Abstract: According to an aspect of an embodiment, a method of modulating supervisory data onto an optical signal includes receiving supervisory data and adjusting a characteristic of a carrier of the optical signal for at least one of a first polarization component of the optical signal and a second polarization component of the optical signal based on the received supervisory data. The characteristic may be adjusted such that there is a relative difference between the characteristic for the first polarization component and the second polarization component. The relative difference of the characteristic between the first polarization component and the second polarization component may indicate the supervisory data. Alternately, the characteristic may be adjusted such that there is a change in a polarization orientation of the carrier on a Poincaré sphere that indicates the supervisory data.

Abstract: According to an aspect of an embodiment, a method of modulating supervisory data onto an optical signal includes increasing a first power level of a first polarization component of an optical signal based on supervisory data. The method further includes decreasing a second power level of a second polarization component of the optical signal based on the supervisory data. The decrease in the second power level is substantially the same as the increase in the first power level such that a total power of the optical signal is substantially constant.

Abstract: A system and method for managing the selection of ghost channels in an optical communication system, including components configured to collect one or more first data values indicating the validity of an optical communication channel within a first degree of a node in the optical communication system, collect one or more second data values indicating the optical power level of the optical communication channel, transmit the first and second data values to a second degree of the node, receive the first and second data values at the first degree, and aggregate the first and second data values for the first degree and the second degree at the first degree.

Abstract: An apparatus including a polarization controller is described. The polarizer controller is communicatively coupled via a feedback loop to an evaluation module located near an optical receiver. The evaluation module is configured to measure polarization dependent loss (PDL) of an optical signal received at the optical receiver. The polarization controller is configured to receive feedback control data regarding the PDL from the evaluation module. Additionally, the polarization controller is configured to modify a state of polarization of the optical signal at an optical transmitter, which is communicatively coupled to the optical receiver, based on the feedback control data.

Abstract: The invention relates to a method for monitoring a passive optical network having a tree-like structure with a main line and a plurality of branches. The method includes transmitting a wake-up signal from an optical line termination (OLT) arranged in the main line to a plurality of monitoring units arranged in the branches. The method also includes detecting the wake-up signal and listening to information requests from the OLT in the monitoring units during a listening time interval after the detection of the wake-up signal. The method further includes transmitting an information request to be received in the listening time interval from the OLT to the monitoring units. The method additionally includes receiving the information request in the monitoring units during the listening time interval, one of the monitoring units which is addressed by the information request transmitting a response message back to the OLT.

Abstract: A WDM optical transmission system includes a plurality of optical nodes optically coupled by a transmission line, a processor that is operative to calculate an amount of adjustment of a reception level capable of increasing an optical signal-to-noise ratio for each channel of the WDM light reaching the optical node positioned at a receiving end of the unit section based on information on amplification operation of the WDM light in at least one optical-amplification repeating node disposed on the optical transmission line in the unit section, and to adjust a power level corresponding to each channel of the WDM light transmitted on the transmission line from the optical node positioned at a transmission end of the unit section in accordance with a calculation result of the calculation.

Abstract: An optical transmission apparatus is provided with an optical filter on a transmission line between a reception end of a transmission line and an OSC receiver. The optical filter has transmission characteristics such as to pass main signal light and optical supervisory channel light (OSC light), and to cut off noise light contained in at least one end portion band on a short wavelength side and a long wavelength side of an OSC transmission band used for reception of OSC light. By such a configuration, even in a case where the OSC light is Raman amplified and transmitted, the influence of noise light due to Raman amplification can be reduced, and OSC light can be received reliably, enabling high dependability to be realized.

Abstract: A span loss monitoring system includes a supervisory signal sending apparatus with a output level monitoring section, a time stamp generation section, and a supervisory signal generation section that generates a supervisory signal including a pair of the output level measurement hour and the output level. The span loss monitoring system also includes a supervisory signal receiving apparatus with an input level monitoring section, a supervisory signal termination section and a span loss calculation section.

Abstract: A wavelength division multiplexing (WDM) transmission system for transmitting a wavelength division multiplexed signal light from a sender transmission apparatus to a receiver transmission apparatus is provided. The system comprises a computing unit that subtracts from a first optical signal noise ratio (OSNR) of the signal light measured by the receiver transmission apparatus a second OSNR ascribed to a sideband of the signal light measured by the sender transmission apparatus so as to compute a corrected OSNR of an amplified spontaneous emission (ASE) noise light with a reduction of an effect of the sideband.

