Abstract: An optical patch panel section is made turnable in a double-door manner, whereby workability in coupling an optical fiber to an optical connector is improved. Eventually, a compact design is provided. Owing to the compact design, a communication chassis can be loaded in the same area in a rack as an area in which an optical transmission device is stored. Not only when a network is constructed but also when a channel is switched to another because a transmission line has to be relocated due to a change in the route of the transmission line occurring after the network is constructed, or when the quality of the transmission line is varied, light level adjustment work or light dispersion adjustment work can be easily achieved from one place on the front side of the chassis.

Abstract: A bi-directional line switched ring network system including a plurality of optical fiber communications lines and a plurality of nodes connected by the plurality of optical fiber communications lines forming a closed circuit. Each of the nodes performs an addition and a drop of a path between an external communications apparatus and the optical fiber communications lines or permits the path on the optical fiber communications lines to pass through, or performs a change of a direction of the path. A control unit is located in each of the nodes to control the addition, the drop, the pass-through and the direction change of the path. When the path passes through each of the nodes, the control unit sets a time slot number of the path in being inputted into the node and a time slot number of the path in being outputted from the node independently of each other.