JP2018107716A - Optical transmission system and optical transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmission system and an optical transmission method for preventing a transmission delay of an incoming signal from occurring due to an activation period.SOLUTION: An optical transmission system comprises a plurality of termination devices and a terminal station device. The registered termination device comprises a first optical communication part for transmitting a main signal to the terminal station device with a first transmission power, and the unregistered termination device comprises: a transmission power adjustment part for determining a second transmission power value on the basis of a loss of a transmission path; and a second optical communication part for transmitting a control signal via the transmission path to the terminal station device with a second transmission power value, and the terminal station device comprises: a main signal demodulation part for demodulating the main signal obtained on the basis of a comparison result between a reception power value of a power multiplexed signal and a first threshold; a signal separation processing part for separating the control signal from the power multiplexed signal on the basis of a reception power value of the main signal estimated on the basis of a preliminarily measured reception power value of the main signal; and a control signal demodulation part for demodulating the separated control signal on the basis of a comparison result between the reception power value of the control signal and a second threshold.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical transmission system and an optical transmission method.

  In a TDM-PON (Time Division Multiplexing Passive Optical Network) system, an end device (ONU: Optical Network Unit) acquires uplink data from a lower device. Further, the ONU notifies the OLT of a request amount (transmission request amount) of a band for transmitting uplink data to an end station device (OLT: Optical Line Terminal).

  The OLT allocates a transmission band and a transmission time to each ONU based on the transmission request amount notified from each ONU. The OLT notifies each ONU of the allocated transmission band and transmission time. Each ONU transmits a main signal having a data amount that can be transmitted within the notified transmission band to the OLT at the allocated transmission time. Due to the control for notifying the transmission band and the transmission time, a transmission delay of the main signal of the uplink data by the ONU occurs.

  In the TDM-PON system, a transmission delay of an upstream data signal (hereinafter referred to as an “upstream signal”) by the ONU also occurs due to a control signal terminated between the OLT and the ONU. In particular, in a process for registering an ONU not registered in the OLT (hereinafter referred to as “unregistered ONU”) by the OLT (hereinafter referred to as “activation process”), it is newly connected to the OLT via a transmission path. An activation window, which is a window for permitting transmission of an upstream signal only to an unregistered ONU and receiving a control signal, is periodically developed by the OLT (see Non-Patent Document 1).

  Hereinafter, a period during which an activation window for receiving a control signal is expanded (a period for receiving a control signal) is referred to as an “activation period”. Hereinafter, an upstream signal transmitted from the ONU to the OLT during the activation period is referred to as an “activation signal”.

  FIG. 10 is a diagram illustrating an example of transmission delay caused by the activation period. An upstream signal transmitted from the ONU registered in the OLT (hereinafter referred to as “registered ONU”) to the OLT has an upstream signal transmission delay (queuing delay) due to the activation period.

"ITU-T G.989.3", International Telecommunication Union, 2015

  These transmission delays become a problem when a TDM-PON system accommodates a communication system such as a mobile system that has strict requirements for uplink signal transmission delays. In a conventional optical transmission system, a registered ONU queues a main signal during an activation period, and transmits the main signal to the OLT during a period other than the activation period. As described above, the conventional optical transmission system has a problem in that an uplink signal transmission delay may occur due to the activation period.

  In view of the above circumstances, an object of the present invention is to provide an optical transmission system and an optical transmission method that do not cause an upstream signal transmission delay due to an activation period.

  One aspect of the present invention is an optical transmission system including a plurality of termination devices and a terminal device, and the termination device registered in the terminal device transmits a main signal to the terminal device via a transmission line. A transmission power adjusting unit that determines a second transmission power value based on a loss of the transmission path, and a termination optical device that is not registered in the terminal device, A second optical communication unit that transmits a control signal to the terminal device at the second transmission power value via the transmission line, wherein the terminal device is configured such that the main signal and the control signal are power multiplexed. A signal acquisition unit that acquires the received signal, a main signal demodulation unit that demodulates the main signal obtained based on a comparison result between the received power value of the power multiplexed signal and the first threshold, Based on the received power value of the main signal estimated based on the received power value of the main signal. And a signal separation processing unit that separates the control signal from the power multiplexed signal, and a control that demodulates the separated control signal based on a comparison result between the received power value of the control signal and a second threshold value. An optical transmission system having a signal demodulator.

  One aspect of the present invention is the above-described optical transmission system, wherein the terminal device determines whether or not it is a period for receiving the control signal, and other than a period for receiving the control signal. And a terminal station power value monitor for measuring the received power value of the main signal for each of the terminal devices.

  One aspect of the present invention is the optical transmission system described above, wherein the termination device includes a termination device power value monitor that measures a reception power value of a downlink signal transmitted by the terminal device, and a reception power of the downlink signal. And a path loss measuring unit that measures the loss of the transmission path based on the value.

  One aspect of the present invention is the optical transmission system described above, wherein the terminal device further includes a transmission rate correction unit that corrects the transmission rate of the control signal so as to correspond to the transmission rate of the main signal.

  One aspect of the present invention is the above-described optical transmission system, wherein the control signal demodulator updates the second threshold value depending on whether the main signal is included in the power multiplexed signal. .

