JP5588543B1 - Discovery method and optical transmission system - Google Patents

Abstract

A discovery signal can be received even when an ONU wavelength tunable filter is in an indefinite state, such as immediately after startup, and an increase in ONU authentication time is suppressed even if the number of wavelength slots used for transmission / reception of optical signals increases. An object of the present invention is to provide a discovery method and an optical transmission system.
When transmitting a discovery signal, the present invention expands the transmission wavelength band of a wavelength tunable filter in an ONU (subscriber premises equipment) and uses light having a signal wavelength close to that of the discovery signal in an OLT (station side apparatus). The signal was stopped.
[Selection] Figure 1

Description

  The present invention relates to a discovery method in an optical transmission system that performs optical communication using a plurality of wavelengths, and the optical transmission system.

  In an optical transmission system represented by a PON (Passive Optical Network) system, a wider bandwidth is required. As a technique for realizing a wider band, a WDM (Wavelength Division Multiplexing) technique using a plurality of wavelengths is available in addition to the conventional technique for increasing the bit rate.

The PON system aggregates one OLT (Optical Line Terminal) corresponding to a station side device, a plurality of ONUs (Optical Network Units) corresponding to subscriber home devices, an optical transmission cable connecting them, and a plurality of subscriber home devices. It is a point to multipoint (P2MP) type optical transmission system comprising an aggregation device. The ONU shares the optical transmission cable with the OLT and performs transmission. Conventionally, multiplexing of ONUs has been realized by TDM (Time Division Multiplexing) -PON which switches allocation of OLT and optical transmission cable in units of time.
In this specification, the station-side device may be described as an OLT or a station-side optical signal transmission / reception device, and the subscriber home device may be described as an ONU or subscriber home optical signal transmission / reception device.

  With a WDM / TDM-PON technology that combines a WDM technology that uses multiple wavelengths and a TDM-PON, a wider bandwidth can be achieved. In the WDM / TDM-PON, the OLT is composed of a plurality of OSUs (Optical Subscriber Units). Each OSU has a function of transmitting and receiving signals having different wavelengths.

  In WDM / TDM-PON, it is necessary to explicitly specify the wavelength used for data transmission / reception between the OLT and the ONU. The ONU includes a wavelength tunable filter and can receive only a signal transmitted from an arbitrary OSU by blocking a signal having an unintended wavelength. In WDM / TDM-PON, before starting data transmission / reception, it is necessary to determine in advance the wavelength used for data transmission / reception and to change the transmission wavelength band of the wavelength tunable filter.

  However, in a wavelength tunable WDM / TDM-PON equipped with a wavelength tunable filter (see, for example, Non-Patent Document 1), the operation of the wavelength tunable filter is not defined when the ONU is activated, and the transmission wavelength band at the time of activation. Is undefined. For this reason, in the wavelength tunable WDM / TDM-PON, it is necessary to determine the wavelength used for data transmission / reception by the discovery signal.

"Wavelength-tunable WDM / TDM-PON for next-generation optical access networks", Shinya Tamaki, Shin Kaneko, Hirotaka Nakamura, Shunji Kimura, Naoto Yoshimoto, July 2012 Communication System Study Group, IEICE Technical Research Report vol. 112 (118): CS2012-30, pp39-44

  For example, in a PON system using only a single wavelength, since the ONU is not equipped with a tunable filter, the ONU waits for a certain period of time to find a discovery signal periodically transmitted from the OLT, It was possible to respond to the OLT.

  However, the wavelength variable WDM / TDM-PON blocks the discovery signal by the wavelength variable filter provided in the ONU, and the ONU may not be able to receive the discovery signal transmitted from the OLT.

  Here, there is an invention described in Japanese Patent Application No. 2011-280555 as a discovery signal transmission / reception method in WDM / TDM-PON. In the invention of the patent document, a discovery signal can be transmitted to all ONU connection ends by adjusting the control unit of the OLT. However, the invention of the patent document has a first problem that the discovery signal may be cut off when the ONU wavelength tunable filter is in an indefinite state such as immediately after activation.

  In general, as a method of transmitting a discovery signal in WDM / TDM-PON, there are a method of transmitting a discovery signal from only a single OSU and a method of transmitting a discovery signal from all OSUs. In the case of a method for transmitting discovery signals from all OSUs, it is necessary for all OSUs to transition to a startup state at the moment of transmitting discovery signals, leading to an increase in power consumption of the system. For this reason, in the wavelength variable WDM / TDM-PON, it is effective to transmit a discovery signal with a single wavelength from any single OSU.

  In WDM / TDM-PON, in order to receive a discovery signal with an unknown single wavelength, the wavelength slot used for the OLT discovery signal is changed periodically with the transmission wavelength band of the tunable filter fixed in the ONU. There is a technique for periodically changing the transmission wavelength band of the wavelength tunable filter of the ONU in a state where the wavelength slot used for the discovery signal transmitted from the OLT is fixed.

  As the latter method, there is a sequential search in which the transmission band of the ONU wavelength tunable filter is sequentially changed. This method has a second problem that the time required for authentication of a newly connected ONU increases as the number of wavelength slots to be used increases.

