JP2011223407A - Optical communication system and optical communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical communication system and an optical communication method which can freely change a wavelength, a path, or their combination for an upstream signal and a downstream signal and avoid a collision of upstream signals.SOLUTION: In switching a wavelength of an upstream signal or a downstream signal, an Optional Line Terminal (OLT) 200 transmits a gate message GM including a time stamp t1 of the time to which optical transmitting and receiving devices (21 and 22) add a propagation delay difference Δ generated between an Optical Network Unit (ONU) 100A and each of the transmitting and receiving devices (21 and 22) to the time of the OLT 200, a transmission starting time t2 in which an upstream signal of the ONU 100A is permitted, and a transmission available duration time K of the upstream signal of the ONU 100A. In this case, the ONU 100A sets the time of the ONU 100A to the time stamp of the gate message GM when receiving the gate message GM from the OLT 200, and transmits an upstream signal from the transmission starting time t2 included in the gate message GM for the transmission available duration time K included in the gate message GM.

Description

  The present invention relates to an optical communication system and an optical communication method in which a wavelength, a route, or a combination route thereof is different for each facing.

  In recent years, the demand for large-capacity communication has increased against the background of the rapid growth of the Internet and Intranet, and a system for realizing an economical high-speed optical access network is being promoted at a rapid pace. For example, PON (Passive Optical Network) is known. In addition, many proposals have been made on an optical access network including an optical switch instead of a passive element (such as an optical splitter) used for the PON (see, for example, Non-Patent Document 3).

  Assuming that time division multiplexing (TDM) technology is applied to the above-mentioned optical access network using an inexpensive SiGe-BiCMOS process conventionally used in high-speed optical access networks and intensity modulation-direct detection. The upper limit is considered to be 10 Gbit / s due to restrictions of electronic devices.

  In view of this, proposals have been made to realize further higher speed / broadband by applying wavelength division multiplexing (WDM) and core line multiplexing. However, when WDM using different wavelengths for each user is applied, an optical transmitter / receiver corresponding to the number of ONUs (Optical Network Units) serving as subscriber-side devices is required for the OLT (Optical Line Terminal) serving as a station-side device. Become. This requires renewal of existing ONUs and OLTs, resulting in a problem of increased costs. In addition, the core multiplexing also requires a light transmitter / receiver and a route for the core wire that is a route, which causes a problem of cost increase.

  In response to this problem, WDM / TDM-PON (for example, Non-Patent Document 1), in which ONUs are grouped into a plurality of groups instead of using different wavelengths for each ONU, and WDM is applied between the groups and TDM is applied within the group. See). This suppresses an increase in cost due to the total bandwidth expansion by sharing the wavelength among a plurality of ONUs.

  There is a method (for example, see Non-Patent Document 2) in which a spare core wire for a redundant configuration is used as an active core wire instead of providing a new core wire and a transceiver for total bandwidth extension. This method solves the problem of cost increase due to the addition of a core wire and a transmitter / receiver accompanying the expansion of the total bandwidth by utilizing a redundant core wire.

"A proposal for total bandwidth extension WDM / TDM-PON and dynamic wavelength band allocation", Manabu Yoshino, Kazutaka Hara, Hirotaka Nakamura, Shunji Kimura, Naoto Yoshimoto, Kiyomi Kunzaki, 2009 IEICE General Conference , Proceedings of Communication, Communication (2), p. 426, B-10-107 "Examination of ATM-PON protection method and dynamic bandwidth allocation", Toshikazu Yoshida, Hiroaki Mukai, Mitsuka Iwasaki, Yoshihiro Asashiba, Hiroshi Ichibanse, Tetsuya Yokoya, May 2001 IEICE Technical Report vol. 101 (53): CS2001-21, pp. 25-30 "Proposal of efficient discovery method in access network using optical packet switch", Hiroaki Ueda, Toshinori Tsuboi, Hiroyuki Kawanishi, April 2009 Communication Society of Japan, IEICE Technical Report Vol. 109 (4): CS2009-12, pp. 69-74

  In an optical access network including a configuration using the PON system described in Non-Patent Document 1 and Non-Patent Document 2 and the optical switch of Non-Patent Document 3, when multiplexing WDM or core lines, inter-wavelength, inter-core lines, or a combination thereof It is desirable to equalize the traffic in the upstream and downstream directions. However, no means has been established for notifying an ONU that receives an arbitrary downstream wavelength, route, or a combination thereof, of a transmission permission for transmission using an arbitrary upstream wavelength, route, or a combination thereof.

  In particular, when only one of the uplink, the downlink, and the wavelength, the route, or the combination thereof is switched, it is described in the transmission permission that arrives from the OLT to the ONU due to the propagation delay difference due to the wavelength dispersion, the route length, or the combination. The time in the OLT meaning the transmission time of the same value or the time in the OLT meaning the value of the transmission start time notified by the OLT changes, and the transmission permission notified by the OLT is not correctly transmitted.

  The following description will be made using a general uplink transmission permission shown in IEEE 802.3 and a discovery operation performed in the preceding stage.

  In the discovery operation, an unregistered ONU is assigned an identification number LLID (Logical Link ID) necessary for frame selection, and a round trip time RTT (Round Trip Time) between the OLT and the ONU of the ONU newly connected to the OLT. Measure. This process is included in the MPCP (Multi-Point Control Protocol) protocol. The OLT periodically transmits a discovery gate message (Discovery_GATE Message) to the ONU so that the ONU may be newly connected to the PON. The discovery gate message is a kind of gate message (GATE Message) for notifying the time when transmission is possible, the transmission time t1 of the message, the transmission start time t2 permitting transmission, and the length of the discovery time window (Discovery Time Window) S is shown. The unregistered ONU that has received the discovery gate message sets its clock to the transmission time t1 of the message indicated by the time stamp of this message. ONU adds transmission start time t2 * (= t2 + d) by adding random time d (0 ≦ d ≦ D, D: maximum value of random time) to transmission start time t2 instructed by the discovery gate message in order to avoid an uplink collision. In response to a register request message (Register_REQ Message) whose time stamp is t2 *. The register request message indicates the MAC address of the ONU. The OLT measures the arrival time t3 of the received register request message, obtains t2 * from the time stamp, and obtains a round trip time Tx (= t3-t2 *) to the ONU. The OLT determines the LLID and notifies the ONU of the LLID through a register message (Register Message).

