JP6514132B2 - Optical concentrator network system, optical transmission apparatus and optical transmission method - Google Patents

Description

  The present invention relates to an optical concentration network system, an optical transmission apparatus, and an optical transmission method for suppressing propagation delay between optical transmission apparatuses in a ring type network using PON (Passive Optical Network) or the like.

  The PON is an optical network in which one optical fiber in which a branching device (optical coupler) is inserted in the middle of an optical fiber network can be shared by a plurality of subscribers. A network to which this PON is applied is basically a tree type, and is not applied to the ring type. In PON, direct communication can not be performed between ONUs (described later) that are arbitrary nodes, and basically, only communication between the OSU and the ONU described later is supported. For this reason, communication between ONUs must necessarily go through the OSU.

  Here, in a PON in a broadband access network, an optical subscriber unit (OSU) in an optical line terminal (OLT) disposed in a central office and an optical network unit (ONU) disposed in a user's home are optical fibers and optical It is connected via a coupler. Usually, a plurality of ONUs are connected to one OSU, and TDM or TDMA (Time Division Multiple Access) is applied between the OSUs and ONUs while demultiplexing of signals (data) in the light area is performed. Transmit data By this transmission, resources such as an optical fiber core and an OLT can be shared by a plurality of users. The OLT is an optical line termination device (optical transmission device) on the station side, and the OSU is an optical line termination device (optical transmission device) of the PDS (Passive Double Star) system. The ONU is a subscriber apparatus as an optical line termination apparatus (optical transmission apparatus) on the user home side.

  FIG. 18 shows the configuration of a light concentration network system (system) 10 as a ring type network to which a conventional PON is applied. In this system 10, an optical transmission apparatus 11 as a high-order apparatus and a plurality of optical transmission apparatuses 12 and 13 as low-order apparatuses are connected as one signal transmission line via the optical demultiplexers 15, 16 and 17. The optical fiber 18 is connected in a ring shape. The optical transmission device 11 is also referred to as the upper device 11, and the optical transmission devices 12 and 13 as the lower devices 12 and 13.

  The host device 11 is provided with an OSU 21 having a TX (transmitter) and an RX (receiver) connected to the optical demultiplexing device 15. The lower devices 12 and 13 are provided with ONUs 22 and 23 having TX and RX connected to the optical demultiplexers 16 and 17, respectively. Further, an external device 25 such as a computer is connected to the OSU 21, and external devices 26 and 27 such as a computer are connected to the ONUs 22 and 23. That is, the OSU 21 is an optical line termination device that terminates signals transmitted to and received from the external device 25 and serves as a control entity, and the ONUs 22 and 23 transmit and receive signals transmitted to and from the external devices 26 and 27. It is an optical line termination device that terminates and becomes an object to the control entity.

In the system 10 to which this PON is applied, there are the following restrictions when performing communication between the OSU 21 and the ONUs 22 and 23.
(A) In downstream communication in which signals are transmitted from the OSU 21 to the ONUs 22 and 23, the optical fiber 18 can be transmitted only in one direction, clockwise or counterclockwise. In this example, it is assumed that downstream communication is performed in the counterclockwise direction indicated by a broken line arrow Y1.
(B) In upstream communication in which signals are transmitted from the ONUs 22 and 23 to the OSU 21, the same transmission path as in downstream communication can be transmitted only in the reverse direction of the upstream direction. In this example, it is assumed that upstream communication is performed clockwise as indicated by an arrow Y2 indicated by an alternate long and short dash line. That is, the down and up directions are opposite to each other, and as in the present example, if the down direction is counterclockwise Y1, the up direction is clockwise Y2.
(C) For upstream communication and downstream communication of one optical fiber, wavelengths in different frequency bands are used. In this example, it is assumed that L band λ1 (wavelength λ1 of L frequency band) is used for downlink Y1, and C band λ2 (wavelength λ2 of C frequency band) is used for uplink Y2.

  When performing communication under such constraints, for example, when performing signal transmission from ONU 22 to ONU 23, the signal is transmitted to OSU 21 in C band λ2 from ONU 22 to uplink clockwise Y2, and this signal is looped back by OSU 21 to go downstream. , And transmits to the ONU 23 in the L band λ1. As a prior art of this kind, there is a ring configuration using PON described in Non-Patent Document 1.

G. Kramer, B. Mukherjee and G. Pesavento, EthernetPON (ePON): design and analysis of an optical access network, Phot. Net. Commun., [Online], 3, 2001, [searched February 5, 2016] , Internet <URL: http://www.www.glenkramer.com/papers/epon_pnc.pdf>

  However, in the system 10 described above, since the signals from the ONUs 22 and 23 are returned by the OSU 21 and returned, if the positions of the ONUs 22 and 23 are far from the OSU 21, there is a problem that a large propagation delay occurs.

  For example, it is assumed that the ONUs 22 and 23 are disposed in the vicinity of the right side of the optical transmission device 15 connected to the OSU 21 in FIG. In this case, a signal is transmitted from the ONU 22 to the OSU 21 in the clockwise direction Y2 in the upstream direction, this signal is returned by the OSU 21 and transmitted to the ONU 23 in the counterclockwise direction Y1 in the downstream direction. In this case, since the path of the upward clockwise Y2 corresponds to about one turn of the optical fiber 18 and the path of the downward counterclockwise Y1 also corresponds to about one round, a large propagation delay of about two rounds occurs. there were. In this case, it is a fatal defect in communication that requires real-time capability.

  In order to eliminate this propagation delay, it is possible to suppress the propagation delay by preparing two PON system equipments and arranging them for clockwise and counterclockwise. However, since the system equipment is doubled, there is a problem of cost increase.

  The present invention has been made in view of such circumstances, and in a ring network to which a PON or the like is applied, an optical concentration network system capable of suppressing propagation delay between ONUs via an OSU at low cost, An object of the present invention is to provide an optical transmission device and an optical transmission method.

  As means for solving the above-mentioned problems, the invention according to claim 1 is directed to an OSU as an optical line termination device which terminates signals transmitted to and received from an external device and which becomes a control entity, and to the control entity. In the configuration in which a plurality of ONUs as optical line termination devices to be objects are cyclically connected by a ring by an optical transmission path, the OSU transmits a downstream signal to the ONU to the ring, and the ONU transmits the signal to the OSU An optical concentration network system for transmitting an upstream signal to a ring, wherein the ONU requires less than half of a ring one-round delay time in which the downstream signal from the OSU returns to the OSU via the ring. A first signal demultiplexing unit that transmits an upstream signal transmitted from the ONU to the OSU in a direction opposite to the transmission direction of the downstream signal when the ONU is located in one area; In the second region where the OSU requires a half or more of the ring one-round delay time, the upstream signal transmitted from the ONU to the OSU is in the same direction as the downstream signal transmission direction. It is a light concentration network system characterized by comprising a second signal demultiplexing unit for transmitting.

  According to this configuration, the following effects can be obtained. For example, when transmitting an upstream signal from one ONU to the OSU to the other ONU via the OSU at the time of communication between ONUs, both of the two ONUs on the transmitting and receiving side are arranged side by side in the ring right side of the OSU. Suppose that it is located in 2 areas. At this time, the counterclockwise uplink signal transmitted from the ONU on the transmission side is transmitted in the same direction as the transmission direction of the downlink signal and transmitted with a slight propagation delay to the adjacent OSU. Furthermore, it takes a propagation delay of about one round of the ring counterclockwise from the OSU to reach the receiving ONU. For this reason, transmission and reception between ONUs can be completed with a propagation delay of about one ring. In the past, transmission and reception between ONUs required a propagation delay of about two ring cycles. Therefore, according to the present invention, the propagation delay between ONUs can be suppressed.

  The invention according to claim 2 is an OSU as an optical line termination apparatus that terminates signals transmitted to and received from an external apparatus, and an optical line termination apparatus that becomes an object to the control entity. In a configuration in which a plurality of ONUs are connected in a ring by an optical transmission path in a ring, when communicating between the ONUs, the OSU always loops back and transmits to the other ONU, and the OSU transmits a downstream signal to the ONU as the ring An optical concentration network system transmitting in only one direction of the above, wherein the ONU requires less than half the ring one-round delay time in which the downstream signal from the OSU returns to the OSU via the ring. A first signal multiplexing unit for transmitting an upstream signal transmitted from the ONU via the ring in a direction opposite to a transmission direction of the downstream signal when located in the first area; The upstream signal transmitted from the ONU through the ring is a transmission of the downstream signal, when it is located in a second area including a separation unit and requiring a time longer than half of the ring 1 round delay time from the OSU. It is a light concentration network system characterized by comprising a second signal demultiplexing unit that transmits in the same direction as the direction.

  According to this configuration, the following effects can be obtained. For example, when two ONUs are located in the second area, the upstream signal transmitted from the transmitting ONU is transmitted to the adjacent OSU with a small propagation delay and is folded back, and the OSU propagates for about one ring. It takes a delay to reach the receiving ONU. For this reason, it is sufficient for the transmission and reception between ONUs to have a propagation delay of about one ring. In the past, transmission and reception between ONUs required a propagation delay of about two ring cycles. In addition, the configuration for suppressing the propagation delay requires only a small cost because only the first and second signal demultiplexing units are required. Therefore, according to the present invention, propagation delay between ONUs can be suppressed at low cost.

  In the invention according to claim 3, the OSU measures and holds the ring one-round delay time, and one path is selected for the path from the OSU to the ONU, which is the delay time of the path. If the first delay time is less than half of the held ring one round delay time, the position of the ONU is identified as the first region, and the upstream signal from the ONU is reverse to the transmission direction of the downstream signal. If the setting to transmit in the direction is made to the ONU, and the first delay time is half or more of the held ring round trip delay time, the position of the ONU is identified as the second area and the ONU 3. The optical concentration network system according to claim 1, wherein the ONU is set to transmit an upstream signal in the same direction as a transmission direction of the downstream signal.

