Embodiments herein describe a fiber array unit (FAU) configured to couple a photonic chip with a plurality of optical fibers. Epoxy can be used to bond the FAU to the photonic chip. However, curing the epoxy between the FAU and the photonic chip is difficult. As such, the FAU can include one or more optical windows etched into a non-transparent layer that overlap with epoxy wells in the photonic chip. Moreover, the FAU may include a transparent substrate on which the non-transparent layer is disposed that permits UV light to pass therethrough. As such, during curing, UV light can be pass through the transparent substrate and through the optical windows in the non-transparent layer to cure the epoxy disposed between the FAU and the photonic chip.