  One aspect of the present invention is the above-described optical transmission system, wherein the terminal device sends the control signal to the terminal device when a response to the control signal is not obtained from the terminal device within a predetermined time. The transmission power adjustment unit further increases the second transmission power value every time the control signal retransmission unit retransmits the control signal.

  One aspect of the present invention is an optical transmission system including a plurality of termination devices and a terminal device, and the termination device registered in the terminal device transmits a main signal to the terminal device via a transmission line. A transmission power adjusting unit that determines a second transmission power value based on a loss of the transmission path, and a termination optical device that is not registered in the terminal device, A second optical communication unit that transmits a control signal to the terminal device via the transmission line at the second transmission power value, and the terminal device transmits the main signal and the control in a first period. A signal acquisition unit that acquires a power multiplexed signal and acquires the control signal in a second period other than the first period, and a comparison result between a received power value of the power multiplexed signal and a first threshold value A main signal demodulating unit for demodulating the main signal obtained based on the second period, And a control signal demodulator for demodulating the acquired the control signal in an optical transmission system.

  One aspect of the present invention is an optical transmission method executed by an optical transmission system including a plurality of termination devices and a terminal device, wherein the termination device registered in the terminal device is transmitted via a transmission line. The main signal is transmitted to the terminal device with the first transmission power, and the terminal device unregistered with the terminal device determines a second transmission power value based on the loss of the transmission path, and passes through the transmission path. A control signal is transmitted to the terminal device at the second transmission power value, the terminal device acquires a signal in which the main signal and the control signal are power multiplexed, and received power of the power multiplexed signal. Demodulating the main signal obtained based on the comparison result between the value and the first threshold, based on the received power value of the main signal estimated based on the received power value of the main signal measured in advance, Separating the control signal from the power multiplexed signal; and Based on the comparison result between the transmission power value and the second threshold value, and demodulates the separated said control signal, an optical transmission method.

  According to the present invention, it is possible to prevent the transmission delay of the uplink signal from occurring due to the activation period.

It is a figure which shows the example of the activation period in 1st Embodiment. It is a conceptual diagram which shows the example of a structure and operation | movement of an optical transmission system in 1st Embodiment. It is a figure which shows the example of a structure of ONU in 1st Embodiment. It is a figure which shows the example of a structure of the demodulation function part of the upstream signal of OLT in 1st Embodiment. It is a figure which shows the example of the detail of operation | movement of OLT in 1st Embodiment. It is a flowchart which shows the example of operation | movement of ONU in 1st Embodiment. It is a flowchart which shows the example of operation | movement of OLT in 1st Embodiment. It is a figure which shows the example of a structure of the demodulation function part of the upstream signal of OLT in 2nd Embodiment. It is a figure which shows the example of a structure of ONU in 3rd Embodiment. It is a figure which shows the example of the transmission delay resulting from an activation period.

Embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram illustrating an example of an activation period. Regardless of whether or not it is the activation period, the registered ONU transmits the main signal of the upstream signal to the OLT. The unregistered ONU transmits an upstream activation signal to the OLT during the activation period. The OLT does not generate an activation delay, which is an uplink signal transmission delay due to the activation period.

  FIG. 2 is a conceptual diagram illustrating an example of the configuration and operation of the optical transmission system 1. In FIG. 2, the ONU 2-1 as an example of a registered ONU transmits an upstream signal main signal in response to a transmission command from the OLT 4 (step S 100). The OLT 4 measures in advance the reception power value A (light reception power value) of the main signal of the uplink signal during a period other than the activation period (step S101).

  An ONU 2-N (N is an integer of 2 or more) that is an unregistered ONU is referred to as a downstream data signal (hereinafter referred to as a “downstream signal”) of another ONU 2 in order to determine the transmission power of the activation signal of the ONU 2-N. ) Measure the received power value of the main signal. The ONU 2-N estimates the loss of the transmission path (path) between the other ONU 2 and the OLT 4 based on the result of measuring the received power value of the main signal of the downstream signal of the other ONU 2 (step S102).

  The ONU 2 -N is configured so that a power difference of a certain level or more is generated between the reception power value of the upstream signal of the upstream signal of the ONU 2-1 and the reception power value of the activation signal of the upstream signal of the ONU 2 -N. Adjust the transmission power of the activation signal of the -N uplink signal. That is, the ONU2-N considers the activation signal of the ONU2-N upstream signal as noise when the OLT4 demodulates the main signal of the upstream signal of the ONU2-1, so that the OLT4 can demodulate the main signal, The transmission power of the activation signal of the upstream signal of ONU2-N is adjusted. When the ONU 2-N obtains an activation signal transmission command from the OLT 4, the ONU 2-N transmits an activation signal whose transmission power is adjusted to the OLT 4 during the activation period.

  The optical coupler 3 multiplexes the main signal of the upstream signal of the ONU 2-1 and the activation signal of the upstream signal of the ONU 2-N, thereby generating a signal in which the main signal and the activation signal are power multiplexed. To the OLT 4 (step S103).