  According to this configuration, since the OSU specifies the first or second area of the ONU, it is possible to specify the position of the ONU, regardless of where the ONU is placed on the circumference of the ring. Moreover, the transmission direction of the upstream signal from ONU can be set so that the delay time at the time of communication between the specified ONU can be suppressed.

  The invention according to claim 4 is that the OSU assigns a first wavelength to the transmission wavelength of the ONU located in the first area, and the transmission wavelength of the ONU located in the second area is different from the first wavelength A wavelength setting means for assigning a second wavelength of wavelengths is provided, and transmission is performed using any one of signals of a plurality of different wavelengths including the first and second wavelengths assigned by the wavelength setting means. It is a light concentration network system according to item 1 or 2.

  According to this configuration, the upstream signal from the ONU in the first area is transmitted in the direction opposite to the transmission direction of the downstream signal from the OSU to the ONU by the first wavelength, and the upstream signal from the ONU in the second area is the second Depending on the wavelength, it is transmitted in the same direction as the downstream signal transmission direction. Further, since different communication wavelengths can be assigned to the ONU according to the first and second regions, the ONU can be freely disposed at any position of the ring.

  In the invention according to claim 5, the OSU reciprocates between the communication target ONU and the communication path from the OSU to the ONU by a reciprocation signal transmission between the OSU and the communication path in the reverse direction of the communication path. The delay time is determined, and the ONU is located in the first region if the half value of the determined round trip delay time is less than half of the ring one round delay time, and the half if it is half or more. The light concentration network system according to claim 3, characterized in that it is specified as being located in two areas.

  According to this configuration, the OSU can accurately identify that the ONU to be communicated with is located in the first area or the second area.

In the invention according to claim 6, the OSU adds the current time of the OSU in the control signal of the downstream signal, and distributes the control signal to which the current time is added to all ONUs that accommodate the control signal. Then, the time delayed by the propagation delay time between the OSU and each ONU is set in each ONU, and the reception time in the OSU of the upstream signal from the ONU for communication located in the first area is determined. The time obtained by subtracting the round trip delay time between the OSU and the ONU from the received time is indicated to the ONU as the upstream signal transmission time at the ONU, and the upstream signal transmitted from the ONU is the OSU Command to be transmitted at the first wavelength via the communication path from the terminal to the ONU in the reverse direction, and the upstream signal from the ONU to be communicated located in the second area The reception time in the OSU is determined, and the time obtained by subtracting the ring one-round delay time from the determined reception time is indicated to the ONU as the upstream signal transmission time in the ONU, and transmitted from the ONU The upstream signal is instructed to be transmitted at a second wavelength different from the first wavelength in the same direction as the signal transmission direction from the OSU to the ONU. It is an optical concentration network system.

  According to this configuration, the OSU can receive upstream signals transmitted from a plurality of ONUs located in the first area without collision. Also, the OSU can receive upstream signals transmitted from a plurality of ONUs located in the second area so as not to collide. At this time, since the ONU in the second region transmits at a wavelength different from the transmission wavelength of the ONU located in the first region, it is possible to prevent collision with the upstream signal of the ONU in the first region.

  The invention according to claim 7 is characterized in that the ONU is a detection means for detecting that a failure has occurred in the path of the first region or the second region of the ring, and the detected failure occurrence path is located in the ONU. In the case of the area, switching control means for switching the wavelength being used for uplink transmission to a different wavelength, and the first signal multiplexing for transmitting the upstream signal transmitted with the wavelength after the switching in the opposite direction to the transmitting direction. The light concentration network system according to claim 1 or 2, further comprising: a separation unit.

  According to this configuration, the ONU transmits the upstream signal to the OSU while avoiding the path portion of the ring in which the failure has occurred, and at the same time, operates the signal from the ONU whose wavelength and path are switched by the wavelength selective switch It can be received by the OSU.

  The invention according to claim 8 is characterized in that the OSU comprises a signal demultiplexing unit configured to transmit the transmission wavelength of the downstream signal in the left or right direction of the ring, and the signal demultiplexing unit The light concentration network system according to claim 1 or 2, wherein an operation of transmitting a signal in a counterclockwise direction or a clockwise direction of the ring is performed according to the transmission wavelength of the OSU.

  According to this configuration, since the OSU can transmit the downstream signal to be transmitted to the ONU in the counterclockwise direction or the clockwise direction via the signal demultiplexing unit, when a failure occurs in the path in either direction, Can be transmitted to the ONU to be communicated.

  The invention according to claim 9 is configured such that the OSUs are two for working and protection, and the downstream signals from two OSUs are transmitted to the ONU in mutually opposite directions at different wavelengths, and the two OSUs are A detection unit for detecting occurrence of a fault in a path of the first area or the second area of the ring; and a first wavelength selection switch for switching upstream signals to the two OSUs, the detection When the means detects that a failure has occurred in the path of the first area or the second area of the ring, the current OSU is rotated clockwise and left by the first OS by the first wavelength selective switch. The upstream signal from the ONU, which is input via the rotating direction, is switched to be input to the spare OSU, and the current OSU is switched to the spare, and the spare OSU is switched to the use. Term Or optical line network system according to 2.

  According to this configuration, even if a failure occurs in the ring, communication between ONUs can be continued by the OSU.

  In the invention according to claim 10, the OSUs are two for working and protection, and downstream signals from two OSUs are transmitted to the ONU in mutually opposite directions at different wavelengths, and the two OSUs are A detection unit that detects occurrence of a failure in a path of the first area or the second area of the ring, and a second wavelength selection switch that switches the transmission direction of the downstream signal from the two OSUs; When the detection means detects that a failure has occurred in the path of the first region or the second region of the ring, the current OSU is controlled by the second wavelength selective switch to a predetermined wavelength from the current OSU 3. The light-concentrating network system according to claim 1, wherein a downstream signal transmitted in a predetermined direction is switched to be transmitted in a direction opposite to the predetermined direction at a wavelength different from the predetermined wavelength. It is a non.

  According to this configuration, even if a failure occurs in the ring, the current OSU can continue the signal return operation as it is.

  The invention according to claim 11 terminates the signal transmitted to and received from the external device, and is connected in a ring by the optical transmission path together with the upper optical transmission device as an optical line termination device as a control subject, A plurality of lower level optical transmission devices serving as optical line termination devices that become objects to a control entity, and a downstream signal transmitted from the upper level optical transmission device to the ring circulates the ring and the higher order When the subordinate optical transmission device is located in the first area that requires less than half of the ring one-round delay time to return to the optical transmission device, the upstream signal transmitted from the subordinate optical transmission device to the ring is When the subordinate optical transmission apparatus is located in a second area which transmits in the direction opposite to the transmission direction of the downstream signal and requires a time longer than half of the ring one round delay time from the superior optical transmission apparatus Up signal An optical transmission apparatus and transmits to the transmission in the same direction as the direction of the downlink signal.

  The invention according to claim 12 terminates the signal transmitted to and received from the external device, and is connected in a ring by the optical transmission path together with the upper optical transmission device as an optical line termination device as a control subject, An optical transmission method by a plurality of lower level optical transmission devices serving as an optical line terminal device serving as an object to a control entity, wherein the lower level optical transmission devices are transmitted from the upper level optical transmission device to the ring When the downstream signal is located in the first region, which requires less than half of the ring one-round delay time to travel around the ring and return to the upper level optical transmission device, the lower order optical transmission device transmits to the ring Transmitting the upstream signal in the direction opposite to the transmission direction of the downstream signal, and in the case where the upstream optical transmission apparatus is located in the second region which requires a half or more of the delay time of one round of the ring; The Ri signals are optical transmission method characterized by performing the step of transmitting to the transmission in the same direction as the direction of the downlink signal.

  According to the configuration of claim 11 and the method of claim 12, as in claim 2 above, transmission and reception between the subordinate optical transmission devices as ONUs need only be a propagation delay of about one ring, so that subordinate light can be transmitted. The propagation delay between transmission devices can be suppressed.

  The invention according to claim 13 terminates the signal transmitted / received to / from the external device, and an upper level optical transmission apparatus as an optical line terminal apparatus serving as a control subject, and an optical line serving as an object to the control subject In a configuration in which a plurality of lower-order optical transmission devices as termination devices are annularly connected by a ring by an optical transmission path, a higher-order optical transmission device that transmits downstream signals to the lower-order optical transmission devices via the ring And measuring the ring one-round delay time in which the downlink signal transmitted from the upper level optical transmission device travels around the ring and returns to the upper level optical transmission device, and the upper level optical transmission device If the first delay time, which is the delay time of one of the two paths from the lower optical transmission apparatus via the ring to the lower optical transmission device, is less than half the ring one-round delay time held, Order of optical transmission equipment Is identified as the first area, and the upstream signal transmitted to the ring from the lower level optical transmission apparatus located in the identified first area is received from the reverse direction to the downstream signal transmission direction, If one delay time is half or more of the held ring one-round delay time, the position of the subordinate optical transmission apparatus identifies the second area that requires half or more of the time, and this identified second area The optical transmission apparatus is characterized in that the upstream signal from the lower-order optical transmission apparatus located in is received from the same direction as the transmission direction of the downstream signal.

  The invention according to claim 14 terminates the signal transmitted / received to / from the external device, and an upper level optical transmission apparatus as an optical line termination apparatus as a control subject, and an optical line as an object with respect to the control subject In a configuration in which a plurality of lower-order optical transmission devices as termination devices are annularly connected by a ring by an optical transmission path, a higher-order optical transmission device that transmits downstream signals to the lower-order optical transmission devices via the ring The optical transmission method according to claim 1, wherein the upper-layer optical transmission device has a ring one-round delay time in which the downstream signal transmitted from the upper-layer optical transmission device travels around the ring and returns to the upper-layer optical transmission device A step of measuring and holding, and a first delay time which is a delay time of one of two paths from the upper optical transmission apparatus to the lower optical transmission apparatus via the ring; One ring If it is less than half of the delay time, the step of identifying the position of the lower light transmission apparatus as the first area, and the uplink transmitted from the lower light transmission apparatus located in the specified first area to the ring The step of receiving the signal in the direction opposite to the transmission direction of the downstream signal, and if the first delay time is not less than half of the held ring one-round delay time, the position of the subordinate optical transmission device is Identifying the second area requiring half or more of the time, and receiving the upstream signal from the lower level optical transmission apparatus located in the identified second area from the same direction as the downstream signal transmission direction Performing the steps of performing the light transmission method.

