JP6381384B2 - PON system, ONU, OLT, and transmission method - Google Patents

Description

  The present invention relates to a PON (Passive Optical Network) system, an ONU (Optical Network Unit), an OLT (Optical Line Terminal), and a transmission method for realizing optical fiber transmission.

  In recent years, the area (cell) covered by a base station apparatus has become narrower as the speed of a radio access network provided by a mobile communication network has decreased, and as a result, the number of base station apparatuses to be installed to configure the mobile communication network Has increased. For this reason, a passive optical network (PON) system in which a single optical transmission line is shared by a plurality of subscribers has been studied as a network for accommodating a plurality of base station apparatuses.

  In the PON system, one optical transmission line terminal (OLT: Optical Line Terminal) installed at a telecommunications carrier's station connects to multiple subscriber-side terminals (ONU: Optical Network Unit) via an optical splitter. Has been. The OLT realizes high band utilization efficiency by dynamically allocating an upstream band to a plurality of ONUs, for example, 64 ONUs, by a time division multiplexing method.

  When accommodating a plurality of base station devices in the PON system, frequency and time synchronization between the base station devices is essential. Conventionally, a GPS (Global Positioning System) antenna is generally installed in each base station apparatus in order to receive reference time information. However, there are cases where the GPS antenna cannot be installed due to restrictions such as the installation environment in the base station apparatus. For this reason, for example, Non-Patent Documents 1 and 2 disclose techniques for distributing frequency and time information from an upper network device to a lower network device and synchronizing the frequency and time of the entire network. Non-Patent Document 3 and Patent Document 1 disclose a technology in which a GPS antenna is installed in an OLT, and frequency and time information received by the GPS antenna is distributed to each ONU via an optical access distribution network. .

JP 2011-040870 A

IEEE Std 1588-2008, “IEEE Standard for a Precision Clock Synchronization Protocol for Network Measurement and Control Systems,” 2008. K. Hann, “Synchtonous Ethernet (registered trademark) to Transport Frequency and Phase / Time,” IEEE Communication Magazine, vol.50, no.8, pp.152-160, August 2012. Takayoshi Tashiro et al., “10G-EPON system with frequency / time synchronization function for mobile backhaul applications,” IEICE Tech. (B), vol.J96-B, no.3, pp.321-329, March 2013.

  However, in the techniques described in Non-Patent Documents 1 and 2, all the upper and lower network devices must be replaced with devices dedicated to frequency and time synchronization. For example, as shown in FIG. 14A, in order to provide frequency and time information from the OLT to each ONU via the IP network according to IEEE 1588, all the devices on the IP network side must support IEEE 1588. Don't be. For this reason, if there is at least one device on the IP network side that does not support IEEE 1588, a clock signal cannot be provided to each ONU.

  In the technique described in Non-Patent Document 3 and Patent Document 1, as shown in FIG. 14B, a coaxial cable for transmitting a GPS signal to a station where an OLT is installed, or a GPS signal is received. However, it is difficult to apply when the equipment installation space of the station building is restricted.

  The present invention has been made in view of such circumstances, and a loopback method in which a GPS signal is received on the ONU side, frequency and time information is provided to the OLT, and the OLT distributes it to each ONU. An object of the present invention is to provide a PON system, ONU, OLT, and transmission method that can be realized.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, the PON system of the present invention is a PON (Passive Optical Network) system that realizes optical fiber transmission, and includes a plurality of ONUs connected to the OLT via an OLT (Optical Line Terminal) and an optical branching unit. (Optical Network Unit) and a GPS signal receiving device that receives GPS signals and provides frequency information and time information to the OLT via the optical splitter, and the OLT includes the GPS signal receiving device. The frequency information and time information provided from the above are corrected using at least the transmission delay time with each ONU, and the corrected frequency information and time information are multicast-distributed to each ONU. Based on the corrected frequency information and time information received from the OLT, mutual synchronization is established.

  In this way, the OLT corrects the frequency information and time information provided from the GPS signal receiver using at least the transmission delay time with each ONU, and multicasts the corrected frequency information and time information to each ONU. Since each ONU establishes synchronization with each other based on the corrected frequency information and time information received from the OLT, it is possible to transfer the frequency information and time information in a loop-back manner via the OLT. Become. This enables frequency and time synchronization between base station devices in the PON system even when frequency information and time information cannot be distributed to all ONUs from a higher level network or when a GPS signal receiving device cannot be installed in the OLT. It becomes.

  (2) In the PON system of the present invention, the GPS signal receiving device is provided in any one ONU as a master ONU.

  Thus, since the GPS signal receiving device is provided in any one ONU as the master ONU, frequency information and time information are acquired from the GPS signal in any one ONU among the plurality of ONUs, Loopback transfer via OLT is realized, and frequency information and time information can be distributed to each ONU. This enables frequency and time synchronization between base station apparatuses in the PON system.

  (3) In the PON system of the present invention, the master ONU transmits a burst signal including frequency information and time information provided from the GPS signal receiver to the OLT, and the OLT The burst signal received from the ONU is accumulated in the buffer, the accumulated frequency information and time information are corrected using the buffering time and the transmission delay time with each ONU, and the corrected frequency information and time information are It is characterized by multicast distribution to each ONU.