  In FIG. 2, the OLT 4 obtains a power-multiplexed signal of the main signal of the upstream signal of the ONU 2-1 and the activation signal of the upstream signal of the ONU 2-N (Step S104). The OLT 4 demodulates the main signal by comparing the received power value of the power multiplexed signal and the main signal threshold. The main signal threshold value is determined in advance to a value that can be removed from the power multiplexed signal using the activation signal included in the power multiplexed signal as noise. Therefore, the main signal threshold value is larger than the reception power value of the activation signal included in the power multiplexed signal (step S105). The OLT 4 obtains a result (1 or 0) obtained by binarizing the received power value of the power multiplexed signal as a result of the loss of the received power value information (power intensity information) of the power multiplexed signal. (Step S106).

  The OLT 4 estimates the received power value A ′ of the main signal in the activation period based on the result of previously measuring the received power value A of the main signal in the period other than the activation period (step S <b> 107). The OLT 4 separates the activation signal from the power multiplexed signal. That is, the OLT 4 extracts the activation signal from the power multiplexed signal by subtracting the main signal corrected so that the received power value becomes A ′ from the power multiplexed signal (step S108).

  Hereinafter, the threshold for determining the bit of the activation signal is referred to as “activation signal threshold”. The OLT 4 demodulates the activation signal based on the comparison result between the reception power value of the activation signal and the activation signal threshold (step S109). The OLT 4 may use the demodulated activation signal to measure the round trip time (RTT) between the OLT 4 and the ONU 2.

  FIG. 3 is a diagram illustrating an example of the configuration of the ONU 2. The ONU 2 includes an optical communication unit 20, a power value monitor 21, a path loss measurement unit 22, a transmission power adjustment unit 23, a PON control unit 24, and a BLDD 25 (Burst Laser Diode Driver).

  Some or all of the optical communication unit 20, the power value monitor 21, the path loss measurement unit 22, the transmission power adjustment unit 23, the PON control unit 24, and the BLDD 25 are, for example, a processor such as a CPU (Central Processing Unit). It may be realized by executing a program stored in the storage unit, or may be realized by using hardware such as LSI (Large Scale Integration) or ASIC (Application Specific Integrated Circuit). The ONU 2 may further include a storage device having a nonvolatile recording medium (non-temporary recording medium) such as a magnetic hard disk device or a semiconductor storage device.

  When the local ONU that is an unregistered ONU is newly connected to the OLT 4, the optical communication unit 20 acquires a downlink signal transmitted from the OLT 4 to another ONU 2. The optical communication unit 20 converts a downstream signal that is an optical signal into an electrical signal. The optical communication unit 20 transmits an electric signal based on the downlink signal to the power value monitor 21 or a predetermined functional unit.

  The optical communication unit 20 converts the electrical signal into an upstream signal that is an optical signal. The optical communication unit 20 acquires an injection current from the BLDD 25. The optical communication unit 20 attenuates the uplink signal according to the injected current. The optical communication unit 20 may directly attenuate the upstream signal using an optical attenuator. When the self ONU that is an unregistered ONU is newly connected to the OLT 4, the optical communication unit 20 waits for a random time in the activation period and transmits an activation signal of an upstream signal to the OLT 4.

The power value monitor 21 acquires a downlink signal from the optical communication unit 20. Power value monitor 21 measures the received power value P _r of the acquired downlink signal. The transmission power of the downlink signal is determined in advance. Power value monitor 21, a received power value P _r of the measured downlink signals, and outputs the path loss measurement unit 22.

Path loss measurement unit 22, the received power value P _r of the power value monitor 21 downlink signal, based on the difference between the transmission power value set in advance, the transmission path between the other ONU2 and OLT4 (route) Estimate the loss. Transmission power value _{P d} of a downlink signal OLT4 are known. The path loss measurement result Loss is expressed as shown in Equation (1). The path loss measurement unit 22 transmits information indicating the path loss measurement result Loss to the transmission power adjustment unit 23.

The transmission power adjustment unit 23 acquires information representing the transmission time (transmission timing) of the activation signal from the PON control unit 24. The transmission power adjustment unit 23 acquires information representing the path loss measurement result Loss from the path loss measurement unit 22. Transmission power adjusting unit 23, via the BLDD25, adjusts the transmit power value _{P s} of the activation signal.

When the reception power value P _u of the activation signal in the OLT 4 is a fixed value, the transmission power value P _s of the activation signal in the ONU 2 is expressed as Expression (2).

The transmission power adjustment unit 23 transmits a command signal for adjusting the injection current to the optical communication unit 20 to the BLDD 25 so that the transmission power value P _s of the activation signal becomes equal to the value of Expression (2).

  The PON control unit 24 determines the amount of current (injected current) that the BLDD 25 injects into the optical communication unit 20. The PON control unit 24 notifies the transmission power adjustment unit 23 of information indicating the transmission time of the activation signal. The BLDD 25 injects current into the optical communication unit 20 with an instantaneous response in accordance with control by the PON control unit 24.

  FIG. 4 is a diagram illustrating an example of a configuration of an uplink signal demodulation function unit of the OLT 4. The OLT 4 includes an optical square detection unit 40, a power value monitor 41, an activation signal acquisition unit 42, a main signal demodulation unit 43, an activation signal separation processing unit 44, an activation signal demodulation unit 45, and a PON control. Part 46.

