JP2002271269A - Optical transmission system provided with reception level adjusting function, or protection optical switch function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide constitution for absorption of the deviation of level between wavelengths in wavelength multiplexed transmission, corresponding reduction of a light receiver tolerance level, accompanying the speed up of a transmission rate and offering of a spare system opening service in the constitution of rate free optical protection using an optical switch, and to provide a control method. SOLUTION: This system materializes the constitution which is easy of change to protection constitution/spare system opening constitution. The deviation between wavelengths in wavelength multiplexed transmission is absorbed, by inserting a light level adjuster before a high- speed light receiver where the reception tolerance level is low. The protection constitution uses a 2×2 optical switch as a light selector on the reception side and uses the optical switch which performs the selection between an optical bridge and other optical channel connection at spare opening on the transmission side. Accordingly, the optical signal at high transmission rate can be applied to a general wavelength multiplexed transmission system, and also the use of a highly reliable and highly efficient optical channel can be provided flexibly to the optical protection constitution, using the optical switch, too, since the change to the spare system opening constitution is easy, so that this can realize cost reduction of communication service.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a configuration of an optical transmission system to which an optical receiver having a narrow allowable dynamic range is applied and a configuration of an optical transmission system including a redundant system, particularly in wavelength division multiplexed optical fiber transmission.

[0002]

2. Description of the Related Art When wavelength multiplexing optical transmission is used, the transmission capacity per optical fiber transmission line can be increased by using a plurality of optical signals having different wavelengths. An optical signal can be used at a plurality of sites, and communication can be performed between a plurality of nodes while sharing a common optical fiber transmission line.
Generally, when a wavelength-division multiplexed optical signal is transmitted while being relayed between a plurality of nodes, regeneration is performed by an optical amplifier. At this time, there is a deviation in the optical level between wavelengths due to the wavelength dependence of the optical amplifier and optical components. Is generated. In consideration of communication between arbitrary nodes, there has been an event that as the number of relay optical amplifiers increases, the accumulation of the wavelength deviation increases. On the other hand, when the rate of the optical signal to be optically transmitted increases, the signal-to-noise ratio deteriorates in proportion to the increase in the rate, so that a high received optical signal level is required. However, since there is a limit on the maximum allowable optical level of the optical receiver, there is a limitation that as the rate of the optical signal increases, the allowable level of the received optical level narrows. For example, at 2488 Mbit / s, the minimum reception level is -18 dBm and the maximum allowable reception level is
Although the allowable range was -0 dBm and 18 dB, at 9952 Mbit / s, the minimum allowable receiving level was -14 dBm and the maximum receiving level was about -1 dBm, and the allowable range was 13 dB. When wavelength multiplex transmission is not performed at a high optical rate, the allowable width of the optical reception level is narrowed, so that more strict suppression of the wavelength-to-wavelength deviation is required.

In wavelength-division multiplexing optical transmission, it is required to introduce a protection function using a redundant system so that an optical transmission signal can be provided without interruption even when an optical fiber transmission line is disconnected. Conventional optical transmission technology, for example, SD
In a configuration to which H (Synchronous Digital Hierarchy) is applied, a UPSR (Uni-
BLSR (Bi) using four optical fiber transmission lines for directional path switched ring) and bidirectional redundancy
-directional Line Switched Ring). For optical fiber transmission, 155 Mbit / s, 622 Mbit / s, 24
Data transmission is mainly performed from transmission centering on audio signals of 88 Mbit / s and 9952 Mbit / s, and the digital signal format is Ethernet (registered trademark) (1.25 Gbit / s) or Fiber Channel (1602 Mbit / s, 2125 Mbit / s). s) and different signal rates and different protocols must be supported. In various digital signal forms, there has been a demand for a service in a common optical transmission system and a demand for a highly reliable service by a redundant system similar to SDH. Therefore, in order to realize a redundant system independent of a signal rate and a digital signal form in an optical fiber transmission line, a protection configuration using an optical signal combining an optical bridge and an optical switch has been introduced. However, unlike protection by electrical signal switching such as SDH, there is no example in the optical switch configuration in which the standby system is opened for the switching configuration, and there has been no configuration in which the service can be freely selected with the same component configuration. . Further, there has been no consideration on the control problem of freely combining the former narrower optical reception level and the latter redundant system.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical transmission system configuration which is not affected by the wavelength deviation even when the optical signal rate is increased in wavelength division multiplexed optical transmission and the allowable width of the optical reception level is reduced. It is not affected by the wavelength deviation of the wavelength division multiplexing optical transmission system, and at the same time provides fast switching for protection. Provided is an optical transmission system having an optical bridge and an optical switch that can provide a protection function and a standby system opening function using the same configuration in any digital signal form.

