5.2 A3XXX Polarization Controller Operation5.2.1 IntroductionThe operation of the LiNbO3 polarization controller (PC) integrated withthe A3xxx family is comparable to a cascade of five endlessly rotatablewaveplates:PC Input(SMF) PC Output(SMF)l/4 l/4 l/2 l/4 l/4j j j j j0 1 2 3 4The state of the PC is given by the position of the waveplates which isexpressed in terms of five angles ϕ0...ϕ4 measured in rad (ranging from0..π. Due to the internal structure of the PC the waveplates are endlesslyrotatable, i.e. there will be no polarization state transition when turningthe position from 2π back to 0.Note that the retardation may slightly differ from the nominal values de-pending on the operating wavelength and also temperature. Furthermorethere may be a systematic deviation due to the electro-optic properties ofthe LiNbO3 polarization controller. Usually these deviations are not anissue since in most applications the polarization is adjusted in an adaptiveway (like for manual fiber-loop polarization controllers).The angles can either be set statically or dynamically. Dynamic changeis implemented by means of a look-up-table stored in the memory of theinstrument. This look-up-table can be processed once or repeatedly atdifferent clock rates. Triggering or synchronizing with an external clockis also possible.5.2.2 Manual OperationIn manual operation mode the polarization can be adjusted by manuallysetting the five angles ϕ0...ϕ4. The operation is comparable to manualfiber-loop polarization controllers. In the polarizationNAVIGATORTMsoftware settings can be saved and restored.5.2.3 Scrambling OperationIn scrambling mode a polarization fluctuation is created by rotating thewaveplates at different speeds. The step size can be chosen as well as theclock rate.5.2.4 Sequence OperationIn sequence mode a look-up-table given in an ASCII text file can beuploaded to the instrument.5.2.5 Loop Synchronous Operation in Optical Loop Test BedsIn scramble mode and sequence mode the instrument can be synchronizedto external events to support synchronous operation to optical loop testbeds. Two configurations are recommended:A1XXX/A2XXX/A3XXX User Guide 27
