A Dual Parallel (DP)-Inphase/Quadrature (I/Q) Mach-Zehnder Modulator (MZM) bias controller configured to generate a pair of orthogonal dither signals; multiply the pair of dither signals to create a second order orthogonal dither signal; and lock an Inphase (I) I MZM of a DP-I/Q MZM to a value of a corresponding I component of a transmission signal by applying the pair of orthogonal dither signal to a Quadrature (Q) MZM and a Phase (P) MZM of the DP-I/Q MZM; applying an I bias signal to the I MZM of the DP-I/Q MZM; detecting an output of the DP-I/Q MZM; and determining an I error signal in the output of the I MZM of the DP-I/Q MZM based on the product of second order dither signal and the output of the DP-I/Q MZM.

A method for allocating a point-to-point channel to a user module of an optical communication network. The network includes user modules and optical terminations, and supports point-to-multipoint channels and a plurality of point-to-point channels, one same point-to-point channel being assigned to one single optical termination. The method is implemented for a user module called a requester user module, and includes: detecting a predetermined availability signal conveyed by a point-to-point channel of the plurality of point-to-point channels; and allocating the point-to-point channel over which the predetermined availability signal is conveyed, called available point-to-point channel, to the requester user module.

Provided is a transmission circuit with which it is possible to facilitate error correction of burst errors without increasing the processing load in multiframes configured from a plurality of OTN frame signals. This transmission circuit is provided with: a transmission-side signal recognition unit for detecting MFAS and recognizing the order of N number of OTN frame signals; an intra-multiframe sequence conversion unit for converting the sequence of data signals inside the multiframe in response to the recognized order; a transmission-side rearranging unit for consolidating the sequentially converted data signals into lengths equal to those of the OTN frame signals and creating N number of quasi-OTN frame signals; and a transmission unit for transmitting the multiframes configured from the N number of quasi-OTN frame signals.

Provided is a transmission circuit with which it is possible to facilitate error correction of burst errors without increasing the processing load in multiframes configured from a plurality of OTN frame signals. This transmission circuit is provided with: a transmission-side signal recognition unit for detecting MFAS and recognizing the order of N number of OTN frame signals; an intra-multiframe sequence conversion unit for converting the sequence of data signals inside the multiframe in response to the recognized order; a transmission-side rearranging unit for consolidating the sequentially converted data signals into lengths equal to those of the OTN frame signals and creating N number of quasi-OTN frame signals; and a transmission unit for transmitting the multiframes configured from the N number of quasi-OTN frame signals.

An optical system is provided comprising a first node and a channel drop add device. The first node is configured to transmit data onto an optical fiber in a first line direction. The channel drop add device (501) is adapted to receive and add channels onto the optical fiber thereby transmitting the data into the first and a second line direction. The network further comprises a second node configured to form a transmitter/receiver function. The second node is configured to receive data on said optical fiber from said first and second line directions. Further, the second node is adapted to synchronize received data from said first and second line directions by delaying the data signals seeing the shortest delay, by a delay device.

An optical system is provided comprising a first node and a channel drop add device. The first node is configured to transmit data onto an optical fiber in a first line direction. The channel drop add device (501) is adapted to receive and add channels onto the optical fiber thereby transmitting the data into the first and a second line direction. The network further comprises a second node configured to form a transmitter/receiver function. The second node is configured to receive data on said optical fiber from said first and second line directions. Further, the second node is adapted to synchronize received data from said first and second line directions by delaying the data signals seeing the shortest delay, by a delay device.

A method for allocating bandwidth to a first ONU, a second ONU, M.sub.1 ONUs, and M.sub.2 ONUs includes, during an allocation cycle, (i) granting a respective upstream time slot to, of a plurality of N ONUs, only each of the M.sub.1 ONUs, and (ii) granting a first upstream time slot to the first ONU. Each of the M.sub.1 ONUs and M.sub.2 ONUs is one of the plurality of N ONUs. The method also includes, during a subsequent cycle, (i) granting a respective upstream time slot to, of the plurality of N ONUs, only each of the M.sub.2 ONUs. The N ONUs includes a skipped-ONU that is one of either, and not both, the M.sub.1 ONUs and the M.sub.2 ONUs. The method includes, during the subsequent allocation cycle, granting a second upstream time slot to a second ONU, which is not one of the plurality of N ONUs.

There is provided a communication method used in a communication system in which a plurality of communication apparatuses is connected by an optical ring network, the communication method including: setting one of the plurality of communication apparatuses as a master communication apparatus and the other communication apparatuses as slave communication apparatuses, causing the master communication apparatus to transmit an optical signal at transmission timing determined in the master communication apparatus; causing the master communication apparatus to transmit an assignment signal for assigning, to the slave communication apparatuses, transmission timing at which an optical signal on at least one wavelength is time-division multiplexed and transmitted; and causing the slave communication apparatuses to transmit an optical signal to the optical ring network based on transmission timing assigned by the assignment signal received from the master communication apparatus. As a result, the number of wavelengths needed for communication is reduced, and even when communication paths increases due to an increase in the number of optical transmission apparatuses, there is no need to increase the number of wavelengths, thereby solving the problem in economic efficiency.

A network or system in which a hub or primary node may communicate with a plurality of leaf or secondary nodes. The hub node may operate or have a capacity greater than that of the leaf nodes. Accordingly, relatively inexpensive leaf nodes may be deployed to receive data carrying optical signals from, and supply data carrying optical signals to, the hub node. One or more connections may couple each leaf node to the hub node, whereby each connection may include one or more spans or segments of optical fibers, optical amplifiers, optical splitters/combiners, and optical add/drop multiplexer, for example. Optical subcarriers may be transmitted over such connections, each carrying a data stream. The subcarriers may be generated by a combination of a laser and a modulator, such that multiple lasers and modulators are not required, and costs may be reduced. As the bandwidth or capacity requirements of the leaf nodes change, the number of subcarriers, and thus the amount of data provided to each node, may be changed accordingly. Each subcarrier within a dedicated group of subcarriers may carry OAM or control channel information to a corresponding leaf node, and such information may be used by the leaf node to configure the leaf node to have a desired bandwidth or capacity.

A network or system in which a hub or primary node may communicate with a plurality of leaf or secondary nodes. The hub node may operate or have a capacity greater than that of the leaf nodes. Accordingly, relatively inexpensive leaf nodes may be deployed to receive data carrying optical signals from, and supply data carrying optical signals to, the hub node. One or more connections may couple each leaf node to the hub node, whereby each connection may include one or more spans or segments of optical fibers, optical amplifiers, optical splitters/combiners, and optical add/drop multiplexer, for example. Optical subcarriers may be transmitted over such connections, each carrying a data stream. The subcarriers may be generated by a combination of a laser and a modulator, such that multiple lasers and modulators are not required, and costs may be reduced. As the bandwidth or capacity requirements of the leaf nodes change, the number of subcarriers, and thus the amount of data provided to each node, may be changed accordingly. Each subcarrier within a dedicated group of subcarriers may carry OAM or control channel information to a corresponding leaf node, and such information may be used by the leaf node to configure the leaf node to have a desired bandwidth or capacity.