Square-core optical fiber has been proposed recently for high optical power delivery in industrial processing tools with core size larger than 400×400 μm2. In this work, we first study the possibility of significantly reducing the core side to single-mode condition (i.e. 9×9 μm2) at optical communication wavelength. In the proposed square-core single-mode-fiber (SC-SMF), high bandwidth-distance product and low bending loss are achieved. We also discuss the fabrication of the SC-SMF. After this, the bending losses of the SC-SMF and standard single mode fiber (SSMF) are analyzed and compared. Finally, 10 Gb/s signal transmission using conventional on-off keying (OOK) and orthogonal frequency division multiplexing (OFDM) passing through 200 m, 500 m and 1 km SC-SMFs are performed. Negligible power penalty is observed. We believe that this can be another choice of high bending tolerance fiber which is simple to manufacture.