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Optically pumped cesium enabling ePRC and ePRTC Class B

Alain Michaud's ITSF 2017 slideshow outlines how new synchronization technology based on optical pumping can deliver major improvements in frequency stability.

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Optically pumped cesium enabling ePRC and ePRTC Class B

  1. 1. Optically pumped cesium enabling ePRC and ePRTC Class B Alain Michaud, director, R&D and PLM, time and frequency ITSF 2017
  2. 2. © 2017 ADVA Optical Networking. All rights reserved.2 Cesium clock as time source PRC (G.811) Frequency PRC : