EFFECT OF ACTIVE FIBRE STABILIZATION ON GROUP AND PHASE DELAY

Many current optical timing schemes use detection of the pulse group or phase delay through an optical fibre to allow them to stabilize propagation through the fibre to the fs or sub-fs scale. However, it is recognised that stabilizing one leaves a residual drift in the other. We have contructed a phase delay detector to investigate the phase-group delay walk-off (PGW) in fibre distribution systems. The phase monitor uses polarisation rotation associated with sub-wavelength delays in the fibre to detect changes in the carrier phase of ultrashort pulses. Used in conjunction with a group delay monitor, we can measure the PGW in actively stabilized fibre links and its implications on the feasibility of stabilizing both carrier and envelope phase in pulsed synchronisation systems. The ability to stabilize both the carrier and envelope phase in these systems could give the higher resolution of interferometric based stabilization systems while continuing to deliver ultrashort pulses for use at delivery sites.