A method is described for providing a universal time in a control unit. The universal time is generated by a timer of the control unit or is received via a communication link from at least one external unit, the universal time being transmitted directly or as at least two time stamps to at least one component for ascertaining time deviations. Furthermore, a control unit, a computer program and a machine-readable storage medium are also described.

[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. Further, a failure restoration detection unit 23 configured to detect a failure in the 0-system or the 1-system, a time calculation unit 24 configured to perform correction by subtracting a 1-system correction value relating to a normal 1-system from UTC having time error accumulated on the normal 1-system side, when a failure in the 0-system is detected, and a path switching unit 25 configured to switch to the normal 1-system side such that the UTC after correction is transferred, when the failure is detected, are included.

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.

A time-synchronization system according to the present disclosure includes a relay apparatus (10) configured to perform time-synchronization with a master apparatus (30) through a transmission system of which a transmission delay changes depending on a transmission direction, and a relay apparatus (20) configured to perform time-synchronization with the relay apparatus (10), in which the relay apparatus (20) transmits information about a difference between first time information obtained by performing time-synchronization with the relay apparatus (10) and second time information obtained from a time-synchronization source to the relay apparatus (10), and the relay apparatus (10) corrects third time information obtained by performing time-synchronization with the master apparatus (30) by using the information about the difference, and performs time-synchronization with a slave apparatus (50) by using the corrected third time information.

A receiving apparatus is provided. The receiving apparatus includes circuitry configured to receive reference time information and metadata including information for executing processing related to the reference time information. The circuitry is configured to execute processing related to the reference time information based on the metadata. The metadata includes a first offset value between the reference time information and a discontinuous time, a second offset value between the discontinuous time and a local time, and a date and time at which a change in a daylight savings time (DST) status is to occur. The local time is determined based on the reference time information and the metadata.

A receiving apparatus is provided. The receiving apparatus includes circuitry configured to receive reference time information and metadata including information for executing processing related to the reference time information. The circuitry is configured to execute processing related to the reference time information based on the metadata. The metadata includes a first offset value between the reference time information and a discontinuous time, a second offset value between the discontinuous time and a local time, and a date and time at which a change in a daylight savings time (DST) status is to occur. The local time is determined based on the reference time information and the metadata.

[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. 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.

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

[Solution] A DC 4 used in a time transmission system that transmits and receives a PTP packet between a master node 1 and a slave node 2 via the DC 4 and synchronizes time of the slave node 2 based on time information on the transmission and reception includes a PTP clock unit 12 that synchronizes time information by the arrived PTP packet, a frequency clock unit 21 that synchronizes time information by a frequency signal, a delay setting unit 22 that sets, such that a transmission delay of the PTP packet between the master node 1 and the slave node 2 becomes a setting delay Lmax, a waiting time of the PTP packet based on a time difference between a departure time of the PTP packet and an arrival time of the PTP packet at the DC 4, which is determined from the time information of the frequency clock unit 21, and a time adjustment unit 26 that corrects a time shift from reference time in the time information of the frequency clock unit 21 based on the time information of the PTP clock unit 12.

[Problem] To determine a time difference between clocks which, for example, are placed far apart from each other with high accuracy at low cost.

[Solution] In a time comparison system 20, an intermediate station 21 disperses a single optical signal 21c in the spatial region using the optical complex amplitude modulation to simultaneously transmit the optical signal 21c to a plurality of comparative stations 22 and 23 apart from each other. The intermediate station 21 transmits the optical signal 21c while changing the transmission angle using phase modulation, performs intensity scanning for the reflected light c1 of the optical signal 21c, and detects the peak intensity to determine the directions of the comparative stations 22 and 23. The reflected light c1 of the optical signal 21c transmitted to the comparative stations 22 and 23 of which the direction have been determined, is detected to determine a round-trip propagation delay time between the intermediate station 21 and each of the comparative stations 22 and 23. The difference calculation unit 25 calculates a sum of time difference between each of times to and tb associated with the comparative stations 22 and 23 and the time tc associated with the intermediate station 21, and the determined propagation delay time to determine time information of each of the comparative stations 22 and 23. Based on the result of subtracting, from the time information of the comparative stations 22, the time information of the comparative stations 23, the time difference between the comparative stations 22 and 23 is determined.

[Problem] To determine a time difference between clocks which, for example, are placed far apart from each other with high accuracy at low cost.

[Solution] In a time comparison system 20, an intermediate station 21 disperses a single optical signal 21c in the spatial region using the optical complex amplitude modulation to simultaneously transmit the optical signal 21c to a plurality of comparative stations 22 and 23 apart from each other. The intermediate station 21 transmits the optical signal 21c while changing the transmission angle using phase modulation, performs intensity scanning for the reflected light c1 of the optical signal 21c, and detects the peak intensity to determine the directions of the comparative stations 22 and 23. The reflected light c1 of the optical signal 21c transmitted to the comparative stations 22 and 23 of which the direction have been determined, is detected to determine a round-trip propagation delay time between the intermediate station 21 and each of the comparative stations 22 and 23. The difference calculation unit 25 calculates a sum of time difference between each of times to and tb associated with the comparative stations 22 and 23 and the time tc associated with the intermediate station 21, and the determined propagation delay time to determine time information of each of the comparative stations 22 and 23. Based on the result of subtracting, from the time information of the comparative stations 22, the time information of the comparative stations 23, the time difference between the comparative stations 22 and 23 is determined.