JPH08331047A - Optical switch, optical switch controller and optical network - Google Patents

Abstract

PURPOSE: To make the controller small, to set freely a wavelength interval of a wavelength multiplexed light and select an optional path for each wavelength by employing an acoustooptical filter for a switch element of an optical switch thereby using the characteristic. CONSTITUTION: An optical signal with multiplexed wavelength of 1548nm and 1556nm is given to optical modulators 31-1 to 31-m, and an acoustic optical modulator is used to multiplex subcarriers for each wavelength. The signal is branched by optical branching devices 521, 522 of an acoustic optical filter driver 511 and multiplexed by a multiplexer 561, converted into an O/E converter 571 into an electric signal, a beat between the signal and a signal fro a natural frequency oscillator 531 by a multiplier 541 an the result is fed to an acoustooptic filter 11 via a filter 551. When a difference of a frequency between a sub carrier and a signal from the oscillator 531 is 175MHz or 174MHz, a cross state is attained for the light of 1548nm and 1556nm. Thus, the optical switch is controlled independently for each wavelength by the optical modulator and switching between optional paths is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for exchanging signals between optical transmission lines, and more particularly to optical exchange for handling wavelength division multiplexed signals.

[0002]

2. Description of the Related Art As a signal switching circuit between a plurality of optical transmission lines through which a wavelength division multiplexed signal is transmitted, for example, Japanese Patent Application Laid-Open
The 1-126096 publication proposes an optical switch as shown in FIG.

In the optical switch shown in FIG. 5, n waves are wavelength-multiplexed in each of m optical transmission lines 21-1 to 21-m. These signals are wavelength-converted by the wavelength converters 41-1 to 41-m, separated by wavelengths by the optical demultiplexers 33-1 to 33-m, collected for each wavelength, and then n pieces of m Xm Optical space switching circuits 43-1 to 43-n are used for switching, and n different wavelengths are combined into one optical transmission line by optical multiplexers 34-1 to 34-m.
The wavelengths are converted by the wavelength converters 44-1 to 44-m and then output to m optical transmission lines 22-1 to 22-m.

In addition, an acousto-optic filter (acoustooptic f
ilter) at a position away from the light, superimpose the subcarrier signal on the light and then emit it to the optical transmission line, and in the acousto-optic filter controller, the beat between this modulated signal and the oscillator output provided in the acousto-optic filter controller. If this is taken, it is possible to drive the acousto-optic filter by this beat and perform the filter operation, as described in a document by WI Way et al. (IEEE Photonics Technology Letters).
s), Vol. 4, No. 4, 1992, pp. 402-405).

[0005]

The optical space switch circuit switches all the passing signal lights regardless of the wavelength. Therefore, the optical space switch circuit alone cannot output the wavelength-multiplexed signal to the optical transmission line different for each wavelength.

In order to overcome this drawback, the above-mentioned Japanese Patent Laid-Open No. 1-12
In the Japanese Laid-Open Patent Publication No. 6096, etc., the wavelength-multiplexed input signal light is separated into wavelengths by a demultiplexer, switched by an optical space switch circuit, and then multiplexed again.

However, in this configuration, m 1 × n demultiplexers, n m × m optical space switch circuits, and m n × 1 multiplexers are required, which makes the device large. Have.

Further, the configuration described in the literature by WI Way and the like can only select whether or not to send a signal to a certain node, and cannot switch the signal between arbitrary routes.

Therefore, an object of the present invention is to provide an optical switch that is small in size, reduces the number of required components, and independently switches between wavelengths without demultiplexing wavelength-division multiplexed light. To provide. Another object of the present invention is to provide an optical switch capable of independently switching between arbitrary paths for each wavelength by a subcarrier signal superimposed on light.

[0010]

To achieve the above object, the present invention comprises an optical switch comprising one or a plurality of acousto-optic filters, the acousto-optic filters being connected in parallel and / or in cascade form. I will provide a.

The present invention is preferably characterized in that the driving high frequency signal of the acousto-optic filter is turned on / off to switch the cross / bar state of the light of the corresponding wavelength.

Further, in the present invention, preferably, the driving high frequency signal of the acousto-optic filter is made variable so that the wavelength interval of the wavelength multiplexed light can be freely set.

Further, according to the present invention, an optical modulator comprising an optical switch including an acousto-optic filter as a switch element is connected in parallel and / or in cascade, and an optical modulator provided in an optical transmission line before the input of the optical switch is used. An optical switch is characterized in that a subcarrier signal is superimposed on the input light of the acousto-optic filter and the switching of the acousto-optic filter is controlled by the subcarrier signal.

