The olfactory bulb has one source of sensory input (axons from olfactory receptor neurons, and one output (mitral cell axons). It is thought that it functions as a filter. However, the olfactory bulb also gets "top-down" information from brain areas like the amygdala, neocortex, hippocampus, locus coeruleus, and substantia nigra.[1][2]
Its range of functions probably include:
discriminating between odors
enhancing sensitivity of odor detection
filtering out background odors
permitting higher brain areas involved in arousal and attention to modify the detection or discrimination of odors.
References
↑Scott J.W. et al 1993. Functional organization of the main olfactory bulb. Microsc. Res. Tech. 24 (2): 142–56. [1]
↑Linster, Christiane & Cleland, Thomas 2013. Spatiotemporal coding in the olfactory system. 20 Years of Computational Neuroscience. 9: 238. [2]