  According to the configuration of claim 13 and the method of claim 14, as in claim 3, the upper level optical transmission apparatus as the OSU specifies the first or second area of the lower level optical transmission apparatus as the ONU. Do. For this reason, even if the lower light transmission apparatus is disposed at any position on the circumference of the ring, the position can be specified. Further, it is possible to receive an upstream signal from the lower optical transmission apparatus so that the delay time during communication between the identified lower optical transmission apparatuses can be suppressed.

  According to the present invention, it is possible to provide an optical concentration network system, an optical transmission apparatus, and an optical transmission method capable of suppressing propagation delay between ONUs via an OSU at low cost in a ring network to which PON or the like is applied. Can.

FIG. 1 is a block diagram showing a configuration of a light concentration network system according to a first embodiment of the present invention. It is a block diagram showing composition of OSU of a light concentration network system of an embodiment. It is a block diagram showing composition of ONU of a light concentration network system of an embodiment. FIG. 2 is a block diagram showing the configuration of an optical demultiplexing apparatus on the OSU side of the light concentration network system of the first embodiment. FIG. 8A is a block diagram showing the configuration of an ONU in the left area of the optical concentration network system of the first embodiment, and FIG. 7B is a block diagram showing the configuration of an ONU in the right area. is there. It is a flowchart for demonstrating the light transmission operation | movement by the light concentration network system of 1st Embodiment. It is a block diagram which shows the structure of OSU and the optical demultiplexing apparatus in the optical concentration network system which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of ONU of 2nd Embodiment, and an optical demultiplexing apparatus. It is a block diagram which shows the structure of the optical concentration network system which concerns on 3rd Embodiment of this invention. It is a sequence diagram for demonstrating the operation | movement of the optical concentration network system of 3rd Embodiment. It is a sequence diagram for demonstrating the other operation | movement of the optical concentration network system of 3rd Embodiment. It is a block diagram which shows the structure of ONU and the optical demultiplexing apparatus in the optical concentration network system which concerns on 4th Embodiment of this invention. It is a block diagram which shows the failure generation to the optical fiber in the optical concentration network system of 4th Embodiment. It is a block diagram which shows the structure of OSU and the optical demultiplexing apparatus in the optical concentration network system which concerns on 5th Embodiment of this invention. It is a block diagram which shows the structure of the optical concentration network system which concerns on 6th Embodiment of this invention. It is a block diagram which shows the 1st structure of the optical demultiplexing apparatus by the side of 2 units | sets of OSU of the optical concentration network system of 6th Embodiment. It is a block diagram which shows the 2nd structure of the optical demultiplexing apparatus by the side of 2 units | sets of OSU of the optical concentration network system of 6th Embodiment. It is a block diagram which shows the structure of the conventional light concentration network system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Configuration of First Embodiment>
FIG. 1 is a block diagram showing the configuration of a light concentration network system according to a first embodiment of the present invention.
The light concentration network system 30 shown in FIG. 1 constitutes a ring network to which the above-mentioned PON (Passive Optical Network) is applied. In this system 30, an optical transmission apparatus 31 as a high-order apparatus and a plurality of optical transmission apparatuses 32 and 33 as low-order apparatuses are connected as one signal transmission line via the optical demultiplexers 35, 36 and 37. The optical fiber 38 is connected in a ring shape. The optical transmission apparatus 31 is also referred to as the upper apparatus 31, and the optical transmission apparatuses 32 and 33 as the lower apparatuses 32 and 33. Further, the upper apparatus 31 constitutes a higher-order optical transmission apparatus described in claims, and the lower apparatuses 32 and 33 constitute a lower-order optical transmission apparatus described in claims. The optical fiber 38 is also referred to as a ring.

  An OSU (Optical Subscriber Unit) 41 having a TX (transmitter) and an RX (receiver) connected to the optical demultiplexer 35 is provided in the upper device 31. In the lower devices 32 and 33, ONUs (Optical Network Units) 42 and 43 having TX and RX connected to the optical demultiplexers 36 and 37 are provided. Further, an external device 45 such as a computer is connected to the OSU 41, and external devices 46 and 47 such as a computer are connected to the ONUs 42 and 43. The OSU 41 includes the optical demultiplexing device 35 to constitute the OSU recited in the claims. The ONUs 42 and 43 include the optical demultiplexing devices 36 and 37 to constitute the ONU according to the claims.

  Next, the configuration of the OSU 41 will be described with reference to FIG. The OSU 41 includes a buffer unit 51, an optical burst reception unit 52, a continuous signal reception unit 53, a MUX (multiplexing) unit 54, a signal separation unit 55, a control information reception unit 56, a delay measurement unit 57, and a path. A determination unit 58, an internal clock unit 59, a counter management unit 60, a TS (time slot) control unit 61, and an optical transmission unit 62 are provided.

The buffer unit 51 accumulates data which is the client signal o1 received from the external device 45, and transmits the accumulated data i1 from the TX to the optical transmission unit 62. Also, the data i2 separated by the signal separation unit 55 is received by RX, and the received data is transmitted to the external device 45 as a client signal o2.
The optical burst receiving unit 52 receives the burst signal x1 transmitted from the ONUs 42 and 43 through the optical demultiplexing device 35.
The continuous signal reception unit 53 receives the continuous signal y1 that has been circulated around the ring 1 after transmission by the OSU 41.

The MUX unit 54 generates the burst signal x1 of the ring 1 continuous signal y1 from the OSU 41 received by the continuous signal receiving unit 53 and the burst signals x1 from the ONUs 42 and 43 received by the optical burst receiving unit 52. Packet multiplexing is performed so as not to collide with the continuous signal y 1, and output to the signal separation unit 55.
The signal separation unit 55 separates the received continuous signal y1 and burst signal x1 into the data signal i2 and the control signal j1, outputs the control signal j1 to the control information reception unit 56, and the data signal i2 to the buffer unit 51. Output.

The control information reception unit 56 responds to the received control signal j1 to assign TS information f1 to the TS control unit 61, TS information e1 from the ONUs 42 and 43 to the delay measurement unit 57, and reference time information c1 to the counter management unit Output to 60
The internal clock unit 59 supplies, to the counter management unit 60, the clock signal b1 for advancing the counter value present in the counter management unit 60.
The counter management unit 60 outputs the counter value g1 obtained by incrementing the reference value to the delay measurement unit 57 and the TS control unit 61 according to the clock signal b1.

  The delay measuring unit 57 is an RTT that is a round trip delay time of the current route between the ONUs 42 and 43 and the OSU 41 from the TS value e1 described in the control signal j1 from the ONUs 42 and 43 and the counter value g1 from the counter managing unit 60. (Round Trip Time), and measure the ring 1 round delay time. The measurement result signal n1 is output to the TS control unit 61 and the path determination unit 58.

  The path determination unit 58 determines the path from the ONUs 42 and 43 to the upstream OSU 41 according to the communication destinations of the ONUs 42 and 43 and the delay time between the ONUs 42 and 43 and the OSU, and the ONUs 42 and 43 further Calculate the wavelength to be used. The calculated use wavelength information s1 is output to the TS control unit 61.

The TS control unit 61 adds the TDM control timing necessary for each route as a time stamp to the control signal based on the route based on the utilization wavelength information s 1, and notifies the control signal k 1 to the optical transmission unit 62.
The optical transmission unit 62 includes the data signal i1 transmitted to the ONUs 42 and 43, the counter value g1 in the counter management unit 60, the ring one-round delay time, the data transmission timing of each ONU 42 and 43, and each ONU 42 and 43 The used wavelength information s1 to be used is added to the optical signal and transmitted to the ONUs 42 and 43 through the optical demultiplexer 35.

  Next, the configuration of the ONUs 42 and 43 will be described with reference to FIG. Each ONU 42, 43 has the same configuration, and only one configuration is shown in FIG. The ONUs 42 and 43 include a buffer unit 71, an optical receiving unit 72, a signal separation unit 73, a control information receiving unit 74, an internal clock unit 75, a counter managing unit 76, a TS control unit 77, and an optical burst transmission. And a unit 78.

The buffer unit 71 accumulates data as the client signal o3 received from the external devices 46 and 47, and transmits the accumulated data i3 from the TX to the optical burst transmission unit 78. Also, the data i4 separated by the signal separation unit 73 is received by the RX, and the received data is transmitted as the client signal o4 to the external devices 46 and 47.
The light receiving unit 72 receives the continuous signal x2 from the OSU 41.
The signal separation unit 73 separates the received continuous signal x 2 into the data signal i 4 and the control signal j 2, and outputs the control signal j 2 to the control information reception unit 74 and the data signal i 4 to the buffer unit 71.

  The control information receiving unit 74 receives the control signal j2 and outputs the reference time information c2 from the OSU 41 to the counter managing unit 76. Further, the reference time information from the OSU 41, used wavelength information, TS transmission timing, allocation The TS information is output to the TS control unit 77 as indicated by a symbol f2.

The internal clock unit 75 supplies the counter management unit 76 with a clock signal b2 for advancing the counter value present in the counter management unit 76.
The counter management unit 76 outputs the counter value g2 obtained by incrementing the reference value to the light burst transmission unit 78 and the TS control unit 77 in accordance with the clock signal b2.