  Therefore, in order to solve the above problems, the present invention can receive a discovery signal even when the ONU wavelength tunable filter is in an indefinite state such as immediately after startup, and the number of wavelength slots used for transmission / reception of optical signals increases. However, it is an object of the present invention to provide a discovery method and an optical transmission system capable of suppressing an increase in ONU authentication time.

  In order to solve the above problems, the present invention extends the transmission wavelength band of a wavelength tunable filter in an ONU (subscriber home device) and transmits a discovery signal close to the discovery signal in an OLT (station side device). The optical signal with the signal wavelength was stopped.

Specifically, the discovery method according to the present invention includes a single station side device and a plurality of subscriber home devices, and uses a plurality of signal wavelengths between the station side device and the subscriber home devices. A discovery method in an optical transmission system that transmits and receives optical signals,
When transmitting a discovery signal of an arbitrary wavelength from the station side device to the subscriber premises device, the station side device stops transmitting an optical signal in a predetermined wavelength range including the wavelength of the discovery signal, and the subscription The discovery signal is searched for by expanding a transmission wavelength band of a variable wavelength filter for selecting a signal wavelength to be received in the home apparatus so that a plurality of signal wavelengths are included.

  By expanding the transmission wavelength band of the ONU filter, the probability that the discovery signal passes through the filter increases. At this time, if the filter having the extended transmission wavelength band transmits another optical signal, the ONU cannot recognize the discovery signal, and the OLT stops the other optical signal in the transmission wavelength band. For this reason, since the number of times of changing the transmission band is reduced even if the sequential search is not performed or the sequential search is performed, the ONU authentication time can be shortened. The same is true even if the transmission wavelength band is indefinite immediately after the ONU is activated.

  Therefore, the present invention can receive a discovery signal even when the ONU wavelength tunable filter is in an indefinite state such as immediately after startup, and the ONU authentication time can be increased even if the number of wavelength slots used for transmission / reception of optical signals increases. A discovery method capable of suppressing the increase can be provided.

  In the discovery method according to the present invention, the predetermined wavelength range is a range including all signal wavelengths, and the transmission wavelength band is extended to include all signal wavelengths. When the transmission wavelength band of the filter can be expanded to include all signal wavelengths, the discovery signal can be detected without performing a sequential search. Therefore, the present invention can receive a discovery signal even when the ONU wavelength tunable filter is in an indefinite state such as immediately after startup, and the ONU authentication time can be increased even if the number of wavelength slots used for transmission / reception of optical signals increases. A discovery method capable of suppressing the increase can be provided.

  The discovery method according to the present invention is characterized in that the discovery signal is searched while moving a center wavelength of the transmission wavelength band of the variable wavelength filter at a wavelength interval corresponding to the transmission wavelength band. When the transmission wavelength band of the filter cannot be expanded to include all signal wavelengths, a search is sequentially performed to detect a discovery signal. However, unlike the conventional sequential search, since the sequential search is performed with the transmission wavelength band extended, the probability of detecting a discovery signal is increased. Therefore, the present invention can receive a discovery signal even when the ONU wavelength tunable filter is in an indefinite state such as immediately after startup, and the ONU authentication time can be increased even if the number of wavelength slots used for transmission / reception of optical signals increases. A discovery method capable of suppressing the increase can be provided.

  When the wavelength information of the ONU is included in the discovery signal frame, the ONU can be authenticated by detecting the discovery signal by the above-described method. However, when the wavelength of the discovery signal itself is ONU wavelength information, it is necessary not only to detect the discovery signal but also to detect the wavelength.

  Therefore, in the discovery method according to the present invention, after the discovery signal is detected by the subscriber premises apparatus, the transmission wavelength band is divided into two, and the band including the discovery signal is set as a new transmission wavelength band. The two-branch search is repeated until the variable wavelength filter transmits only the discovery signal. By repeating the two-branch search, the transmission wavelength band of the filter is narrowed, and finally a band that can transmit only the discovery signal is obtained. Thus, the wavelength of the discovery signal can be detected by repeating the two-branch search.

  The discovery method according to the present invention detects a discovery signal by the above two-branch search after performing a discovery method for extending the transmission wavelength band of a filter. Even when the transmission wavelength band of the filter cannot be expanded to include all signal wavelengths, the wavelength of the discovery signal can be detected.

One optical transmission system according to the present invention includes:
A single station side device,
A plurality of subscriber home devices;
An optical transmission line connecting the station side device and the subscriber premises device via a power splitter;
A communication control function for performing transmission and reception of optical signals using a plurality of signal wavelengths between the station side device and the subscriber premises device, and performing the discovery method at a predetermined time,
Is provided.

Another optical transmission system according to the present invention is:
A single station side device,
A plurality of subscriber home devices;
An optical transmission line that connects the station side device and the subscriber premises device via a device having a wavelength routing function;
When performing the discovery method, while selecting the wavelength of the discovery signal so that the discovery signal arrives in sequence to a specific subscriber home device or a specific subscriber home device group, A communication control function for transmitting and receiving optical signals using a plurality of signal wavelengths with the subscriber home device or another subscriber home device group;
Is provided.

  The optical transmission system can realize the discovery method. Therefore, the present invention can receive a discovery signal even when the ONU wavelength tunable filter is in an indefinite state such as immediately after startup, and the ONU authentication time can be increased even if the number of wavelength slots used for transmission / reception of optical signals increases. An optical transmission system capable of suppressing an increase can be provided.

  The present invention can receive a discovery signal even when the ONU wavelength tunable filter is in an indefinite state, such as immediately after startup, and increase the ONU authentication time even if the number of wavelength slots used for transmitting and receiving optical signals increases. It is possible to provide a discovery method and an optical transmission system that can be suppressed.

It is a figure explaining the discovery method which concerns on this invention. The discovery method according to the present invention is a technique for accelerating discovery signal search by stopping signal transmission from other wavelength slots at the time of discovery signal transmission and extending the transmission wavelength band of the wavelength variable filter. It is a figure explaining the discovery method which concerns on this invention. The discovery method according to the present invention speeds up discovery signal search by stopping signal transmission from a wavelength slot adjacent to the discovery signal at the time of discovery signal transmission and sequentially searching with the transmission wavelength band of the wavelength tunable filter expanded. It is a technique to do. 5 is a flowchart illustrating a discovery method according to the present invention. The discovery method according to the present invention is a technique for speeding up a search for a discovery signal by combining a sequential search and a two-branch search in a state where the transmission wavelength band of the wavelength tunable filter is varied and the transmission wavelength band is expanded. It is a figure explaining the discovery method which concerns on this invention. The discovery method according to the present invention is a technique for specifying an unknown arbitrary wavelength at high speed by applying a sequential search phase and a two-branch search phase. It is a figure explaining the discovery method which concerns on this invention. The discovery method according to the present invention is a method of identifying an unknown arbitrary wavelength at high speed by applying a two-branch search phase. It is a figure explaining the optical transmission system concerning the present invention. This figure is an example of transmission / reception of a plurality of wavelength signals in a WDM / TDM-PON using a power splitter. It is a figure explaining the optical transmission system concerning the present invention. This figure is an example of transmitting and receiving a plurality of wavelength signals in a WDM / TDM-PON using a recurring AWG. It is a figure explaining the optical transmission system concerning the present invention. This figure is an example of transmission / reception of a plurality of wavelength signals in WDM / TDM-PON using an optical switch.

  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)
The discovery method of the present embodiment includes a single station side device and a plurality of subscriber home devices, and transmits and receives optical signals using a plurality of signal wavelengths between the station side device and the subscriber home devices. A discovery method in an optical transmission system to perform,
When transmitting a discovery signal of an arbitrary wavelength from the station side device to the subscriber premises device, the station side device stops transmitting an optical signal in a predetermined wavelength range including the wavelength of the discovery signal, and the subscription The discovery signal is searched for by expanding a transmission wavelength band of a variable wavelength filter for selecting a signal wavelength to be received in the home apparatus so that a plurality of signal wavelengths are included.

  In particular, the present embodiment is characterized in that the predetermined wavelength range is a range including all signal wavelengths, and the transmission wavelength band is extended to include all signal wavelengths.

  FIG. 1 is a diagram for explaining the discovery method of the present embodiment. In this embodiment, signal transmission from other wavelength slots is stopped during discovery signal transmission, and the discovery signal search is speeded up by extending the transmission wavelength band of the wavelength tunable filter.

  More specifically, when the OLT transmits a discovery signal using an arbitrary one wavelength slot, the OLT stops all signal transmission using the other wavelength slots, and the ONU extends the transmission wavelength band of the tunable filter. As a result, the ONU can simultaneously receive signals of all wavelength slots used for transmission and reception, and can search for a discovery signal with an arbitrary single wavelength at high speed.

  As a result, it is possible to search for a discovery signal with an arbitrary single wavelength at a higher speed as compared with a conventional sequential search method that repeatedly executes a process for determining whether a discovery signal is included in a single wavelength slot.

  In addition, the discovery method according to the present embodiment achieves band use efficiency equivalent to the technique in which the OLT uses all wavelength slots to transmit discovery signals, and the OLT transmits discovery signals using all wavelength slots. Compared with the technique, there is an advantage that the power consumption on the OLT side required for transmitting the discovery signal can be reduced.

(Embodiment 2)
The discovery method of this embodiment is characterized in that the discovery signal is searched for while moving the center wavelength of the transmission wavelength band of the variable wavelength filter at a wavelength interval corresponding to the transmission wavelength band.

  FIG. 2 is a diagram for explaining the discovery method of this embodiment. In the present embodiment, when transmitting a discovery signal, signal transmission from a wavelength slot adjacent to the discovery signal is stopped, and the search is sequentially performed in a state where the transmission wavelength band of the wavelength tunable filter is expanded, thereby speeding up the discovery signal search.

  More specifically, when the OLT transmits a discovery signal using an arbitrary one wavelength slot, the OLT stops signal transmission using the wavelength slot adjacent to the discovery signal, and the ONU extends the transmission wavelength band of the wavelength tunable filter. . As a result, the ONU can simultaneously receive signals of a plurality of wavelength slots used for transmission / reception within the transmission wavelength band. Then, the ONU sequentially searches for discovery signal wavelengths using the extended transmission wavelength band.

