Abstract: A medium-scale IP telecommunications network is configured in a low-cost optical network with good reliability and expandability. A physical configuration example has a center node 2-1 and eight local nodes 2-11 through 2-18 connected in one OADM ring 2-21/2-22. The logical configuration is a star configuration with the central node 2-1 at its origin with all traffic passing through the center node 2-1. The local nodes 2-11 through 2-18 are connected to the central node 2-1 by wavelength-unit optical channels or optical paths ?1 through ?8. Channels are added as required. Initially, for example, the center node 2-1 and the local node 2-5 are connected by ?5, but ?13 can added when the need arises. Since the logical star network is limited to approximately two add/drop optical channels at local nodes, costs are reduced by using inexpensive filters (e.g., dielectric interference film filters or fiber Bragg reflectors) that are capable of extracting only the specific wavelength of the optical channel.

Abstract: To ensure transmission in a flexible optical network system, a digital test signal generation/comparison circuit is incorporated in an electrical signal processing portion of a transponder. The optical network system provides transparent wavelength-division multiplex service regardless of the signal type in client optical signals. Prior to connecting a client optical line to the optical system, a selective insertion unit and a selective extraction unit enable quality assessment of the client optical line.

Abstract: A medium-scale IP telecommunications network is configured in a low-cost optical network with good reliability and expandability. A physical configuration example has a center node 2-1 and eight local nodes 2-11 through 2-18 connected in one OADM ring 2-21/2-22. The logical configuration is a star configuration with the central node 2-1 at its origin with all traffic passing through the center node 2-1. The local nodes 2-11 through 2-18 are connected to the central node 2-1 by wavelength-unit optical channels or optical paths &lgr;1 through &lgr;8. Channels are added as required. Initially, for example, the center node 2-1 and the local node 2-5 are connected by &lgr;5, but &lgr;13 can added when the need arises. Since the logical star network is limited to approximately two add/drop optical channels at local nodes, costs are reduced by using inexpensive filters (e.g.

Abstract: Methods, apparatus and techniques for hitlessly accessing an original data signal include provisioning a duplicate of the original signal at a provisioning location. The duplicate signal is sent to a switching location that has been transmitting the original signal, but which hitlessly switches to transmitting the duplicate signal instead. The original signal is accessed at an access location where the original signal is altered. The altered signal is sent to the switching location which again hitlessly switches from transmitting the duplicate signal to transmitting the altered signal. Implementation in an optical network allows wavelengths to be dropped at nodes in the network without network hits being incurred which would disrupt service or otherwise result in system downtime.

Abstract: To ensure transmission in a flexible optical network system, a digital test signal generation/comparison circuit is incorporated in an electrical signal processing portion of a transponder. The optical network system provides transparent wavelength-division multiplex service regardless of the signal type in client optical signals. Prior to connecting a client optical line to the optical system, a selective insertion unit and a selective extraction unit enable quality assessment of the client optical line.

Abstract: A medium-scale IP telecommunications network is configured in a low-cost optical network with good reliability and expandability. A physical configuration example has a center node 2-1 and eight local nodes 2-11 through 2-18 connected in one OADM ring 2-21/2-22. The logical configuration is a star configuration with the central node 2-1 at its origin with all traffic passing through the center node 2-1. The local nodes 2-11 through 2-18 are connected to the central node 2-1 by wavelength-unit optical channels or optical paths &lgr;1 through &lgr;8. Channels are added as required. Initially, for example, the center node 2-1 and the local node 2-5 are connected by &lgr;5, but &lgr;13 can added when the need arises. Since the logical star network is limited to approximately two add/drop optical channels at local nodes, costs are reduced by using inexpensive filters (e.g.