Abstract: A power-saving mode flag generating unit 101e sets a power-saving mode flag to active (non power-saving mode, turning on the power-source) when it receives a reset signal from a MAC unit 102. Furthermore, the power-saving mode flag generating unit 101e sets the power-saving mode flag to sleep (power-saving mode, turning off the power source) in accordance with a signal-interrupt detection signal obtained by the signal-interrupt detecting unit 101f1 of the packet monitoring unit 101f. Depending on the state of a packet, the power-saving mode flag generating unit 101e changes the power-saving mode flag to active or sleep for the data communication area of the packet; however, for the ranging area of the packet, the power-saving mode flag generating unit 101e always sets the power-saving mode flag to active. A pattern discriminating unit 101g discriminates between the data communication area and the ranging area of the packet.

Abstract: Delivering multicast data traffic over a communication network includes a first network node delivering multicast data traffic to second network nodes. The first and second network nodes are connected by a transmission network in a ring architecture and implement a point-to-multipoint layer 2 protocol. A method includes at the first network node: collecting alarms signals indicative of a failure along the whole ring and of the second network nodes. Based on a current state of the alarm signals, delivering the multicast data traffic either in a first delivery direction along the ring, or in a second delivery direction along the ring opposite to the first delivery direction, or in both the first and second delivery directions. At each of the second network nodes: collecting alarm signals indicative of a failure of the transmission network locally to the second network node and of the second network node.

Abstract: In an optical transmission apparatus, a unit includes a first connection section, a second connection section, a branching section, a first detection section, and a second detection section. The first connection section connects to a first component. The second connection section connects to a second component. The branching section is disposed at a preceding stage of the second connection section and outputs signal light to the first component through the first connection section. The first detection section determines whether the first component receives the signal light output from the branching section. The second detection section is disposed at a subsequent stage of the second connection section and detects the signal light.

Abstract: A method for monitoring wavelength-division multiplexed (WDM) signal for detecting signal drift of objective signals, including generation of one or more objective signals and a guard signal. The guard signal has a wavelength that is within a range defined by a guard channel. The first and second objective signals and the guard signal are wavelength-division multiplexed to generate a wavelength-division multiplexed signal. The first objective signal, the second objective signal, and the guard signal are assigned to a first multiplexed objective channel, a second multiplexed objective channel, and a multiplexed guard channel, respectively. The wavelength-division multiplexed signal is received by a monitor and then the error rate of the multiplexed guard channel is determined.

Abstract: A system for mitigating the effects of polarization hole burning in an optical communication system. The system includes an optical input signal comprising one or more traffic channels, a measurement module configured to check for the existence of ghost channels around the traffic channels, and a ghost channel generation module configured to generate a ghost channel around the traffic channels from amplified spontaneous emission noise of the optical input signal.

Abstract: The present invention relates to an optical cross-connect apparatus supporting plural directions, and provides a method of effectively performing an alarm indication by a node supervisory unit of the optical cross-connect apparatus. The node supervisory unit includes an alarm indication information storage unit that manages a management table for each of the plural directions. The management table manages not only received alarm indication information but also “internal WSS input/output port optical fiber connection state”, “WSS optical path setting state on DROP/THROUGH selection side”, “transponder destination location”, and “destination direction”, with respect to each direction. Then, a process flow is added to match received FDI information with the management information stored in the management table for each direction, and to specify an alarm destination.

Abstract: Exemplary embodiments of the invention relate to an optical transceiver module having a diagnostic communications link, wherein the link is configured to access diagnostic and other data contained within the transceiver controller via a backdoor interface. Controller data, including operational parameter values and module setup values, is accessible while the transceiver operates in conjunction with an external host and may be retrieved, and sometimes modified, in real time without interrupting normal transceiver operation or suspending the transmission of data over optical fibers. The data is accessed with an external user device via a backdoor interface on the outside of the transceiver module.