  As described above, the OLT accumulates the burst signal received from the master ONU in the buffer, corrects the accumulated frequency information and time information using the buffering time and the transmission delay time with each ONU, Since frequency information and time information are multicast-distributed to each ONU, occurrence of timing jitter in the OLT can be avoided, and synchronization accuracy of frequency information and time information can be maintained.

  (4) In the PON system of the present invention, the master ONU transmits the frequency information and time information provided from the GPS signal receiving device to the OLT with an optical signal having a wavelength different from that of the upstream data signal. The OLT demultiplexes the optical signal received from the master ONU, corrects the frequency information and time information obtained by the wavelength demultiplexing using the transmission delay time with each ONU, and after the correction The frequency information and time information are multicast-distributed to each ONU.

  In this way, the master ONU transmits the frequency information and time information provided from the GPS signal receiving device to the OLT with an optical signal having a wavelength different from that of the upstream data signal, and the OLT receives the light received from the master ONU. The signal is wavelength-demultiplexed, the frequency information and time information obtained by wavelength demultiplexing are corrected using the transmission delay time with each ONU, and the corrected frequency information and time information are multicast distributed to each ONU. Therefore, in the OLT, it is possible to extract frequency information and time information without generating jitter. Thereby, it becomes possible to maintain the synchronization accuracy of frequency information and time information.

  (5) In the PON system of the present invention, the master ONU transmits a burst signal including an uplink data signal to the OLT and includes frequency information and time information provided from the GPS signal receiver. A RoF (Radio-over-Fiber) signal is transmitted to the OLT, and the OLT demultiplexes the upstream signal received from the master ONU at an RF (Radio Frequency) frequency, and the RoF signal is converted into a baseband signal. Converting and extracting time information, extracting frequency information from the burst signal rate, correcting the obtained frequency information and time information using a transmission delay time with each ONU, corrected frequency information and Time information is multicast-distributed to each ONU.

  As described above, the master ONU transmits a burst signal including an uplink data signal to the OLT, and transmits a RoF signal including frequency information and time information provided from the GPS signal receiver to the OLT. Demultiplexes the upstream signal received from the master ONU at the RF frequency, converts the RoF signal into a baseband signal, extracts time information, extracts frequency information from the burst signal rate, and obtains frequency information And the time information are corrected using the transmission delay time with each ONU, and the corrected frequency information and time information are multicast-distributed to each ONU. Therefore, in the OLT, the frequency information and the time information are generated without generating jitter. Can be extracted. Thereby, it becomes possible to maintain the synchronization accuracy of frequency information and time information.

  (6) The ONU of the present invention is an ONU (Optical Network Unit) applied to a PON (Passive Optical Network) system for realizing optical fiber transmission, and receives a GPS (Global Positioning System) signal. A GPS signal receiving device that provides frequency information and time information to the OLT via an optical splitter, a multiplexing unit that multiplexes the frequency information and time information into an uplink data signal, and an uplink data signal that has been multiplexed And an ONU transmission unit that transmits a burst signal to an OLT (Optical Line Terminal).

  Thus, the GPS signal is received, the frequency information and the time information are multiplexed on the uplink data signal, and the burst signal including the multiplexed uplink data signal is transmitted to the OLT. It is possible to perform loopback transfer via the network.

  (7) The ONU of the present invention is an ONU (Optical Network Unit) applied to a PON (Passive Optical Network) system that realizes optical fiber transmission, and receives a GPS (Global Positioning System) signal. A GPS signal receiver that provides frequency information and time information to the OLT via an optical splitter, a first optical converter that converts an upstream data signal into an optical signal of a first wavelength, and the GPS signal reception A second optical converter that converts frequency information and time information provided from the apparatus into an optical signal having a second wavelength different from the first wavelength; an optical signal having the first wavelength; And an ONU transmission unit that transmits an optical signal of a wavelength to an OLT (Optical Line Terminal).

  In this way, the GPS signal is received, the upstream data signal is converted into the optical signal of the first wavelength, and the frequency information and time information provided from the GPS signal receiving device are changed to the second wavelength different from the first wavelength. The optical signal having the wavelength is converted into the optical signal having the first wavelength and the optical signal having the second wavelength is transmitted to the OLT. Therefore, the OLT can extract frequency information and time information without generating jitter. It becomes possible. Thereby, it becomes possible to maintain the synchronization accuracy of frequency information and time information.

  (8) The ONU of the present invention is an ONU (Optical Network Unit) applied to a PON (Passive Optical Network) system that realizes optical fiber transmission, and receives a GPS (Global Positioning System) signal. A GPS signal receiving device that provides frequency information and time information to the OLT via an optical branching unit, and frequency information and time information provided from the GPS signal receiving device are respectively converted into RoF (Radio-over- And a ONU transmission unit that transmits the RoF signal to an OLT (Optical Line Terminal) together with a burst signal including an uplink data signal.

  In this way, the GPS signal is received, the frequency information and the time information provided from the GPS signal receiving device are converted into RoF signals of different frequencies, and the RoF signal is transmitted to the OLT together with the burst signal including the upstream data signal. Therefore, in the OLT, it is possible to extract frequency information and time information without generating jitter. Thereby, it becomes possible to maintain the synchronization accuracy of frequency information and time information.

  (9) The OLT of the present invention is an OLT (Optical Line Terminal) applied to a PON (Passive Optical Network) system that realizes optical fiber transmission, and includes frequency information and time provided from a GPS signal receiver. An OLT receiving unit that receives a burst signal including information from a master ONU; a buffer that accumulates the received burst signal; an extraction unit that extracts frequency information and time information from the burst signal accumulated in the buffer; Using the buffering time in the buffer and the transmission delay time with each subordinate ONU, the control unit that corrects the extracted frequency information and time information, and the corrected frequency information and time information to each subordinate ONU. And an OLT transmission unit that performs multicast distribution.

  In this way, the burst signal including the frequency information and time information provided from the GPS signal receiver is received from the master ONU, the received burst signal is accumulated in the buffer, and the frequency information and the burst information accumulated in the buffer are The time information is extracted, the buffered time in the buffer and the transmission delay time with each subordinate ONU are used to correct the extracted frequency information and time information, and the corrected frequency information and time information are changed to each subordinate ONU. Therefore, the occurrence of timing jitter in the OLT can be avoided, and the synchronization accuracy of frequency information and time information can be maintained.

  (10) The OLT of the present invention is an OLT (Optical Line Terminal) applied to a PON (Passive Optical Network) system that realizes optical fiber transmission, and includes frequency information and time provided from a GPS signal receiver. An OLT receiving unit for receiving information from the master ONU with an optical signal having a wavelength different from that of the upstream data signal, a demultiplexing unit for demultiplexing the received optical signal, frequency information obtained by the wavelength demultiplexing, and A control unit that corrects the time information using a transmission delay time with each subordinate ONU, and an OLT transmission unit that multicast-distributes the corrected frequency information and time information to each subordinate ONU. Features.

  In this way, the frequency information and time information provided from the GPS signal receiving device are received from the master ONU with an optical signal having a wavelength different from that of the upstream data signal, and the received optical signal is wavelength-demultiplexed, The obtained frequency information and time information are corrected using the transmission delay time with each subordinate ONU, and the corrected frequency information and time information are multicast-distributed to each subordinate ONU. It is possible to extract frequency information and time information without generating them. Thereby, it becomes possible to maintain the synchronization accuracy of frequency information and time information.

  (11) The OLT of the present invention is an OLT (Optical Line Terminal) applied to a PON (Passive Optical Network) system for realizing optical fiber transmission, and includes frequency information and time provided from a GPS signal receiver. An OLT receiving unit that receives a RoF (Radio-over-Fiber) signal including information as an upstream signal together with a burst signal including an upstream data signal, and demultiplexes the received upstream signal at an RF (Radio Frequency) frequency. A demultiplexing unit, a RoF signal obtained by the demultiplexing, which converts the RoF signal into a baseband signal, extracts time information, extracts frequency information from a burst signal rate, and the extracted frequency information and time information Is corrected using the transmission delay time with each subordinate ONU, and the frequency information and time information after the correction are malformed to each subordinate ONU. Characterized in that it comprises a OLT transmitting unit to cast delivery to.

  In this way, the RoF signal including the frequency information and time information provided from the GPS signal receiving device is received as an upstream signal together with the burst signal including the upstream data signal, and the received upstream signal is demultiplexed at the RF frequency. The RoF signal obtained by the demultiplexing is converted into a baseband signal to extract time information, and the frequency information is extracted from the burst signal rate, and the extracted frequency information and time information are transmitted to each subordinate ONU. Correction is performed using the delay time, and the corrected frequency information and time information are multicast-distributed to each subordinate ONU. Therefore, in the OLT, it is possible to extract the frequency information and time information without generating jitter. . Thereby, it becomes possible to maintain the synchronization accuracy of frequency information and time information.

  (12) A transmission method of the present invention is a transmission method of a PON (Passive Optical Network) system that realizes optical fiber transmission, and a GPS (Global Positioning System) signal receiving device receives a GPS signal, A step of providing frequency information and time information to an OLT (Optical Line Terminal) via a branching unit; and in the OLT, at least frequency information and time information provided from the GPS signal receiving device are transmitted to each ONU (Optical A step of multicasting the corrected frequency information and time information to each subordinate ONU, and the corrected frequency information received from the OLT in each ONU. And at least a step of establishing synchronization with each other based on the time information.

  In this way, the OLT corrects the frequency information and time information provided from the GPS signal receiver using at least the transmission delay time with each ONU, and multicasts the corrected frequency information and time information to each ONU. Since each ONU establishes synchronization with each other based on the corrected frequency information and time information received from the OLT, it is possible to transfer the frequency information and time information in a loop-back manner via the OLT. Become. This enables frequency and time synchronization between base station devices in the PON system even when frequency information and time information cannot be distributed to all ONUs from a higher level network or when a GPS signal receiving device cannot be installed in the OLT. It becomes.

  According to the present invention, frequency information and time information can be transferred in a loopback via the OLT. This enables frequency and time synchronization between base station devices in the PON system even when frequency information and time information cannot be distributed to all ONUs from a higher level network or when a GPS signal receiving device cannot be installed in the OLT. It becomes.

