Abstract: A hub for use in a passive optical network (PON) includes a transmission fiber on which an information-bearing optical signal is received, a double-cladded, rare-earth doped fiber located along the transmission fiber for imparting gain to the information-bearing optical signal, and a combiner having an output coupled to the transmission fiber and a plurality of inputs. The output is coupled to the transmission fiber such that optical energy at pump energy wavelengths but not signal wavelengths are communicated therebetween. At least one pump source is optically coupled to one of the inputs of the combiner for providing optical pump energy to the double-cladded, rare-earth doped fiber. An optical splitter is also provided. The optical splitter has an input coupled to the transmission fiber for receiving an amplified, information-bearing optical signal and a plurality of outputs for directing portions of the amplified, information-bearing optical signal to remote nodes in the PON.

Abstract: A method and a system in which selected wavelengths of a wavelength division multiplexed (WDM) signal are modulated with multicast data for multicasting data services on an optical network. The WDM signal is received from a hub node of the optical network, such as a unidirectional ring network or a bi-directional ring network. A four-port wavelength crossbar switch (4WCS) selectably switches selected wavelengths from the optical network to a modulator loop. The modulator loop includes a multicast modulator that modulates the selected plurality of wavelengths with the multicast data. Each modulated wavelength is then switched back to the optical network by the 4WCS switch, and sent to a plurality of subscriber nodes of the optical network. This architecture allows a facility provider to be physically separated from a content provider, and affords the flexibility of selectively delivering multicast content to individual subscribers.

Abstract: An optical conversion device for a shared FTTH distribution network including first and second optical fibers and an optical processing circuit. The optical processing circuit has an input for receiving a first optical analog signal carried by the first optical fiber and an output for providing a first optical digital signal for transmission via the second optical fiber. The optical processing circuit is configured to digitize the first optical analog signal and incorporate into the first optical digital signal. The optical analog signal may be an optical signal which is modulated by an RF signal, which is the same or similar to that of existing HFC networks. High loss electrical signals are converted to low-loss optical signals propagated within the optical plant. The combined optical analog and digital protocol supports analogous communications of existing HFC networks and the optical plant minimizes cost of fiber optic upgrade.

Abstract: Various methods and apparatuses are described for a wavelength division multiplexing passive optical network (WDM-PON) that performs bi-directional communication. The WDM-PON may include two or more remote distribution nodes in between a central office and the most distant optical network unit. Each remote distribution node is located in a physically separate location. A first remote distribution node has two or more optical network units connected to the first remote distribution node. Each remote node separates one or more wavelength channels from a composite optical signal distributed through that remote distribution node.

Abstract: A self-healing passive optical network is disclosed. The network includes a central office and a remote node connected to the central office through a main optical fiber. The remote node transmits one portion of power of the upstream optical signal, which has been input from each of the optical network units, to the central office, and returning a remaining portion of the power of the upstream optical signal to the optical network unit. The network also includes a plurality of optical network units connected to the remote node through a plurality of distribution optical fibers. Each of the optical network units transmits an upstream optical signal to the remote node through the directly connected distribution optical fiber, and detects abnormality occurrences from a state of the upstream optical signal returning from the remote node.

Abstract: An optical network provides a digital interconnect fabric allowing nodes to seamlessly communicate with each other. Each node is connected to a bi-directional optical bus through passive optical interface devices. The optical interface devices route signals from each node onto the bus in both directions and also route signals traveling along the bus in either direction to each node. The optical interface devices and optical bus are passive and do not involve any regeneration of the electrical signals. The nodes are assigned wavelengths of transmission and have tunable receivers for selecting a wavelength of reception. The digital interconnect fabric facilitates Ethernet, Fibre Channel, and other digital communication protocols.

Abstract: An optical aggregation device can couple a plurality of optical line terminals to a common plurality of optical network terminals. The device is coupled to the network terminals via a passive optical network. The aggregation device makes it possible to more fully use all of the available bandwidth of the passive optical network.

Abstract: A broadcast/communication convergence system, and an FTTH (Fiber To The Home) system that can accommodate broadcast signals of various channels and variable band signals by converging broadcast and communication signals and transmitting the converged broadcast and communication signals using an IEEE 1394 transmission method serving as a standard interface in the FTTH system for broadcast/communication convergence. An OLT (Optical Line Terminal) transfers a plurality of broadcast signals and a communication signal received from external broadcast and communication providers through a single optical signal (A).

