Abstract: In order to realize the efficient detection of remote multiple nodes and reduce the cost, a distributed feedback semiconductor laser working at special central wavelength was shared and placed at a local control node being connected to each remote detection node with bi-directional fiber links in series. Furthermore, a novel distributed optical fiber gas sensor system was designed by using the special structure of remote nodes and fiber segments. At each detection node, the gas cell was added between two Y-couplers. There were the upstream signal and the downstream signal in the system, which could avoid the influences of the signals from other nodes and implement time division multiplexing directly. The numerical calculation and experiments were carried out in a 3-node methane detection system. The results show that the proportion of the laser diode in the total cost drops from about 60% to about 38%. When the loop number is increased, the relative error of the measured gas density at each node can be reduced, and particularly the relative error at the first node can be reduced to below 0.2% or even lower. Distributed sensing with a shared light source can be achieved efficiently.