JP4697458B2 - Optical transmission system - Google Patents

Description

  The present invention relates to an optical transmission system.

  As one type of optical fiber network topology, one optical fiber from a master station is branched into a plurality of optical fibers by an optical splitter (1: n optical coupler), and a slave station is connected to the end of each optical fiber. There is a shape. Such a form is generally called a PDS (Passive Double Star) type. A so-called PON (Passive Optical Network) system is known as a typical system for bidirectional communication in a PDS type optical fiber network. In the PON system, an optical terminator OLT (Optical Line Terminal) is used as a master station, and an optical network unit (ONU) of each user is used as a slave station.

  Usually, different wavelengths are used for the downstream signal from the OLT to each ONU and the upstream signal from the ONU to the OLT. Time division multiplexing (TDM) is used for downlink signal transmission. That is, the OLT time-division multiplexes the data signal to each ONU and outputs it to the optical transmission line as a downstream optical signal. Each ONU converts the downstream optical signal into an electrical signal, takes only the data signal addressed to itself, and discards the rest.

For upstream signal transmission, all ONUs use the same wavelength for upstream optical signals, the OLT assigns transmission timing to each subscriber's ONU, and upstream data signals are optically transmitted in time slots where each ONU does not collide with each other. There are known a TDMA (Time Division Multiple Access) system that outputs to a road (Patent Document 1) and a WDM (Wavelength Division Multiplexing) system that assigns different wavelengths to uplink signals of each subscriber (Patent Documents 1 and 2). .
JP 2006-165953 A JP 2006-191618 A

  In the TDMA system, when the number of users increases, the uplink signal band that each user can occupy decreases. In order to increase the signal band occupied by each user in the TDMA system, it is necessary to increase the transmission rate of the uplink signal. However, in that case, the optical modulator of each ONU must be made high-speed corresponding to the transmission rate, and the cost of the ONU increases.

  On the other hand, since the WDM system assigns different wavelengths to each user, the number of users that can be accommodated is limited to the maximum number of receivable wavelengths preset in the OLT. For this reason, it is difficult to increase the number of users beyond the maximum number of wavelengths that can be received.

  An object of the present invention is to present an optical transmission system that can flexibly cope with an increase in users and easily secure an uplink signal band for each user.

An optical transmission system according to the present invention is an optical transmission path that optically connects a master station, a plurality of slave stations, and the master station and the slave stations, and a part of the optical transmission system An optical transmission system including an optical transmission line shared by each of the slave stations , wherein the master station temporarily stores an uplink data signal for each uplink wavelength from the plurality of slave stations, and an uplink buffer A buffer monitoring device that monitors the stored upstream data signal and recognizes the upstream signal bandwidth for each upstream wavelength and the upstream signal bandwidth of each of the plurality of slave stations, and according to the monitoring result of the buffer monitoring device, A wavelength allocation determining device that determines the allocation of the upstream wavelength used in each of the plurality of slave stations so that the upstream signal band of each of the slave stations becomes a desired value, and each of the slave stations from among a plurality of predetermined upstream wavelengths Used for upstream optical signal A wavelength allocation command generating device for generating a wavelength assignment command for upstream wavelength, and the wavelength allocation command generating device for generating the wavelength allocation command in accordance with the determination of the wavelength allocation determination unit, the slave station to use the same upstream wavelength And a bandwidth allocation command generating device for generating a bandwidth allocation command for instructing transmission of an upstream optical signal by time division multiple access (TDMA), and each of the plurality of slave stations has a wavelength-variable electrical / optical conversion. , An upstream signal supply device for supplying an upstream signal to the electrical / optical converter according to the band allocation command, and the electrical / optical converter to the upstream wavelength specified by the wavelength allocation command according to the wavelength allocation command And a wavelength control device for controlling the wavelength of the output light.

