OPA_FAIL_INDI appears because of no configuration on Rated Optical Power

For one ROADM NE, after configuring XC(LSX-->FIU), OPA_FAIL_INDI alarm appeared on 5-LSX board.The signal flow is:
LSX-->MR2-->WSMD2-->OBU-->FIU 
The engineer checked the channel attenuation on WSMD2 board. it is coming to threshold 15 dB for added 5-LSX board. 

OPA_FAIL_INDI alarm

1.check the the optical power of 5-LSX.  LSX(OUT)= -0.8dBm according to the performance. 
2.check the rated insertion loss is 1.5dB from ADD to OUT of MR2.
:cfg-get-wastage:1-1,0 
                                    OPA-WASTAGE                                   
                              BID      PORT    WASTAGE                             
                              1-1        1              15                                 
                              1-1        2              15                                 
                              1-1        3              10                                 
                              1-1        4               0                                   
  Total records :4                 
3.check WSMD2 rated attenuation(AM-->OUT)=3.8dB          
:cfg-get-wastage:1,0 
                                    OPA-WASTAGE                                   
                              BID      PORT    WASTAGE                             
                              1           1               0                                   
                              1           2              32                                 
                              1           3              38                                 
                              1           4               0                                   
                              1           5              31                                 
                              1           6              46                                 
                              1           7               -1                                 
                              1           8               -1          
4.check the the rated optical power of 7-OBU101, it's NULL.
:cfg-get-goalpow:7,0,0 
failed! cmd:0x8e72 error:0x9706 NSERR_CFG_GET_NULL       
5.So we ensure the cause is no configuration of the rated optical power of 7-OBU101.
6.the rated optical of OBU101 should be -20dBm for 40 waves system.
Description=OptiX OSN 6800,TN11OBU101,C-BAND Optical Booster Unit(MAX -4dBm IN and 16dBm OUT,Gain 20dB) 
-4-10lg40＝-20dBm 
7.After configuring -20dBm for the rated optical power of 7-OBU101,the OPA_FAIL_INDI alarm disappeared.
-0.8-1.5-3.8-(-20)=13.9dB

We ensure the signal flow: 5-LSX-->101-MR2-->1-WSMD2-->7-OBU101;
In general,OPA calcuate the VOA atenuation according to the rated insertion loss of WSMD2 (AM-->OUT) and MR2 (ADD－>OUT) , the optical power of LSX-OUT and the rated optical power of OBU101.
We need acquire these data to calculate the VOA attenuation. If the value is higher than 15dB,OPA_FAIL_INDI alarm will be reported.

OPA need to calculate according to the rated optical power of OA board. So before using the OPA function,please configure the correct rated optical power of OA board at first.