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: A system and method is disclosed that allows real-time processing of child OPOI and rider service alarms from a parent OPOI which determines if one or more STS alarms are associated with a rider service, a child OPOI, or a parent OPOI. The system and method performs in real-time processing intervals required for alarm surveillance in a telecommunications network.

Abstract: A method, apparatus, and program, for evaluating an optical network node. The method comprises providing at least one communication path of the node with a capability by which lasing can occur in the communication path, and detecting whether lasing has been established in the communication path to determine whether the optical node is operational. If no lasing is detected in the detecting, a fault exists in the communication path. The method further comprises determining an insertion loss in the communication path, and determining whether the insertion loss is comparable to a predetermined insertion loss, to confirm whether the node is configured correctly.

Abstract: A fiber-optic communications interface (110) and method of operation that operates with a paired fiber-optic communications interface (112) in a redundant communications termination point (101). The fiber-optic communications interface (110) has a paired card interface (122) that exchanges at least a first subset of status data between a local bearer processor (124) and a paired bearer processor (144) located within a different card cage (112). The local bearer processor (124) processes bearer data channels communicating with a remote site (102) through a remote site fiber-optic line (106). A local data interface (128) exchanges data contained in the bearer data channels between the local bearer processor (124) and a local user data network (114). The local data interface (128) also exchanges at least a second subset of the status data with the paired bearer processor (144) through the local user data network (114).

Abstract: A device may include a first network module to capture network data at a first location in a network and a second network module to capture network data at a second location in the network different from the first location in the network. The device may include a control module to receive control commands relating to the first network module and the second network module. The control module may forwarded the control commands to the first network module and the second network module. The control module may receive the captured network data from the first network module and the second network module.

Abstract: A method and system of measuring the spectroscopic impedance of a sensor and its immediate surroundings. The sensor is disposed on an engineered structure and is coated with a protective coating. The method includes providing a first optical signal having a first modulation frequency and amplitude. The method also includes transmitting the first optical signal and a second optical signal from a first location to a sensor location. The method also includes modulating the second optical signal with a second modulation frequency and amplitude, the second modulation frequency and amplitude converted from the first optical signal. The method also includes comparing the first modulation frequency to the second modulation frequency to determine one of a phase difference and a time lag and calculating the electrochemical impedance spectroscopy of the sensor and its immediate surroundings as a function of frequency.

Abstract: An optical communication system has two or more active interfaces, each controlling the transmission and reception of optical signals between a communication network and one or more subscriber terminals according to control information pertaining to the individual subscriber terminals. The control information used by all the active interfaces is stored in a memory. The optical communication system also has a standby interface that is functionally equivalent to the active interfaces, and an optical switching apparatus that switches data transmission paths among the network, the active and standby interfaces, and the subscriber terminals. If a fault is detected in an active interface, the standby interface extracts the control information of the faulty interface from the memory, and the optical switching apparatus switches the data transmission paths so that the standby interface replaces the faulty interface.

Abstract: An optical transmission apparatus includes a non-reciprocal device including first to second ports, an optical signal input from the first port being provided to the second port, an optical signal input from the second port being provided to the first port, a dispersion compensator that is coupled to the first port of the non-reciprocal device and that conducts given processing to an optical signal input from the first port of the non-reciprocal device to provide the optical signal subjected to the given processing to the second port of the non-reciprocal device, a first monitor, a second monitor, and a fault determination device that compares a value monitored by the first monitor with a value monitored by the second monitor to determine a connection failure at the first and/or second ports of the non-reciprocal device and/or a connection state of the dispersion compensator.

Abstract: A method and an apparatus to provide optical equipment protection have been disclosed. In one embodiment, the method includes splitting an incoming optical signal into a first and a second optical signals, sending the first and the second optical signals to a first and a second equipments in an optical network node, respectively, the second equipment being a protection module for the first equipment, monitoring a first and a second outgoing optical signals from the first and second equipments, and declaring a failure of the optical network node if only one of the first and the second outgoing optical signals has failed. Other embodiments have been claimed and described.

Abstract: Disclosed is a method and apparatus which provides for alerting of potential fiber optic cable intrusion. A stress detector located at a fiber optic cable termination point detects stress on the fiber optic cable and generates an alarm signal in response to the stress detection. The alarm signal is transmitted to remote alarm units along the fiber optic right of way via a conductive metallic portion of the fiber optic cable (e.g., the fiber optic cable sheath). In response to receipt of an alarm signal, the alarm units initiate a perceptible (e.g., audible and/or visible) alarm. The stress detector may also determine a location of the stress, and generate an alarm signal addressed to a particular one or more alarm units in the vicinity of the stress location.

