JP3566086B2 - Optical switch array and optical add / drop multiplexer using the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical switch array and an improvement of an optical add / drop multiplexer using the same.
[0002]
[Prior art]
2. Description of the Related Art In order to cope with multimedia communication that is spreading rapidly, the capacity of a network has been increased by using light. Networks using optical wavelength division multiplexing (WDM) technology have attracted attention as a technology that enables not only a significant increase in transmission capacity but also opticalization of the entire network including node functions such as cross connect and switching. However, realizing this WDM type network requires a large amount of small optical add / drop multiplexers with low crosstalk.
[0003]
The optical add / drop multiplexer is composed of two optical elements, a wavelength multiplexer / demultiplexer and a spatial optical switch array. Its function is to separate the light of a certain wavelength band, which is transmitted in an optical fiber, spatially by wavelength multiplexer / demultiplexer for each wavelength, and then select only the light of the desired wavelength by a spatial optical switch array. In other words, the extracted light having an arbitrary wavelength is multiplexed by a wavelength multiplexer / demultiplexer and returned to the optical fiber.
[0004]
Conventionally, when manufacturing an optical add / drop multiplexer, an AWG (array waveguide diffraction grating) is used as a wavelength multiplexer / demultiplexer, and a Mach-Zehnder type 2 × 2TO (thermo-optic effect) switch is used as a spatial optical switch array. It was common to use a plurality of them arranged in parallel.
[0005]
In fact, an optically integrated 16-channel AWG add / drop multiplexer has been proposed in which two types of components, two sets of AWGs and a Mach-Zehnder 2 × 2TO switch, are optically integrated on the same optical waveguide substrate (K. Okamoto, K. Takaguchi and Y. Ohmori, "16-channel optical add / drop multiplexer using silica-based arrayed-waveguide grating", see Electron, Vol.
[0006]
[Problems to be solved by the invention]
However, the above-described conventional optical add / drop multiplexer has some problems in terms of crosstalk and size when modularized.
[0007]
First, since the crosstalk of the Mach-Zehnder 2 × 2TO switch itself is about −30 dB, even if an optical add / drop multiplexer is manufactured using the Mach-Zehnder 2 × 2TO switch, the crosstalk is only about −30 dB. Does not have a sufficiently low value. For this reason, crosstalk and the like in optical communication may occur.
[0008]
Next, in the Mach-Zehnder TO switch, the switches are switched using the phase difference change of the propagating light due to the thermo-optic effect. Therefore, when the distance between the switches is reduced, the heat of one switch also affects the other switch. And worsens the crosstalk of the other switch. From the viewpoint of avoiding this phenomenon, the distance between the switches cannot be easily reduced, so that there is a problem that the size of the optical switch array itself and the optical add / drop multiplexer using the same are inevitably increased. .
[0009]
An object of the present invention is to solve the above problems and provide a small and inexpensive optical switch array having a crosstalk value of −40 dB or less which is sufficient for optical communication, and an optical add / drop multiplexer using the same. is there.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the present invention, a first optical waveguide group including n (n is a natural number) optical waveguides each having a parallel optical axis, and n optical waveguides each having a parallel optical axis The second optical waveguide group consisting of is arranged such that the respective optical waveguides intersect each other, of the intersections between each optical waveguide of the first optical waveguide group and each optical waveguide of the second optical waveguide group, An optical switch provided with a switch unit capable of directly outputting light from the optical waveguides of the first optical waveguide group or switching and outputting the light from the optical waveguides of the first optical waveguide group to the optical waveguides of the second optical waveguide group only at diagonal intersections of the entire intersection. Suggest an array.
