JP2009088757A - Synchronizing method in network for code division multiplex communication constituted with an office apparatus and a plurality of subscribere terminals and the same network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent irregular communication that is caused by allowing a signal for adjustment of synchronization of a new ONU to superimpose on the signal for data communication of the existing ONU in the asynchronous condition. <P>SOLUTION: The synchronizing method is provided with: a synchronization adjusting process for adjusting synchronization between the office apparatus and the plurality of subscriber terminals by changing each transmission phase of the subscriber terminals in the synchronization adjusting section 10; and a user data transmitting/receiving process for transmitting and receiving user data between the office apparatus and the plurality of subscribers in the user data section 20. Here, the synchronization adjusting section and the user data section are sequentially and repeatedly provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a synchronization method and a network in a network performing code division multiplex communication composed of one station side device and a plurality of subscriber devices.

  An optical communication network that multiplexes 32 channel 10/100 BASE-TX signals by code division multiplexing (CDM) will be described with reference to FIG.

  The optical communication network 1100 is a passive optical subscriber network (PON), that is, a WDM-CDM-PON system, which combines wavelength division multiplexing (WDM) technology and code division multiplexing (CDM) technology. A station side device (OLT) 1200 is arranged at the central office 1110 close to the backbone network, and a user terminal device (ONU) 1300 is arranged at the subscriber side. A wavelength filter 1120 is provided on the ONU 1300 side, and the central office 1110 and the wavelength filter 1120 are connected by a single optical fiber 1130. The WDM-CDM signal sent from the central office 1110 to the ONU 1300 is branched for each wavelength by the wavelength filter 1120 and sent to the optical coupler 1400.

  A plurality of ONUs 1300 are connected to the optical coupler 1400. One ONU group connected to the one optical coupler 1400 and one OLT 1200 constitute one group.

  Communication within this one group uses the same wavelength for upstream communication from the ONU 1300 to the OLT 1200 and downstream communication from the OLT 1200 to the ONU 1300 using the CDM technology. On the other hand, different wavelengths are assigned to each group, and wavelength separation or wavelength multiplexing is performed by the wavelength filter 1120 and the intra-office filter 1122 provided in the central office 1110.

  The OLT 1200 includes an interface 1210, and performs transmission / reception of packets with the backbone network, generation of frames, extraction of packets, and the like. Thirty-two types of codes are assigned to the encoders 1232-1 to 322, respectively. The encoders 1232-1 to 3232 convert the upstream frame to generate a code spread signal. The code spread signals are added by the addition multiplexer 1240 to generate a code division multiplexed (CDM) signal. This CDM signal is converted into a CDM optical signal by the optical module 1250 and transmitted to the ONU 1300. The CDM optical signal generated by each OLT 1200 is wavelength-multiplexed by the intra-office filter 1122 and sent to the ONU 1300 as a WDM-CDM signal.

  The WDM-CDM signal is wavelength-separated by the wavelength filter 1120, and each separated CDM optical signal is sent to the optical coupler 1400. The CDM optical signal is branched into 32 by the optical coupler 1400 and then sent to each ONU 1300.

  In each ONU 1300, a CDM optical signal is converted into a CDM electrical signal by the optical module 1350 and then sent to a decoder 1382 including a CCD matched filter 1384 and a comparator 1386.

  The CCD matched filter 1384 performs a convolution operation on the code assigned to the decoder 1382 with respect to the CDM electric signal. The comparator 1386 reproduces the downstream frame from the result of the convolution operation by the CCD matched filter 1384. Thereafter, the packet extracted from the frame via the interface 1310 is sent to the user terminal.

  On the other hand, a signal from the user terminal is received by the interface 1310 of the ONU 1300, encoded by the encoder 1332, and then converted into an optical signal by the optical module 1350. This optical signal is multiplexed by the optical coupler 1400 to become a CDM optical signal, and further wavelength-multiplexed by the wavelength filter 1120 and sent to the central office 1110 as a WDM-CDM signal. The WDM-CDM signal is wavelength-separated into a CDM optical signal by the intra-office filter 1122, and then sent to the OLT 1200.

In the OLT 1200, the optical module 1250 converts the CDM optical signal into a CDM electrical signal, the electrical signal is distributed by the distributor 1270, and is sent to the decoders 1282-1 to 322. Each of the decoders 1282-1 to 32 is composed of a CCD matched filter and a comparator, similarly to the decoder 1382 included in the ONU 1300, and reproduces an upstream frame from the electrical signal. The upstream packet is transmitted to the backbone network via the interface 1210.
G. C. Gupta et al. , “Hybrid WDM-CDM-PON for Ultra Long Reach Access Network”, European Conference on Optical Communication EcoC We3, 147, September 2006.

  In the optical network having the above-described configuration, the CDM signals in the downstream direction are collectively generated by the OLT 1200, so that the phases of the transmission clock and the modulation clock are aligned. Here, the transmission clock defines a chip cycle Tchip when code spreading is performed with a code of k chips. The modulation clock defines a data period Tdata (= Tchip × k).

  However, in the case of upstream communication, due to the difference in distance from the optical coupler 1400 of each ONU 1300, the optical coupler is in a state where the transmission clock and the modulation clock between the channels are not synchronized, that is, the phases are not aligned. As a result, the uplink frame may not be reproduced on the OLT side. Therefore, it is necessary to align the phases of the upstream transmission clocks.

  Transmission clock synchronization is normally performed by a phase shift according to an instruction from the OLT to each ONU, but each ONU cannot recognize a difference in distance from the coupler.

  For this reason, when an ONU is added or the like, the signal for synchronization adjustment of the new ONU overlaps in a state where it is not synchronized with the data communication signal of the existing ONU, and normal communication may not be performed.

  Therefore, when the inventors of the present application have conducted intensive research, a synchronization adjustment interval and a user data interval are provided in a signal to be transmitted, and a frame for data communication is arranged only in the user data interval. For subscriber devices that are only in the section and are not synchronized, by stopping transmission in the user data section, it is possible to adjust the synchronization of the new ONU without interfering with data communication in the existing ONU I found out that

  The present invention has been made in view of the above-described problems, and an object of the present invention is an existing network that performs code division multiplex communication including one station-side device and a plurality of subscriber devices. The present invention provides a synchronization method and a network capable of adjusting the synchronization of a new ONU without interfering with data communication between the ONU and the OLT.

  In order to achieve the above-described object, according to the first aspect of the present invention, there is provided a synchronization method in a network performing code division multiplex communication, which is composed of one station side device and a plurality of subscriber devices. The

  This synchronization method includes a synchronization adjustment process for performing synchronization adjustment between a station-side device and a plurality of subscriber devices by changing a transmission phase of each of the plurality of subscriber devices in a synchronization adjustment section, and user data The section includes a user data transmission / reception process of transmitting / receiving user data between the station-side apparatus and a plurality of subscriber apparatuses synchronized with the station-side apparatus. Here, the synchronization adjustment section and the user data section are sequentially and repeatedly provided.

  In performing the synchronization method described above, in the synchronization adjustment process, the synchronization adjustment is performed for one subscriber apparatus among a plurality of subscriber apparatuses, and the synchronization adjustment is performed for each repetition of the synchronization adjustment section and the user data section. It is better to switch subscriber devices.