Abstract: Methods, systems, and computer-readable media provide for notifying and determining a location of a fiber cut. According to embodiments, a method for determining a location of a fiber cut in a passive optical network (PON) including a plurality of optical network terminations (ONTs) is provided. According to the method, a plurality of base signatures are generated prior to the fiber cut. Each of the base signatures correspond to a known configuration of the plurality of ONTs. In response to the fiber cut, a current signature corresponding to a current configuration of the plurality of ONTs is generated. Whether the current signature matches one of the base signatures is determined. In response to finding a matching base signature, the location of the fiber cut is determined based on the known configuration of the plurality of ONTs corresponding to the matching base signature.

Abstract: A method and system are provided for remotely monitoring undersea cable systems. Upon receiving a fault alert message, an optical cross-connect is set up between the subject cable station and a testing platform. Testing is conducted and a determination is made whether the fault is in the undersea portion of the network, or in the terrestrial backhaul. By making that determination early, unnecessary technician travel is reduced.

Abstract: A system, method, and computer readable medium for passive optical network rogue optical network unit diagnostics, comprises, detecting an alarm of a network, correlating the detected alarm to a bandwidth map, and selectively disabling an optical network unit upstream to the detected alarm on the bandwidth map for a pre-determined interval.

Abstract: The present invention discloses a method for handling channel failures in an Automatically Switched Optical Network (ASON). When a channel alarm occurs, the head service node decides whether the channel alarm is incurred by a channel failure according to the alarm message or alarm information. If so, the head and end service nodes continue to locate whether the channel failure is inside or outside the network by combining local detection and message notification. If the channel failure is an internal failure, rerouting is activated to locate and remove the channel failure. When this method is used to locate a channel failure, the amount of information exchanged is small. The method may quickly identify the accurate position of a failure inside the network, improve the efficiency in removing failures, and minimize the damages to services, with little harm to equipment functioning and network performance.

Abstract: A multi-wavelength optical transmission system includes a plurality of primary optical transmitters, each being configured to provide directly modulated analog optical signals at non-uniformly spaced apart wavelengths. An optical multiplexer having a plurality of optical input ports receives the analog optical signals from each of the plurality of primary optical transmitters and provides a wavelength division multiplexed signal over an optical fiber coupled at an output thereof. A spare optical transmitter is coupled to an input port of the optical multiplexer and, in response to detecting failure of a failed one of the plurality of primary optical transmitters, is tuned to provide a directly modulated analog optical signal at a spare wavelength that is selected as to be non-uniformly spaced relative to at least some of the non-uniformly spaced apart wavelengths according to tuning data.

Abstract: A method for processing fault dependency of different levels of tandem connection monitoring is provided. The method comprises obtaining monitored coverage scopes of the different levels of tandem connection monitoring (TCM); locating a fault section according to an overlapping relationship between monitored coverage scopes of the at least two different levels of TCM at which the warnings are reported and performance degradation degrees of the at least two different levels of TCM, the fault section being located when warnings are reported in at least two different levels of TCM; and outputting location-related information that includes information of the fault section to a user.

Abstract: A computerized system and method for managing a passive optical network (PON) is disclosed. The system includes a detection and analysis module adapted for receiving uploaded measurement data from an optical line terminal (OLT) and at least one optical network terminal (ONT), and at least one of technical tools data, service failure data, and outside plant data. The detection and analysis module is adapted for determining a source of failure or potential failure in the PON by correlating the uploaded measurement data and the at least one of technical tools data and service failure data with information stored in a memory medium for the OLT and each ONT.

Abstract: A fault detecting method, system, and apparatus for a PON system and an electrical relay apparatus are provided. The method includes the following steps. An electrical relay apparatus receives and detects a signal sent by a previous apparatus. If a defect is detected in the received signal, it is determined that a fault occurs to a transmission path between the previous apparatus and the electrical relay apparatus, and a signal with no defect is formed and sent to a next apparatus. If no defect is detected, the received signal is processed according to original processes and sent to the next apparatus. The next apparatus receives and detects the signal sent by the electrical relay apparatus. If a defect is detected in the signal sent by the electrical relay apparatus, it is determined that a fault occurs to a transmission path between the next apparatus and the electrical relay apparatus.