Abstract: A wavelength-division multiplexed self-healing passive optical network is capable of detecting cut-off and deterioration of feeder fiber and distribution fiber and restoring a network with a star structure. The network includes a central office, a remote node, and a plurality of subscriber units. Working and protection feeder fibers connect the central office to the remote node. A reflection unit at an end of the remote node connects to the central office for reflecting a monitoring optical signal transmitted from the central office. An output monitor stage at an end of the central office connects to the remote node for detecting the reflected monitoring optical signal and generating a control signal based on the presence of abnormality of the working and protection feeder fibers.

Abstract: Analog video signals are communicated from multiple service providers to subscribers by using analog optical carriers. Unlike digital optical carriers that typically support data services or IP TV, analog optical carriers that can be demodulated or translated back into the analog radio-frequency (RF) signals do not require additional and costly hardware for reception by a RF receiving device such as a television (TV) set. With the present invention, a TV set does not need significant digital hardware such as a digital set top box to allow the TV set to view video signals from a desired service provider. The present invention can allow a plurality of competing service providers to offer video services to a subscriber through a single optical network.

Abstract: A PON and a method of transmitting data employing different upstream and downstream transmission protocols are disclosed. The PON includes: a plurality of ONTs; WDM filters; an OLT receiving and transmitting optical signals to and from the ONTs and a higher network; and an optical coupler. The ONT includes a first switching unit, a level transformer converting two level Ethernet signals into a three level data signals, a first code generator generating a specific CDMA codes that distinguish the ONT from another ONT, and a first multiplier performing a spread spectrum function with the CDMA codes. The OLT includes an optical receiver, a branching filter branching the upstream CDMA signals, a plurality of second code generators generating codes for despread, a plurality of second multipliers multiplying the received signals by the despread codes, and a plurality of data decider extracting data through correlation calculation.

Abstract: The present invention relates to a WDM/SCM-PON and a media access control method for asymmetric packet communication in the same. In the WDM/SCM-PON, each SCM channel is classified and used as a link by adopting an SCM technique of subdividing a wavelength band of up/downstream data links between an OLT and ONTs into frequency bands, and the ONTs are formed so that a certain SCM channel is independently distributed not fixedly assigned. Accordingly, an inventory problem, which can be generated in WDM/SCM, is prevented before happens, asymmetric dynamic band allocation is performed, and asymmetric service of up/downstream transmission is supported. As a result, a band required for next generation service is dynamically provided, optical interference effect is minimized, and Ethernet compatibility is provided so that Ethernet service suitable for providing IP service can be accommodated.

Abstract: Disclosed is a wavelength-division-multiplexed passive optical network using a wavelength-locked optical transmitter.

Abstract: An optical module includes a transmitter optical sub-assembly comprising a transmitter configured to emit a multi-longitudinal-mode (MLM) spectrum signal having an emission spectrum comprising a plurality of distinct narrow-spectrum peaks each corresponding to a longitudinal mode in the transmitter. The emission spectrum can be shifted in wavelength by a change in the transmitter temperature. The optical module also includes a heating and cooling device configured to control the temperature of the transmitter in response to a temperature-control signal and a receiver optical sub-assembly configured to output a pair of differential digital signals in response to an input optical signal.

Abstract: A GE-PON (Gigabit Ethernet Passive Optical Network) apparatus includes a 2×N splitter, an OLT (Optical Line Terminal) connected to the 2×N splitter via a first path line or a second path line, and a switching unit for switching the first path line or the second path line upon receiving a predetermined control signal. An ONU (Optical Network Unit) generates a switching request according to a signal environment and transmits the generated switching request to the OLT.

Abstract: Disclosure is a wavelength division multiplexed-passive optical network having a bus structure capable of connecting one central office to a plurality of remote nodes through one optical fiber.

Abstract: In an optical transmission apparatus in which a plurality of nodes are optically connected to one another via an optical transmission path, a light signal which is coded so that a mixture ratio of 1 and 0 constituting data is made close to 50% is transmitted through the optical transmission path. When a light signal is not emitted from all of the nodes, a dummy signal which is an AC-like signal is emitted to the optical transmission path. Therefore, an optoelectric conversion section can be always set to an active state, and the signal recognizability can be prevented from being lowered.

