公开(公告)号：US20220294549A1

公开(公告)日：2022-09-15

申请号：US17428240

申请日：2020-02-06

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Masahiro NAKAGAWA ,  Kaoru ARAI ,  Hiroki SAKUMA ,  Shunichi TSUBOI

IPC: H04J3/06 ,  H04L7/00

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. The second transmission device 2 includes: a transmission section 16 configured to transmit PTP packets for a plurality of wavelengths to the corresponding transmission device simultaneously; and a reception section 17 configured to calculate a propagation delay Dms on a path from the corresponding transmission device to the second transmission device 2 based on a difference between the arrival times of the PTP packets for the plurality of wavelengths received from the corresponding transmission device, and provide the propagation delay Dms to the slave node 4 as a correction parameter used in a process of synchronizing the time of the slave node 4.

公开(公告)号：US20210058223A1

公开(公告)日：2021-02-25

申请号：US16968062

申请日：2019-02-15

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Hiroki SAKUMA ,  Kaoru ARAI ,  Ryuta SUGIYAMA ,  Takaaki HISASHIMA ,  Shunichi TSUBOI ,  Osamu KUROKAWA ,  Kazuyuki MATSUMURA

IPC: H04L7/00 ,  G04G7/00 ,  G06F1/14

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. A propagation delay amount τ1 in the fiber F1 is calculated, from a proportional relationship between T1 and T2 and a proportional relationship of τud and τ1, where T1 represents a propagation delay time difference between a pulse signals P1 and P4 of an identical wavelength λ1 returned after transmitting a pulse signal P1 of wavelength λ1 and a pulse signal P2 of wavelength λ2 different from λ1 to the remote apparatus R, T2 represents a propagation delay time difference between the pulse signal P1 of wavelength λ1 and a pulse signal P3 of wavelength λ2, and τud represents the round-trip delay time between the apparatuses L and R. The pulse signals P1 and P2 are transmitted with a time difference td corresponding to a difference between the current and last calculated propagation delay amounts τ1 being set so that the difference is zero.

公开(公告)号：US20230288182A1

公开(公告)日：2023-09-14

申请号：US18019530

申请日：2020-08-04

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Hiroki SAKUMA ,  Kaoru ARAI ,  Ryuta SUGIYAMA ,  Tomoya AKATSUKA ,  Katsuya OGURI

IPC: G01B9/02003 ,  G01B9/02015 ,  G01B9/02001 ,  G01B9/02

CPC classification number: G01B9/02003 ,  G01B9/0203 ,  G01B9/02011 ,  G01B9/02083 ,  G01B2290/70

Abstract: An optical complex amplitude measurement apparatus causes a polarization controller to perform control of making a polarized beam of a signal beam having a frequency that is output from a first laser and then passes through a measurement target match with a polarized beam of a reference beam from a second laser. A spatial filter extracts, from the matched signal beam, a plane wave component in which a wave front is distorted due to the passage, and outputs a signal beam having the frequency. The second laser performs a phase synchronization control of a frequency of the reference beam such that a frequency difference due to multiplexing of the signal beam and the reference beam by a homodyne interferometer becomes 0. The controlled reference beam and the signal beam from the polarization controller are multiplexed by a beam splitter.

公开(公告)号：US20220376783A1

公开(公告)日：2022-11-24

申请号：US17776059

申请日：2019-11-19

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Hiroki SAKUMA ,  Kaoru ARAI ,  Ryuta Sugiyama

IPC: H04B10/071 ,  H04B10/11

Abstract: A receiver (12) includes at least a spatial light modulation unit (12a), splitters (12b to 12d), a spatial filtering unit (12h), and a wavefront measurement unit (12i). The splitters (12b to 12d) transmit and reflect reference signal light of a reference optical frequency received via space (15) after being transmitted from a transmitter 11. The spatial filtering unit (12h) extracts a plane wave component, which is a signal component other than distortions, from the reflected light and outputs the extracted light as reference light. The wavefront measurement unit (12i) measures a wavefront due to the interference between the reference light and the reflected and transmitted signal light to detect a wavefront distortion of the reference signal light. The spatial light modulation unit (12a) wavefront-modulates the reference signal light received from the transmitter (11) into a plane wave without wavefront distortions with a reversed wavefront distortion obtained by reversing the detected wavefront distortion. That is, the wavefront modulation corrects the reference signal light into a plane wave without wavefront distortions.