It is a figure showing a schematic structure of a PON system concerning an embodiment of the present invention. 1 is a diagram illustrating a schematic configuration of a PON system according to Embodiment 1. FIG. 1 is a block diagram illustrating a schematic configuration of a master ONU according to Embodiment 1. FIG. It is a block diagram which shows schematic structure of a slave ONU. 1 is a block diagram illustrating a schematic configuration of an OLT according to a first embodiment. It is a figure which shows operation | movement of the PON system concerning Example 1. FIG. 3 is a sequence chart illustrating an operation of the PON system according to the first embodiment. It is a figure which shows schematic structure of the PON system which concerns on Example 2. FIG. It is a block diagram which shows schematic structure of the master ONU which concerns on Example 2. FIG. FIG. 6 is a block diagram illustrating a schematic configuration of an OLT according to a second embodiment. It is a figure which shows an example of frequency arrangement | positioning. FIG. 10 is a diagram illustrating a schematic configuration of a PON system according to a third embodiment. It is a block diagram which shows schematic structure of the master ONU which concerns on Example 3. FIG. FIG. 10 is a block diagram illustrating a schematic configuration of an OLT according to a third embodiment. It is a figure which shows schematic structure of the PON system which distributes frequency information and time information from a high-order network. It is a figure which shows schematic structure of the PON system which receives a GPS signal by OLT and distributes frequency information and time information.

  In the conventional PON system, the present inventors pay attention to the fact that frequency and time synchronization, which are essential between a plurality of base station apparatuses, have not always been easily realized, and a GPS signal is transmitted to any one ONU. It was found that the frequency and time synchronization between the base station apparatuses can be easily realized by loopback transfer of the frequency information and time information via the OLT.

  That is, the PON system of the present invention is a PON system that realizes optical fiber transmission, and receives GPS signals from an OLT and a plurality of ONUs connected to the OLT via an optical splitter, and transmits the optical signal. A GPS signal receiving device that provides frequency information and time information to the OLT via a branching device, and the OLT receives at least each of the ONUs from the frequency information and time information provided from the GPS signal receiving device. And the corrected frequency information and time information are multicast distributed to each ONU, and each ONU is based on the corrected frequency information and time information received from the OLT. And establishing synchronization with each other.

  With this configuration, the present inventors can perform loopback transfer of frequency information and time information via the OLT. If the frequency information and time information cannot be distributed to all ONUs from the upper network, Even when the GPS signal receiving device cannot be installed, the frequency and time synchronization between the base station devices in the PON system can be performed. Embodiments of the present invention will be specifically described below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a PON system according to an embodiment of the present invention. In this PON system, the OLT 100 and a plurality of ONUs 201 to 203 are connected via an optical branching device 300. Base station apparatuses 211 to 213 are connected to the ONUs 201 to 203, respectively. The ONU 201 is provided with a GPS antenna 220 and configured to receive GPS signals from the GPS satellite 230. In the present embodiment, the ONU 201 having the GPS antenna 220 is referred to as “master ONU”, and the other ONUs 202 and 203 are referred to as “slave ONU”. In the present embodiment, the master ONU 201 acquires a GPS signal, and loop-back-transfers frequency information and time information to each slave ONU 202, 203 via the OLT. This eliminates the need for replacement of higher-level network devices and GPS pull-in to the OLT, and can realize frequency / time synchronization between base stations even in a situation where it is difficult to install a GPS antenna.

  That is, in this embodiment, as shown in FIG. 1, the master ONU 201 receives a GPS signal from the GPS antenna 220 and transmits frequency information and time information to the OLT 100. The OLT 100 extracts frequency information and time information from the signal received from the master ONU 201. Next, the OLT 100 corrects the frequency information and the time information based on the transmission delay time with each slave ONU 202, 203, and performs multicast distribution to each slave ONU 202, 203. Each slave ONU 202, 203 realizes synchronization between base stations based on the frequency information and time information received from the OLT 100.

  Here, in the upstream direction of the PON system, that is, the direction from the ONU to the OLT, transmission is normally performed by a burst signal. For this reason, in OLT, when receiving an upstream burst signal, it is necessary to eliminate frequency and time synchronization errors caused by jitter. Therefore, in this embodiment, the influence of jitter is eliminated by the following three examples.

  FIG. 2 is a diagram illustrating a schematic configuration of the PON system according to the first embodiment. In the first embodiment, the OLT 100-1 is provided with the buffer 101, and the jitter generated when the upstream burst signal is received is absorbed by buffering. This eliminates frequency and time synchronization errors. That is, in FIG. 2, the master ONU 201-1 acquires a GPS signal, and transmits frequency information and time information as a burst signal to the OLT 100-1. The OLT 100-1 accumulates the received upstream burst signal in the buffer 101 and absorbs jitter. Thereafter, frequency information and time information are extracted.

  The OLT 100-1 corrects the extracted frequency information and time information based on the buffering time in the buffer 101 and the transmission delay time with each slave ONU 202 and 203, and the corrected frequency information and time information are corrected to each slave ONU 202, Multicast delivery to 203. Each slave ONU 202, 203 realizes synchronization between base stations based on the frequency information and time information received from the OLT 100-1. In FIG. 2, one master ONU 201-1 and two slave ONUs 202 and 203 are shown. However, this is merely an example, and the present invention is not limited to these numbers.

  FIG. 3 is a block diagram illustrating a schematic configuration of the master ONU according to the first embodiment. In FIG. 3, the master ONU 11-1 acquires the signal received by the GPS antenna 13 by the GPS signal receiving unit 15. The GPS antenna 13 and the GPS signal receiving unit 15 constitute a GPS signal receiving device 16. The GPS signal receiving device 16 may be provided outside the master ONU 11-1.

