Hi Kanwarjeet,
Bit error test set (BERTs) are a common feature in many test labs either as BER measuring devices, or as test pattern sources for other measurements. The two most common classes are: High Speed BERTs, typically used in design and manufacturing of high-speed components and the early phases of design of boards and systems.
The BER Test Set (BERT) performs the direct error counting for one or more sweep iterations of a defined sequence length of bits. From this data it is possible to determine the bit error rate (BER) for each iteration and the running average of BERs. BER data is also provided for X, Y and X+Y polarization channels.
Prior to performing the BER analysis of a system, it’s important to determine if guard bits and leading/trailing zeros will be needed.
For more details about Bit error test set (BERTs), you can also refer to optisystem component library pdf file.
Hope this will help you