  Further, according to a preferred embodiment of the synchronization method of the present invention, a new subscriber device newly connected to the network is put into a non-operational state, and the synchronization adjustment process further includes a synchronization adjustment start instruction process and a standby state transition. It is preferable to include a process, a transmission phase synchronization process, a transmission availability notification process, and a state transition process.

  In the synchronization adjustment start instruction process, the station side device instructs the new subscriber device, which is a subscriber device to be synchronized, to start synchronization adjustment. In the standby state transition process, the new subscriber device transmits an uplink signal including a standby notification to the station side device in response to the synchronization adjustment start instruction and shifts from the non-operation state to the standby state.

  In the transmission phase synchronization process, the station side device recognizes that the new subscriber device is in a standby state in response to reception of an upstream signal including a standby notification, and changes the transmission phase with respect to the new subscriber device. Send the synchronization adjustment instruction to be made. On the other hand, the new subscriber apparatus changes the transmission phase in response to the synchronization adjustment instruction, and then transmits an uplink signal including a standby notification to synchronize the station side apparatus and the new subscriber apparatus.

  In the transmission permission / inhibition notification process, the station side device transmits a signal indicating transmission permission to the new subscriber device as a transmission permission notification when the station side device and the new subscriber device are synchronized. In the state transition process, the new subscriber device transitions to the operation state in response to receiving the transmission permission / inhibition notification indicating that transmission is possible.

  According to a preferred embodiment of the synchronization method of the present invention, the new subscriber device holds its own channel number.

  In the synchronization adjustment start instruction process, the new subscriber device determines whether or not the channel number of the subscriber device included in the synchronization adjustment start instruction is equal to its own channel number. Transition to the non-operational state and end the synchronization adjustment process.

  According to another preferred embodiment of the synchronization method of the present invention, the station side device provides a subscriber channel number and a subscriber indicating an operating state, a non-operating state or a standby state to each subscriber device. The status information is held, and the new subscriber device holds its own channel number and its own status information indicating the operating status, non-operating status or standby status.

  In the synchronization adjustment start instruction process, the new subscriber device determines whether or not the channel number of the subscriber device included in the synchronization adjustment start instruction is equal to its own channel number. The synchronization adjustment process is terminated as a non-operational state.

  On the other hand, when the subscriber channel number is equal to the self channel number, the subscriber state information and the self state information included in the synchronization adjustment start instruction are further determined. As a result, when the subscriber information indicates the operating state and the self-state information indicates the non-operating state, the terminal adjustment is displayed and then the synchronization adjustment process is terminated.

  Further, in performing the synchronization method described above, in the synchronization adjustment process, one subscriber apparatus transmits to the station side device during a certain period from the start of the synchronization adjustment period to the fixed period and the end of the synchronization adjustment period. Good to stop.

  Further, according to the second aspect of the present invention, code division multiplexing communication is performed between a station-side device and a subscriber device, in which one station-side device is configured to be connected to a plurality of subscriber devices. A network is provided.

  The station-side device includes a station-side information insertion unit, a station-side information extraction unit, and a station-side control unit.

  The station-side information insertion unit sets a synchronization adjustment section and a user data section, and in the synchronization adjustment section, subscriber channel number, subscriber state information indicating an operation state, a non-operation state, or a standby state, a transmission delay amount, and transmission availability Station side subscriber information including any one or more information is inserted, and a frame is arranged in the user data section to generate a downlink transmission signal.

  The station-side information extraction unit extracts subscriber-side subscriber information included in the synchronization adjustment section and a frame included in the user data section from the received signal demodulated in the station-side apparatus.

  The station-side control unit stores the subscriber information for all the subscriber devices included in the network in a freely readable and rewritable manner, and based on the subscriber-side subscriber information extracted by the station-side information extracting unit. The subscriber information is updated or the subscriber information is read out and sent as station side subscriber information to the station side information insertion unit.

  Each of the plurality of subscriber devices includes a subscriber side information insertion unit, a subscriber side information extraction unit, and a subscriber side control unit.

  The subscriber-side information insertion unit sets a synchronization adjustment section and a user data section, and inserts subscriber-side subscriber information including subscriber state information indicating an operation state, a non-operation state, or a standby state in the synchronization adjustment section. And an uplink transmission signal is generated by arranging frames in the user data section.

  The subscriber-side information extraction unit extracts station-side subscriber information included in the synchronization adjustment section and a frame included in the user data section from the downlink reception signal demodulated in the subscriber apparatus.

  The subscriber-side control unit compares the channel number and the subscriber channel number with each other based on the station-side subscriber information, determines the self-state information and the subscriber state information, and based on the comparison and determination results. The self state is switched to the operation state, the non-operation state, or the standby state.

  According to the synchronization method and network of the present invention, a synchronization adjustment interval and a user data interval are provided in a signal to be transmitted, synchronization adjustment is performed in the synchronization adjustment interval, and a frame for data communication is arranged only in the user data interval. In the user data section, only the subscriber apparatus that is synchronized with the station-side apparatus performs transmission. That is, for the subscriber apparatus that is not synchronized with the station-side apparatus, transmission in the user data section is stopped. Thus, it is possible to adjust the synchronization of the new subscriber device without interfering with the communication between the existing subscriber device and the station side device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments are merely schematically shown to the extent that the present invention can be understood. Moreover, numerical conditions etc. are only suitable examples. Therefore, the present invention is not limited to the following embodiments, and many changes or modifications that can achieve the effects of the present invention can be made without departing from the scope of the configuration of the present invention.

(Network configuration)
With reference to FIG. 1, a configuration of a network in which a synchronization method according to an embodiment of the present invention is implemented will be described. FIG. 1 is a schematic diagram illustrating an optical communication network as a configuration example of a network. The optical communication network 100 of this configuration example includes one station side device (OLT: Optical Line Terminal) 200 and a plurality of subscriber devices from the first to the nth (n is an integer of 2 or more). User terminal devices (ONU: Optical Network Units) 300-1 to 300-n.

  The OLT 200 is connected to the first to nth ONUs 300-1 to 300-n via the optical fiber 410 branched by the optical coupler 400. The OLT 200 is connected to a backbone network (not shown) such as the Internet. Each ONU 300 is connected to a communication terminal (not shown) such as a personal computer.

  Between the OLT 200 and each of the ONUs 300-1 to n, communication in the downstream direction from the OLT 200 to the ONUs 300-1 to n and communication in the upstream direction from the ONUs 300-1 to n to the OLT 200 are performed. As a result, transmission / reception of packets is performed between the backbone network and each communication terminal. Here, an example will be described in which a 100BASE-TX packet is transmitted and received as, for example, a Fast Ethernet (registered trademark) standard packet.

  First, an outline of downlink communication will be described.

  From the backbone network, the OLT 200 corresponds to the first to n ONUs 300-1 to n, and the 100BASE-TX downlink packets of channels (CH) 1 to CHn (indicated by arrows 500-1 to n in the figure). Receive.

