JP2014121078A - Optical communication network system, and control method of optical communication network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a P2MP discovery method for minimizing burst-like increase of up-link delay time and a jitter in a PON (Passive Optical Network) allowing connection of an ONU (Optical Network Unit) having wide distance difference of 0 to 100 km or the like, and to provide an OLT (Optical Line Terminal) and the ONU for realizing the P2MP discovery method.SOLUTION: An OLT transmits a Discovery GATE according to a standard to an ONU. The ONU transmits a REGISTER_REQ at outputting time calculated according to self-connection distance. The OLT receives all REGISTER_REQs during a Discovery Window of time of conventional degree or shorter than the conventional degree. Thereby, burst-like increase of delay time and a jitter can be minimized.

Description

  The present invention relates to a network system for connecting a plurality of subscriber termination devices and a single station side communication device in a PON (Passive Optical Network) topology. The present invention relates to a method for detecting a new connection terminal in PON.

  A PON in which an OLT (Optical Line Terminal) and an ONU (Optical Network Unit) communicate with each other using an Ethernet (registered trademark) frame is called an EPON (Ethernet (registered trademark) PON), and among them, a transmission rate is 1 Gbps. -PON (Gigabit Ethernet (registered trademark) PON) is widely used especially in Japan because it can provide a fast and inexpensive FTTH service.

  Recently, a standard specification of 10G-EPON having a transmission rate increased to 10 Gbps has been studied. In the standard specification of 10G-EPON, it is considered that ONUs 21 having different transmission rates of 10 Gbps and 1 Gbps are mixedly connected to the OLT 11 as shown in FIG.

  In recent years, studies have been made on optical repeaters for PON, and it has become possible to extend the reach of optical signals. Specifically, the connection distance can be set to 100 km, while the connection distance of 20 km or less is often used so far because of the limitation of the reach of the optical signal.

  In general, in PON, the direction of communication from the OLT 11 to the ONU 21 is referred to as a downlink direction, and the opposite direction is referred to as an uplink direction. The wavelength range used by 10G and 1G is shown in FIG. The downstream communication uses different wavelength bands, and the upstream direction uses overlapping wavelength bands.

  In many PONs including GE-PON, uplink communication is performed by time division multiple access. By controlling the transmission timing of each ONU 21 by the OLT 11, a plurality of ONUs can perform time division communication with the OLT 11. Similarly, 10G-EPON uplink communication is performed by time division multiple access. In 10G-EPON, a method in which a plurality of ONUs 21 having different uplink transmission rates can be connected to one OLT 11 is being studied. At this time, uplink communication is realized by time division multiple access even between ONUs 21 of different speeds.

  In many PONs in which upstream communication is performed by time division multiple access, in order to use the upstream bandwidth efficiently, the length of time during which upstream communication is permitted for each ONU 21 is set according to the communication status. A dynamic bandwidth allocation function that dynamically changes in response to this is provided. Here, the bandwidth is allocated by calculating the transmission permission amount for each ONU 21 and exclusively securing the transmission time zone. Since the ONU 21 transmits uplink data only in the time zone assigned by the OLT 11, the time waiting for the assigned time zone is added to the transmission delay time.

  In EPON, a protocol called MPCP (Multi Point-Control Protocol) for the OLT 11 to control communication of a plurality of ONUs 21 is defined as a standard. MPCP includes Discovery Processing for detecting the unauthenticated ONU 21 and REPORT Processing and GATE Processing for controlling the transmission timing of the upstream signal of the ONU 21 (see, for example, Non-Patent Document 1).

  In EPON, when the ONU 21 is connected to the PON, the OLT 11 automatically discovers the ONU 21 and assigns an LLID to the ONU 21 to automatically establish a communication link. This function is called P2MP discovery (Point to multi-point Discovery). MPCP's Discovery Processing is a protocol for realizing P2MP discovery. A sequence diagram of Discovery Processing is shown in FIG.

First, the OLT 11 transmits a GATE frame storing Discovery Information (hereinafter, Discovery GATE) to all ONUs 21 (step S301). ONU21 unregistered in OLT11 receives the Discovery GATE, wait a random waiting time _{T R} for collision avoidance, and transmits the REGISTER_REQ frame (step S302). The OLT 11 opens the Discovery Window only for a time during which REGISTER_REQ from the ONU 21 having the longest expected RTT (Round Trip Time) can be received, and receives REGISTER_REQ from all the ONUs 21 (step S302).

The length of the Discovery Window is common to most maximum value far to might be connected to the RTT of ONU21 can take _{T R (T RWUL)} a value obtained by adding. In response to the received REGISTER_REQ, the OLT 11 notifies the LLID (Logical Link. ID) that is the identification number of the ONU 21 (or UNI port) by the REGISTER frame (step S303).

