The Agilent N7785B is a high-speed Synchronous Scrambler. It contains a polarization controller plus microcontroller based driving circuitry. This unit can operate in various modes as synchronous scrambler, SOP switch and traditional scrambler.
As Synchronous Scrambler the device switches the SOP of the output signal in a (pseudo) random way. Switching of the SOP occurs within few microsconds.
The SOP is stable for a predefined time until it again switches to a new SOP.
An electrical trigger input can be used to synchronize the scrambler with external events.
The results obtained in re-circulating loop experiments depend heavily on the PMD and PDL properties of the loop. Loop synchronous polarization scrambling schemes have proven to be necessary for generating results comparable to deployed systems.
The Agilent N7785B is ideally suited to provide the synchronous scrambling capability in such experiments.
This is a key capability to provide realistic change of polarization from cycle to cycle around the loop, while providing a stable SOP during passage of the bit train through the scrambler.
This avoids the unrealistic effect caused by continuous scramblers, which is a rapid change of the polarization during the bit train.