JP5087430B2 - Repeater, optical transmission system and switching method thereof - Google Patents

Description

The present invention relates to an optical amplifier, a repeater using an optical switch , an optical transmission system, and a switching method thereof, and in particular, does not require an additional device or line for transmitting switching information and can prevent erroneous switching of the line. The present invention relates to a repeater, an optical transmission system, and a switching method thereof .

  Conventionally, means for transmitting information that a line or relay station device in an optical transmission system is abnormal to another relay station has been proposed (see, for example, Patent Documents 1 to 4). By receiving this abnormality information, line switching and erroneous switching prevention are performed.

  Patent Document 1 discloses a monitoring method for monitoring a failure of a transmission line by causing a self-oscillation in an optical amplifier when an input signal from the transmission line disappears and detecting a light modulation frequency at this time by a relay station. Is disclosed.

  In Patent Document 2, pump light for an optical amplifier is transmitted to a previous-stage repeater, and the previous-stage repeater monitors a failure in the transmission path based on the presence or absence of the pump light. A method is disclosed in which when the pumping light cannot be detected, it is determined that the transmission line is faulty, and the line is switched to a backup line.

  In Patent Document 3, when the interruption of the input light due to a transmission path abnormality or the like is detected, a holding optical signal for holding the switching state of the optical repeater at the next stage is sent to the transmission path, thereby instantaneously switching the optical switch. An optical repeater is disclosed in which a disconnection is prevented from being transmitted to the next-stage relay station so that the optical amplifier does not make a false determination that a failure has occurred.

In Patent Document 4, control information of each repeater is held for all repeaters (optical amplifiers) that are affected by fluctuations in the input light level when a line is switched by detecting a transmission line abnormality or the like. Discloses a transmission path switching method for transmitting information using an optical monitoring channel or a data communication network.
Japanese Patent No. 3013113 Japanese Patent Laid-Open No. 9-233023 JP-A-5-211481 Japanese Patent No. 3613337

However, the above-described conventional technique has the following problems.
In the prior art disclosed in Patent Document 1, since the self-oscillation frequency must be set to a value unique to each optical amplifier, there is a possibility that frequency allocation may be an obstacle when the system is expanded. In addition, it is necessary to prepare an optical amplifier having the same transmission frequency for replacement at the time of failure, and maintenance is difficult. Furthermore, one optical switch is required for each optical amplifier, which causes a high cost.

  In the prior art disclosed in Patent Document 2, since ISO cannot be arranged on the input side, amplification characteristics such as oscillation may become unstable. In addition, since the ALC control is used, the excitation power that arrives is not constant, and it is difficult to determine the threshold value of the power to be determined.

  In the prior art disclosed in Patent Document 3, a maintenance light source is necessary, which causes a high cost.

  The prior art disclosed in Patent Document 4 requires an optical monitoring channel or a data communication network, which makes the structure complicated and expensive. Further, when the signal light is interrupted, information transmission through the optical monitoring channel is impossible.

  Further, as a common problem in the above-described prior art, there is a possibility that an abnormal line switching operation (erroneous switching) may be performed by detecting an abnormal line as well as an interruption as well as an instantaneous interruption.

The present invention has been made in view of the above circumstances, a repeater, an optical transmission system, and an optical transmission system capable of performing line switching and erroneous switching prevention at the time of detecting a failure in an optical transmission system without increasing the scale of the repeater and at low cost. The purpose is to provide a switching method .

To achieve the above object, the present invention provides a first optical amplifier that amplifies an optical signal from a first optical transmission line, and a second optical amplifier that amplifies an optical signal from a second optical transmission line, An optical transmission line on the input side so as to output any one of the optical signal input from the first optical amplifier and the optical signal input from the second optical amplifier to the optical transmission path on the output side And a control unit that controls the switching operation of the optical switch so that the switching operation of the optical switch is performed when the input power from the selected optical transmission line to the optical switch becomes less than a specified value. a repeater having said first or second optical amplifier, when the input signal light from the optical transmission line in which the optical switch is selected blocked, input power which is input to the optical switch is the outputs spontaneous emission light so as not to be less than a specified value Providing a repeater of interruption of the input signal light is the optical switch the optical amplifier is stopped spontaneous emission light output when continued for a predetermined period of time characterized the TURMERIC line switching operation.

In the repeater of the present invention, it is preferable that the time from when the optical amplifier detects the interruption of the input light to when the output of the spontaneous emission light is stopped is set longer than the switching time of the optical switch.
The present invention provides an optical transmission system in which the repeater is provided in multiple stages.

The present invention includes a first optical amplifier that amplifies an optical signal from a first optical transmission line, a second optical amplifier that amplifies an optical signal from a second optical transmission line, and a first optical amplifier. An optical switch for switching the optical transmission path on the input side so that either one of the optical signal input or the optical signal input from the second optical amplifier is output to the output optical transmission path ; Optical transmission provided with multiple stages of control units that control the switching operation of the optical switch so that the switching operation of the optical switch is performed when the input power from the optical transmission line to the optical switch becomes less than the specified value In the system , when the input signal light from the optical transmission line is cut off, the optical amplifier outputs spontaneous emission light, the optical switch and the optical amplifier in the next stage hold the operating state, and the input signal light is cut off. the optical amplifier spontaneous emission light output when continued for a predetermined period of time The next stage of the optical switch is stopped to provide an optical transmission system characterized and TURMERIC line switching operation.