The TS control unit 77 compares the counter value g2 with the timing value described in the allocation TS information according to the allocation TS information from the OSU 41, and controls the TS transmission operation to the light burst transmission unit 78 by the control signal h2. Do.
The optical burst transmitter 78 combines the data signal to be transmitted to the OSU 41 and the control signal (including the current time), and transmits the optical burst signal at the wavelength according to the control instruction of the TS controller 77. Send to OSU 41 via

In the system 30 shown in FIG. 1 having such a configuration, in the communication between the ONUs 42 and 43 via the OSU 41, in the present embodiment, rules for communication are defined as follows.
(1) In downstream communication in which downstream signals are transmitted from the OSU 41 to the ONUs 42 and 43, only one direction of clockwise or counterclockwise rotation of the ring can be transmitted. This is a rule defined by PON, and in this example, downstream communication is performed in the counterclockwise direction indicated by a broken line arrow Y11.
(2) Upstream communication for transmitting upstream signals from the ONUs 42 and 43 to the OSU 41 is defined as follows. Less than half (indicated by a broken line H1) of the ring one-round delay time D transmitted from the OSU 41 and returned to the OSU 41 is the left area (first area), and half or more is the right area (second area). The ONU 42 located in the left area transmits the upstream signal clockwise (upper right), as indicated by a dashed dotted arrow Y12. The ONU 43 located in the right area transmits the upstream signal counterclockwise (upper left) as indicated by an arrow Y13 indicated by an alternate long and short dash line.
(3) The wavelengths in different frequency bands are used for uplink communication and downlink communication of the ring. In this example, it is assumed that L band λ1 (wavelength λ1 of L frequency band) is used for downlink communication (Y11) and C band λ2 (wavelength λ2 of C frequency band) is used for uplink communication (Y12, Y13). Each frequency band may be different and the same wavelength may be used. For example, the L band λ1 and the C band λ1 may be used.

Next, the configuration of the optical demultiplexing devices 35 to 37 for performing such communication will be described with reference to FIGS. 4 and 5. FIG.
FIG. 4 is a block diagram showing the configuration of the optical demultiplexer 35 connected to the OSU 41. As shown in FIG. The optical demultiplexing device 35 is configured to include band separation filters 35a and 35b on both sides and an optical coupler 35c which is a signal demultiplexing unit. An optical fiber 38 is connected to the left and right band separation filters 35a and 35b. In the optical fiber 38 shown in FIG. 4, (L) is attached to the optical fiber 38 corresponding to the left side as viewed in FIG. 1, and (R) is attached to the optical fiber 38 corresponding to the right side.

The band separation filters 35a and 35b shown in FIG. 4 separate the downstream signal and the upstream signal by separating the frequency bands of the L band λ1 (λ1) and the C band λ2 (λ2).
The left band separation filter 35a separates the signal of the L band λ1 (λ1) transmitted from the TX of the OSU 41, and transmits only λ1 to the ONUs 42 and 43 as a downstream signal to the optical fiber 38 (L). In addition, the band separation filter 35a separates the upstream signal of the C band λ2 (λ2) transmitted via the optical fiber 38 (L) and inputs it to the optical coupler 35c. The optical coupler 35 c outputs the input upstream signal of λ 2 to the RX of the OSU 41.

  The band separation filter 35b on the right side separates the upstream signal of the C band λ2 (λ2) transmitted via the optical fiber 38 (R) and inputs it to the optical coupler 35c, and the optical coupler 35c receives the input And outputs the upstream signal of λ2 to RX. The band separation filter 35b separates the signal of λ1 transmitted from the TX of the OSU 41 and having traveled around the optical fiber 38, and outputs the separated signal to the RX via the optical coupler 35c.

  FIG. 5A is a block diagram showing the configuration of the optical demultiplexer 36 connected to the ONU 42 located in the left area (FIG. 1). The optical demultiplexing device 36 is configured to include band separation filters 36a and 36b on both sides, wavelength filters 36c, 36d and 36e by optical filters that are signal demultiplexing units, and optical couplers 36f and 36h. This feature is an optical coupler 36h, in which the upstream signal of λ2 transmitted from the ONU 42 is output by the optical coupler 36h only in the ring clockwise direction (see FIG. 1) as indicated by the arrow Y12. is there. Similarly to this, the optical coupler 36 h outputs the upstream signal of λ 2 that has been received by the right band separation filter 36 b via the optical fiber 38 (R) in the ring clockwise direction only. With this configuration, the ONU 42 located in the left area {see (2) above} can transmit the upstream signal clockwise as indicated by the arrow Y12.

  The other optical demultiplexer 36 will be described. The downstream signal of λ1 from the OSU 41 that has passed through the optical fiber 38 (L) is separated after being input to the left band separation filter 36a, and is output to the wavelength filter 36e side by the optical coupler 36f via the wavelength filter 36c. , RX received. Besides, the downstream signal is separated from the optical coupler 36 f through the wavelength filter 36 d by the right band separation filter 36 b and transmitted to the optical fiber 38 (R). On the other hand, the upstream signal of C band λ 2 that has passed through the optical fiber 38 (R) is separated after reception by the band separation filter 36 b on the right side, and is separated through the optical coupler 36 h and the band separation filter 36 a. Sent to).

  FIG. 5B is a block diagram showing the configuration of the optical demultiplexer 37 connected to the ONU 43 located in the right area (FIG. 1). The optical demultiplexing device 37 also has the same configuration as the optical demultiplexing device 36 described above, and is different from the optical coupler in FIG. The optical coupler 36 h 1 is configured to output the upstream signal of the C band λ 2 transmitted from the ONU 43 only in the ring counterclockwise direction (see FIG. 1) as indicated by the arrow Y 13. Similarly, the optical coupler 36h1 outputs the upstream signal of λ2 that has been received by the left band separation filter 36a via the optical fiber 38 (L) in the ring left-handed direction only. With this configuration, the ONU 43 located in the right area described above can transmit the upstream signal in the counterclockwise direction, as indicated by the arrow Y13.

  As described above, when the OSU 41 transmits the downstream signal of λ1 counterclockwise, the ONU 42 located in the left region transmits the upstream signal of λ2 clockwise, and the ONU 43 located in the right region transmits the upstream signal of λ2 The configuration of transmitting counterclockwise can also be applied to systems of ring networks other than PON. The configuration of the ring network system other than the PON corresponds to the optical concentration network system according to claim 1.

<Optical Transmission Method of First Embodiment>
Next, the light transmission operation by the light concentration network system 30 will be described with reference to the flowchart shown in FIG.

  In step S1 of FIG. 6, the OSU 41 returns from the OSU 41 to the OSU 41 to return to the OSU 41 for a half cycle of the propagation delay time (ring one-round delay time D) of the downstream signal of the L band λ1 for one round. Determined as (first area). Next, in step S2, half or more of the ring one-round delay time D is determined as the right area (second area).

  In step S3, the OSU 41 determines which of the left and right areas the ONUs 42 and 43 are located. As a result, when the ONU 42 is located in the left area, in step S4, the upstream signal transmitted from the ONU 42 in the left area to the OSU 41 is transmitted in the clockwise direction opposite to the transmission direction of the downstream signal. This transmission is performed by the optical coupler 36h shown in FIG. 5A outputting the upstream signal of λ2 transmitted from the ONU 42 in the ring clockwise direction (see FIG. 1) as indicated by the arrow Y12. .

  On the other hand, when the ONU 43 is located in the right area as a result of the determination in step S3, in step S5, the upstream signal transmitted from the ONU 43 in the right area to the OSU 41 is transmitted counterclockwise in the same direction as the downstream signal transmission direction. Do. This transmission is performed by the optical coupler 36h1 shown in FIG. 5B outputting the upstream signal of λ2 transmitted from the ONU 43 in the ring counterclockwise direction (see FIG. 1) as indicated by the arrow Y13. .

<Effect of First Embodiment>
As described above, as shown in FIG. 1, the optical concentration network system 30 according to the first embodiment terminates the signal transmitted to and received from the external device 45, and serves as an optical line termination device to be a control subject. The OSU 41 and a plurality of ONUs 42 and 43 as optical circuit terminating devices serving as objects with respect to the control subject are annularly formed in a ring by an optical transmission line via optical demultiplexing devices 35 to 37 that demultiplex and demultiplex signals. It has a connected configuration. In this configuration, when communicating between the ONUs 42 and 43, an upstream signal from one ONU 42 to the OSU 41 is returned by the OSU 41 and transmitted to the other ONU 43, and the OSU 41 transmits downstream signals to the ONUs 42 and 43 in one direction of the ring only. Send to Here, it is assumed that transmission is performed in the counterclockwise direction indicated by the arrow Y11.

  A feature of the present invention is that the ONUs 42 and 43 are upstream transmitted from the ONU 42 to the OSU 41 when, for example, the ONU 42 is located from the OSU 41 to the left region as the first region requiring less than half of ring one-ring delay time D. An optical coupler 36h (FIG. 5A) is provided as a first signal demultiplexing unit that transmits a signal in the direction opposite to the transmission direction of the downstream signal. On the other hand, when the ONU 43 is located in the right area as the second area which requires less than half of the ring 1 round delay time from the OSU 41, the upstream signal transmitted from the ONU 43 to the OSU 41 is the transmission direction of the downstream signal. An optical coupler 36h1 (FIG. 5B) as a second signal demultiplexing unit for transmitting in the same direction is provided.

  According to this configuration, the following effects can be obtained. It is assumed that two second optical transmission devices 32 and 33 are located in the right area adjacent to the host device 31. In this case, each of the ONUs 42 and 43 is configured to transmit the upstream signal in the same direction as the downstream signal transmission direction. In this configuration, the upstream signal transmitted from the ONU 42 on the transmitting side is transmitted in the counterclockwise direction, turned back by the adjacent OSU 41, and transmitted counterclockwise as the downstream signal, requiring a propagation delay of about one ring from the OSU 41. Thus, the ONU 43 on the receiving side is reached. For this reason, the propagation delay of about one ring is sufficient for transmission and reception of the ONUs 42 and 43. In the prior art to be described later, transmission and reception between the ONUs 42 and 43 requires a propagation delay of about two ring cycles. Further, the configuration for such propagation delay suppression requires only the optical couplers 36 h and 36 h 1 and therefore costs only a small amount. Therefore, according to the present embodiment, it is possible to suppress the propagation delay of the signal between the ONUs 42 and 43 folded back by the OSU 41 at low cost.