  The OLT notifies the ONU of the next uplink timing by a gate message (GATE Message) designated by the LLID. The gate message includes a transmission time t1 of the gate message, a transmission start time t2 at which communication is permitted, and a transmission permission duration time K. The ONU that has received the gate message sets its clock to the transmission time t1 of the message indicated by the time stamp of the message. The ONU responds with a register Ack message (Register ACK Message) from the transmission start time t2 indicated by the gate message until the continuation time K elapses. This completes the discovery process.

  The upstream signal permission is notified to the ONU by a gate message based on the upstream accumulated data amount of the ONU, the upstream usage band, and the like ascertained by the OLT by the report message (Report Message) from the ONU. The gate message includes a transmission time t1 of the gate message, a transmission start time t2 at which communication is permitted, and a transmission permission duration time K. The ONU that has received the gate message sets its clock to the transmission time t1 of the message indicated by the time stamp of the message. The ONU transmits an uplink signal from the transmission start time t2 until the continuation time K elapses.

  As is clear from this procedure, the transmission time t1 recognized by the ONU is a time obtained by adding a one-way propagation delay time to the transmission time t1 in the OLT. Therefore, when the propagation time of the downlink signal varies, the time in the OLT at the transmission time t1 recognized by the ONU differs. The same applies even if the propagation time of the upstream signal varies. Therefore, the OLT may not be able to receive an upstream signal at the time indicated in the gate message transmission permission.

  Therefore, the present invention can freely switch the wavelength, the route, or a combination thereof between the upstream signal and the downstream signal, and switches the wavelength, the route, or a combination thereof in the upstream signal or the downstream signal. An object of the present invention is to provide an optical communication system and an optical communication method capable of correcting a change in propagation delay and avoiding an uplink signal collision.

  In order to achieve the above object, the optical communication system and the optical communication method according to the present invention, when changing the wavelength, route, or combination of downlink signals, transmit an increase in propagation delay associated with the change to transmit a gate message. The time added to the time t1 is t1, or the time obtained by subtracting the propagation delay increase from the transmission start time t2 is t2. Further, in the optical communication system and the optical communication method according to the present invention, when the wavelength of the upstream signal, the route, or the combination thereof is changed, the time when the propagation delay increase accompanying the change is added to the transmission time t1 of the gate message Is set to t1, or the time subtracted from the transmission start time t2 at which transmission is permitted is set to t2.

  Specifically, an optical communication system according to the present invention includes a station side apparatus (OLT: Optical Line Terminal) having at least two optical transceivers having different wavelengths, paths, or combinations of wavelengths and paths, and the OLT. A plurality of optical signals transmitted to and received from the OLT by wavelength division multiplexing and time division multiplexing, core line multiplexing and time division multiplexing, or wavelength division multiplexing, core line multiplexing and time division multiplexing. An optical network unit (ONU), and when the OLT switches the wavelength of an upstream signal or a downstream signal, a path, or a combination of a wavelength and a path, the one optical transceiver The transmission permission when the ONU is notified of permission to transmit to another optical transceiver different from the optical transceiver having a propagation delay with the ONU. A time obtained by adding a propagation delay difference obtained by subtracting a propagation delay between the ONU and the one optical transceiver from a propagation delay between the ONU and the other optical transceiver to the current time of the one optical transceiver; It includes a transmission start time that permits transmission of an upstream signal from the ONU and a duration that permits transmission of the upstream signal from the ONU. Alternatively, the current time of the one optical transceiver is permitted to transmit the upstream signal from the ONU. A transmission delay time obtained by subtracting a propagation delay difference between the ONU and one optical transceiver from a propagation delay between the ONU and another optical transceiver from the transmission start time, and an upstream signal of the ONU The ONU, when receiving the transmission permission from the OLT, adjusts the time of its own device to the current time included in the transmission permission and starts the transmission included in the transmission permission. An upstream signal is transmitted to another optical transceiver at the time, and the upstream signal is transmitted to the one optical transceiver after the propagation delay difference has elapsed at the transmission start time and until the duration included in the transmission permission. Is transmitted.

  In the optical communication system according to the present invention, in the optical communication system, when switching the wavelength, route, or combination of wavelength and route of an upstream signal or downstream signal, propagation from one optical transceiver to the ONU is performed. When the OLT notifies the ONU of transmission permission to another optical transmitter / receiver that is different from the optical transmitter / receiver having one delay, the transmission permission is transmitted to the ONU at the current time of the one optical transmitter / receiver. A time obtained by adding a propagation delay difference obtained by subtracting a propagation delay between the ONU and the one optical transceiver from a propagation delay with the other optical transceiver, a transmission start time for permitting transmission of an upstream signal of the ONU, and The ONU and another optical transceiver including a duration time permitting transmission of the upstream signal of the ONU, or from a current start time of the one optical transceiver and a transmission start time permitting transmission of the upstream signal of the ONU When The transmission permission from the OLT, including a time obtained by subtracting a propagation delay difference obtained by subtracting a propagation delay between the ONU and the one optical transceiver from a propagation delay, and a duration for allowing transmission of the upstream signal of the ONU. The time of the ONU is adjusted to the current time included in the transmission permission when an ON signal is received, and an upstream signal is transmitted from the ONU to another optical transceiver at the transmission start time included in the transmission permission, and the transmission An upstream signal is transmitted from the ONU to the one optical transceiver after the propagation delay difference has elapsed at the start time and until the duration included in the transmission permission.