Abstract: In case of a disconnection failure of an optical transmission line, a Raman amplifier generates a loss of main and supervisory signal alarms, an optical amplifier generates a loss of main signal alarm, and a supervisory signal transmission and reception unit detects the loss of supervisory signal. On the other hand, in case of a failure generated in an optical fiber, the supervisory signal transmission and reception unit performs APR control. Thus the optical amplifier stops outputting the main signal and continues to output the supervisory signal. The Raman amplifier generates the loss of main signal alarm, and the supervisory signal transmission and reception unit detects the loss of supervisory signal. The monitoring unit identifies failure point according to a combination of an existence of the loss of signal alarm by the Raman and optical amplifiers and the loss of supervisor signal by the supervisory signal transmission and reception unit.

Abstract: A system and method for monitoring an optical communication system. The system may include trunk terminals coupled through a trunk path and a branch terminal coupled the trunk path. A monitoring signal routing device within the branch terminal routes a monitoring signal from a branch-drop path to a branch-add path.

Abstract: One embodiment provides a system for performance monitoring in a passive optic network (PON). The system includes an optical line terminal (OLT) and an optical network unit (ONU). The OLT includes an optical transceiver configured to transmit optical signals to and receive optical signals from the ONU, and a performance monitoring mechanism configured to monitor performance of the PON based on received optical signals.

Abstract: A dynamic gain equalizer-monitor (DGEM) includes a light modulator operable to modulate one or more component wavelengths of an input optical signal. The DGEM also includes a grating operable to receive one or more modulated component wavelengths from the light modulator. The grating is also operable to combine a first portion of each of the one or more modulated component wavelengths and transmit that first portion into an output optical signal. The DGEM may also include a detector array operable to receive, from the grating, a second portion of modulated component wavelengths that are separated from the first portion by the grating. The detector array is operable to generate an electrical signal proportional to an optical characteristic associated with each of the modulated component wavelengths of the second portion.

Abstract: A system for transmitting a plurality of data channels and an optical service channel through an optical fiber link of a Wavelength Division Multiplexed (WDM) optical communications system. The system comprises a first transmitter at a first end of the optical fiber link, for transmitting the data channels as a wavelength division multiplexed optical signal through the optical fiber link in a first direction. A second transmitter is connected at a second end of the optical fiber link, for transmitting the optical service channel through the optical fiber link in a second direction opposite to the first direction.

Abstract: A system and method is disclosed that allows for the monitoring, analyzing and reporting on performance, availability and quality of optical network paths. The correlation of PM parameter metrics to client connections, coupled with threshold-based alarm generation provides a proactive and predictive management, reporting and analyzing of the health and effectiveness of individual path connections to alert Operational Support (OS) staff and/or customers to signal degradation and impending Network Element (NE) failures. The system and method performs in real-time processing intervals required for alarm surveillance in a telecommunications network.

Abstract: A transponder having a dynamic remapping circuit remaps a value of decision threshold voltage Vdtc and a value of optical power RXP to a reference voltage Vref to minimize the bit error rate BER of a communication system. The dynamic remapping circuit implements a bilinear mapping of Vdtc and RXP to Vref with three bilinear remapping constants “a”, “b”, and “c” selected to align a remapped value of Vdtc_opt to a selected Vdtc normalization value, Vdtc_norm. A transponder in accord with an embodiment of the invention prevents BER from exceeding a threshold value of BER whether RXP or OSNR, or both, remain constant, change continuously, or change intermittently. Constants “a”, “b”, and “c” are related to parameters resulting from mathematically fitting a line to data comprising Vdtc_opt versus RXP. Another embodiment comprises a method for dynamically optimizing Vdtc and RXP to Vref in a transponder with a bilinear remapping circuit.

Abstract: An optical repeater connected to an optical transmission line between an optical network unit having an optical network unit (ONU) function on the side of a subscriber and an optical line termination (OLT) on the side of a center includes first electrical/optical conversion means connected to a first optical transmission line on the side of the center, a second electrical/optical conversion means connected to a second optical transmission line on the side of the subscriber, and transmission means connected between the first electrical/optical conversion means and the second electrical/optical conversion means to transmit an optical repeater supervisory signal between the optical transmission lines.

Abstract: The present relates to pluggable electronic unit with transmission power adjustment capability such as for example small form-factor pluggable transceivers. The pluggable electronic unit with transmission power adjustment capability may comprise a power adjustment unit. By verifying the transmitted power is sufficient or could be reduced, it is possible to regulate transmission power of a transceiver autonomously within the pluggable electronic unit itself.