  Some or all of the optical square detection unit 40, the power value monitor 41, the activation signal acquisition unit 42, the main signal demodulation unit 43, the activation signal separation processing unit 44, the activation signal demodulation unit 45, and the PON control unit 46. For example, a processor such as a CPU may be realized by executing a program stored in a storage unit, or may be realized using hardware such as an LSI or an ASIC. The OLT 4 may further include a storage device having a nonvolatile recording medium (non-temporary recording medium) such as a magnetic hard disk device or a semiconductor storage device.

The power value monitor 41 measures the reception power value A of the main signal R _data of the upstream signal that does not include the activation signal R _act for each ONU 2 in a period other than the activation period. The power value monitor 41 records the received power value A of the main signal R _data of the upstream signal in the storage unit of the PON control unit 46.

In the OLT 4, the demodulation of the main signal included in the electrical signal based on the upstream signal and the demodulation of the activation signal included in the electrical signal based on the upstream signal are performed separately. The optical square detection unit 40 converts an upstream signal that is an optical signal into an electrical signal. The optical square detector 40 converts the received optical signal r, which is an optical signal obtained by power-multiplexing the main signal s _data and the activation signal s _act , into an electrical signal. The received optical signal r is expressed as in Equation (3).

Here, h _data represents a channel transfer function of the main signal s _data . h _act represents the channel transfer function of the activation signal s _act . n represents the noise received by the signal in the transmission path (channel) or the communication unit of the OLT 4. The optical square detection unit 40 converts the received optical signal r into an electrical signal as in Expression (4) to Expression (6) when squarely detecting the received optical signal r expressed in Expression (3).

  The optical square detection unit 40 transmits a reception electrical signal R, which is an electrical signal obtained as a result of detection, to the activation signal acquisition unit 42 and the main signal demodulation unit 43.

  The activation signal acquisition unit 42 acquires information indicating whether the activation window is expanded from the PON control unit 46. The activation signal acquisition unit 42 determines that it is the activation period when acquiring information indicating that the activation window is expanded. When the activation signal acquisition unit 42 acquires information indicating that the activation window is not expanded, the activation signal acquisition unit 42 determines that the period is other than the activation period.

  The activation signal acquisition unit 42 interrupts the process when it is a period other than the activation period. The activation signal acquisition unit 42 transmits the received electrical signal R to the activation signal separation processing unit 44 when it is the activation period.

The main signal demodulator 43 demodulates the main signal included in the received electrical signal R. The main signal demodulator 43 demodulates the main signal based on the result of comparison between the received power value of the received electrical signal R and the main signal threshold. Hereinafter, the binary main signal from which the noise component has been removed is referred to as “R _data ^bin ”. The main signal demodulator 43 is a main signal threshold for binarizing the main signal so that the reception power value of the activation signal becomes a noise component compared to the reception power value of the main signal during the activation period. May be updated. The main signal demodulator 43 transmits the demodulated binary main signal R _data ^bin to the activation signal separation processor 44. The main signal demodulator 43 transmits a bit string representing the demodulated main signal to the PON controller 46.

The activation signal separation processing unit 44 acquires the received electrical signal R from the activation signal acquisition unit 42. The activation signal separation processing unit 44 separates the main signal R _data and the activation signal R _act by performing predetermined processing on the received electrical signal R. When the main signal R _data is not included in the received electric signal R, the activation signal separation processing unit 44 transmits the received electric signal R including the activation signal R _act to the activation signal demodulating unit 45.

Activation signal separation processing section 44, if it contains a main signal _{R data} to the received electrical signals R, removing the main signal _{R data} from the received electrical signal R. The activation signal separation processing unit 44 transmits the received electrical signal R including the activation signal R _act , which is the received electrical signal R from which the main signal R _data has been removed, to the activation signal demodulating unit 45. Note that the activation signal separation processing unit 44 may interrupt the process when it is a period other than the activation period.

The activation signal separation processing unit 44 obtains the activation signal R _act by removing the component of the binary main signal R _data ^bin from the received electrical signal R based on the estimated received power value A ′. The activation signal R _act is expressed as shown in Equation (7).

Here, the demodulated binary main signal R _data ^bin is a signal obtained as a result of comparison processing using a main signal threshold. For this reason, the power information (reception power intensity information) of the main signal R _data ^bin is lost. On the other hand, the main signal R _data included in the received electrical signal R retains power information because the comparison process using the main signal threshold is not performed. Therefore, the activation signal separation processing unit 44 estimates the received power value of the main signal R _data before the comparison process using the main signal threshold is performed on the main signal R _data ^bin using the tuning parameters. There is a need to. The tuning parameter α is a parameter for returning the received power value of the main signal R _data ^bin to the received power value A ′.

A method for estimating the received power value A ′ of the main signal R _data will be described. In the TDM-PON system, the OLT 4 manages the transmission time of the uplink signal. The ONU 2 transmits the main signal R _data of the uplink signal with the same transmission power every time. Therefore, the activation signal separation processing unit 44 stores the received power value A of the main signal R _data for each ONU 2 by the PON control unit 46, so that the tuning parameter α can be obtained as information on the received power value A during the activation period. Can be used.

