JP2004312256A - Optical transmission apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission apparatus capable of preventing the occurrence of misconnection on the occurrence of the misconnection in the apparatus. <P>SOLUTION: Each of optical fiber amplifiers 202 individually applies intensity modulation to each channel light by using each of unique modulation frequencies f in advance. Then monitor circuits 203, 204 read the modulation frequencies of each channel light and give the result to a frequency identification circuit 211 wherein each channel light is identified. A channel light causing misconnection is discriminated by the collation of the result of the identification with the routing information of an optical component 200. A variable optical attenuator 206 applies intensity modulation furthermore to the channel light discriminated to have misconnection so as to suppress the transmission of information to a destination. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical transmission device used in a wavelength division multiplexing transmission system and the like, in which channel light is transmitted transparently inside the device, and an erroneous transmission prevention method used in the optical transmission device.
[0002]
[Prior art]
In recent years, communication demand has increased remarkably. In response to the demand, the use of DWDM (Dense Wavelength Division Multiplex) technology and the like to increase the size of the optical backbone communication network has been promoted, but bottlenecks in optical transmission devices have become increasingly prominent. This is because the conventional optical transmission device converts an optical signal having a wavelength corresponding to each channel (hereinafter, referred to as channel light) into an electric signal and performs a routing process using the electric signal.
[0003]
From such a background, an all-optical transmission device that routes channel light as it is without performing optical-electrical-optical conversion (OEO conversion) inside the device is being put to practical use. Since the all-optical transmission device does not perform OEO conversion inside the device, it is expected that a protocol-free and bit-rate-free optical network can be constructed. This type of device includes an OADM (Optical Add Drop Multiplexer) device, an optical cross connect (Optical Cross Connect) device, and the like.
[0004]
This type of device includes various optical units such as an optical switch for switching the channel light path and an optical amplifier for amplifying the channel light. In order to keep these units in a healthy state, it is necessary to reliably detect any failure, erroneous connection that may occur artificially, or erroneous connection due to a software defect. However, since this type of apparatus does not perform OEO conversion, it is not possible to distinguish individual channel lights based on overhead information of a transmission signal or the like.
[0005]
Therefore, various attempts have been made in an all-optical transmission apparatus to uniquely identify each channel light in the apparatus. For example, a technique has been considered in which intensity modulation is performed on each channel light in a different pattern, and each channel light is identified by reading the modulation pattern. According to such a method, it is possible to trace each channel light even when all the channel lights are transmitted at the same wavelength inside the device.
[0006]
However, in the current device, only the channel light can be uniquely identified, and no technology for subsequent processing has been established. That is, even if it is possible to detect that the channel light is connected to the wrong path inside the device, the channel light is connected to the wrong route outside the device and the transmission information is transmitted to the wrong route. There is no way to prevent a connection.
[0007]
Related technologies are disclosed in Patent Literatures 1 and 2 below.
Patent Literature 1 discloses an optical amplifier that superimposes a supervisory information optical signal on an output optical signal and transfers the supervisory information optical signal downstream, and modulates the pump light power with the supervisory information and modulates the gain of the optical amplifier accordingly to monitor. A technique for widening the band given to an information signal has been disclosed.
[0008]
Patent Literature 2 discloses a technique that enables information transmission by excitation light by modulating the excitation light with a high-frequency modulation signal having a period shorter than the fluorescence lifetime of the excited state.
[0009]
[Patent Document 1]
JP-A-7-131421 (paragraph number [0016] etc.)
[0010]
[Patent Document 2]
JP-A-8-331058 (paragraph numbers [0016] to [0023] etc.)
[0011]
[Problems to be solved by the invention]
As described above, even if each channel light can be uniquely identified in the all-optical transmission apparatus, a technique for preventing a misconnection has not yet been known.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical transmission device capable of preventing a misconnection when an erroneous connection occurs in the device.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an optical component (for example, an optical switch) that routes a plurality of channel lights each including transmission information as it is based on given routing information, Characteristic adding means (for example, an optical fiber amplifier) for adding the identification characteristic of the optical component before entering the optical component, and identification means for individually identifying each channel light emitted from the optical component by monitoring the identification characteristic (E.g., a monitor circuit), a determination unit (e.g., a switch determination circuit) that checks a result of the identification by the identification unit with the routing setting information and determines an erroneous connection in the optical component for each channel. Suppression means (for example, a variable optical attenuator) for suppressing information transmission by a channel light determined to be incorrectly connected is provided. .
