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Optical timing channel (OTC): Delivering sub-50ns over long-distance commercial WDM networks

At the NPL and BT webinar, Nir Laufer discussed timing for telecom networks. Providing an overview of Oscilloquartz's industry-leading portfolio of synchronization solutions, the presentation discussed new optical timing channel technology.

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Optical timing channel (OTC): Delivering sub-50ns over long-distance commercial WDM networks

  1. 1. Optical timing channel (OTC): Delivering sub-50ns over long-distance commercial WDM networks Nir Laufer, senior director, product line management, Oscilloquartz, ADVA September 2020
  2. 2. © 2020 ADVA. All rights reserved.22 Oscilloquartz (OSA) at a glance Innovation leader for timing distribution and assurance • An ADVA company • Focused on offering sync solutions for communications, government and enterprise applications • Longstanding relationship with customers worldwide since 1949! • Around 100 sync-focused partners in about 80 countries around the globe • State-of-the-art, end-to-end time, phase and frequency solutions • Excellence in timing delivery and assurance
  3. 3. © 2020 ADVA. All rights reserved.33 Common synchronization challenges – sub-1usec Mobile radio networks 1.1usec, 260nsec relative Financial trading 1usec Regulation (MIFID II), HFT Power utilities 1usec – PMU, fault location Data center infrastructure 1usec Broadcast networks 1usec How to make sync delivery more accurate and more resilient
  4. 4. © 2020 ADVA. All rights reserved.44 GNSS vulnerabilities and threats GNSS for timing Jamming and spoofing Obstruction Interference with transmitters at adjacent bands Atmospheric disturbance, solar activity GNSS segment errors
  5. 5. © 2020 ADVA. All rights reserved.55 Application area for OTC: aggregation network Core time base network Single-digit number of locations for large operator ePRTC-enabled, TE ≤ ±30ns Aggregation network Hundreds of locations for large operator PRTC-enabled, TE ≤ ±100ns Feeders to end application Thousands of locations for large operator TE ≤ ±1100ns Optical timing channel Optical timing channel 70ns budget ePRTC
  6. 6. © 2020 ADVA. All rights reserved.66 Core time base sites – ePRTC GNSS Receiver Clock Combiner PPS/PPS+ToD OSA 3230B ePRC cesium clock GNSS antennas OSA 5440 10MHz BITS SyncE PTP NTP Clock combiner GNSS receiver OSA 3350 ePRC+ cesium clock Carrier-grade, fully redundant HW Multi-band, multi- constellation GNSS PTP+SyncE Backup from peer site Peer core site ePRTC with cesium backups OSA 5405 Smart antenna Syncjack and GNSS assurance Advanced jamming and spoofing detection
  7. 7. © 2020 ADVA. All rights reserved.77 OTC Timing over ... Asymmetry is the biggest challenge! Timing over ... Optimization methods Time error Layer 3 (routed) Small packet size High (ms/µs) Layer 2 (switched) VLAN with high priority Middle (µs) Layer 1 (OTN) OTN buffer policing or in-band transmission Low (µs/ns) Layer 1 (transparent WDM) Single fiber working Lowest (ns) Asymmetry
  8. 8. © 2020 ADVA. All rights reserved.88 Timing device OTC regen ILA ROADM Terminal Cross-connect Terminal/ADM card Optical timing channel (OTC) The optical timing channel (OTC) achieves high-accuracy time distribution by PTP (IEEE 1588) via Gigabit Ethernet over dedicated wavelengths on a single fiber OTC has minimal constant link asymmetry due to bidirectional transmission on a single fiber; further compensation is supported OTC is independent from other layers (IP, Ethernet, OTN, reconfigurable optical layer) practically eliminating dynamic time errors OTC does not change optical network engineering rules and is just an overbuild to the optical transport layer