Abstract: An optical communication system comprises a base station, a plurality of trunk optical fibers connected to the base station, a plurality of star couplers connected to the trunk optical fibers, a plurality of remote stations, and a plurality of branch optical fibers. The branch optical fibers have first branch cut ends at positions adjacent to each of the star couplers and second branch cut ends at positions adjacent to the remote station groups. The first branch cut ends are connected to the second ports of the star couplers and the second branch cut ends to the remote stations of a remote station group.

Abstract: Provided is an ONU that suppresses transmission of a useless multicast control message to a PON section and enables a communication bandwidth of the PON section to be effectively used. The ONU of the PON system has a multicast group management table that shows a correspondence between a multicast group identifier and an address of a user terminal participating in a multicast group. When the ONU receives a request message of participation in the multicast group from the user terminal, the ONU registers the correspondence between the multicast group identifier indicated by the received message and the user terminal address. A new received message is deleted without being sent to the OLT if another user terminal address is registered already, along with a correspondence with the same multicast group identifier, in the multicast group management table.

Abstract: Disclosed is a wavelength division multiplexed passive optical network (WDM PON) system including a central office, a remote Node, and an optical fiber coupled between the central office and the remote node, wherein the central office includes an optical power splitter coupled to the optical fiber, wherein the optical power splitter (1) divides an upstream optical signal from the optical fiber into a plurality of upstream optical signals having substantially similar power and (2) outputs downstream optical signals to the optical fiber, and a plurality of optical transceiver modules to (1) receive the plurality of upstream optical signals, and (2) output the downstream optical signals to the optical power splitter, and wherein at least one of the optical transceiver modules having an optical transmitter including a semiconductor optical amplifier and a reflection-type optical fiber grating located at a predetermined distance from the semiconductor optical amplifier, the optical transmitter transmitting light o

Abstract: An ring type optical LAN device includes a master node and a plurality of slave nodes that are interconnected by an optical fiber cable. A plurality of optical bypass transmission lines are provided in correspondence with each one of the slave nodes. Each of the optical bypass transmission lines bypasses the corresponding one of the slave nodes. Each slave node includes an E/O converter and an optical cutoff circuit. Each of the E/O converters is controlled to flash for generating an optical signal, which is transmitted to a network. When any one of the slave nodes fails such that the corresponding E/O converter is maintained in a turned on state, the associated optical cutoff circuit forcibly switches the E/O converter to a turned off state. This suppresses a network crash caused by the failure maintaining the E/O converter in the turned on state.

Abstract: Disclosed is a broadcast/communication unified passive optical network system.

Abstract: An optical network termination (ONT) apparatus can determine its own geographic location information automatically, thereby permitting the ONT to report its geographic location to a management entity in a passive optical network (PON) automatically, without manual intervention.

Abstract: A self-healing WDM (Wavelength Division Multiplexing)-PON (Passive Optical Network) system is disclosed and includes a CO (Central Office), a RN (Remote Node) and a plurality of subscriber units. The system includes a trunk working fiber and a trunk protection fiber for connecting the CO with the RN, a distribution working fiber, and a distribution protection fiber for connecting the RN with the subscriber units. The CO is connected to the trunk working fiber and the trunk protection fiber, and contains an optical switching unit switched when an error or communication failure occurs, an upstream working optical receiver and an upstream protection optical receiver for receiving upstream data, and a downstream working light source and a downstream protection light source for transmitting downstream data.

Abstract: This invention provides a new architecture for a communication system between head-ends and end-users which expands bandwidth and reliability of the communication system. A mux-node receives communication signals from a head-end and forwards the received communication signals to one or more mini-fiber nodes. The connection to the head-end is via a small number of optical fibers and the connections to each of the mini-fiber nodes may be via one or more optical fibers that may provide full duplex communication. The head-end may communicate with the mux-node using digital or digital and analog signals. The mini-fiber nodes may combine the signals received from the head-end with loop-back signals used for local media access control prior to forwarding the signals to the end-users. Upstream data are received by the mini-fiber nodes and transmitted to the mux-node.

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 WDM optical source, in adopting a spectrum-sliced method, advantageously needs neither an optical source with specific generation wavelength nor a wavelength-stabilizing circuit for stabilizing wavelength. Affording high power and a very narrow line width, the WDM optical source can provide a broadcasting service without signal distortion by a chromatic dispersion effect and also avoids the expense of an amplifier and/or external modulator, thereby relieving subscribers of the economical burden. The practical use of WDM-PON and of WDM-PON using an inventive WDM optical source can therefore be brought to fruition and broadcasting service can be provided economically.