  Another optical communication system according to the present invention includes an optical line terminal (OLT) having at least two optical transceivers having different wavelengths, paths, or combinations of wavelengths and paths, and optical transmission to the OLT. A plurality of subscribers that are connected via a path and transmit / receive optical signals to / from the OLT by wavelength division multiplexing and time division multiplexing, core line multiplexing and time division multiplexing, or wavelength division multiplexing, core line multiplexing, and time division multiplexing A device (ONU: Optical Network Unit), and when the OLT switches the wavelength of an upstream signal or a downstream signal, a route, or a combination of a wavelength and a route, a plurality of the optical transceivers When notifying the ONU of permission to transmit to the one optical transceiver having a propagation delay with the ONU different from that of the other optical transceiver, the other optical transceiver The transmission permission is obtained by subtracting the propagation delay between the ONU and the one optical transceiver from the propagation delay between the ONU and the other optical transceiver at the current time of the other optical transceiver. , A transmission start time that permits transmission of the upstream signal of the ONU, and a duration that permits transmission of the upstream signal of the ONU, or the current time of the other optical transceiver, A time obtained by subtracting a propagation delay difference obtained by subtracting a propagation delay between the ONU and one optical transceiver from a propagation delay between the ONU and another optical transceiver from a transmission start time at which transmission of an upstream signal is permitted; and The ONU includes a duration for allowing transmission of an upstream signal from the ONU, and when the ONU receives the transmission permission from the OLT, adjusts the time of its own device to the current time included in the transmission permission, and transmits the transmission permission. Included in The uplink signal is transmitted to one optical transceiver between the transmission start time and the duration included in the transmission permission.

  In the optical communication method according to the present invention, in the other optical communication system, when switching the wavelength, the route, or the combination of the wavelength and the route of the uplink signal or the downlink signal, the ONU When the OLT notifies the ONU of transmission permission to the one optical transceiver that has a propagation delay different from that of the other optical transceiver, the transmission permission from the other optical transceiver A time obtained by adding a propagation delay difference obtained by subtracting a propagation delay between the ONU and the one optical transceiver from the propagation delay between the ONU and the other optical transceiver at the current time of the optical transceiver; Including a transmission start time permitting transmission of the ONU and a duration time permitting transmission of the upstream signal of the ONU, or a current time of the other optical transceiver, and a transmission start time permitting transmission of the upstream signal of the ONU Before A time obtained by subtracting a propagation delay difference obtained by subtracting a propagation delay between the ONU and one optical transceiver from a propagation delay between the ONU and the other optical transceiver, and a duration time during which transmission of the upstream signal of the ONU is permitted. The ONU time is matched with the current time included in the transmission permission when the transmission permission from the OLT is received, and the continuation included in the transmission permission from the transmission start time included in the transmission permission. An upstream signal is transmitted from the ONU to one of the optical transceivers until time.

  The present optical communication system and the present optical communication method increase or decrease the time transmitted by the gate message according to the increase or decrease of the propagation delay difference of the uplink signal or the downlink signal due to the switching of the wavelength, the route, or the combination thereof. The incoming time can be made constant. For this reason, this optical communication system and this optical communication method can notify the transmission permission to transmit at an arbitrary upstream wavelength to an ONU that receives an arbitrary downstream wavelength.

  Therefore, the present invention can provide an optical communication system and an optical communication method that can freely change the wavelength, the route, or the combination thereof between the upstream signal and the downstream signal and can avoid the collision of the upstream signal.

  The present invention can freely switch a wavelength, a route, or a combination thereof between an upstream signal and a downstream signal, and a propagation delay when switching a wavelength, a route, or a combination thereof in the upstream signal or the downstream signal. Thus, it is possible to provide an optical communication system and an optical communication method that can correct the change of the signal and avoid the collision of the uplink signals.

1 is a block diagram illustrating an optical communication system according to the present invention. It is a time diagram explaining the optical communication method which concerns on this invention. It is a time diagram explaining the optical communication method which concerns on this invention. It is a time diagram explaining the optical communication method which concerns on this invention. It is a time diagram explaining the optical communication method which concerns on this invention. 1 is a block diagram illustrating an optical communication system according to the present invention. (A) is an example of the increase in the downlink delay of the uplink transmission permission performed by the optical communication system according to the present invention. (B) is an example of the downlink delay reduction of the uplink transmission permission performed by the optical communication system according to the present invention. (C) is an example of an increase in uplink delay of uplink transmission permission performed by the optical communication system according to the present invention. (D) is an example of the uplink delay reduction of the uplink transmission permission performed by the optical communication system according to the present invention.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
FIG. 1 is a conceptual diagram illustrating an optical communication system 301 according to the first embodiment. An optical communication system 301 includes an OLT 200 having optical transceivers (21, 22) that transmit and receive different wavelengths, and an optical distribution network (ODN) ODN50 that is an optical transmission path to the optical transceivers (21, 22). And wavelength division multiplexing using a plurality of wavelengths with the OLT 200 (for example, the downstream direction from the OLT to the ONU is λ1, λ2, the upstream direction from the ONU to the OLT is λ1 ′, λ2 ′) and A plurality of ONUs (100A, 100B, 100C) having optical transceivers for transmitting and receiving optical signals by time division multiplexing. The optical communication system 301 is, for example, a PON, and transmits an optical signal by wavelength division multiplexing and time division multiplexing.

  As wavelengths used for wavelength division multiplexing, for example, downstream wavelengths are 1574.54 nm, 1576.20 nm, 1577.86 nm, 1579.52 nm, and upstream wavelengths are 1270 nm, 1290 nm, 1310 nm, and 1330 nm.

  The ONU (100A, 100B, 100C) is installed in each subscriber's house, and the optical transmitter / receiver of each ONU outputs signal light of the assigned wavelength for use in the uplink signal to be transmitted. The assigned wavelength is one of a plurality of selectable wavelengths.