  In the prior art, since the upstream signal transmitted from the ONU 42 on the transmission side is always transmitted in the opposite direction to the downstream signal of the OSU 41, a propagation delay of about one ring is required when reaching the OSU 41 first. Furthermore, when it is turned back by the OSU 41 and reaches the ONU 43 on the receiving side, a propagation delay of about one ring is required. For this reason, the propagation delay for about two rounds of rings was applied to transmission and reception between the ONUs 42 and 43.

<Configuration of Second Embodiment>
FIG. 7 is a block diagram showing the configuration of an OSU and an optical demultiplexing apparatus in an optical concentration network system according to a second embodiment of the present invention. FIG. 8 is a block diagram showing the configuration of an ONU and an optical demultiplexing apparatus according to the second embodiment.
The features of the light concentration network system 30 according to the second embodiment include the process (area specifying process) for specifying the left area and the right area described in the first embodiment, the upstream signal of the ONU 42 in the left area, and the ONU 43 in the right area. Processing to set different transmission directions of uplink signals (transmission direction setting processing), and processing to set uplink signals of each transmission direction to different wavelengths λ2 and λ3 {[C band λ3] on arrow Y13 side in FIG. And (wavelength setting processing) is performed automatically.

  The above processes are performed by the path determination unit 58 (see FIG. 2) of the OSU 41 shown in FIG. 7, the optical demultiplexing device 35 connected to the OSU 41, and the optical demultiplexing device connected to the ONUs 42 and 43 shown in FIG. 36 and 37 are performed.

  The path determination unit 58 performs the area specifying process and the transmission direction setting process. First, the path determination unit 58 measures the delay time until the signal transmitted from the OSU 41 travels around the optical fiber 38, returns to the OSU 41, and is received (referred to as “one-ring delay time D”). It is held in storage means such as a memory (not shown).

  Next, the delay time DA from the OSU 41 to the ONUs 42 and 43 is measured, and if this measurement result DA is less than half of the held ring round trip delay time D, it is identified as the left area. After this specification, the upstream signal transmitted from the ONU 42 in the left area to the OSU 41 is set to be transmitted in the clockwise direction (Y12) opposite to the transmission direction of the downstream signal. On the other hand, if the above measurement result DA is half or more of the ring one-round delay time D, it is identified as the right region. After this specification, the upstream signal transmitted from the ONU 43 in the right area to the OSU 41 is set to be transmitted in the counterclockwise direction (Y13) in the same direction as the downstream signal transmission direction.

  Next, the path determination unit 58 performs processing for assigning and setting different wavelengths to the signal transmission wavelengths of the ONUs 42 and 43 in the left and right regions. For example, the C band λ2 (λ2) is allocated to the transmission wavelength of the ONU 42 in the left area, and the C band λ3 (λ3) is allocated to the transmission wavelength of the ONU 43 in the right area. At this time, the function of selecting the respective wavelengths λ2 and λ3 for the optical multiplexer / demultiplexer 35 on the OSU 41 side shown in FIG. 7 and the wavelength λ2 and λ3 for the optical demultiplexers 36 and 37 on the ONUs 42 and 43 shown in FIG. And the function of distributing The path determination unit 58 constitutes a wavelength setting unit described in the claims.

First, a wavelength filter 35e is provided in the optical demultiplexing device 35 shown in FIG. That is, the optical demultiplexing device 35 shown in FIG. 7 has a configuration in which the optical coupler 35c of the optical demultiplexing device 35 shown in FIG. 4 described above is replaced with the wavelength filter 35e of FIG.
The wavelength filter 35e outputs one of the plurality of input signals to the RX. For example, the wavelength filter 35 e is an upstream signal of the C band λ 2 (λ 2) from the optical fiber 38 (L) separated by the left band separation filter 35 a and the optical fiber 38 separated by the right band separation filter 35 b ( One of the upstream signals of C band λ3 (λ3) or L band λ1 (λ1) from R) is output to RX of OSU 41. However, although only one OSU 41 is shown in FIG. 7, when there are two or more, one path is connected to two paths in the opposite direction from the two OSU 41 to the ONUs 42 and 43. It is assumed that

Next, a wavelength filter 36i is provided in the optical demultiplexing devices 36 and 37 shown in FIG. That is, the optical demultiplexing devices 36 and 37 shown in FIG. 8 have a configuration in which the optical coupler 36h of the optical demultiplexing device 36 shown in FIG. 5A described above is replaced with the wavelength filter 36i of FIG. .
When the wavelength filter 36i is mounted on the optical demultiplexing apparatus 36 connected to the ONU 42 in the left area, the upstream signal of λ2 transmitted from the ONU 42 is transmitted through the band separation filter 36a as indicated by the arrow Y12. Output in the clockwise direction of the ring (see FIG. 1). Further, when the wavelength filter 36i is mounted on the optical demultiplexing apparatus 37 connected to the ONU 43 in the right area, the upstream signal of λ3 transmitted from the ONU 43 is indicated by the arrow Y13 as the band separation filter 36b. Output in the ring counterclockwise direction (see FIG. 1) via.

  Such setting in the clockwise direction and counterclockwise direction of the wavelength filter 36i is performed when the path setting unit 58 performs the above-described wavelength setting process. That is, when the ONU 42 is located in the left area, the path determination unit 58 assigns the transmission wavelength of the C band λ 2 to the ONU 42, and outputs the upstream signal of λ 2 from the wavelength filter 36 i in the clockwise direction (Y12). To be done. On the other hand, when the ONU 43 is located in the right region, the upstream wavelength of λ3 is output from the wavelength filter 36i in the counterclockwise direction (Y13) by assigning the transmission wavelength of the C band λ3 to the ONU 43. The operation of transmitting the C band λ2 or the C band λ3 set in this way from the ONUs 42 and 43 is performed by the optical burst transmitting unit 78 (FIG. 3) of the ONUs 42 and 43.

<Effect of Second Embodiment>
The system 30 of the second embodiment has the following characteristic configuration.

  (1) The OSU 41 measures and holds the ring one-round delay time D by the path determination unit 58, selects one path for the path from the OSU 41 to the ONU 42, and delays the delay time DA of the path If the delay time) is less than half of the held one round ring delay time D, the position of the ONU 42 is identified as the left region, and the upstream signal from the ONU 42 is in the reverse direction to the downstream signal transmission direction. The ONU 42 is set to transmit in the clockwise direction. Further, if the delay time DA is equal to or more than half of the held one round ring delay time D, the position of the ONU 43 is identified as the right area, and the upstream signal from the ONU 43 is the same as the downstream signal transmission direction. The ONU 43 is set to transmit in the counterclockwise direction of the direction.

  As a result, the OSU 41 specifies the left or right region of the ONUs 42 and 43 and sets the transmission direction of the upstream signal, so that even if the ONUs 42 and 43 are disposed at any position on one ring circumference, their positions can be identified. . By this specification, the transmission direction of the upstream signal from the ONUs 42 and 43 can be set so that the delay time during communication between the ONUs 42 and 43 can be suppressed.

  (2) The OSU 41 includes the path determination unit 58 as a wavelength setting unit that assigns the wavelength λ2 to the transmission wavelength of the ONU 42 located in the left area and assigns the wavelength λ3 different from the wavelength λ2 to the transmission wavelength of the ONU 43 located in the right area . Further, the configuration is such that transmission is performed using any one of signals of a plurality of different wavelengths including the first and second wavelengths assigned by the path determination unit 58.

  According to this configuration, the upstream signal from the ONU 42 in the left area is transmitted clockwise in the direction opposite to the transmission direction of the downstream signal from the OSU 41 to the ONU 42 by the wavelength λ2, and the upstream signal from the ONU 43 in the right area is the wavelength Transmission is performed in the same direction as the downstream signal transmission direction by λ3. Further, since different communication wavelengths can be assigned to the ONUs 42 and 43 according to the left and right regions, the ONUs 42 and 43 can be freely disposed at arbitrary positions of the ring.

<Configuration of Third Embodiment>
The third embodiment of the present invention is characterized in the process of setting the transmission timing of the upstream signal from the ONUs 42 and 43 to the OSU 41 described above. Therefore, FIG. 9 shows a system 30 having the same configuration as that of FIG. 1, and arrows Y21, Y22, and Y23 for describing the features of the third embodiment are attached.

  The delay measuring unit 57 (FIG. 2) of the OSU 41 shown in FIG. 9 measures RTT (Round Trip Time) which is the delay time between the OSU 41 and the ONU (referred to as 42) as indicated by arrows Y21 and Y22. . The operation along the time axis at the time of measurement will be described with reference to the sequence diagram of FIG. In FIG. 10, the OSU 41 sets the local time T0 of the OSU itself as the transmission time, adds a time stamp “T0” of this time in the control signal of the downstream signal, and indicates the L band λ1 (λ1) as shown by arrow Y21. It transmits to ONU42. The transmitted time stamp “T0” is received by the ONU 42 with a delay time D1 delayed.

  In the ONU 42, the reception time is T0, and when T0, the relative time of the OSU 41 is D1 + T0. Next, the ONU 42 transmits the upstream signal at time T1 in the reverse direction through the path through which the downstream signal from the OSU 41 passes. At the time of this transmission, the ONU 42 attaches a time stamp “T1” in the control signal of the upstream signal, and transmits it to the OSU 41 in the C band λ2 (λ2) as indicated by the arrow Y22.

