Telefonaktiebolaget Lm Ericsson (publ)

Cisco Technology, Inc.

Cisco Systems (sweden) Aktiebolag

Cisco Systems (sweden) Ab

Lars Egnell

Bengt Johansson

Dag Bonnedal

Fredrik Lindgren

Ola Hulten

Robert Batchellor

Anders G Djupsjobacka

Nigel Robert Wood

Magnus &Ouml;berg

Fredrik Linden

Fredrik Liden

A receiver transponder to be used in an optical add and drop multiplexer connected in short haul type networks receives light signals from two opposite directions on input fibers (). The optical input signals are converted to electrical signals by O/E converters (). The output terminals of the converters are connected to an electronic switch () which handles protection switching in a protected ring type network. The output of the switch can be monitored () before, it enters a reshaping circuit () in which the signal is reshaped, cleansed from a supervisory channel and given a proper drive level for a following laser (). The optical signal from the laser can travel a significant distance through a fiber () to a client receiver or sustain other forms of attenuation and still have a sufficient signal power for reliable detection. An electrical output signal can be provided () by the reshaping circuit. The converters can be used to protect for one another and to detect channel signal power and a supervisory channel at electric outputs (). The laser can be a low cost type since the laser is typically used for transmitting light over only moderate distances and the input signal is amplified and reshaped. The electric high frequency switch is generally more reliable and can be more easily monitored than a purely optical switch.

Receiver transponder for protected networks

A receiver transponder that is implemented in an optical add/drop multiplexer (OADM) is disclosed. The OADM is used in short haul type networks and receives light signals from two opposite directions on input fibers (). The optical input signals are converted to electrical signals by optical-to-electrical (O/E) converters (). The output terminals of the converters are connected to an electronic switch (), which provides protection switching in a protected ring type network. The output signal of the switch can be monitored () before the signal enters a reshaping circuit (), where the signal is reshaped, filtered from a supervisory channel, and adjusted to a proper drive level for a laser (). The optical signal from the laser can travel a significant distance through a fiber () to a client receiver or sustain other forms of attenuation and still have sufficient signal power for reliable detection. An electrical output signal can be provided () by the reshaping circuit. The converters can be used to protect for one another and to detect channel signal power and a supervisory channel at electric outputs (). The laser can be a low cost type since the laser is typically used for transmitting light over only moderate distances. The electric high frequency switch is generally more reliable and can be more easily monitored than a purely optical switch.

An add/drop node of an optical WDN-network which has two fiber paths for light of a plurality of channels propagating in opposite directions comprises two add/drop modules () for each of the channels. All the modules are identically constructed. Each module comprises an add device () for adding light to one of the paths and a drop device () for deflecting a portion of light from a second one of the paths. A module comprises a house () enclosing the add device and the drop device. A first fixed connector () is attached to the house for connection in the first path and to a an optical fiber () which extends freely from the house and has a first free connector () at its free end to be attached to the fixed connector of a neighboring add/drop module for continuing the first path through the considered add/drop module to the neighboring module. In the same way a second fixed connector is attached to the house for connection in the second path and to a second optical fiber which extends freely from the house and has a second free connector at its free end to be attached to the fixed second connector of a neighboring add/drop module for continuing the second path through the considered add/drop module to the neighboring module.

Connection of on an add/drop node

A system and a method for maintaining operation of a signaling interconnection between a first ring network and a separate second ring network. Each ring network comprises two communication paths transmitting data in opposite directions and at least two nodes connected to both communication paths. The networks are interconnected via two adjacent gateways, which receive data from the two communication paths on one network, and transmit the data onto the other network directed away from the other gateway. Data traffic is stopped in both directions in an inactive segment on each ring network, so that a node situated on a ring network receives traffic from only one of the two gateways.

Method and a system for interconnecting ring networks

An add/drop node used in an optical network having two fiber paths for carrying light corresponding to a plurality of channels in opposite directions may include a pair of add/drop modules that correspond to one of the plurality of channels. This arrangement advantageously provides a simple approach for connecting the components of an add/drop node.

Connection of an add/drop node

A receiver transponder that is implemented in an optical add/drop multiplexer (OADM) is disclosed. The OADM is used in short haul type networks and receives light signals from two opposite directions on input fibers ( ). The optical input signals are converted to electrical signals by optical-to-electrical (O/E) converters ( ). The output terminals of the converters are connected to an electronic switch ( ), which provides protection switching in a protected ring type network. The output signal of the switch can be monitored ( ) before the signal enters a reshaping circuit ( ), where the signal is reshaped, filtered from a supervisory channel, and adjusted to a proper drive level for a laser ( ). The optical signal from the laser can travel a significant distance through a fiber ( ) to a client receiver or sustain other forms of attenuation and still have sufficient signal power for reliable detection. An electrical output signal can be provided ( ) by the reshaping circuit. The converters can be used to protect for one another and to detect channel signal power and a supervisory channel at electric outputs ( ). The laser can be a low cost type since the laser is typically used for transmitting light over only moderate distances. The electric high frequency switch is generally more reliable and can be more easily monitored than a purely optical switch.

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.

Optical WDM network having an efficient use of wavelengths and a node therefor

A communications network comprising at least two nodes is disclosed. The network has two communication paths that carry traffic in opposite directions and work as a bi-directional bus. The network has a first inactive segment that carries no traffic and is arranged to allow the first inactive segment to be made active and another segment to be made inactive, especially in the case of fault in the other segment. The activation and inactivation logically &ldquo;move&rdquo; the first inactive segment. Additional protection paths are provided between the nodes.

Communications network and an add and drop node

An optical fiber network of WDM type comprises two fibers which carry light signals propagating in opposite direction and which are arranged in a ring configuration. In the ring, one standby link between two neighboring nodes is used if another link fails. An add and drop node, used in the network only for traffic between neighboring nodes, has band blocking filters connected in respective fibers between a drop coupler and an add coupler. A drop coupler takes out equal shares of the light power to be received through simple switches and bandpass filters in receivers. An add coupler adds new wavelength channels produced in transmitters in the node through multiplexers and simple switches. The switches are used for receiving and transmitting on the wavelength channels in correct directions depending on the location of the inactive link. Thus, the positions of two of the switches have to be changed when the inactive link is one of the two links directly connected to the node. Such a node has a minimun of in-line components, and particulary, a minimum of in-line filtering components.

Add and drop node for an optical WDM network having traffic only between adjacent nodes

A system and a method for dispersion compensation in fiber optic high speed systems, the dispersion compensation being carried out in the transmitter. The system comprises a modulating device for modulating an information-carrying electric signal, an equalizing device for equalizing the signal modulated in the modulation device, and an electro-optic translating device for translating the signal equalized in the equalizing device into an optical signal substantially without loss of information and with substantially maintained phase and amplitude properties.

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Saltsjöbaden, Sweden

Lars Egnell