We have investigated experimentally different operational states of an all-normal-dispersion ytterbium-doped fiber (YDF) ring laser with a long cavity. Various operational states were obtained by adjusting a polarization controller (PC) and the pump power. Self-pulsing, bright pulses, dark-bright pulse pairs and their harmonic mode locking (HML) counterparts, as well as dark pulses and their HML counterparts have all been obtained. Numerical simulations reproduce well the formation processes of dark pulses and dark-bright pulse pairs.