JP2000032510A - Optical switch array and optical add/drop multiplexer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and small-sized optical switch array with crosstalk value of -40 dB or below which is sufficient for optical communication and to provided the optical add/drop multiplexer using it. SOLUTION: First and second optical waveguide groups respectively consisting of 16 optical guide paths are placed on the way of optical guide paths tying AWGs(array waveguide diffraction grating) 61, 62 corresponding to the add operation and AWGs 63, 64 corresponding to the drop operation, so that the optical waveguides cross each other in this optical switch array and a 16 pseudo 2×2 optical switch array 65, consisting of switches that direct a light from the 1st optical waveguide group as it is or switches the light to a 2nd optical guide path group is placed only to the crossing on a diagonal line of the entire crossings and add/drop applied to a signal with a desired wavelength is conducted by switching of the optical switch array 65.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical switch array and an optical add / drop multiplexer using the same.

[0002]

2. Description of the Related Art In order to cope with multimedia communication which 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 not only enables a significant increase in transmission capacity but also enables the 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.

An optical add / drop multiplexer is composed of two optical elements, a wavelength multiplexer / demultiplexer and a spatial optical switch array. Its function is to transmit in optical fiber,
After light of a certain wavelength band is spatially separated for each wavelength by a wavelength multiplexer / demultiplexer, only light of a desired wavelength is selectively extracted by a spatial light switch array, or conversely, any extracted light is extracted. Light of a wavelength is multiplexed by a wavelength multiplexer / demultiplexer and returned into an optical fiber.

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 2 × 2TO (thermo-optical effect) is used as a spatial optical switch array. It was common to use a plurality of switches arranged in parallel.

In fact, two sets of AWG and Mach-Zehnder type 2
An optical integrated 16-channel AWG add / drop multiplexer in which two types of components of a × 2TO switch are optically integrated on the same optical waveguide substrate has been proposed (K. Ok).
amoto, K .; Takeguchi and Y. O
hmori, "16-channel optical
add / drop multiplexer usi
ng silca-based arrayed-wa
vegide grating ”, Electron
Lett. , Vol. 31, No. 9, pp. 723
-724, 1995).

[0006]

However, the above-mentioned conventional optical add / drop multiplexer has some problems in terms of crosstalk and size when modularized.

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 about −30 dB. And does not have a sufficiently low value. For this reason, crosstalk and the like in optical communication may occur.

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 is transferred to the other switch. Also have an effect and exacerbate 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. .

An object of the present invention is to solve the above-mentioned problems and to 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 to do.

[0010]

According to the present invention, there is provided a first optical waveguide group including n (n is a natural number) optical waveguides each having a parallel optical axis. A second optical waveguide group consisting of n optical waveguides having an optical axis is arranged such that the respective optical waveguides cross each other, and each optical waveguide of the first optical waveguide group and each of the second optical waveguide group are arranged. Of the intersections with the optical waveguides, the light from the optical waveguides of the first optical waveguide group goes straight to the optical waveguides of the second optical waveguide group only at the intersections of the uniquely corresponding optical waveguides, or is switched to the optical waveguide of the second optical waveguide group. We propose an optical switch array with a switch that can output.

According to the above configuration, the 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 made large. Therefore, it is possible to obtain a crosstalk value of −40 dB or less, which is sufficient for optical communication. Further, since the thermo-optic effect is not used unlike the Mach-Zehnder type TO switch, there is no restriction that the distance between the switch units cannot be easily reduced, and the size can be easily reduced.

At this time, among the intersections between the respective optical waveguides of the first optical waveguide group and the respective optical waveguides of the second optical waveguide group, a switch portion is provided only at a diagonal intersection of the entire intersection. For example, the number of intersections through which light that is switched from the optical waveguides of the first optical waveguide group to the optical waveguides of the second optical waveguide group passes is the same in each optical waveguide, and the loss is the same.

The optical switch array and the 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 optically guided. By directly coupling in a wave path, a small and inexpensive optical add / drop multiplexer having a crosstalk value of −40 dB or less sufficient for optical communication can be realized.

The switch section of the above-described optical switch array includes, for example, a slit (groove) having a wall surface for reflecting 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 of the slit.

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 passes through the wall of the slit. The light is totally reflected and switches 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.

In the configuration of the switch section, the optical path is switched by filling and removing an appropriate amount of the refractive index matching liquid in the central portion in the longitudinal direction of the slit. It is not limited to the rate matching liquid. 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. Also, mercury may be injected into the longitudinal center of the slit filled with the electrolyte solution having the refractive index of the core of the optical waveguide.

[0017]

FIG. 1 shows an outline of an optical switch array according to the present invention. In FIG. 1, reference numeral 1 denotes a first optical waveguide group,
Denotes a second optical waveguide group, and 3 denotes a switch unit.