[0005]

In a wavelength division multiplexing optical transmission system, even if the optical signal rate is increased and the allowable width of the optical reception level is reduced, the receiving side automatic optical level adjusting optical system is not affected by the wavelength deviation. An attenuator is installed in front of the optical receiver to automatically attenuate an optical input exceeding an allowable optical level to a safety level of the optical receiver by accumulating the wavelength deviation.

As an arrangement for performing high-speed switching for protection without being affected by the wavelength deviation of the wavelength division multiplexing optical transmission system, the receiving side automatic optical level adjusting optical attenuator is provided in two systems, an operating system and a standby system. Instead of inserting
By inserting the protection optical switch immediately before the optical receiver at the subsequent stage, the cost can be reduced by sharing the two systems and the protection of the optical receiver can be enhanced.

In the above configuration, when a failure in the operation system is detected, the light level to the optical receiver is non-destructive even if the automatic light level adjusting attenuator on the receiving side is increased in attenuation and the selection optical switch is switched. Alternatively, after setting the attenuation amount so as to be equal to or lower than the allowable light level, the selection optical switch is switched to the standby system, and then the automatic adjustment operation of the automatic light level adjuster is started, and the predetermined light level is transmitted to the optical receiver. By adopting a protection structure with a reception level adjuster having a sequence to be transmitted, without breaking the optical receiver, without being affected by the wavelength deviation of the wavelength division multiplexing optical transmission, at the same time, a high-speed protection for safe protection Can be switched. In the above processing, the notification of the disconnection detection signal, the notification of the control of the safe attenuation to the optical attenuator, the setting of the attenuation, the notification of the switching of the optical switch, the execution of the optical switch switching, and the start of the automatic adjustment control of the optical attenuator are respectively performed by a number.
This is processing within ms, and switching within 50 ms can be performed safely.

An optical transmitter, an optical receiver, an optical channel inserter,
In a redundant optical transmission system comprising an optical channel splitter, two optical fiber transmission lines, an optical bridge, and an optical switch, a protection system with a function of opening a standby system, wherein a 2 × 2 optical signal is used as an optical switch for selection. With this configuration, the protection function and the standby system release function are realized using the same configuration without depending on the digital signal form in the optical transmission signal. 1 when using the protection function
The optical signal of the optical transmitter is input to the optical input end of one optical coupler bridge having an optical bridge function consisting of two optical couplers and an optical line or two optical couplers, and the optical signal branched by the optical bridge is used for the operation system. Input to the applied optical fiber transmission line and the optical fiber transmission line applied to the standby system. Conversely, on the receiving side, a signal from the optical fiber transmission line as the active system and an optical signal from the optical transmission line as the standby system are received by the 2 × 2 optical switch, and the optical signal of the active system is normally selected and received. To the communication device to form a communication path. When the optical signal in the working system is damaged, the 2 × 2 optical switch is switched to receive the optical signal in the standby system.

In a redundant optical transmission system including an optical transmitter, an optical receiver, an optical channel inserter, an optical channel splitter, two optical fiber transmission lines, an optical bridge, and a select function optical switch, a 2 × 2 optical signal is used. By using an optical switch for selecting one of the output side of the optical coupler for the optical bridge and the standby system open transmission side path, the protection configuration and the standby system open configuration are manually performed. This can be performed automatically without depending on the change of the optical connector.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment will be described with reference to FIG. FIG. 1 shows one node configuration in a two-fiber transmission ring system composed of a plurality of nodes, showing 1 + 1 optical switch protection and a receiving-side automatic optical level controller. FIG. 1 shows a state in which the optical fiber transmission line is disconnected in the normal operation system and switched to the standby system. The operation in a normal state will be described. When the clockwise WDM optical input signal 1-1 inserted at another node is input to the optical signal dropping / inserting function unit 1-3 of the node, an optical channel signal of a specific wavelength is output at the optical signal splitting unit 1-2. Branched, optical protection / reception level adjustment function unit 3-10
Is input to When the counterclockwise wavelength-division multiplexed optical input signal 2-1 inserted at another node is input to the optical signal branching / inserting function unit 2-3 of the node, the optical signal branching unit 2-2 causes the optical signal branching unit 2-2 to transmit light of a specific wavelength. Channel signal is split and optical protection
/ Input to reception level adjustment function unit 3-10. In a normal state, the clockwise signal is used as the operating system and the optical signal branching unit 1-2
Is detected by the clockwise branch signal light monitor 3-1 and transmitted as a clockwise branch signal light monitor signal 3-11 to the optical switch / reception-side optical level controller control unit 3-8. The optical switch / reception-side optical level controller controller 3-8 selects the optical switch control signal 2-15 so that the optical reception signal selection optical switch 3-3 selects the clockwise branch signal.
Is received as a response to the selection optical switch control signal 2-15. Clockwise branch signal light monitor signal 3-11 and selection optical switch control signal 2-15
The first answer indicates that there is an optical signal to the receiver
The start of automatic control is notified to the optical channel receiving side automatic optical level adjustment optical attenuator 3-4 by the first optical channel automatic optical level adjustment control signal 3-13. This is because, when there is no optical input, if the first optical channel receiving side automatic optical level adjustment optical attenuator 3-4 is automatically controlled, the optical attenuator is set to the minimum attenuation, and optical input suddenly enters in that state. And the optical input exceeding the allowable optical input level of the first optical channel optical receiver 4-13 enters and may be destroyed. Therefore, it is confirmed that there is a predetermined optical input level, and optical level control is performed. In order to. Accumulation of wavelength deviation may occur up to 12 dB, and the minimum received optical input may be -9 dB with some margin.
Assuming m, a dynamic range of only 8 dB can be obtained between the maximum allowable level of -1 dBm. For this reason, the receiving-side automatic optical level adjusting optical attenuator 3-4 performs feedback control so as to suppress the optical input above -1 dBm to about -9 dBm.