  Subsequently, the OLT 11 notifies the upstream transmission permission timing of the ONU 21 by the GATE frame (step S304), and the ONU 21 returns REGISTER_ACK according to the notified permission (step S305). P2MP discovery is realized by these processes.

  Here, the ONU 21 that has already been registered cannot perform uplink transmission during the time period of the Discovery Window. As described above, in the upstream communication of EPON, the OLT 11 calculates and notifies the transmission permission amount to each ONU 21, and exclusively secures the transmission time zone. Since there is a possibility that an upstream signal (REGISTER_REQ) from the unregistered ONU 21 arrives during the Discovery Window time zone, upstream transmission of the registered ONU 21 is not permitted in order to avoid signal collision.

IEEE std 802_3-2008sec5_Access. pdf (P264, 265) Nakamura et al., “Proposal of Simple Eye Monitor Method for Electric Dispersion Compensation”, 2007 IEICE Society Conference

  When an associated P2MP discovery is performed in an EPON that allows connection of a long-distance ONU 21 such as 100 km, REGISTER_REQ from a long-distance ONU 21 such as 100 km and REGISTER_REQ from a short-distance ONU 21 such as 0 km are collectively received. Therefore, the time period for opening the Discovery Window for a long time becomes longer, and the upstream delay time and delay time fluctuation (hereinafter referred to as jitter) increase in a burst manner.

Generally, in a communication system, it can be said that the shorter the data communication delay time, the better the performance. It can also be said that the smaller the jitter, the better the performance. If the propagation speed of light in a general optical fiber is about V _f = 2.0 · 10 ⁸ km / s, for example, an RTT with a connection distance of 20 km is about 200 μs, whereas an RTT with a 100 km is about 1000 μs. It is. If T _RWUL is _set to 200 μs, the length of the _{discovery window} is ₁₂₀₀ μs for a maximum connection of 100 km, compared to 400 μs for a maximum connection of 20 km.

  This value is added to the delay time of all ONUs 21 at every P2MP discovery process. The average uplink delay time of EPON up to the conventional maximum 20 km connection is 1000 μs or less to 1500 μs or less. If the average delay time of EPON is set to 1000 μs, the delay time of about 1200 μs is added to the delay time of about 1000 μs every time the P2MP discovery process is performed, and it suddenly (burst) increases more than twice. The degree is great.

  The present invention relates to a P2MP discovery method for minimizing the burst delay increase in uplink delay time and jitter in a PON that allows connection of ONUs having a wide distance difference such as 0 to 100 km, and an OLT for realizing the P2MP discovery method. The purpose is to provide ONU.

  In order to achieve the above object, according to the present invention, the OLT 11 transmits a Discovery GATE to the ONU 21 as standard, the ONU 21 transmits REGISTER_REQ at the transmission time calculated according to its connection distance, and the OLT 11 By receiving all REGISTER_REQ during a discovery window of a degree or shorter time than conventional, bursty increase in delay time and jitter can be minimized.

Specifically, the optical communication network system according to the present invention is:
An optical communication network system in which a parent node and a plurality of child nodes are connected by an optical transmission line,
The child node has a registration request notification function for notifying the parent node of a registration request to the parent node at a timing according to the distance to the parent node,
The parent node has a registration request notification reception function for receiving the registration request notified by the registration request notification function in a predetermined reception time frame.

Specifically, the control method of the optical communication network system according to the present invention is:
A control method of an optical communication network system in which a parent node and a plurality of child nodes are connected by an optical transmission line,
A registration request notification procedure for notifying the parent node of a registration request to the parent node at a timing according to the distance from the parent node to the child node;
A registration request notification reception procedure for receiving the registration request notified in the registration request notification procedure from a child node in a predetermined reception time frame;
Have

Since the optical communication network system registration request notification function according to the present invention is provided, the child node can notify the registration request to the parent node at a timing according to the distance from the parent node.
Since the optical communication network system according to the present invention has a registration request notification receiving function, the parent node can open a reception time frame only in a time zone where a registration request may arrive.
Accordingly, it is possible to minimize the burst-like increase in delay time and jitter in uplink communication.

In the present invention, the parent node further includes a detection optical signal transmission function for transmitting two detection optical signals having different wavelengths to the child node,
The registration request notification function detects a wavelength difference and a delay difference between two detection optical signals, and calculates a distance from the parent node to the child node using the wavelength difference and the delay difference between the two detection optical signals. Also good.

In the present invention, the parent node further includes a detection optical signal transmission function for transmitting a detection optical signal having a predetermined wavelength to the child node,
The registration request notification function may estimate a chromatic dispersion amount using a degree of deterioration of the waveform of the detection optical signal, and calculate a distance from the parent node to the child node using the estimated chromatic dispersion amount.

In the present invention, the child node further includes a detection optical signal transmission / reception function for transmitting the detection optical signal of the non-communication wavelength to the parent node and receiving the detection optical signal from the parent node,
The parent node further includes a detection optical signal reflection function for reflecting the detection optical signal to the child node,
The registration request notification function is from the detection optical signal transmission time in the detection optical signal transmission / reception function to the arrival time of the detection optical signal reflected to the child node by the detection optical signal reflection function. The distance between the parent node and the child node may be calculated using time.

In the present invention, the parent node further includes a detection optical signal transmission function for transmitting the detection optical signal storing the transmission time to the child node,
The registration request notification function calculates a distance between a parent node and a child node using a time from a transmission time stored in the detection optical signal to an arrival time of the detection optical signal at a child node. Also good.

In the present invention, the parent node further includes a detection optical signal transmission function for transmitting the detection optical signal to the child node,
The registration request notification function may measure a signal intensity of the detection optical signal and calculate a distance from the parent node to the child node using an optical attenuation factor of the detection optical signal.

  The predetermined reception time frame in the registration request notification reception function is a time obtained by adding a waiting time for collision avoidance to a transmission delay time of a child node that may be connected at the farthest distance from the parent node. It may be a shorter time.

  The above inventions can be combined as much as possible.

  According to the present invention, there is provided a method for shortening a discovery window length in which an OLT is available when performing ONU discovery processing over a wide range of connection distances. As a result, a burst-like increase in the upstream delay time can be prevented.

An example of a 10G-EPON configuration is shown. An example of the structure of 10G-EPON wavelength arrangement is shown. An example of the operation | movement of a standard Discovery Processing sequence is shown. An example of the configuration of 10G-EPON according to the present invention will be shown. It is a table | surface which shows an example of the connection distance of each ONU which concerns on this invention. It is a table | surface which shows an example of a response | compatibility with the connection distance which concerns on this invention, and a connection distance range management number. It is a table | surface which shows an example of a response | compatibility of the connection distance of each ONU which concerns on this invention, and a connection distance range management number. 5 is a flowchart illustrating an example of an operation of an intermittent extended P2MP discovery process according to the present invention. 6 shows an example of a sequence operation of an extended P2MP discovery process according to the present invention. It is a table | surface which shows an example of the format of the Discovery GATE frame which concerns on this invention. The structural example of the ONU receiving part structure (pattern 1) which concerns on Embodiment 2 is shown. The structural example of the ONU receiving part structure (pattern 2) which concerns on Embodiment 2 is shown. An example of the connection distance detection frame which concerns on Embodiment 2 is shown. An example of operation | movement of the connection distance detection sequence which concerns on Embodiment 2 is shown. 10 is a table showing an example of correspondence between connection distances and connection distance range management numbers according to the second embodiment. The structural example of the ONU receiving part structure (pattern 3) which concerns on Embodiment 3 is shown. The structural example of the ONU receiving part structure (pattern 4) which concerns on Embodiment 3 is shown. The structural example of ONU structure (pattern 5) which concerns on Embodiment 4 is shown. The structural example of the OLT structure (pattern 5) which concerns on Embodiment 4 is shown. An example of the PON section splitter structure which concerns on Embodiment 6 is shown.

  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.

  An optical communication network system according to the present invention is an optical communication network system connected to a parent node by a plurality of child nodes. The child node has a registration request notification function for notifying the parent node of a registration request to the parent node at a timing corresponding to the distance to the parent node. The parent node has a registration request notification reception function for receiving the registration request notified by the registration request notification function in a predetermined reception time frame.

The control method of the optical communication network system includes a registration request notification procedure and a registration request notification reception procedure in this order.
In the registration request notification procedure, the registration request notification function notifies the parent node of a registration request to the parent node at a timing corresponding to the distance from the parent node to the child node.
In the registration request notification reception procedure, the registration request registration request notification reception function receives the registration request notified by the registration request notification function in a predetermined reception time frame.

(Embodiment 1)
In the present embodiment, the child node stores a distance to the parent node in advance.

  As an example, FIG. 4 shows the configuration of a PON system that performs P2MP discovery processing according to the present invention. All ONUs (1) to (5) are connected to the OLT 11 via an optical fiber, and registration processing by P2MP discovery has not been performed yet. Suppose that it is necessary to register. Moreover, the connection distance of each ONU21 is shown in FIG.

  The OLT 11 and each ONU 21 are connected via an optical fiber and an optical splitter at a distance shown in FIG. A PON optical amplifier may be inserted according to the distance. Whether or not an optical amplifier is inserted does not affect the present invention. As an example, assume that the OLT 11 is set to allow a connection distance of up to 100 km.

  A rough connection distance is input to each ONU 21 in advance. Specifically, based on the correspondence table as shown in FIG. 6, it is input in advance that the connection distance range shown in FIG. 7 is connected. In FIG. 6, as an example, the granularity of distance range management is 20 km.