The first optical waveguide group 1 is composed of n (n is a natural number), here three optical waveguides 1 each having a parallel optical axis.
1, 12, 13 and the second optical waveguide group 2
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 mutually connected. The 3 × 3 matrix optical waveguides are formed on the optical waveguide substrate 4 so as to intersect substantially orthogonally.

The switch section 3 converts 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 that reflects light to the right side, and a refractive index matching liquid 32 filled and removed in an appropriate amount at the center of the slit 31 in the longitudinal direction. The light from the A side is made to go straight to the output side (hereinafter, referred to as B side) of the optical waveguide of the second optical waveguide group 2, and when removed, the light from the A side is output to the D side. .

The switch section 3 includes the first optical waveguide group 1
Among the optical waveguides 11, 12, and 13 and the optical waveguides 21, 22, and 23 of the second optical waveguide group 2, uniquely corresponding optical waveguides, here, the optical waveguides 11, 22, and 12
And 23, 13 and 21 are provided only at the intersections.

The optical switch array shown in FIG. 1 normally operates as a double pseudo 2.times.2 optical switch having a low crosstalk value sufficient for optical communication as described below.

That is, when a state in which light is transmitted (through) is referred to as “off” and a reflection switching (cross) state is referred to as “on”, when all the switches 3 are off, the A side of the first optical waveguide group 1 is turned off. From the first optical waveguide group 1 is propagated to the B side of the first optical waveguide group 1 as it is, and is not propagated to the D side of the second optical waveguide group 2. The crosstalk value at this time is -40 dB or less. When all the switch sections 3 are turned 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.

When all the switches 3 are turned on, the input light from the side A of the first optical waveguide group 1 is
Is propagated to the D side of the second optical waveguide group 2 and 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 switches 3 are turned on, the C of the second optical waveguide group 2
The input light from the side is not propagated to the D side of the second optical waveguide group 2.

That is, one unnecessary reflection switching (cross) function is eliminated from 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.

When an optical add / drop multiplexer is manufactured using the optical switch array of the present invention, the optical switch array and the arrayed waveguide grating (AWG) are integrated on the same substrate, and the optical switch array is manufactured. Since each input terminal port and each output terminal port of the AWG are directly coupled by an optical waveguide, it is possible to maintain a value of −40 dB or less equivalent to the switch characteristic in crosstalk.

When the optical switch array shown in FIG. 1 is actually assembled, the overall size is about 1 mm × 1 mm. This size is a conventional Mach-Zehnder type 2 × 2
2 × 2 2 switches manufactured by arranging two TO switches in parallel
As compared with the size of the optical switch array, the mounting area is about one tenth, which is extremely small. 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 optical switch array manufactured using the Mach-Zehnder TO switch.

Further, since the optical switch array of the present invention is extremely small, an optical add / drop multiplexer can be manufactured using this optical switch array.
The size can be significantly reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 2 shows an embodiment of an optical switch array according to the present invention.

Here, a first optical waveguide group 51 comprising eight optical waveguides each having a parallel optical axis and a second optical waveguide group comprising eight optical waveguides each having a parallel optical axis are provided on an optical waveguide substrate 50. The second optical waveguide group 52 and the second optical waveguide group 5 are arranged and formed such that the respective optical waveguides intersect each other substantially orthogonally.
2 of the first optical waveguide group 5 among the intersections with the respective optical waveguides.
The switch unit 53 is provided only at eight diagonal intersections of the entire intersection so that the number of intersections through which the light switched and output from the first to the second optical waveguide group 52 passes is the same in each optical waveguide. (SW (a) to (h)) are provided.

The configuration of each switch section 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 of the slit in the longitudinal direction. Filling / removal of the liquid, as described above,
One of the heaters provided near the center (lower portion) and both ends in the longitudinal direction of the slit is heated, and the refractive index matching liquid is moved in the slit. Further, an optical fiber 54 for optical input / output is connected to each optical waveguide.

First, the switch behavior of the 8-series pseudo 2 × 2 optical switch array shown in FIG. 2 is as follows.
It has been confirmed that the switch operates normally as a low crosstalk pseudo 2 × 2 optical switch sufficient for optical communication.

When the light transmitting (through) state is referred to as off and the reflection switching (cross) state is referred to as on, when all the switches 53 are off, the input light from the A side is output from the B side output port. 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.

When any one of the switch units 54 is turned on, A corresponding to the turned on switch unit
The light from the side optical waveguide is propagated to the D side optical waveguide, and
It is not propagated to the 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.

According to this embodiment, the pseudo 2 × 2 optical switch array of the present invention is a conventional Mach-Zehnder type 2 × 2 TO
It can be said that crosstalk can be significantly reduced as compared with the switch.

