EXFO PSO-200 Optical Modulation Analyzer - Manual (Page 114)

Bit Pattern Analysis and the Gearbox
106 PSO-200
Obtaining and Using Bit/Symbol Error Rates
The application displays a BER for each polarization of the system,
according to the Gearbox configuration, as shown below. The application
computes a BER for each input stream.
Similarly, the SER is calculated as the number of error symbols / total
number of symbols. A current burst SER and a total SER are measured for
each polarization.
The following example shows the difference between BER and SER:
1 symbol = 4 bits (16-QAM)
Provided stream: 0101 1010 0100 1011
Measured stream: 0100 1010 0111 1011
BER = 3/16 = 0.1875; SER = 2/4 = 0.5
One global stream N individual streams Dual X-Y streams