Further, the present invention is preferably an optical switch control device in which optical switches including an acousto-optic filter are connected in parallel and / or in a tandem form, and the optical switch control device is provided in the input stage of the optical switch control device. , A plurality of optical modulators for superimposing a subcarrier signal on each light in the plurality of optical transmission lines, the optical switch, a signal light propagating through one of the input optical transmission line of the acousto-optic filter The first optical branch that partially branches, the second optical branch that partially branches the signal light propagating in the other input optical transmission line, and the light that has been split by the first and second optical branches are multiplexed. A multiplexer,
An optical / electrical converter that receives the output light of the multiplexer and obtains a subcarrier signal, an oscillator that outputs an oscillation frequency specific to the acousto-optic filter, and an output signal of the optical / electrical converter of the oscillator. An optical switch control device comprising: a multiplier for multiplying an output to obtain a difference frequency between the output frequency of the subcarrier signal and the oscillator and inputting the difference frequency to the acousto-optic filter.

According to the present invention, a transmission node is provided with at least an optical modulator, a subcarrier signal is superposed on input light of an optical switch including an acousto-optic filter by using the optical modulator, and the optical switch is provided by the subcarrier signal. An optical network is provided which controls switching of the optical network.

Further, the present invention preferably comprises a light source, an optical modulator for superimposing a subcarrier signal on light, a plurality of nodes including an optical receiver, the plurality of nodes and an optical transmission line. A coupled optical switch, and an optical transmission line coupling the plurality of nodes and the optical switch,
The optical switch has a first optical branch that partially branches signal light that propagates through one of the input optical transmission paths of the acousto-optic filter and a second optical branch that partially branches signal light that propagates through the other input optical transmission path. An optical branch, a multiplexer that combines the lights branched by the first and second optical branches, an optical-electrical converter that receives the output light of the multiplexer to obtain a subcarrier signal, An oscillator that outputs a specific oscillation frequency for an acousto-optic filter, and an acousto-optic device that multiplies the output signal of the optical-electrical converter by the output of the oscillator to obtain a difference frequency between the sub-carrier signal and the output frequency of the oscillator. An optical network comprising: a multiplier for inputting to a filter.

[0017]

The operation and principle of the present invention will be described below.

The operation principle of the acousto-optic filter is described in a document by SE Harris et al. (Journal of the Optical Society of America, No. 59).
Vol. 6, No. 6, 1969, pp. 744-747).

The acousto-optic filter is in the cross-state (see FIG. 4A) only for light having a wavelength corresponding to the frequency of the input high-frequency start signal, and is in the bar-state (see FIG. 4 (B) for other wavelengths. ) See).

Further, the acousto-optic filter has a feature that when a high frequency signal having a plurality of different frequencies is inputted, a plurality of lights having different wavelengths corresponding to the respective high frequency signals can be cross-stated.

Therefore, it can be used as a space switch capable of switching independently for each wavelength.

With the optical switch of the present invention, it is possible to realize the same operations as those of the demultiplexer, the multiplexer, and the number of optical space switches equal to the number of wavelengths in the conventional switch. Therefore, the device can be downsized.

Further, in the conventional optical switch, since the output wavelength of the optical demultiplexer and the input wavelength of the optical multiplexer cannot be changed, it is not possible to freely set the wavelength interval between the wavelength multiplexed lights. could not.

On the other hand, according to the optical switch of the present invention, the selected wavelength of the acousto-optic filter can be continuously changed by continuously changing the frequency of the driving high frequency signal. The wavelength spacing between each of the lights can be set freely.

Next, the switch operation by superposing the subcarrier signals will be described.

Using the optical modulator, subcarrier signals having different frequencies, the number of which is equal to the number of switch stages, are superimposed on the light before input to the acoustooptic filter.

Since it is necessary for the optical modulator to modulate each wavelength independently, an acousto-optic modulator, an acousto-optic filter or the like is used.

The driver of each acousto-optic filter takes a beat between the subcarrier signal superimposed on the light and the oscillator output. If the frequency of the oscillator in the acousto-optic filter driver is different for each stage, the beat frequency is different for each stage. Only the acousto-optic filter at the stage where the beat frequency is equal to the drive frequency of the acousto-optic filter is in the cross-state, and switching between arbitrary routes is possible.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

[0030]

Embodiment 1 FIG. 1 is a diagram for explaining an embodiment of an optical switch according to the present invention. Referring to FIG. 1, this embodiment is configured by connecting a plurality of acousto-optic filters in a crossbar type.

