Abstract: A bandwidth allocation apparatus and method for providing a low-latency service in an optical network that may guarantee low-latency requirements and improve a network utilization rate by allocating a static bandwidth to an ONU requiring low latency within an allocable bandwidth and by allocating a dynamic bandwidth to an ONU not requiring the low latency within a remaining bandwidth.

Abstract: Wavelength channels used in the optical network system are classified into downstream channels used to transmit optical signals from an optical line terminal (OLT) to an optical network unit (ONU) and upstream channels that are used to transmit optical signals from the ONU to the OLT. The wavelength channels are included in an O-band and may not overlap each other. One of the upstream channels are allocated to a wavelength band (for example, a zero-dispersion window) in which a four-wave mixing occurs. A wavelength spacing between the upstream channels and the downstream channels is determined based on a performance of separating the upstream channels and the downstream channels in a bidirectional optical sub assembly (BOSA) of the ONU. Also, a wavelength spacing between the downstream channels is determined based on a performance of separating the downstream channels in the BOSA.

Abstract: An optical line terminal (OLT) accumulates and stores a user frame for each physical layer identifier (PLID) to efficiently use a plurality of lanes used for downstream transmission from the OLT to an optical network unit (ONU). The OLT envelopes payloads that are accumulatively stored for the respective PLIDs based on a transmission rate supported by a corresponding ONU, combines an envelope header based on an envelope payload unit, and transmits an envelope frame. The OLT selects an available lane from among a plurality of lanes and may transmit the envelope frame through the selected lane.

Abstract: An optical network unit (ONU) for optical transmission in a burst mode includes an electro-absorption modulated laser (EML) transmitter including a laser diode (LD) and configured to transmit an uplink optical signal through the LD, an electro-absorption modulator (EAM) driver integrated circuit (IC) (EAM driver IC) configured to amplify an uplink data signal and provide the amplified data signal to the EML transmitter, an LD burst-mode driving circuit configured to control an operation of turning on or off the LD based on a burst-enable signal, and a media access control (MAC) configured to transmit the data signal to the EAM driver IC and transmit the burst-enable signal to the LD burst-mode driving circuit.

Abstract: An optical network unit (ONU) for optical transmission in a burst mode includes an electro-absorption modulated laser (EML) transmitter including a laser diode (LD) and configured to transmit an uplink optical signal through the LD, an electro-absorption modulator (EAM) driver integrated circuit (IC) (EAM driver IC) configured to amplify an uplink data signal and provide the amplified data signal to the EML transmitter, an LD burst-mode driving circuit configured to control an operation of turning on or off the LD based on a burst-enable signal, and a media access control (MAC) configured to transmit the data signal to the EAM driver IC and transmit the burst-enable signal to the LD burst-mode driving circuit.

Abstract: An optical line terminal (OLT) accumulates and stores a user frame for each physical layer identifier (PLID) to efficiently use a plurality of lanes used for downstream transmission from the OLT to an optical network unit (ONU). The OLT envelopes payloads that are accumulatively stored for the respective PLIDs based on a transmission rate supported by a corresponding ONU, combines an envelope header based on an envelope payload unit, and transmits an envelope frame. The OLT selects an available lane from among a plurality of lanes and may transmit the envelope frame through the selected lane.

Abstract: A radio-over-fiber (RoF) transmission system includes at least one baseband unit (BBU) connected to a core network of a service provider that provides a mobile Internet service, an optical line terminal (OLT) configured to convert a radio signal received from the at least one BBU into an optical signal, an optical distribution network (ODN) comprising an optical fiber and an optical splitter, at least one optical network unit (ONU) configured to receive the optical signal from the OLT via the ODN and convert the optical signal into a radio signal, and at least one remote radio head (RRH) configured to receive the radio signal from the at least one ONU and output the radio signal via a plurality of antennas.

Abstract: A method of registering an optical network unit (ONU) in an optical line terminal (OLT). The OLT determines a lane to be used by the ONU based on a transmission rate supported by the ONU, combines or distributes data of a dataflow based on a rate of the lane by comparing the rate of the lane to a rate of the dataflow of a media access control (MAC) client interface, and, when the OLT and the ONU are connected through multiple lanes, transmits and receives data between the OLT and the ONU through channel bonding for more effective use of a network.

Abstract: A host unit is provided between a remote radio head and a radio unit. The host unit performs a conversion between a digital optical signal used by the remote radio head and an analog optical signal used by the radio unit. A frequency of the analog optical signal converted by the host unit may be an intermediate frequency. The radio unit performs a conversion between an analog optical signal used by the host unit and an analog radio signal used by a user terminal. A frequency of the analog radio signal may be included in a millimeter wave band or radio frequency band.

Abstract: Provided is an analog optical transmission system using a dispersion management technique. The analog optical transmission system may include a digital unit (DU) pool including a plurality of DUs to transmit an optical signal; a plurality of radio units (RUs) to receive the optical signal; and one or more dispersion management apparatus to remove a signal distortion component caused by an interaction between a chirp and chromatic dispersion by compensating for the chromatic dispersion before the plurality of RUs receives the optical signal that is transmitted from the DU pool.

