An optical communication system includes a looped path in which an active trunk fiber and a standby trunk fiber are connected in a loop. A plurality of optical combining/splitting units is provided on an active trunk fiber in series, and a plurality of slave devices is connected the plurality of optical combining/splitting units, respectively. A master device performs optical communication with each slave device. Each optical combining/splitting unit includes an optical sensor configured to detect an optical signal passing through an optical fiber and a transmitter. The transmitter determines whether or not there is an abnormality in optical communication on the basis of a detection state of the optical signal and transmits an abnormality notification including identification information of the optical combining/splitting unit to a monitoring apparatus in a case where there is an abnormality. The monitoring apparatus holds connection relationship information indicating a connection relationship between the plurality of optical combining/splitting units along the active trunk fiber. In a case where the monitoring apparatus receives the abnormality notification from at least one of the plurality of optical combining/splitting units, the monitoring apparatus specifies a failure position on a communication path on the basis of identification information of each optical combining/splitting unit that has transmitted the abnormality notification and the connection relationship information.

A monitoring control unit (22) of an OXC (20d) stores a management table (22a) in which pieces of information regarding a modulation mode, an FEC, and a frame mode of an optical signal are associated with each other, and sequentially changes the modulation mode, the FEC, and the frame mode according to the management table (22a) upon an LOS alert from a relay-side optical input/output unit (24) or an LOF alert from a DSP (25) being input thereto. Upon successfully receiving an appropriate optical signal according to the change, the monitoring control unit (22) acquires transmission source information included in the optical signal, and detects an occurrence of erroneous connection of an optical transmission line in an OXC (20g), which serves as a relay apparatus, when the acquired transmission source information indicates an optical cross-connect apparatus that is a transmission source different from an original transmission source.

A method and apparatus is proposed for accurately evaluating the performance of optical transmitters under test conditions (such as high bit-rate modulation formats) that compromise the operability of standard test equipment used for this purpose. The proposed apparatus and method are similar to the elements associated with existing testing standards based on an optical eye diagram, with an important distinction that allows for accurate measurements of the transmitter's performance to be made. In particular, the sampling point for collecting eye diagram data samples in the inventive arrangement is shifted by half a period with respect to the conventional mid-eye sampling point, eliminating the need to include representative reference equalizer in the test equipment and providing an evaluation not influenced by the test equipment, resulting in a more accurate measurement of transmitter-related distortions.

A service management method and apparatus for a passive optical network, an optical line terminal and a medium are disclosed. The method may include, maintaining communication with the OLT; acquiring optical network unit management control interface (OMCI) frame data transferred via the OLT; acquiring service information of the ONU according to the OMCI frame data; and performing the service management to the passive optical fiber network according to a network connection status between the OLT and the OMCI VNF, and service information of the ONU.

A method includes determining a first power level by performing a first series of measurements based on a first series of burst transmissions from an optical transmitter of an optical network unit (ONU) in an optical network. Bursts in the first series of burst transmissions include a first modified preamble. A second power level is determined by performing a second series of measurements based on a second series of optical burst transmissions. Bursts in the second series of burst transmissions include a second modified preamble. A first power level (P.sub.0) and a second power level (P.sub.1) are determined based on the first power level and the second power level and one or more additional parameters associated with transmissions from the optical transmitter are determined based on P.sub.0 and P.sub.1. Based on the additional parameters, it is determined whether the optical transmitter complies with specifications of the optical network.

Methods for, and network elements in, packet or optical transport networks are disclosed, including a network element comprising non-transitory computer readable medium storing computer-executable instructions configured as one or more software agents that when executed with computer hardware: determine a state of the network element, comprising comparing a current state of transient properties of the network element against a predetermined, expected state of the transient properties of the network element; and verify a state of other network elements or paths in the transport network by comparing a current state of one or more network-level constraints of the other network elements or paths against a predetermined, expected state of the one or more network-level constraints on the other network elements or paths. The computer hardware may further positively or negatively acknowledge received instructions to apply a configuration to the network element based on the determination and/or verification.

A data communication network includes a plurality of network nodes coupled together via optical links and a network controller. Each network node includes a reflectometry analyzer that provides a characterization of physical properties of the optical links coupled to the associated network node. The characterization for each particular optical link provides a unique fingerprint of the physical properties of the particular optical link. The network controller determines a network path between a first network node and a second network node, wherein the network path traverses a first optical link, receives a first fingerprint for the first optical link from a first reflectometry analyzer, defines a signature for the path, the signature including the first fingerprint, receives a second fingerprint for the first optical link from the first reflectometry analyzer, the second fingerprint being different from the first fingerprint, and determines that the network path is not secure based upon the difference between the first fingerprint and the second fingerprint.

A monitoring control unit (22) of an OXC (20d) stores a management table (22a) in which pieces of information regarding a modulation mode, an FEC, and a frame mode of an optical signal are associated with each other, and sequentially changes the modulation mode, the FEC, and the frame mode according to the management table (22a) upon an LOS alert from a relay-side optical input/output unit (24) or an LOF alert from a DSP (25) being input thereto. Upon successfully receiving an appropriate optical signal according to the change, the monitoring control unit (22) acquires transmission source information included in the optical signal, and detects an occurrence of erroneous connection of an optical transmission line in an OXC (20g), which serves as a relay apparatus, when the acquired transmission source information indicates an optical cross-connect apparatus that is a transmission source different from an original transmission source.

A buffer unit including a plurality of buffers, a sorting unit configured to sort an input signal to any of the plurality of buffers based on header information, a rate calculation unit configured to calculate a rate at which the input signal is read from each of the plurality of buffers based on burst information of the input signal, an adjustment unit configured to adjust a rate at which the input signal is read from each of the plurality of buffers based on the rate calculated by the rate calculation unit, and a transfer unit configured to transfer the signal read from each of the plurality of buffers are provided.

An apparatus includes a reconfigurable optical add/drop multiplexer (ROADM) having an input port to receive a first optical signal from a second device. The ROADM also includes a first wavelength selective switch (WSS), in optical communication with the input port, to convert the first optical signal into a second optical signal, a loopback, in optical communication with the first WSS, to transmit the second optical signal, and a second WSS, in optical communication with the loopback, to convert the second optical signal to a third optical signal and direct the third optical signal back to the second device via the input port.