Abstract: The present disclosure relates to a passive optical network (PON) and discloses a method and system for maintaining the PON where the optical line terminal (OLT) is provided with an optical power detection module for measuring the total power of optical signals received by the PON, and the optical network units (ONUs) are provided with an optical transmitter power supply module.

Abstract: A signal is conducted from a controller module onto a network via a first coupling. The signal is transmitted across the network and received at one or more receiver modules via one or more second couplings. At the one or more receiver modules, the received signal is analyzed and based upon the analysis, a determination is made as to whether a fault has occurred in the network and/or where the occurrence occurred.

Abstract: Disclosed is a method and apparatus which provides for alerting of potential fiber optic cable intrusion. A stress detector located at a fiber optic cable termination point detects stress on the fiber optic cable and generates an alarm signal in response to the stress detection. The alarm signal is transmitted to remote alarm units along the fiber optic right of way via a conductive metallic portion of the fiber optic cable (e.g., the fiber optic cable sheath). In response to receipt of an alarm signal, the alarm units initiate a perceptible (e.g., audible and/or visible) alarm. The stress detector may also determine a location of the stress, and generate an alarm signal addressed to a particular one or more alarm units in the vicinity of the stress location.

Abstract: One apparatus embodiment includes a first light source, a second light source, and a receiver having a photodetector. The first light source emits a first signal at a nonvisible wavelength for data transmission. The second light source emits a second signal at a visible wavelength for fault detection when combined with the first signal for transmission over a fiber optic path. The receiver converts the first signal from the nonvisible wavelength to an electrical signal.

Abstract: A method, system and apparatus for managing alarms in a Long Reach Passive Optical Network (LR-PON) system are disclosed. The method includes: obtaining a PON signal from an Optical Line Terminal (OLT) or an Optical Network Unit (ONU) on one side; checking whether the obtained PON signal fails; and notifying the ONU or the OLT on the other side if the PON signal fails. The method, system and apparatus under the present invention monitor the LR-PON transmission quality and process various alarm indications raised in the LR-PON signal monitoring.

Abstract: An optical network system enabling confirmation of connection and tracking of wavelength paths at a high speed and a low cost without introducing any special hardware by having a wavelength path monitoring unit in an NMS give temporary change of optical power through a change generating unit to an optical signal S from an optical transmitting/receiving node, by having a change detecting unit confirm that this change of optical power has propagated through an optical transmission line and appeared at each node on the way, and confirming connections and monitoring the wavelength path while confirming the presence of the change.

Abstract: A method, apparatus, and system for evaluation of a faulty point in a multi-stage optical amplifying and repeating transmission line which provides a totally new technique for searching for faults neither of the typical “command response type” or the “DCR method”. When a fault occurs in an optical submarine cable, the profile exhibited by the optical spectral characteristics of the optical noise signal (ASE) successively amplified through the chain of optical amplifying repeaters at the downstream side of the faulty point changes in accordance with the number of the repeaters. The technique finds the number of the repeaters until the faulty point based on the change in the profile so as to evaluate the location of the faulty point and has a step (S11) of monitoring the optical spectrum at the light receiving end and a step (S12) of determining the location of the faulty point from the monitored optical spectrum.

Abstract: A photonic integrated circuit having a plurality of circuit components, is disclosed, which may include an MMI for splitting signal power passing therethrough among first and second optical pathways coupled to first and second outputs, respectively, of the MMI, thereby directing first and second percentages of the signal power along the first and the second optical pathways, respectively; and a photodetector integrated into the photonic integrated circuit and coupled to said first optical pathway for measuring a signal power level on said first optical pathway.

Abstract: An optical transmission apparatus comprises a preamplifier controlling unit for controlling a preamplifier so that amplified spontaneous emission including all wavelength bands of a wavelength-multiplexed signal beam is outputted toward a wavelength demultiplexing unit, with the wavelength-multiplexed signal beam not inputted, power monitors for monitoring optical powers of the amplified spontaneous emission fed from the preamplifier and wavelength-demultiplexed by the wavelength demultiplexing unit, and a determining unit for determining the continuity state of an optical propagation path of each wavelength component on the basis of a result of monitoring by the power monitors. The optical transmission apparatus allows the continuity test on optical propagation paths of channels including a channel not used at the time of a start of the operation to be made easier than the known techniques.