  The OLT 200 generates a CDM signal from the received downlink packets 500-1 to CHn of the CH1 to CHn using a code division multiplexing (CDM) technique, and then converts the CDM signal, which is an electric signal, to the downlink multilevel light. It is converted into a signal (indicated by an arrow 530 in the figure).

  The downstream multilevel optical signal 530 generated by the OLT 200 is branched into first to n-th branch multilevel optical signals (indicated by arrows 532-1 to n in the figure) by the optical coupler 400, and each ONU 300-1 is split. Sent to ~ n.

  Each ONU 300-1 to n demodulates the received branched multilevel optical signals 532-1 to 532-1 and extracts a downlink packet addressed to itself. The extracted downstream packets (indicated by arrows 550-1 to n in the figure) are sent from the respective ONUs 300-1 to 300-n to the communication terminals.

  Next, an outline of uplink communication will be described.

  Each of the ONUs 300-1 to 300-n receives CH1 to CHn uplink packets (indicated by arrows 552-1 to 55n in the figure) from the communication terminals. Each ONU 300-1 to n modulates the received upstream packets 552-1 to 552-1 to code spread signals, and then converts them into upstream optical signals (indicated by arrows 570-1 to 570n in the figure).

  Upstream optical signals 570-1 to 570-n generated by the respective ONUs 300-1 to n are combined by the optical coupler 400 to generate an upstream multilevel optical signal (indicated by an arrow 572 in the figure). This upstream multilevel optical signal 572 is sent to the OLT 200.

  The OLT 200 extracts upstream packets (indicated by arrows 590-1 to n in the figure) included in the first to n ONUs 300-1 to n from the upstream multilevel optical signal 572, and transmits them to the backbone network. .

  In this case, the CH1 downlink packet 500-1 input from the backbone network to the OLT 200 and the CH1 downlink packet 550-1 sent from the first ONU 300-1 to the communication terminal have the same contents. Also, the CH1 upstream packet 552-1 input from the communication terminal to the first ONU 300-1 and the CH1 upstream packet 590-1 sent from the OLT 200 to the backbone network have the same contents. The same applies to the downlink packets and uplink packets of other CH2 to CHn.

  In order for the optical coupler 400 to generate the upstream multilevel optical signal 572 as a CDM optical signal, the upstream optical signals 570-1 to 570-n are synchronized with each other, that is, their positions on the time axis are aligned. Need to be.

  The synchronization of each upstream optical signal is performed, for example, by sending a phase shift instruction from the OLT 200 to each of the ONUs 300-1 to n, and performing a phase shift on the received ONUs 300-1 to n. At this time, normally, each ONU 300-1 to n cannot recognize the difference in distance from the optical coupler 400 to each ONU 300-1 to n. Therefore, when an upstream signal from a new ONU and an upstream signal from an existing ONU overlap in an unsynchronized state, such as when adding ONUs, normal communication may not be possible between the OLT and the existing ONU. Therefore, in order to prevent normal communication from being disabled, the signal is configured as described below.

  With reference to FIG. 2, the structure of the signal transmitted / received between OLT200 and each ONU300 is demonstrated. FIG. 2 is a schematic diagram showing a configuration of signals transmitted and received in the optical communication network.

  The signal transmitted and received in the optical communication network 100 repeatedly has the synchronization adjustment section 10 and the user data section 20 on the time axis. Here, the user data section 20 is a section in which a frame including a packet transmitted / received between the backbone network and the terminal device is transmitted / received. The synchronization adjustment section 10 is a section for transmitting and receiving signals for synchronizing the OLT 200 and the ONUs 300-1 to n.

  Here, the ONUs (target ONUs) to be subjected to synchronization adjustment in the synchronization adjustment section 10 are all ONUs constituting the network, and one ONU is assigned to each section. The target ONU is sequentially switched every time the synchronization adjustment section 10 and the user data section 20 are repeated. That is, each ONU is subject to synchronization adjustment at regular intervals, and receives a synchronization adjustment start instruction addressed to itself.

  Regarding user data transmission / reception including packets, a user data interval and a synchronization adjustment interval are provided in the transmission signal, and user data is not transmitted / received in the synchronization adjustment interval, but is transmitted / received only in the user data interval. For example, since it is conventionally known, the description is omitted here.

  The station side device (OLT) will be described with reference to FIG. FIG. 3 is a schematic diagram illustrating a configuration example of the OLT.

  The OLT 200 includes an interface unit 210, a framer 220, a station side information insertion unit 225, a modulation unit 230, an addition multiplexer 240, an optical module 250, a distributor 270, a demodulation unit 280, a station side information extraction unit 285, a clock control unit 260, and A station-side control unit 290 is provided.

  The interface unit 210 transmits and receives packets to and from the outside, here, the backbone network. Specifically, interface section 210 receives CH1 to CHn downlink packets 500-1 to 500-n from the backbone network and sends them to framer 220. Further, the interface unit 210 receives the uplink packets 590-1 to 590-n of CH 1 to CHn from the framer 220 and transmits them to the backbone network. As the interface unit 210, any conventionally known and suitable PHY (physical layer) device can be used.

  The framer 220 adds a header to the downlink packets 500-1 to n received from the interface unit 210, and converts the packets into downlink frames (indicated by arrows 504-1 to n in the figure) suitable for CDM. In the 100BASE-TX standard, the data rate is defined as 100 Mbps (bit per second). In the framer 220, the downlink frames 504-1 to n generated by converting the downlink packets 500-1 to n have a data rate of 125 Mbps. Here, the header added by the framer 220 includes management data such as error detection data. Downlink frames 504-1 to 504-1 generated by framer 220 are sent to station-side information insertion unit 225.

  Further, the framer 220 receives from the station-side information extraction unit 285 the uplink frames (indicated by arrows 586-1 to n in the figure) transmitted from each ONU and reproduced in the OLT 200. The framer 220 removes the headers from the upstream frames 586-1 to 586-n, and extracts the upstream packets 590-1 to 590-n of CH1 to CHn, respectively. In this case, framer 220 extracts 100 Mbps upstream packets 590-1 to 590-n from the upstream frame having a data rate of 125 Mbps.

  Here, the framer 220 generates a header to be added to the downlink frame based on an instruction from the station-side control unit 290, and sends header information included in the uplink frame to the station-side control unit 290.

  As the framer 220, any suitable and well-known MAC (Media Access Control) device can be used.

  The station-side information insertion unit 225 adds station-side subscriber information received from the station-side control unit 290 to the downlink frames 504-1 to n received from the framer 220, and transmits a downlink transmission signal (indicated by an arrow 506 in the figure). -1 to n)). The downlink transmission signal repeatedly has a synchronization adjustment interval and a user data interval on the time axis. The downstream frame is arranged in the user data section. The station side subscriber information is inserted into the synchronization adjustment section. The subscriber information will be described later.

  The modulator 230 includes first to n encoders 232-1 to 23-n corresponding to CH1 to CHn.