[0011]
According to the above configuration, a large angle (intersection angle) between the optical axis of each optical waveguide of the first optical waveguide group and the optical axis of each optical waveguide of the second optical waveguide group can be taken. A crosstalk value of −40 dB or less sufficient for communication can be obtained, and an intersection where light output from the first optical waveguide group is switched to the second optical waveguide group and passed through is output. Are the same in each optical waveguide, and the loss is the same . Further, since the thermo-optic effect is not used unlike the Mach-Zehnder TO switch, there is no restriction that the distance between the switch units cannot be easily reduced, and the size can be easily reduced.
[0013]
Then, the optical switch array and the array waveguide grating are integrated on the same substrate, and each input port of the optical switch array and each output port of the array waveguide grating are directly connected by the optical waveguide. If combined, a small and inexpensive optical add / drop multiplexer having a crosstalk value of −40 dB or less sufficient for optical communication can be realized.
[0014]
The switch unit of the optical switch array described above includes, for example, a slit (groove) having a wall surface that reflects light from the optical waveguides of the first optical waveguide group to the optical waveguides of the second optical waveguide group, And a refractive index matching liquid that is filled and removed in an appropriate amount in the central portion in the longitudinal direction.
[0015]
At this time, when the refractive index matching liquid is filled in the center of the slit in the longitudinal direction, the light passes through the slit, and when the refractive index matching liquid is removed, the light is totally reflected on the wall surface of the slit. And switch the optical path. The filling and removal of the refractive index matching liquid necessary for the optical path switching is performed, for example, by providing thin film heaters near the center (lower part) in the longitudinal direction and near both ends of the sealed slit. When only the heater is removed and only the heater near the center is heated, the vapor pressure in the slit is partially changed to move the refractive index matching liquid.
[0016]
In the configuration of the switch unit, the optical path switching is performed by filling and removing an appropriate amount of the refractive index matching liquid at the center in the longitudinal direction of the slit, but if the optical path can be switched by the slit, the refractive index matching liquid is used. However, the present invention is not limited to this. For example, a reflection mirror may be provided at the center in the longitudinal direction of the slit filled with the refractive index matching liquid. Further, mercury may be injected into a central portion in the longitudinal direction of the slit filled with the electrolyte solution having the refractive index of the core of the optical waveguide.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an outline of an optical switch array according to the present invention. In the figure, reference numeral 1 denotes a first optical waveguide group, 2 denotes a second optical waveguide group, and 3 denotes a switch unit.
[0018]
The first optical waveguide group 1 is composed of n (n is a natural number), here, three optical waveguides 11, 12, and 13 each having a parallel optical axis. It is composed of n (n is a natural number), here, three optical waveguides 21, 22, 23 each having a parallel optical axis, and these optical waveguides 11, 12, 13, and 21, 22, 23 are substantially orthogonal to each other. The 3 × 3 matrix-shaped optical waveguides are formed on the optical waveguide substrate 4 so as to intersect with each other.
[0019]
The switch unit 3 reflects light from the input side (hereinafter, A side) of the optical waveguide of the first optical waveguide group 1 to the output side (hereinafter, D side) of the optical waveguide of the second optical waveguide group 2. A slit (groove) 31 having a wall surface, and a refractive index matching liquid 32 filled and removed in an appropriate amount in a central portion of the slit 31 in the longitudinal direction, from the side A when the refractive index matching liquid 32 is filled. Of the first optical waveguide group 1 goes straight to the output side (hereinafter, referred to as B side) of the optical waveguide of the first optical waveguide group 1 , and when removed, the light from the A side is output to the D side.
[0020]
The switch section 3 is a cross section of the optical waveguides 11, 12, and 13 of the first optical waveguide group 1 and the optical waveguides 21, 22, and 23 of the second optical waveguide group 2, and uniquely corresponds to the optical waveguide. Here, they are provided only at the intersections of the optical waveguides 11 and 22, 12 and 23, and 13 and 21 here.
[0021]
The optical switch array shown in FIG. 1 operates normally as a double pseudo 2 × 2 optical switch having a low crosstalk value sufficient for optical communication as described below.