The activation signal separation processing unit 44 acquires the tuning parameter α from the PON control unit 46. The activation signal separation processing unit 44 obtains an activation signal R _act as a result of multiplying Expression (7) by the tuning parameter α. The activation signal R _act is expressed as in Expression (8) to Expression (10).

The received power of the main signal during the activation period may not match the received power of the main signal during a period other than the activation period. For this reason, there is an error between the received power value A of the main signal R _{data and} the received power value A ′ of the demodulated main signal αR _data ^bin . The error ε _datax is expressed as shown in Equation (11). The error ε _data is expressed as in Expression (12).

  FIG. 5 is a diagram illustrating an example of details of the operation of the OLT 4. The optical communication unit 20 of the ONU 2 transmits an activation signal of an upstream signal to the OLT 4 after waiting for a random time in the activation period when a self-ONU that is an unregistered ONU is newly connected to the OLT 4. For this reason, the transmission time of the main signal and the transmission time of the activation signal may not match. In FIG. 5, the transmission time of the main signal of the upstream signal is shifted from the transmission time of the activation signal of the upstream signal.

The activation signal demodulator 45 follows the time after sampling the main signal and the activation signal even when the transmission time of the main signal of the upstream signal and the transmission time of the activation signal of the upstream signal are shifted. By demodulating, the activation signal is demodulated. Accordingly, the activation signal demodulating unit 45 can extract the activation signal R _act even when the transmission time of the main signal is different from the transmission time of the activation signal. The activation signal demodulating unit 45 outputs the activation signal at a time considering the time for the signal to reciprocate between the OLT 4 and the ONU 2 based on the comparison result between the reception power value of the activation signal and the activation signal threshold value. You may demodulate.

In some cases, one activation signal and a plurality of main signals are power-multiplexed with the received electrical signal R. In the TDM-PON system, the OLT 4 manages which ONU 2 transmits the upstream signal at what time. The activation signal separation processing unit 44 receives one activation signal and a plurality of main signals by time-multiplexing the upstream signal main signal of the ONU 2-1 and the upstream signal main signal of the ONU 2-2. When the power is multiplexed on the electrical signal R, information indicating which ONU 2 main signal is demodulated is acquired from the PON control unit 46. The activation signal separation processing unit 44 adjusts the reception power value A ′ of the main signal to be subtracted for each ONU 2 based on information indicating which main signal of the ONU 2 is demodulated. The activation signal separation processing unit 44 removes the component of the binary main signal R _data ^bin from the received electrical signal R based on the adjusted received power value A ′, thereby obtaining the activation signal R _act for each ONU 2. obtain.

Even when one activation signal and a plurality of main signals are power-multiplexed with the received electrical signal R, the activation signal demodulation unit 45 activates the activation signal based on the received power value A ′ adjusted for each ONU 2. The separation processing unit 44 demodulates the activation signal by removing the component of the binary main signal R _data ^bin from the received electrical signal R.

The activation signal demodulator 45 updates the activation signal threshold according to whether or not the main signal R _data is included in the received electrical signal R. When the main signal R _data is included in the received electrical signal R, the activation signal demodulator 45 determines whether the value of the demodulated main signal R _data ^bin is 1 or 0, Update the activation signal threshold. The activation signal threshold is larger when the demodulated main signal R _data ^bin value is 1 than when the demodulated main signal R _data ^bin value is 0.

The activation signal demodulator 45 demodulates the activation signal based on the comparison result between the received power value A ′ of the demodulated main signal αR _data ^bin and the activation signal threshold. The activation signal demodulating unit 45 transmits a bit string representing the demodulated activation signal to the PON control unit 46. Note that the activation signal demodulator 45 may interrupt the process when it is a period other than the activation period.

The PON control unit 46 (system control unit) notifies the activation signal acquisition unit 42 of information indicating whether or not the activation window is expanded. The PON control unit 46 notifies the activation signal separation processing unit 44 of the tuning parameter α for each ONU 2 that is the upstream signal transmission source. The value of the tuning parameter α is determined for each received power value A ′ of the main signal R _data of the ONU 2 that is the upstream signal transmission source.

  FIG. 6 is a flowchart showing an example of the operation of the ONU 2. The power value monitor 21 measures the received power value of the main signal of the downlink signal (step S201). The path loss measuring unit 22 measures the loss of the transmission path (path) based on the received power value of the main signal of the downlink signal (step S202). The transmission power adjustment unit 23 adjusts the transmission power of the activation signal based on the measurement result of the transmission path loss (step S203). The transmission power adjustment unit 23 determines whether it is an activation period (step S204). If it is the activation period (step S204: Yes), the optical communication unit 20 transmits an activation signal to the OLT 4 via the optical coupler 3 (step S205). When it is a period other than the activation period (step S204: No), the ONU 2 ends the process.

FIG. 7 is a flowchart illustrating an example of the operation of the OLT 4. The optical square detection unit 40 converts the upstream signal, which is an optical signal, into an electrical signal (step S301). The activation signal acquisition unit 42 determines whether or not the current time is an activation period (step S302). When it is not the activation period (step S302: No), the power value monitor 41 measures the received power value of the main signal R _data that is the uplink signal of the registered ONU for each ONU 2. The power value monitor 41 records the received power value of the main signal R _data for each ONU 2 (step S303).

