A model is constructed for the Raman effect as responsible for the sel
f-frequency shift of solitons. The effect is related to and compared w
ith the measured Raman gain in silica fibers. The model is quantized a
nd includes the thermal and the quantum noise of the optical phonons g
enerating the Raman effect. It is shown that the Raman effect causes e
xcess noise for ultrashort pulses and limits the squeezing of subpicos
econd solitons.