When the disconnection failure 1-6 occurs, the clockwise branch signal light monitor 3-1 detects the disconnection of the optical input, and generates a clockwise branch signal light monitor signal 3-11 as an optical switch / receiving-side light level controller controller. The input disconnection detection is transmitted to 3-8. The optical switch / reception-side optical level controller controller 3-8 has the first
The first optical channel automatic light level adjustment control signal 3-13 is transmitted to the optical channel receiving side automatic light level adjustment light attenuating section 3-4 so that the attenuation amount becomes a predetermined value or more. Next, the 1 + 1 optical reception signal selection optical switch 3-3 receives the signal 3-12 detected by the anti-clockwise branch signal light monitor 3-2 and detects the standby optical input so that the counterclockwise branch signal is selected. A selection optical switch control signal 2-15 is sent to confirm that switching to the standby system has been set.
Receive 15 answers. In response to the response of the counterclockwise branch signal light monitor signal 3-12 and the selection optical switch control signal 2-15, the first signal in the state where the light signal to the receiver exists exists.
The start of automatic control is notified to the optical channel receiving side automatic optical level adjustment optical attenuator 3-4 by the first optical channel automatic optical level adjustment control signal 3-13. This is because, when there is no optical input at the time of switching and the first optical channel receiving side automatic optical level adjustment optical attenuator 3-4 is automatically controlled, the optical attenuator is set to the minimum attenuation, and in this state, the optical input is reduced. This is because if the optical input suddenly enters, an optical input exceeding the allowable optical input level of the first optical channel optical receiver 4-13 enters and may be destroyed. With the above sequence, it is confirmed that there is a predetermined light input level, and light level control is performed safely.

On the optical signal transmitter side, the optical channel signal from the first optical channel optical transmitter 4-12 of the first optical channel signal section 4-11 is transmitted to the optical protection / reception level adjusting function section 3-10. The signal is input to the first optical channel bridge optical coupler 3-6. The optical channel bridge optical coupler 3-6 separates the optical signals for clockwise and counterclockwise rotation, and the clockwise signal is input via the optical signal insertion section 1-4 and output as the wavelength multiplexed optical output signal 1-5. Is output to the clockwise optical fiber transmission line as a one-wavelength optical signal. The counterclockwise signal is input through the optical signal insertion unit 2-4 and output to the counterclockwise optical fiber transmission line as an optical signal of one wavelength of the wavelength multiplexed optical output signal 2-5.