  The first to nth encoders 232-1 to 232-1 to code spread the downlink transmission signals 506-1 to 506-1 generated by the station-side information insertion unit 225 using a code set in advance for each channel. , Code spread signals (indicated by arrows 508-1 to n in the figure) are generated. Here, one bit of the downstream frame is spread to 16 chips. When a downstream frame having a data rate of 125 Mbps is spread to 16 chips, a code spread signal having a chip rate of 2 G (= 125 M × 16) cps (chip per second) is obtained. For example, when the data indicated by 1 bit is “1”, the code spread signal is “10100... 01”, while when the data is “0”, the code spread signal is “01011.

  The addition multiplexer 240 multiplexes the n-channel code spread signals 508-1 to 508-n generated by the encoders 232-1 to 23-n of the modulation unit 230. At this time, code spread signals 508-1 to 508-n which are binary signals of “0” and “1” are multiplexed for each chip to obtain a downlink multilevel electric signal (indicated by an arrow 512 in the figure). . Here, since the n-channel code spread signals 508-1 to 508 -n are multiplexed, the downlink multilevel electric signal 512 takes n + 1 values from 0 to n.

  Each of the encoders 232-1 to 23-n, that is, the modulation unit 230 and the addition multiplexer 240 can have the same configuration as that normally used in a communication system using the CDM technique.

  The optical module 250 is a part that transmits / receives a code spread signal to / from each ONU, and is also referred to as a station side code spread signal transmitter / receiver.

  Here, the optical module 250 performs electrical-optical (E / O) conversion and optical-electrical (O / E) conversion, and conventionally known, for example, a laser diode (LD) 252 and a photodiode (PD) 254. It is configured with. In the optical module 250, the LD 252 performs E / O conversion, and the PD 254 performs O / E conversion.

  In the optical module 250, the LD 252 converts the downlink multilevel electrical signal 512 into the downlink multilevel optical signal 530, and then transmits it to each ONU 300. Further, the PD 254 converts the upstream multilevel optical signal 572 into an upstream multilevel electrical signal (indicated by an arrow 576 in the figure), and then sends it to the distributor 270. In addition, a part of the uplink multilevel electric signal 576 is sent to the clock control unit 260.

  The distributor 270 distributes the upstream multi-level electric signal 576 according to the number of channels. Here, distributor 270 sends first to n-th upstream electrical signals (indicated by arrows 580-1 to n in the drawing) obtained by dividing upstream multilevel electrical signal 576 by n to demodulation section 280.

  The demodulator 280 includes first to nth decoders 282-1 to 282-1. Each decoder 282-1 to n demodulates the first to n upstream electrical signals 580-1 to n.

  Each decoder 282-1 to n may have a conventionally well-known configuration described with reference to FIG. 11, and includes, for example, a charge coupled device (CCD) matched filter 284 and a comparator 286. The

  The CCD matched filter 284 performs a convolution operation on the decoding codes determined for each channel with respect to the upstream electrical signals 580-1 to 580-n. When the encoded code pattern matches the decoding code pattern, the CCD matched filter 284 outputs a strong autocorrelation peak in the positive or negative direction. The direction of the autocorrelation peak corresponds to “1” or “0” of the data. For example, a positive peak is output when the data is “1” and a negative direction when the data is “0”. The peak of is output.

  The comparator 286 determines the output of the CCD matched filter 284 at a period corresponding to the data rate, that is, at a timing of 125 MHz. For example, the comparator 286 outputs “1” when the output of the CCD matched filter 284 is positive, and outputs “0” when the output is negative. This output is latched during the data period Tdata and maintained until the timing of the next modulation clock. As a result, uplink reception signals 584-1 to 584-1 corresponding to each channel are reproduced.

  Uplink received signals 584-1 to 584-1 demodulated by demodulating section 280 are sent to station side information extracting section 285. The station side information extraction unit 285 extracts the upstream frames 586-1 to 586-1 to n arranged in the user data section and sends them to the framer 220, and also extracts subscriber information on the subscriber side arranged in the synchronization adjustment section. To the station control unit 290.

  The subscriber information includes, for example, one or more of a synchronization pattern, a synchronization adjustment section start flag, a subscriber channel number, subscriber status information, a transmission delay amount, and transmission permission / inhibition information.

  The synchronization pattern is a pattern used for determining whether or not the OLT and each ONU are synchronized. The synchronization adjustment section start flag is a flag indicating the start of the synchronization adjustment section. The subscriber channel number is a channel number of an ONU that is a target of synchronization adjustment (hereinafter also referred to as a target ONU). The subscriber status information indicates whether the target ONU is in an operating state, a non-operating state, or a standby state. The transmission delay amount indicates the magnitude of the phase shift with respect to the target ONU.

  In the OLT, the station-side control unit 290 holds subscriber information so that it can be read and rewritten. The station-side control unit 290 sends the read subscriber information to the station-side information insertion unit 225 as station-side subscriber information. The station-side control unit 290 receives the subscriber-side subscriber information extracted by the station-side information extraction unit 285, and updates the stored subscriber information according to the subscriber-side subscriber information.

  The clock control unit 260 includes a 125 MHz oscillator 262, a 2 GHz oscillator 264, a clock extraction circuit 266, and a clock comparison circuit 268.

  The 125 MHz clock generated by the 125 MHz oscillator 262 is sent to the framer 220 and the demodulator 280 as a downstream modulation clock and an upstream demodulation clock, respectively. The 2 GHz clock generated by the 2 GHz oscillator is sent to the modulation unit 230, the addition multiplexer 240, and the optical module 250 as a downlink transmission clock and an uplink reception clock. The clock extraction circuit 266 extracts an upstream transmission clock using the upstream multilevel electrical signal 576 generated by the optical module 250.

  The clock comparison circuit 268 compares the frequency of the upstream reception clock generated by the 2 GHz oscillator 264 with the frequency of the upstream transmission clock extracted by the clock extraction circuit 266. The result of this comparison is sent to the station side control unit 290.

  As the 125 MHz oscillator 262 and the 2 GHz oscillator 264, any suitable conventionally known oscillator can be used. The 125 MHz oscillator 262 may be configured with a conventionally known frequency divider that divides the downstream transmission clock generated by the 2 GHz oscillator 264 by 1/16. The clock comparison circuit 268 only needs to have a function of comparing the frequencies of the two clocks, the upstream reception clock and the upstream transmission clock, and outputting different signals according to the frequency difference. Can be used.

  The clock extraction circuit 266 will be described with reference to FIGS. 4 and 5. FIG. 4 is a schematic diagram for explaining the configuration of the clock extraction circuit. FIG. 5 is a schematic time chart for explaining the clock extraction method. In FIG. 5, the horizontal axis indicates the time axis, and the vertical axis indicates the signal level in arbitrary units.

  The clock extraction circuit 266 has a function of extracting a clock from the multilevel signal, and includes, for example, a signal conversion circuit 2660 and a clock recovery circuit 2666.

  The clock extraction circuit 266 receives an uplink multilevel electric signal as the multilevel serial signal Sn (FIG. 5A).

  The signal conversion circuit 2660 converts the input multilevel serial signal Sn into a binary serial signal Sb. The signal conversion circuit 2660 outputs a high level corresponding to the period from when the signal value of the multilevel signal Sn starts to rise to when it starts to fall, and the signal value of the multilevel serial signal Sn decreases. The low level is output in correspondence with the period from the start to the start of rising. For this purpose, the signal conversion circuit 2660 includes a delay circuit 2662 and a comparator 2664 with hysteresis.