  The ODN 50 combines the signal light from the optical transceivers of each ONU and couples them to the optical transceivers (21, 22) of the OLT 200, and branches the signal light from the optical transceivers (21, 22) of the OLT 200 to each of them. Coupled to ONU optical transceiver. Here, when the upstream signal light output from the optical transceiver of each ONU arrives at the OLT 200 at the same wavelength that is received as the same wavelength, it cannot be received, so the OLT 200 transmits the propagation time at that wavelength of the optical transceiver of each ONU. In consideration of the difference, signal lights that receive the same wavelength are permitted to be transmitted by the optical transceivers (21, 22) of the OLT 200. The transmission permission is notified from the OLT 200 at the wavelength being received by the optical transceiver on each ONU side. The wavelength being received is one of a plurality of wavelengths that can be selected as a wavelength received by the ONU.

  The OLT 200 demultiplexes the light from the ODN 50 for each wavelength, multiplexes the light from the optical transceivers (21, 22) and delivers it to the ODN 50, and demultiplexes from the optical multiplexer / demultiplexer 25. A plurality of optical transceivers (21, 22) for receiving the received signal light and outputting them as electrical signals. For example, a wavelength filter can be applied to the optical multiplexer / demultiplexer 25. For example, a photodiode can be used as the light receiving unit of the optical transceiver (21, 22).

  Here, if the wavelength applied to simplify the talk is assumed to be two wavelengths for the upstream and downstream, the optical multiplexer / demultiplexer 25 separates the upstream signal light from the ONU via the ODN 50 into the wavelength λ1 ′ and the wavelength λ2 ′. Waves are respectively coupled to the optical transceivers (21, 22). Each of the optical transceivers (21, 22) outputs the received signal light as an electrical signal. Therefore, the OLT 200 can receive signal light for each wavelength (λ1 ′, λ2 ′). The optical transceivers (21, 22) output downstream signal lights having wavelengths λ1 and λ2, respectively, are combined by the optical multiplexer / demultiplexer 25, and are coupled to the ONU via the ODN 50.

  FIG. 7 is an example of uplink transmission permission performed by the optical communication system 301.

  The characteristic of the optical communication system 301 is that, when changing the wavelength of the downlink signal, the time obtained by adding the propagation delay increase accompanying the change to the transmission time t1 of the gate message is t1, or the propagation delay increase is the transmission start time t2. The time subtracted from t is t2. Further, when changing the wavelength of the uplink signal, the time obtained by adding the propagation delay increase accompanying the change to the transmission time t1 of the gate message is set to t1, or the time subtracted from the transmission start time t2 that permits transmission is set to t2. To do. That is, the same processing is performed for the increase in the propagation delay of the uplink signal and the increase in the propagation delay of the downlink signal.

  In the following, since the case of two wavelengths is shown, an example in which the propagation delay of one of the uplink signal and the downlink signal is changed is shown, but when both the uplink signal and the downlink signal are changed, a combination thereof may be used.

  First, an example of an increase in downlink delay is shown in FIG. The horizontal arrow in the figure indicates the time at the ONU, where t1 = 0, t2 = 100, and propagation delay increase Δ = 10. “K” in the figure is a transmission continuation time. In the conventional example, due to an increase in propagation delay, a time later by the propagation delay increase Δ than before switching is mistaken as t1 and t2 before switching. For this reason, the time 110 later than the original transmission start time t2 (= 100) assumed by the OLT by the propagation delay increase Δ is treated as 100. For this reason, the transmission start time is delayed by 10.

  On the other hand, the optical communication system 301 sets the time when the propagation delay increase Δ is added to the transmission time t1 of the gate message as the method 1 as t1. That is, t1 + Δ = 0 + 10 = 10 is transmitted as t1. By delaying the time of the transmission time t1 by the delay of the gate message accompanying the increase in propagation delay, the transmission starts similarly to before the switching.

  The optical communication system 301 sets the time when the propagation delay increase Δ is subtracted from the transmission start time t2 as method 2 as t2. That is, t2−Δ = 100−10 = 90 is transmitted as t2. By advancing the transmission start time t2 by the gate message delay accompanying the increase in propagation delay, the transmission starts similarly to before the switching.

  Next, an example of downlink delay reduction is shown in FIG. Since it is a decrease, if the increase is set to a negative value, it is the same as the increase example. The propagation delay increase Δ = −10. Other than that, it is the same as the example of the delay increase. In the conventional example, due to a decrease in propagation delay, a time later by the propagation delay increase Δ than before the switching (a time earlier by the propagation delay decrease −Δ) is mistaken as t1 and t2 before the switching. For this reason, the time 90 later by the propagation delay increase Δ than the original transmission start time t2 assumed by the OLT is treated as 100 (the time 90 earlier by the propagation delay decrease −Δ is 100). For this reason, the transmission start time is delayed by −10 (by 10 earlier).

  On the other hand, the optical communication system 301 sets the time when the propagation delay increase Δ is added to the transmission time t1 of the gate message as the method 1 as t1. That is, t1 + Δ = 0 + (− 10) = − 10 is transmitted as t1 (the propagation delay decrease −Δ is subtracted from the gate message transmission time t1 as t1, that is, t1 − (− Δ) = 0− ( 10) =-10 is transmitted as t1). By delaying the time of transmission time t1 by the amount of delay of the gate message accompanying the increase in propagation delay (advancing the time of transmission time t1 by the amount of advance of the gate message accompanying reduction of propagation delay), Become.

  The optical communication system 301 sets the time when the propagation delay increase Δ is subtracted from the transmission start time t2 as method 2 as t2. That is, t2−Δ = 100 − (− 10) = 110 is transmitted as t2 (the time obtained by adding the propagation delay decrease −Δ to the transmission start time t2 is t2. That is, t2 + (− Δ) = 100 + (10). = 110 is transmitted as t2.) Transmission similar to that before switching by advancing the time of transmission start time t2 by the amount of delay of the gate message accompanying the increase in propagation delay (delaying the time of transmission start time t2 by the amount of advance of the gate message accompanying reduction of propagation delay) It will start.