  This embodiment can improve the bandwidth utilization efficiency by searching for a discovery signal with an arbitrary single wavelength at high speed and reducing the number of wavelength slots for stopping signal transmission.

  The discovery method of this embodiment may be used when the transmission wavelength band of the wavelength tunable filter of the ONU is smaller than the total wavelength band of all the wavelength slots of the WDM / TDM-PON. Further, by changing the number of wavelength slots that must be stopped at the time of discovery signal transmission, it may be used for improving band utilization efficiency of other wavelengths at the time of discovery signal transmission from the OLT.

  In the discovery method of the present embodiment, the OLT signal transmission stop slot is determined according to the transmission wavelength band of the wavelength tunable filter. For example, when the transmission wavelength band is set so that the wavelength tunable filter of the ONU receives X wavelength slots at the same time, the OLT uses (2X-1) wavelengths centered on the wavelength slot of the discovery signal when transmitting the discovery signal. Stops signal transmission from the slot. The transmission wavelength band sequentially searched in the wavelength tunable filter can be determined at the time of designing the WDM / TDM-PON from the viewpoint of the transmission wavelength band performance and band utilization efficiency of the wavelength tunable filter.

(Embodiment 3)
The discovery methods described in the first and second embodiments are applicable when wavelength information to be set is included as frame information in the discovery signal, that is, when it is not necessary to specify which wavelength slot the signal has been received.

  The discovery method of the present embodiment is applied when the wavelength of the discovery signal itself is wavelength information to be set, that is, when it is necessary to identify which wavelength slot the discovery signal is.

  In the discovery method of the present embodiment, after the discovery signal is detected by the subscriber premises apparatus, the transmission wavelength band is divided into two, and the band including the discovery signal is set as a new transmission wavelength band. The search is repeated until the variable wavelength filter transmits only the discovery signal.

  The discovery method of the present embodiment is executed after the discovery signal is detected by the discovery method described in the first and second embodiments. Hereinafter, an example in which the discovery method according to the present embodiment is executed after a discovery signal is detected by the discovery method described in the second embodiment will be described. FIG. 3 is a flowchart for explaining the discovery method of this embodiment. FIG. 4 is a diagram for explaining the discovery method (two-branch search) of this embodiment. In the present embodiment, the transmission wavelength band of the wavelength tunable filter is varied, and the discovery signal wavelength is specified at a higher speed by combining the sequential search and the two-branch search in a state where the transmission wavelength band is expanded.

  More specifically, as shown in FIG. 3, the discovery method according to the present embodiment includes three phases: an initial center wavelength and transmission wavelength band determination phase, a sequential search phase, and a two-branch search phase. In the initial center wavelength and transmission wavelength band determination phase and sequential search phase, specify that a discovery signal exists in a plurality of wavelength slots, and then uniquely specify the wavelength slot in which the discovery signal exists in the two-branch search phase Thus, the wavelength slot of the discovery signal transmitted by an arbitrary wavelength is specified at high speed.

  In the discovery method of this embodiment, the total number of wavelengths used in WDM / TDM-PON is a power of 2, and the wavelength slots of discovery signals transmitted from the OSU are aligned at equal intervals with respect to the wavelength axis. It is assumed that. Similarly to the discovery method of the second embodiment, it is necessary to stop signal transmission from the wavelength slot adjacent to the wavelength slot of the discovery signal when transmitting the discovery signal in the OLT. Since the OLT does not recognize the transmission wavelength band of the ONU wavelength variable filter at the time of discovery signal transmission, the transmission wavelength band of the wavelength variable filter determined in the initial center wavelength and transmission wavelength band determination phase is used. Signal transmission from the adjacent wavelength slot is stopped.

  The discovery method of this embodiment will be further described with reference to FIG. FIG. 4 shows a method of speeding up the discovery signal wavelength identification by expanding / contracting the transmission wavelength band of the wavelength tunable filter, in which the maximum transmission wavelength band of the wavelength tunable filter is greater than the wavelength slot where the discovery signal may be transmitted. This is an application example in the case of being small.

In the initial center wavelength and transmission wavelength band determination phase, the transmission center of the wavelength variable filter used in the sequential search phase using the performance of the wavelength variable filter and the wavelength bandwidth in which the wavelength used in the WDM / TDM-PON may exist. The wavelength λ _center and the transmission wavelength band λ _band are determined. The initial value of the transmission wavelength band λ _band is smaller than the maximum transmission wavelength band that can be realized by the wavelength tunable filter, and is 1/2 ^N times the total wavelength band of the wavelength slots used in the WDM / TDM-PON (N is an arbitrary natural number) It is the maximum wavelength band that satisfies

The transmission center wavelength λ _center is determined based on the transmission wavelength band λ _band . In FIG. 4, since the search is sequentially performed from a low wavelength toward a high wavelength, a wavelength higher by λ _band / 2 from the lowest transmission wavelength band to be searched is set as a transmission center wavelength. However, λ _band × N + λ _band / 2 (N is an arbitrary integer) may be used according to the search order of discovery wavelengths.

