All-fiber passively Q-switched lasers were demonstrated using ytterbium-doped double cladding fiber (YDF) as an active medium. The laser was pumped by three 25W, 975nm fiber coupled diodes and Q-switching was initiated when the amplified spontaneous emission generated in the core of the gain fiber bleached the saturable absorber (SA). A piece of samarium-doped fiber was used as SA in first configuration and pulses with 68μJ pulse energy and 210ns pulse width were obtained. In second configuration, a piece of ytterbium-doped fiber with much smaller core size was used as SA to produce pulse energy of 86μJ. The last configuration incorporated a 9m-long YDF as gain fiber. The far end from pump was acting as SA in this case and pulses with 82μJ pulse energy and 148ns pulse width were observed. The peak power was estimated at 554W. Traveling wave model was implemented to numerically simulate the output characteristics versus pump power.