  Next, an example of an increase in uplink delay is shown in FIG. The horizontal arrow in the figure is the time at the OLT, and the other points are the same as in the downlink example. It is assumed that t1 = 0, t2 = 100, and propagation delay increase Δ = 10. In the conventional example, due to an increase in propagation delay, arrival is delayed by a propagation delay increase Δ compared to before switching. For this reason, it arrives at a time 110 later than the original arrival time t2 (= 100) assumed by the OLT by a propagation delay increase Δ.

  On the other hand, the optical communication system 301 sets the time when the propagation delay increase Δ is added to the transmission time t1 of the gate message as the method 1 as t1. That is, t1 + Δ = 0 + 10 = 10 is transmitted as t1. By delaying the time of transmission time t1 by the amount of delay of the uplink signal accompanying the increase in propagation delay, shortening the time from transmission time t1 to transmission start time t2, and increasing the transmission start time by the amount of increase in propagation delay, before switching It will be the same arrival time.

  The optical communication system 301 sets the time when the propagation delay increase Δ is subtracted from the transmission start time t2 as method 2 as t2. That is, t2−Δ = 100−10 = 90 is transmitted as t2. Same as before switching by advancing the transmission start time t2 by the amount of delay of the uplink signal due to the increase of the propagation delay, shortening the time from the transmission time t1 to the transmission start time t2 and advancing the transmission start time by the increase of the propagation delay It will be the arrival time.

  Next, an example of uplink delay reduction is shown in FIG. Since it is a decrease, if the increase is a negative value, it is the same as the increase example. The propagation delay increase Δ = −10. Other than that, it is the same as the example of the delay increase. In the conventional example, due to the decrease in the propagation delay, the arrival is delayed by the propagation delay increase Δ compared to before the switching (the arrival is advanced by the propagation delay decrease −Δ). For this reason, it arrives at time 90 later than the original arrival time t2 (= 100) assumed by the OLT by the propagation delay increase Δ (arrival at time 90 earlier by the propagation delay decrease −Δ). This delays the arrival time by -10 (by 10 earlier).

  On the other hand, the optical communication system 301 sets the time when the propagation delay increase Δ is added to the transmission time t1 of the gate message as the method 1 as t1. That is, t1 + Δ = 0 + (− 10) = − 10 is transmitted as t1 (the propagation delay decrease −Δ is subtracted from the gate message transmission time t1 as t1, that is, t1 − (− Δ) = 0− ( 10) =-10 is transmitted as t1). The time of transmission time t1 is delayed by the amount of delay of the upstream signal accompanying the increase in propagation delay (the time of transmission time t1 is advanced by the amount of early time of the upstream signal accompanying decrease of propagation delay), and from transmission time t1 to transmission start time t2. By shortening the time and accelerating the transmission start time by the propagation delay increase (by increasing the time from the transmission time t1 to the transmission start time t2 and delaying the transmission start time by the propagation delay decrease), the same as before switching It will be the arrival time.

  The optical communication system 301 sets the time when the propagation delay increase Δ is subtracted from the transmission start time t2 as method 2 as t2. That is, t2−Δ = 100 − (− 10) = 110 is transmitted as t2 (the time obtained by adding the propagation delay decrease −Δ to the transmission start time t2 is t2. That is, t2 + (− Δ) = 100 + (10). = 110 is transmitted as t2.)

  The transmission start time t2 is advanced by an amount corresponding to the delay of the uplink signal accompanying the increase in the propagation delay (the time of the transmission start time t2 is delayed by an amount corresponding to the advance of the uplink signal accompanying the decrease in the propagation delay), and the transmission start time t2 from the transmission time t1. By shortening the time until the transmission start time is advanced by an increase in the propagation delay (by increasing the time from the transmission time t1 to the transmission start time t2 to delay the transmission start time by the propagation delay decrease), before switching. It will be the same arrival time.

  Consider a case where the OLT 200 and the ONU 100A are communicating. When the OLT 200 switches the wavelength of the upstream signal or the downstream signal, the optical transceiver (21, 22) causes the propagation delay difference generated between the ONU 100A and each optical transceiver (21, 22) at the time of its own device. A gate message GM including a time stamp t1 of the transmission time obtained by adding Δ, a transmission start time t2 that permits the upstream signal of the ONU 100A, and a transmission possible duration K of the upstream signal of the ONU 100A is transmitted. In this case, when the ONU 100A receives the gate message GM from the OLT 200, the ONU 100A adjusts the time of its own device to the time stamp of the gate message GM, and can transmit from the transmission start time t2 included in the gate message GM. Uplink signals are transmitted up to the duration K.

  Further, when the OLT 200 switches the wavelength of the upstream signal or downstream signal, the optical transceiver (21, 22) starts from the time stamp of the own device at time t1, the transmission start time t2 at which the upstream signal of the ONU 100A is permitted, and the ONU 100A. The gate message GM including the transmission start time t2 ′ obtained by reducing the propagation delay difference Δ generated between the optical transceivers (21, 22) and the ONU 100A upstream signal transmission possible duration K may be transmitted. . In this case, when the ONU 100A receives the gate message GM from the OLT 200, the ONU 100A matches the time of its own device with the time stamp t1 included in the gate message GM, and changes from the transmission start time t2 ′ included in the gate message GM to the gate message GM. Uplink signals are transmitted up to the included transmittable duration K.

  This will be described with reference to the time diagrams of FIGS. FIGS. 2 and 3 are examples of notifying transmission permission to the optical transceivers 21 and 22 by a gate message from the optical transceiver 21. 4 and 5 are examples in which transmission permission to the optical transceiver 21 is notified by a gate message from the optical transceivers 21 and 22. Here, it is assumed that the propagation delay time transmitted / received by the optical transceiver 21 in both uplink and downlink is shorter than the propagation delay time transmitted / received by the optical transceiver 22.