For example, as shown in FIG. 4, when the total wavelength band of the wavelength slots used in the WDM / TDM-PON is λ and the maximum transmission wavelength band of the wavelength variable filter is between λ / 2 ² and λ / 2, the sequential search phase initial center wavelength than the minimum wavelength lambda / 2 ³ long wavelength side, the transmission wavelength band becomes lambda / 2 ² in.

  The wavelength acquired after applying the wavelength slot of the discovery signal transmitted from the OSU and the sequential search phase and the two-branch search phase of the third discovery signal search method of the present invention by such an initial value setting method of the transmission wavelength band Match the transmission center wavelength of the variable filter.

  In the sequential search phase, the initial center wavelength and the transmission wavelength band determined in the initial center wavelength and transmission wavelength band determination phase are used to perform a sequential search for changing the transmission center wavelength.

  The ONU broadens the transmission wavelength band of the wavelength tunable filter and receives a plurality of wavelength slots at a time, and determines whether a discovery signal is included in the plurality of wavelength slots. When the discovery signal is not included, the discovery signal is searched by changing the transmission center wavelength of the wavelength tunable filter. Because discovery signals are searched for multiple wavelength slots at the same time, all wavelength slots used in WDM / TDM-PON are faster than when searching for each wavelength slot where discovery signals may be transmitted. It becomes possible to search for.

  In the sequential search phase, the discovery method of the second embodiment may be applied using the transmission wavelength band determined in the initial center wavelength and transmission wavelength band determination phase. When all the wavelength slots used in the WDM / TDM-PON are set as the transmission wavelength band as in the first embodiment, only the two-branch search phase is executed without performing the sequential search phase.

For example, as shown in FIG. 4, the sequential search phase is executed using the conditions determined in the initial center wavelength and transmission wavelength band phase. In this example, in the third search, the transmission wavelength band of the wavelength tunable filter matches the wavelength of the discovery signal, and the discovery signal is received. Therefore, the ONU recognizes that a discovery signal exists in any one of the wavelength slots from λ ₈ to λ ₁₁ .

  In the two-branch search phase, after confirming that a discovery signal is included in any of a plurality of wavelength slots, the transmission wavelength band is contracted and the transmission center band is repeatedly changed. This is a discovery signal search method characterized by speeding up identification of a discovery signal wavelength to be transmitted.

  In the two-branch search phase, a plurality of wavelength slots in which a discovery signal may exist is divided into two wavelength slot groups, and the transmission center wavelength of the wavelength tunable filter is set as the center wavelength of one wavelength slot group. The total wavelength band of the divided wavelength slots is set as the transmission wavelength band, and a discovery signal is awaited. The standby time interval is longer than the discovery signal transmission interval. When the discovery signal is received, the wavelength is further subdivided. When the discovery signal is not received, the other wavelength slot group is further subdivided and the search for the discovery signal proceeds. When the transmission wavelength band of the wavelength tunable filter becomes equal to the wavelength slot of WDM / TDM-PON, the search is terminated.

For example, in FIG. 4, the discovery signal is not detected in the fourth search. For this reason, it can be determined that a discovery signal exists in the wavelength band in which the search is not performed in the fourth search, that is, λ ₁₀ or λ ₁₁ among the λ ₈ to λ ₁₁ wavelength bands searched in the third search. In the fifth search, λ ₁₀ is searched to find a discovery signal. At this time, since the transmission wavelength band and wavelength slot band of the tunable filter are equivalent to end the search, the discovery signal wavelength is determined to be lambda _10.

The average period required for the discovery signal search when the sequential search phase and the two-branch search phase are used in combination as in the present embodiment is 2 ^α−1 + log ₂ (N / 2 ^α ) (N is the number of wavelength slots, 2 ^α-1 is the average number of sequential searches), and when N is greater than 4, it is smaller than N / 2, which is the average period required for discovery signal detection by sequential search.

  In both the sequential search phase and the two-branch search phase, it is necessary to wait for the discovery signal at a time interval equal to or longer than the discovery signal transmission cycle. When the ONU waits at an interval equal to or longer than the cycle transmitted from the OLT, the ONU may receive at least one discovery signal. As a result, it is determined that the discovery signal has not arrived because the discovery signal is not transmitted from the OLT but the wavelength variable filter blocks the discovery signal.

  FIG. 5 is a diagram for explaining another example of the discovery method of the present embodiment. FIG. 5 shows a method for speeding up the discovery signal wavelength identification by expanding / contracting the transmission wavelength band of the wavelength tunable filter, in which the maximum transmission wavelength band of the wavelength tunable filter is greater than the wavelength slot in which the discovery signal may be transmitted. This is an example of application when it is large.

An example in which the third discovery signal search method of the present invention is applied to a WDM / TDM-PON in which the maximum transmission wavelength band of the wavelength tunable filter can cover all the wavelength slots is shown. When the wavelength tunable filter can be set to transmit all the wavelength slots of WDM / TDM-PON, the wavelength search of the discovery signal is performed only by the two-branch search. As shown in FIG. 5, a half value of the total wavelength slot bandwidth of WDM / TDM-PON is set as the initial value of the transmission wavelength band λ _band , and the two-branch search phase is executed.