  According to the present invention, since WDM and TDMA are used in combination, the uplink signal band can be significantly increased, and the transmission band allocated to each slave station can be flexibly changed. Even if the number of users increases, it is possible to suppress or not reduce the decrease in the transmission bandwidth of existing users.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of an embodiment of the present invention. The OLT 10 is connected to the optical splitter 14 via the optical fiber 12. The optical splitter 14 is also connected to the ONUs 18-1 to 18-m of each user via branch optical fibers 16-1 to 16-m. Computers (PC) 20-1 to 20-m are connected to the respective ONUs 18-1 to 18-m. Of course, more computers, or other communication terminal devices and information processing devices can be connected to each of the ONUs 18-1 to 18-m.

In this embodiment, n optical wavelengths λ _{1 to} λ _n can be used for upstream optical signals from the respective ONUs 18-1 to 18 -m to the OLT 10. In this embodiment, the OLT 10 can specify the optical wavelength used by each ONU 18-1 to 18-m for the upstream optical signal, and the time slots different in TDMA between the ONUs using the same optical wavelength for the upstream optical signal. The upstream signal transmission timing of each ONU 18-1 to 18-m is designated so as to transmit upstream data. In the example shown in FIG. 1, the wavelength λ ₁ is assigned to the upstream optical signals of the ONUs 18-1, 18-2, and 18-3, the wavelength λ ₂ is assigned to the upstream optical signals of the ONUs 18-4 and 18-5, and the ONU 18- ( The wavelength λ _n is assigned to the upstream optical signals of m−1) and 18-m. In other words, all ONUs 18-1 to 18-m can be divided into a maximum of n groups with wavelengths used for upstream optical signals, and upstream optical signals are transmitted by WDM between groups using different upstream wavelengths. In the group using the upstream wavelength, the upstream optical signal is transmitted by TDMA. In this way, ONUs that use a plurality of wavelengths as upstream signals and that use the same upstream wavelength with a transmission rate per wavelength share each other, so that the upstream data transmission band of each ONU can be easily increased. It can be changed within a wide range.

The light sources for upstream optical signals of the ONUs 18-1 to 18-m do not have to be variable in all wavelengths [lambda] _{1 to} [lambda] _n that can be received on the OLT side, but are in a range that can be actually selected. Can be changed.

  The OLT 10 is connected to the edge router 22 of the upper network. The network interface 30 writes the downlink data frame (Ethernet (registered trademark) frame) from the edge router 22 in the downlink buffer 32. The destination MAC address acquisition device 34 acquires the destination MAC address of the downlink data frame written in the downlink buffer 32 and supplies the acquired MAC address to the header adding device 36. Further, the downlink data frame written in the buffer 32 is sequentially read out to the header adding device 36.

  In a recent PON system, a plurality of logical links are set between the OLT and the ONU so that various services such as VoIP, data communication, and VoD can be simultaneously provided. This logical link identifier is called a logical link identifier (LLID). The MAC address / LLID management table 38 is a communication terminal that uses logical link identifiers LLID logically assigned to the services of the subordinate ONUs 18-1 to 18-m and the services (for example, VoIP, data, and VoD). Stores the correspondence with the MAC address of the device.

  The header assigning device 36 searches the MAC address / LLID management table 38 for the LLID corresponding to the destination MAC address using the MAC address from the destination MAC address acquisition device 34 as a key, and downloads the header including the found LLID to the down buffer 32. Is added to the downstream data frame. The header added by the header adding device 36 is for transmission in the PON system. In this sense, in this specification, the header is called an LLID header, a PON header, or an optical transmission header.

The data frame to which the LLID header is attached by the header assigning device 36 is applied to the electrical / optical (E / O) converter 42 via the multiplexing device 40. The electrical / optical converter 42 is composed of a laser diode that oscillates at a downstream wavelength λ ₀ and converts an electrical signal into an optical signal. The output optical signal of the electrical / optical converter 42 is output to the optical fiber 12 through the WDM optical coupler 44 as a downstream optical signal. The WDM optical coupler 44 is an optical element that transmits light having a wavelength λ ₀ between the ports a and b and transmits other wavelengths λ _{1 to} λ _n between the ports b and c. FIG. 2 shows the transmission characteristics of the WDM optical coupler 44. An optical device having a similar function can be realized by an optical circulator. The downstream optical signal propagates through the optical fiber 12, enters the optical splitter 14, and is divided into m pieces. Each downstream optical signal divided by the optical splitter 14 propagates through the optical fibers 16-1 to 16-m and enters the ONUs 18-1 to 18-m. The processing contents in the ONUs 18-1 to 18-m will be described later.