  The delay circuit 2662 generates the delay signal Sd by delaying the multi-level serial signal Sn. The delay time τ of the delay circuit 2662 is set to a value smaller than the frequency of the multilevel serial signal Sn. For example, when transmission data with a transmission rate of 2 GHz is used as a multi-level serial signal, the propagation time per bit of the signal is 500 picoseconds, and therefore the delay time τ is set to less than 500 picoseconds, for example, 100 picoseconds. (FIG. 5B).

  To the comparator 2664 with hysteresis, the multi-value serial signal Sn is input from the + input terminal, and the delay signal Sd is input from the − input terminal. Then, the comparator 2664 with hysteresis outputs a high level when the difference Sn−Sd between the two signal values becomes larger than a predetermined positive value V1 (0 <V1). Once the high level output is started, the comparator 2664 with hysteresis maintains the high level output until the difference Sn−Sd becomes smaller than a predetermined negative value V2 (0> V2). When the difference Sn−Sd becomes smaller than the predetermined negative value V2, the comparator 2664 with hysteresis outputs a low level. Once the low level output is started, the comparator 2664 with hysteresis maintains the low level output until the difference Sn−Sd becomes larger than the positive value V1. Thus, a binary serial signal Sb is generated and output from the signal conversion circuit 2660 (FIG. 5C). That is, the magnitude of hysteresis is determined by the set values of V1 and V2. In this embodiment, V1 and V2 are set such that the time from when the multilevel serial signal Sn starts to rise or fall until Sn-Sd> V1 or Sn-Sd <V2 is shorter than the delay time τ. Is set. Since the internal configuration of the comparator 2664 with hysteresis is well known, a description thereof will be omitted (see, for example, JP-A-9-18297).

  The clock recovery circuit 2666 regenerates the clock CLK from the binary serial signal Sb. The configuration of the clock recovery circuit 2666 may be the same as that of the conventional clock recovery circuit (see, for example, JP-A-2006-261725). That is, as long as the clock CLK is regenerated from the binary serial signal Sb, any configuration can be adopted as the clock recovery circuit 2666 of this embodiment.

  The ONU will be described with reference to FIG. FIG. 6 is a schematic diagram illustrating a configuration example of the ONU.

  The ONU 300 includes an interface unit 310, a framer 320, a subscriber side information insertion unit 325, an encoder 332, an optical module 350, a decoder 382, a subscriber side information extraction unit 385, a clock control unit 360, a subscriber side control unit 390, and variable signals. A delay unit 345 is provided.

  The interface unit 310, the framer 320, the encoder 332, and the decoder 382 included in the ONU 300 can have the same configuration as the interface unit 210, the framer 220, the encoder 232, and the decoder 282 of the OLT 200 described with reference to FIG. . Therefore, the description is omitted here.

  The clock control unit 360 includes a clock extraction circuit 366, a frequency divider 367, and a clock phase adjuster 369. The clock extraction circuit 366 can have the same configuration as that described with reference to FIG. The clock extraction circuit 366 extracts a downlink transmission clock from the downlink multilevel electric signal (indicated by an arrow 536 in the figure) generated by the optical module 350. This downlink transmission clock is also used as a downlink reception clock.

  The frequency divider 367 divides the downlink reception clock to generate a downlink demodulation clock. As the frequency divider 367, any suitable conventionally known one can be used. The clock phase adjuster 369 only needs to have a function of adjusting the phase of the downlink demodulated clock according to an instruction from the subscriber-side control unit 390, for example, and a conventionally known variable delay device can be used.

  The downlink multilevel electrical signal is reproduced as a downlink reception signal (indicated by an arrow 540 in the figure) by a decoder 382 having a CCD matched filter 384 and a comparator 386. The reproduced downlink reception signal is sent to the subscriber side information extraction unit 385. The subscriber side information extraction unit 385 extracts the downlink frame arranged in the user data section and sends it to the framer 320, and extracts the subscriber information on the station side arranged in the synchronization adjustment section. The data is sent to the control unit 390.

  Based on the station side subscriber information, the subscriber side control unit 390 compares its own channel number and subscriber channel number, and determines its own state information and subscriber state information. The subscriber-side control unit 390 switches its own state to an operating state, a non-operating state, or a standby state based on the comparison and determination results.

  Downlink packet 550 is extracted from downlink frame 540 by framer 320 and sent to the communication terminal via interface unit 310.

  The upstream packet 552 received by the interface unit 310 is converted into an upstream frame (indicated by an arrow 556 in the figure) by the framer 320. The upstream frame 556 is sent to the subscriber side information insertion unit 325.

  The subscriber side information insertion unit 325 has the same configuration and function as the station side information insertion unit 225 of the OLT 200. Similar to the downlink transmission signal, the uplink transmission signal repeatedly has a synchronization adjustment interval and a user data interval on the time axis. The subscriber side information insertion unit 325 generates an uplink transmission signal by arranging an uplink frame in the user data section and inserting subscriber information in the synchronization adjustment section.

  The upstream transmission signal is modulated into a code spread signal 560 by the encoder 332. The code spread signal 560 is sent to the optical module 350 after being delayed by the variable signal delay unit 345 (indicated by an arrow 564 in the figure). The variable signal delay unit 345 delays the delay amount of the code spread signal by a magnitude according to an instruction from the subscriber side control unit 390. Here, an example is shown in which phase adjustment is performed by delaying the uplink transmission signal, but the clock control unit 360 may perform phase adjustment by shifting the phase of the uplink transmission clock and the uplink modulation clock. . In this case, the variable signal delay device can be omitted.

  The optical module 350 converts the code spread delayed signal (indicated by an arrow 564 in the figure) delayed by the variable signal delay unit 345 into an upstream optical signal 570 and sends it to the OLT. The optical module 350 includes an LD 352 and a PD 354 as in the optical module 250 of the OLT 200. Here, the LD 352 performs transmission and stops in response to an instruction from the subscriber-side control unit 390. That is, the ONU 300 can perform only reception in the user data section and can stop transmission to the OLT.

  The ONU 300 includes any suitable display unit 395, and can display the state of the ONU 300.

  The OLT 200 has a station-side information insertion unit 225, a station-side information extraction unit 285, and a station-side control unit 290, and the ONU 300 has a subscriber-side information insertion unit 325, a subscriber-side information extraction unit 385, and a subscriber-side control unit. Each of the 390s has only to have the above-described functions, and can be configured as an integrated circuit having an FPGA (Field Programmable Gate Array) or the like. Further, for example, the station-side control unit 290 and the subscriber-side control unit 390 are configured as a RAM (Random Access Memory) or a ROM (Read Only Memory) as an MPU (Microprocessing Unit) as a memory, and can be read into the memory. A configuration may be adopted in which each functional unit is realized by reading a stored program and executing the program.

(Synchronization method)
A case will be described in which an ONU is newly added to an optical communication network configured by the OLT 200 and a plurality of ONUs (existing ONUs).