  In the present invention, P2MP discovery is intermittently and collectively performed for all ONUs 21 within the allowable connection distance range. The process of collectively performing P2MP discovery of ONUs 21 with a wide range of connection distances provided in the present invention is hereinafter referred to as an extended P2MP discovery process. FIG. 8 shows the procedure. The OLT 11 performs the extended P2MP discovery process every preset time Tth.

  The OLT 11 has a counter that counts the interval interval of the extended P2MP discovery process, and this value is set as Tcount. The extended P2MP discovery process is executed only when the value of Tcount exceeds Tth (step S501). Tres indicates the Tcount granularity, and this value is not particularly limited.

  Next, details of the extended P2MP discovery process will be described. FIG. 9 shows a sequence of the extended P2MP discovery process. This is a sequence when ONUk (k is an ONU identification number) performs extended P2MP discovery. Control messages to be transmitted / received are the same as those specified in the standard.

OLT11 All ONU21 standard Discovery GATE message at time _{t 0} is transmitted to the receivable broadcast MAC address (step S602). The format of the Discovery GATE message is shown in FIG.

In FIG. 10, the T _RWUL is notified by the Grant # 1 Length field of the Discovery GATE, but the T _RWUL may set fixed values in the ONU 21 and the OLT 11 in advance (step S602). When the OLT 11 notifies, TR _RWUL may be a variable length, and this value may be set based on the number of connected _devices . When a fixed value is set in the ONU 21 and the OLT 11 in advance, the length of the Discovery Window may be stored in the Grant # 1 Length field. However, the frame format is set in advance as a protocol so that the ONU 21 can correctly read the frame format.

After receiving Discovery GATE, ONU _k receives Random Wait Time Start Time (for firstEST ONU) = t ₁ described in Discovery GATE, and adds time adjustment time T _Wk according to its connection distance to time T ₂ REGISTER_REQ is transmitted at random timing during T _RWUL (step S603).

In order to receive REGISTER_REQ, the OLT 11 continues the REGISTER_REQ reception waiting state by opening the Discovery Window from time t _sj to t _ej (length L _Dj ). During the time period when the Discovery Window is opened, the OLT 11 does not permit upstream communication from all the ONUs 21 for which the P2MP discovery process has already been completed. The OLT 11 calculates t _sj , t _ej , and L _Dj as follows.

The maximum value of the connection distance range of the ONU 21 is D _m [m], and the maximum value of the connectable distance is D _M [m]. Here, since RTT (RTT (D)) of the distance D [m] is obtained by the equation (1),
(Equation 1)
RTT (D) = 2 × D / V _n (1)

Here, V _n is the propagation speed of light in the optical fiber, and is calculated from the refractive index of the optical fiber and the wavelength of the light. In this embodiment, the propagation speed of light in the fiber is calculated as 2.0 × 10 ⁸ m / s. The start time t _sj of the Discovery Window is obtained by Expression (2).
(Equation 2)
t _sj = t ₁ + RTT (D _M ) (2)

Next, t _{ej is obtained} by equation (3).
(Equation 3)
t _ej = t _sj + T _RWUL + RTT (D _m ) / 2 (3)

Next, a method in which the ONU _k obtains the timing adjustment time T _wk according to its own connection distance will be described. Assuming that the minimum value of the connection distance range to which the ONU 21 belongs is D _mink [m], Twk is obtained by Expression (4).
(Equation 4)
T _wk = t ₁ + RTT (D _mink ) (4)

  By the above method, the OLT 11 can open the Discovery Window only in a time zone where the REGISTER_REQ may arrive, and the ONU 21 can calculate the REGISTER_REQ transmission timing according to the connection distance. The subsequent processing is not limited in the present invention. In this embodiment, the process proceeds as standard.

(Embodiment 2)
In the present embodiment, the parent node further includes a detection optical signal transmission function for transmitting two detection optical signals having different wavelengths. The registration request notification function detects the wavelength difference and the delay difference between the two detection optical signals, and calculates the distance from the parent node to the child node using the wavelength difference and the delay difference between the two detection optical signals.

  As a second example, a method in which each ONU detects and stores its own connection distance range is different from that in the first embodiment. Other methods are the same as those in the first embodiment. In the present embodiment, the ONU 21 detects a speed difference between two different wavelengths emitted from the OLT 11 and shows a method of estimating a connection distance to the OLT 11 from this speed difference.

Assume that the OLT 11 includes downlink transmitters in two different wavelength ranges (λ ₁ , λ ₂ ). If 10G-EPON can accommodate 1G-ONU 24, it has two different wavelength downstream transmitters for 1G (1480-1500 nm) and 10G (1575-1580 nm), so we will use this. .