Abstract: A communication network comprising at least one first terminal, at least one second terminal, a plurality of links, and at least first and second nodes. The first node is bidirectionally coupled to the first terminal through at least a first one of the links, and also is bidirectionally coupled to the second terminal through at least a second link and the second node. Preferably, the first node comprises a plurality of communication paths, each of which is coupled at a first end thereof to at least one corresponding first link. Second ends of the communication paths are all coupled to the second link, through a multiplexing device, and route signals between the first and second links. The first node also preferably comprises at least one alternate communication path having a first end coupled through the multiplexing device to the second link, at least one switch that is coupled to the alternate communication path, and a detector for detecting a failure in at least one of the communication paths.

Abstract: An object is to provide a redundant supervisory control system and a redundancy switching method thereof. In the redundant supervisory control system, remote I/O apparatuses are less likely to be inaccessible, even in a case where failures occur in plural locations. Thus, the reliability of the system is enhanced. The redundant supervisory control system including a plurality of first loop interface units in each of a pair of controllers, second loop interface units, and communication cables each connecting the plurality of first and second loop interface units with one another in a circular loop. The redundant supervisory control system is configured by connecting the controllers and the remote I/O units to one another in a plurality of loop networks. In a case where abnormality in the loop networks is detected by use of received data in the networks, the first and second loop interface units that can perform normal reception are automatically selected.

Abstract: A method of self-testing includes transmitting a plurality of self-test signals and receiving the plurality of self-test signals. In addition, the method includes storing the received self-test signal in a first database; and comparing the received self-test signal with data from a second database. An self-testing apparatus and a method of for assuring substantially continued calibrated function of a testing device.

Abstract: There is provided in a telecommunications network comprising an optical fiber cable, and an optical component connected to a first point of the optical fiber cable, with an optical time domain reflectometer (OTDR) connected to a second point of the optical fiber cable so that it can emit OTDR signals along the optical fiber cable towards the optical component, a method of preventing OTDR signals from being applied to the optical component, comprising introducing one or more optical signals into the optical fiber cable at the first point thereof using the optical fiber cable to carry the optical signals to the second point thereof, and configuring the OTDR to detect the or each optical signal from the optical fiber cable and to prevent emission of OTDR signals at any time during which detection of an optical signal occurs. The optical component may comprise, for example, an optical receiver which may introduce the optical signals into the optical fiber cable.

Abstract: A method and apparatus of isolating a location of a fault in an optical network may include using communications traffic signals and network nodes to determine excess power losses without interrupting service or requiring additional external test equipment. A transmit optical network node is configured to measure the transmit power of multiple wavelengths of a transmitted optical signal. A receive optical network node is configured to measure the receive power of the same multiple wavelengths. Power differentials of the transmit and receive optical power for each wavelength may be calculated. Optical power losses as a function of the optical path distance between the transmit and receive optical network nodes my be determined. The data may be used to isolate the location of a fault in a passive optical network based on the differences between the optical power losses of the multiple wavelengths thereby reducing troubleshooting time and network downtime.

Abstract: An optical transmission apparatus includes optical transmitters for transmitting optical signals and first monitor units for monitoring optical signals from the optical transmitters. A multiplexer is provided for multiplexing the optical signals from the optical transmitters into a multiplexed signal. A second monitor unit is provided for monitoring each optical signal which is multiplexed in the multiplexed signal from the multiplexer. A processing unit is provided for comparing a first number of optical signals detected by the first monitor units and a second number of optical signals detected by the second monitor unit.

Abstract: A fiber-optic communications interface (110) and method of operation that operates with a paired fiber-optic communications interface (112) in a redundant communications termination point (101). The fiber-optic communications interface (110) has a paired card interface (122) that exchanges at least a first subset of status data between a local bearer processor (124) and a paired bearer processor (144) located within a different card cage (112). The local bearer processor (124) processes bearer data channels communicating with a remote site (102) through a remote site fiber-optic line (106). A local data interface (128) exchanges data contained in the bearer data channels between the local bearer processor (124) and a local user data network (114). The local data interface (128) also exchanges at least a second subset of the status data with the paired bearer processor (144) through the local user data network (114).

