An optical end terminal in which protection switching is implemented by using (i) the optical data receiver thereof for detecting a path failure and (ii) the optical data transmitter thereof for signaling the detected path failure to the protection-switching circuit. In an example embodiment, the optical data receiver is configured to detect a path failure based on the presence of certain data-recovery errors. The optical data transmitter is operatively connected to the optical data receiver and configured to generate an in-band dither tone of a predetermined frequency in response to such failure detection. The protection-switching circuit is configured to (i) detect dither tones in the optical signals passing therethrough and (ii) connect the optical data receiver to the protection path instead of the working path in response to detecting the dither tone of the predetermined frequency.

Disclosed herein are switch devices in terminal ends of a network and methods of using same. One embodiment relates to a terminal end of a network including a terminal end transceiver configured to communicate with one or more end user devices, and a switch device configured to automatically route communication at the terminal end transceiver between a primary communication path with a central office and an auxiliary communication path with the central office. Another embodiment relates to a method of switching between primary and auxiliary communication paths at a terminal end. Automatic switching is particularly applicable in a looped communication architecture with redundant communication paths for preventing interruption and increasing reliability for an improved user experience. Another embodiment relates to indexing with splices to reduce connections in a communication path and increase signal quality.

In a case where a failure occurs in a part of an optical fiber in an optical cable, when attempting to switch to a redundant configuration, the stable use of an optical transmission system is impaired, so that the wavelength band cannot be used effectively. Accordingly, the optical transmission system of the present invention includes a first optical device configured to change the transmission line of a wavelength band signal propagating through a first optical transmission line to a second optical transmission line that is the same path as the first optical transmission line, in the stage before a faulty part in the first optical transmission line, and a second optical device configured to change the transmission line of the wavelength band signal from the second optical transmission line to the first optical transmission line, in the stage after the faulty part.

The present invention discloses: when a first laser in N lasers is switched to a second idle laser in M lasers, a wavelength of a wavelength-selective optical element to which the first laser is coupled is adjusted from a first wavelength to a second wavelength, and the second wavelength is different from the N wavelengths. Similarly, when a first optical receiver in N optical receivers is switched to a second idle optical receiver in M optical receivers, a wavelength of a wavelength-selective optical element to which the first optical receiver is coupled is adjusted from a first wavelength to a second wavelength, and the second wavelength is different from the N wavelengths.

An optical network system includes an optical line terminal, an optical splitter that is connected to the optical line terminal via one first optical fiber, and a plurality of optical network units that are connected to the optical splitter via respective second optical fibers. The plurality of optical network units communicate with the optical line terminal using an optical signal of a working wavelength uniquely assigned to each of them. The optical line terminal communicates with an optical network unit that is connected to the optical splitter using an optical signal of a working wavelength and an optical signal of a spare wavelength that is common to a plurality of optical networks.

[Objective] To make it possible to effectively relay remaining signals even when any input failure occurs on a propagation path. [Solution] Provided is an optical branching/insertion device including: a trunk-side detection/branching unit for detecting a failure of a trunk-side optical signal inputted from the trunk side and outputting it as a first detection result, and for splitting the trunk-side optical signal and sending the split signals respectively to the trunk side and to the branch side; a branch-side detection unit for detecting a failure of a branch-side optical signal inserted from the branch side and outputting it as a second detection result, and for sending the branch-side optical signal as an insertion signal; an insertion signal adjustment unit for outputting the insertion signal with its pass-through degree having been adjusted on the basis of the first detection result, as a first adjusted signal; a trunk signal adjustment unit for outputting the trunk-side optical signal with its pass-through degree having been adjusted on the basis of the first detection result, as a second adjusted signal; and a combining/output unit for outputting, to the outside, an optical signal into which the first adjusted signal and the second adjusted signal are combined together, as a trunk-side output optical signal.

According to a method, when it is detected that service traffic needs to be switched from a first optical layer path to a second optical layer path, a first internet protocol (IP) link associated with the service traffic needs to be determined, and an IP link used to transmit the service traffic is adjusted from the first IP link to a second IP link; an optical layer path of the first IP link is switched from the first optical layer path to the second optical layer path after the adjustment of the IP link is completed; and the IP link used to transmit the service traffic is adjusted from the second IP link to the first IP link after the switching of the optical layer path is completed. In this way, continuity of the service traffic can be ensured.

A procedure for transferring wavelengths, and a system that operates in accordance with the procedure. The system comprises at least one network terminal, each including a switch and a controller. A plurality of wavelength sets are applied to the switch. The controller is arranged to operate the switch such that the switch (a) selects at least one wavelength from at least one of the plurality of wavelength sets, based on electrical monitoring at a port module external to the network terminal, and (b) outputs the at least one wavelength to an output of the at least one network terminal.

A method for determining a path in an optical network, implemented by one or more controllers associated with a control layer, includes receiving a path request specifying start and end points, an associated bandwidth, and a longevity parameter providing an anticipated length during which the path is required; determining a route in the optical network through a routing algorithm executed by the controller, wherein the routing algorithm utilizes the start and end points, the associated bandwidth, and the longevity parameter to determine the path; and provisioning the path through a plurality of switches along the route.

A framer in a transmission device allocates plural optical channel time slots to a plurality of logical prioritized paths. It allocates received client signals to the allocated time slots, and transmits the client signals by a plurality of optical subcarriers that use a plurality of optical wavelengths corresponding to the plurality of time slots. The framer includes: a time slot allocation unit that, in a case where an optical wavelength corresponding to a time slot allocated to a logical path having a high transmission priority is not used, allocates at least one of the plurality of time slots to the logical path having the high transmission priority while the time slot corresponding to the unused optical wavelength is avoided, to change the time slot allocated to the logical path having the high transmission priority.