Each ONU 18-1 to 18-m outputs an upstream optical signal having a wavelength specified in advance by the OLT 10 to the optical fibers 16-1 to 16-m at a transmission timing and period specified in advance by the OLT 10. This upstream optical signal includes a bandwidth request command for the OLT 10 and an upstream data signal directed to the upper network. Similar to the downlink signal, an LLID header is added to the uplink data signal. In the example shown in FIG. 1, ONU18-1~18-3 outputs the upstream optical signal of wavelength λ _1, ONU18-4,18-5 outputs the upstream optical signal of the wavelength λ _2, ONU18- (m- 1), 18-m outputs the upstream optical signal of wavelength lambda _n.

The upstream optical signals output from the respective ONUs 18-1 to 18-m propagate through the optical fibers 16-1 to 16-m, are combined by the optical splitter 14, propagate through the optical fiber 12, and are transmitted to the WDM optical coupler 44. Is incident on the port b. The WDM optical coupler 44 supplies these upstream optical signals to the optical demultiplexer 46. The optical demultiplexer 46 separates the wavelength-multiplexed upstream optical signal from the WDM optical coupler 44 into individual wavelengths λ _{1 to} λ _n, and converts each separated upstream optical signal into optical / electrical (O / E) Supply to converters 48-1 to 48-n. Such an optical demultiplexer 46 is composed of, for example, an arrayed waveguide grating. The optical / electrical converters 48-1 to 48-n are formed of so-called photodiodes, and convert incoming upstream optical signals into electrical signals.

  Each of the separation devices 50-1 to 50-n converts the output electric signals of the corresponding optical / electrical converters 48-1 to 48-n into a band request command for the OLT 10 and a signal (uplink data signal) for the upper network. ), The former is supplied to the bandwidth allocation calculation device 58, and the latter is supplied to the upstream buffers 52-1 to 52-n. The buffer monitoring device 64 monitors the upstream data signals stored in the upstream buffers 52-1 to 52-n, and grasps the upstream bandwidth usage status of each ONU 18-1 to 18-m.

  The header removers 54-1 to 54-n remove the LLID header from the uplink data signals from the corresponding buffers 52-1 to 52-n, and supply the Ethernet (registered trademark) uplink data frame to the multiplexer 56. To do. The multiplexing device 56 multiplexes the uplink data frames from the header removal devices 54-1 to 54-n on the time axis, and supplies the multiplexed uplink data frames to the network interface 30. The network interface 30 outputs the uplink data signal from the multiplexing device 56 to the edge router 22.

  In this way, the uplink data signal output from each ONU 18-1 to 18-m toward the upper network is output from the OLT 10 to the edge router 22.

In this embodiment, the OLT 10 can designate the wavelength used by each ONU 18-1 to 18-m for the upstream optical signal, and transmission timings that do not collide with each other for a plurality of ONUs that use the upstream optical signal of the same wavelength. Specify the transmission period. Details of this function of the OLT 10 will be described. The bandwidth allocation calculation device 58 performs TDMA on each of the ONUs 18-1 to 18-m according to the bandwidth request command from each of the ONUs 18-1 to 18-m supplied from the separation devices 50-1 to 50-n. A transmission band, specifically, a transmission timing and a transmission period are calculated for each upstream wavelength. In an example of using the upstream wavelength shown in FIG. 1, since the ONU18-1~18-3 use the same upstream wavelength lambda _1, the band distribution calculating unit 58, the optical fiber 12, an optical splitter 14 and optical fiber 16-1～ A transmission timing and a transmission period that do not collide with each other are determined for the ONUs 18-1 to 18-3 within the transmission band of the wavelength λ ₁ of the optical transmission line composed of 16-m.

