Abstract: A management apparatus in a time synchronization system includes a time variation information receiving unit configured to acquire time variation information and position information of a time synchronization apparatus, a position information classifying unit configured to classify time synchronization apparatuses into predetermined categories based on the acquired position information, a time variation analysis configured to determine majority based on whether patterns of time variation of the time synchronization apparatuses belonging to an identical category are identical to each other, and to analyze the time variation based on the determined results, and a filtering and delivery unit configured to output an instruction to block the time information received from the positioning satellite, to the time synchronization apparatus having abnormal time variation.

Abstract: The accuracy of an offset value is improved by correcting an error in time synchronization caused by link asymmetry. PTP packets are exchanged between a master node 3 and a slave node 4 vis a first transmission device 1 connected to the master node 3 and a second transmission device 2 corresponding to the first transmission device 1 and connected to the slave node 4.

Abstract: [Problem] To monitor a frequency difference between an input clock and a synchronous clock synchronized with the input clock. [Solution] A clock frequency monitoring apparatus that monitors the frequency of an input clock 18a includes a phase comparator 12 that compares a phase of a synchronous clock 18e phase-synchronized with the input clock 18a or a first frequency-divided clock 18f obtained by frequency-dividing the synchronous clock 18e with the phase of the input clock 18a, a filter 13 that low-pass filters an output signal of the phase comparator 12, an oscillator 14 that generates the synchronous clock 18e having a frequency corresponding to a control value from the filter 13, and a determiner 19 that determines that the frequency of the input clock 18a is abnormal when the variation amplitude of the output signal of the filter 13 is equal to or more than a predetermined range.

Abstract: A time synchronization mechanism is provided. A second transmission device includes: a transmission section configured to transmit packets for delay calculation for a plurality of wavelengths to the corresponding time transmission device simultaneously; and a reception section configured to calculate a propagation delay Dms on a path from the corresponding time transmission device to the second transmission device based on a difference between the arrival times of the packets for delay calculation for the plurality of wavelengths received, receive a propagation delay Dsm on a path from the second transmission device to the corresponding time transmission device calculated, and calculate a propagation delay Dmax that is larger than any of the propagation delay Dms and the propagation delay Dsm. The reception section transmits a received PTP packet to a slave node after a waiting delay Wms calculated by subtracting the propagation delay Dms from the propagation delay Dmax.

Abstract: An optical transmission device of each node simultaneously sends a plurality of signals having different wavelengths as delay measurement signals to a transmission path. The optical transmission device determines a delay value that reflects a propagation delay calculated based on an arrival time difference between a plurality of wavelengths in a signal received from another node, and determines a waiting time amount based on the delay value and the propagation delay. The optical transmission device notifies the other node of the delay value. Each optical transmission device outputs the received signal from the other node with a delay of the waiting time amount. The optical transmission device generates an optical intermittent signal obtained by selecting and multiplexing any of time information, the delay measurement signal, and communication information. A reception side extracts a desired multiplexed signal from the received optical intermittent signals.

Abstract: [Problem to be Solved] Optimizing a route of time synchronization in a network including apparatuses with different types of precision classes. [Solution to the Problem] A time transmission system includes BC nodes 200 with different types of apparatus performances, and multiple routes of PTP packets from GM nodes 101 and 102 to a BC node 220 via the BC node 200 are present. Each BC node 200 located upstream on a route performs notification of performance information indicating its apparatus performance to the BC node 200 located downstream with respect thereto. The BC node 220 includes a determination index calculation unit 11 that calculates a determination index for each route by referencing the performance information notified from the BC nodes 200 located upstream on each route, and a route selection unit 12 that selects a route for transmitting and receiving PTP packets from multiple routes of PTP packets to the BC node 220, based on the calculated determination index for each route.

