Abstract : General relativity describes gravity as a deformation of space-time. Applied to the Universe as a whole, it explains well cosmological observations in the lambda-CDM paradigm. However, at the Planck scale, the theory is not anymore self-consistent. It is most probably necessary to include quantum effects. For a century, this has been considered as one of the main challenges for theoretical physics. This is however an extremely difficult aim to reach and this thesis is devoted to one of the main proposal: Loop Quantum Gravity. To go ahead in the construction of any quantum theory of gravity, it would be most useful to compare predictions with observations. To this aim, we have studied cosmological perturbations in this framework. We have investigated into the details the phenomenological consequences of loop quantum cosmology corrections in a bouncing universe. A Fisher analysis was carried out to compare the predictions with future data. For the other modes, we have used a specific formalism to include counterterms that prevent anomalies from appearing in the algebra of constraints. This formalism was applied to vector and scalar perturbations. The gauge-invariant equations of motion leading to the calculation of measurable spectra were derived.