[First switching state]
A 1st switching state is demonstrated using the time diagram of FIG.
(1) Gate message from the optical transceiver 21 to the ONU The optical transceiver 21 transmits a gate message in which the ONU is designated by LLID. The gate message includes the current time t1, the transmission start time t2 at which communication is permitted, and the time K at which transmission permission is continued.
(2) Upstream signal from ONU to optical transceiver 21 The ONU that received the gate message sets its clock at the transmission time t1 of the message indicated by the time stamp of this message. The ONU transmits an uplink signal from the transmission start time t2 indicated by the gate message until the continuation time K elapses.
(1 ′) Gate message from the optical transceiver 21 to the ONU The optical transceiver 21 transmits a gate message in which the ONU is designated by LLID. The gate message includes a transmission time t1 ′ (= t1 + Δ) obtained by adding a propagation delay increase Δ to the current time t1, a transmission start time t2 ′ (= t2) for allowing communication, and a time K ′ for continuing transmission permission. (= K) is included. Here, Δ is a propagation delay difference between the ONU-optical transceiver 21 and the ONU-optical transceiver 22.
(2 ′) Upstream signal from ONU to optical transceiver 22 The ONU that has received the gate message sets its clock at the transmission time t1 ′ of the message indicated by the time stamp of this message. The ONU transmits an uplink signal from the transmission start time t2 ′ indicated by the gate message until the continuation time K elapses.

[Second switching state]
A 2nd switching state is demonstrated using the time diagram of FIG.
(1) Gate message from the optical transceiver 21 to the ONU The optical transceiver 21 transmits a gate message in which the ONU is designated by LLID. The gate message includes the current time t1, the transmission start time t2 at which communication is permitted, and the time K at which transmission permission is continued.
(2) Upstream signal from ONU to optical transceiver 21 The ONU that received the gate message sets its clock at the transmission time t1 of the message indicated by the time stamp of this message. The ONU transmits an uplink signal from the transmission start time t2 indicated by the gate message until the continuation time K elapses.
(1 ′) Gate message from the optical transceiver 21 to the ONU The optical transceiver 21 transmits a gate message in which the ONU is designated by LLID. The gate message has a transmission start time t2 ′ (= t2−Δ) obtained by subtracting the propagation delay increase Δ from the current own time t1 ′ (= t1) and the transmission start time t2 permitting the original communication, and transmission permission. Including the time K ′ (= K) to continue. Here, Δ is a propagation delay difference between the ONU-optical transceiver 21 and the ONU-optical transceiver 22.
(2 ′) Upstream signal from ONU to optical transceiver 22 The ONU that has received the gate message sets its clock at the transmission time t1 ′ of the message indicated by the time stamp of this message. The ONU transmits an uplink signal from the transmission start time t2 ′ indicated by the gate message until the continuation time K elapses.

[Third switching state]
A 3rd switching state is demonstrated using the time diagram of FIG.
(1) Gate message from the optical transceiver 21 to the ONU The optical transceiver 21 transmits a gate message in which the ONU is designated by LLID. The gate message includes the current time t1, the transmission start time t2 at which communication is permitted, and the time K at which transmission permission is continued.
(2) Upstream signal from ONU to optical transceiver 21 The ONU that received the gate message sets its clock at the transmission time t1 of the message indicated by the time stamp of this message. The ONU transmits an uplink signal from the transmission start time t2 indicated by the gate message until the continuation time K elapses.
(1 ′) Gate message from the optical transceiver 21 to the ONU The optical transceiver 21 transmits a gate message in which the ONU is designated by LLID. The gate message includes a transmission time t1 ′ (= t1 + Δ) obtained by adding a propagation delay increase Δ to the current time t1, a transmission start time t2 ′ (= t2) for allowing communication, and a time K ′ for continuing transmission permission. (= K) is included. Here, Δ is a propagation delay difference between the ONU-optical transceiver 21 and the ONU-optical transceiver 22.
(2 ′) Upstream signal from ONU to optical transceiver 22 The ONU that has received the gate message sets its clock at the transmission time t1 ′ of the message indicated by the time stamp of this message. The ONU transmits an uplink signal from the transmission start time t2 ′ indicated by the gate message until the continuation time K elapses.

[Fourth switching state]
A 4th switching state is demonstrated using the time diagram of FIG.
(1) Gate message from the optical transceiver 21 to the ONU The optical transceiver 21 transmits a gate message in which the ONU is designated by LLID. The gate message includes the current time t1, the transmission start time t2 at which communication is permitted, and the time K at which transmission permission is continued.
(2) Upstream signal from ONU to optical transceiver 21 The ONU that received the gate message sets its clock at the transmission time t1 of the message indicated by the time stamp of this message. The ONU transmits an uplink signal from the transmission start time t2 indicated by the gate message until the continuation time K elapses.
(1 ′) Gate message from the optical transceiver 21 to the ONU The optical transceiver 21 transmits a gate message in which the ONU is designated by LLID. The gate message includes a transmission start time t2 ′ (= t2−Δ) and a transmission permission in which the propagation delay increase Δ is expressed from the current own time t1 ′ (= t1) and the transmission start time t2 permitting the original communication. Including time K ′ (= K). Here, Δ is a propagation delay difference between the ONU-optical transceiver 21 and the ONU-optical transceiver 22.
(2 ′) Upstream signal from ONU to optical transceiver 22 The ONU that has received the gate message sets its clock at the transmission time t1 ′ of the message indicated by the time stamp of this message. The ONU transmits an uplink signal from the transmission start time t2 ′ indicated by the gate message until the continuation time K elapses.

  As shown in FIGS. 2 to 5, the optical communication system 301 arrives at the OLT 200 by increasing / decreasing the time transmitted by the gate message GM in accordance with the increase / decrease in the propagation delay difference Δ in the uplink direction or the downlink direction accompanying the switching of the wavelength. The time to do can be made constant. In this example, the process according to the propagation delay difference is performed on the transmission permission side, but the same process may be performed on the transmission permission side.

  As described above, the optical communication system 301 can notify the ONU (100A, 100B, 100C) that receives an arbitrary downstream wavelength of transmission permission to transmit at an arbitrary upstream wavelength. It is possible to provide a 1 to N optical access system that avoids the collision of uplink signals while freely changing the upper and lower combinations between wavelengths.