If it is the activation period (step S302: Yes), the power value monitor 41 demodulates the main signal R _data . The main signal demodulator 43 transmits the demodulated binary main signal R _data ^bin to the activation signal separation processor 44. (Step S304). The activation signal separation processing unit 44 determines whether or not the main signal is included in the received electrical signal R (step S305). If the main signal is not included in the received electrical signal R (step S305: No), the activation signal demodulator 45 determines the bit of the activation signal based on the received power value of the received received electrical signal R. The threshold value (bit determination threshold value) for updating is updated (step S306).

When the main signal is included in the received electrical signal R (step S305: Yes), the activation signal separation processing unit 44 estimates the tuning parameter α (step S307). The activation signal separation processing unit 44 obtains an activation signal R _act by removing a component of the binary main signal R _data ^bin from the received electrical signal R (step S308).

The activation signal demodulator 45 updates the activation signal threshold based on the demodulated bit information of the main signal R _data ^bin . That is, the activation signal demodulator 45 updates the threshold for determining the bit of the activation signal R _act according to the demodulated value (1 or 0) of the main signal R _data ^bin (step S309). Activation signal demodulation unit 45, based on a result of comparison between the activation signals R _act of receiving power values and activation signal threshold and demodulates the activation signal R _act (step S310).

  As described above, the optical transmission system 1 according to the first embodiment includes the plurality of ONUs 2 and the OLT 4. The ONU 2 registered in the OLT 4 includes the optical communication unit 20-1 and the like (first optical communication unit). The optical communication unit 20-1 or the like transmits the main signal to the OLT 4 with the first transmission power via the transmission path. The ONU 2 that is not registered in the OLT 4 includes a transmission power adjustment unit 23 and an optical communication unit 20-N (second optical communication unit). The transmission power adjustment unit 23 determines the second transmission power value based on the transmission path loss. The optical communication unit 20-N transmits a control signal (activation signal) with the second transmission power value to the OLT 4 via the transmission path. The OLT 4 includes an optical square detection unit 40 (signal acquisition unit), a main signal demodulation unit 43, an activation signal separation processing unit 44 (signal separation processing unit), and an activation signal demodulation unit 45 (control signal demodulation unit). Have The optical square detection unit 40 acquires a signal (received electric signal R) obtained by power-multiplexing the main signal and the control signal. The main signal demodulator 43 demodulates the main signal obtained based on the comparison result between the received power value of the power multiplexed signal and the main signal threshold (first threshold). The activation signal separation processing unit 44 separates the control signal from the power multiplexed signal based on the received power value of the main signal estimated based on the received power value of the main signal measured in advance. The activation signal demodulator 45 demodulates the separated control signal based on the comparison result between the received power value of the control signal and the activation signal threshold (second threshold).

  Thereby, the optical transmission system 1 according to the first embodiment can prevent the transmission delay of the uplink signal from occurring due to the activation period.

  The processing in the MAC (Media Access Control) layer can be realized by a conventional method, and a protocol need not be added. In addition, in the activation period, even when the main signal transmitted from the registered ONU and the activation signal transmitted from the unregistered ONU are power multiplexed on the transmission line, the OLT 4 separates the power multiplexed signals from each other. By doing so, the main signal and the activation signal can be obtained.

(Second Embodiment)
The second embodiment is different from the first embodiment in that the OLT 4 demodulates the activation signal R _act acquired during a period in which the main signal R _data is not included in the received electrical signal R. In the second embodiment, only differences from the first embodiment will be described.

  FIG. 8 is a diagram illustrating an example of a configuration of an uplink signal demodulation function unit of the OLT 4. The OLT 4 includes an optical square detection unit 40, an activation signal acquisition unit 42, a main signal demodulation unit 43, an activation signal demodulation unit 45, and a PON control unit 46.

The activation signal acquisition unit 42 acquires information indicating whether the activation window is expanded from the PON control unit 46. The activation signal acquisition unit 42 acquires information representing a period during which the main signal R _data is not included in the received electrical signal R from the PON control unit 46. The activation signal acquisition unit 42 transmits the received electrical signal R to the activation signal separation processing unit 44 when the received electrical signal R does not include the main signal R _data . The activation signal acquisition unit 42 interrupts the process when it is a period other than the activation period.

The activation signal demodulator 45 acquires the received electrical signal R from the activation signal acquisition unit 42 when the received electrical signal R does not include the main signal R _data . Only the activation signal acquired during a period in which the main signal R _data is not included in the received electrical signal R is demodulated. When the main signal R _data and the activation signal are power-multiplexed with the received electrical signal R, the activation signal demodulator 45 discards the activation signal without demodulating it.

The PON control unit 46 determines whether or not the activation window is expanded. The PON control unit 46 determines whether or not it is a period in which the main signal R _data is not included in the received electrical signal R.

