The fringe envelope in a single channel (or pixel/column) is rather wide due to the narrow bandwidth. Below we show the interferometric signal of channel I1 of pixel 50 over several scanning periods. The EWS commands are also shown.

f=midigui() ; Select fringe track file
spawn,getenv('vltiCbin')+'/oir1dCompressData "'+f+'" '+getenv('prismhmask')+' outf'
df=oirgetdata('outf')
!p.multi=[0,1,2]
plot,df.data1(50),/ynozero,xrange=[2000,2200]
plot,df.localopd(0)*1e6,xrange=[2000,2200],ytitle='OPD [microns]'