Tektronix 071-0590-00 GB700/ GB1400 Optical Component Test, Fiber Optic Link Test Example

Application Example

GB700/ GB1400 Optical Component Test

gB-Series Tx	gB-Series Rx
	Clock
Data	Clock	Data

Fiber Optic

Clock Recovery

and

Retiming

Fiber Optic Link Test Example

A typical BERT application is measuring the error performance of the electrical- to-optical (E/O) and optical-to-electrical (O/E) output modules of a fiber optic transmission system, as shown in the diagram above. Not all fiber optic links are designed for extremely high speed. For example, many data communications LANs use FDDI at 133 Mb/s. Serial digital video links operate at 270 Mb/s.

External Clock input shown on the BERT Tx would be used to provide jittered clock to stress Clock Recovery (CR) circuit.

Longer PRBS patterns, such as 223 might be used to test DC wander susceptibility of the CR subsystem.

Peak-to-peak amplitude and level offset of the BERT Tx output may be varied to determine acceptable operating range for the DUT input circuitry.

Tests may be made using short and long fiber cables to be able to specify maximum allowable length of fiber runs.

Note that in this application, it may be an advantage to be able to separate the BERT Tx and Rx. Using the BERT internal PRBS generator makes it easy to assure that the Tx and Rx have the same data for error comparison.

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