Second, when the 8-unit pseudo 2 × 2 optical switch array shown in FIG. 2 is actually assembled, the overall size is 3 mm.
With a size of about 3 mm, the mounting area is remarkably reduced to about one tenth, compared to the size of an 8-unit 2 × 2 optical switch array manufactured by arranging eight conventional Mach-Zehnder 2 × 2 TO switches in parallel. 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.

Third, in the eight-unit pseudo 2 × 2 optical switch array shown in FIG. 2, the number of intersections passing when the light travels from the A-side optical waveguide to the D-side optical waveguide is made equal. Since the switch section (slit) is provided at the intersection only in the diagonal direction, there is no variation in the loss between the output ports and a constant value is always taken. Therefore, the multiple pseudo 2 of the present invention
It can be said that the × 2 optical switch array has remarkably advantageous characteristics when it is combined with another optical element such as AWG.

[Embodiment 2] FIG. 3 shows an optical add-in device according to the present invention.
An example of an embodiment of a drop multiplexer, here, an optical integrated type 16-channel AWG add / drop multiplexer in which a 16-unit pseudo 2 × 2 optical switch array and an arrayed waveguide grating (AWG) are integrated on the same substrate is shown. is there.

That is, in FIG. 3, reference numeral 60 denotes an optical waveguide substrate;
Reference numerals 1 and 62 denote array waveguide diffraction gratings (AWG) corresponding to the add operation, and 63 and 64 denote array waveguide diffraction gratings (AWG) corresponding to the drop operation, which connect between AWG 61 and AWG 63 and between AWG 62 and AWG 64. In the middle of the optical waveguide, a 16-unit pseudo 2 × 2 optical switch array in which the number of optical waveguides constituting the first and second optical waveguide groups is 16 in the 8-unit pseudo 2 × 2 optical switch array shown in FIG. 65 are arranged, and by switching of the 16 pseudo 2 × 2 optical switch array 65, a signal of a desired wavelength is added / dropped out of 16 channels as described below.

That is, when the 16 pseudo 2 × 2 optical switch array 65 is ON (cross), the signal of 16 wavelengths inputted from the main input port is first split by the AWG 62,
The signals are multiplexed again by the AWG 63 through the cross port of the 16-unit pseudo 2 × 2 optical switch 65 and output to the main output port. Next, a 16-unit pseudo 2 × 2 optical switch array 65
Is turned off (through), the respective wavelength signals demultiplexed by the AWG 62 are multiplexed by the AWG 64 through the corresponding through-ports of the 16-unit pseudo 2 × 2 optical switch array 65, and are collectively output from the drop port. Is done.

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 constructed using a conventional Mach-Zehnder 2 × 2TO switch. The mounting area can be remarkably reduced to about one tenth as compared with the size of the 16-channel AWG add / drop multiplexer excluding the AWG portion.

[0042]

As described above, according to the present invention,
An optical switch array having a sufficiently low crosstalk and a small size can be constructed, and an optical add / drop multiplexer manufactured by using the optical switch array is also a module having a low crosstalk and a high degree of integration, that is, a small and inexpensive module. FTTD (fiber to the desk) or optical LAN (local area network)
It can be effectively used for optical interconnections in user-based optical networks and communication processing devices.

[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 a configuration diagram showing an example of an embodiment of an optical add / drop multiplexer according to the present invention;

[Explanation of symbols]

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 continuous pseudo 2 × 2
Optical switch array.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 30, 1999 (September 9, 1999
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Fumio Shimokawa 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo F-term in Nippon Telegraph and Telephone Corporation (reference) 2H047 KB01 KB10 LA09 MA05 RA08 TA05 5K002 AA07 BA02 BA05 BA06 CA21 DA02 DA09 DA13 FA01 5K069 AA02 AA16 BA09 CB10 DB07 DB33 EA24 EA29

Claims (3)

[Claims] 1. A first optical waveguide group including n (n is a natural number) optical waveguides each having a parallel optical axis, and a second optical waveguide group including n optical waveguides each having a parallel optical axis. A waveguide group is disposed such that the respective optical waveguides intersect each other, and an optical waveguide uniquely corresponding to an intersection between each optical waveguide of the first optical waveguide group and each optical waveguide of the second optical waveguide group An optical switch, characterized in that a switch unit is provided only at the intersection between the optical waveguides so that light from the optical waveguides of the first optical waveguide group can go straight as it is or can be switched to and output from the optical waveguides of the second optical waveguide group. array. 2. A switch unit is provided only at a diagonal intersection of the entire intersection among the intersections of each optical waveguide of the first optical waveguide group and each optical waveguide of the second optical waveguide group. The optical switch array according to claim 1, wherein: 3. An optical switch array according to claim 1 or 2, and an arrayed waveguide grating are integrated on the same substrate, and each input port of the optical switch array and each output of the arrayed waveguide grating. An optical add / drop multiplexer, wherein an end port is directly coupled with an optical waveguide.