Customized Bit Error Rate (cBERT) Tester for Characterizing Frequent Fade Communications Channels

Abstract

Standard bit error rate test (BERT) equipment can be inadequate in characterizing free space optical (FSO) communications channels due to frequent fades caused by turbulence effects. Though FSO channels can have high percentage throughput, the BER statistics are dominated by errors from short duration fades with many cases causing lengthy pattern re-synchronization of the traditional BERT. We describe a custom BERT (cBERT) that is optimized to provide statistics with bit-level error accuracy for faded channels. In addition to traditional BER statistics, the cBERT provides histogram statistics of error-free blocks in bins of 1 µs – 100 s to characterize error distributions, channel throughput, and packet error rates for efficient network protocol design. Results of a 10 Gbps FSO test using the cBERT are presented.