Interesting issue raised by Muhammad Boron., However the topics relating to the usage of BER test set in place of BER analyzer have been discussed previously in some of the earlier posts. Any of these might be beneficial to you. I think you have to check the components property of the BER test set before you can actually read the received BER information.
https://optiwave.com/forums/topic/how-do-we-connect-bre-analyzer-to-a-dp-qpsk-reciever/ and several others.
enjoy!!!