Abstract: A multi-wavelength light source includes an amplifier for generating light over a wide wavelength range; and, an optical fiber grating including a plurality of gratings formed on an optical fiber in in parallel with each other, thereby dividing the light inputted from the amplifier into respective channels having different wavelengths to reflect the divided channels to the amplifier. The amplifier amplifies each channel reflected in the gratings.

Abstract: Two signal lights having different wavelengths are bidirectionally transmitted on an optical-fiber transmission-line. A Raman pump light source generates a first Raman pump light having predetermined wavelengths with a Raman gain-bandwidth for amplifying the first signal light and without response to the second signal light. Another Raman pump light source generates a second Raman pump light having predetermined wavelengths with a Raman gain-bandwidth for amplifying the second signal light and without response to the first signal light. The first Raman pump light and the second Raman pump light are differently injected from respective input/output terminals into the optical-fiber transmission-line by optical combining and branching filters.

Abstract: An optical fiber network can include an outdoor laser transceiver node that can be positioned in close proximity to the subscribers of an optical fiber network. The outdoor laser transceiver node does not require active cooling and heating devices that control the temperature surrounding the laser transceiver node. The laser transceiver node can adjust a subscriber's bandwidth on a subscription basis or on an as-needed basis. The laser transceiver node can also offer data bandwidth to the subscriber in preassigned increments. Additionally, the laser transceiver node lends itself to efficient upgrading that can be performed entirely on the network side. The laser transceiver node can also provide high speed symmetrical data transmission. Further, the laser transceiver node can utilize off-the-shelf hardware to generate optical signals such as Fabry-Perot (F-P) laser transmitters, distributed feed back lasers (DFB), or vertical cavity surface emitting lasers (VCSELs).

Abstract: In one embodiment, a router includes a star switching fabric operable to receive a plurality of optical signals each having a wavelength and each associated with a payload received by the router and to communicate from the switching fabric a plurality of substantially similar sets of the optical signals. The router further includes a plurality of tunable filters each having a configuration speed and each associated with a communication path coupled to one of a plurality of destination elements. Each filter is operable to receive one of the sets of optical signals from the switching fabric and to selectively tune to a wavelength of one of the plurality of optical signals received to facilitate communication of at least the payload associated with that optical signal toward the destination element associated with that filter. The router also includes a plurality of line cards operable to facilitate generation of at least some of the optical signals for transmission to the star switching fabric.

Abstract: A TDM PON including: an optical line terminal; a remote node including multiple secondary optical distributors connected to multiple optical network units; and the multiple optical network units generating and outputting a corresponding upstream optical signal. Each of the secondary optical distributors splits an upstream optical signal input from one of the optical network units connected thereto so as to generate split upstream optical signals and transmits one of the upstream optical signals to the optical line terminal, and transmits another upstream optical signal to a different optical network unit.

Abstract: Provided is a hybrid Passive Optical Network (PON) using a wireless communication.

Abstract: An optical communication system is provided which includes an optical signal transmitter which communicates high bandwidth, high power frequencies. The optical signal transmitter includes a high efficiency/high power optical source such as an optical magnetron or a phased array source of electromagnetic radiation, and a modulator element. The modulator element may be within a resonance cavity of the high efficiency/high power optical source (intra cavity) or external to the cavity (extra cavity). The modulator element serves to modulate output radiation of the high efficiency/high power optical source to produce a modulated high frequency optical signal which may be transmitted through the air. The optical signal transmitter is particularly useful in providing the last mile connection between cable service operators and end users.

Abstract: A passive optical network includes: a central office for generating multiplexed downstream optical signals and receiving an upstream optical signal; a plurality of optical network units for receiving a corresponding downstream optical signal and generating subcarrier channels carrying electrical data of an assigned frequency; and a remote node for photoelectrically converting the channels into electrical data, electro-optically converting the electrical data into at least one upstream optical signal.

Abstract: In accordance with the teachings of the present invention, a system and method for extending reach in a passive optical network (PON) is provided. In a particular embodiment, a method for extending reach in a PON includes transmitting traffic at a first wavelength from a transmitter at a first optical network unit (ONU) in a PON and transmitting traffic at a second wavelength from a transmitter at a second ONU in the PON. The method also includes receiving the traffic in the first wavelength at a first input port of a multiplexer at a distribution node in the PON and receiving the traffic in the second wavelength at a second input port of the multiplexer at the distribution node. The method further includes forwarding the traffic in the first wavelength and the traffic in the second wavelength to an optical line terminal (OLT) in the PON.