  The time when the OSU 41 receives the time stamp “T1” is T2. Since the received data in the OSU 41 includes the time stamp "T1", the OSU 41 subtracts the time stamp "T1" from the time of the OSU 41 at the time of receiving the time stamp using the time stamp "T1". The round trip delay time RTT (D1 + D1 = 2D1) between the OSU 41 and the ONU 42 is obtained. The OSU 41 can determine whether the position of the ONU 42 is the left area or the right area by subtracting the half value of the round trip delay time RTT from the ring first round delay time D. This can be similarly obtained in the ONU 43.

  However, when the OSU 41 obtains the ring one-round delay time D, it sends packet data to the optical fiber 38 via the respective optical demultiplexers 35 to 37, and receives and obtains packet data returned to its own OSU 41. ing.

  Further, after the identification of the left and right areas, in order for the ONU 42 located in the left area to cause the data from the ONU 42 to arrive at the predetermined reception time (arrival time) T2 of the OSU 41, the ONU 42 subtracts RTT from the arrival time T2. It may be sent at the timing of. For this purpose, the OSU 41 instructs the ONU 42 in the left region to transmit at the wavelength λ2 in the reverse direction of the downstream passing path from the OSU 41. As a result, after receiving the downstream signal (Y21) from the OSU 41, the ONU 42 transmits the upstream signal at the wavelength λ2 in the reverse direction of the downstream path as indicated by the arrow Y22 at timing T2-RTT.

  Next, in order for the ONU 43 located in the right area to cause the data from the ONU 43 to arrive at the predetermined reception time (arrival time) T2 of the OSU 41, the ONU 43 subtracts the one-ring delay time D from the arrival time T2. It may be sent at the timing of.

  The transmission timing will be described with reference to the sequence diagram of FIG. In FIG. 11, the transmission from the OSU 41 to the ONU 43 in the right area is performed in the same manner as the transmission to the ONU 42 in the left area described above. The ONU 43 in the right area, which has received the downstream signal from the OSU 41 at time T0, transmits the upstream signal at time T1a in the same direction as the downstream path of the OSU 41 as indicated by the arrow Y23 (see FIG. 10). At the time of this transmission, the ONU 43 transmits to the OSU 41 in the C band λ3 (λ3) as indicated by the arrow Y23. The uplink signal transmitted in the counterclockwise direction requires the delay time D3 and is received by the OSU 41 at time (arrival time) T2. The relative time of the ONU 43 at this time T2 is “T2-D1”.

  The time when the propagation delay time D3 is subtracted from this "T2-D1" (T2-D3-D1), that is, T2- (D3 + D1) is the upstream signal transmission timing from the ONU 43 in the right area. Since D3 + D1 is the ring 1 round delay time D, the upstream signal transmission timing from the ONU 43 in the right area is the time T1a obtained by subtracting the ring 1 round delay time D from the arrival time T2 to the OSU 41.

  That is, the OSU 41 instructs the ONU 43 in the right area to transmit with the wavelength λ3 in the same direction as the downstream passing path from the OSU 41. Thus, after receiving the downstream signal (Y21) from the OSU 41, the ONU 43 transmits the upstream signal at the wavelength of λ3 in the same direction as the downstream path as indicated by the arrow Y23 at the timing of time T2- (D3 + D1). Do.

<Effect of Third Embodiment>
The system 30 of the third embodiment has the following characteristic configuration.
(1) The OSU 41 obtains the round trip delay time due to the reciprocation signal transmission between the communication path from the OSU 41 to the ONUs 42 and 43 and the communication path heading in the reverse direction to the communication target ONU. The value of 1⁄2 of the round trip delay time is subtracted from the ring 1 round delay time D, and if this subtraction result is less than half of the ring 1 round delay time D, the ONU 42 is located in the left area, half If it is above, it is specified that it is located in the right area.
By this, the OSU 41 can accurately specify that the ONU to be communicated is located in the right area or the left area.

(2) The OSU 41 assigns the current time of the OSU 41 in the control signal of the downlink signal, and distributes the control signal to which the current time is assigned to all ONUs 42 and 43 that accommodates the OSU 41. The time delayed for the propagation delay time between each ONU 42, 43 is set in each ONU 42, 43, and the reception time in the ONU 42, 43 of the upstream signal from the ONU 42 to be communicated located in the left area is determined. The time obtained by subtracting the round trip delay time from the defined reception time is indicated to the ONU 42 as the upstream signal transmission time in the ONU 42, and the upstream signal transmitted from the ONU 42 is a communication path from the OSU 41 to the ONU 42. Is instructed to be transmitted at wavelength λ2 (first wavelength) via the reverse direction.
By this, the OSU 41 can receive the upstream signals transmitted from the plurality of ONUs 42 located in the left area without collision.

  (3) The OSU 41 assigns the current time of the OSU 41 in the control signal of the downstream signal, and distributes the control signal to which the current time is assigned to all ONUs 42 and 43 that accommodates the OSU 41. The time delayed for the propagation delay time between each ONU 42, 43 is set in each ONU 42, 43, and the reception time of the upstream signal from the ONU 43 to be communicated located in the right area is determined. The time obtained by subtracting the ring one-round delay time D from the determined reception time is indicated to the ONU 43 as the upstream signal transmission time in the ONU 43, and the upstream signal transmitted from the ONU 43 is transmitted from the OSU 41 to the ONU 43. It is instructed to transmit at wavelength λ3 (second wavelength) in the same direction as the signal transmission direction to which the signal is directed.

  By this, the OSU 41 can receive the upstream signals transmitted from the plurality of ONUs 43 located in the right area without collision. At this time, since the ONU 43 in the right region transmits at a wavelength λ3 different from the transmission wavelength λ2 of the ONU 42 located in the left region, it is possible to prevent collision with the upstream signal of the ONU 42 in the left region.

<Configuration of Fourth Embodiment>
FIG. 12 is a block diagram showing the configuration of an ONU and an optical demultiplexing apparatus in an optical concentration network system according to a fourth embodiment of the present invention.
The feature of the fourth embodiment is that the optical demultiplexing devices 36 and 37 connected to the ONUs 42 and 43 shown in FIG. 12 have the configuration of the optical demultiplexing devices 36 and 37 (see FIG. 8) described in the second embodiment. In addition, there is a point that is configured to include the path failure detection unit 36 j and the path wavelength switching control unit 36 k.

The path failure detection unit 36 j detects that a signal interruption failure such as a disconnection occurs in the path of the left area or the right area of the optical fiber 38 as indicated by the crosses of K1 and K2 in FIG. 13.
The ONUs 42 and 43 switch to a wavelength different from the wavelength λ2 or λ3 currently used for the upstream signal if the failure occurrence point is between the paths with the OSU 41 in the own area. The switching of the wavelength is performed by the TS control unit 77.
The path wavelength switching control unit 36k performs control to switch the TX transmission wavelength of the ONUs 42 and 43 to a wavelength λ3 different from the current wavelength (for example, λ2) in accordance with the failure detected by the path failure detection unit 36j.

  For example, as shown in FIG. 13, it is assumed that a failure occurs in the optical fiber 38 as indicated by a symbol K2 in the right area. In this case, the path failure detection unit 36 j detects that a failure has occurred in the path of the right area of the optical fiber 38. The path wavelength switching control unit 36k of the ONU 43 shown in FIG. 12 switches to the wavelength λ2 different from the wavelength λ3 currently used for the upstream signal because the failure occurrence path is between the OSU 41 in its own region (right region).

  By this switching, the wavelength filter 36i switches from the current λ3 to λ2, and operates to transmit the upstream signal of λ2 in the clockwise direction (see FIG. 13) as indicated by the arrow Y12. As a result, the ONU 43 sends an upstream signal to the OSU 41 through the path part of the left area while avoiding the path part of the right area in the failure of the optical fiber 38.

  On the other hand, as shown in FIG. 13, it is assumed that a failure occurs in the optical fiber 38 as indicated by a symbol K1 in the left region. In this case, the path failure detection unit 36 j detects that a failure has occurred in the path of the left area of the optical fiber 38. The path wavelength switching control unit 36k of the ONU 42 shown in FIG. 12 switches to the wavelength λ3 different from the wavelength λ2 currently used for the upstream signal because the failure occurrence location is between the paths with the OSU 41 in its own region (left region).

  By this switching, the wavelength filter 36i switches from the current λ2 to λ3 and operates so that the upstream signal of λ3 is transmitted in the counterclockwise direction (see FIG. 13) as indicated by the arrow Y13. Thereby, the ONU 42 avoids the path portion of the failed left area of the optical fiber 38 and transmits an upstream signal to the OSU 41 so as to pass through the path portion of the right area.

<Effect of Fourth Embodiment>
The system 30 of the fourth embodiment has the following characteristic configuration.
The ONU (for example, 43) has a path failure detection unit 36j as a detection unit that detects that a failure K1 or K2 has occurred in the path of the left area or the right area of the optical fiber 38, and the detected failure generation path is In the right area where the ONU 43 is located, the path wavelength switching control unit 36k as switching control means for switching the wavelength λ3 being used for uplink transmission to a different wavelength λ2 and the upstream signal transmitted with the wavelength λ2 after switching A wavelength filter 36i as a first signal demultiplexing unit for transmitting in the direction (arrow Y13) in the transmission and in the reverse direction (arrow Y12) is provided.
By this, the ONUs 42 and 43 can transmit the upstream signal to the OSU 41 while avoiding the path part of the optical fiber 38 in which the failure has occurred.

<Configuration of Fifth Embodiment>
FIG. 14 is a block diagram showing the configuration of the OSU and the optical demultiplexing apparatus in the light-concentration network system according to the fifth embodiment of the present invention.
The feature of the fifth embodiment is that the wavelength demultiplexing device 35 shown in FIG. 4 is provided with a wavelength filter 35g as shown in FIG. 14 to switch different wavelengths λ1r and λ1l of downstream signals transmitted from the OSU 41 to the ONUs 42 and 43. In that the optical fiber 38 can transmit in the counterclockwise or clockwise direction. The wavelength filter 35g may be provided in the same manner as described above in the optical demultiplexer 35 shown in FIG.