[0022]
In other words, when the light transmitting (through) state is referred to as OFF and the reflection switching (cross) state is referred to as ON, the input from the A side of the first optical waveguide group 1 when all the switch units 3 are OFF. The light propagates directly to the B side of the first optical waveguide group 1 and does not propagate to the D side of the second optical waveguide group 2. The crosstalk value at this time is -40 dB or less. Further, when all the switch sections 3 are off, the input light from the input side (hereinafter, C side) of the optical waveguide of the second optical waveguide group 2 is directly propagated to the D side of the second optical waveguide group 2. You.
[0023]
When all the switch units 3 are on, the input light from the A side of the first optical waveguide group 1 is propagated to the D side of the second optical waveguide group 2 by reflection at the switch unit 3, The light is not propagated to the B side of the first optical waveguide group 1. The crosstalk value at this time is also -40 dB or less. When all the switch units 3 are turned on, the input light from the C side of the second optical waveguide group 2 is not propagated to the D side of the second optical waveguide group 2.
[0024]
That is, one unnecessary reflection switching (cross) function is eliminated in the optical add / drop multiplexer. In this sense, it can be said that the optical switch array in FIG. 1 is a triple pseudo 2 × 2 optical switch array.
[0025]
In the case of manufacturing an optical add / drop multiplexer using the optical switch array of the present invention, the optical switch array and the array waveguide diffraction grating (AWG) are integrated on the same substrate, and each input terminal of the optical switch array is integrated. Since the port and each output terminal port of the AWG are directly coupled by the optical waveguide, it is possible to maintain a value of −40 dB or less equivalent to the switch characteristic in crosstalk.
[0026]
When the optical switch array shown in FIG. 1 is actually assembled, the overall size is about 1 mm × 1 mm. This size is significantly smaller than the size of a conventional 2 × 2 optical switch array manufactured by arranging two conventional Mach-Zehnder type 2 × 2 TO switches in parallel, that is, one-tenth of the mounting area. Therefore, it can be said that the optical switch array of the present invention is more suitable for a large-scale (multiple-unit) optical switch array manufactured using a Mach-Zehnder TO switch.
[0027]
Furthermore, since the optical switch array itself of the present invention is extremely small, the size of the optical add / drop multiplexer can be significantly reduced when the optical switch array is manufactured using this optical switch array.
[0028]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0029]
[Embodiment 1]
FIG. 2 shows an example of an embodiment of the optical switch array of the present invention.
[0030]
Here, a first optical waveguide group 51 composed of eight optical waveguides each having a parallel optical axis and a second optical waveguide group composed of eight optical waveguides each having a parallel optical axis are provided on an optical waveguide substrate 50. The waveguide group 52 is arranged and formed such that the respective optical waveguides cross each other at substantially right angles, and furthermore, the intersection between each optical waveguide of the first optical waveguide group 51 and each optical waveguide of the second optical waveguide group 52. Of the sections, the diagonal line of the entire intersection is the same so that the number of intersections through which the light switched from the first optical waveguide group 51 to the second optical waveguide group 52 passes is the same in each optical waveguide. The switch section 53 (SW (a) to (h)) is provided only at the eight intersections.
[0031]
The configuration of each switch unit 53 is the same as that of FIG. 1 and includes a slit and a refractive index matching liquid that is filled and removed in an appropriate amount in the center in the longitudinal direction of the slit. As described above, the removal is performed by heating one of the heaters provided near the center (lower portion) and near both ends in the longitudinal direction of the slit and moving the refractive index matching liquid in the slit. . An optical fiber 54 for inputting and outputting light is connected to each optical waveguide.
[0032]
First, in the switch behavior of the 8-unit pseudo 2 × 2 optical switch array shown in FIG. 2, it was confirmed that the switch operates normally as a low crosstalk pseudo 2 × 2 optical switch sufficient for optical communication as described below. did.