  In this way, the wavelength of a discovery signal using an unknown arbitrary wavelength can be specified at a high speed by performing a sequential search by expanding the transmission wavelength band of the wavelength tunable filter and narrowing down the wavelength of the discovery signal by a two-branch search. Is possible.

(Embodiment 4)
A WDM / TDM-PON equipped with a wavelength tunable filter has been proposed to have a configuration using a power splitter and a device having a wavelength routing function. As an element having a wavelength routing function, there is a circulating AWG (Arrayed waveguide grating) or an optical switch. FIG. 6 shows a WDM / TDM-PON configuration using a power splitter, FIG. 7 shows a WDM / TDM-PON configuration using a circular AWG, and FIG. 8 shows a WDM / TDM-PON configuration using an optical switch.

[1] WDM / TDM-PON using power splitter
The WDM / TDM-PON 301 in FIG.
A single station side device 60;
A plurality of subscriber home devices 61;
An optical transmission line 65 for connecting the station side device 60 and the customer premises device 61 via a power splitter 62;
A communication control function for performing transmission and reception of optical signals using a plurality of signal wavelengths between the station-side device 60 and the subscriber premises device 61, and performing the discovery method described in the first to third embodiments at a predetermined time;
Is provided.

  The WDM / TDM-PON 301 includes an optical transmission path 65 in which a station side optical signal transmission / reception device 60, a subscriber home optical signal transmission / reception device 61-x, and a plurality of power splitters (62, 63-x) are connected in multiple stages.

  The station-side optical signal transmitter / receiver 60 includes an optical transmitter 601-x, an optical receiver 602-x, a filter 603-x, and a spectrometer 604-x that separates transmitted light and received light. x, a control unit 605, and a power splitter 606. The subscriber home optical signal transmission / reception device 61-x includes an optical transmitter 611-x, an optical receiver 612-x, a wavelength tunable filter 613-x, a spectroscope 614-x, and a controller 615-x. Control units (605, 615) are the communication control function.

  The WDM / TDM-PON 301 transmits a discovery signal at an arbitrary wavelength from the optical transmitter 601-i of the station side optical signal transmitter / receiver 60-i designated by the control unit 605 of the station side optical signal transmitter / receiver 60, and newly The control unit 615-j of the subscriber optical signal transmitter / receiver 61-j connected to the network dynamically sets the transmission center wavelength and the transmission wavelength band of the wavelength tunable filter 613-j at a time interval equal to or longer than the OLT discovery signal transmission cycle. By changing, a discovery signal with an unknown arbitrary wavelength is received.

  The WDM / TDM-PON 301 transmits all the other station-side optical signal transceivers 60-x (x ≠) by the control unit 605 at the moment of transmitting a discovery signal from any one station-side optical signal transceiver 60-i. i) Alternatively, signal transmission from the station-side optical signal transmitter / receiver 60-y whose wavelength slot is adjacent to the station-side optical signal transmitter 601-i is stopped.

  As shown in FIG. 6, the WDM / TDM-PON 301 receives optical signals of all wavelengths transmitted from the station side optical signal transmitter / receiver 60-x in the subscriber home optical signal transmitter / receiver 61-x. In addition to the discovery signal transmitted from the station-side optical signal transmitter / receiver 60-i, another station-side optical signal transmitter / receiver 60-x (x ≠ i) or the station-side optical signal transmitter / receiver 60-y adjacent to the wavelength slot When the discovery signal or the data signal is transmitted from the subscriber optical signal transmission / reception device 61-x, the subscriber optical signal transmission / reception device 61-x receives a signal in which a plurality of wavelengths are mixed by extending the transmission wavelength band of the wavelength tunable filter. Accordingly, there is a possibility that the subscriber home optical signal transmission / reception device 61-x cannot demodulate the discovery signal. Therefore, the control unit 605 of the station-side optical signal transmission / reception device 60 exclusively transmits the optical signal at the time of discovery signal transmission.

[2] WDM / TDM-PON using orbiting AWG
The WDM / TDM-PON 302 in FIG.
A single station side device 70;
A plurality of subscriber home devices 71;
An optical transmission line 75 for connecting the station side device 70 and the customer premises device 71 via a device 72 having a wavelength routing function;
While performing the discovery method described in the first to third embodiments, while selecting the wavelength of the discovery signal so that the discovery signal arrives in sequence at a specific subscriber home device 71 or a specific subscriber home device 71 group A communication control function for transmitting and receiving optical signals using a plurality of signal wavelengths between the station-side device 70 and another subscriber home device 71 or another subscriber home device 71 group;
Is provided.

  The WDM / TDM-PON 302 includes an optical transmission path 75 in which a station-side optical signal transmission / reception device 70, a subscriber home optical signal transmission / reception device 71-x, a circulating AWG 72, and a plurality of power splitters 73-x are connected in multiple stages. The revolving AWG 72 is a device having the wavelength routing function.