  As described above, the optical transmission system 1 according to the second embodiment includes the plurality of ONUs 2 and the OLT 4. The ONU 2 registered in the OLT 4 includes the optical communication unit 20-1 and the like (first optical communication unit). The optical communication unit 20-1 or the like transmits the main signal to the OLT 4 with the first transmission power via the transmission path. The ONU 2 that is not registered in the OLT 4 includes a transmission power adjustment unit 23 and an optical communication unit 20-N (second optical communication unit). The transmission power adjustment unit 23 determines the second transmission power value based on the transmission path loss. The optical communication unit 20-N transmits a control signal (activation signal) with the second transmission power value to the OLT 4 via the transmission path. The OLT 4 includes an optical square detection unit 40 (signal acquisition unit), a main signal demodulation unit 43, and an activation signal demodulation unit 45 (control signal demodulation unit). The optical square detection unit 40 acquires a signal (reception electric signal R) obtained by power-multiplexing the main signal and the control signal in the first period, and acquires the control signal in a second period other than the first period. The main signal demodulator 43 demodulates the main signal obtained based on the comparison result between the received power value of the power multiplexed signal and the main signal threshold (first threshold). The activation signal demodulator 45 demodulates the control signal acquired in the second period.

  Accordingly, the optical transmission system 1 according to the second embodiment can prevent the transmission delay of the uplink signal from occurring due to the activation period even when the configuration of the OLT 4 is simple.

(Third embodiment)
The third embodiment is different from the first and second embodiments in that the ONU 2 transmits an activation signal with a predetermined transmission power. In the third embodiment, only differences from the first and second embodiments will be described.

  FIG. 9 is a diagram illustrating an example of the configuration of the ONU 2. The ONU 2 includes an optical communication unit 20, a transmission power adjustment unit 23, a PON control unit 24, and a BLDD 25. In the third embodiment, the ONU 2 does not include the power value monitor 21 and the path loss measurement unit 22 as compared with the first and second embodiments. The PON control unit 24 includes a time count unit 240 and an activation signal retransmission unit 241.

  The time count unit 240 measures a time-out time indicating that activation has not been executed within the time. The time count unit 240 notifies the activation signal retransmission unit 241 that the activation has not been executed within the time.

  The activation signal retransmission unit 241 sends an activation signal via the optical communication unit 20 when the OLT 4 does not execute the activation after the optical communication unit 20 transmits the activation signal and times out. Retransmit to OLT4. The activation signal retransmission unit 241 transmits information indicating that the activation signal is retransmitted to the transmission power adjustment unit 23.

The transmission power adjustment unit 23 adjusts the transmission power value P _s of the activation signal via the BLDD 25 so that the optical communication unit 20 transmits the activation signal with a predetermined transmission power. The transmission power adjustment unit 23 increases the transmission power step by step every time the activation signal is retransmitted. The transmission power adjustment unit 23 determines the amount of increase in transmission power according to a preset rule.

  As described above, the ONU 2 according to the third embodiment includes the activation signal retransmission unit 241 and the transmission power adjustment unit 23. The activation signal retransmission unit 241 retransmits the control signal to the OLT 4 when a response to the control signal (activation signal) is not obtained from the OLT 4 within a predetermined time. The transmission power adjustment unit 23 increases the second transmission power value every time the activation signal retransmission unit 241 retransmits the control signal.

  Thereby, the optical transmission system 1 according to the third embodiment can prevent the transmission delay of the uplink signal from being generated due to the activation period even when the configuration of the ONU 2 is simple.

(Fourth embodiment)
The fourth embodiment is different from the first to third embodiments in that the uplink signal transmission rate (transmission speed) is different from the downlink signal transmission rate. In the fourth embodiment, only differences from the first to third embodiments will be described.

  The communication unit of the OLT 4 does not always transmit a control signal indicating that the activation window is developed to the ONU 2 at a speed and encoding method equivalent to the transmission rate of the main signal. For this reason, the transmission rate of the activation signal may be asymmetric between the upstream signal and the downstream signal in the optical transmission system 1.

  The PON control unit 46 of the OLT 4 measures a round trip time (RTT) between the OLT 4 and the ONU 2 based on the activation signal acquired from the ONU 2 while the activation window is expanded. . When the uplink signal transmission rate and the downlink signal transmission rate are different (asymmetric), it is necessary to correct the difference in transmission rate.

  For example, when the transmission rate of the downstream signal activation signal is 10 Gbps and the upstream signal transmission rate is 5 Gbps, the OLT 4 obtains the same amount of information as the downstream signal activation signal from the upstream signal activation signal. For this purpose, it takes twice as long as the time of the activation signal of the upstream signal. Therefore, the PON control unit 46 (transmission rate correction unit) of the OLT 4 corrects the transmission rate of the activation signal of the upstream signal so as to correspond to the transmission rate of the main signal of the upstream signal. The PON control unit 46 of the OLT 4 determines the activation signal transmission rate in advance. The PON control unit 46 notifies the ONU 2 of the transmission rate of the activation signal.

  Further, the PON control unit 46 of the OLT 4 takes into account the delay due to the calculation time of each functional unit shown in FIGS. The PON control unit 46 corrects the delay caused by the calculation time of each functional unit. The PON control unit 46 determines the calculation time of each functional unit in advance. The PON control unit 46 may acquire information indicating the calculation time of each functional unit in advance. The PON control unit 46 corrects the delay time of the main signal of the uplink signal based on the transmission rate of the activation signal of the uplink signal and the calculation time of each functional unit.

