Bragg gratings were written in H2-loaded polarization- maintaining fiber (PM-FBGs) and inserted in an actively mode-locked Er-doped fiber laser. The use of PM-FBG in sigma laser cavity allows to effectively build all polarization- maintaining fiber laser. Long term stabilization of the laser was ensured by a feedback loop that controlled the cavity length. Peak wavelengths, reflection bandwidths and reflectivity values of the grating were equal to 1545.5 nm and 1540.5 nm, 1.6-nm and 0.8-nm, of 99% and 90%, respectively. At a 3-GHz repetition rate, pulses of 9.4-ps and 27.9-ps duration were generated with first and second gratings, respectively. By inserting additional long piece of dispersion-shifted fiber in the cavity, nonlinear pulse shortening was observed due to formation of average soliton inside the cavity. In this case, pulses of 7.8-ps and 22.7- ps duration were generated with first and second gratings, respectively. With the first grating, generated pulses were close to transform limit for hyperbolic secant pulse shape. Longer pulse duration obtained with second grating is attributed to narrower bandwidth and residual chirp of the grating.