초록 ▼

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 o

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.

대표청구항 ▼

1. A node arranged to be connected in a network and for communication only with adjacent nodes, the network including a ring configuration including two optical fibers each carrying light signals in one direction, the direction being opposite each other and links connecting adjacent nodes, an inacti

1. A node arranged to be connected in a network and for communication only with adjacent nodes, the network including a ring configuration including two optical fibers each carrying light signals in one direction, the direction being opposite each other and links connecting adjacent nodes, an inactive link carrying no light signals such that when the inactive link is made active another one of the links is made inactive, and the network carrying the light signals in a plurality of wavelength bands separate from each other, the node comprising: a drop coupler and an add coupler for each of the opposite directions for taking out a share of the light signals at the node and adding light signals in the node to the light signals carried in the network, respectively; plural receivers for receiving light signals in wavelength bands in the node and transmitters for transmitting light signals in wavelength bands from the node into the network; a band blocking filter arranged between the drop coupler and the add coupler for each of the opposite directions for blocking in the respective opposite direction light of all wavelengths in the wavelength bands of light signals which are received by the receivers in the node from the respective direction; and at least one of: a 2x1 switch coupled between the drop couplers and at least one of the receivers for allowing the at least one of the receivers to receive from either one of the opposite directions, and a 1x2 switch coupled between at least one of the transmitters and the add couplers for allowing the at least one of the transmitters to transmit in either one of the opposite directions. 2. The node of claim 1, wherein the receivers are divided in two groups, a first group of west port receivers and a second group of east port receivers, a 2x1 switch being coupled to all the receivers of one of the groups for allowing all the receivers of said one of the groups to simultaneously receive from either one of the opposite directions. 3. The node of claim 2, further comprising an optical demultiplexer coupled between the 2x1 switch and said one of the groups of receivers. 4. The node of claim 1, wherein the transmitters are divided in two groups, a first group of a plurality of west port transmitters and a second group of a plurality of east port transmitters, a 1x2 witch being coupled to all the transmitters of one of the groups for allowing all the transmitters of said one of the groups to simultaneously transmit in either one of the opposite directions. 5. Then node of claim 4, further comprising an optical multiplexer coupled between the 1x2 switch and said one group of the transmitters.