Abstract: Described herein are systems and methods for a field-configurable optical network terminal (ONT) device at a subscriber to provide one or more communication services to the subscriber. The field-configurable ONT device is of a modular design operable for the insertion of additional communication modules or removal of existing communication modules from the ONT device for scaling the device to increased or decreased communication capacity as desired.

Abstract: Communication from a component in an optical communication system may be effected by modulating a system power voltage across the component to generate voltage signals representing the information to be communicated. The voltage signals generated by the component are detectable in the power feed equipment (PFE) in the optical communication system. Signature analysis may be performed on the system voltage data to identify the voltage signals and determine the information being communicated.

Abstract: Embodiments are directed to fiber optic cable diagnostics using digital modulation. A contact of a RFID (radio frequency identification) device located in a cable is connected with a contact of an optical transceiver. Data through the cable is using digital modulation and monitored to determine if the fiber optic cable and the optical transceiver are properly functioning.

Abstract: The invention refers a method and an arrangement for in service Raman gain measurements and monitoring of a wavelength division multiplex system. By measuring the power level values of a transmitted WDM signal (WMS_TX) and an optical supervisory signal (OSS_TX) at the transmitter and the power level values of the received signals (WMS_RX; OSS_RX) the Raman gain can be calculated for the different channels.

Abstract: An example method determines at an optical network monitoring device whether a value for at least one parameter that characterizes an optical signal which traverses a link of an optical coherent network is above a corresponding threshold and sets an alarm indicator when the value is larger than the corresponding threshold. The at least one corresponding parameter is at least one of polarization mode dispersion, polarization dependent loss and chromatic dispersion. An example method may obtains the optical signal from the link of the coherent optical network and determines the value for the at least one parameter, which may entail calculating the value based on the optical signal and filter coefficients of a filter that can be utilized to compensate the optical signal.

Abstract: A method and apparatus of detecting a rogue optical network unit (ONU) is provided. An optical line terminal (OLT) detects an abnormal upstream transmission to determine a plurality of rogue ONU candidates, and transmits a sleep allow message instructing a transition to a sleep mode to each of the plurality of rogue ONU candidates. The OLT detects the rogue ONU among the plurality of rogue ONU candidates based on upstream transmissions from the plurality of rogue ONU candidates in the sleep mode. Since the detection of the rogue ONU is performed in the sleep mode, the remaining ONUs can transition from the sleep mode to the normal mode after the detection of the rogue ONU is completed, thereby making it possible to rapidly resume upstream communication.

Abstract: A testing input module for testing an in-service WDM system is provided. The testing input module includes a first light source configured to emit a first light signal to one or more empty channels of the in-service WDM system; and a tunable second light source configured to emit a second light signal to test the one or more empty channels. The testing input module also includes a first switch module configured to: receive from the first light source and output the first light signal during a first time interval; and receive from the second light source and output the second light signal during a second time interval. The second time interval is a duration wherein a channel power monitoring function of the in-service WDM system is not triggered.

Abstract: A method for allocating and configuring TCM in an embodiment of the present invention includes: configuring the domain that needs TCM in a network and the scope of the domain; determining the ODU service that needs TCM; and allocating TCM automatically according to the ODU service trail and the configured domain; and enabling or disabling the TCM of each level. The present invention enables the system to allocate TCM automatically. The TCM levels can be allocated easily in a centralized way, or for each node in a distributed way. The present invention ensures that the TCM level allocated for the service in the forward direction corresponds to that in the reverse direction. The method is perfectly applicable to the networks of more than six operators. The TCM levels are handled according to the allocated order, thus ensuring correct insertion of AIS and BDI and unique result of insertion.

Abstract: The network operating system includes an embedded platform for controlling operation of an agile optical network at the physical layer level. At the module embedded level, each module (card-pack) is provided with an embedded controller EC that monitors and control operation of the optical modules. At the next level, each shelf is provided with a shelf processor SP that monitors and control operation of the ECs over a backplane network. All optical modules are connected over an optical trace channel to send/receive trace messages that can then be used to determine network connectivity. At the next, link management level, a network services controller NSC controls the SPs in a negotiated span of control, over a link network. The control is address-based; each NSC receives ranges of addresses for the entities in its control, and distributes these addresses to the SPs, which in turn distribute addresses to the ECs in their control.

Abstract: A channel alignment system in an optical communication network includes logic to sample power of a quadrature amplitude modulation (QAM) channel at a component downstream from a QAM modulator. The system determines if the sampled channel power has a sufficient level. The system signals power control logic of the QAM modulator to adjust a gain of the sampled channel.