  9. 9. © 2020 ADVA. All rights reserved.99 OpticallinesystemIntermediatesite Node with timing access Terminal west Terminal east PTP over optical timing channel Payload traffic Timing device featuring High-accuracy PTP boundary clock type D BiDi transceivers OTC provides ample optical budget: up to 30dB between two BiDi transceivers Dispersion is irrelevant at GbE line rate Line terminal
  10. 10. © 2020 ADVA. All rights reserved.1010 Impact of chromatic dispersion can be efficiently compensated Same east-west wavelength Asymmetric delay results in a deterministic time error Chromatic dispersion creates asymmetric delay 100km of fiber with dispersion of18ps/(nm km) l1 = 1.605µm l2 = 1.615µm 𝑐𝑇𝐸 ≈ 100𝑘𝑚 2 10𝑛𝑚 18𝑝𝑠 𝑛𝑚 𝑘𝑚 = 9000𝑝𝑠 = 9𝑛𝑠 85km 65km70km 82km Time error from chromatic dispersion: 27.2ns Constant and deterministic
  11. 11. © 2020 ADVA. All rights reserved.1111 50km_aOSC OSCOSC OSC OSC Paragon Neo OSA 5430 5WCAOTC Patch-through Master port Slave port OSC OTC accuracy measurment 3GU/1605LGBE/1615V 3GU/1605L SFP/GBE/1605V GBE/1615V GBE/1615V MALPB-OSC-C MTP-OSC-C MTPB-OSC-C MTPB-OSC-C MTP-OSC-C MTPB-OSC-C 50km_b 65km_a 65km_b OSA 5421 GBE/1310 GBE/1310 210 cm 𝑐𝑇𝐸 ≈ 100𝑘𝑚 2 ∗ −10𝑛𝑚 18𝑝𝑠 𝑛𝑚 𝑘𝑚 = − 9000𝑝𝑠 = − 9𝑛𝑠 𝑐𝑇𝐸 ≈ 130𝑘𝑚 2 ∗ −10𝑛𝑚 18𝑝𝑠 𝑛𝑚 𝑘𝑚 = 11700𝑝𝑠 = −11.7𝑛𝑠 TE within 15nsec
  12. 12. © 2020 ADVA. All rights reserved.1212 PTP GM/BC type D / slave NTP server SSUePRTC Sync probe G.8265.1 EnterpriseG.8275.2 G.8275.1 2G/3G/ 4G/5G FDD BS DOCSIS 3.1 MIFID ii 5G-NR/LTE TDD/LTE-A BS NTP61850-9-3/ C37.238 Smart grid OSA 54XX – Synchronization “Swiss Army knife“ OSA 542X OSA 5430 OSA 5440
  13. 13. © 2020 ADVA. All rights reserved.1313 The challenge – transmission asymmetry PTP (IEEE 1588) recovered time is affected by network asymmetry: 1) Forward and backward paths use different fibers and therefore have different lengths (constant time error about 2.5ns/m) 2) Dynamically changing intermediate (Ethernet) processing on the paths 3) Forward and backward transmission use the same fiber but slightly different wavelengths (minor constant time error due to dispersion of about 0.09ns per km) OTC eliminates (1) – (2). The error according to (3) is small and constant and can be compensated
  14. 14. © 2020 ADVA. All rights reserved.1414 Two CWDM slots per bidirectional channel Standard transceivers have two fiber connectors (TX and RX) One CWDM slot per bidirectional channel BiDi transceivers have one fiber connector with TX and RX pre-multiplexed in the transceiver BiDi transceiversStandard transceivers Running on the same fiber, forward and backward paths have exactly the same length; there is only marginal asymmetric delay BiDi transceivers CWDM Slot TX CWDM Slot RX CWDM Slot TX RX OTC
  15. 15. Thank you IMPORTANT NOTICE The content of this presentation is strictly confidential. ADVA is the exclusive owner or licensee of the content, material, and information in this presentation. Any reproduction, publication or reprint, in whole or in part, is strictly prohibited. The information in this presentation may not be accurate, complete or up to date, and is provided without warranties or representations of any kind, either express or implied. ADVA g shall not be responsible for and disclaims any liability for any loss or damages, including without limitation, direct, indirect, incidental, consequential and special damages, alleged to have been caused by or in connection with using and/or relying on the information contained in this presentation. Copyright © for the entire content of this presentation: ADVA. nlaufer@adva.com

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