  The GPS signal reception unit 15 outputs a 10 MHz signal as frequency information (reference clock) to the CLK generation unit 17 and outputs 1 PPS / ToD as time information to the CPU 19. Here, the 10 MHz signal is a reference sine wave from the GPS signal receiving device 16, 1 PPS is a signal that defines the start phase of 1 second, and ToD is a text describing the hour, minute, and second Means information.

  The CLK generator 17 outputs the clock signal CLK1 to the CPU 19 and outputs the clock signal CLK2 to the E / O 23. The upstream data signal is input to the control signal multiplexing unit 21, multiplexed with time information input from the CPU 19, converted into an optical signal by the E / O 23 that converts an electrical signal into an optical signal, and output to the WDM 25. The WDM 25 transmits an optical signal to an OLT (not shown) via an optical fiber.

  On the other hand, the optical signal received from the OLT via the optical fiber is input to the WDM 25 and converted into an electrical signal by the O / E 27 that converts the optical signal into an electrical signal. The control signal separation unit 29 separates the downlink data signal and the control signal and outputs the control signal to the CPU 19.

  FIG. 4 is a block diagram showing a schematic configuration of the slave ONU. The slave ONU 12 includes a CLK extraction unit 30 that extracts CLK1 from a signal received from the OLT, and a frequency conversion unit 32 that converts the frequency of CLK1 and outputs a 10 MHz signal. Unlike the master ONU, the GPS signal receiver 16 and the CLK generator 17 are not provided. Other configurations are the same as those of the master ONU.

  The slave ONU 12 acquires frequency information and time information corrected according to the transmission delay time from an OLT (not shown), and the CLK extraction unit 30 extracts CLK1. In addition, the corrected time information is extracted by the control signal separation unit 29 and input to the CPU 19. The CPU 19 outputs a 1PPS / ToD signal as time information, and the frequency converter 32 outputs a 10 MHz signal.

  FIG. 5 is a block diagram illustrating a schematic configuration of the OLT according to the first embodiment. The OLT 41-1 receives the upstream burst signal in the WDM 43. The O / E 45 that converts an optical signal into an electric signal converts the received upstream burst signal into an electric signal. The buffer 47 accumulates the upstream burst signal converted into an electrical signal. Thereby, jitter is absorbed. The CLK extraction unit 49 extracts CLK1 and CLK2 from the upstream burst signal, outputs CLK1 to the CPU 51, and outputs CLK2 to the E / O 59. The control signal separation unit 55 separates the uplink data signal and the control signal including time information from the uplink burst signal.

  The CPU 51 generates frequency information and time information to be distributed to the slave ONU based on the time information input from the control signal separation unit 55 and the CLK1 input from the CLK extraction unit 49. At that time, the memory 53 is used to correct the frequency information and time information based on RTT (Round-Trip Time), that is, the transmission delay time for each slave ONU. The corrected frequency information and time information are input to the control signal multiplexing unit 57. The control signal multiplexing unit 57 multiplexes the corrected frequency information and time information and the downlink data signal. The multiplexed signal is converted into an optical signal by an E / O 59 that converts an electrical signal into an optical signal and input to the WDM 43. The WDM 43 multicasts the input signal to each slave ONU via an optical fiber.

  The PON system according to the first embodiment including the above components operates as follows. FIG. 6 is a diagram illustrating the operation of the PON system according to the first embodiment. The GPS signal receiving device 16 acquires a GPS signal via a GPS antenna. The master ONU 11-1 transmits the frequency information (reference clock) and time information (1PPS and ToD) supplied from the GPS signal receiving device 16 to the OLT 41-1 by a burst signal. The OLT 41-1 absorbs the jitter of the received upstream burst signal by buffering, extracts frequency information (reference clock), and corrects the transmission delay time of the master ONU 11-1 and each slave ONU 12. Multicast distribution to each slave ONU 12 in an OAM (Operation, Administration & Maintenance) frame.

  FIG. 7 is a sequence chart illustrating the operation of the PON system according to the first embodiment. First, initial registration is performed between the OLT and the master ONU (step S1). Next, initial registration is performed between the OLT and the slave ONU (step S2). At this time, the OLT measures the RTT. Next, the OLT secures “Normal GATE” (step S3), and the master ONU notifies the OLT that the own device is the master ONU (step S4). Next, the OLT secures “Normal GATE” (step S5), and the master ONU transmits frequency information and time information to the OLT (step S6). The OLT corrects the frequency information and time information in consideration of the transmission delay time for each slave ONU, and multicast-distributes the corrected frequency information and time information to each slave ONU (step S7). Each slave ONU extracts clock and time information and realizes synchronization between base stations. Note that sequences related to normal data transmission / reception are omitted.

  According to the first embodiment, frequency information and time information can be loopback transferred from the master ONU to each slave ONU via the OLT, and the frequency and time caused by jitter when receiving an upstream burst signal in the OLT. Synchronization error is eliminated.

  FIG. 8 is a diagram illustrating a schematic configuration of the PON system according to the second embodiment. In the second embodiment, the master ONU 201-2 is provided with two optical transmitters having different wavelengths, and a data signal, a control signal, and the like are transmitted as an upstream burst signal having the wavelength λ1. On the other hand, frequency information and time information are transmitted by a continuous signal having a wavelength λ2 having a wavelength different from the wavelength λ1. Further, in the OLT 100-2, the upstream signal of each wavelength is demultiplexed and received by the optical receiver (RX (λ2)) for frequency information and time information. This makes it possible to extract frequency information and time information without generating jitter.