A second embodiment will be described with reference to FIGS. FIG. 2 shows one node configuration in a two-fiber transmission ring system composed of a plurality of nodes, in which an optical protection configuration with a standby system opening function using a 2 × 2 optical switch operates as a protection function, FIG. 3 shows a configuration in which an optical protection configuration with a standby system opening function using a 2 × 2 optical switch is operated with the standby system opened. The difference from FIG. 1 is that FIG. 1 does not have the function of opening the standby system and has only the function of protection, but the configuration of FIGS. 2 and 3 has a configuration that can also realize the function of opening the standby system. 2 and 3, a 2 × 2 optical switch is used as the 1 + 1 optical reception signal selection optical switch 3-3. 2
The × 2 optical switch can be realized by a bubble type optical switch, a capillary thermo-optical switch, a Maha Zehnder type optical switch, or the like. 2 when using in 1 + 1 optical protection configuration
The first optical channel receiving side automatic optical level adjusting optical attenuator 3-4 is connected to one output of the × 2 selection optical switch, and the output is received by the first optical channel optical receiver 4-13. In some cases, the empty output port can be connected to another receiver to perform digital signal processing and be used for a standby optical quality monitor. The transmitting side optical bridge is equipped with a second optical channel bridge optical coupler 3-7 separately from the first optical channel bridge optical coupler 3-6. However, when the optical bridge is used as a 1 + 1 optical protection configuration, As in the first embodiment, a configuration is used in which the optical transmission signal is divided into clockwise and counterclockwise optical transmission signals using only the first optical channel bridge optical coupler 3-6.

Referring to FIG. 3, a description will be given of a standby system open configuration in an optical protection configuration with a standby system open function using a 2 × 2 optical switch. When the standby system is opened, the optical reception signal selection optical switch 3-3 does not need to use the switching operation, so that each of the optical protection / standby system opening function control units 3-9 fixes the setting to the through state. Thereby, the branch signal from the clockwise optical signal branching unit 1-2 is input to the first optical channel optical receiver 4-13 via the first optical channel receiving side automatic optical level adjusting optical attenuating unit 3-4. Is done. On the other hand,
The branch signal from the counterclockwise optical signal branching unit 2-2 is input to the second optical channel optical receiver 4-23 via the second optical channel receiving side automatic optical level adjustment optical attenuator 3-5. .
The signal light from the first optical channel optical transmitter 4-12 of the first optical channel signal unit 4-11 is input to the first optical channel bridge optical coupler 3-6, but the branch is not used. ,
One of the optical outputs is connected to the optical signal insertion section 1-4, and is transmitted as a one-wavelength optical signal of the clockwise wavelength multiplexed optical output signal 1-5. The signal light from the second optical channel optical transmitter 4-22 of the second optical channel signal section 4-21 is input to the second optical channel bridge optical coupler 3-7, but the branch is not used. And one of the optical outputs is connected to the optical signal insertion unit 2-4, and is sent out as a one-wavelength optical signal of the counterclockwise wavelength multiplexed optical output signal 2-5. The second optical channel bridge optical coupler 3-7 may be a simple jumper optical fiber. By changing the connection of the optical lines of the optical protection / reception level adjusting function unit 3-10 in this manner, the protection configuration and the standby system open configuration can be easily changed.

A third embodiment will be described with reference to FIGS. FIG. 4 shows one node configuration of a two-fiber transmission ring system composed of a plurality of nodes. The configuration of FIG. 2 or FIG. And a protection optical bridge / standby system opening switching optical switch 3-17 for operating the protection function. FIG. 5 shows a structure operating with the standby system open. In FIGS. 2 and 3, when the protection configuration is changed from the protection configuration to the standby system release, the optical fiber connected to the optical signal insertion unit 2-4 is connected to one of the optical output ports of the first optical channel bridge optical coupler 3-6. It was necessary to change the connection to the second optical channel bridge optical coupler 3-7. On the other hand, in FIGS. 4 and 5, the optical protection / standby system opening function control unit 3-9 sends the 1 + 1 optical reception signal selection optical switch 3-3 to the fixed through state and the protection optical bridge / standby system opening. The switching optical switch 3-17 is automatically protected by setting the optical switch so that the signal from the second optical channel bridge optical coupler 3-7 is connected to the optical signal insertion unit 2-4. The standby system open configuration can be changed from the configuration.
Conversely, when changing from the standby system configuration to the protection configuration, the setting can be reversed to automatically change between the protection configuration and the standby system configuration without human intervention.

[0016]

According to the present invention, a general wavelength division multiplexing transmission system can be used even when the rate of an optical transmission signal becomes high and the allowable reception level becomes narrow, and an optical protection configuration using an optical switch is provided. Since it is easy to change to a standby system open configuration, it is possible to flexibly provide highly reliable and highly efficient use of an optical channel, thereby reducing the cost of communication services.

[Brief description of the drawings]

FIG. 1 Configuration of 1 + 1 optical switch protection and automatic optical level adjuster on the receiving side

FIG. 2 shows an optical switch protection configuration in an optical protection configuration with a standby system opening function using a 2 × 2 optical switch.

FIG. 3 shows a standby system open configuration in an optical protection configuration with a standby system open function using a 2 × 2 optical switch.