  Based on the calculation result of the bandwidth allocation calculation device 58, the bandwidth allocation command generation device 60 generates a bandwidth allocation command that specifies the transmission timing and transmission period permitted to each ONU 18-1 to 18-m. The header assigning device 62 assigns an LLID header corresponding to the destination to the bandwidth allocation command generated by the bandwidth allocation command generating device 62. The band allocation command to which the LLID header is assigned by the header assigning device 62 is applied to the electrical / optical converter 42 via the multiplexing device 40. As in the case of the downlink data signal, the electrical / optical (E / O) converter 42 converts the electrical signal from the multiplexing device 40 into an optical signal. The output optical signal of the electrical / optical converter 42 is transmitted as a downstream optical signal through each of the ONUs 18-1 to 18-m via the WDM optical coupler 44, the optical fiber 12, the optical splitter 14, and the optical fibers 16-1 to 16-m. Is incident on. Each ONU 18-1 to 18-m takes in a bandwidth allocation command addressed to itself, and outputs an upstream optical signal at a transmission timing and a period permitted by the bandwidth allocation command.

  The buffer monitoring device 64 monitors the upstream data signal temporarily stored in the upstream buffers 52-1 to 52-n, thereby increasing the upstream signal bandwidth for each wavelength and the upstream signal bandwidth of each ONU 18-1 to 18-m. Can be recognized. The wavelength allocation determining device 66 determines the upstream wavelength of each ONU 18-1 to 18-m so that the upstream signal band of each ONU 18-1 to 18-m becomes a desired value according to the monitoring result of the buffer monitoring device 64. . In a data communication service, an uplink signal band of a certain level or more may be promised by a contract with a user. For such a user, for example, when a promised uplink signal band cannot be secured in a group using the same uplink wavelength, the promised uplink signal band is reduced by moving to a group of uplink wavelengths with fewer users. Easy to secure.

  Based on the determination by the wavelength allocation determining device 66, the wavelength allocation command generating device 68 generates a wavelength allocation command that specifies the upstream wavelength of each ONU 18-1 to 18-m. The header assigning device 70 assigns an LLID header corresponding to the destination to the wavelength assignment command generated by the wavelength assignment command generating device 68. The wavelength assignment command to which the LLID header is assigned by the header assigning device 70 is applied to the electrical / optical converter 42 via the multiplexing device 40. As in the case of the downlink data signal, the electrical / optical (E / O) converter 42 converts the electrical signal from the multiplexing device 40 into an optical signal. The output optical signal of the electrical / optical converter 42 is transmitted as a downstream optical signal through each of the ONUs 18-1 to 18-m via the WDM optical coupler 44, the optical fiber 12, the optical splitter 14, and the optical fibers 16-1 to 16-m. Is incident on. Each ONU 18-1 to 18-m takes in the wavelength allocation command addressed to itself, and controls the wavelength of the upstream signal light source to the upstream wavelength specified by the wavelength allocation command.

  FIG. 3 shows a sequence of uplink data transmission from the ONUs 18-1 to 18-m to the OLT 10 by TDMA. When there is upstream data from the computers 20-1 to 20-m, the ONUs 18-1 to 18-m first transmit a bandwidth request command for requesting a bandwidth for transmission of upstream data to the OLT 10 to the OLT 10, and the OLT 10 In response to this bandwidth request command, the bandwidth allocation command indicating the transmission timing and period is transmitted to the requesting ONUs 18-1 to 18-m. The ONUs 18-1 to 18-m that have received the bandwidth allocation command transmit uplink data at a timing and a period permitted by the OLT 10. When all the uplink data cannot be transmitted within the permitted period, the ONUs 18-1 to 18-m transmit a bandwidth request command to the OLT 10 following the uplink data.

