The periodic perturbations to the soliton in passively mode-locked fiber soliton lasers cause dispersive wave shedding, which lead to sharp spectral sidebands that limit pulse duration. By using a broad intracavity birefringent plate filter, the side-bands are greatly reduced, and the pulse duration is shortened. The filter also allows wavelength tuning, and a 43 nm continuous tuning range is demonstrated for pulses of 311-357 fs duration in a fully self-starting diode pumped system.