Abstract: [Problem] An object is to obtain a time quality of another GM with high accuracy on the basis of a GM a time quality of which is known already. [Solution] A first TC 20 includes a time comparison unit 23 that calculates time difference information by comparing first time information of a first PTP processing unit 12 and second time information of a second PTP processing unit 22 with each other. In addition, a quality calculation device 5 measures time difference information until time difference information obtained by a time comparison unit 23 of the first TC 20 and time difference information obtained by a time comparison unit 43 of a second TC 40 match each other, and obtains a GM time quality of a second GM 30 on the basis of a transmission time error of the time transmission network 2 at a timing when both of pieces of the time difference information match each other.

Abstract: The accuracy of an offset value is improved by correcting an error in time synchronization caused by link asymmetry. PTP packets are exchanged between a master node 3 and a slave node 4 vis a first transmission device 1 connected to the master node 3 and a second transmission device 2 corresponding to the first transmission device 1 and connected to the slave node 4.

Abstract: A SW used in the time transmission system in which a master node and a slave node perform transmission and reception of a precision time protocol (PTP) packet via the SW and the time of the master node is synchronized based on time information of the transmission and reception includes a delay calculator that measures an intra-device delay between input and output of the PTP packet to and from the SW, and a delay information writing unit that appends the intra-device delay measured by the delay calculator to a packet subsequent to the PTP packet, and outputs the appended packet to an output destination of the PTP packet.

Abstract: [Problem] To reduce a time synchronization error caused by upstream and downstream asymmetry of the transmission path, improve wavelength band utilization efficiency, and reduce the required number of transponders. [Solution] An optical transmission device of each node simultaneously sends a plurality of signals having different wavelengths as delay measurement signals to a transmission path. The optical transmission device determines a delay value that reflects a propagation delay calculated based on an arrival time difference between a plurality of wavelengths in a signal received from another node, and determines a waiting time amount based on the delay value and the propagation delay. The optical transmission device notifies the other node of the delay value. Each optical transmission device outputs the received signal from the other node with a delay of the waiting time amount.

Abstract: A time synchronization mechanism is provided for reducing influences of link asymmetry between time synchronization devices. A second transmission device 2 includes: a transmission section 16 configured to transmit packets for delay calculation for a plurality of wavelengths to the corresponding time transmission device simultaneously; and a reception section 17 configured to calculate a propagation delay Dms on a path from the corresponding time transmission device to the second transmission device 2 based on a difference between the arrival times of the packets for delay calculation for the plurality of wavelengths received from the corresponding time transmission device, receive a propagation delay Dsm on a path from the second transmission device 2 to the corresponding time transmission device calculated by the corresponding time transmission device, and calculate a propagation delay Dmax that is larger than any of the propagation delay Dms and the propagation delay Dsm.

Abstract: [Problem] An object is to obtain a time quality of another GM with high accuracy on the basis of a GM a time quality of which is known already. [Solution] A first TC 20 includes a time comparison unit 23 that calculates time difference information by comparing first time information of a first PTP processing unit 12 and second time information of a second PTP processing unit 22 with each other. In addition, a quality calculation device 5 measures time difference information until time difference information obtained by a time comparison unit 23 of the first TC 20 and time difference information obtained by a time comparison unit 43 of a second TC 40 match each other, and obtains a GM time quality of a second GM 30 on the basis of a transmission time error of the time transmission network 2 at a timing when both of pieces of the time difference information match each other.

Abstract: [Problem to be Solved] Optimizing a route of time synchronization in a network including apparatuses with different types of precision classes. [Solution to the Problem] A time transmission system includes BC nodes 200 with different types of apparatus performances, and multiple routes of PTP packets from GM nodes 101 and 102 to a BC node 220 via the BC node 200 are present. Each BC node 200 located upstream on a route performs notification of performance information indicating its apparatus performance to the BC node 200 located downstream with respect thereto. The BC node 220 includes a determination index calculation unit 11 that calculates a determination index for each route by referencing the performance information notified from the BC nodes 200 located upstream on each route, and a route selection unit 12 that selects a route for transmitting and receiving PTP packets from multiple routes of PTP packets to the BC node 220, based on the calculated determination index for each route.