  Each existing ONU is synchronized with the OLT, and is in a state where user data is transmitted and received (hereinafter referred to as an operation state). The downlink transmission signal from the OLT to each ONU and the uplink transmission signal from each ONU to the OLT both have a synchronization adjustment section 10 and a user data section 20 on the time axis. Here, the user data section 20 is a section in which user data is transmitted and received between the backbone network and the terminal device. The synchronization adjustment section 10 is a section in which a signal for synchronization is transmitted and received between the OLT and each ONU.

  Note that ONUs (target ONUs) to be subjected to synchronization adjustment in the synchronization adjustment section 10 are all ONUs that constitute the network, and one ONU is assigned to each section. The target ONU is sequentially switched every time the synchronization adjustment section 10 and the user data section 20 are repeated. That is, each ONU is subject to synchronization adjustment at regular intervals, and receives a synchronization adjustment start instruction addressed to itself.

  Note that transmission / reception of user data is well known in the art, except that a user data interval and a synchronization adjustment interval are provided in the transmission signal, and transmission / reception is performed only in the user data interval. The synchronization adjustment will be described in detail below.

  FIG. 7 is a sequence diagram for explaining the synchronization method. FIG. 8 is a diagram showing a processing flow in the new ONU in the synchronization adjustment process.

  First, after connecting the new ONU to the optical fiber 410 constituting the optical communication network, the power is turned on. In this state, the new ONU receives a downstream signal from the OLT 200 when the power is turned on, but does not transmit a packet to the communication terminal and does not transmit an upstream signal to the OLT (hereinafter, non-transmission state). (Referred to as operational state).

  The station-side control unit 290 of the OLT 200 holds information such as a channel number and state regarding each ONU 300 as subscriber information. Here, the existing ONU is in the operating state, and the new ONU is in the non-operating state.

  In the OLT 200, the interface unit 210 sends a downlink packet received from the backbone network to the framer 220. The framer 220 adds a header to each downlink packet and generates a downlink frame. Here, since the downstream frame is generated using the common modulation clock received from the clock control unit 260, the phases of the downstream frames are aligned.

  Based on each downlink frame received from the framer 220, the station side information insertion unit 225 generates a downlink transmission signal that repeatedly has a synchronization adjustment interval and a user data interval on the time axis. The station-side information insertion unit 225 arranges the downlink frame in the user data section, and the station-side information insertion unit 225 inserts the subscriber information received from the station-side control unit 290 into the synchronization adjustment section as station-side subscriber information. To do.

  Each downlink transmission signal is modulated by the modulation unit 230 and then multiplexed by the addition multiplexing unit 240. A code division multiplexing (CDM) signal obtained as a result of multiplexing is converted into a CDM optical signal by an optical module and then sent to each ONU.

  The CDM optical signal is n-branched by an optical coupler and sent to each ONU.

  In the new ONU 300 that has received the CDM optical signal, the optical module 350 converts the downstream multilevel optical signal 532 into the downstream multilevel electrical signal 536. Subsequently, the downlink multilevel electric signal 536 is demodulated. However, when the downlink demodulation clock is not synchronized with the downlink modulation clock, the demodulation cannot be performed normally. Therefore, in the new ONU, the downlink demodulation clock is synchronized with the downlink modulation clock.

  This synchronization is performed as follows, for example.

  First, the clock extraction circuit 366 of the new ONU 300 extracts the downlink transmission clock from the downlink multilevel electric signal. This extracted downlink transmission clock is used as a downlink reception clock in the new ONU 300.

  Subsequently, the frequency divider 367 divides the downlink reception clock to generate a downlink demodulation clock. The generated downlink demodulation clock is sent to the decoder 382.

  Subsequently, the decoder 382 demodulates the downlink reception signal 540 at the timing of the downlink demodulation clock generated by the frequency divider 367. The downlink reception signal obtained as a result of the conversion in the optical module is sent to the subscriber side information extraction unit. The subscriber information extraction unit extracts subscriber information from the synchronization adjustment section. The extracted subscriber information is sent to the subscriber-side control unit.

  The subscriber-side control unit of the new ONU determines that the ONU downlink demodulation clock is not synchronized with the OLT downlink modulation clock when the subscriber information does not include a synchronization pattern. In this case, the downstream demodulation clock is phase-shifted, and the downstream demodulation clock of the new ONU is synchronized with the downstream modulation clock of the OLT. For example, when the downlink demodulation clock is generated by dividing the downlink reception clock, the magnitude of the phase shift may be set in units of the period of the downlink reception clock. By setting in this way, if the maximum number of phase shifts is performed as many as the number of chips, the ONU downlink demodulation clock and the OLT downlink modulation clock are synchronized.

  After the ONU downlink demodulation clock and the OLT downlink modulation clock are synchronized, the new ONU waits to receive a synchronization adjustment start instruction addressed to its own ONU.

  The new ONU receives a downlink signal including a synchronization adjustment start instruction addressed to any one of the ONUs at every synchronization adjustment section (S10). In the new ONU, the subscriber side control unit 390 receives and analyzes the subscriber information extracted from the downlink signal by the subscriber side information extraction unit 325.

  In S20, the subscriber-side control unit 390 determines whether or not the subscriber channel number of the target ONU included in the subscriber information is equal to the self channel number.

  In this process, the subscriber-side control unit 390 reads the self channel number stored in a readable manner in a storage unit provided in the ONU. This storage unit can be configured as a ROM or a RAM when the subscriber-side control unit 390 is configured with an MPU. Further, when the subscriber-side control unit 390 is configured as an integrated circuit such as an FPGA, for example, an electrical resistance value may be associated with a self channel number.

  If the self channel number and the subscriber channel number of the target ONU are different (No), the ONU ends the synchronization adjustment process while remaining in a non-operating state. In other words, the synchronization adjustment in the current synchronization adjustment section is not performed, and the process waits until the next synchronization adjustment section.

  On the other hand, when the self channel number is equal to the subscriber channel number (Yes), next, the state is determined in S30.

  The new ONU is in a non-operational state when the power is turned on. Accordingly, the self-state information indicates a non-operational state. On the other hand, since the OLT has not recognized the connection of the new ONU so far, the subscriber status information indicates the non-operating status.

  Therefore, when both the subscriber status information included in the subscriber information and the self status information indicate a non-operational state (No), the new ONU shifts to a standby state and transmits a synchronization adjustment signal ( S40). In this standby state, the new ONU transmits a synchronization adjustment signal in the synchronization adjustment section, but does not transmit user data or perform transmission / reception between communication terminals connected to the new ONU in the user data section. .

  On the other hand, when the self-status information is non-operational and the subscriber status information is operational (Yes), the own channel number is already used by another ONU, that is, the new ONU overlaps with the existing ONU. It is determined that When a new ONU and an existing ONU overlap, the signal addressed to the own ONU can be demodulated by another ONU, or a data error occurs in communication from a plurality of overlapping ONUs to the OLT Or disable normal communication.

  Therefore, the new ONU displays the fact that it overlaps with the existing ONU via the display means provided by itself, and ends the synchronization adjustment process.

  In response to receiving the synchronization adjustment signal, the OLT updates the held subscriber information and switches the state of the target ONU from the non-operational state to the standby state.