FIG. 11 shows the configuration of the ONU receiving unit (pattern 1) according to this embodiment. The ONU 21 includes an ONU control unit 22, a reception frame reading unit 33, O / E conversion units 42-1 and 42-2, and a wavelength multiplexer / demultiplexer 31. The wavelength multiplexer / demultiplexer 31 receives two detection optical signals (λ ₁ , λ ₂ ) having different wavelengths from the OLT 11, demultiplexes the detection optical signals into wavelengths λ ₁ and λ ₂ , and an O / E conversion unit. The detection signal of wavelength λ ₁ is output to 42-1 and the detection optical signal of wavelength λ ₂ is output to O / E converter 42-2. Each of the O / E conversion units 42-1 and 42-2 performs O / E conversion on the detection optical signal and outputs it to the received frame reading unit 31 of the ONU control unit 22. The reception frame reading unit 31 reads the transmission time and the reception time of the detection optical signal, and estimates the distance from the OLT to the ONU.

FIG. 12 shows the configuration of the ONU receiving unit (pattern 2) according to this embodiment. The ONU 21 includes an ONU controller 22, a received frame reader 31, O / E converters 42-1 and 42-2, a connection distance detector 34, and a wavelength multiplexer / demultiplexer 31. The wavelength multiplexer / demultiplexer 31 receives the detection optical signal from the OLT 11, demultiplexes the detection optical signal into λ ₁ and λ ₂ , and sends the detection optical signal with the wavelength λ ₁ to the O / E converter 42-1. The optical signal for detection of wavelength λ ₂ is output to the O / E converter 42-2. Each of the O / E conversion units 42-1 and 42-2 performs O / E conversion on the detection optical signal, and outputs it to the reception frame reading unit 31 and the connection distance detection unit 34 of the ONU control unit 22. The connection distance detection unit 34 reads the transmission time and the reception time of the detection optical signal, and estimates the distance from the OLT to the ONU.

  In pattern 1, the reception frame reading unit 31 reads the detection optical signals of both wavelengths and estimates the connection distance. In pattern 2, after the connection distance is estimated by the connection distance detection unit 34, the estimated connection distance information is transmitted to the ONU control unit 22. In either configuration, the object of the present invention can be achieved. Therefore, which configuration is selected may be selected depending on the configuration of the ONU controller 22.

The OLT 11 transmits a connection distance detection frame as shown in FIG. 13 to all ONUs 21 in two different wavelength ranges (λ ₁ , λ ₂ ). The frequency may be arbitrary, but is transmitted at the same frequency as the distance range limited P2MP discovery process.

  The conditions of the connection distance detection frame are that the Destination Address is addressed to all ONUs 21 (Broadcast Address), the time stamp of the transmission timing from the OLT 11 is described, and the transmission wavelength information is described. . The transmission wavelength may be estimated based on the received waveform when the modulation frequency varies depending on the wavelength, such as 10G-EPON. In this case, the description of the wavelength information in the connection distance detection frame can be omitted. Further, since the extended Discovery GATE in FIG. 10 is addressed to all the ONUs 21 and includes a time stamp, if the wavelength information is added or the ONU 21 estimates the wavelength based on the waveform, the extended Discovery GATE is connected to the connection distance detection frame. Is available as

  When the ONU 21 receives connection distance detection frames of two different wavelengths, the ONU 21 estimates the connection distance from the time stamp value and arrival time. A method for estimating the connection distance will be described in detail. FIG. 14 shows a connection distance detection sequence.

The wavelength used by ONUk for receiving the downlink main signal is λ ₁ . The OLT 11 transmits connection distance detection frames in the wavelength bands of λ ₁ and λ ₂ at times t ₀ and t ₁ , respectively. The connection distance detection frames in the wavelength bands of λ ₁ and λ ₂ are sent alternately. First ONUk has set the time on the timestamp of the connection distance detection frame sent by lambda _1. Next, determine the time t _{1 ',} which has received the connection distance detection frame sent by OLT time t ₁ to lambda _2, the difference Delta] t ₁ and t ₁ tailored to lambda ₁ of the connection distance detection frame.

In the present embodiment, the center wavelengths of the two downstream wavelengths λ ₁ and λ ₂ are 1490 nm and 1580 nm. The value of the center wavelength is input to the ONU 21 in advance. At this time, the wavelength difference Δλ = 90 nm. When chromatic dispersion D [ps / nm · km] is assumed, the actual delay difference Δt ₁ ′ is expressed by Expression (5).
(Equation 5)
Δt ₁ ′ (l) = D × Δλ × l (5)

l is the fiber length, that is, the connection distance of the ONU 21. The value of D is determined in advance according to the wavelength dispersion characteristic of the optical fiber to be used. If this inverse function is obtained, the connection distance can be calculated from Δt ₁ ′.