Abstract: [Problem] To select an optimal transmission path having a minimum total MTIE value of total MTIE values between a plurality of master apparatuses configured to transmit time information serving as a reference and a specific relay apparatus configured to receive the time information via a plurality of relay apparatuses to achieve time synchronization. [Solution] A time path selection apparatus 30 selects a transmission path employed for time synchronization, on the basis of a MTIE value evaluated in each of relay apparatuses 13 to 16, between master apparatuses 11 and 12 configured to transmit time information serving as a reference and a relay apparatus 15 or 16 at an edge configured to receive the time information via a relay apparatus 13 or 14 to achieve the time synchronization.

Abstract: [Problem] To provide a time synchronization mechanism that is not affected by link asymmetry between time synchronization devices.

Abstract: [Problem] A time synchronization mechanism with which an impact of link asymmetry between time synchronization devices is reduced is provided. [Solution] A SW 3 used in the time transmission system in which a master node 1 and a slave node 2 performs transmission and reception of a PTP packet via the SW 3 and the time of the master node 1 is synchronized based on time information of the transmission and reception includes a delay calculator 32 that measures an intra-device delay between input and output of the PTP packet to and from the SW 3, and a delay information writing unit 33 that appends the intra-device delay measured by the delay calculator 32 to a packet subsequent to the PTP packet, and outputs the appended packet to an output destination of the PTP packet.

Abstract: [Problem] It is possible to improve the quality of time information by suppressing a jump in time which arises when switching a transfer path in a BC apparatus to which transfer paths of time information of at least 2 systems are connected to an input side. [Solution] A time synchronization apparatus 20 is mounted on a BC apparatus 12c in which two systems of at least a 0-system route (0-system) and a 1-system route (1-system) are connected to an input side, and includes a time correction value holding unit 26 configured to hold a 0-system correction value in which a time error resulting from delay of UTC due to performance inherent to the BC apparatus is the same value as a time error accumulated on the 0-system side and a 1-system correction value in which the time error is the same value as a time error accumulated on the 1-system side.

Abstract: [Problem] To synchronize timings of transmitting and receiving a pulse signal (1 PPS signal) at a constant interval between communication apparatuses even in a case where an optical fiber connecting the communication apparatuses fluctuates in an optical characteristic and an optical fiber length. [Solution] The time synchronization system 20 transmits and receives a pulse signal at a constant interval between a local apparatus L (apparatus L) and a remote apparatus R (apparatus R) connected through the two-core bidirectional optical fibers F1 and F2 to synchronize time.

Abstract: A local device of a time synchronization system includes a path switching unit that connects respective remote devices using individual optical fibers and switches the respective optical fibers sequentially in a cyclic order, a counter unit, a phase difference memory unit, and a table unit. The counter unit counts a pulse signal P1d demodulated by a PPS demodulation unit to obtain a count value. The phase difference memory unit stores the count value as path information in association with a phase difference detected by a phase detection unit, and outputs the phase difference associated with this path information indicated by the count value to the variable delay unit. When the count value is input, the table unit outputs a path switching signal for switching to the next optical fiber in the cyclic order to the path switching unit and the path switching unit performs switching to the next optical fiber.

Abstract: [Problem] To reduce a total equipment cost. [Solution] A local device (20A) of a time synchronization system (10A) includes a path switching unit (33) that connects respective remote devices (40A1 to 40An) using individual optical fibers (60a to 60n) and switches the respective optical fibers (60a to 60n) sequentially in a cyclic order, a counter unit (31), a phase difference memory unit (30), and a table unit (32). The counter unit (31) counts a pulse signal P1d demodulated by a PPS demodulation unit (23) to obtain a count value (T1). The phase difference memory unit (30) stores the count value (T1) as path information in association with a phase difference (?1) detected by a phase detection unit (22), and outputs, when the count value (T1) is input, the phase difference (?1) associated with this path information indicated by the count value (T1) to the variable delay unit (24).