  Although the optical communication system 301 has been described with three ONUs and two wavelengths, the number of ONUs may be increased or decreased, and the number of wavelengths to be wavelength division multiplexed may be two or more. Moreover, although the wavelength transmitted / received for each ONU is set to one wavelength, a plurality of wavelengths may be used. Although the optical communication system 301 has been described as a PON, the same can be applied to an optical access network in which an optical switch is replaced with an optical splitter. The same applies to the following embodiments.

(Embodiment 2)
FIG. 6 is a conceptual diagram illustrating the optical communication system 302 according to the second embodiment. The optical communication system 302 includes an OLT 200 having an optical transceiver (21, 22) for each path (H1, H2), and an optical distribution network ODN that is an optical transmission path in the optical transceiver (21, 22). And a plurality of ONUs (100A, 100B, 100C) that are connected via a path (50 (H1), 50 (H2)) and transmit / receive optical signals to / from the OLT 200 by core line multiplexing and time division multiplexing. The optical communication system 302 is, for example, a PON, and transmits an optical signal by core multiplexing and time division multiplexing.

  The optical communication system 302 distributes and stores each ONU in a plurality of paths (H1, H2), while the optical communication system 301 in FIG. 1 distributes and stores each ONU in wavelengths (λ1, λ2). The point is different. In the second embodiment, description of parts that are the same as or substantially the same as those already described in the first embodiment is omitted.

  The ONUs (100A, 100B, 100C) and the OLT 200 are obtained by replacing the wavelengths of the ONUs (100A, 100B, 100C) and the OLT 200 described in the first embodiment with routes.

  The ONUs (100A, 100B, 100C) are installed in each subscriber's house, and the optical transceivers of each ONU output signal light in the assigned route for use in the uplink signal to be transmitted. The assigned route is one of a plurality of selectable routes (H1, H2).

  The ODN (50 (H1), 50 (H2)) combines the signal light from the optical transceiver of each ONU for each route (H1, H2) and couples it to the optical transceiver (21, 22) of the OLT 200. The signal light from the optical transceivers (21, 22) of the OLT 200 is branched for each route (H1, H2) and coupled to the optical transceiver of each ONU. Here, since the upstream signal light output from the optical transceiver of each ONU cannot be received if it simultaneously arrives at the OLT 200 in the same route, the OLT 200 determines the difference in propagation time in the corresponding route of the optical transceiver of each ONU. Considering this, transmission is permitted so that the optical transceivers (21, 22) of the OLT 200 do not overlap. The transmission permission is notified from the OLT 200 in the route being received by the optical transceiver on each ONU side. The route being received is one of a plurality of routes that can be selected as a route to be received by the ONU.

  The optical transceiver of the OLT 200 includes a plurality of light receivers that receive light from ODN (50 (H1), 50 (H2)) for each route. The optical transceiver of the OLT 200 receives signal light for each path (H1, H2).

  The upstream signal permission notification of the optical communication system 302 can be described by replacing the wavelength λ1 and the wavelength λ2 with the route H1 and the route H2, respectively, in the description of the permission notification of the optical communication system 301 in FIG.

  As described above, the optical communication system 302 can notify the ONU (100A, 100B, 100C) that receives a signal from an arbitrary downstream route of transmission permission to transmit on the arbitrary upstream route. Therefore, it is possible to provide a 1 to N optical access system that avoids the collision of uplink signals while freely changing the upper and lower combinations between routes.

  Although the optical communication system 302 has been described with three ONUs and two routes, the number of ONUs may be increased or decreased, and the number of routes may be two or more. In addition, although the transmission / reception route for each ONU is a single route, a plurality of routes may be used. Further, wavelength division multiplexing may be performed in each of the routes (H1, H2), and the processing of the optical communication system 301 and the processing of the optical communication system 302 in FIG. 1 may be combined.

(Other embodiments)
The embodiment described above shows one aspect of the present invention, and the present invention is not limited to the above-described embodiment, and has the configuration of the present invention to achieve the object and effect. Needless to say, modifications and improvements within the scope of the present invention are included in the content of the present invention. Further, the specific structure, shape, and the like in carrying out the present invention are not problematic as other structures, shapes, and the like as long as the objects and effects of the present invention can be achieved. The present invention is not limited to the above-described embodiments, and modifications and improvements within the scope that can achieve the object of the present invention are included in the present invention.

  For example, the information transmission medium is a wavelength in the optical communication system 301 and a path in the optical communication system 302, but is another division multiplexing technique, for example, an optical code, one OFDM bin, polarization, and phase. May be.

  The present invention can be used in a technical field related to an optical communication system applied to a PON.

21, 22: Optical transceiver 25: Optical multiplexer / demultiplexer 50, 50 (H1), 50 (H2): ODN
55: Optical splitters H1, H2: Paths 100A, 100B, 100C: ONU
200: OLT
301, 302: Optical communication system GM: Gate message K: Transmission possible duration

Claims (4)