  In FIG. 8, the master ONU 201-2 acquires a GPS signal and transmits a data signal and a control signal to the OLT 100-2 as a burst signal having a wavelength λ1, and frequency information and time information are different from the wavelength λ1. It transmits with a continuous signal of wavelength λ2. The OLT 100-2 demultiplexes the received upstream signal and extracts frequency information and time information from the continuous signal having the wavelength λ2.

  The OLT 100-2 corrects the extracted frequency information and time information based on the transmission delay time with each slave ONU 202, 203. The corrected frequency information and time information are multicast-distributed to each slave ONU 202, 203 as a continuous signal having the same wavelength as the downlink data signal. Each slave ONU 202, 203 realizes synchronization between base stations based on the frequency information and time information received from the OLT 100-2. Although FIG. 8 shows one master ONU 201-2 and two slave ONUs 202 and 203, this is merely an example, and the present invention is not limited to these numbers.

  FIG. 9 is a block diagram illustrating a schematic configuration of the master ONU according to the second embodiment. In FIG. 9, the master ONU 11-2 acquires the signal received by the GPS antenna 13 by the GPS signal receiving unit 15. The GPS antenna 13 and the GPS signal receiving unit 15 constitute a GPS signal receiving device 16. The GPS signal receiving device 16 may be provided outside the master ONU 11-2.

  The GPS signal reception unit 15 outputs a 10 MHz signal as frequency information (reference clock) to the CLK generation unit 17 and outputs 1 PPS / ToD as time information to the CPU 19. The CLK generation unit 17 outputs the clock signal CLK1 to the CPU 19 and outputs the clock signal CLK2 to the E / O 23b. The E / O 23 b converts the time information input from the CPU 19 from an electrical signal to an optical signal having a wavelength λ 2 using the CLK 2 input from the CLK generation unit 17 as a reference, and outputs the optical signal to the WDM 25.

  The upstream data signal is input to the control signal multiplexing unit 21, multiplexed with time information input from the CPU 19, converted to an optical signal of wavelength λ 1 by the E / O 23 a that converts the electrical signal into an optical signal, and output to the WDM 25. The The WDM 25 transmits a burst signal having a wavelength λ1 and a continuous signal having a wavelength λ2 to an OLT (not shown) via an optical fiber.

  On the other hand, the optical signal received from the OLT via the optical fiber is input to the WDM 25 and converted into an electrical signal by the O / E 27 that converts the optical signal into an electrical signal. The control signal separation unit 29 separates the downlink data signal and the control signal and outputs the control signal to the CPU 19.

  FIG. 10 is a block diagram illustrating a schematic configuration of the OLT according to the second embodiment. The OLT 41-2 receives the burst signal having the wavelength λ1 and the continuous signal having the wavelength λ2 in the WDM 43. The O / E 45a that converts the optical signal having the wavelength λ1 into an electrical signal converts the received upstream burst signal into an electrical signal. The O / E 45b that converts the optical signal having the wavelength λ2 into an electric signal converts the received upstream continuous signal into an electric signal. The CLK extraction unit 49 extracts CLK1 and CLK2 from the upstream continuous signal, outputs CLK1 to the CPU 51, and outputs CLK2 to the E / O 59. The control signal separation unit 55 separates the uplink data signal and the control signal including time information from the uplink burst signal.

  The CPU 51 generates frequency information and time information to be distributed to the slave ONU based on the time information input from the control signal separation unit 55 and the CLK1 input from the CLK extraction unit 49. At that time, the memory 53 is used to correct the frequency information and time information based on RTT (Round-Trip Time), that is, the transmission delay time for each slave ONU. The corrected frequency information and time information are input to the control signal multiplexing unit 57. The control signal multiplexing unit 57 multiplexes the corrected frequency information and time information and the downlink data signal. The multiplexed signal is converted into an optical signal by an E / O 59 that converts an electrical signal into an optical signal and input to the WDM 43. The WDM 43 multicasts the input signal to each slave ONU via an optical fiber.

  According to the second embodiment, the frequency information and time information can be loopback transferred from the master ONU to each slave ONU via the OLT, and the frequency and time caused by jitter when receiving the upstream burst signal in the OLT. Synchronization error is eliminated.

  In the third embodiment, the master ONU transmits a data signal and a control signal as an upstream burst signal, and transmits the frequency information and the time information by optical fiber radio (RoF) on an RF carrier. In the OLT, the upstream signal is demultiplexed at the RF frequency, and the RoF signal is frequency-converted into a baseband signal. Thereby, frequency information and time information are extracted without generating jitter.

  FIG. 11A is a diagram illustrating an example of a frequency arrangement. An upstream burst signal is arranged in a low frequency region, frequency information (tone signal) is arranged at frequency f1, and time information is arranged at frequency f2.

  FIG. 11B is a diagram illustrating a schematic configuration of the PON system according to the third embodiment. The master ONU 201-3 acquires a GPS signal, transmits a data signal and a control signal as an upstream burst signal to the OLT 100-3, and transmits a frequency information and time information as a RoF signal carried on an RF carrier. The OLT 100-3 demultiplexes the received uplink signal at the RF frequency, converts the RoF signal into a baseband signal, and then extracts time information. Also, frequency information is extracted from the upstream burst signal rate.