  In some cases, the upstream reception clock and upstream demodulation clock of the OLT are not synchronized with the upstream transmission clock and upstream modulation clock of the target ONU. If the uplink reception clock and the uplink transmission clock are not synchronized, clock extraction cannot be performed normally.

  In this case, the OLT sends, as subscriber information, an instruction to phase shift to the target ONU. The target ONU performs the phase shift according to the magnitude of the phase shift included in the subscriber information, and transmits the synchronization adjustment frame again. This process is repeated until the clock is extracted normally.

  After the uplink transmission clock and the uplink reception clock are synchronized, the OLT checks the synchronization pattern included in the synchronization adjustment interval. If the uplink modulation clock and the uplink demodulation clock are synchronized, the synchronization adjustment section repeatedly includes a synchronization pattern.

  When the synchronization pattern is not included, it is determined that the uplink modulation clock and the uplink demodulation clock are not synchronized. Therefore, the OLT sends, as subscriber information, an instruction to phase shift to the target ONU. The target ONU performs the phase shift according to the magnitude of the phase shift included in the subscriber information, and transmits the synchronization adjustment frame again. This process is repeated until the synchronization pattern is confirmed normally.

  After the synchronization pattern is confirmed normally, that is, after the uplink modulation clock and the uplink demodulation clock are synchronized, the OLT switches the state of the target ONU to the operation state and notifies the target ONU that user data can be transmitted. send.

  The ONU that has received the user data transmission enable notification switches its own state to the operating state. The ONU in the operating state sends user data received in the user data section to the communication terminal, converts the upstream packet received from the communication terminal into a frame, places it in the user data section, and transmits it to the OLT. .

  Here, when synchronization is not established in one synchronization adjustment section and it is not possible to shift to the operation state, the standby state is maintained and synchronization is performed in the next own synchronization adjustment section.

  According to this configuration, the synchronization adjustment section and the user data section are separated. Non-synchronized ONUs such as newly connected ONUs do not transmit in the user data interval until they are synchronized. For this reason, it is possible to add ONUs without interfering with communication of other channels.

  In addition, since the synchronization adjustment section is repeatedly provided, it is possible to periodically detect and re-adjust the clock phase shift due to aging or temperature fluctuation.

  Furthermore, according to this configuration, when the code used for modulation and demodulation is different for the channel number assigned to the new ONU, the new ONU cannot shift to the operating state. At this time, since the new ONU displays the overlap between the ONUs, the operator can determine the overlap on the ONU side. Further, in the OLT, by not receiving the synchronization adjustment signal from the new ONU, it is possible to recognize an abnormality regarding the connected new ONU.

  As a result, the OLT does not need to have a control circuit for terminal authentication or the like, and the normal operation of the terminal can be confirmed with a simple circuit configuration and control.

  Here, even if the synchronization adjustment section and the user data section are separated, the existing ONU user data section and the new ONU synchronization adjustment section overlap depending on the difference in distance from the optical coupler to each ONU. There is a risk that. Therefore, it is preferable to set a guard time in a section that overlaps the synchronization adjustment section and the user data section, and during this period, transmission is not performed from the new ONU to the station side apparatus.

  With reference to FIGS. 9 and 10, the guard time when the user data section of the existing ONU and the synchronization adjustment section of the new ONU overlap will be described. Here, the first ONU 300-1 will be described as an existing ONU, and the second ONU 300-2 will be described as a new ONU.

  In FIG. 9, the distance from the optical coupler 400 to the first ONU 300-1 is X (unit: m), the distance from the optical coupler 400 to the second ONU 300-2 is Y (unit: m), and the second In this case, the ONU 300-2 is closer to the optical coupler than the first ONU 300-1 (X> Y).

  In this case, the downlink multilevel signal 530 is in phase until reaching the optical coupler 400, but the branched multilevel optical signals 532-1 and 532-2 branched by the optical coupler 400 are respectively the first The time to reach the ONU 300-1 and the second ONU 300-2 is different. Further, the upstream optical signals 570-1 and 570-2 after being processed by the first ONU 300-1 and the second ONU 300-2, respectively, have different times to reach the optical coupler 400. The upstream signal 570-2 from the ONU 300-2 reaches the optical coupler 400 earlier than the upstream signal 570-1 from the first ONU 300-1. Therefore, the vicinity of the end of the user data section of the upstream signal 570-1 from the first ONU 300-1 and the vicinity of the head of the synchronization adjustment section of the upstream signal 570-2 from the second ONU 300-2 overlap.

  Therefore, in the second ONU 300-2, it is preferable to provide a guard time 12 for stopping the transmission of the uplink signal for a certain period Tg1 from the start of the synchronization adjustment period. During the section Tg1 of the guard time 12, the transmission of the optical module is stopped, and the transmission from the second ONU 300-2 to the OLT 200 is not performed.

  In FIG. 10, the distance from the optical coupler to the first ONU 300-1 is X (unit: m), the distance from the optical coupler to the second ONU 300-2 is Y (unit: m), and the second ONU 300 -2 shows a case where the optical coupler is farther than the first ONU 300-1 (X <Y).

  In this case, for the upstream signals from the first ONU 300-1 and the second ONU 300-2 to the OLT, the time to reach the optical coupler is different, and the upstream signal from the first ONU 300-1 is It reaches the optical coupler earlier than the upstream signal from the second ONU 300-2. Therefore, the vicinity of the beginning of the user data section of the upstream signal from the first ONU 300-1 overlaps with the vicinity of the end of the synchronization adjustment section of the upstream signal from the second ONU 300-2.

  Therefore, in the second ONU 300-2, it is preferable to provide a guard time 14 for stopping the transmission of the uplink signal for a certain period Tg2 until the end of the synchronization adjustment period. During the interval Tg2 of the guard time 14, the transmission of the optical module is stopped and the transmission from the ONU to the OLT is not performed.

  The length of the guard time may be set to a suitable value according to the setting. In addition, each ONU cannot grasp | ascertain the distance from an optical coupler to each ONU. Therefore, the length of the guard time is determined in advance and stored in the OLT and ONU control units so as to be readable, or is transmitted from the OLT to the ONU with a signal within the synchronization adjustment interval. be able to.

  The length of the guard time is determined by the following policy, for example.

  The transmission time of the optical signal in the optical fiber is 5 nanoseconds per meter. The difference in distance from the optical coupler to each ONU is about 10 kilometers at the maximum. In this case, the difference in transmission time of the optical signal that travels back and forth from the optical coupler to each ONU is 100 microseconds. Also, it takes time (in-device processing time) to perform processing such as demodulation and information extraction from when an optical signal is received in each ONU until transmission to the OLT. Therefore, when the in-device processing time is about 1 microsecond, it is preferable to secure a margin for the transmission time and the in-device processing time and set the guard time to 110 microseconds.

  For example, when the synchronization adjustment interval is 1 millisecond and the user data interval is 99 milliseconds, if the guard time is set to 110 microseconds, the synchronization adjustment in the synchronization adjustment interval of the new ONU is changed to the existing ONU. It is not performed in the user data section.

