Abstract: The disclosure relates to a method (30) for radio bearer release performed in a base station node (2) of a communication system (5). The base station node (2) provides one or more radio bearers to a user equipment (1), and the communication system (5) comprises a serving gateway (4). The method (30) comprises: receiving (31) an error message from the serving gateway (4), the error message indicating a faulty radio bearer; awaiting (32), for a delay time, additional error messages indicating faulty radio bearers; and releasing (33) the one or more radio bearers being indicated as faulty.

Abstract: The disclosure relates to a method (30) for radio bearer release performed in a base station node (2) of a communication system (5). The base station node (2) provides one or more radio bearers to a user equipment (1), and the communication system (5) comprises a serving gateway (4). The method (30) comprises: receiving (31) an error message from the serving gateway (4), the error message indicating a faulty radio bearer; awaiting (32), for a delay time, additional error messages indicating faulty radio bearers; and releasing (33) the one or more radio bearers being indicated as faulty.

Abstract: In an optical fiber network bidirectional WDM traffic is sent on one optical main transmission fiber (1) between two nodes (A, B) connected in the path of the transmission fiber. The bidirectional traffic between a pair of nodes is carried on two different wavelength channels (Nos. 1, 2), one for each direction. The two wavelength channels are added to/dropped from the traffic in the ring fiber (1) in each node using a two-channel add/drop filter (5e1-2, 5w1-2), e.g. a band add/drop filter. In this way the number of add/drop filters connected in the path of the transmission fiber can be kept as small as possible.

Abstract: An optical WDM ring network includes at least two add/drop nodes connected in a ring path. The ring path comprises only a single optical fiber arranged for bidirectional traffic between the nodes. A 2×2 switch is used in one of the add/drop nodes for switching signals forwarded from the node to the other node to travel either on a first segment of the ring path or on a second, complementary segment of the ring path when required for protection purposes. Signals from the other node to the first node are issued to travel on both segments but the switch selects the actual segment from which the signals are received in the first node. The signals switches by the switch can be high priority signals used in protected channels communicated between the node and another node. On the segment from which the high priority signals are not received, low priority signals in non-protected channels can be communicated between the nodes, these channels also passing the switch.

Abstract: A broadcast and select ring network for optical WDM communication includes two parallel fiber rings (1a, 1b) carrying traffic in opposite directions between nodes (3; A, B, C, D). The nodes comprise on their receive side selecting means such as a cross connect device (21) or similar means allowing a flexible selection of the wavelength channels which are to be received by each node. Thereby, any WDM channel in the rings can be selected and received in the nodes. For example, all nodes can receive signals in the same channel for e.g. set up or reconfiguration purposes. Furthermore, the number of receivers in a node can be small but still all channels can be received. The number of transmitters in each a node can also be small since every transmitter can reach every receiver.

Abstract: A node is provided in an optical communications network that utilizes a first set of add/drop filter elements for extracting and combining optical signals that are carried on wavelength division multiplexed channels in a first wavelength band. Additionally, an extraction element and a combining element for dropping and adding a service channel associated with the wavelength division multiplexed channels. The extraction element is arranged downstream of the add/drop filter elements. The extraction and combining elements are additionally adapted to drop and add, respectively, at least one further wavelength band carrying at least one optical traffic data channel.

Abstract: Devices (13.1, 31.1) communicate with each other on a wavelength channel using wavelength specific signals on a working WDM fiber (21) having a parallel protection WDM fiber (23). An SDH system (13.S, 31.S) uses one channel of the WDM system of the fibers as one of the fibers of the working pair of the SDH system and has a separate fiber (37) constituting that fiber of the protecting fiber pair for the SDH-system. To provide an unambiguous or predictable protection behaviour for the SDH system for the case of the working WDM fiber being cut the RETs (29.1, . . . , 29.S) have two modes. In the first mode a RET will be on and always carry traffic when the input power is high enough. In the second mode a RET they will not automatically turn on again after it has first lost the input signal and thereupon the input signal has returned. The RET can then be manually restarted or restarted after some suitable delay. Then the sequence of events will always be unambiguously defined.