公开(公告)号：US20220103281A1

公开(公告)日：2022-03-31

申请号：US17429172

申请日：2020-02-06

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Masahiro NAKAGAWA ,  Kaoru ARAI ,  Hiroki SAKUMA ,  Shunichi TSUBOI

IPC: H04J3/06

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. The reception section 17 transmits a received PTP packet to a slave node 4 after waiting for a waiting delay Wms that is calculated by subtracting the propagation delay Dms from the propagation delay Dmax.

公开(公告)号：US20170324472A1

公开(公告)日：2017-11-09

申请号：US15526835

申请日：2015-11-27

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Kei KITAMURA ,  Takafumi HAMANO ,  Takashi KOTANIGAWA ,  Kaoru ARAI ,  Masahiro YOKOTA ,  Hideki MAEDA ,  Yoshiaki YAMADA ,  Takuya OHARA ,  Kengo SHINTAKU

IPC: H04B10/032 ,  H04J3/16

CPC classification number: H04B10/032 ,  H04B1/74 ,  H04B10/03 ,  H04J3/00 ,  H04J3/14 ,  H04J3/16

Abstract: A framer in a transmission device allocates plural optical channel time slots to a plurality of logical prioritized paths. It allocates received client signals to the allocated time slots, and transmits the client signals by a plurality of optical subcarriers that use a plurality of optical wavelengths corresponding to the plurality of time slots. The framer includes: a time slot allocation unit that, in a case where an optical wavelength corresponding to a time slot allocated to a logical path having a high transmission priority is not used, allocates at least one of the plurality of time slots to the logical path having the high transmission priority while the time slot corresponding to the unused optical wavelength is avoided, to change the time slot allocated to the logical path having the high transmission priority.

公开(公告)号：US20220407607A1

公开(公告)日：2022-12-22

申请号：US17777313

申请日：2019-11-19

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Hiroki SAKUMA ,  Kaoru ARAI ,  Ryuta Sugiyama

IPC: H04B10/67 ,  H04B10/572

Abstract: A second transceiver (22) includes a guide light source (22c), a photorefractive crystal (22a), and a frequency control unit (22e). The guide light source (22c) emits guide light (Y3). A double phase conjugate mirror (22m) is formed in a crystal (22a) by scattering of reference signal light (Y1), which has a frequency different from that of the guide light and is incident on the crystal via space (15) after being transmitted from a first transceiver (21) which is a transceiver on the other side, and the guide light that is incident on the crystal in a reverse direction to that of the reference signal light. A frequency control unit (22e) couples the reference signal light emitted from the crystal (22a), which is phase-conjugate light of the guide light generated by the mirror (22m), to an optical fiber (13b).

公开(公告)号：US20220060310A1

公开(公告)日：2022-02-24

申请号：US17413863

申请日：2019-12-06

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Kaoru ARAI ,  Hiroki SAKUMA ,  Masahiro NAKAGAWA ,  Shunichi TSUBOI

IPC: H04L7/00 ,  H04J3/06 ,  H04W56/00 ,  H04W40/02

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.

公开(公告)号：US20210302499A1

公开(公告)日：2021-09-30

申请号：US17267161

申请日：2019-07-16

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Takaaki HISASHIMA ,  Hiroki SAKUMA ,  Kaoru ARAI ,  Ryuta SUGIYAMA ,  Shunichi TSUBOI ,  Osamu KUROKAWA ,  Kazuyuki MATSUMURA

IPC: G01R31/317 ,  H03K5/26 ,  H03K5/00 ,  H03K5/1252 ,  G06F1/12

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.

公开(公告)号：US20170257169A1

公开(公告)日：2017-09-07

申请号：US15528629

申请日：2015-11-27

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Kei KITAMURA ,  Takashi KOTANIGAWA ,  Takafumi HAMANO ,  Kaoru ARAI ,  Masahiro YOKOTA ,  Hideki MAEDA ,  Yoshiaki YAMADA ,  Takuya OHARA ,  Kengo SHINTAKU

IPC: H04B10/50 ,  H04J14/08

CPC classification number: H04B10/50 ,  H04B10/03 ,  H04J3/00 ,  H04J3/16 ,  H04J14/08

Abstract: There is provided a tray which is connected to a plurality of transmitters that multicarrier-transmit a plurality of parallel signals by optical subcarriers. The framer selects time slots to be allocated to a path to be accommodated such that the number of optical subcarriers corresponding to the time slots satisfies a predetermined condition on the basis of empty time slots which are specified by path accommodation information indicating a correspondence between paths allocated to a client signal and time slots in a signal frame and the optical subcarriers corresponding to the empty time slots indicated by time slot information indicating a correspondence between the time slots and the optical subcarriers, and sets the selected time slot in the path accommodation information. The framer sets a client signal to the time slots on the basis of the path accommodation information.