Abstract: An apparatus for transmitting a control signal in a radio-over-fiber (RoF)-based mobile fronthaul includes: a data channel transmitter configured to generate a data signal at a preassigned frequency or wavelength; a control channel transmitter configured to generate a control signal at a designated frequency or wavelength that is shared with other apparatuses; and a combiner configured to combine the data signal with the control signal.

Abstract: A remote radio head disposed between a baseband unit and a host unit. The remote radio head may transmit and receive a digital optical signal to the baseband unit, transmit and receive an analog optical signal to the host unit, and convert the digital optical signal and the analog optical signal, a frequency of the analog optical signal transmitted and received by the remote radio head and the host unit may be an intermediate frequency of a baseband, the host unit may be disposed between the remote radio head and a radio unit, the host unit and the radio unit may transmit and receive the analog optical signal, and the frequency of the analog optical signal transmitted and received by the host unit and the radio unit may be the intermediate frequency with a baseband signal.

Abstract: A bidirectional optical element in optical network units (ONUs) of a passive optical network (PON) includes a main filter configured to pass an upstream signal having an upstream-channel wavelength and a downstream signal having a downstream-channel wavelength, a drop filter configured to pass the downstream signal having the downstream-channel wavelength and reject the upstream signal having the upstream-channel wavelength, and an add filter configured to pass the upstream signal having the upstream-channel wavelength and reject the downstream signal having the downstream-channel wavelength, wherein the main filter, the drop filter, and the add filter are configured to share a single optical waveguide, and the optical waveguide is configured to connect input ports of the main filter and the drop filter and an output port of the drop filter and is provided in a straight line shape.

Abstract: An optical signal transmission system and method of allocating center frequencies of intermediate frequency (IF) carriers in a frequency division multiplexing (FDM) optical fiber link. The optical signal transmission method includes determining a center frequency interval between modulated signals based on a bandwidth of the modulated signals or a center frequency of a modulated signal having a lowest center frequency, among the modulated signals, reallocating center frequencies to the modulated signals based on the center frequency interval between the modulated signals, and converting the modulated signals reallocated the center frequencies from electrical signal into optical signal and transmitting the optical signal.

Abstract: An optical line terminal (OLT) and an optical network unit (ONU) configured to generate a plurality of fragments by fragmenting a media access control (MAC) frame and to transmit the plurality of generated fragments, when a length of the MAC frame is greater than or equal to a maximum transmission unit (MTU).

Abstract: A remote radio head disposed between a baseband unit and a host unit. The remote radio head may transmit and receive a digital optical signal to the baseband unit, transmit and receive an analog optical signal to the host unit, and convert the digital optical signal and the analog optical signal, a frequency of the analog optical signal transmitted and received by the remote radio head and the host unit may be an intermediate frequency of a baseband, the host unit may be disposed between the remote radio head and a radio unit, the host unit and the radio unit may transmit and receive the analog optical signal, and the frequency of the analog optical signal transmitted and received by the host unit and the radio unit may be the intermediate frequency with a baseband signal.

Abstract: A host unit is provided between a remote radio head and a radio unit. The host unit performs a conversion between a digital optical signal used by the remote radio head and an analog optical signal used by the radio unit. A frequency of the analog optical signal converted by the host unit may be an intermediate frequency. The radio unit performs a conversion between an analog optical signal used by the host unit and an analog radio signal used by a user terminal. A frequency of the analog radio signal may be included in a millimeter wave band or radio frequency band.

Abstract: Wavelength channels used in the optical network system are classified into downstream channels used to transmit optical signals from an optical line terminal (OLT) to an optical network unit (ONU) and upstream channels that are used to transmit optical signals from the ONU to the OLT. The wavelength channels are included in an O-band and may not overlap each other. One of the upstream channels are allocated to a wavelength band (for example, a zero-dispersion window) in which a four-wave mixing occurs. A wavelength spacing between the upstream channels and the downstream channels is determined based on a performance of separating the upstream channels and the downstream channels in a bidirectional optical sub assembly (BOSA) of the ONU. Also, a wavelength spacing between the downstream channels is determined based on a performance of separating the downstream channels in the BOSA.

Abstract: An optical signal receiving apparatus included in an optical line terminal (OLT) includes a resistor disposed between a capacitor connected to a receiving optical sub-assembly (ROSA) and a limiting amplifier, wherein a resistance value of the resistor may be determined based on the OLT receives an optical signal from an optical network unit (ONU) and whether the ONU transmitting the optical signal to the OLT is switched, the resistance value of the resistor may be determined to reduce a data loss occurring from the optical signal receiving apparatus in response to the OLT receiving the optical signal from the ONU, and the resistance value of the resistor may be determined such that the optical signal receiving apparatus more rapidly follows a change in intensity of the optical signal in response to the ONU transmitting the optical signal to the OLT being switched.

Abstract: A flexible printed circuit board (FPCB) for an optical module includes: a signal via pad connected with a signal lead pin of the optical module; a ground layer spaced apart from the signal via pad; an isolation gap formed between the signal via pad and the ground layer; and a protective layer which is formed at a portion that comprises the isolation gap, and which, when connected with the signal via pad, compensates for parasitic inductance caused by a protruding signal lead pin.