Oite the optical transmission system of the present invention, than the switching time of the optical switch, it is preferable that the optical amplifier is set longer the time from the detection of the input light blocking until stops outputting the spontaneous emission.

The repeater, the optical transmission system, and the switching method thereof according to the present invention provide the spontaneous emission light from the optical amplifier in the operation of switching the line and preventing erroneous switching when detecting a failure in the optical transmission system in which the optical amplifiers and optical switches are arranged in multiple stages. Since it does not require an additional device or line for transmitting the switching information, it can be realized without increasing the scale of the repeater and at a low cost.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram showing an embodiment of an optical transmission system of the present invention. In the figure, reference numerals 1, 2 and 3 are control units, 10, 20 and 30 are relay stations (repeaters), 11, 12, 21, 22, 31 and 32 are optical amplifiers, 13, 23 and 33 are optical switches, 14, 24 and 34 are optical distributors, 15, 25 and 35 are working lines, and 16, 26 and 36 are protection lines.

  The optical transmission system of the present embodiment includes optical amplifiers 11, 12, 21, 22, 31, and 32 that amplify optical signals, optical switches 13, 23, and 33 that switch optical transmission paths, and optical distributors 13, 23, 33 and control units 1, 2, and 3 that control switching operations of the optical switches 13, 23, and 33, the first to third relay stations 10, 20, and 30 are connected to the working lines 15, 25, and 35, and the standby line. The lines 16, 26, and 36 are connected in multiple stages.

  The lines between the relay stations 10, 20, 30 are duplexed by the working lines 15, 25, 35 and the protection lines 16, 26, 36. In the first repeater station 10, the optical signal from the working line 15 is amplified by the optical amplifier 11, and the optical signal from the protection line 16 is amplified by the optical amplifier 12 and input to the optical switch 13. The optical switch 13 has selected the working line 15 and its output is distributed by the optical distributor 14 and then transmitted to the relay station 30 in the next stage.

  In this optical transmission system, when a failure occurs on the transmission line of the working line 15, the control unit 1 performs the switching operation of the optical switch 13 so that the protection line 16 is selected. Is transmitted to the relay station 30 of the stage.

  In the present invention, when an input signal of an optical amplifier is lowered or cut off due to an abnormality in a transmission line, spontaneous emission light (ASE) is output within an input cut-off detection time, and an optical switch and an optical amplifier after the optical amplifier are input. A feature is to prevent erroneous detection of a drop or block of an optical signal, and to stop the output of ASE and perform line switching by an optical switch when the decrease or block of the input signal continues for more than the input cutoff detection time. Yes. Although a momentary interruption occurs due to switching of the optical switch, since the input cutoff detection time of the optical amplifier and the optical switch is set longer than this, erroneous determination can be prevented. Hereinafter, an example of the switching method of the present invention will be specifically described by way of examples.

In the optical transmission system of FIG. 1, the optical amplifier 11 monitors input power and output signal power, and controls the output power to be constant (+20 dBm) regardless of the input power from the work line 15. (FIG. 2A). Therefore, the signal light input power to the optical switch 13 is also constant. At this time, the optical switch 13 determines that the working line 15 is normal and selects the working line 15 because the input power is not less than the specified value P _in1 (= + 17 dBm) (FIG. 2A). The selected optical signal on the working line 15 is distributed by the optical distributor 14 and then transmitted to the relay station 30 at the next stage. If the transmission loss between the relay station 10 and the relay station 30 is 10 dB, the input optical power to the optical amplifier 31 of the relay station 30 is +3 dBm (FIG. 2B).

When a failure occurs in the working line 15 and the signal light input power of the optical amplifier 11 is temporarily reduced or momentarily interrupted and becomes less than P _{in_EDFA} (= _{−6 dBm} ), the optical amplifier 11 is generated by itself. The spontaneous emission power to be _operated is the specified value _{Pout_ASE} (= + 14 dBm) (FIG. 2C). At this time, the optical switch 13 can determine that a failure has occurred in the work line 15 because the input power is equal to or greater than the specified value P _in2 (= + 10 dBm), but keeps the work line 15 selected. When the signal light input power drop or instantaneous interruption of the optical amplifier 11 returns to a normal value (P _{in_EDFA} (= _{−6 dBm} ) or more) within a certain time (= 500 ms), the output constant control of the optical amplifier 11 is also restored. In addition, the input power of the optical switch 13 is also equal to or greater than the specified value P _in1 (+17 dBm) (FIG. 3D).