  FIG. 4 shows a schematic block diagram of the ONU 18-1. The configurations of the other ONUs 18-2 to 18-m are the same as the ONU 18-1. The operation of the ONU 18-1 will be described with reference to FIG.

The downstream optical signal from the OLT 10 enters the port b of the WDM optical coupler 80 from the optical fiber 16-1. The transmission characteristics of the WDM optical coupler 80 are the same as those of the WDM optical coupler 44. The WDM optical coupler 80 supplies the downstream optical signal having the wavelength λ ₀ from the optical fiber 16-1 to the optical / electrical (O / E) converter 82 from the port a. The optical / electrical converter 82 is made of a photodiode, for example. The optical / electrical converter 82 converts the downstream optical signal into an electrical signal. The downstream signal output from the optical / electrical converter 82 is temporarily stored in the downstream buffer 84. The downlink signal read from the downlink buffer 84 is supplied to the separation device 88 via the normally open switch 86. This downlink signal includes a downlink data signal directed to the computer 20-1 and a control signal directed to the ONU 18-1, such as a band assignment command and a wavelength assignment command.

  The header monitoring device 90 monitors the LLID header of the electrical signal output from the optical / electrical converter 82, and closes the switch 86 via the switch control device 92 only when there is a downlink signal addressed to the buffer 84. . Thereby, only the downstream signal addressed to the ONU 18-1 is supplied to the separation device 88. It is obvious that the same operation can be realized by controlling the writing or reading of the buffer 84 instead of the opening / closing control of the normally open switch 86.

  The separation device 88 separates the downlink signal from the switch 86 into a downlink data signal addressed to the computer 20-1 and a control signal (here, wavelength allocation command and band allocation command) addressed to the ONU 18-1. Is supplied to the header removing device 94, and the latter is supplied to the ONU control device 96.

The ONU control device 96 controls the oscillation wavelength of the electrical / optical (E / O) converter 108 formed of a laser diode to a wavelength specified by the wavelength assignment command from the separation device 88. The wavelength specified here is one of the wavelengths λ _{1 to} λ _n . The ONU control device 96 also controls the upstream buffer 102 and the switch 106 so as to transmit the upstream signal at the transmission timing and period according to the band allocation command from the separation device 88. Details of the control of the upstream buffer 102 and the switch 106 will be described later.

The wavelength of the electrical / optical converter 108 does not need to be variable in all wavelengths λ _{1 to} λ _n , and may be changed within a range that can be actually selected.

  The electric / optical converter 108 capable of changing the wavelength includes, for example, a Fabry-Perot semiconductor laser and a temperature control device for controlling the temperature thereof. It is well known that the oscillation wavelength of a semiconductor laser can be changed by controlling the temperature. For example, products that can control the oscillation wavelength with a temperature dependency of about 0.4 nm / ° C. have been commercialized. Of course, other laser elements that can be changed continuously or discretely can be used.

  The header removal device 94 removes the LLID header attached by the header assignment device 36 from the downlink data signal from the separation device 88. The output of the header removing device 94 is an Ethernet (registered trademark) data frame, and is supplied to the network interface 98.

  The network interface 98 supplies the data frame from the header removing device 94 to the computer 20-1. In this way, the data signal from the host network reaches the computer 20-1.

  The network interface 98 also supplies a data frame of upstream data from the computer 20-1 to the header assigning device 100. The header assigning device 100 adds an LLID header to the data frame of the upstream data from the network interface 98 and supplies it to the upstream buffer 102. The ONU control device 96 recognizes the presence / absence of upstream data by monitoring the data stored in the upstream buffer 102.

  When the ONU control device 96 recognizes the upstream data in the upstream buffer 102, it generates a bandwidth request command as described with reference to FIG. 3, and switches the switch 106 so as to select this bandwidth request command. The bandwidth request command includes information for designating which logical link assigned to the ONU 18-1. The bandwidth request command is applied to the electrical / optical converter 108 via the switch 106. The electrical / optical converter 108 converts the electrical signal of the band request command from the switch 106 into an optical signal having the wavelength specified previously. The optical signal output from the electrical / optical converter 108 is output to the optical fiber 16-1 via the WDM optical coupler 80, and is transmitted to the OLT 10 as described above.