  The station-side optical signal transmitter / receiver 70 is composed of an optical transmitter 701-x, an optical receiver 702-x, a filter 703-x, and a spectrometer 704-x that separates transmitted light and received light. x, a control unit 705, and a power splitter 706. The subscriber home optical signal transmission / reception device 71-x includes an optical transmitter 711-x, an optical receiver 712-x, a wavelength tunable filter 713-x, a spectroscope 714-x, and a controller 715-x. Control units (705, 715) are the communication control function.

  The WDM / TDM-PON 302 transmits a discovery signal at an arbitrary wavelength from the optical transmitter 701-i of the station side optical signal transmitter / receiver 70-i designated by the control unit 705 of the station side optical signal transmitter / receiver 70, and newly The control unit 715-j of the subscriber optical signal transmitter / receiver 71-j connected to the network dynamically sets the transmission center wavelength and the transmission wavelength band of the wavelength tunable filter 713-j at a time interval equal to or longer than the OLT discovery signal transmission cycle. By changing, a discovery signal with an unknown arbitrary wavelength is received.

  In the WDM / TDM-PON 302, signals of a plurality of wavelengths transmitted from the station-side optical signal transmission / reception device 70 are transmitted to each PON branch connected to the subscriber side of the circulating AWG 72 by the wavelength routing function of the circulating AWG. It is transmitted as a signal for each wavelength. Therefore, unlike the WDM / TDM-PON 301 in FIG. 6, the control unit 705 of the station side optical signal transmission / reception apparatus 70 transmits another discovery signal to an arbitrary optical signal transmission / reception unit 701-i. There is no need to stop transmission of discovery signals or data signals from the station-side optical signal transmitter-receiver 70-y with adjacent wavelength slots -x (x ≠ i).

  The WDM / TDM-PON 302 expands and contracts the transmission wavelength band of the wavelength tunable filter 713-j of the subscriber home optical signal transmitter / receiver 71-j without stopping signal transmission from other optical signal transmitters during discovery signal transmission. Even in this case, signals of a plurality of wavelengths are not received simultaneously. However, the control unit 705 selects the station-side optical signal transmitter according to the wavelength routing function of the WDM / TDM-PON using the recursive AWG and the wavelength so that the discovery signal reaches all the PON branches. Need to be assigned.

[3] WDM / TDM-PON using optical switches
FIG. 8 is a diagram for explaining a WDM / TDM-PON 303 using an optical switch.
The WDM / TDM-PON 303 includes a station side optical signal transmission / reception device 80, a subscriber home optical signal transmission / reception device 81-x, and an optical transmission path 85 in which a plurality of optical switches 82-x and a plurality of power splitters 83-x are connected in multiple stages. Is provided. The optical switch 82-x is a device having the wavelength routing function.

  Similarly to the WDM / TDM-PON 302 in FIG. 7, the WDM / TDM-PON 303 also has a single wavelength optical signal for each PON branch connected to the subscriber side of the optical switch 82-x by the wavelength routing function. Only sent. The control unit (805, 815) is the communication control function.

  Therefore, in the station side optical signal transmitting / receiving apparatus 80, the control unit 805 determines the transmission wavelength so that the discovery signal is transmitted to each PON branch connected to the subscriber side from the optical switch 82-x, and In the device 81-x, the discovery signal can be searched at high speed by extending the transmission wavelength band of the wavelength tunable filter.

[Appendix]
The following describes the discovery method and optical transmission system of the present embodiment.

(1): An optical transmission system that includes a single station side device and a plurality of subscriber home devices, and transmits and receives optical signals using a plurality of wavelengths, from the station side device to the subscriber home device. Discovery in a subscriber home device characterized by searching for a discovery signal by changing a transmission wavelength band and a transmission center band of a signal wavelength received in the subscriber home device when searching for a discovery signal of an arbitrary wavelength transmitted Signal search technique.

(2): The discovery signal search method according to claim 1, in the optical transmission system for setting the wavelength of the data signal using the wavelength information bit string included in the discovery signal frame, from the station side device to the subscriber home device. When transmitting a discovery signal in an arbitrary wavelength slot, signal transmission by other wavelength slots is stopped, and the subscriber premises equipment receives the signals of all the wavelength slots simultaneously by extending the transmission wavelength band. Discovery signal transmission method and discovery signal search method.

(3): The discovery signal search method according to claim 1 in the optical transmission system for setting the wavelength of the data signal by using the wavelength information bit string included in the discovery signal frame, from the station side device to the subscriber home device When transmitting a discovery signal in an arbitrary wavelength slot, signal transmission from the wavelength slot adjacent to the wavelength slot that transmits the discovery signal is stopped according to the transmission wavelength band of the subscriber home device. A discovery signal transmission method and a discovery signal search method characterized by receiving signals of a plurality of wavelength slots simultaneously by extending

(4): The discovery signal search method according to claim 1 in the optical transmission system for setting the wavelength of the data signal based on the wavelength of the discovery signal, wherein the discovery signal is expanded by extending the transmission wavelength band of the subscriber premises equipment. A search method for a discovery signal in a subscriber premises apparatus, characterized in that a transmission wavelength band is contracted and a transmission center band is changed in a subsequent search after searching.

