  The flat spectrum radio quasar CTA 102 entered an extended period of activity
from 2016 to 2017 during which several strong $\gamma$-ray flares were
observed. Using Fermi large area telescope data a detailed investigation of
\gray spectra of CTA 102 during the flaring period is performed. In several
periods the \gray spectrum is not consistent with a simple power-law, having a
hard photon index with an index of $\sim(1.8-2.0)$ that shows a spectral cutoff
around an observed photon energy of $\sim(9-16)$ GeV. The internal $\gamma$-ray
absorption via photon-photon pair production on the broad-line-region-reflected
photons cannot account for the observed cut-off/break even if the emitting
region is very close to the central source. This cut-off/break is likely due to
a similar intrinsic break in the energy distribution of emitting particles. The
origin of the spectral break is investigated through the multiwavelength
modeling of the spectral energy distribution, considering a different location
for the emitting region. The observed X-ray and $\gamma$-ray data is modeled as
inverse Compton scattering of synchrotron and/or external photons on the
electron population that produce the radio-to-optical emission which allowed to
constrain the power-law index and cut-off energy in the electron energy
distribution. The obtained results are discussed in the context of a diffusive
acceleration of electrons in the CTA 102 jet.