  In the OLT 10, the bandwidth request command from the ONU 18-1 is one of the WDM optical coupler 44, the optical demultiplexer 46, the optical / electrical converters 48-1 to 48-n, and the separating devices 50-1 to 50-. n is input to the bandwidth allocation calculation device 58 via any of n. The bandwidth allocation command generation device 60 generates a bandwidth allocation command for the ONU 18-1. The header assigning device 62 assigns an LLID header indicating a logical link that the ONU 18-1 wants to use for uplink data transmission to the bandwidth allocation command generated by the bandwidth allocation command generating device 62. The bandwidth allocation command to which the LLID header is assigned by the header assigning device 62 includes the multiplexing device 40, the electrical / optical converter 42, the WDM optical coupler 44, the optical fiber 12, the optical splitter 14, and the optical fibers 16-1 to 16-m. Then, the light enters the ONU 18-1. In the ONU 18-1, the bandwidth allocation command is input to the ONU control device 96 via the optical / electrical converter 82, the downlink buffer 84, the switch 86 and the separation device 88.

  The ONU control device 96 connects the switch 106 to the upstream buffer 102 (terminal a) and reads the upstream data signal from the upstream buffer 102 at the transmission timing and period specified by the bandwidth allocation command from the OLT 10. If all of the upstream data signal cannot be transmitted within the permitted period, the ONU controller 96 generates a further bandwidth request command, and switches the switch 106 ONU so that this bandwidth request command follows the downstream data signal transmitted. Switch to the control device 96 (terminal b). By this operation, the upstream data signal and, if necessary, the bandwidth request command that follows it are applied to the electrical / optical converter 108 and converted into an optical signal. Thereafter, as described above, the upstream optical signal output from the electrical / optical converter 108 reaches the OLT 10 and is received by the OLT 10.

  In such a transmission non-permission period, the ONU 96 switches the switch 106 to the terminal c that is not connected to the downstream buffer 102 or the ONU control device 96 so that nothing is transmitted during a period other than the period during which transmission is permitted. deep.

  When the system of the embodiment shown in FIG. 1 is started, the OLT 10 first instructs each ONU 18-1 to 18-m with the wavelength assignment command which upstream signal wavelength each ONU 18-1 to 18-m uses for upstream signal transmission. To do. Thereafter, an uplink signal transmission timing by TDMA between ONUs using the same uplink signal wavelength is determined, and the corresponding ONU is instructed by a band allocation command.

Or, at system start-up, initially, a specific wavelength of the upstream signal wavelength, for example, is set to lambda _1, to establish a logical link between the ONU18-1~18-m and OLT 10, hereinafter, each ONU18- The upstream signal wavelength and bandwidth may be indicated according to the upstream bandwidth required by 1-18-m or the upstream bandwidth permitted to each ONU 18-1 to 18-m.

  Next, the wavelength allocation processing for the ONUs 18-1 to 18-m will be described in detail. The buffer monitoring device 64 monitors the upstream buffers 52-1 to 52-n, and monitors the upstream signal band for each upstream wavelength and the upstream signal band of each ONU 18-1 to 18-m. Then, for example, when the wavelength allocation determining apparatus 66 is biased in the upstream signal band for each upstream wavelength and this bias is reduced by changing the wavelength arrangement of the ONUs 18-1 to 18-m, the ONU 18-1 Change the wavelength allocation of ~ 18-m.