[0013]
By adopting such a means, a characteristic characteristic is added to each channel light by the characteristic adding means, and each channel light is identified by the identification means based on the characteristic. If the result of this identification and the routing information do not match, it means that an erroneous connection has occurred in the device, and the determination means determines that. Then, the information transmission by the channel light determined to be erroneously connected is suppressed by, for example, blocking the light or applying a strong intensity modulation by the suppression means. As a result, when an erroneous connection occurs in the device, even if the channel light reaches the wrong destination, the transmission information is already destroyed, or the transmission information is not transmitted because the channel light does not reach the wrong destination. The transmission to the wrong destination is suppressed. Therefore, it is possible to prevent misconnection.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a functional block diagram showing the configuration of the optical transmission device according to the present invention. In this optical transmission device, channel light including transmission information is transmitted transparently in the device. As a format of the transmission information, for example, a time division multiplexing format such as an SDH (Synchronous Digital Hierarchy) frame or a SONET (Synchronous Optical Network) frame is applied.
[0015]
In FIG. 1, wavelength multiplexed light arriving via an optical fiber WL is split by an optical splitter 201 into channel lights having different wavelengths. Each channel light is incident on an optical component 200 such as an optical switch via an optical fiber amplifier 202. The optical fiber amplifier 202 compensates an optical loss generated in an optical transmission line between another adjacent optical transmission device or optical repeater or the optical demultiplexer 101 for each channel light.
[0016]
The optical component 200 routes each channel light as it is based on routing information given from the outside. The channel light whose path has been switched here enters the optical multiplexer 207 from the optical component 200 via the optical fiber amplifier 205, is wavelength-multiplexed, and is transmitted to the optical fiber EL.
[0017]
Meanwhile, each optical fiber amplifier 202 is provided with a unique modulation frequency f for each channel light generated by a frequency (ID: identification) source 208 via a modulation-side channel selection switch 209. Each optical fiber amplifier 202 modulates the intensity of the channel light according to a given modulation frequency f, whereby each channel light is provided with a unique and identifiable modulation characteristic.
[0018]
The modulation-side channel selection switch 209 operates under the control of the sequence control circuit 212 based on the routing information, and switches and outputs the modulation frequency f according to the routing information to the optical fiber amplifier 202. Thus, the identification characteristic to be given to each channel light is switched according to the routing setting of the optical component 200.
[0019]
Monitor circuits 203 and 204 are provided for each channel light on the entrance path and the exit path in the optical component 200. The monitor circuits 203 and 204 read the modulation frequency given to each channel light, and give the result to the monitor-side channel selection switch 210. The monitor-side channel selection switch 210 performs a switching operation in accordance with a control signal provided from the sequence control circuit 212, and outputs the outputs of the monitor circuits 203 and 204 to the frequency identification circuit 211 by a combination of input and output paths according to the routing information. give.
[0020]
The frequency identification circuit 211 identifies the modulation frequency f acquired by the monitor circuits 203 and 204, and supplies the result to the switch determination circuit 214. The switch determination circuit 214 compares the identified modulation frequency f with the routing setting information, and determines an erroneous connection in the optical component 200 for each channel light.
[0021]
The wavelength light output from the optical component 200 enters the optical fiber amplifier 205 irrespective of the presence or absence of erroneous connection in the device. The optical fiber amplifier 205 is driven by ALC (Automatic Level Control), and performs level compensation on each channel light output from the optical component 200 and removes its intensity modulation component. Thereafter, each channel light is input to the optical multiplexer 207 via the variable optical attenuator 206, wavelength-multiplexed, and transmitted to the optical fiber EL.
[0022]
Each of the variable optical attenuators 206 is supplied with the frequency signal F from the oscillator 215 as a drive signal via the switch determination circuit 214 when the input channel light is the one causing the erroneous connection in the device. The attenuation rate of the variable optical attenuator 206 is varied according to the frequency signal F, and thereby the intensity of the channel light in which the erroneous connection has occurred is modulated according to the frequency signal F.
[0023]
It is preferable that the frequency of the intensity modulation, that is, the frequency of the frequency signal F is set to be about the response frequency of the population inversion of the rare-earth element-doped optical fiber. In this way, even when an ALC-driven optical fiber amplifier or the like is connected to the subsequent stage of the device, the intensity modulation component can be prevented from being lost. In addition, it is more preferable to increase the intensity of the intensity modulation so that the intensity modulation component is not lost by the subsequent ALC-driven optical fiber amplifier.
[0024]
As described above, in the present embodiment, the intensity of each channel light is individually modulated in advance by the optical fiber amplifier 202 at the unique modulation frequency f. Then, the modulation frequency of each channel light is read by the monitor circuits 203 and 204, and the result is given to the frequency identification circuit 211 to identify each channel light. On the basis of this, the channel light in which the erroneous connection has occurred is determined by collating with the routing information of the optical component 200. The channel light determined to be incorrectly connected is further subjected to intensity modulation by the variable optical attenuator 206 so as to suppress information transmission to the destination.