(Equation 6)
l (Δt ₁ ′) = Δt ₁ ′ / (D × Δλ) (6)

In this embodiment, D is set to a general chromatic dispersion value of 16 ps / nm / km. From Equation (6), the value of the connection distance l is Equation (7).
(Equation 7)
l (Δt ₁ ′) = Δt ₁ ′ [ns] / {(16 ps / nm / km) × 90 nm)} (7)

Time granularity of ONU21 the TQ (= 16 ns) since, if Delta] t ₁ is 0TQ, 'the range of 0 ≦ Δt _1' Δt ₁ as <16 [ns], the connection distance range of l 0 ≦ l <12 [ km]. Similarly, if 1TQ, the range of Δt ₁ ′ can be estimated as 12 ≦ l <22 [km]. Similarly, it is possible to estimate the subsequent distance range.

  In this embodiment, the correspondence between the connection distance and the connection distance range management number is set as shown in FIG. 15 according to the granularity of the connection distance estimation. )

  The ONU 21 obtains and holds its own connection distance range management number based on FIG. 15 and the estimated connection distance range value, and performs the same processing as in the first embodiment based on this value. This makes it possible to execute the extended P2MP discovery process without inputting the connection distance to the ONU 21 in advance.

(Embodiment 3)
In this embodiment, the parent node further includes a detection optical signal transmission function for transmitting a detection optical signal having a predetermined wavelength. The registration request notification function estimates the chromatic dispersion amount using the degree of deterioration of the waveform of the detection optical signal, and calculates the distance from the parent node to the child node using the estimated chromatic dispersion amount.

  As a third example, a method in which each ONU 21 detects and stores its own connection distance range is different from the first and second embodiments. Other methods are the same as those in the first embodiment.

  In the present embodiment, the ONU 21 shows a method of detecting the chromatic dispersion degree of the signal emitted from the OLT 11 and estimating the connection distance to the OLT 11 from the chromatic dispersion degree. Since the OLT 21 includes at least one downlink transmitter, this is used.

  FIG. 16 shows the configuration of the ONU receiving unit (pattern 3) according to this embodiment. The ONU 21 includes an ONU controller 22, a received frame reader 33, an O / E converter 42-1, a connection distance detector 34, and a wavelength multiplexer / demultiplexer (wavelength filter) 35. The wavelength multiplexer / demultiplexer (wavelength filter) 35 reads the detection optical signal from the OLT 11 and outputs the detection optical signal to the O / E converter 42-1. The O / E conversion unit 42-1 performs O / E conversion of the detection optical signal and outputs it to the reception frame reading unit 31 and the connection distance detection unit 34 of the ONU control unit 22. The connection distance detection unit 34 reads the waveform of the detection optical signal and calculates the distance from the OLT to the ONU from the chromatic dispersion amount of the signal.

  FIG. 17 shows the configuration of the ONU receiving unit (pattern 4) according to this embodiment. The ONU 21 includes an ONU control unit 22, a reception frame reading unit 33, a dispersion compensation unit 36, and an O / E conversion unit 42-1 wavelength multiplexer / demultiplexer (wavelength filter) 35. The wavelength multiplexer / demultiplexer (wavelength filter) 35 reads the detection optical signal from the OLT 11 and outputs the detection signal to the O / E converter 42-1. The O / E conversion unit 42-1 performs O / E conversion of the detection optical signal and outputs it to the dispersion compensation unit 36. The dispersion compensator 36 estimates the chromatic dispersion amount of the detection optical signal. The reception frame reading unit 33 calculates the distance from the OLT to the ONU using the chromatic dispersion amount.

  In pattern 3, the connection distance detection unit 34 estimates the chromatic dispersion amount of the signal, and estimates the connection distance from the chromatic dispersion amount. In the pattern 4, when the dispersion compensation unit 36 is provided, the dispersion compensation unit 36 estimates the chromatic dispersion amount of the signal, and thus the connection distance is estimated from this value. As long as the amount of chromatic dispersion can be monitored, the object of the present invention can be achieved in either configuration.

  The OLT 11 always transmits a downstream continuous signal. The ONU 21 estimates the chromatic dispersion amount of the received downlink signal. In this embodiment, as a simple estimation method of the chromatic dispersion amount, the degree of waveform deterioration is detected by three sets of comparators and a low pass filter (LPF), and the degree of waveform deterioration and the amount of chromatic dispersion correspond one-to-one. Estimate the amount of chromatic dispersion. After that, as in the second embodiment, the connection distance can be calculated from the wavelength distribution of the OLT transmitter, the estimated chromatic dispersion amount, and the chromatic dispersion D of the fiber (for example, see Non-Patent Document 2).

  Thereafter, the same processing as in the second embodiment is performed. This makes it possible to execute the extended P2MP discovery process without inputting the connection distance to the ONU 21 in advance.

