The low frequency noise of optoelectronic coupled devices (OCDs) was measured in the system designed and constructed by the authors. The RTS noise was observed in some devices. The analysis of RTS noise in time and frequency domains is presented. The values of fRTS were found from spectrum and from observed RTS noise on the base of tup and tdown evaluation. The results of evaluations were compared. The dependencies of tup, tdown and fRTS on values of Id were described.