A station side device (OLT: Optical Line Terminal) having at least two optical transceivers having different wavelengths, paths, or combinations of wavelengths and paths;
Connected to the OLT via an optical transmission line, and transmits / receives optical signals to / from the OLT by wavelength division multiplexing and time division multiplexing, core line multiplexing and time division multiplexing, or wavelength division multiplexing, core line multiplexing, and time division multiplexing. A plurality of subscriber side devices (ONU: Optical Network Unit);
With
The OLT is
When switching the wavelength, route, or combination of wavelength and route for upstream or downstream signals,
When notifying the ONU of transmission permission from one optical transceiver to another optical transceiver that has a propagation delay with the ONU different from the one optical transceiver,
The transmission permission is
A time obtained by adding a propagation delay difference obtained by subtracting a propagation delay between the ONU and the one optical transceiver from a propagation delay between the ONU and the other optical transceiver to the current time of the one optical transceiver; Including a transmission start time at which transmission of the upstream signal of the ONU is permitted and a duration at which transmission of the upstream signal of the ONU is permitted,
Alternatively, from the current time of one optical transceiver, the transmission start time permitting transmission of the upstream signal of the ONU, and the propagation delay between the ONU and the other optical transceiver, the ONU and the one optical transceiver Including a time when the propagation delay difference is reduced and a duration time during which transmission of the upstream signal of the ONU is permitted,
The ONU is
When the transmission permission from the OLT is received, the time of the own device is adjusted to the current time included in the transmission permission, and an uplink signal is transmitted to the other optical transceiver at the transmission start time included in the transmission permission. An optical communication system, wherein an uplink signal is transmitted to one of the optical transceivers after the propagation delay difference has elapsed at the transmission start time and before the duration included in the transmission permission. A station side device (OLT: Optical Line Terminal) having at least two optical transceivers having different wavelengths, paths, or combinations of wavelengths and paths;
Connected to the OLT via an optical transmission line, and transmits / receives optical signals to / from the OLT by wavelength division multiplexing and time division multiplexing, core line multiplexing and time division multiplexing, or wavelength division multiplexing, core line multiplexing, and time division multiplexing. A plurality of subscriber side devices (ONU: Optical Network Unit);
With
The OLT is
When switching the wavelength, route, or combination of wavelength and route for upstream or downstream signals,
When notifying the ONU of transmission permission from the plurality of optical transceivers to one of the optical transceivers whose propagation delay with the ONU is different from that of the other optical transceivers,
The transmission permission from the other optical transceiver is
A time obtained by adding a propagation delay difference obtained by subtracting a propagation delay between the ONU and one optical transceiver from a propagation delay between the ONU and another optical transceiver to the current time of the other optical transceiver; Including a transmission start time at which transmission of the upstream signal of the ONU is permitted and a duration at which transmission of the upstream signal of the ONU is permitted,
Alternatively, from the current time of the other optical transceiver, from the transmission start time permitting transmission of the upstream signal of the ONU, from the propagation delay between the ONU and the other optical transceiver, the ONU and the one optical transceiver Including a time when the propagation delay difference is reduced and a duration time during which transmission of the upstream signal of the ONU is permitted,
The ONU is
When receiving the transmission permission from the OLT, the time of its own device is adjusted to the current time included in the transmission permission, and from the transmission start time included in the transmission permission to the duration included in the transmission permission. An optical communication system, wherein an upstream signal is transmitted to the one optical transceiver in between. A station side device (OLT: Optical Line Terminal) having at least two optical transceivers having different wavelengths, paths, or combinations of wavelengths and paths;
Connected to the OLT via an optical transmission line, and transmits / receives optical signals to / from the OLT by wavelength division multiplexing and time division multiplexing, core line multiplexing and time division multiplexing, or wavelength division multiplexing, core line multiplexing, and time division multiplexing. A plurality of subscriber side devices (ONU: Optical Network Unit);
In an optical communication system comprising:
When switching the wavelength, route, or combination of wavelength and route for upstream or downstream signals,
When notifying the ONU from the OLT of permission to transmit to the other optical transceiver having a propagation delay with the ONU different from that of the optical transceiver from the one optical transceiver.
The transmission permission is
A time obtained by adding a propagation delay difference obtained by subtracting a propagation delay between the ONU and the one optical transceiver from a propagation delay between the ONU and the other optical transceiver to the current time of the one optical transceiver; Including a transmission start time at which transmission of the upstream signal of the ONU is permitted and a duration at which transmission of the upstream signal of the ONU is permitted,
Alternatively, from the current time of one optical transceiver, the transmission start time permitting transmission of the upstream signal of the ONU, and the propagation delay between the ONU and the other optical transceiver, the ONU and the one optical transceiver Including a time when the propagation delay difference is reduced and a duration time during which transmission of the upstream signal of the ONU is permitted,
When the transmission permission from the OLT is received, the ONU time is adjusted to the current time included in the transmission permission, and the ONU is transferred from the ONU to another optical transceiver at the transmission start time included in the transmission permission. Transmitting an upstream signal from the ONU to the one optical transceiver after the propagation delay difference has elapsed at the transmission start time and until the duration included in the transmission permission. An optical communication method characterized by the above. A station side device (OLT: Optical Line Terminal) having at least two optical transceivers having different wavelengths, paths, or combinations of wavelengths and paths;
Connected to the OLT via an optical transmission line, and transmits / receives optical signals to / from the OLT by wavelength division multiplexing and time division multiplexing, core line multiplexing and time division multiplexing, or wavelength division multiplexing, core line multiplexing, and time division multiplexing. A plurality of subscriber side devices (ONU: Optical Network Unit);
In an optical communication system comprising:
When switching the wavelength, route, or combination of wavelength and route for upstream or downstream signals,
When notifying transmission permission from the OLT to the ONU from a plurality of the optical transceivers to the one optical transceiver whose propagation delay with the ONU is different from that of the other optical transceivers,
The transmission permission from the other optical transceiver is
A time obtained by adding a propagation delay difference obtained by subtracting a propagation delay between the ONU and one optical transceiver from a propagation delay between the ONU and another optical transceiver to the current time of the other optical transceiver; Including a transmission start time at which transmission of the upstream signal of the ONU is permitted and a duration at which transmission of the upstream signal of the ONU is permitted,
Alternatively, from the current time of the other optical transceiver, from the transmission start time permitting transmission of the upstream signal of the ONU, from the propagation delay between the ONU and the other optical transceiver, the ONU and the one optical transceiver Including a time when the propagation delay difference is reduced and a duration time during which transmission of the upstream signal of the ONU is permitted,
When receiving the transmission permission from the OLT, the time of the ONU is matched with the current time included in the transmission permission, and from the transmission start time included in the transmission permission to the duration included in the transmission permission. An optical communication method comprising transmitting an upstream signal from the ONU to the one optical transceiver in between.

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