  In this paper, we characterize the performance of relay-assisted underwater
wireless optical code division multiple access (OCDMA) networks over turbulent
channels. In addition to scattering and absorption effects of underwater
channels, we also consider optical turbulence as a log-normal fading
coefficient in our analysis. To simultaneously and asynchronously share medium
among many users, we assign a unique optical orthogonal code (OOC) to each user
in order to actualize OCDMA-based underwater network. The most significant
challenge in underwater optical communication is in the ability to extend the
short range of its coverage. In order to expand the viable communication range,
we consider multi-hop transmission to the destination. Moreover, we evaluate
the performance of a relay-assisted point-to-point UWOC system as a special
case of the proposed relay-assisted OCDMA network. Our numerical results
indicate significant performance improvement by employing intermediate relays,
e.g., one can achieve $32$ {dB} improvement in the bit error rate (BER) of
$10^{-6}$ using only a dual-hop transmission in a $90$ {m} point-to-point clear
ocean link.
