Tektronix 071-0590-00 user manual Bert Basics GB1400, Example, Bert Application

Functional Overview

BERT Basics - GB1400

The GB1400 Generator and Analyzer together comprise a 1400 Mb/s, serial, bit error rate test system or BERT.

A BERT is an instrument designed to measure the bit error rate (BER)—or more generally, the error performance—of a digital communications device, module, or system.

A typical BERT application, for example, would be to measure the error performance of the electrical-to-optical (E/O) and optical-to-electrical (O/E) output modules of a high-speed fiber optic transmission system (FOTS), as shown in the figure below.

GB1400 Generator

CLOCK DATA

OUT OUT

GB1400 Analyzer

CLOCK DATA

IN IN

E/O

O/E

Figure 2-1. Example, BERT Application

The GB1400 is described as a serial BERT because it is designed to test one digital path at a time. The term serial also distinguishes the GB1400 from parallel BERTs, such as the Tektronix MB100, which is designed to test multiple digital signal paths simultaneously.

The GB1400 Generator, also known as the transmitter or "Tx", can generate various test patterns, including pseudo-random bit sequences (PRBS) and user- defined word patterns. The Generator output consists of a two level, non-return to zero (NRZ) data signal and its associated clock signal, as illustrated in Figure

2-2. In the NRZ format, the data signal remains at either a logic "1" or logic "0" level for the entire duration of each bit time slot, except for a small transition period between time slots containing different data. The corresponding clock signal is a nominal "square wave" whose frequency defines the bit rate of the test signal.

2-2 GB1400 User Manual