Abstract: In an optical network a 1+1 bidirectional protection system is presented. Each node across a link has photodiodes to monitor the power of signals received by the node on receiving working and protection optical fibers and also optical switches connected to transmission working and protection optical fibers to modulate signals to its counterpart node across the link. When a node detects a fault in the receiving working optical fiber, not only does the node switch to the receiving protection optical fiber, but it also switches to the transmission protection optical fiber to signal the fault to the node across the link. The optical switches on transmission working and protection optical fibers allow the two nodes across the link to signal each other at a protocol-less or primary protocol level for the link to revert back to its initial state.

Abstract: In one embodiment, techniques provide a mechanism for tracking wavelengths in a DWDM network. In particular, embodiments of the present invention also provide for connection tracking using a slowly modulated pilot tone in a DWDM network without dedicated hardware for the generation and the diction of the tone.

Abstract: A WDM communication system that includes links traversing substantially inaccessible regions may tolerate multiple failures. In one implementation, a primary link spanning such a region is protected by a backup link. To provide further fault tolerance diverse paths may be provided to and from this backup link. The region may be, for example, an ocean.

Abstract: Agile OADM structures having a range of tradeoffs between costs and flexibility are disclosed. In certain implementations, cyclic AWGs (arrayed waveguide gratings) are employed. Excellent optical performance is achieved along with relatively low initial and upgrade costs. An economically optimal level of network flexibility may thus be achieved.

Abstract: Agile OADM structures having a range of tradeoffs between costs and flexibility are disclosed. In certain implementations, cyclic AWGs (arrayed waveguide gratings) are employed. Excellent optical performance is achieved along with relatively low initial and upgrade costs. An economically optimal level of network flexibility may thus be achieved.

Abstract: In an optical network a 1+1 bidirectional protection system is presented. Each node across a link has photodiodes to monitor the power of signals received by the node on receiving working and protection optical fibers and also optical switches connected to transmission working and protection optical fibers to modulate signals to its counterpart node across the link. When a node detects a fault in the receiving working optical fiber, not only does the node switch to the receiving protection optical fiber, but it also switches to the transmission protection optical fiber to signal the fault to the node across the link. The optical switches on transmission working and protection optical fibers allow the two nodes across the link to signal each other at a protocol-less or primary protocol level for the link to revert back to its initial state.

Abstract: Systems and methods for evaluating an optical communication link are provided. The evaluation is based on a polarization analysis of received optical power. Such an analysis is able to differentiate between received noise and received optical signal power, even for typical multi-channel signals. By appropriately analyzing the polarization of received optical power, the link quality can be evaluated. Failures may be detected and optical signal to noise ratio may be measured.

Abstract: A local area network is used to interconnect media equipment, such as telephones, VoIP telephones, a media server, etc., located at geographically distributed sites of an optical communication system. The local area network may be implemented within an optical services channel carried by a WDM optical communication link. This may provide the needed connectivity at low costs and may allow conference calls to be accommodated.

Abstract: In one embodiment, techniques provide a mechanism for tracking wavelengths in a DWDM network. In particular, embodiments of the present invention also provide for connection tracking using a fast pilot tone in a DWDM network without dedicated hardware for the generation and the diction of the tone.

Abstract: Agile OADM structures having a range of tradeoffs between costs and flexibility are disclosed. In certain implementations, cyclic AWGs (arrayed waveguide gratings) are employed. Excellent optical performance is achieved along with relatively low initial and upgrade costs. An economically optimal level of network flexibility may thus be achieved.

Abstract: A efficient and inexpensive optical WDM network architecture with add and drop couplers. Add couplers and drop couplers connected to a network optical fiber with wavelength blocker units which filter out optical signals at selected wavelengths on the optical fiber. The wavelength blocker units are distributed among the add and drop couplers so that each segment of the optical fiber between pairs of neighboring wavelength blocker units has at least three add and drop couplers. More specifically, each segment has the following relationship: THRU+ADD+DROP+LOCAL?TOTAL where THRU is the number of channels passing through the segment; ADD is the number of channels added within the segment; DROP the number of channels dropped within the segment; LOCAL the number of channels confined within the segment; and TOTAL is the total capacity of the optical fiber.

Abstract: An autoprotected optical communication ring network includes a first and a second optical carrier having opposite transmission directions and a plurality of optically reconfigurable nodes optically connected along the first and the second optical carrier and adapted to communicate in pairs on links susceptible to failure, the ring network having a normal operative condition in which the nodes of each pair are optically configured so as to exchange optical signals on a working arc path at a respective first wavelength (?x) on the first carrier and at a respective second wavelength (?y) different from the first wavelength (?x) on the second carrier, the working path having a complementary arc path defining a protection arc path in which the first wavelength (?x) on the first carrier and the second wavelength (?y) on the second carrier can be used for further links.

Abstract: An autoprotected optical communication ring network is disclosed. The ring network includes two optical carriers that are arranged for bidirectional transmission. Multiple optically reconfigurable nodes are connected along the optical carriers. The nodes communicate in pairs, defining non-overlapping working links. Under normal conditions, the nodes of each pair are optically configured to exchange optical signals over the working link at a first wavelength on the first carrier and at a second wavelength that is different from the first wavelength on the second carrier. During a failure condition, the first wavelength on the second carrier and the second wavelength on the first carrier are reserved for effecting a protection scheme, while the first wavelength on the first carrier and the second wavelength on the second carrier can still be used for unaffected working links.

Abstract: Systems and methods for reliable and low cost optical connection verification. One application is verification and monitoring of optical cross-connect performance. A connection is verified by splitting off optical signals at both ports of the connection, converting the signals to electrical signals, and then cross-correlating to verify connectivity between the ports. Lowpass filtering applied to the electrical signals may be applied to reduce the complexity of the cross-correlation.

Abstract: An autoprotected optical communication ring network includes a first and a second optical carrier (2, 3) having opposite transmission directions and a plurality of optically reconfigurable nodes (20a-20f) optically connected along the first and the second optical carrier (2, 3) and adapted to communicate in pairs by means of respective links susceptible of failure, the ring network having a normal operative condition in which the nodes of each pair are optically configured so as to exchange optical signals on a respective working arc path at a respective first wavelength (&lgr;x) on the first carrier (2) and at a respective second wavelength (&lgr;y) different from the first wavelength (&lgr;x) on the second carrier (3), the respective working path having a complementary arc path defining a respective protection arc path in which the first wavelength (&lgr;x) on the first carrier (2) and the second wavelength (&lgr;y) on the second carrier (3) can be used for further links and the first wavelength (&lgr;x) on