[0033]
If the light transmitting (through) state is referred to as “off” and the reflection switching (cross) state is referred to as “on”, the input light from the A side propagates directly to the B side output port when all the switch units 53 are off. And is not propagated to the D-side output port. The crosstalk value at this time is -40 dB or less. When all the switches 53 are off, the input light from the C side is propagated to the D side output port.
[0034]
When any one of the switch units 54 is turned on, the light from the A-side optical waveguide corresponding to the turned-on switch unit is propagated to the D-side optical waveguide and is not propagated to the B-side. The crosstalk value at this time is -40 dB or less. At this time, light from the optical waveguide on the C side is not propagated to the D side.
[0035]
According to the present embodiment, it can be said that the pseudo 2 × 2 optical switch array of the present invention can significantly reduce the crosstalk as compared with the conventional Mach-Zehnder 2 × 2 TO switch.
[0036]
Second, when the eight-unit pseudo 2 × 2 optical switch array of FIG. 2 is actually assembled, the entire size is about 3 mm × 3 mm, and eight conventional Mach-Zehnder type 2 × 2 TO switches are arranged in parallel. As compared with the size of the 8-unit 2.times.2 optical switch array, the mounting area is remarkably reduced to about one tenth. Therefore, it can be said that the optical switch array of the present invention is more suitable for increasing the scale (multiple units) than the Mach-Zehnder TO switch.
[0037]
Third, in the 8-series pseudo 2 × 2 optical switch array shown in FIG. 2, the diagonal direction is set so that the number of intersections passing when the light travels from the optical waveguide on the A side to the optical waveguide on the D side is the same. Since the switch section (slit) is provided at the intersection of only the output ports, there is no variation in the loss between the output ports, and the loss always takes a constant value. Therefore, it can be said that the multiple pseudo 2 × 2 optical switch array of the present invention has remarkably advantageous characteristics when coupled to another optical element such as AWG.
[0038]
[Embodiment 2]
FIG. 3 shows an example of an embodiment of an optical add / drop multiplexer according to the present invention. In this case, an optical integrated type 16 channel in which a 16-unit pseudo 2 × 2 optical switch array and an arrayed waveguide grating (AWG) are integrated on the same substrate. 3 illustrates an AWG add / drop multiplexer.
[0039]
That is, in FIG. 3, 60 is an optical waveguide substrate, 61 and 62 are arrayed waveguide diffraction gratings (AWG) corresponding to the add operation, and 63 and 64 are arrayed waveguide diffraction gratings (AWG) corresponding to the drop operation. , Between the AWG 61 and the AWG 63 and between the AWG 62 and the AWG 64, the number of optical waveguides constituting the first and second optical waveguide groups in the eight-unit pseudo 2 × 2 optical switch array shown in FIG. A 16-series pseudo 2 × 2 optical switch array 65 is disposed. By switching the 16-series pseudo 2 × 2 optical switch array 65, a signal of a desired wavelength is added and dropped from 16 channels as described below. I am trying to do it.
[0040]
That is, when the 16-unit pseudo 2 × 2 optical switch array 65 is on (cross), the 16-wavelength signal input from the main input port is first split by the AWG 62 and the 16-unit pseudo 2 × 2 optical switch 65 The signals are multiplexed again by the AWG 63 through the cross port and output to the main output port. Next, when the 16-unit pseudo 2 × 2 optical switch array 65 is turned off (through), each wavelength signal demultiplexed by the AWG 62 is transmitted through the corresponding through-port of the 16-unit pseudo 2 × 2 optical switch array 65. The signals are multiplexed by the AWG 64 through the ports, and are output collectively from the drop port.
[0041]
The size of the optical integrated type 16-channel AWG add / drop multiplexer of the present invention is about 5 mm × 5 mm except for the AWG portion, and the optical integrated type 16-channel AWG constructed using the conventional Mach-Zehnder type 2 × 2 TO switch. The mounting area can be remarkably reduced to one-tenth of the size of the add / drop multiplexer excluding the AWG portion.