(Embodiment 4)
In this embodiment, the child node further includes a detection optical signal transmission / reception function for transmitting a detection optical signal having a non-communication wavelength to the parent node and receiving the detection optical signal from the parent node. The parent node further includes a detection signal reflection function for reflecting the detection optical signal to the child node. The registration request notification function uses the time from the transmission time of the detection optical signal in the detection optical signal transmission / reception function to the arrival time of the detection optical signal reflected to the child node by the detection optical signal reflection function. To calculate the distance between the parent node and the child node.

  As a fourth example, a method in which each ONU 21 detects and stores its own connection distance range is different from those in the first, second, and third embodiments. Other methods are the same as those in the first embodiment.

  In this embodiment, the ONU 21 transmits a connection distance detection optical signal of a non-communication wavelength, reflects the connection distance detection optical signal on the OLT 11 side, and the ONU 21 detects the reflection signal and uniquely determines its propagation delay time. RTT is acquired at the same time, and the connection distance is calculated. FIG. 18 shows the configuration of the ONU (pattern 5) according to this embodiment. The ONU 21 includes an ONU control unit 22, a connection distance estimation unit 35, an optical transmission unit 51, E / O conversion units 52-1, 52-2, an optical reception unit 41, and an O / E conversion unit 42-2. 42-3, a power splitter or circulator 61, and a wavelength multiplexer / demultiplexer (wavelength filter) 35. FIG. 19 shows the configuration of the OLT (pattern 6) according to this embodiment. The OLT 11 includes an OLT control unit 12, an optical transmission unit 53, an E / O conversion unit 54, an optical reception unit 43, an O / E conversion unit 44, a wavelength multiplexer / demultiplexer (wavelength filter) 35, And a reflection unit 71.

The ONU 21 is configured as shown in FIG. 18, and the ONU 21 that has not undergone P2MP discovery has a connection distance detection light at a wavelength λ3 different from the communication wavelength and at an interval T _int that is approximately P2MP discovery interval T _th for each distance. Send a signal. Here, it is a condition that the identification information (MAC address or the like) of the outgoing ONU is described in the connection distance detection optical signal.

The ONU 21 records the transmission time of the connection distance detection optical signal or stores the time stamp at the time of transmission in the connection distance detection optical signal. T _int is a random value with a certain interval or more between them, in order to prevent collision between the plurality of ONUs 21. For example, it calculates | requires like Formula (8).
(Equation 8)
T _int = {α + 2 (1−α) R} T _th (8)

  Here, α is a ratio for determining the minimum interval, and R is a random value that has a uniform distribution in the range of 0 to 1. The OLT 11 is configured as shown in FIG. 19, and the connection distance detection optical signal is reflected as it is by the reflection unit and returned to the ONU 21. The ONU 21 reads the ONU identification information of the connection distance detection optical signal (reflected light), and discards signals other than those transmitted from the own ONU 21.

When the connection distance detection optical signal (reflected light) is emitted from the own ONU 21, the ONU 21 determines the connection distance l (Δt) from the difference Δt between the arrival time and the transmission time of the connection distance detection optical signal to the OLT 11. Is calculated.
(Equation 9)
l (Δt) = V _n × Δt / 2 (9)

Here, V _n, the light propagation speed of the optical fiber. In the present embodiment, the propagation speed of light in the fiber is calculated as 2.0 × 10 ⁸ m / s.

  Thereafter, the same processing as in the first, second, and third embodiments is performed. This makes it possible to execute the extended P2MP discovery process without inputting the connection distance to the ONU 21 in advance.

(Embodiment 5)
In the present embodiment, the parent node further includes a detection optical signal transmission function for transmitting a detection optical signal storing the transmission time. The registration request notification function calculates the distance between the parent node and the child node using the time from the transmission time stored in the detection optical signal to the arrival time of the detection optical signal at the child node.

  As a fifth example, a method in which each ONU 21 detects and stores its connection distance range is different from those in the first, second, third, and fourth embodiments. Other methods are the same as those in the first embodiment.

The OLT and ONU have a GPS receiver and synchronize time. The OLT transmits a connection distance detection frame (absolute time may be stored in the extended Discovery GATE) storing a time stamp of the transmission time to all ONUs. The ONU calculates the connection distance l (Δt ′) from the difference Δt ′ between the arrival time and the transmission time of the connection distance detection frame according to the equation (10).
(Equation 10)
l (Δt ′) = V _n × Δt ′ (10)

(Embodiment 6)
In the present embodiment, the parent node further includes a detection optical signal transmission function for transmitting a detection optical signal having a predetermined signal strength. The registration request notification function measures the signal intensity of the detection optical signal, and calculates the distance from the parent node to the child node using the difference between the measured signal intensity and the predetermined signal intensity.

  The OLT 11 transmits the detection optical signal to the power splitter 62. The power splitter 62 measures the signal oscillation intensity of the detection optical signal and transmits it to the power splitter 63. The power splitter 63 measures the signal oscillation intensity of the detection optical signal from the power splitter 62 and transmits it to the ONU 21. The ONU 21 calculates the distance from the OLT 11 to the ONU 21 using the difference in signal oscillation intensity between the power splitter 62 and the power splitter 63 of the detection optical signal.

