  We have investigated the transport properties of an insulating
sub-micrometric YBa2Cu3O7-d bridge, patterned on a thin film. As expected for a
variable-range-hopping insulator, transport is found non linear. The reduced
dimension allows for the observation of an individual fluctuator generating
random telegraph noise, which dynamics could be explored as a function of the
temperature and transport current. Some recordings clearly exhibit three levels
fluctuating resistance, with comparable level separation and correlated
dynamics, which likely result from the existence of two states or correlated
clustered charge traps.