[0042]
【The invention's effect】
As described above, according to the present invention, an optical switch array with sufficiently low crosstalk and a small size can be formed, and an optical add / drop multiplexer manufactured using this optical switch array can also have a low crosstalk. And a highly integrated module, that is, a small-sized and inexpensive module that can be configured in a user optical network such as FTTD (fiber to the desk) or optical LAN (local area network) and in a communication processing apparatus. It can be used effectively for optical interconnection.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an outline of an optical switch array of the present invention; FIG. 2 is a configuration diagram showing an example of an embodiment of an optical switch array of the present invention; FIG. 3 is an embodiment of an optical add / drop multiplexer of the present invention; Configuration diagram showing an example of the form [Description of reference numerals]
1, 51: first optical waveguide group, 2, 52: second optical waveguide group, 3, 53: switch unit, 4, 50, 60: optical waveguide substrate, 11 to 13, 21 to 23: optical waveguide, 31: slit (groove), 32: refractive index matching liquid, 61 to 64: arrayed waveguide diffraction grating (AWG), 65: 16 quasi 2 × 2 optical switch array.

Claims (4)

A first optical waveguide group consisting of n (n is a natural number) optical waveguides each having a parallel optical axis, and a second optical waveguide group consisting of n optical waveguides each having a parallel optical axis, Are arranged so that the optical waveguides intersect each other,
Of the intersections between each optical waveguide of the first optical waveguide group and each optical waveguide of the second optical waveguide group, only the diagonal intersection of the entire intersection is
An optical switch array, comprising: a switch portion that allows light from the optical waveguides of the first optical waveguide group to travel straight as it is or outputs the light to the optical waveguides of the second optical waveguide group. The optical switch array according to claim 1 and an arrayed waveguide grating are integrated on the same substrate, and each input port of the optical switch array and each output port of the arrayed waveguide grating are optical waveguides. An optical add / drop multiplexer which is directly coupled. In the middle of an optical waveguide connecting between the first and second arrayed waveguide gratings and between the third and fourth arrayed waveguide gratings ,
A first optical waveguide group consisting of n (n is a natural number) optical waveguides each having a parallel optical axis, and a second optical waveguide group consisting of n optical waveguides each having a parallel optical axis, Of the intersections between the respective optical waveguides of the first optical waveguide group and the respective optical waveguides of the second optical waveguide group, only the intersections between the optical waveguides uniquely corresponding to each other are arranged so that the optical waveguides of the first optical waveguide group intersect with each other. An optical switch array provided with a switch unit that can directly output light from the optical waveguides of the first optical waveguide group or switch to the optical waveguides of the second optical waveguide group and output the same,
Each optical waveguide of the first optical waveguide group forms a part of the optical waveguide that connects the first array waveguide diffraction grating and the second array waveguide diffraction grating, and the second optical waveguide group An optical add / drop multiplexer, wherein each optical waveguide forms a part of the optical waveguide connecting the third array waveguide diffraction grating and the fourth array waveguide diffraction grating . In the middle of an optical waveguide connecting between the first and second arrayed waveguide gratings and between the third and fourth arrayed waveguide gratings ,
A first optical waveguide group consisting of n (n is a natural number) optical waveguides each having a parallel optical axis, and a second optical waveguide group consisting of n optical waveguides each having a parallel optical axis, Are arranged so that the optical waveguides of the first optical waveguide group intersect with each other. An optical switch array provided with a switch unit that can directly output light from the optical waveguides of the first optical waveguide group or switch to the optical waveguides of the second optical waveguide group and output the light,
Each optical waveguide of the first optical waveguide group forms a part of the optical waveguide that connects the first array waveguide diffraction grating and the second array waveguide diffraction grating, and the second optical waveguide group An optical add / drop multiplexer, wherein each optical waveguide forms a part of the optical waveguide connecting the third array waveguide diffraction grating and the fourth array waveguide diffraction grating .

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