(5): A single station side device and a plurality of subscriber premises devices are connected via a power splitter, transmit / receive optical signals using a plurality of wavelengths, and transmit data signals based on the wavelengths of discovery signals. An optical transmission system for setting a wavelength, wherein when a discovery signal is transmitted from a station side device to a subscriber home device in an arbitrary wavelength slot, all signal transmissions by other wavelength slots are stopped, and the subscriber home device An optical transmission system characterized in that the wavelength slot of the discovery signal transmitted by an arbitrary wavelength is specified at high speed by performing the discovery wavelength search of (4) above.

(6): A single station side device and a plurality of subscriber home devices are connected via an element having a wavelength routing function, transmit / receive an optical signal using a plurality of wavelengths, and set the wavelength of the discovery signal. In addition, in the optical transmission system for setting the wavelength of the data signal, the discovery signal of the single wavelength slot for all the subscriber home devices according to the optical path configuration by the element having the wavelength routing function in the station side device The discovery signal is transmitted so that only the target signal is reached, and the subscriber home device performs the discovery wavelength search of (4) above, thereby identifying the wavelength slot of the discovery signal transmitted by an arbitrary wavelength at high speed. Optical transmission system.

  In the present invention, the WDM / TDM-PON discovery signal search is speeded up by changing the transmission wavelength band and transmission center wavelength of the wavelength tunable filter mounted on the ONU and simultaneously searching for signals in a plurality of wavelength slots.

  Further, the wavelength of the unknown discovery signal is specified by switching the transmission wavelength band and the transmission center wavelength of the ONU wavelength tunable filter at a time interval equal to or longer than the OLT search signal transmission cycle.

  The present invention can search for a discovery signal using an arbitrary wavelength slot used in WDM / TDM-PON. That is, even when the wavelength slot used for the discovery signal is changed due to a failure or maintenance of the OSU, the ONU can receive the discovery signal. Further, since the discovery signal is transmitted by a single wavelength, it is not necessary for all OSUs to be in an activated state when the discovery signal is transmitted.

Each x is an arbitrary integer.
60, 70, 80: Station side optical signal transmitting / receiving apparatus (station side apparatus, OLT)
60-x, 70-x, 80-x: Station side optical signal transmitters / receivers 61-x, 71-x, 81-x: Subscriber home optical signal transmitter / receiver (subscriber home device, ONU)
62, 63-x, 73-x, 83-x: Power splitter 72: Circulating AWG
82-x: optical switches 601-x, 701-x, 801-x: optical transmitters 602-x, 702-x, 802-x: optical receivers 603-x, 703-x, 803-x: filters 604 -X, 704-x, 804-x: spectrometers 605, 705, 805: control units 606, 706, 806: power splitters 611-x, 711-x, 811-x: optical transmitters 612-x, 712- x, 812-x: optical receivers 613-x, 713-x, 813-x: tunable filters 614-x, 714-x, 814-x: spectrometers 615-x, 715-x, 815-x: Control unit

Claims (7)

A discovery method in an optical transmission system comprising a single station side device and a plurality of subscriber home devices and transmitting and receiving optical signals using a plurality of signal wavelengths between the station side device and the subscriber home devices Because
When transmitting discovery signals using any wave slots for the subscriber terminal from the station side device, a predetermined wavelength range including a wavelength of said discovery signals from other wavelength slot in the station side device Stop transmission of optical signals, stop transmission of all signals in the predetermined wavelength range, and include a plurality of signal wavelengths in the transmission wavelength band of a variable wavelength filter that selects a signal wavelength to be received at the subscriber premises equipment And searching for the discovery signal.   The discovery method according to claim 1, wherein the predetermined wavelength range is a range including all signal wavelengths, and the transmission wavelength band is extended to include all signal wavelengths.   2. The discovery method according to claim 1, wherein the discovery signal is searched while moving a center wavelength of the transmission wavelength band of the variable wavelength filter at a wavelength interval corresponding to the transmission wavelength band.   After the discovery signal is detected by the subscriber premises apparatus, the variable wavelength filter performs a two-branch search by dividing the transmission wavelength band into two and setting the band including the discovery signal as a new transmission wavelength band. The discovery method according to claim 1, wherein only the discovery signal is repeated until the discovery signal is transmitted.   The discovery method according to claim 4, wherein the discovery method according to claim 4 is performed after the discovery signal is detected by the discovery method according to claim 2. A single station side device,
A plurality of subscriber home devices;
An optical transmission line connecting the station side device and the subscriber premises device via a power splitter;
A communication control function for performing transmission / reception of optical signals using a plurality of signal wavelengths between the station side device and the subscriber premises device and performing the discovery method according to any one of claims 1 to 5 at a predetermined time; ,
An optical transmission system comprising: A single station side device,
A plurality of subscriber home devices;
An optical transmission line that connects the station side device and the subscriber premises device via a device having a wavelength routing function;
The wavelength at which the discovery signal is transmitted so that the discovery signal arrives in sequence at the specific subscriber home device or the specific subscriber home device group when performing the discovery method according to any one of claims 1 to 5. A communication control function for transmitting and receiving optical signals using a plurality of signal wavelengths between the station side device and the other subscriber home device or other subscriber home device group while selecting a slot ;
An optical transmission system comprising:

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