1548 is provided on each of the four input optical transmission lines 211 to 214.
2 wavelengths of 1 nm and 1556 nm are wavelength-multiplexed, and the acousto-optic filter 111
Type in ~ 144.

The acousto-optic filters 111 to 144 are in a cross-state when the driving frequency is 175 MHz for the light having the wavelength of 1548 nm, and the driving frequency is 174 MHz for the light having the wavelength of 1556 nm.
When, it becomes a cross state.

For each acousto-optic filter, frequency 175M
By switching the high frequency signal of Hz or 174 MHz on or off, the switching of the light of wavelengths 1548 nm and 1556 nm can be performed without being affected by the light of other wavelengths.

The blocking property of the switch circuit is the same as when switching is performed using an optical space switch between the input / output optical transmission lines that are not wavelength-multiplexed. In addition to the crossbar, double crossbar, depending on the degree of obstruction required
N-Stage Planar, Bene
s), cross network (Clos Network), multiple substrates (Multiple Substrate), etc. can be adopted. For the configuration of these switch circuits, see Ron A. Spanke's reference (IEEE Communications Magazine, Vol. 25, Vol. 5).
Issue, 1987, pp. 42-48).

In the example of the prior art shown in FIG. 5, each of the optical switch circuits (optical space switch circuits) 43-1 to 43-m has the above-described structure such as a crossbar, and m pieces of them are provided. In addition to this, an optical demultiplexer, a multiplexer, etc. are required and the device becomes large in size. However, in this embodiment shown in FIG. 1, one optical switch is used for each wavelength for a plurality of wavelengths. The size of the device can be reduced because switching can be independently performed between arbitrary routes.

Further, since the transmission wavelengths of the optical demultiplexer and the optical multiplexer used in the prior art are fixed, it is not possible to deal with the change of the wavelength interval of each wavelength-multiplexed light. In the above optical switch, it is possible to continuously change the selected wavelength of the acousto-optic filter by continuously changing the driving RF frequency, and it is possible to cope with the change in the wavelength interval.

In the present embodiment, the number of input / output transmission lines of the optical switch is not limited to 4, but may be a desired natural number.

Further, in the present embodiment, the number of wavelength division multiplexing in each optical transmission line is not limited to 2, 3, 4,
A desired natural number such as 8, 16, 32, 100 can be set.
Furthermore, the number of output optical transmission lines is larger than the number of input optical transmission lines,
Alternatively, the number of output optical transmission lines can be made smaller than the number of input optical transmission lines.

In this embodiment, the wavelength of the input light is not limited to the 1.5 μm band but may be 1.3 μm band or the like as long as the acousto-optic filter operates. The selected wavelength of the acousto-optic filter changes depending on the acousto-optic filter temperature, but this can be corrected by changing the frequency of the oscillator in the acousto-optic filter driver. Also, the number of stages is not limited to two,
A desired number of stages such as 3 stages and 10 stages may be used. Increasing the number of steps causes a problem of light loss due to passing through the acousto-optic filter,
In this case, the loss can be compensated by using an optical amplifier such as an Er-doped optical fiber amplifier, a Pr optical fiber amplifier, or a semiconductor optical amplifier.

[0040]

Second Embodiment FIG. 2 is a diagram for explaining the configuration of the second embodiment of the present invention.

Two waves having wavelengths of 1548 nm and 1556 nm are wavelength-multiplexed in each optical transmission line and input to the optical modulators 31-1 to 31-m. An acousto-optic modulator is used as the optical modulators 31-1 to 31-m to superimpose subcarrier signals independently for each wavelength.

In each acousto-optic filter driver 511,
First, part of the input of the acousto-optic filter 11 is divided into optical branches 521, 5
Branch at 22.

After the branched light is multiplexed by the optical multiplexer 561, it is converted into an electric signal by the O / E (optical / electrical) converter 571, and the acousto-optical filter driver of each stage is converted by using the multiplier 541. It takes a beat with the oscillator 531 that oscillates at its own frequency.

Then, after the excess frequency component is removed by the bandpass filter 551, it is input to the acousto-optic filter 11.

As described above, the acousto-optic filter 11 responds to light with a wavelength of 1548 nm when the difference between the frequency of the subcarrier signal superimposed by the optical modulator and the frequency of the oscillator in the acousto-optic filter driver is 175 MHz. Cross state, 174M
At Hz, it becomes a cross-state for light with a wavelength of 1556 nm.