Abstract: Disclosed is a wavelength division multiplexing passive optical network (WDM PON) system in which an optical signal outputted from a central office is injected into a Fabry-Perot laser diode (F-P LD) as the light source of an optical network unit, so that the output wavelength of the optical network unit is injection-locked at the same wavelength as that of the optical signal outputted from the central office, thereby enabling the optical network unit to output an optical signal having the same wavelength as that of the optical signal outputted from the central office. In accordance with this system, it is possible to transmit and receive forward and backward data at the same wavelength by the unit of channels. Since inexpensive F-P LDs are used as respective light sources of the central office and optical network units, it is possible to efficiently and economically implement a WDM PON system.

Abstract: A single fiber passive optical network (PON) wavelength division multiplex (WDM) overlay includes a central office, a fiber optic network, and a plurality of optical network termination (ONT) units. The central office has a baseline optical link that receives a baseline communication signal and converts the baseline communication signal into a downstream baseline optical signal within a first optical bandwidth, and has an additional optical link that receives a second type of communication signal and converts the second type of communication signal into a second downstream optical signal within a second optical bandwidth. The downstream baseline optical signal generated by the baseline optical link is combined with the second optical signal generated by the additional optical link to generate a broadband optical signal. The fiber optic network is coupled to the central office and receives the broadband optical signal on at least one optic fiber.

Abstract: A passive optical network includes a central office and a subscriber-side apparatus connected with the central office through an optical fiber link. The subscriber-side apparatus performs communication with the central office based on wavelength-division-multiplexed optical signals. The central office has a routing section, provided with first to fourth multiplexing ports, for demultiplexing multi-wavelength light inputted from the fourth multiplexing port into a plurality of channels. Each of the demultiplexed channels is amplified and multiplexed for output through the first multiplexing port. Optical signals inputted through the third multiplexing port are demultiplexed and outputted upstream. The routing section also multiplexes channels for downstream optical signals, outputting the multiplexed channels through the second port. A splitting section, provided with first to third splitting ports and arranged on a loop optical waveguide connects the first and fourth multiplexing port with each other.

Abstract: Disclosed is a hybrid PON including: a central office, remote terminal and a plurality of optical network units arranged in groups, the central office for outputting downstream optical signals, the remote node for wavelength-division-demultiplexing the downstream optical signals input from the central office, splitting the demultiplexed downstream optical signals, respectively, to generate multiple downstream optical signals, outputting the multiple downstream optical signals to optical network units of a corresponding group, generating corresponding upstream optical signals modulated into upstream subcarriers of a corresponding group input from the optical network units of the group, and outputting the generated upstream optical signals to the central office, and the optical network units for obtaining downstream subcarriers of a corresponding group from corresponding downstream optical signals input from the remote node, obtaining corresponding downstream subcarriers by filtering the downstream subcarriers

Abstract: The invention relates to the distribution of a synchronization signal in an optical communication system which is inherently asynchronous. In order to accomplish a cost-efficient mechanism for transmitting a synchronization signal in such a system, the amplitude of a payload signal is modulated with the synchronization signal, whereby an amplitude-modulated payload signal is obtained. This amplitude-modulated payload signal is transmitted as an optical signal to the opposite end of an optical link, where the synchronization signal is separated from the payload signal.

Abstract: In accordance with the teachings of the present invention, a system and method for managing network components in a passive optical network (PON) is provided. In a particular embodiment, the method includes transmitting, at a first wavelength, a first configuration message on the PON, wherein the first configuration message comprises a first transmitter interface number. The method also includes transmitting, at a second wavelength and at approximately the same time as the first message, a second configuration message on the PON, wherein the second configuration message comprises a second transmitter interface number. The method further includes receiving a configuration response message from each of one or more optical network units (ONUs) in a first set of ONUs that comprises the first transmitter interface number and receiving a configuration response message from each of one or more ONUs in a second set of ONUs that comprises the second transmitter interface number.

Abstract: A method and system for providing tandem protection in a communication system. Path protection is provided using at least two redundant communication paths and selecting the communication having higher signal quality. Interface protection is provided through a protection transceiver thus implementing M:N equipment protection and 1+1 optical protection.