Abstract: Wavelength drift in an optical WDM system between wavelengths launched by lasers (110) and received at a demultiplexer (50) can lead to disturbance of traffic signals if not identified and rectified rapidly. It is proposed to identify wavelength drift by determining a difference in temperature of the demultiplexer (50) for each channel between an actual temperature and a temperature for optimal transmission of the channel. The mean of these temperature differences for all channels is indicative of wavelength drift, while each difference is utilised to determine whether an individual channel is drifting in wavelength and to correct the drift. Wavelength drift can be detected and corrected whether sourced at a laser (110) or due to a temperature variation at the demultiplexer (50). Measurement and control can be performed during normal operation without impeding or degrading traffic flow. Wavelength influencing parameters other than temperature can be utilized.

Abstract: An optical network comprises a bidirectional link connecting two nodes (1) through two optical fibers (3). Optical output signals from optical transmitters (7) in a node are provided to transponders (11) issuing optical signals of well-defined wavelengths to a power combiner (13), from which optical signals are forwarded to the other node on the respective fiber. The network can have protection for failures of various components. Thus, a spare transponder (21) can receive the optical output signals of an optical transmitter (7) in the case of a failure of an ordinary transponder (11). The spare transponder (21) is also connected to the combiner (13). The optical transmitters (7) and receivers (9) can be duplicated by providing spare transmitters (7?) and spare receivers (9?). Various arrangements can be used for connecting the output of a transmitter to an ordinary transponder or the spare transponder.

Abstract: An optical WDM ring network includes at least two add/drop nodes connected in a ring path. The ring path comprises only a single optical fiber arranged for bidirectional traffic between the nodes. A 2×2 switch is used in one of the add/drop nodes for switching signals forwarded from the node to the other node to travel either on a first segment of the ring path or on a second, complementary segment of the ring path when required for protection purposes. Signals from the other node to the first node are issued to travel on both segments but the switch selects the actual segment from which the signals are received in the first node. The signals switches by the switch can be high priority signals used in protected channels communicated between the node and another node. On the segment from which the high priority signals are not received, low priority signals in non-protected channels can be communicated between the nodes, these channels also passing the switch.

Abstract: A broadcast and select ring network for optical WDM communicationincludes two parallel fiber rings (1a, 1b) carrying traffic in oppositedirections between nodes (3; A, B, C, D). The nodes comprise on their receive side selecting means such as a cross connect device (21) or similar means allowing a flexible selection of the wavelength channels which are to be received by each node. Thereby, any WDM channel in the rings can be selected and received in the nodes. For example, all nodes can receive signals in the same channel for e.g. set up or reconfigurationpurposes. Furthermore, the number of receivers in a node can be smallbut still all channels can be received. The number of transmitters in eacha node can also be small since every transmitter can reach every receiver.

Abstract: An optical WDM network for use for instance in a larger e.g. meshed network is the hubbed type and comprises parallel fiber ring paths (1b), a hub (3h) and satellite nodes (3A, 3B, 3C) connected in the ring path. Client equipments are connected to the hub and the satellite nodes. A client equipment connected to the main node can communicate with a client equipment connected to any of the satellite nodes, using a number of wavelength channels equal to the number of client equipments in the satellite nodes. The wavelength channel used for transmission from the hub can e.g. be fixed or selected by a tunable optical transmitter (31). The WDM transmitters (9) in the satellite nodes transmits light signals in a fixed one of the wavelength channels to the fiber ring path. A single band drop filter (35) is arranged in the main node to receive the light signals from the satellite nodes.

Abstract: An optical communication line having optical fiber amplifiers including a pump laser can be configured to suppress the transmission of optical signals by reducing the power of the pump laser. In order that the portion of the line downstream of the amplifier can be monitored for fiber breaks causing only negligible crosstalk with a parallel working line, and with the elimination of the risk of mistaking reflections from a working line for light emitted by the standby amplifier, the light emitted by the standby amplifier is modulated by a low frequency control tone. The modulated laser light causes modulation of the amplified spontaneous emission (ASE) generated in the amplifier to create a control tone. Monitoring means disposed at the end of the optical line detect this control tone and use this as the criteria for a functional connection downstream the amplifier.