Abstract: A land-based cable station is provided for interfacing with first and second undersea transmission segments of an undersea optical transmission system. At least one first bypass optical transmission path is provided for selectively coupling reflectometry probe signals and backscattered and reflected signals located at a prescribed wavelength from a first interface device to a second interface device. At least one second bypass optical transmission path is provided for selectively coupling reflectometry probe signals and backscattered and reflected signals located at a prescribed wavelength from the second interface device to the first interface.

Abstract: Method and apparatus for dynamic provisioning of reliable connections in the presence of multiple failures in optical networks are described. One embodiment is a method for allocation of protection paths after a failure in an optical network. The method comprises, responsive to a failure in an active lightpath, switching traffic on the active lightpath to a protection path; subsequent to the switching, identifying all active lightpaths in the network that no longer have an available protection path; and attempting to allocate a protection path to each of the identified active lightpaths.

Abstract: The present invention provides an optical signal transmission apparatus for carrying out bi-directional light transmission. The optical signal transmission apparatus includes: a light sending module, for sending an optical main-signal having at least one data width, and receiving an optical sub-signal including a control signal; a light receiving module for receiving the optical main-signal and sending the optical sub-signal; and an optical cable for connecting between the light sending module and the light receiving module, wherein the light sending module comprises a control component which controls the output of the optical main-signal such that the output of the optical main-signal is stopped, when the optical sub-signal, which includes as data the reception status of the optical main-signal, is not being received, or when the reception status of the optical main-signal is indicating non-receiving.

Abstract: An apparatus for shared optical performance monitoring (OPM) is provided. A wavelength sensitive device receives light at an input port and routes it wavelength selectively to a set of output ports. To perform optical performance monitoring on the output ports, a monitoring component of each output signal is extracted, and these monitoring components are then combined. A single OPM function is then performed on the combined signal. However, with knowledge of the wavelengths that were included in each output signal, a virtual OPM function can be realized for each output port. The per port functionality can include total power per port, power per wavelength per port, variable optical attentuation, dynamic gain equalization, the latter two examples requiring feedback.

Abstract: In an optical transmission system: a first unit generates a first optical supervisory signal being arranged on the shorter-wavelength side of main signals and containing information for determining continuity of an optical transmission line and a second optical supervisory signal arranged on the longer-wavelength side of the main signals and used for supervisory control of optical communication; a second unit generates a wavelength-multiplexed signal by optically multiplexing the main signals and the first and second optical supervisory signals, and transmits the wavelength-multiplexed signal onto the optical transmission line; a third unit receives the wavelength-multiplexed signal, and optically demultiplexes the wavelength-multiplexed signal into the main signals and the first and second optical supervisory signals; and a fourth unit determines whether or not the optical transmission line is optically continuous, based on the first optical supervisory signal, and performs supervisory control of optical com

Abstract: A method and system for network wide fault isolation in an optical network are described. A single fault in a network can produce a large number of alarms at different points in an optical network. The described method and system identify the root cause alarm while masking all correlated alarms. In the embodiment of the invention, the method and system are based on a wavelength tracker technology allowing identification and tracking of individual channels in the optical network.

Abstract: A transmission apparatus that receives an optical signal by selecting any one of a plurality of provided optical signal transmission paths through protection control is configured to include a plurality of optical signal outputting sections that output the optical signals transmitted through said optical signal transmission paths respectively as optical signals having wavelengths that are different from each other, a wavelength selective optical switch capable of selectively outputting light of a wavelength corresponding to any one of the optical signals coming from the optical signal outputting sections on the basis of the frequency of a controlling frequency signal, and an optical switch controlling section that supplies said controlling frequency signal to the wavelength selective optical switch so as to output the optical signal coming from the optical signal transmission path side that is selected by said protection control among the optical signals coming from the optical signal outputting sections.

Abstract: A method and system are provided for remotely monitoring undersea cable systems. Upon receiving a fault alert message, an optical cross-connect is set up between the subject cable station and a testing platform. Testing is conducted and a determination is made whether the fault is in the undersea portion of the network, or in the terrestrial backhaul. By making that determination early, unnecessary technician travel is reduced.

Abstract: The present invention discloses a method for handling channel failures in an Automatically Switched Optical Network (ASON). When a channel alarm occurs, the head service node decides whether the channel alarm is incurred by a channel failure according to the alarm message or alarm information. If so, the head and end service nodes continue to locate whether the channel failure is inside or outside the network by combining local detection and message notification. If the channel failure is an internal failure, rerouting is activated to locate and remove the channel failure. When this method is used to locate a channel failure, the amount of information exchanged is small. The method may quickly identify the accurate position of a failure inside the network, improve the efficiency in removing failures, and minimize the damages to services, with little harm to equipment functioning and network performance.

