We discuss the quantum theory of self-phase modulation as applied to optical fibers. We use a formalism that does not rely on a cavity and thereby resolves some anomalous length dependences present in earlier studies. We show that the exact expectation values and variances can be evaluated without the need for linearizing about a classical pump wave. The standard quantum equations for self-phase modulation are generalized in order to remove singularities in some expectation values whose origin is the instantaneous response time approximation.