[0025]
As described above, the intensity modulation is performed again on the channel light in which the erroneous connection has occurred at the modulation frequency F, so that the transmission information included in the channel light is destroyed. Therefore, even if the channel light reaches the wrong destination, the transmission information is transmitted. Transmission can be prevented. Therefore, it is possible to prevent misconnection. Further, since the modulation frequency F can be used as the misconnection sign information, it is possible to inform that a device connected at a later stage has made a misconnection, which is useful for system maintenance. Further, since the transmission information is destroyed by the intensity modulation, the optical signal itself is transmitted as it is. This can minimize the operational effects on various devices and systems, including the optical amplifier (repeater) connected downstream.
[0026]
In addition, the modulation frequency F is set to the level of the response frequency of the population inversion of the rare earth element-doped optical fiber, or the intensity of the intensity modulation is increased to such an extent that the intensity modulation component is not lost by the subsequent ALC drive optical fiber amplifier. Then, even when an ALC drive optical fiber amplifier or the like is connected to the subsequent stage of the device, the intensity modulation component is not lost, and misconnection can be prevented more reliably.
[0027]
Note that the present invention is not limited to the above embodiment. For example, instead of the variable optical attenuator 206 in FIG. 1, an optical amplifier whose gain is controlled according to the modulation frequency F may be provided. Of course, the same effect can be obtained by providing a variable optical modulator or a high-speed optical switch element. If the modulation frequency F is given to the optical fiber amplifier 205 in FIG. 1 to perform gain control, the configuration can be simplified.
[0028]
In the above-described embodiment, it is preferable that the frequency of the frequency signal F is approximately equal to the response frequency of the population inversion of the rare-earth element-doped optical fiber, but it is not always necessary. For example, the frequency of the frequency signal F may be set to a level at which the wavelength of the erroneously connected channel light can be converted to a wavelength that does not belong to the wavelength division multiplexing system.
[0029]
Further, in the present embodiment, the intensity modulation is performed on the erroneously connected channel light on the output side of the optical transmission device to suppress the readability of the transmission information. However, the erroneously connected channel light may be more directly blocked. good. To do this, an optical switch may be provided in place of the variable optical attenuator 206 in FIG. 1 to switch the path of the erroneously connected channel light from the information transmission path to a path to be excluded. Alternatively, the same effect can be obtained by providing a light breaker. Further, by turning off the optical fiber amplifier 205 to which the erroneously connected channel light is incident, the channel light can be cut off more easily. In addition, various modifications can be made without departing from the spirit of the present invention.
[0030]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide an optical transmission device capable of preventing a misconnection when an erroneous connection occurs in the device.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing a configuration of an optical transmission device according to the present invention.
[Explanation of symbols]
WL optical fiber EL optical fiber 101 optical splitter 200 optical component 201 optical splitter 202 optical fiber amplifiers 203 and 204 monitor circuit 205 optical fiber amplifier 206 variable optical attenuator 207 optical multiplexing. Device 208 frequency source 209 modulation-side channel selection switch 210 monitor-side channel selection switch 211 frequency discrimination circuit 212 sequence control circuit 214 switch determination circuit 215 oscillator

Claims (8)

An optical component that routes a plurality of channel lights each including transmission information as light based on given routing information;
Characteristic adding means for adding a unique identification characteristic to each of the plurality of channel lights before entering the optical component,
Identification means for individually identifying each channel light emitted from the optical component by monitoring the identification characteristic thereof,
Determining means for comparing the result of the identification by the identification means with the routing setting information, and determining an erroneous connection in the optical component for each channel;
An optical transmission device comprising: a suppression unit that suppresses transmission of the transmission information by a channel light determined to be erroneously connected by the determination unit. The optical transmission device according to claim 1, wherein the characteristic adding unit modulates the plurality of channel lights with respective unique modulation characteristics to add the identification characteristics. When an optical fiber amplifier that amplifies each channel light by introducing each channel light into the amplification fiber to which the pumping light is optically coupled is connected to a stage subsequent to the suppression unit,
The deterrent means,
2. The optical transmission device according to claim 1, further comprising a modulation unit that intensity-modulates the channel light determined to be erroneously connected at a modulation frequency corresponding to a response frequency of a population inversion of the amplification fiber. The optical transmission device according to claim 3, wherein the modulation unit is a variable optical attenuator whose attenuation rate is controlled by a drive signal corresponding to the modulation frequency. The optical transmission device according to claim 3, wherein the modulation unit is an optical amplifier whose gain is controlled by a drive signal according to the modulation frequency. The optical transmission device according to claim 3, wherein the modulation unit superimposes misconnection indicator information on the channel light determined to be misconnection. 2. The optical transmission device according to claim 1, wherein the suppression unit is a switch unit that switches a path of the channel light determined to be incorrectly connected to a path to be excluded from the information transmission path. 2. The optical transmission device according to claim 1, wherein the suppression unit is a blocking unit that blocks the channel light determined to be incorrectly connected.

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