Abstract: A transmission line monitoring apparatus includes a first optical coupling unit, a first optical dividing unit, a second optical coupling unit, a second optical dividing unit and a monitoring unit. The first optical coupling unit couples a down data signal with a first wavelength and an examination signal with a second wavelength into a first coupled signal. The first optical dividing unit receives the first coupled signal and divides the first coupled signal into the down data signal with the first wavelength and the examination signal with the second wavelength. The second optical coupling unit couples an up data signal with the first wavelength and the examination signal from the first optical dividing unit into a second coupled signal. The second optical dividing unit receives the second coupled signal and divides the second coupled signal into the up data signal with the first wavelength and the examination signal with the second wavelength.

Abstract: A modular cross connect system for optical telecommunication networks has the optical unit divided in at least two main bodies with one section for connection comprising the collimators and a main commutation section with MEMS devices. The first section is a fixed part while the second section is a readily removable section. The two sections face each other through a window and, in the first section, optics are provided for steering all or part of the optical signals from and to the main MEMS unit to a MEMS standby or protection plane to allow replacement of the main MEMS unit without interrupting service.

Abstract: A method and system provide capacity-efficient restoration within an optical fiber communication system. The system includes a plurality of nodes each interconnected by optical fibers. Each optical fiber connection between nodes includes at least three channel groups with different priority levels for restoration switching in response to a connection failure. The system maintains and restores full-capacity communication services by switching at least a portion of the channel groups from a first optical fiber connection to a second optical fiber connection system based on the priority levels assigned to the channel groups. Service reliability is effectively maintained without incurring additional costs for dedicated spare optical fiber equipment by improving idle capacity utilization.

Abstract: Five electronic control units (ECU) control vehicle devices using CAN protocol. Each of ECUs is provided with a resistor and a switch for activating the resistor. A first and fifth ECUs are arranged on the leftmost and rightmost ends. Resistors of the first and fifth ECUs are used as terminating resistors to a two-wire communications line. When the two-wire communications line is broken, the first ECU sends a test signal while other ECUs excluding the fifth ECU turn on the switches from right to left. When the test signal can be received, a broken point is located on the right side of ECU that turns on its switch at this time. Thereafter ECUs on the left side of the broken point conduct communication.

Abstract: Transparent network elements (10) pass data in a data communication plane (24) over optical links (42) and pass control information in a control communication plane (22) over a out-of-fiber/out-of-band (OF/OB) network (44), such as an IP-based network. Previously developed protection state machines (38), such as those used in traditional SONET/SDH systems can be used along with new protection state machines (38), such as shared ring protection state machines. Client State machines (40) and a signaling controller (30) interface between the protection state machines (38) and the OF/OB network (44) such that the protection state machines (38) are isolated from the technicalities of transmission in the separate network.

Abstract: Embodiments of the present invention disclose a method for detecting an upstream timeslot conflict in a Passive Optical Network (PON). An Optical Line Terminal (OLT) detects a timeslot conflict in an upstream timeslot. An OLT is provided also, including an optical receiver, an optical transmitter, a control unit and a detection unit. The detection unit receives an optical signal from the optical receiver, samples instantaneous optical power of the optical signal in an upstream timeslot, compares the instantaneous optical power with normal upstream optical power of the upstream timeslot, and detects that a timeslot conflict occurs in the upstream timeslot when the instantaneous optical power exceeds normal upstream optical power of the upstream timeslot. Embodiments of the present invention make the costs lower to detect an upstream timeslot conflict in the PON.

Abstract: An optical communication system has two or more active interfaces, each controlling the transmission and reception of optical signals between a communication network and one or more subscriber terminals according to control information pertaining to the individual subscriber terminals. The control information used by all the active interfaces is stored in a memory. The optical communication system also has a standby interface that is functionally equivalent to the active interfaces, and an optical switching apparatus that switches data transmission paths among the network, the active and standby interfaces, and the subscriber terminals. If a fault is detected in an active interface, the standby interface extracts the control information of the faulty interface from the memory, and the optical switching apparatus switches the data transmission paths so that the standby interface replaces the faulty interface.