To meet the urgent demand for high-performance photodetectors in emerging solar-blind ultraviolet communication applications, this study systematically designs and implements a fully transparent β-Ga₂O₃ solar-blind photodetector based on a back-illumination architecture. The device is fabricated using RF magnetron sputtering to epitaxially grow high-quality β-Ga₂O₃ films (~300 nm in thickness, ~4.98±0.05 eV in bandgap) on double-polished sapphire substrates, with indium tin oxide (ITO) interdigitated electrodes forming efficient quasi-Ohmic contacts with n-type Ga₂O₃. The core advantage of this design lies in exploiting the high deep-UV transmittance of double-polished sapphire substrates, enabling incident photons to completely bypass the UV-absorbing ITO electrodes and eliminate photon loss caused by electrode shadowing effects in traditional front-illumination configurations. Consequently, the device demonstrates exceptional optoelectronic performance: a maximum responsivity of 0.46 A/W corresponding to an external quantum efficiency of 222.4%, an outstanding UV/visible rejection ratio of 1.2×10⁴, a minimum noise equivalent power of 1.52 pW/Hz^1/2, and a peak specific detectivity of 1.39×10¹¹ Jones, with fast response times of 24 μs (rise) and 1.24 ms (decay). Building on this high-performance detector platform, we further explore its multifunctional application potential by constructing a polarization detection system that utilizes the intrinsic lattice anisotropy of monoclinic β-Ga₂O₃, and successfully demonstrating a non-line-of-sight (NLOS) UV communication system that validates high-fidelity information transmission in complex scattering channels. This work provides effective physical insights and experimental basis for developing next-generation Ga₂O₃-based optoelectronic devices with integrated high sensitivity, polarization resolution, and NLOS communication capabilities, showing promising applications in secure communications and polarization imaging.