Abstract: In an optical fiber network bidirectional WDM traffic is sent on one optical main transmission fiber (1) between two nodes (A, B) connected in the path of the transmission fiber. The bidirectional traffic between a pair of nodes is carried on two different wavelength channels (Nos. 1, 2), one for each direction. The two wavelength channels are added to/dropped from the traffic in the ring fiber (1) in each node using a two-channel add/drop filter (5e1-2, 5w1-2), e.g. a band add/drop filter. In this way the number of add/drop filters connected in the path of the transmission fiber can be kept as small as possible.

Abstract: An optical fiber network of WDM type comprises two fibers which carry light signals propagating in opposite directions and which are arranged in a ring configuration. One standby link between two neighboring nodes is inactive but is made active if an active link fails. An add and drop node used in the network has band blocking filters connected in a fiber between a drop coupler and an add coupler, taking out a share of the light power in each direction to be received through bandpass filters in receivers and adding new wavelength channels produced in transmitters, respectively. Switches are used for receiving and transmitting on the wavelength channels in correct directions. The positions of the switches can be changed when the inactive link has to become one of the two active links directly connected to the node. A very efficient use of the wavelength channels in the network can then be achieved for nodes having a minimum of in-line components, and particularly, a minimum of in-line filtering components.

Abstract: The present invention is a method to protect a cross-connect OXC/OEXC used to forward at least one signal AB from a main input IN to a main output OUT. Said method comprises the following step: dividing the at least one signal AB into two substantially identical signal parts, a first signal part A and a corresponding signal part B; routing the at least one first signal part A through a first cross-connect OXC1/OEXC1, from the input IN to the output OUT; detection of a failure affecting the at least one first signal part A; interruption of the routing path for the at least one first signal part A; routing the at least one corresponding signal part B through a second cross-connect OXC2/OEXC2, from the input IN to the output (OUT).

Abstract: Devices (13.1, 31.1) communicate with each other on a wavelength channel using wavelength specific signals on a working WDM fiber (21) having a parallel protection WDM fiber (23). An SDH system (13.S, 31.S) uses one channel of the WDM system of the fibers as one of the fibres of the working pair of the SDH system and has a separate fibre (37) constituting that fibre of the protecting fibre pair for the SDH-system. To provide an unambiguous or predictable protection behaviour for the SDH system for the case of the working WDM fibre being cut the RETs (29.1, . . . , 29.S) have two modes. In the first mode a RET will be on and always carry traffic when the input power is high enough. In the second mode a RET they will not automatically turn on again after it has first lost the input signal and thereupon the input signal has returned. The RET can then be manually restarted or restarted after some suitable delay. Then the sequence of events will always be unambiguously defined.

Abstract: The present invention relates to an optical system with an optical amplifier having at least one input and output, a control circuit for controlling the output power of the amplifier with the aid of an output process demand signal (PD) from a control means. The control circuit comprises control means, a detector block and a means for tapping off light from an input or an output of the optical amplifier to the detector block. According to the invention, at least one check signal (A) is disposed to be sent in at least one check signal channel which passes through the optical amplifier. The detector block is configured to measure the amplitude of the control signal(s).

Abstract: The present invention relates to an arrangement and a method for detecting faults in an optical fiber network, comprising at least two nodes arranged with at least two optical fibers to a bus with the end nodes connected via two spare fibers. Every node comprising a central module (50), at least two protection switches (60,61) and optical amplifiers (21,22,23,24) and said central module comprising at least one central processor (51), at least one logical unit (52), at least one protection signal transmitter (53) and at least one protection signal monitor (54). The end nodes of the bus transmit a protection signal in at least one direction of the bus and said end nodes can detect the own protection signal and the protection signal transmitted from the other end node. All nodes in the bus can detect Optical Power Loss, OPL. The bus will reshape into new end nodes in case of a fault.

Abstract: An optical node in an optical network includes transmitters (Tx:1-3) and receivers (Rx:1-3) adapted to particular wavelength channels and arranged to communicate via the optical bus network, with receivers and transmitters for corresponding wavelength channels in other nodes. The node includes optical safety switching devices (S1-S5) in connection with the transmitters (Tx:1-3) and receivers (Rx:1-3) of the node, so that the transmitters (Tx:1-3) and receivers (Rx:1-3) can be switched from a first optical fiber (1,2) to a second optical fiber (1,2).