The fiber Bragg grating (FBG) has a huge capacity in optical communication, especially for showing optical multistability, which can be used in optical switching and optical memories. In this paper, we numerically solve the coupled mode equations governing the uniform FBG and obtain the output shapes of the bright and dark solitons as input pulses with different amplitudes. This paper shows that we can reach different output shapes using identical input shapes with different amplitudes. Hence we can control the output light waveform using light as the controlling input. For signal processing purposes, it is made clear that the input pulse characteristics, such as amplitude and shape, are distinguishable applying only the output shape. Also, we can predict the length of the FBG. The deliverables of this article will facilitate generating light pulses with application to optical fiber digital communication systems.