Abstract: The embodiments of the invention provide a method of routing convergence in a control plane of an intelligent optical network, which includes: a function unit perceiving a service link state transmitting an alarm notification message indicating a failure in a service link to a routing protocol unit when the service link is in failure; the routing protocol unit confirming a service link failure in the control plane according to the alarm notification message. The embodiments of the invention also provide an apparatus of routing convergence in a control plane of an intelligent optical network. According to the embodiments of the invention, the establishment of a new service or re-routing may be implemented within several seconds or even hundreds of milliseconds after the service link failure in the control plane occurs.

Abstract: An ultra-long fiber-optic transmission system is configured in accordance with the current telecom standards and particularly advantageous for transmission data at a long distance which may exceed 400 km between adjacent nodes. The disclosed system has at least one intermediate amplifying node provided with a supervisory optical channel (SOC) which carries information between spaced nodes about the multi-wavelength optical signal as well as remote conditions at the optical terminal or regeneration site. The SOC comprises a transponder operative to select the direction in which an optical supervisory signal OSS, carrying information about the fiber break and malfunction of WDM channels, is transmitted along the SOC. The transponder further includes a receiver operative to measure the power of incoming OSS signal, which is indicative of the power of the transmitted and amplified WDM signal, and a Raman controller.

Abstract: A system and method for fault identification in optical communication networks. One or more repeaters in the system includes a loop back path that couples an output a first amplifier for amplifying signals carried in a first direction through a repeater to an input of a second amplifier for amplifying signals carried in a second direction through said repeater. Fault analysis is conducted using loop gain data associated with test signals transmitted on the first or second paths and returned on the opposite path through the loop back paths.

Abstract: This invention relates to a device and associated process capable of obtaining the optical spectrum phase of an optical signal or test signal to be analyzed using techniques for heterodyning between two monochromatic spectral components simultaneously extracted from the test signal itself by means of stimulated Brillouin scattering.

Abstract: An optical repeater connected to an optical transmission line between an optical network unit having an ONU function on the side of a subscriber and an optical line termination (OLT) on the side of a center includes first electrical/optical conversion means connected to a first optical transmission line on the side of the center, a second electrical/optical conversion means connected to a second optical transmission line on the side of the subscriber, and transmission means connected between the first electrical/optical conversion means and the second electrical/optical conversion means to transmit an optical repeater supervisory signal between the optical transmission lines.

Abstract: The present disclosure provides methods and systems for detecting small span loss changes in fiber optic networks. The present invention utilizes existing equipment without additional hardware to provide span loss measurements in a highly accurate manner. In an exemplary embodiment, the present invention utilizes power measurements associated with an optical supervisory channel (OSC) at both ends of a fiber span. These measurements are periodically sampled taking into account propagation delay along the fiber span. Further, these measurements are integrated or time-averaged to account for temporary fluctuations. The present invention can be utilized for intrusion detection (i.e., unwanted fiber taps), fiber degradation, and fiber aging performance. The present invention satisfies the criteria for a feasible (i.e., makes use of current architecture), cost-effective (i.e., does not require additional hardware), and highly accurate solution (i.e., capable of detecting span loss changes of 0.01 dB or 0.03%).

Abstract: A method for monitoring wavelength-division multiplexed (WDM) signal for detecting signal drift of objective signals, including generation of one or more objective signals and a guard signal. The guard signal has a wavelength that is within a range defined by a guard channel. The first and second objective signals and the guard signal are wavelength-division multiplexed to generate a wavelength-division multiplexed signal. The first objective signal, the second objective signal, and the guard signal are assigned to a first multiplexed objective channel, a second multiplexed objective channel, and a multiplexed guard channel, respectively. The wavelength-division multiplexed signal is received by a monitor and then the error rate of the multiplexed guard channel is determined.

Abstract: A method of detecting transmission collisions in an optical data interconnect system. The method includes initiating a data transmission of a data signal from a transmitting node over the optical data channel, transmitting a first collision detect signal from the transmitting node throughout a duration of the data transmission where the first collision detect signal is transmitted over an optical detection channel corresponding to the transmitting node, monitoring at the transmitting node of the optical data interconnect system for a predetermined period of time, where the optical data interconnect system further includes optical collision detection channels corresponding to each of a plurality of receiving nodes and one or more remaining nodes, and identifying a transmission collision when a second collision signal is received through one of the optical collision detection channels at the transmitting node during the predetermined period of time.