  As described above, the OLT 4 of the fourth embodiment corrects the transmission rate of the control signal (activation signal) of the uplink signal so as to correspond to the transmission rate of the main signal of the uplink signal. Thus, the optical transmission system 1 according to the fourth embodiment prevents the transmission delay of the uplink signal from occurring due to the activation period even when the transmission rate of the uplink signal and the transmission rate of the downlink signal are different. Is possible.

  You may make it implement | achieve at least one part of the optical transmission system, terminal device, and termination device in embodiment mentioned above with a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be a program for realizing a part of the above-described functions, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. You may implement | achieve using programmable logic devices, such as FPGA (Field Programmable Gate Array).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  The present invention is applicable to an optical transmission system such as a TDM-PON system.

DESCRIPTION OF SYMBOLS 1 ... Optical transmission system, 2 ... ONU, 3 ... Optical coupler, 4 ... OLT, 20 ... Optical communication part, 21 ... Power value monitor, 22 ... Path loss measurement part, 23 ... Transmission power adjustment part, 24 ... PON control part 25 ... BLDD, 40 ... light square detection unit, 41 ... power value monitor, 42 ... activation signal acquisition unit, 43 ... main signal demodulation unit, 44 ... activation signal separation processing unit, 45 ... activation signal demodulation unit, 46 ... PON control unit, 240 ... time count unit, 241 ... activation signal retransmission unit

Claims (8)

An optical transmission system including a plurality of terminal devices and terminal devices,
The terminal device registered in the terminal device is
A first optical communication unit that transmits a main signal to the terminal device via a transmission line at a first transmission power;
The terminal device unregistered with the terminal device is:
A transmission power adjustment unit that determines a second transmission power value based on the loss of the transmission path;
A second optical communication unit that transmits a control signal at the second transmission power value to the terminal device via the transmission path;
The terminal device is
A signal acquisition unit for acquiring a power-multiplexed signal of the main signal and the control signal;
A main signal demodulating unit that demodulates the main signal obtained based on a comparison result between a received power value of the power multiplexed signal and a first threshold;
A signal separation processing unit that separates the control signal from the power multiplexed signal based on the received power value of the main signal estimated based on the received power value of the main signal measured in advance;
An optical transmission system comprising: a control signal demodulating unit that demodulates the separated control signal based on a comparison result between a received power value of the control signal and a second threshold value. The terminal device is
A terminal device controller that determines whether or not it is a period for receiving the control signal;
The optical transmission system according to claim 1, further comprising: a terminal device power value monitor that measures, for each of the termination devices, a reception power value of the main signal in a period other than a period in which the control signal is received. The terminator is
A terminating device power value monitor for measuring the received power value of the downlink signal transmitted by the terminal device;
The optical transmission system according to claim 1, further comprising: a path loss measuring unit that measures a loss of the transmission path based on a received power value of the downlink signal. The terminal device is
The optical transmission system according to any one of claims 1 to 3, further comprising: a transmission rate correction unit that corrects the transmission rate of the control signal so as to correspond to the transmission rate of the main signal.   The said control signal demodulation part updates the said 2nd threshold value according to whether the said main signal is contained in the signal by which the said power multiplexing was carried out, It is any one of Claims 1-4. Optical transmission system. The terminator is
A control signal retransmission unit that retransmits the control signal to the terminal device when a response to the control signal is not obtained from the terminal device within a predetermined time; and
The optical transmission system according to any one of claims 1 to 5, wherein the transmission power adjustment unit increases the second transmission power value every time the control signal retransmission unit retransmits the control signal. An optical transmission system including a plurality of terminal devices and terminal devices,
The terminal device registered in the terminal device is
A first optical communication unit that transmits a main signal to the terminal device via a transmission line at a first transmission power;
The terminal device unregistered with the terminal device is:
A transmission power adjustment unit that determines a second transmission power value based on the loss of the transmission path;
A second optical communication unit that transmits a control signal at the second transmission power value to the terminal device via the transmission path;
The terminal device is
A signal acquisition unit that acquires a power-multiplexed signal of the main signal and the control signal in a first period, and acquires the control signal in a second period other than the first period;
A main signal demodulating unit that demodulates the main signal obtained based on a comparison result between a received power value of the power multiplexed signal and a first threshold;
An optical transmission system comprising: a control signal demodulator that demodulates the control signal acquired in the second period. An optical transmission method executed by an optical transmission system including a plurality of terminal devices and terminal devices,
The terminal device registered in the terminal device is
A main signal is transmitted to the terminal device via a transmission line at a first transmission power;
The terminal device unregistered with the terminal device is:
A second transmission power value is determined based on the loss of the transmission path,
A control signal is transmitted to the terminal device via the transmission line at the second transmission power value;
The terminal device is
Obtaining a power-multiplexed signal of the main signal and the control signal;
Demodulating the main signal obtained based on a comparison result between the received power value of the power multiplexed signal and a first threshold;
Separating the control signal from the power multiplexed signal based on the received power value of the main signal estimated based on the received power value of the main signal measured in advance;
Demodulating the separated control signal based on a comparison result between the received power value of the control signal and a second threshold;
Optical transmission method.

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