The current cone beam computed tomography (CBCT) system on the small animal radiation research platform (SARRP) is less effective in localizing soft-tissue targets. On the contrary, molecular optical imaging techniques, such as bioluminescence tomography (BLT) and fluorescence tomography (FT), can provide high contrast soft tissue images to complement CBCT and offer functional information. In this study, we present a dual-use optical imaging system that enables BLT/FT for both on-board and stand-alone applications. The system consists of a mobile cart and an imaging unit. Multi-projection optical images can be acquired in a range of -90°∼90° angles. An optical fiber driven by an X-Y-Z Cartesian stage serves as an excitation light source specifically for FT. Our results show that the accuracy and reproducibility of the system meets the requirements set by the pre-clinical workflow (<0.1 mm and 0.5 degree error). Preliminary experiments demonstrate the feasibility of bioluminescent imaging in a tissue-simulating phantom with a luminescent source embedded. In a considerable light-tight environment, we can achieve average background optical intensity significantly lower than the luminescent signal (< 5%).