Abstract: Processing a received optical signal in an optical communication network includes equalizing a received optical signal to provide an equalized signal, demodulating the equalized signal according to an m-ary modulation format to provide a demodulated signal, decoding the demodulated signal according to an inner code to provide an inner-decoded signal, and decoding the inner-decoded signal according to an outer code. Other aspects include other features such as equalizing an optical channel including storing channel characteristics for the optical channel associated with a client, loading the stored channel characteristics during a waiting period between bursts on the channel, and equalizing a received burst from the client using the loaded channel characteristics.

Abstract: In a hybrid fiber coax (HFC) cable system, data is communicated upstream from user terminals to a headend of the system to realize various interactive services. The user terminals generate analog modulated signals representing the user data, which populate different channels in a reverse passband of the system. In accordance with the invention, the analog modulated signals are transformed to the corresponding digital baseband signals containing the data. The resulting digital baseband signals are optically transmitted to the headend, thereby efficiently utilizing the limited capacity of the fiber optical portion of the HFC cable system.

Abstract: The present invention is generally drawn to optical network architecture that can include a multi-subscriber optical interface that can service a plurality of subscribers that are located in close proximity relative to one another. For example, the multi-subscriber optical interface can service multiple dwelling units such as an apartment complex that has many different subscribers to the optical network system. Further, the invention can also service subscribers over the same optical waveguide who may have different bandwidth needs, such as businesses, personal/home users and the like.

Abstract: A repeating apparatus and method using wireless optical transmission is disclosed. The repeating apparatus includes a donor device for transmitting two identical copies of an optical signal by receiving a RF signal from a base station and electro-optic converting the RF signal to an optical signal, and for transmitting a RF signal by receiving two identical copies of the optical signal and optic-electro converting the optical signal to a RF signal; and a coverage device for transmitting a RF signal to a mobile communication terminal by receiving two identical copies of the optical signal from the donor device and optic-electro converting the two identical copies of the optical signal to the RF signal, and transmitting two optical signals to the donor device by receiving the RF signal from the mobile communication terminal and elector-optic converting the RF signal to the optical signal.

Abstract: A light source apparatus for use with optical communication using external-injection light sources, and an optical communication system using the light source apparatus. The light source apparatus for optical communication includes external-injection light sources, and a multiplexer/demultiplexer. The multiplexer/demultiplexer provides light components spectrum-sliced broadband light from a broadband light source as respective external injection light inputs. The multiplexer/demultiplexer includes a first waveguide to transmit the broadband light and multiplexed light with a plurality of wavelengths, a plurality of second waveguides each to transmit light with an associated one of the wavelengths, and a plurality of optical filters each to pass light with an associated one of the wavelengths and to reflect the remaining wavelengths.

Abstract: The invention concerns a method of connecting a subscriber unit (12) to a fiberoptic communication network (14) via a fiberoptic interface device (30) adapted to function as an interface device (30) in a coarse wavelength division multiplex (CWDM) system. The interface device (30) comprises an electric circuit arrangement (32) and a first (34) and a second (36) receiving section adapted to receive transceiver modules (24, 70). According to the method, an opto-electric transceiver module (24) is arranged in said first receiving section (34) and connected to said fiberoptic communication network (14). A first electric transceiver module (70) is provided and arranged in said second receiving section (36). The interface device (30) is connected, via said electric transceiver module (70), to said subscriber unit (12) via electrical conduction paths (82, 86). The invention also concerns a method of testing the function of said interface device (30).

Abstract: In an optical wavelength division multiplexed access system, a center unit (OSU) and n optical network units (ONUs) are connected together via a wavelength splitter and optical fiber transmission lines, and downstream optical signals from the OSU to the ONUs and upstream optical signals from the ONUs to the OSU are transmitted in both directions, the wavelength spacing ??d (optical frequency spacing ?fd) of the downstream optical signals is set to twice or more the wavelength spacing ??u (optical frequency spacing ?fu) of the upstream optical signals, each ONU transmits an upstream optical signal whose optical spectral width is twice or more ??u (?fu), and the wavelength splitter spectrum slices the upstream signals transmitted from the ONUs into wavelengths (optical frequencies) whose optical spectral widths are mutually different within ??u (?fu), and wavelength-division multiplexes them and transmits to the OSU.