FIG. 4 shows an optical switch protection configuration in an optical protection configuration with an automatic standby system opening function using a 2 × 2 optical switch and an optical bridge with optical switch switching.

FIG. 5 shows a standby system release configuration in an optical protection configuration with an automatic standby system release function using a 2 × 2 optical switch and an optical bridge with optical switch switching.

[Explanation of symbols]

1-1: Clockwise WDM optical input signal, 1-2: Optical signal branching unit, 1-3: Optical signal branching / insertion function unit, 1-4: Optical signal insertion unit, 1-5: Clockwise wavelength division multiplexing Optical output signal, 1
-6: disconnection failure, 2-1: counterclockwise WDM optical input signal, 2-2: optical signal branching unit, 2-3: optical signal branching / inserting function unit, 2-4: optical signal inserting unit, 2 -5: counterclockwise WDM optical output signal, 3-1: clockwise branch signal light monitor, 3-2: counterclockwise branch signal light monitor, 3-3: 1
+1 optical reception signal selection optical switch, 3-4: first optical channel reception side automatic optical level adjustment optical attenuator, 3-5: second optical channel reception side automatic optical level adjustment optical attenuator, 3-6:
1st optical channel bridge optical coupler, 3-7: second
3-8: Optical switch / reception-side optical level controller controller, 3-9: Optical protection / standby system release function controller, 3-10: Optical protection / reception level adjustment function 3-11: Clockwise branch signal light monitor signal, 3-12: Counterclockwise branch signal light monitor signal, 3-13: First optical channel automatic light level adjustment control signal, 3-14: Second signal Optical channel automatic optical level adjustment control signal, 3-15: optical switch control signal for selection, 3-16: optical protection configuration / standby system open configuration setting control signal, 3-17: optical bridge for protection
/ Standby system release switching optical switch, 4-11: first optical channel signal section, 4-12: first optical channel optical transmitter, 4
-13: first optical channel optical receiver, 4-21: second optical channel signal section, 4-22: twelfth optical channel optical transmitter, 4-23: second optical channel optical receiver

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ryuji Ishii 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in the Communications Division, Hitachi, Ltd. 2K002 AA02 AB04 BA13 DA08 HA11 5K002 BA02 CA08 DA02 DA09 EA33

Claims (6)

[Claims] 1. An optical fiber transmission line comprising a plurality of nodes, comprising an optical transmitter, an optical receiver, an optical channel inserter, an optical channel splitter, and an optical amplifier having at least one wavelength in a wavelength division multiplexing optical transmission system. Optical transmission system characterized in that a receiving-side automatic optical level adjusting optical attenuator is inserted between a receiving-side optical channel splitter and an optical receiver in a wavelength multiplexing optical transmission system having 2. An optical transmitter, an optical receiver, an optical channel inserter,
In a redundant optical transmission system including an optical channel splitter, two optical fiber transmission lines, an optical bridge, an optical switch for selection, and an automatic optical level adjusting optical attenuator on the receiving side, 2 × 1 or 2 × 2 light is transmitted to the optical switch for selection. An optical transmission system having a protection configuration with a reception level adjuster, wherein a switch is applied and one optical coupler is used for an optical bridge. 3. An optical transmission system having a protection configuration with a reception level adjuster according to claim 1, wherein a receiving-side automatic optical level adjustment optical attenuator is inserted between an optical switch for selection and an optical receiver. 4. An optical system according to claim 3, wherein when a failure in the operation system is detected, the optical level to the optical receiver is changed even if the amount of attenuation of the automatic optical level adjusting attenuator on the receiving side is increased and the selection optical switch is switched. After setting the attenuation so that it is below the non-destructive level or the permissible light level, the selection optical switch is switched to the standby system, and then the automatic adjustment operation of the automatic light level adjuster is started, and the predetermined light level is adjusted. Optical transmission system having protection configuration with reception level adjuster having sequence transmitted to optical receiver 5. An optical transmitter, an optical receiver, an optical channel inserter,
In a redundant optical transmission system comprising an optical channel splitter, two optical fiber transmission lines, an optical bridge, and an optical switch, a protection system with a function of opening a standby system, wherein a 2 × 2 optical signal is used as an optical switch for selection. Optical transmission system having configuration 6. An optical transmitter, an optical receiver, an optical channel inserter,
In a redundant optical transmission system including an optical channel splitter, two optical fiber transmission lines, an optical bridge, and a select function optical switch, a 2 × 2 optical signal is used as an optical switch for selection, and one of the optical couplers for the optical bridge is used. An optical transmission system having a protection configuration having an automatic standby system opening function, characterized by using an optical switch for selecting an output side and a standby system opening transmission side path.