  The OLT 100-3 corrects the extracted frequency information and time information based on the transmission delay time with each slave ONU 202, 203. The corrected frequency information and time information are multicast-distributed to each slave ONU 202, 203. Each slave ONU 202, 203 realizes synchronization between base stations based on the frequency information and time information received from the OLT 100-3. In FIG. 11B, one master ONU 201-3 and two slave ONUs 202 and 203 are shown, but this is merely an example, and the present invention is not limited to these numbers.

  FIG. 12 is a block diagram illustrating a schematic configuration of the master ONU according to the third embodiment. In FIG. 12, the master ONU 11-3 acquires the signal received by the GPS antenna 13 by the GPS signal receiving unit 15. The GPS antenna 13 and the GPS signal receiving unit 15 constitute a GPS signal receiving device 16. The GPS signal receiving device 16 may be provided outside the master ONU 11-3.

  The GPS signal reception unit 15 outputs a 10 MHz signal as frequency information (reference clock) to the CLK generation unit 17 and the frequency conversion unit 31a, and outputs 1 PPS / ToD as time information to the CPU 19. The CLK generator 17 outputs the clock signal CLK1 to the CPU 19 and outputs the clock signal CLK2 to the E / O 23. The frequency conversion unit 31a converts the input frequency information (10 MHz) to the frequency f1 and outputs the frequency f1 to the MUX 40. The uplink data signal is input to the control signal multiplexing unit 21, multiplexed with the control information input from the CPU 19, and output to the MUX 40.

  The CPU 19 outputs the time information to the frequency converter 31b based on 1PPS / ToD as the input time information. The frequency conversion unit 31b converts the time information into the frequency f2 and outputs it to the MUX 40. The MUX 40 multiplexes each input frequency and outputs it to the E / O 23. The E / O 23 converts an electrical signal into an optical signal and outputs the optical signal to the WDM 25. The WDM 25 transmits an optical signal to an OLT (not shown) via an optical fiber.

  On the other hand, the optical signal received from the OLT via the optical fiber is input to the WDM 25 and converted into an electrical signal by the O / E 27 that converts the optical signal into an electrical signal. The control signal separation unit 29 separates the downlink data signal and the control signal and outputs the control signal to the CPU 19.

  FIG. 13 is a block diagram illustrating a schematic configuration of the OLT according to the third embodiment. The OLT 41-3 receives the uplink signal in the WDM 43. The O / E 45 that converts an optical signal into an electrical signal converts the received upstream signal into an electrical signal. The DEMUX 46 demultiplexes the received upstream signal at the RF frequency and outputs a signal including the frequencies f1 and f2, the data signal, and the control signal. The frequency conversion unit 48a extracts time information from the frequency f2, and the frequency conversion unit 48b extracts CLK1 from the frequency f1. The control signal separation unit 55 separates the uplink data signal and the control signal including time information from the signal including the data signal and the control signal.

  The CPU 51 generates frequency information and time information to be distributed to the slave ONU based on the time information input from the frequency conversion unit 48a and the CLK1 input from the frequency conversion unit 48b. At that time, the memory 53 is used to correct the frequency information and time information based on RTT (Round-Trip Time), that is, the transmission delay time for each slave ONU. The corrected frequency information and time information are input to the control signal multiplexing unit 57. The control signal multiplexing unit 57 multiplexes the corrected frequency information and time information and the downlink data signal. The multiplexed signal is converted into an optical signal by an E / O 59 that converts an electrical signal into an optical signal and input to the WDM 43. The WDM 43 multicasts the input signal to each slave ONU via an optical fiber.

  According to the third embodiment, frequency information and time information can be loopback transferred from the master ONU to each slave ONU via the OLT, and the frequency and time caused by jitter when receiving an upstream burst signal in the OLT. Synchronization error is eliminated.

11-1 to 11-3 Master ONU
13 GPS antenna 15 GPS signal receiver 16 GPS signal receiver 17 CLK generator 19 CPU
21 Control signal multiplexer 23, 23a, 23b, 59 E / O
25, 43 WDM
27, 45, 45a, 45b O / E
29 control signal separation unit 30 CLK extraction unit 31a frequency conversion unit 31b frequency conversion unit 32 frequency conversion unit 47 buffer 48a frequency conversion unit 48b frequency conversion unit 49 CLK extraction unit 53 memory 55 control signal separation unit 57 control signal multiplexing unit 100, 100 -1 to 100-3 OLT
101 Buffer 201, 201-1 to 201-3 Master ONU
202, 203 Slave ONU
211 to 213 Base station apparatus 220 GPS antenna 230 GPS satellite 300 Optical splitter

Claims (12)