  As a result, when a new ONU is connected, even if the user data section of the existing ONU and a part of the synchronization adjustment section of the new ONU overlap, synchronization adjustment is performed without disturbing existing communication. be able to.

  Although an example in which a 100BASE-TX standard packet is code-division multiplexed with 16 chips has been described here, the packet standard and the number of chips are not limited to this. Further, the synchronization method of this embodiment can be applied not only to an optical communication network but also to CDM wireless communication.

1 is a schematic diagram of an optical communication network. It is a schematic diagram which shows the structure of data. It is the schematic of a station side apparatus (OLT). It is the schematic of a clock extraction circuit. It is a time chart for demonstrating a clock extraction method. It is the schematic of a user terminal device (ONU). It is a sequence diagram for demonstrating a synchronization method. It is a figure which shows a processing flow. It is a schematic diagram (the 1) for demonstrating guard time. It is a schematic diagram (the 2) for demonstrating guard time. It is the schematic of the conventional optical communication network.

Explanation of symbols

100 Optical communication network
200 Station side equipment (OLT)
210, 310 Interface unit 220, 320 Framer 225 Station side information insertion unit 230 Modulation unit 232, 332 Encoder 240 Adder multiplexer 250, 350 Optical module 260, 360 Clock control unit 262 125 MHz oscillator 264 2 GHz oscillator 266, 366 Clock extraction circuit 268 Clock comparison circuit 270 Distributor 280 Demodulation unit 282, 382 Decoder 284, 384 CCD matched filter 285 Station side information extraction unit 286, 386 Comparator 290 Station side control unit 300 User terminal device (ONU)
325 Subscriber side information insertion unit 345 Variable signal delay unit 367 Frequency divider 369 Clock phase adjuster 385 Subscriber side information extraction unit 390 Subscriber side control unit 400 Optical coupler
410 optical fiber
2660 Signal conversion circuit 2662 Delay circuit 2664 Comparator with hysteresis 2666 Clock recovery circuit

Claims (7)

A synchronization method in a network that performs code division multiplexing communication, which includes one station side device and a plurality of subscriber devices,
In the synchronization adjustment interval, by changing the transmission phase of each of the plurality of subscriber devices, a synchronization adjustment process for performing synchronization adjustment between the station side device and the plurality of subscriber devices,
In a user data section, comprising: a user data transmission and reception process for transmitting and receiving user data between the station side device and the plurality of subscriber devices synchronized with the station side device;
The synchronization method, wherein the synchronization adjustment section and the user data section are sequentially and repeatedly provided. In the synchronization adjustment process, among the plurality of subscriber devices, perform synchronization adjustment for one subscriber device,
The synchronization method according to claim 1, wherein a subscriber apparatus to be subjected to synchronization adjustment is switched every time the synchronization adjustment section and the user data section are repeated. Leave the new subscriber device newly connected to the network in a non-operational state,
The synchronization adjustment process further includes a synchronization adjustment start instruction process for instructing a new subscriber apparatus, which is a subscriber apparatus to be subjected to synchronization adjustment, to start synchronization adjustment.
In response to the synchronization adjustment start instruction, the new subscriber device transmits an upstream signal including a standby notification to the station-side device, and a standby state transition process for transitioning from a non-operation state to a standby state,
In response to reception of the upstream signal including the standby notification, the station side device recognizes that the new subscriber device is in a standby state and changes the transmission phase for the new subscriber device. The new subscriber unit transmits a phase adjustment instruction, changes the transmission phase in response to the phase adjustment instruction, and then transmits an upstream signal including a standby notification, and the station side unit and the new subscriber unit A transmission phase synchronization process for synchronizing
The station side device, when the station side device and the new subscriber device are synchronized, as a transmission permission notification, a transmission permission notification process of transmitting a signal indicating transmission permission to the new subscriber device;
The synchronization method according to claim 2, further comprising: a state transition process in which the new subscriber device transitions to an operation state in response to reception of a transmission permission / inhibition notification indicating that transmission is possible. The new subscriber device has its own channel number,
The instruction to start synchronization adjustment includes a subscriber channel number which is a channel number of a subscriber apparatus subject to synchronization adjustment,
In the synchronization adjustment start instruction process,
The new subscriber unit determines whether or not the subscriber channel number is equal to the own channel number, and if different, sets the self to a non-operational state and ends the synchronization adjustment process. The synchronization method according to claim 3, wherein: The station side device holds, for each subscriber device, a channel number and subscriber status information indicating an operating status, a non-operating status or a standby status,
The subscriber device holds its own channel number and self-state information indicating an operation state, a non-operation state or a standby state,
The instruction to start synchronization adjustment includes a subscriber channel number which is a channel number of a subscriber apparatus subject to synchronization adjustment, and subscriber status information of the subscriber apparatus,
In the synchronization adjustment start instruction process,
The new subscriber unit determines whether or not the subscriber channel number is equal to the own channel number, and if different, sets the self to a non-operational state and ends the synchronization adjustment process,
If the subscriber channel number and the self channel number are equal, further determine the subscriber status information and the self status information,
4. The synchronization according to claim 3, wherein when the subscriber status information indicates an operating status and the self status information indicates a non-operating status, the synchronization adjustment process is terminated after displaying terminal duplication. Method. In the synchronization adjustment process,
The said subscriber apparatus stops transmission to the said station side apparatus during the fixed area from the start of the said synchronization adjustment area to the fixed area and the completion | finish of the said synchronization adjustment area, The said 1st aspect is characterized by the above-mentioned. The synchronization method according to any one of the above. A network that performs code division multiplex communication, in which one station side device is connected to a plurality of subscriber devices,
The station side device
A synchronization adjustment section and a user data section are set, and any one of a subscriber channel number, an operation state, a non-operation state or a standby state information indicating a subscriber channel number, a transmission delay amount, and transmission availability information is set in the synchronization adjustment section. Or station side information insertion unit that inserts station side subscriber information including two or more, and generates a downlink transmission signal by arranging a frame in the user data section;
From the received signal demodulated in the station side device, the subscriber side subscriber information included in the synchronization adjustment section and the station side information extraction unit for extracting the frame included in the user data section,
Subscriber information for all subscriber devices included in the network is stored in a freely readable and rewritable manner, and the subscriber information is extracted based on the subscriber side subscriber information extracted by the station side information extracting unit. Or a station-side control unit that reads out the subscriber information and sends it as station-side subscriber information to the station-side information insertion unit,
Each of the plurality of subscriber devices is
A synchronization adjustment section and a user data section are set, subscriber side subscriber information including subscriber state information indicating an operation state, a non-operation state or a standby state is inserted into the synchronization adjustment section, and the user data section A subscriber side information insertion unit that arranges a frame and generates an uplink transmission signal;
From the received signal demodulated in the subscriber unit, the subscriber side information extraction unit for extracting the station side subscriber information included in the synchronization adjustment section and the frame included in the user data section;
Based on the station side subscriber information, the self channel number and the subscriber channel number are compared, the self state information and the subscriber state information are determined, and the self state is determined based on the comparison and the determination result. And a subscriber-side control unit that switches to an operating state, a non-operating state, or a standby state.

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