Abstract: The invention has for its object to provide a network in which an optimized mode of operation is made possible both in the trouble-free case and on the occurrence of a disturbance. This object is attained by a network (NET) which is implemented with nodes (HUB2) as claimed in claim 1.

Abstract: The invention has for its object to provide a network in which an optimized mode of operation is made possible both in the trouble-free case and on the occurrence of a disturbance. This object is attained by a point-to-multipoint network (NET) which is characterized in that it comprises two nodes (HUB3, HUB4) which are designed as subcenters, are connected to the center (HE) via respective main trunk lines, and make the signals received from the center (HE) available on reserve lines. By activating the reserve lines only if disturbances are present on the main trunk lines, power can be saved. The occurrence of a disturbance in a main trunk line is detected autonomously by each node concerned. In this manner, the nodes can control the reception and forwarding of the signals autonomously and independently of additional control equipment, such as a central switching assembly, and the reserve line is activated only on the occurrence of a disturbance.

Abstract: An optical switching unit is disclosed which permits switching from faulty components to standby components in optical transmission systems. A component in this connection may be a transmit laser or an optical fiber, for example. The optical switching unit (OSE) according to the invention contains an n×m optical space switch (ORS) whose ports (P1A . . . PNA; P1B . . . PMB) are monitored by photodiodes (M1A, M1B). The photodiodes provide a control unit (SE) with information as to whether and, if so, what signals are arriving at the ports. The control unit (SE) controls the position of the optical switch (ORS) in accordance with program instructions. The switching unit controls itself, i.e., incorporation of a higher-level control center is not necessary. It thus allows very short switching times and has many applications; it is particularly suitable for use in modular optical transmission systems.

Abstract: A network element (NE) of an optical communication system includes of a chassis into which different modules (D1-D3, S1-S8, X1-X12) and at least one auxiliary module (DS, SS) can be inserted, wherein the modules are optically connected via optical waveguides. Some of the modules (D1-D3, DS, S1-S8, SS) include at least one laser. There is also provided a method automatically testing these optical connections by sequentially switching the lasers of the modules (D1-D3, DS, S1-S8, SS) off and on, and by measuring on the subsequent modules with the help of detectors (DET) which are located in the modules (S1-S8, SS, X1-X12) and have optical inputs (PORT1, PORT2), whether a signal loss has occurred. A memory in the network element (NE) can also include a program module which can be implemented in a control device with a microprocessor, for executing the test method.