. 3 is a schematic view showing a bar and a cross state.

FIG. 4 is a configuration diagram showing a configuration of an optical switch for parallel transmission that is a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a configuration of a parallel transmission optical switch according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram showing a conventional optical switch mechanism.

[Explanation of symbols]

10 Polarization Separation Means 11 Optical Path Conversion Means 12 Polarization Separation Unit 13 Polarization Control Element 14 Optical Path Conversion Means 15 Polarization Synthesis Means 16 Polarization Synthesis Unit 17 Input Means 18 Output Means 19a, 19b Lens 20 Optical Fiber 22a, 22b Lens 24 Optical Fiber Connection Collective Switching means

Claims (5)

[Claims] 1. A polarization separation unit comprising a polarization separation means for separating light into P-polarized light and S-polarized light, and an optical path conversion means for changing the optical paths of these separated P and S-polarized light, and a polarization separation unit for separating the light. A polarization control element for switching the polarization states of the P and S polarizations, an optical path conversion means for changing the optical paths of the P and S polarizations introduced from the polarization control element, and the P and S polarizations of which the optical paths are changed are combined. For parallel transmission, which includes a polarization combining unit including polarization combining means, input means for allowing light to enter the polarization separation unit from the outside, and output means for transmitting light emitted from the polarization combining unit to the outside. In the optical switch, each of the input means and the output means is formed by a lens and a plurality of optical fibers arranged in an array near the optical axis of the focal position of the lens. Parallel transmission characterized in that an optical fiber connection collective switching means for collectively controlling the polarization state of the polarization control element from the outside to collectively switch the connection state of the plurality of optical fibers between the input and output is provided. Optical switch. 2. The total value of the focal lengths of a pair of lenses whose optical path lengths on the optical axes of P and S polarized light in the optical system from the polarization separation unit to the polarization combining unit correspond between the input and output means. 2. The optical switch for parallel transmission according to claim 1, wherein the size and the arrangement of each optical component in the optical system are set so as to be a value equal to or nearly equal to. 3. A polarization beam splitter is used as the polarization splitting means and the polarization synthesizing means, and the incident surface and the exit surface of this polarization beam splitter are arranged to be inclined with respect to the optical axis of each light from the input / output means. The optical switch for parallel transmission according to claim 1, wherein: 4. An optical switch for parallel transmission according to claim 1, wherein a plurality of sets of input / output means composed of a lens and a plurality of optical fibers are arranged in a one-dimensional or two-dimensional array. 5. A polarization control element is formed by dividing the element surface corresponding to the number of a pair of optical fiber arrays between input and output, and the polarization states of the element surfaces divided into a plurality of parts are separately and externally provided. 5. An optical switch for parallel transmission according to claim 4, further comprising element surface control means for controlling switching.