  The wavelength filter 35g switches the transmission direction according to the wavelength of the downstream signal transmitted from the OSU 41. For example, the OSU 41 transmits a wavelength L band λ1r (λ1r) in the counterclockwise direction indicated by the arrow Y11r according to the transmission direction of the downlink signal, and a clockwise direction indicated by the arrow Y11l in the wavelength L band λ1l (λ1l) And a transmission path. The wavelength filter 35g switches the transmission direction of the downstream signal in accordance with the wavelength L band λ1r (λ1r) or the wavelength L band λ1l (λ1l) of the downstream signal transmitted from the OSU 41. For example, when the OSU 41 transmits the wavelength λ1r, it transmits in the counterclockwise direction indicated by the arrow Y11r along a path corresponding to the wavelength λ1r. When the OSU 41 transmits the wavelength λ1ll, it transmits in the clockwise direction indicated by the arrow Y11l along the path corresponding to the wavelength λ1l.

<Effect of Fifth Embodiment>
The system 30 of the fifth embodiment has the following characteristic configuration.
The OSU 41 includes a wavelength filter 35 g as a passive device set to transmit the transmission wavelengths λ1 r and λ1 l of the downstream signal in the left or right direction of the optical fiber 38. The wavelength filter 35g performs an operation of transmitting a signal in the counterclockwise (arrow Y1r) or clockwise (arrow Y11) direction of the ring according to the transmission wavelength λ1r or λ1l of the OSU 41.
As a result, the OSU 41 can transmit the downstream signal to be transmitted to the ONU 42 or 43 counterclockwise (arrow Y1r) or clockwise (arrow Y11) via the wavelength filter 35g. By this, when a failure occurs in the path in either direction, it can be avoided and transmitted to the ONU 42 or 43 to be communicated. Also, the OSU 41 can reduce the downstream transmission delay to the ONU 42 or 43 by transmitting the downstream signal counterclockwise (arrow Y1r) or clockwise (arrow Y1l).

<Configuration of Sixth Embodiment>
FIG. 15 is a block diagram showing the configuration of a light concentration network system according to a sixth embodiment of the present invention.
The characteristic configuration of the sixth embodiment is that the first and second OSUs 41A and 41B are used, and the optical demultiplexer 35A connected to each of the OSUs 41A and 41B is used. However, for the PON application, the first OSU 41A is fixed to transmit the downstream signal in the counterclockwise direction (one direction) in the L band λ11 (λ11) as indicated by the arrow Y31. The second OSU 41 B is fixed so as to transmit the downstream signal in the clockwise direction (the other direction) in the L band λ12 (λ12) of a wavelength different from λ11 as indicated by the arrow Y32. For example, the first OSU 41A is currently used and the second OSU 41B is used as a spare for each of the OSUs 41A and 41B. The ONUs 42 and 43 have the same configuration as that shown in FIG.

  The optical demultiplexing device 35A, as shown in FIG. 16, is configured to have a path failure detection unit 35q and a wavelength selective switch (first wavelength selective switch) 35p connected to the RX of each of the OSUs 41A and 41B. . Alternatively, as shown in FIG. 17, a path failure detection unit 35 q and wavelength selective switches 35 r and 35 l connected to the TXs of the OSUs 41 A and 41 B are provided.

  The path failure detection unit (detection means) 36 j has a failure in the path 38 (L) in the left region or the path 38 (R) in the right region of the optical fiber 38 as indicated by the crosses K1 and K2 in FIG. Detect that.

  The wavelength selective switch 35p illustrated in FIG. 16 performs the following operation when occurrence of a failure K1 of the path 38 (L) is detected while the first OSU 41A is in use and the second OSU 41B is in use as a spare. The wavelength selective switch 35p performs the switching operation of selecting the upstream signal of the C band λ13 (λ13) input to the RX of the first OSU 41A and switching to the RX of the second OSU 41B. At this time, the wavelength selective switch 35p performs the switching operation of selecting the upstream signal of the C band λ14 (λ14) input to the RX of the first OSU 41A and switching to the RX of the second OSU 41B. At this time, an operation of switching the current use of the first OSU 41A to the second OSU 41B is also performed.

By this switching operation, the ONU 42 in the left area shown in FIG. 15 switches the transmission wavelength of the upstream signal from λ13 to λ14, and switches the transmission direction from clockwise (Y33) to counterclockwise (Y34). However, the ONU 43 in the right area does not switch as it is. Further, since the current use is switched to the second OSU 41B, the downstream signal is transmitted in the clockwise direction at λ12 as indicated by the arrow Y32 from the second OSU 41B. As a result, even if the failure K1 of the path 38 (L) occurs, the communication can be continued.
On the other hand, when the first OSU 41A is a spare and the second OSU 41B is a current use, the reverse operation described above is performed, and thus the description thereof is omitted.

  In the optical demultiplexing apparatus 35A shown in FIG. 17, the wavelength selective switches (second wavelength selective switches) 35r and 35l perform switching operation to switch the current downlink signal in the reverse direction. The wavelength selective switch 35r performs the following operation when occurrence of a fault K1 of the path 38 (L) is detected by the path fault detection unit 35q while the first OSU 41A is in use and the second OSU 41B is in use as a spare. The downstream signal of λ11 transmitted from the first OSU 41A counterclockwise (Y31) is switched to the downstream signal transmitted at λ12 clockwise (Y32).

  On the other hand, the wavelength selective switch 35l performs the following operation when the occurrence of the failure K2 of the path 38 (R) is detected while the first OSU 41A is in use as a spare and the second OSU 41B is in use. The downstream signal of λ12 transmitted clockwise (Y32) from the second OSU 41B is switched to the downstream signal transmitted at λ11 counterclockwise (Y31).

  By this switching operation, for example, when occurrence of a fault K1 on the path 38 (L) is detected while the first OSU 41A is in use and the second OSU 41B is being used as a spare, λ11 transmitted from the first OSU 41A to the counterclockwise direction (Y31) The down signal of is switched to the down signal transmitted at λ12 clockwise (Y32). Further, the ONU 42 in the left area where the failure K1 has occurred switches the wavelength of the upstream signal from λ13 to λ14 and switches the signal transmission direction from clockwise (Y33) to counterclockwise (Y34). However, the ONU 43 in the right area is not switched as it is. Therefore, the OSU 41A for current use can continue the signal return operation as it is. The first and second OSUs 41A and 41B shown in FIG. 17 can receive uplink signals of λ13 and λ14 at RX.

<Effect of Sixth Embodiment>
The system 30 of the sixth embodiment has the following characteristic configuration.
(1) The OSU 41 is configured as two units for current use and protection, and downstream signals from the two OSUs 41A and 41B are transmitted to the ONU in mutually opposite directions at different wavelengths. Further, the two OSUs 41A and 41B are a path failure detection unit 36j as a detection unit that detects that a failure has occurred in the path of the left area or the right area of the optical fiber 38, and the uplink to the two OSUs 41A and 41B. And a wavelength selective switch 35p for switching signals. In this configuration, when the path failure detection unit 36j detects that a failure has occurred in the path of the left area or the right area of the optical fiber 38, the wavelength selective switch 35p rotates clockwise or counterclockwise to the current OSU 41A. The upstream signals from the ONUs 42 and 43 input via the switch are switched to be input to the spare OSU 41 B, so that the active OSU 41 A is switched to the spare and the spare OSU 41 B is switched to the active.

  Thus, even if a failure occurs in the ring, communication between ONUs can be continued by the OSU 41A or 41B.

  (2) The OSU 41 is configured as two units for working and protection, and the downstream signals from the two OSUs 41A and 41B are transmitted to the ONU in mutually opposite directions at different wavelengths. Also, the two OSUs 41A and 41B switch the upstream signal to the path fault detection unit 36j that detects that a fault has occurred in the path of the left area or the right area of the optical fiber 38, and the two OSUs 41A and 41B. The wavelength selective switches 35r and 35l are provided. In this configuration, when the currently used OSU 41A detects that the path in the left or right region of the ring has a failure, the wavelength selective switches 35r and 35l are transmitted from the currently used OSU 41A in a predetermined direction at a predetermined wavelength. The downstream signal is switched to be transmitted in the opposite direction to the predetermined direction at a wavelength different from the predetermined wavelength.

  By this, even if a failure occurs in the ring, the current OSU 41A can continue the signal return operation as it is.

  In addition, about a specific structure, it can change suitably in the range which does not deviate from the main point of this invention.