Assuming that the frequency of the oscillator in the acousto-optic filter driver of the first stage is 100 MHz and the frequency of the oscillator in the acousto-optic filter driver of the second stage is 200 MHz, the subcarrier signal of 275 MHz is generated by the optical modulator. When is superimposed on the light, the first stage becomes the cross-state and the second stage becomes the bar-state for the 1548 nm light. For 1556 nm light, both the first and second stages are in bar state.

As described above, the optical switches 31-1 to 31-m provided in the preceding stage of the optical switch circuit can independently control the optical switch for each wavelength and demultiplex the wavelength-multiplexed light. Instead, switching between arbitrary routes can be performed.

In the present embodiment, the number of input transmission lines and the number of wavelength division multiplexing of the input transmission lines may be desired numbers as in the first embodiment. The blocking property of the switch circuit for each wavelength is the same as in the first embodiment.

The frequency of the subcarrier signal superimposed on the light and the frequency of the in-drive oscillator of the acousto-optic filter are
It suffices that the difference between them is around 175 MHz which drives the acousto-optic filter, and not only the combination of 275 MHz and 100 MHz as in the above embodiment, but also 175 MHz and 0 MHz, 2.5 GHz and 2.325G.
Anything such as Hz is acceptable.

Also, the beat frequency is not set to 175 MHz, but 175 M
Up-convert as a frequency lower than Hz or 17
The acousto-optic filter drive frequency can be set to 175 MHz by down-converting it as a frequency higher than 5 MHz.

The frequency of the oscillator in the second-stage self-routing optical wavelength switch is such that the difference from the frequency of the oscillator in the first stage is larger than the driving frequency bandwidth (about 5 MHz) of the acousto-optic filter covering the 1.5 μm band. If you decide to 100M
It does not have to be Hz.

In the present embodiment, the interconnection form of the plurality of optical wavelength switches 501 to 504 shown in FIG. 2 is not limited to the crossbar type as described in the first embodiment, but may be a desired interconnection form. Good.

[0053]

[Third Embodiment] FIG. 3 is a diagram showing the configuration of a third embodiment of the present invention. Referring to FIG. 3, each of the nodes 60-1 to 60-m is
Light sources 61-1, 61-3, 61-m-1 with oscillation wavelength of 1548 nm and oscillation wavelength
It is equipped with light sources 61-2, 61-4, 61-m of 1556 nm, light of two wavelengths is combined by optical multiplexers 63-1, 63-2, 63-m, and optical modulator 31-1, Input to 31-2, 31-m.

The optical modulators 31-1, 31-2, 31-m are acousto-optic modulators, acousto-optic filters, etc. capable of independently modulating each wavelength. These optical modulators 31-1, 31-2, and 31-m superimpose subcarrier signals on the light of each wavelength independently, and wavelength-multiplexed light is respectively transmitted to the optical transmission lines 21-1, 21-2, and 21-m. Output.

Alternatively, light sources 61-1 and 61 having an oscillation wavelength of 1548 nm
-3, 61-m-1 and the outputs of light sources 61-2, 61-4, 61-m with an oscillation wavelength of 1556 nm are modulated before being combined, and subcarriers are superimposed, then combined, and then optical transmission is performed. You may output to the paths 21-1, 21-2, 21-m.

In the optical wavelength switch 401 circuit (same configuration as the optical wavelength switch 401 in FIG. 2), only the acousto-optic filter corresponding to the subcarrier signal is in the cross state according to the principle explained in the second embodiment. Light of each wavelength is independently switched and output to the optical transmission lines 22-1, 22-2, 22-m.

As described above, the optical switch provided in each node can remotely control the optical switch for each wavelength,
It is possible to connect arbitrary nodes without demultiplexing the wavelength-multiplexed light.

Although the present invention has been described above in accordance with the above-mentioned aspects, the present invention is not limited to the above-mentioned aspects, and it is needless to say that it includes various aspects according to the principle of the present invention.

[0059]

As described above, according to the optical switch of the present invention, one optical switch can perform optical switching without demultiplexing wavelength-division-multiplexed light. Has the effect of achieving Further, according to the present invention, the wavelength interval of the wavelength multiplexed light can be freely set by changing the frequency of the driving high frequency signal of the acousto-optic filter. Furthermore, according to the present invention, the optical switch circuit is controlled by superimposing a subcarrier signal on light by an optical modulator provided in a node distant from the optical switch circuit front stage or the optical switch,
Since it is possible to switch between arbitrary routes for each wavelength, it is necessary to have as many optical demultiplexers as the number of input transmission lines, optical switch circuits equal to the number of wavelength multiplexes, and optical multiplexers equal to the number of output transmission lines. Therefore, the device can be downsized.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a first embodiment of the present invention, showing a structural example of an optical switch in which an acousto-optic filter is connected in a crossbar type.

