Function Implementation

The intra-board 1+1 protection utilizes the dual fed and selective receiving function of the OLP and OTU, diverse routing scheme to protect service.

The intra-board 1+1 protection can be generally classified into two types:

The intra-board 1+1 protection realized by dual fed and selective receiving OTU.
The intra-board 1+1 protection realized by dual fed and selective receiving OLP or DCP board working with the OTU boards without the dual fed and selective receiving function.

In the case of the OptiX OSN 3800A/6800A/8800 T16 (NA)/8800 T32 (NA)/8800 T64 (NA):

For the intra-board 1+1 protection realized by dual fed and selective receiving OLP or DCP working with the single-fed and single receiving OTU, it can be divided into common mode and extended mode. The difference between the common mode and extended mode lies in that, besides the OLP or DCP, the latter applies the OTU as its monitoring unit, which enables it to detect the electrical layer alarms.

Trigger Conditions

In the case of the OptiX OSN 3800A/6800A/8800 T16 (NA)/8800 T32 (NA)/8800 T64 (NA):

The trigger conditions for the intra-board 1+1 protection realized by dual fed and selective receiving OTU automatic switching are as follows.

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.
There is a signal degraded (SD) condition. SD includes the following board-side alarms: SF-S, OTU-DEG, OTU-EXC, ODU-DEG, ODU-EXC, IN-PWR-HIGH, IN-PWR-LOW.
NOTE:
IN-PWR-HIGH and IN-PWR-LOW are valid for LWXS board.

The trigger conditions for the intra-board 1+1 protection realized by dual fed and selective receiving OLP or DCP board working with the OTU boards without the dual fed and selective receiving function automatic switching are as follows.

For the common mode, the trigger condition of automatic switching is signal failure (SF).
- The input power loss exceeds the threshold. The board-side alarm is LOS.
- The variance between primary and secondary input power exceeds the threshold. The board-side alarm is OPR-DIFF-OVER.
  NOTE:
  - The threshold of input power loss is -35 dBm by default.
  - The variance threshold between primary and secondary input power is 5 dB by default.
For the extended mode, the trigger condition of automatic switching are as follows.
- There is a signal failure (SF) condition. SF includes the following board-side alarms:
  - OTU board-side alarms: LOF, LOS, LOC, OTU-LOF, OTU-LOM, OTU-AIS, ODU-AIS, ODU-OCI, ODU-LCK, ODU-LOFLOM.
  - OLP or DCP board-side alarms:
    - The input power loss exceeds the threshold. The board-side alarm is LOS.
    - The variance between primary and secondary input power exceeds the threshold. The board-side alarm is OPR-DIFF-OVER.
- There is a signal degraded (SD) condition. SD includes the following OTU board-side alarms: SF-S, OTU-DEG, OTU-EXC, ODU-DEG, ODU-EXC.

In the case of the OptiX OSN 1800 (NA):

The trigger conditions for the automatic switching of the intra-board 1+1 protection realized by the OTU with the dual fed and selective receiving function or the OLP with the dual fed and selective receiving function are as follows:

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.
SF: The board side reports the LOF, LOS, ODU-AIS, ODU-OCI, ODU-LCK, OTU-AIS, and OTU-LOF.
SD: The board side reports the SF-S, SD-S, OTU-DEG, OTU-EXC, ODU-DEG, and ODU-EXC.

Working Principle

Intra-board 1+1 protection adopts dual fed and selective receiving and unidirectional switching in linear networks and ring networks. In a linear network, the OTU intra-board 1+1 protection is similar to optical line protection and both of them need diverse routing at adjacent stations. In a ring network, the OTU intra-board 1+1 protection uses diverse routing of the ring network, that is, the services travel clockwise or anticlockwise in the ring to reach the destination node.

There are two types of intra-board 1+1 protection.

It uses dual fed and selective receiving OTU to realize client service protection. (for 2.5 Gbit/s OTU)
It uses dual fed and selective receiving OLP or DCP to realize client service protection. (for 5 Gbit/s, 10 Gbit/s and 40 Gbit/s OTU)

Figure 1 takes the ring network as an example to show the working principle of the intra-board 1+1 protection realized by dual fed and selective receiving OTU.

Figure 1 Working principle of Intra-board 1+1 protection (OTU)

: Direction of the working signal flow

: Direction of the protection signal flow

In the transmitting direction, the OTU that has the dual-fed signal selection function divides the client-side services into two at the WDM side and feeds the signals into the east OADM and the west OADM. Signals are transmitted to the receiving end by different optical routes.
In the receiving direction, the corresponding OTU detects the signals coming in east and west directions. If the signals in the working route are normal, the working signals are chosen by the OTU and sent to the client side.
When the OTU at the receiving end detects any failure in the working signals, the protection signals are chosen by the OTU and sent to the client side.
After the recovery of the working wavelength route, service signals can be switched back to the working route or not based on the revertive mode configured on the NMS.

Figure 2 takes the ring network as an example to show the working principle of the intra-board 1+1 protection realized by dual fed and selective receiving OLP or DCP. For the working principle of the OLP and DCP, refer to the Hardware Description.

Figure 2 Working principle of intra-board 1+1 protection (OLP)

: Direction of the working signal flow

: Direction of the protection signal flow

In the transmitting direction, the OLP or DCP board that has the dual-fed signal selection function divides the incoming client signals and feeds the signals into the east OADM and the west OADM. Signals are transmitted to the receiving end by different optical routes.
In the receiving direction, the corresponding OLP or DCP at the receiving end detects the signals coming in east and west directions. If the signals in the working route are normal, the working signals are chosen by the OLP or DCP and sent to the client side.
When the receive-end OTU detects that the signals of the working wavelength route are abnormal, the OLP selects and sends the protection signals to the client-side equipment.
When a LOS alarm of the working channel occurs or when the optical power difference between the working channel and the protection channel crosses the threshold, the protection signals are chosen by the OLP or DCP and sent to the client side.
In the extended mode, the OTU board further detects the signals that the OLP/DCP board selectively receives. If the OTU finds switching triggering alarms, protection switching occurs.
After the recovery of the working wavelength route, service signals can be switched back to the working route or not based on the revertive mode configured on the NMS.