Provided are a method and system for improving bandwidth allocation efficiency, relating to optical communication field. In a PON system, an ONU detects each TCONT of the ONU in real time, and sends to an OLT a private message used for reporting buffer overflow when detecting that buffer overflow occurs on a TCONT; the OLT sends, according to the received private message used for reporting the buffer overflow, to the ONU a private message used for instructing the ONU to activate an overflow allocation mechanism; after receiving the private message used for instructing the ONU to activate the overflow allocation mechanism, the ONU activates the overflow allocation mechanism, calculates an actual traffic of a buffer of the TCONT, and sends the actual traffic of the buffer of the TCONT to the OLT; and the OLT dynamically allocates bandwidth to the TCONT according to the actual traffic of the buffer of the TCONT.

An intranodal reconfigurable optical add/drop multiplexer (ROADM) fiber management apparatus, and a system employing the apparatus. The apparatus comprises a plurality of ingress optical ports, a plurality of egress optical ports, and a plurality of optical interconnections interposed between ones of the plurality of ingress optical ports and ones of the plurality of egress optical ports. Each of the plurality of ingress optical ports corresponds to one of the plurality of egress optical ports. Each one of the plurality of ingress optical ports is optically coupled by way of the optical interconnections to at least one of the plurality of egress optical ports. Each one of the plurality of egress optical ports is optically coupled by way of the optical interconnections to at least one of the plurality of ingress optical ports.

A fixed communication network is disclosed in which a plurality of transmitters feed signals via tributary transmission lines of different lengths onto a shared network component. A timing reference signal is distributed to the transmitters. The shared network component in some embodiments takes the form of a transmission line. In order to enable the sharing of the capacity of the shared network component, each of the plurality of transmitters codes data for transmission in accordance with a code division multiple access scheme. The efficiency of usage of the shared network component is improved by synchronizing the arrival of the encoded bits at the shared network component. This is achieved by populating a store within each transmitter with a pre-set timing offset, and timing the transmission of data in accordance with the timing reference signal received by the transmitters and the pre-set timing offset.

In the optical transport system a transport frame generator divides a transport frame accommodating plural client signals into plural transmission signals. Subcarrier transmission units convert the signals into optical signals using different optical carriers and transmit the converted optical signals. Subcarrier reception units receive the transmitted optical signals and convert the optical signals into reception signals. A transport frame termination unit combines the reception signals to restore the transport frame. A time-demultiplexing processor time-demultiplexes the restored transport frame to be separated into the client signals. A time slot control unit determines a new time slot allocation when time-multiplexing the client signals in the transport frame and stops supply of electric power to a subcarrier transmission unit and a subcarrier reception unit that transmit and receive an optical signal to which the client signals are not allocated.

A node (20, 25) for a single fiber bidirectional WDM optical ring network has a first optical protection switch (100) having first and second ports for coupling to the single fiber bidirectional ring, while providing a pass through optical path for wavelengths on the bidirectional ring. A further port is coupled to an external optical path. In operation the switch couples optically bidirectional selected wavelengths between the external optical path and either of the first and second ports selectively, according to an indication of a fault on the ring, so as to use different portions of the bidirectional ring respectively as working path and protection path. This combines coupling wavelengths with the ring, with the selection of protection or working path, which simplifies the optical equipment, and upstream and downstream optical delays can be symmetrical.

[Problem] It is possible to cancel out beat noises in a WDM signal to obtain a high-quality signal component, and a configuration thereof is achieved with low mounting costs. [Solution] An optical reception device converts a WDM signal rs(t) of an optical signal to electrical signals d(t)1 to d(t)n expressed as complex numbers of orthogonal phases, cancels out beat noises from the electrical signals, and then demodulates the signals to obtain signals D1 to Dn of a transmission source. This optical reception device includes an absolute value calculation units 31a to 31n that generate a signal component including a beat noise component through absolute value squaring calculation processing for squaring an absolute value of the electrical signal, scaling units 32a to 32n that multiply the generated beat noise component by a proportional constant to restore beat noise associated with n types of wavelengths in the electrical signal, and subtraction units 33a to 33n that subtract the n type of beat noises restored from the electrical signal to cancel out then types of beat noises included in the electrical signal.

A transmission apparatus includes: a first obtaining section configured to obtain a first transmission characteristic in communication of a multi-carrier signal through a transmission path between the transmission apparatus and a distant transmission apparatus; a second obtaining section configured to obtain a second transmission characteristic under a predetermined usage condition within a specified performance range of the transmission apparatus; a correcting section configured to correct the first transmission characteristic according to the second transmission characteristic; and a determining section configured to determine an amount of allocation for each subcarrier included in the multi-carrier signal, according to the first transmission characteristic that has been corrected by the correcting section.

A transmission apparatus includes: a first obtaining section configured to obtain a first transmission characteristic in communication of a multi-carrier signal through a transmission path between the transmission apparatus and a distant transmission apparatus; a second obtaining section configured to obtain a second transmission characteristic under a predetermined usage condition within a specified performance range of the transmission apparatus; a correcting section configured to correct the first transmission characteristic according to the second transmission characteristic; and a determining section configured to determine an amount of allocation for each subcarrier included in the multi-carrier signal, according to the first transmission characteristic that has been corrected by the correcting section.

Aspects described herein include an optical apparatus comprising a multiple-stage arrangement of two-mode Bragg gratings comprising: at least a first Bragg grating of a first stage. The first Bragg grating is configured to transmit a first two wavelengths and to reflect a second two wavelengths of a received optical signal. The optical apparatus further comprises a second Bragg grating of a second stage. The second Bragg grating is configured to transmit one of the first two wavelengths and to reflect an other of the first two wavelengths. The optical apparatus further comprises a third Bragg grating of the second stage. The third Bragg grating is configured to transmit one of the second two wavelengths and to reflect an other of the second two wavelengths.

Aspects described herein include an optical apparatus comprising a multiple-stage arrangement of two-mode Bragg gratings comprising: at least a first Bragg grating of a first stage. The first Bragg grating is configured to transmit a first two wavelengths and to reflect a second two wavelengths of a received optical signal. The optical apparatus further comprises a second Bragg grating of a second stage. The second Bragg grating is configured to transmit one of the first two wavelengths and to reflect an other of the first two wavelengths. The optical apparatus further comprises a third Bragg grating of the second stage. The third Bragg grating is configured to transmit one of the second two wavelengths and to reflect an other of the second two wavelengths.