Reference Signs List 30 optical concentration network system 31, 32, 33 optical transmission device 35, 36, 37 optical demultiplexing device 38 optical fiber 41, 41A, 41B OSU
42, 43 ONU
45, 46, 47 External device 51 Buffer unit 52 Optical burst reception unit 53 Optical signal reception unit 54 MUX unit 55 Signal separation unit 56 Control information reception unit 57 Delay measurement unit 58 Path determination unit 59 Internal clock unit 60 Counter management unit 61 TS Control unit 62 Optical transmission unit 71 Buffer unit 72 Optical reception unit 73 Signal separation unit 74 Control information reception unit 75 Internal clock unit 76 Counter management unit 77 TS control unit 78 Optical burst transmission unit 35a, 35b, 36a, 36b Band separation filter 35c , 36f, 36h, 36h 1 Optical coupler (signal demultiplexing unit)
35e wavelength filters 35g, 36c, 36d, 36e, 36i wavelength filters (signal demultiplexing unit)
35q, 36j Path failure detection unit 36k Path wavelength switching control unit

Claims (14)

An OSU as an optical line termination device that terminates signals transmitted to and received from an external device, and a control subject, and a plurality of ONUs as optical line termination devices that become objects to the control subject An optical concentration network system in which the OSU transmits a downstream signal to the ONU to the ring and the ONU transmits an upstream signal to the OSU to the ring;
The ONU is
When the downstream signal from the OSU is located in the first area requiring a time less than half of the ring 1 round delay time to return to the OSU via the ring, the upstream signal transmitted from the ONU to the OSU is A first signal demultiplexing unit for transmitting in the direction opposite to the transmission direction of the downlink signal;
When the OSU is located in a second area requiring half or more of the ring one-round delay time, an upstream signal transmitted from the ONU to the OSU is transmitted in the same direction as the downstream signal transmission direction. A light concentration network system comprising a second signal demultiplexing unit. An OSU as an optical line termination device that terminates signals transmitted to and received from an external device, and a control subject, and a plurality of ONUs as optical line termination devices that become objects to the control subject In the configuration in which the ring is connected in a ring, the OSU always returns at the time of communication between the ONUs and transmits it to the other ONU, and the OSU transmits downstream signals to the ONU only in one direction of the ring. Optical concentration network system,
The ONU is
Uplink transmitted from the ONU through the ring when the downlink signal from the OSU is located in a first area requiring a time less than half of a ring 1 round delay time to return to the OSU through the ring A first signal demultiplexing unit that transmits a signal in the direction opposite to the transmission direction of the downstream signal;
When the OSU is located in the second area requiring half or more of the ring one-round delay time, the upstream signal transmitted from the ONU via the ring is in the same direction as the downstream signal transmission direction. A light concentration network system comprising a second signal demultiplexing unit for transmitting. The OSU is
The ring one-round delay time is measured and held, and one path is selected for the path from the OSU to the ONU, and the first round of the ring where the first delay time, which is the delay time of the path, is held If the delay time is less than half, the ONU is set as the first area and the upstream signal from the ONU is transmitted to the ONU in the opposite direction to the transmission direction of the downstream signal.
If the first delay time is equal to or more than half of the held ring one round delay time, the position of the ONU is identified as the second region, and the upstream signal from the ONU is the transmission direction of the downstream signal. The optical concentration network system according to claim 1 or 2, wherein setting for transmitting in the same direction is performed to the ONU. The OSU is
A wavelength setting unit is provided which assigns a first wavelength to the transmission wavelength of the ONU located in the first area, and assigns a second wavelength of a wavelength different from the first wavelength to the transmission wavelength of the ONU located in the second area ,
The optical concentration network system according to claim 1 or 2, wherein any one of signals of different wavelengths including the first and second wavelengths assigned by the wavelength setting means is transmitted. The OSU is
The round trip delay time due to the round trip signal transmission between the communication path from the OSU to the ONU and the communication path heading in the reverse direction of the communication path is calculated with the ONU to be communicated, and the calculated round trip time If the value of 1⁄2 is less than half of the ring 1 round delay time, the ONU is located in the first area, and if it is more than half, the ONU is identified as being located in the second area. The light concentration network system according to claim 3. The OSU is
The propagation delay time between the OSU and each ONU is given by assigning the current time of the OSU in the control signal of the downstream signal and distributing the control signal to which the current time is assigned to all ONUs that accommodate the control signal. The time delayed by a minute is set in each ONU, and the reception time in the OSU of the upstream signal from the communication target ONU located in the first area is determined, and the OSU and the ONU are reciprocated from the determined reception time The time obtained by subtracting the delay time is indicated to the ONU as the upstream signal transmission time in the ONU, and the upstream signal transmitted from the ONU passes the communication path from the OSU to the ONU in the reverse direction. To be transmitted at the first wavelength,
The reception time in the OSU of the upstream signal from the ONU for communication located in the second area is determined, and the time obtained by subtracting the ring one-round delay time from the determined reception time is the upstream in the ONU While instructing the ONU as a signal transmission time, an upstream signal transmitted from the ONU is transmitted at a second wavelength different from the first wavelength in the same direction as the signal transmission direction from the OSU toward the ONU The light concentration network system according to claim 1 or 2, wherein: The ONU is
A detection means for detecting that a failure has occurred in the path of the first area or the second area of the ring, and a wavelength in use for upstream transmission if the detected failure path is the area where the ONU is located And a first signal demultiplexing unit for transmitting an upstream signal transmitted at the wavelength after the switching in a direction opposite to the direction during transmission. The light concentration network system according to 1 or 2. The OSU is
And a signal demultiplexing unit configured to transmit the transmission wavelength of the downlink signal in the left or right direction of the ring,
The signal demultiplexing unit performs an operation of transmitting a signal in a counterclockwise direction or a clockwise direction of the ring according to the transmission wavelength of the OSU. Optical concentration network system. The two OSUs are configured to transmit the downstream signals from the two OSUs in mutually opposite directions to the ONU in different wavelengths, respectively, with the current OS and the spare two, and the two OSUs are the first area of the ring or the first area of the ring or And a first wavelength selection switch that switches upstream signals to the two OSUs.
When the detection unit detects that a failure has occurred in the path of the first area or the second area of the ring, the current OSU rotates clockwise to the current OSU by the first wavelength selective switch. And switching so that an upstream signal from the ONU, which is input via a counterclockwise direction, is input to the spare OSU, and switching the current OSU to a spare and the spare OSU to a current. The optical concentration network system according to claim 1 or 2. The two OSUs are configured to transmit the downstream signals from the two OSUs in mutually opposite directions to the ONU in different wavelengths, respectively, with the current OS and the spare two, and the two OSUs are the first area of the ring or the first area of the ring or A detection unit that detects occurrence of a failure in the path of the second area; and a second wavelength selection switch that switches the transmission direction of downstream signals from the two OSUs;
When the detection means detects that a failure has occurred in the path of the first region or the second region of the ring, the current OSU is controlled by the second wavelength selective switch to a predetermined wavelength from the current OSU The light-concentrating network system according to claim 1 or 2, wherein a downstream signal transmitted in a predetermined direction is switched to be transmitted in a direction opposite to the predetermined direction at a wavelength different from the predetermined wavelength. It terminates the signal transmitted / received to / from the external device, and is annularly connected with the ring by the optical transmission path together with the upper optical transmission device as the optical line termination device as the control subject, and becomes an object to the control subject A plurality of subordinate optical transmission devices as optical line termination devices, wherein
The lower light is required to be in the first region that requires less than half of the ring one-round delay time for the downstream signal transmitted from the upper optical transmission device to the ring to travel around the ring and return to the upper optical transmission device When the transmission apparatus is located, the upstream signal transmitted to the ring from the lower optical transmission apparatus is transmitted in the direction opposite to the transmission direction of the downstream signal;
When the subordinate optical transmission apparatus is located in the second area, which requires a half or more of the ring one-round delay time from the superior optical transmission apparatus, the upstream signal is in the same direction as the downstream signal transmission direction. An optical transmission apparatus characterized by transmitting to. It terminates the signal transmitted / received to / from the external device, and is annularly connected with the ring by the optical transmission path together with the upper optical transmission device as the optical line termination device as the control subject, and becomes an object to the control subject An optical transmission method using a plurality of subordinate optical transmission devices as an optical line termination device, comprising:
The subordinate optical transmission device is
When the downstream signal transmitted to the ring from the upper level optical transmission apparatus is located in the first area which requires less than half the ring one-round delay time to travel around the ring and return to the upper level optical transmission apparatus Transmitting an upstream signal transmitted from the subordinate optical transmission apparatus to the ring in a direction opposite to the transmission direction of the downstream signal;
Transmitting the upstream signal in the same direction as the downstream signal transmission direction, when the upstream optical transmission apparatus is located in the second area requiring half or more of the ring one-round delay time An optical transmission method characterized by: An upper optical transmission apparatus as an optical line termination apparatus that terminates signals transmitted to and received from an external apparatus as a control subject, and a plurality of lower levels as optical line termination apparatuses that become objects with respect to the control subject An optical transmission apparatus for transmitting a downstream signal to the subordinate optical transmission apparatus via the ring in a configuration in which the optical transmission apparatus is connected in a ring by an optical transmission path;
The downstream signal transmitted from the upper level optical transmission apparatus travels around the ring and measures the ring one-round delay time to return to the upper level optical transmission apparatus, and holds the ring from the upper level optical transmission apparatus If the first delay time, which is the delay time of one of the two paths to the subordinate optical transmission device, is less than half of the held ring round circumference delay time, the subordinate optical transmission device Position is identified as the first area, and the upstream signal transmitted to the ring from the subordinate optical transmission device located in the identified first area is received from the reverse direction to the downstream signal transmission direction,
If the first delay time is half or more of the held ring one round delay time, the position of the subordinate optical transmission apparatus is identified as the second area requiring the half or more time, and the identified first An optical transmission apparatus characterized in that the upstream signal from a lower-order optical transmission apparatus located in two areas is received from the same direction as the transmission direction of the downstream signal. An upper optical transmission apparatus as an optical line termination apparatus that terminates signals transmitted to and received from an external apparatus as a control subject, and a plurality of lower levels as optical line termination apparatuses that become objects with respect to the control subject An optical transmission method by a higher-order optical transmission apparatus for transmitting a downstream signal to the lower-order optical transmission apparatus via the ring in a configuration in which the optical transmission apparatus is annularly connected by a ring by an optical transmission path,
The upper level optical transmission device is
Measuring and holding a ring one-round delay time in which the downstream signal transmitted from the higher-order optical transmission device travels around the ring and returns to the higher-order optical transmission device;
A first delay time, which is a delay time of one of two paths from the upper optical transmission apparatus to the lower optical transmission apparatus via the ring, is less than half of the held ring one-round delay time If the position of the subordinate optical transmission apparatus is identified as the first area;
Receiving an upstream signal transmitted to the ring from a lower-order optical transmission apparatus located in the specified first area from the direction opposite to the downstream signal transmission direction;
If the first delay time is equal to or more than half of the held ring one-round delay time, the position of the subordinate optical transmission apparatus is specified as the second area requiring the half or more time;
And D. receiving the upstream signal from the lower-level optical transmission apparatus located in the specified second area from the same direction as the downstream signal transmission direction.

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