で表される。 An example of an algorithm for changing the wavelength arrangement of the ONUs 18-1 to 18-m will be described. The signal band is averaged at a predetermined time with a uplink buffer 52-i and _{L i,} the upstream signal band of ONU18-j and _{B j.} i is 1 to n, and j is 1 to m. At this time, the average upstream signal bandwidth L _avg for each upstream buffer is

It is represented by

For u-th uplink buffers 52-u and v-th uplink buffers _{52-v, L u> L} avg and _L v holds _{<L avg} both, of the upstream signal bandwidth for each ONU to yet constituting a _{L u,} ( When the bandwidth of the ONU (for example, 18-j) closest to L _u −L _v ) / 2 is B _j and 0 <B _j <L _u −L _v holds, the upstream wavelength of the ONU 18-j the change in λ _v. However, 1 ≦ u ≦ n, 1 ≦ v ≦ n, and u ≠ v.

  As described above, the bias of the upstream signal band for each buffer is reduced as compared with that before the wavelength change.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

It is a schematic block diagram of one Example of this invention. This is a wavelength characteristic of the WDM optical couplers 44 and 80. It is a figure which shows the sequence of the upstream signal transmission between OLT10 and ONU18-1-18-m. It is a schematic block diagram of ONU18-1.

Explanation of symbols

10: OLT
12: Optical fiber 14: Optical splitters 16-1 to 16-m: Branch optical fibers 18-1 to 18-m: ONU
20-1 to 20-m: Computer 30: Network interface 32: Downstream buffer 34: Destination MAC address acquisition device 36: Header assigning device 38: MAC address / LLID management table 40: Multiplexing device 42: Electrical / optical (E / O) Converter 44: WDM optical coupler 46: Optical demultiplexers 48-1 to 48-n: Optical / electrical (O / E) converters 50-1 to 50-n: Separation devices 52-1 to 52-n : Upstream buffers 54-1 to 54-n: Header removal device 56: Multiplexer 58: Bandwidth allocation calculation device 60: Bandwidth allocation command generation device 62: Header assignment device 64: Buffer monitoring device 66: Wavelength allocation determination device 68: Wavelength assignment command generation device 70: header assignment device 80: WDM optical coupler 82: optical / electrical (O / E) converter 84: downstream buffer 86: normally open switch 88: separator 90: Header monitoring device 92: the switch controller 94: a header remover 96: ONU controller 98: network interface 100: a header adding unit 102: uplink buffer 106: Switch 108: Electrical / optical converter

Claims (1)

A master station (10), a plurality of slave stations (18-1 to 18-m), and an optical transmission path for optically connecting between the master station and the plurality of slave stations, some of which An optical transmission system comprising optical transmission lines (12, 14, 16-1 to 16-m) that are shared by the plurality of slave stations,
The master station
An upstream buffer (52-1 to 52-n) for temporarily storing upstream data signals for the upstream wavelengths from the plurality of slave stations;
A buffer monitoring device (64) for monitoring the upstream data signal stored in the upstream buffer and recognizing the upstream signal band for each upstream wavelength and the upstream signal bands of the plurality of slave stations;
A wavelength allocation determining device (66) that determines the allocation of the upstream wavelength used in each of the plurality of slave stations so that the upstream signal band of each of the plurality of slave stations becomes a desired value according to the monitoring result of the buffer monitoring device When,
A wavelength allocation command generating device (68) for generating a wavelength allocation command for designating an upstream wavelength that each slave station uses for an upstream optical signal from a plurality of predetermined upstream wavelengths , the wavelength allocation determining device (66) A wavelength allocation command generation device that generates the wavelength allocation command according to the determination of
Band allocation command generator (60) for generating a band allocation command for instructing a slave station using the same upstream wavelength to transmit an upstream optical signal by time division multiple access (TDMA)
And
Each of the plurality of slave stations (18-1 to 18-m) sends an upstream signal to the electrical / optical converter (108) according to the wavelength variable electrical / optical converter (108) and the band allocation command. An upstream signal supply device (96, 102, 106) to be supplied and a wavelength control device (in accordance with the wavelength assignment command) for controlling the wavelength of the output light of the electric / optical converter to the upstream wavelength specified by the wavelength assignment command ( 96). An optical transmission system comprising:

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