A PON (Passive Optical Network) system that realizes optical fiber transmission,
OLT (Optical Line Terminal),
A plurality of ONUs (Optical Network Units) connected to the OLT via optical splitters;
A GPS signal receiving device that receives a GPS (Global Positioning System) signal and provides frequency information and time information to the OLT via the optical splitter;
The OLT corrects the frequency information and time information provided from the GPS signal receiver using at least a transmission delay time with each ONU, and multicasts the corrected frequency information and time information to each ONU. Deliver,
The ONUs establish synchronization with each other based on corrected frequency information and time information received from the OLT.   The PON system according to claim 1, wherein the GPS signal receiving device is provided in any one ONU as a master ONU. The master ONU transmits a burst signal including frequency information and time information provided from the GPS signal receiver to the OLT,
The OLT stores a burst signal received from the master ONU in a buffer, corrects the stored frequency information and time information using a buffering time and a transmission delay time with each ONU, and frequency information after correction 3. The PON system according to claim 2, wherein the time information and the time information are multicast-distributed to the respective ONUs. The master ONU transmits the frequency information and time information provided from the GPS signal receiver to the OLT with an optical signal having a wavelength different from that of the upstream data signal,
The OLT demultiplexes the optical signal received from the master ONU, corrects the frequency information and time information obtained by the wavelength demultiplexing using the transmission delay time with each ONU, and the corrected frequency. The PON system according to claim 2, wherein the information and the time information are multicast-distributed to each ONU. The master ONU transmits a burst signal including an uplink data signal to the OLT, and transmits a RoF (Radio-over-Fiber) signal including frequency information and time information provided from the GPS signal receiving device to the OLT. Send to
The OLT demultiplexes the upstream signal received from the master ONU at an RF (Radio Frequency) frequency, converts the RoF signal into a baseband signal, extracts time information, and extracts frequency information from the burst signal rate. The obtained frequency information and time information are corrected using a transmission delay time with each ONU, and the corrected frequency information and time information are multicast distributed to each ONU. 2. The PON system according to 2. An ONU (Optical Network Unit) applied to a PON (Passive Optical Network) system that realizes optical fiber transmission,
A GPS signal receiving device that receives a GPS (Global Positioning System) signal and provides frequency information and time information;
A multiplexing unit that multiplexes the frequency information and time information into an uplink data signal;
An ONU comprising: an ONU transmission unit that transmits a burst signal including the multiplexed uplink data signal to an OLT (Optical Line Terminal). An ONU (Optical Network Unit) applied to a PON (Passive Optical Network) system that realizes optical fiber transmission,
A GPS signal receiving device that receives a GPS (Global Positioning System) signal and provides frequency information and time information;
A first optical converter that converts an upstream data signal into an optical signal of a first wavelength;
A second optical converter that converts the frequency information and time information provided from the GPS signal receiver into an optical signal having a second wavelength different from the first wavelength;
An ONU comprising: an ONU transmission unit that transmits the optical signal of the first wavelength and the optical signal of the second wavelength to an OLT (Optical Line Terminal). An ONU (Optical Network Unit) applied to a PON (Passive Optical Network) system that realizes optical fiber transmission,
A GPS signal receiving device that receives a GPS (Global Positioning System) signal and provides frequency information and time information;
A conversion unit that converts frequency information and time information provided from the GPS signal receiving device into RoF (Radio-over-Fiber) signals of different frequencies;
An ONU comprising: an ONU transmission unit that transmits the RoF signal to an OLT (Optical Line Terminal) together with a burst signal including an uplink data signal. An OLT (Optical Line Terminal) applied to a PON (Passive Optical Network) system that realizes optical fiber transmission,
An OLT receiver that receives a burst signal including frequency information and time information provided from a GPS signal receiver from a master ONU;
A buffer for storing the received burst signal;
An extraction unit for extracting frequency information and time information from the burst signal accumulated in the buffer;
A control unit that corrects the extracted frequency information and time information using a buffering time in the buffer and a transmission delay time with each ONU under its control;
An OLT comprising: an OLT transmitting unit that multicast-distributes the corrected frequency information and time information to each subordinate ONU. An OLT (Optical Line Terminal) applied to a PON (Passive Optical Network) system that realizes optical fiber transmission,
An OLT receiver that receives frequency information and time information provided from the GPS signal receiver from the master ONU with an optical signal having a wavelength different from that of the upstream data signal;
A demultiplexing unit for demultiplexing the received optical signal;
A control unit that corrects the frequency information and time information obtained by the wavelength demultiplexing using a transmission delay time with each subordinate ONU;
An OLT comprising: an OLT transmitting unit that multicast-distributes the corrected frequency information and time information to each subordinate ONU. An OLT (Optical Line Terminal) applied to a PON (Passive Optical Network) system that realizes optical fiber transmission,
An OLT receiver that receives a RoF (Radio-over-Fiber) signal including frequency information and time information provided from a GPS signal receiver as an upstream signal together with a burst signal including an upstream data signal;
A demultiplexing unit for demultiplexing the received upstream signal at an RF (Radio Frequency) frequency;
An extraction unit that converts the RoF signal obtained by the demultiplexing into a baseband signal and extracts time information, and extracts frequency information from a burst signal rate;
A controller that corrects the extracted frequency information and time information using a transmission delay time with each subordinate ONU;
An OLT comprising: an OLT transmitting unit that multicast-distributes the corrected frequency information and time information to each subordinate ONU. A transmission method of a PON (Passive Optical Network) system that realizes optical fiber transmission,
In a GPS (Global Positioning System) signal receiving device, receiving a GPS signal and providing frequency information and time information to an OLT (Optical Line Terminal) via an optical splitter;
In the OLT, the frequency information and time information provided from the GPS signal receiving device are corrected using at least the transmission delay time with each subordinate ONU (Optical Network Unit), and the corrected frequency information and time information are Multicast delivery to each subordinate ONU;
Each of the ONUs includes at least a step of establishing synchronization with each other based on the corrected frequency information and time information received from the OLT.

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