However, when the signal light input power of the optical amplifier 11 is less than _{Pin_EDFA} ( _{−6 dBm} ) for a certain time (= 500 ms) or longer, the optical amplifier 11 stops the pumping light operation and outputs spontaneous emission light. Is stopped (FIG. 2E). At this time, since the signal light input power of the optical switch 13 becomes less than the specified value P _in2 (= + 10 dBm), the optical switch 13 is switched from the working line to the protection line. At this time, an instantaneous interruption corresponding to the switching time (= 20 ms) of the optical switch 13 occurs (FIG. 2 (f)). The signal light from the selected protection line 16 is transmitted from the relay station 10 to the relay station 30 (FIG. 2 (g)).

When this instantaneous interruption optical signal is input to the optical amplifier 31 of the relay station 30, the optical amplifier 31 outputs spontaneous emission light during the instantaneous interruption (FIG. 2 (h)). Therefore, since the optical input power of the optical switch 33 is equal to or greater than the specified value P _in2 (= + 10 dBm), switching from the working line 35 to the protection line 36 does not occur. In other words, even when an abnormality in the working line 15 is detected in the preceding relay station 10 and the line is switched, the optical amplifier 31 and the optical switch 33 in the succeeding relay station 30 erroneously determine that the working line 35 is abnormal. There is no switching to the protection line 36.

It is a block diagram which shows one Embodiment of the optical transmission system of this invention. It is a figure which shows the result of an Example and shows the case where a signal light input cuts off momentarily and a line is switched. It is a figure which shows the result of an Example and shows the case where a signal light input cuts off momentarily, but a circuit | line is not switched.

Explanation of symbols

  1, 2, 3 ... control unit 10, 20, 30 ... relay station, 11, 12, 21, 22, 31, 32 ... optical amplifier, 13, 23, 33 ... optical switch, 14, 24, 34 ... optical distribution 15, 25, 35 ... active line, 16, 26, 36 ... standby line.

Claims (8)

First a first optical amplifier for amplifying the optical signal from the optical transmission line, a second and a second optical amplifier for amplifying an optical signal from the optical transmission path, light input from the first optical amplifier An optical switch for switching the optical transmission line on the input side so that any one of the signal and the optical signal input from the second optical amplifier is output to the optical transmission line on the output side, and the selected light A repeater having a control unit that controls the switching operation of the optical switch so as to perform the switching operation of the optical switch when the input power from the transmission path to the optical switch becomes less than a specified value ,
The first or second optical amplifier prevents the input power input to the optical switch from becoming less than the specified value when the input signal light from the optical transmission line selected by the optical switch is cut off. outputs spontaneous emission, repeater said optical switch characterized by the TURMERIC line switching operation said optical amplifier is stopped spontaneous emission light output when interruption of the input signal light continues for a predetermined time. 2. The repeater according to claim 1, wherein the time from when the optical amplifier detects interruption of input light to when the output of spontaneous emission is stopped is set longer than the switching time of the optical switch. An optical transmission system in which the repeater according to claim 1 or 2 is provided in multiple stages. First a first optical amplifier for amplifying the optical signal from the optical transmission line, a second and a second optical amplifier for amplifying an optical signal from the optical transmission path, light input from the first optical amplifier An optical switch for switching the optical transmission line on the input side so that any one of the signal and the optical signal input from the second optical amplifier is output to the optical transmission line on the output side, and the selected light an optical transmission system in which a control unit is provided in multiple stages to control the switching operation of the optical switch to perform the switching operation of the optical switch when the input power from the transmission path to the optical switch is less than a specified value ,
When the input signal light from the optical transmission line is cut off, the optical amplifier outputs spontaneous emission light, the optical switch and the optical amplifier in the next stage hold the operating state, and the interruption of the input signal light continues for a predetermined time . optical transmission system next stage of the optical switch, wherein the TURMERIC line switching operation said optical amplifier is stopped spontaneous emission light output when. 5. The optical transmission system according to claim 4 , wherein the time from when the optical amplifier detects the interruption of the input light to when the output of the spontaneous emission light is stopped is set longer than the switching time of the optical switch . An optical switch switching method in the repeater according to claim 1 or 2 ,
The first or second optical amplifier prevents the input power input to the optical switch from becoming less than the specified value when the input signal light from the optical transmission line selected by the optical switch is cut off. outputs spontaneous emission light, the optical switch the optical amplifier is stopped spontaneous emission light output when interruption of the input signal light continues for a predetermined period of time of the optical switch, wherein the TURMERIC line switching operation Switching method. A method for switching an optical transmission system according to claim 3 ,
The first or second optical amplifier prevents the input power input to the optical switch from becoming less than the specified value when the input signal light from the optical transmission line selected by the optical switch is cut off. an optical transmission system and outputting the spontaneous emission light, the optical switch the optical amplifier is stopped spontaneous emission light output when interruption of the input signal light continues for a predetermined period of time characterized the TURMERIC line switching operation Switching method. A method for switching an optical transmission system according to claim 4 or 5 ,
When the input signal light from the optical transmission line is cut off, the optical amplifier outputs spontaneous emission light, the optical switch and the optical amplifier in the next stage hold the operating state, and the interruption of the input signal light continues for a predetermined time . switching method of the optical transmission system of the next stage of the optical switch, characterized the TURMERIC line switching operation said optical amplifier is stopped spontaneous emission light output when.

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