  As a sixth example, a method in which each ONU detects and stores its own connection distance range is different from those in the first, second, third, fourth, and fifth embodiments. Other methods are the same as those in the first embodiment.

In the present embodiment, the receiver of the ONU 21 has a received light intensity measurement function, and the downlink signal reception intensity P _IN [dBm] from the OLT 11 is measured. The downlink signal oscillation intensity P _out [dBm] of the OLT 21 measures the oscillation intensity on the ONU side or measures the oscillation intensity on the OLT side, writes the oscillation intensity in the extended DiscoveryGATE, and notifies the ONU. The splitter configuration is set in advance or is a fixed configuration. From the difference [Delta] P between P _out and _{P IN [dB] (= P} out -P IN), obtains the connection distance l ([Delta] P).

For example, the splitter configuration between OLT and ONU is shown in FIG. If the attenuation factors of the light intensity due to the branching at the power splitter 62 and the power splitter 63 are P _LOS1 [dB] and P _LOS2 [dB], respectively, l (ΔP) is expressed by Equation (11). Here, P _r [dB / km] is an optical attenuation factor per unit distance of the optical fiber.
(Equation 11)
l (ΔP) = {ΔP− (P _LOS1 + P _LOS2 )} / P _r (11)

  Thereafter, the same processing as in the first, second, and third embodiments is performed. This makes it possible to execute the extended P2MP discovery process without inputting the connection distance to the ONU 21 in advance.

  The present invention can be applied to the information communication industry.

11: OLT
12: OLT control unit 21: ONU
22: ONU control unit 31, 35: wavelength multiplexer / demultiplexer 33: received frame reading unit 34: connection distance detection unit 36: dispersion compensation unit 41, 43: optical receiving units 42-1, 42-2, 42-3, 44: O / E converters 51, 53: Optical transmitters 52-1, 52-2, 54: E / O converters 61, 62, 63: Power splitter 71: Optical reflector 81: Lower network 82: Upper network 83: Optical communication path

Claims (8)

An optical communication network system in which a parent node and a plurality of child nodes are connected by an optical transmission line,
The child node has a registration request notification function for notifying the parent node of a registration request to the parent node at a timing according to the distance to the parent node,
The parent node has a registration request notification reception function for receiving the registration request notified by the registration request notification function in a predetermined reception time frame.
Optical communication network system. The parent node further includes a detection optical signal transmission function for transmitting two detection optical signals having different wavelengths to the child node,
The registration request notification function detects a wavelength difference and a delay difference between two detection optical signals, and calculates a distance from the parent node to the child node using the wavelength difference and the delay difference between the two detection optical signals.
The optical communication network system according to claim 1. The parent node further includes a detection optical signal transmission function for transmitting a detection optical signal having a predetermined wavelength to the child node,
The registration request notification function estimates the chromatic dispersion amount using the degree of deterioration of the waveform of the detection optical signal, and calculates the distance from the parent node to the child node using the estimated chromatic dispersion amount.
The optical communication network system according to claim 1. The child node further includes a detection optical signal transmission / reception function for transmitting the detection optical signal of the non-communication wavelength to the parent node and receiving the detection optical signal from the parent node,
The parent node further includes a detection optical signal reflection function for reflecting the detection optical signal to the child node,
The registration request notification function is from the detection optical signal transmission time in the detection optical signal transmission / reception function to the arrival time of the detection optical signal reflected to the child node by the detection optical signal reflection function. Calculate the distance from the parent node to the child node using time,
The optical communication network system according to claim 1. The parent node further includes a detection optical signal transmission function for transmitting the detection optical signal storing the transmission time to the child node,
The registration request notification function calculates a distance between a parent node and a child node using a time from a transmission time stored in the detection optical signal to an arrival time of the detection optical signal at a child node.
The optical communication network system according to claim 1. The parent node further includes a detection optical signal transmission function for transmitting the detection optical signal to the child node,
The registration request notification function measures the signal intensity of the detection optical signal and calculates the distance from the parent node to the child node using the optical attenuation rate of the detection optical signal.
The optical communication network system according to claim 1. The predetermined reception time frame in the registration request notification reception function is a time obtained by adding a waiting time for collision avoidance to a transmission delay time of a child node that may be connected at the farthest distance from the parent node. Is a shorter time,
The optical communication network system according to claim 1. A control method of an optical communication network system in which a parent node and a plurality of child nodes are connected by an optical transmission line,
A registration request notification procedure for notifying the parent node of a registration request to the parent node at a timing according to the distance from the parent node to the child node;
A registration request notification reception procedure for receiving the registration request notified in the registration request notification procedure from a child node in a predetermined reception time frame;
A method for controlling an optical communication network system.

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