FIG. 2 is a diagram for explaining the second embodiment of the present invention, showing the configuration when an optical modulator is connected to the preceding stage of an optical switch circuit.

FIG. 3 is a diagram for explaining a third embodiment of the present invention, showing a configuration in the case where an optical modulator is installed in a transmission node apart from an optical switch circuit.

FIG. 4A is a diagram showing a cross-state state of the acousto-optic filter. FIG. 6B is a diagram showing a bar state of the acousto-optic filter.

FIG. 5 is a configuration diagram of a conventional optical switch circuit.

[Explanation of symbols]

 11, 111-144 Acousto-optic filter 21-1-21-m, 22-1-22-m Optical transmission line 211, 212, 213, 214, 221, 222, 223, 224 Optical transmission line 31-1 to 31- m Optical modulator 33-1, 33-m Optical demultiplexer 34-1, 34-m Optical multiplexer 401 Optical wavelength switch circuit 43-1, 43-n Optical space switch 41-1, 41-m, 44- 1, 44-m Wavelength converter 501, 502, 503, 504 Optical wavelength switch circuit 511 Acousto-optic filter driver 521, 522 Optical branch 531 Oscillator 541 Multiplier 551 Bandpass filter 561, 63-1, 63-2, 63 -m Optical multiplexer 571 O / E converter 60-1, 60-2, 60-m Node 61-1, 61-2, 61-3, 61-4, 61-m-1, 61-m Light source 62 -1, 62-2, 62-m optical receiver

Claims (7)

[Claims] 1. A system comprising one or more acousto-optic filters,
An optical switch configured by connecting the acousto-optic filters in parallel and / or in tandem. 2. The optical switch according to claim 1, wherein the driving high frequency signal of the acousto-optic filter is turned on / off to switch the cross / bar state of the light of the corresponding wavelength. 3. The optical switch according to claim 2, wherein the driving high frequency signal of the acousto-optic filter is made variable so that the wavelength interval of the wavelength multiplexed light can be freely set. 4. An acousto-optic device comprising an optical switch comprising an acousto-optic filter as a switching element connected in parallel and / or in a tandem form, using an optical modulator provided in an optical transmission line before an input of the optical switch. An optical switch, wherein a subcarrier signal is superimposed on input light of a filter, and switching of the acousto-optic filter is controlled by the subcarrier signal. 5. An optical switch control device comprising an optical switch including an acousto-optic filter as a switch element connected in parallel and / or in a tandem form, the optical switch control device being provided in a stage preceding an input of the optical switch control device. A plurality of optical modulators for superimposing subcarrier signals on respective lights in the transmission path, wherein the optical switch partially branches signal light propagating in one of the input optical transmission paths of the acousto-optic filter; One optical branch, a second optical branch for partially branching the signal light propagating through the other input optical transmission line, and a multiplexer for multiplexing the lights branched by the first and second optical branches. An optical / electrical converter that receives the output light of the multiplexer and obtains a subcarrier signal, an oscillator that outputs an oscillation frequency specific to the acousto-optical filter, and an oscillator that outputs the output signal of the optical / electrical converter. of Multiplying the force, the multiplier to be input to the acousto-optic filter subcarrier signal and obtain the difference frequency of the output frequency of the oscillator, the optical switch control device characterized by comprising a. 6. The transmitting node comprises at least an optical modulator,
An optical network characterized in that a subcarrier signal is superimposed on input light of an optical switch including an acousto-optic filter using the optical modulator, and switching of the optical switch is controlled by the subcarrier signal. 7. A light source, an optical modulator for superimposing a subcarrier signal on light, a plurality of nodes including an optical receiver, and an optical switch coupled to the plurality of nodes by an optical transmission line. The optical switch includes a first optical branch that partially branches signal light that propagates through one of the input optical transmission paths of the acousto-optic filter, and a partial branch of signal light that propagates through the other input optical transmission path. A second optical branch, a multiplexer that multiplexes the lights branched by the first and second optical branches, and an optical-electrical converter that receives the output light of the multiplexer and obtains a subcarrier signal An oscillator that outputs an oscillation frequency peculiar to the acousto-optic filter; and an output signal of the optical-electrical converter is multiplied by an output of the oscillator to obtain a difference frequency between the subcarrier signal and the output frequency of the oscillator. The acousto-optic filter An optical network, characterized in that it and a multiplier for inputting.