<p>Sensor networks are indispensable for diverse engineering applications and cutting-edge scientific research. Recent advances in cavity optomechanics have enabled progress in ultrasensitive sensing. Crucially, the resonant enhancement of optical and mechanical responses enables highly sensitive detection of small perturbations, making it a promising candidate for next-generation ultrasensitive sensor networks. However, the intrinsic limitations of existing optomechanical sensors-such as fiber-optic integration and polarization-dependent response- have hindered progress in this field. Here, we demonstrate a kilometer-scale optomechanical sensor network, integrating multiple fiber-optic optomechanical sensors into a standard single-mode fiber. Leveraging commercially available fiber Bragg gratings, we achieve robust, low-loss, low-noise, and polarization-insensitive coupling with light sources. Within this network, which incorporates both scalar and vector magnetometers, we illustrate the network operation by resolving the spatial variations in the magnetic field under a magnetically unshielded environment with the ambient temperature and pressure. Our work advances the practical application of cavity optomechanics in ultrasensitive sensor networks.</p>