The fiber Bragg gratings (FBGs) with Kerr nonlinearity exhibit optical soliton like phenomena known as the Bragg solitons. Due to the high dispersion of FBGs near the band edge, optical solitons in the anomalous dispersion side is produced when the input pulse has suitable pulse-width and peak intensity. The Bragg solitons belong to the class of bi-directional pulse propagation problems. In this paper, general quantum theory for bi-directional pulse propagation problems is developed and applied to the Bragg solitons. The output Bragg soliton pulses are quantum-mechanically squeezed and their squeezing ratios calculated.