Abstract: A transponder having a dynamic remapping circuit remaps a value of decision threshold voltage Vdtc and a value of optical power RXP to a reference voltage Vref to minimize the bit error rate BER of a communication system. The dynamic remapping circuit implements a bilinear mapping of Vdtc and RXP to Vref with three bilinear remapping constants “a”, “b”, and “c” selected to align a remapped value of Vdtc_opt to a selected Vdtc normalization value, Vdtc_norm. A transponder in accord with an embodiment of the invention prevents BER from exceeding a threshold value of BER whether RXP or OSNR, or both, remain constant, change continuously, or change intermittently. Constants “a”, “b”, and “c” are related to parameters resulting from mathematically fitting a line to data comprising Vdtc_opt versus RXP. Another embodiment comprises a method for dynamically optimizing Vdtc and RXP to Vref in a transponder with a bilinear remapping circuit.

Abstract: Devices, systems and techniques for optical communication are provided based on polarization division multiplexing (PDM) to use an optical monitor channel at a distinct optical monitor wavelength to monitor optical polarization fluctuation and polarization mode dispersion during the transmission from the transmitter to the receiver to facilitate the effective demultiplexing of the two orthogonal signal channels at the receiver through automatic feedback control on a dynamic polarization controller and a polarization beam splitter.

Abstract: A method for laser safety protection in an optical communication system includes: a downstream station detecting whether an identification signal loaded by an upstream station on a main optical channel in a direction from the upstream station to the downstream station, exist on the main optical channel; if the identification signal is not detected, the downstream station executing a scheduled safety protection procedure. Methods for loading an identification signal on a main optical channel in an optical communication system and an optical amplifier of laser safety protection, which implement loading the identification signal by controlling the change of pump light of optical amplifier or the wave motion of signal light of main optical channel, are also provided. The solution makes it possible to reliably detect a fiber failure when RAMAN amplifiers or remotely-pumped amplifiers exist, thereby implementing laser safety protection.

Abstract: A robust and redundant status link is established by a first multi-channel optoelectronic device with a second multi-channel optoelectronic device in a multi-channel communication link. Transmitter bias currents are effectively modulated with a status link modulation signal representative of status data and subsequently modulated with primary data modulation signals. The resulting signals are transformed into optical signals and transmitted over the link as main communication links combined with a status link. At the second device, the optical signals are received and converted to electrical signals. The receipt of the optical signals creates multiple receiver bias currents, which may be monitored to detect the status link modulation signal. The second device may adjust various operating parameters in response to the information conveyed by the status link.

Abstract: The present invention relates to controlling wavelength switching in a plurality of nodes that are provided to increase the distance of signal transmission in inverse MUX transmission in which a high-speed line is divided into a plurality of low-speed lines for transmission. A maximum skew occurring between adjacent nodes is measured, and switching of wavelength channels is performed in one or a plurality of nodes on the basis of the measured maximum skew to keep the skew of the entire inverse MUX transmission system at or below a prescribed value. The optical communication device is provided with an NNI functional block to which high-speed lines on the transmission channel side are connected, and a UNI functional block to which low-speed lines on the client side are connected.

Abstract: Various high loss loop back (HLLB) repeater architectures are disclosed that enable selectively monitoring (e.g., measuring, analyzing, etc) of Rayleigh signals from both inbound and outbound directions of an optical communication system. In one such embodiment, first and second optical test signal frequencies (or ranges) are used, in conjunction with selective filtering, for monitoring the outbound and inbound paths, respectively. The repeater architectures allow optical time domain reflectometry (OTDR) monitoring techniques to be employed, for example, in particularly long repeater spans, such as those in excess of 90 km in length.

Abstract: In an optical transmission system, a transmitting transceiving node generates a multiplexed optical-packet signal by performing optical wavelength multiplexing on a plurality of optical packets, and transmits the multiplexed optical-packet signal to a receiving transceiving node. The receiving transceiving node transmits the multiplexed optical-packet signal back to the transmitting transceiving node. The transmitting transceiving node detects a skew amount of the optical packet allocated to each wavelength band of the multiplexed optical-packet signal received from the receiving transceiving node, and adjusts a delay amount of the optical packet based on the detected skew amount.