sentences:  Due to much lower attenuation and interference, optical fiber has large advantages over existing copper wire in long-distance, high-demand applications.However, infrastructure development within cities was relatively difficult and time-consuming, and fiber-optic systems were complex and expensive to install and operate.Due to these difficulties, fiber-optic communication systems have primarily been installed in long-distance applications, where they can be used to their full transmission capacity, offsetting the increased cost.