when I verify the PRBS CHECKER function of DS250DF410, some issue can't fix.

1: Directly connected TX and RX of DS250DF410, find that bit error of checker is zero,that's fine.But connect TX to optical module TX ,and optical module RX to DS250DF410' RX , the optical module just optical loopback  .  The checker always have bit error,that abnormal. The optical module is OK ,I have already confirmed,and I get the optical RX to other BERT , no bit error.

2: So I want to optimize the DS250DF410 register configure,I change the channel register 0x39 then reset CDR and release CDR ,next I find that CDR can't be lock,0x78 always 0x20. I keep try many times by different sequence  0X39 CDR RESET CDR  release, no work.Below register configure is one of kind

       for example MCU_WIICS 0 0x4E 0xFF 0X1 0X01

MCU_WIICS :write the register 0x4E :the device address, 0xFF :the register address     0X01 : number of write  0x01 : the value be  written in  regiter 

for example MCU_RIICS 0 0x4E 0x83 0X1         

MCU_RIICS :read the register 0x4E :the device address, 0x83 :the register address     0X01 : number of read

MCU_WIICS 0 0x4E 0xFF 0X1 0X01

MCU_WIICS 0 0x4E 0xFC 0X1 0X08

MCU_WIICS 0 0x4E 0x00 0X1 0X04
MCU_WIICS 0 0x4E 0x0A 0X1 0X0C
MCU_WIICS 0 0x4E 0x2F 0X1 0X58
MCU_WIICS 0 0x4E 0x39 0X1 0X65
MCU_WIICS 0 0x4E 0x0D 0X1 0X00
MCU_WIICS 0 0x4E 0x79 0X1 0X43
MCU_WIICS 0 0x4E 0x30 0X1 0X08
MCU_WIICS 0 0x4E 0x30 0X1 0X18
MCU_WIICS 0 0x4E 0x30 0X1 0X08
MCU_WIICS 0 0x4E 0x0A 0X1 0X00
MCU_WIICS 0 0x4E 0x82 0X1 0X40
MCU_WIICS 0 0x4E 0x82 0X1 0X00
MCU_WIICS 0 0x4E 0x82 0X1 0X80
MCU_RIICS 0 0x4E 0x83 0X1
MCU_RIICS 0 0x4E 0x84 0X1
MCU_WIICS 0 0x4E 0x82 0X1 0X00

my issue is that about How to optimize  RX , After cdr reset and release,cdr is no-lock ,please correct my configure make DS250DF410  work normal

Summary

      my optical module ,TX work normal, DS250DF410  TX and RX Electric loopback no bit error, optical RX to other BERT no bit error,just optical module RX to DS250DF410  always have bit error

Test condition is 25.78Gbps PRBS31