A　ytterbium-doped　large　mode　area　PCF　sub-picosecond　laser　oscillator　and　amplifier　system　is　experimentally　studied.　The　oscillator　which　combines　NPE　and　SESAM　is　operating　on　the　all-normal-dispersion　regime　and　the　LMA　PCF　is　used　as　the　gain　medium.　In　the　CW　mode-locking　regime,　the　oscillator　directly　generates　the　pulse　at　the　repetition　rate　of　83.7　MHz　while　the　pulse　duration　is　960　fs.　The　double-clad　fiber　amplifier　system　directly　generates　a　high　average　power　of　12.53　W　with　a　pulse　duration　of　4.1　ps　corresponding　to　the　pulse　energy　of　150　nJ　and　peak　power　of　36.6　KW　after　about　3　m　ytterbium　doped　double　clad　fiber　amplification.