Client-side 1+1 protection uses two wavelengths: one is the working wavelength, and the other is the protection wavelength. The two wavelengths adopt diverse routing to transmit signals to protect the OTU and the OCh fibers.
Trigger Conditions
The trigger conditions for the client 1+1 protection automatic switching are as follows:
In the case of the OptiX OSN 3800A/6800A/8800 T16 (NA)/8800 T32 (NA)/8800 T64 (NA):
- The board is offline, including the following situations: removing or cold resetting the board.
- There is a signal failure (SF) condition. SF includes the following board-side alarms: LOF, LOS, LOC, OTU-LOF, OTU-LOM, OTU-AIS, ODU-AIS, ODU-OCI, ODU-LCK, ODU-LOFLOM, REMC-SF.
- There is a signal degraded (SD) condition. SD includes the following board-side alarms: SF-S, OTU-DEG, OTU-EXC, ODU-DEG, ODU-EXC, REMC-SD, IN-PWR-HIGH, IN-PWR-LOW.
NOTE: IN-PWR-HIGH and IN-PWR-LOW are valid for LWXS board.
In the case of the OptiX OSN 1800 (NA):
- The board is offline, including the following situations: removing or cold resetting the board.
- When the input power difference between the working channel and protection channel crosses the 5 dB threshold, the board side reports the corresponding alarm, that is, OPR-DIFF-OVER.
- There is a signal failure (SF) condition. SF includes the following board-side alarms: LOF, LOS, ODU-AIS, ODU-OCI, ODU-LCK, OTU-AIS, OTU-LOF.
- There is a signal degraded (SD) condition. SD includes the following board-side alarms: SF-S, ODU-DEG, ODU-EXC, OTU-DEG, OTU-EXC.
Working Principle
Client-side 1+1 protection is in three types.
- Intra-subrack client 1+1
This protection is utilized when the working OTU and the protection OTU are in the same subrack of an NE. The SCS board is recommended for this type of protection.
- Inter-subrack client 1+1
This protection is utilized when the working OTU and the protection OTU are in different subracks of an NE. The OLP or DCP board must be used for this type of protection.
- Inter-NE client 1+1
This protection is utilized when the working OTU and the protection OTU are in different NEs. The OLP or DCP board must be used for this type of protection.
NOTICE: In the case of the OptiX OSN 6800A/3800A, the client 1+1 protection and VLAN SNCP cannot be configured at the same time for the L4G and TBE board.
The three types share similar protection principles. The difference lies in that the positions of the working and protection OTU boards are different.
When the SCS board is used, the system selects signals by enabling or disabling the client-side laser of the working or the protection OTU board. When the OLP or DCP board is used, the client-side lasers of the working and protection OTU boards are enabled. In this case, the system selects signals by using the SCC board to control the OLP or DCP board. Figure 1shows the principle with the client 1+1 protection as an example.
For the description of the working principle of the SCS, OLP and DCP boards, refer to the Hardware Description.
 : Direction of the working signal flow |
 : Direction of the protection signal flow |
NOTE: - The SCS board communicates with the OTU through the backplane. This communication is not indicated in Figure 1.
- The OptiX OSN 8800 T64 (NA)/8800 T32 (NA)/8800 T16 (NA)/6800A/3800A support the same client 1+1 protection in terms of working principle and application. The difference lies in that the OptiX OSN 8800 T64 (NA)/8800 T32 (NA)/8800 T16 (NA)/6800A uses the optical multiplexing/demultiplexing unit while the OptiX OSN 3800A uses the optical add/drop multiplexing unit.
- In the transmit direction, the SCS board at the transmitting end splits each signal into two channels. Then it sends them to the working OTU (OTU1) and the protection OTU (OTU2). The working signals and the protection signals are transmitted to the receiving end respectively through the working route and the protection route.
- In the receiving direction, the SCS at the receiving end controls the OTU1 and the OTU2 based on the detection information reported by the OTU. The laser of the client-side optical interface where the working channel of OTU1 is located works normally, whereas the laser of the client-side optical interface where the protection channel of OTU2 is located is shut down. Only the signals transmitted by the working wavelength channel are sent to the client-side equipment.
- When the OTU1 at the receiving end detects a channel of signals is faulty, that trigger the switching, the SCC board directs the OTU1 to shut down the corresponding client-side laser. The client-side laser of the OTU2 for this channel is enabled. Thus, for this channel of services, only the signals transmitted by the protection wavelength route are sent to the SCS board. All the other channels of signals are not switched to the protection wavelength route. They are still transmitted by the working wavelength route.
- After the recovery of the working wavelength route, service signals transmitted by the protection wavelength route can be switched back to the OTU1 or not based on the revertive mode configured on the NMS.
- When a protection switching occurs, only a part of the client-side services are switched to the protection OTU. Other client-side services are not affected. As a result, there is no need to switch the services.
- When a channel of client signal received by the working OTU fails, only this channel is switched. There is no switching at the WDM side.
- The working OTU in the opposite end shut down the client-side transmit laser for this failed channel. The protection OTU at the opposite end turns on the corresponding client-side transmit laser. The other normal signals are still transmitted through the working OTU.