For protecting traffic from a source client entity (CE1) to a destination client entity (CE2) via an optical transport network and attachment circuits at ingress (A,B) and egress (C,D) nodes, there are multiple paths within the OTN, and the attachment circuits are dual homed. By sending (120) an indication of operational status of the dual homed attachment circuits within overhead associated with the traffic and sent with the traffic through the network, a selection can be made (130) of which of the provided paths and attachment circuits to use for the traffic, based on the indicated operational status, and on OTN fault detection, to protect against a fault. Thus protection can extend across the edge nodes without interworking of separate protection schemes and without a control plane. Traffic flows can be multiplexed at the ingress, with the indication in the overhead having separate indications for each of the traffic flows.

An apparatus for protection switching in an optical transport network (OTN) includes: a working path interface module configured to check, via a working path for protection switching, connectivity of a first end node and a corresponding second end node; and a protecting path interface module configured to check connectivity of the first end node and the second node via a protection path for protection switching. Upon confirming the connectivity, the working path interface module and the protection path interface module exchange bandwidth resize (BWR) coordination information with each other and simultaneously output an ODUflex bandwidth control signal based on the exchanged BWR coordination information.

A network design apparatus includes: a memory; and a processor coupled to the memory and configured to execute: accommodation design processing of, based on a traffic of a protection-applied or protection-unapplied first link in a first layer, generating a protection-unapplied second link in a second layer lower than the first layer, and generating a working path and a protection path of the first link on a network configured of the second link, and protection application processing of, based on the protection-unapplied second link and the working path and the protection path of the first link that are generated in the accommodation design processing, selecting or generating a protection-applied link in the second layer from the protection-unapplied second link.

A communications network remote node having a downstream optical circuit configured to receive downstream, DS, optical signals from an active main node and from a standby main node, the downstream optical circuit switchable between a working mode and a protection mode. Optical receivers are configured to receive the demultiplexed downstream optical signals and output encapsulated downstream client signals. Optical transmitters are configured to receive encapsulated upstream client signals and to transmit upstream, US, optical signals at upstream wavelengths carrying the encapsulated upstream client signals. An upstream optical circuit is configured to multiplex the upstream optical signals carrying the encapsulated upstream client signals and to send the upstream optical signals to both main nodes. Processing circuitry is configured to extract downstream client signals and alignment data from encapsulated downstream client signals and form encapsulated upstream client signals by encapsulating upstream client signals and alignment data.

Integrated performance monitoring (PM); optical layer operations, administration, maintenance, and provisioning (OAM & P); alarming; amplification, and the like is described in optical transceivers, such as multi-source agreement (MSA)-defined modules. A pluggable optical transceiver defined by an MSA agreement can include advanced integrated functions for carrier-grade operation which preserves the existing MSA specifications allowing the pluggable optical transceiver to operate with any compliant MSA host device with advanced features and functionality, such as Forward Error Correction (FEC), framing, and OAM&P directly on the pluggable optical transceiver. The advanced integrated can be implemented by the pluggable optical transceiver separate and independent from the host device.

A data communications system has a plurality of nodes connected by a plurality of links. A subset of the links and nodes forms a worker path for carrying worker data through the communications system, and a further subset of links and nodes provides a protection path for carrying other data in the absence of a fault in the worker path and for providing an alternative path for the worker data in the event of a fault in the worker path. The alternative path is predetermined prior to the detection of a fault in the worker path.

An optical transmission device for transmitting and receiving a multilevel-modulated optical signal includes a plurality of transmission frame processors for generating transmission frame signals accommodating a plurality of client signals that are each subjected to error correction processing and scrambling/descrambling processing, and a digital modulator/demodulator for mapping the transmission frame signals that are input to and output from the plurality of transmission frame processors to a multilevel signal. The digital modulator/demodulator performs digital modulation/demodulation, in which the plurality of transmission frame processors each have a function of shifting a phase of a pattern between a plurality of transmission frames to be mapped to a multilevel signal and to be digitally modulated/demodulated.

An Optical Transport Network (OTN) fault localization method, an iterative OTN fault localization method, and an OTN network use OTN tandem connection monitors operating in a Monitor mode to provide fault localization. The methods and network use TCMs for fault localization that can be performed manually or automatically to isolate a fault in a multi-domain OTN network to a particular link, switching fabric, or transport function. Additionally, a roles-based assignment scheme is presented for automatically assigning TCM levels between domains and links in multi-domain OTN networks. The fault localization methods enable fault localization in an automated and non-intrusive manner.

A method of processing a digital signal for transmission is provided comprising digital data frames, by compressing the digital data frames; and generating an optical data unit for transmission comprising multiple of the compressed digital data frames. The optical data unit is configured for transport by an Optical Transport Network, OTN.

A node for a communications network has a converter for digitizing at a receiver clock rate a received optical signal received over an optical link from an optical transmitter at a source node, a framer for detecting frames and a forward error correction part for correcting errors in the payload of the frame. An error rate in the received payload part is monitored and a processor sends, according to the monitored error rate, a request to the optical transmitter to adapt a length of the transmitted forward error correction part and to adapt a clock rate of the transmission of the frame if FEC length is reduced or FEC is disabled. This can enable power saving, when less FEC information is being sent.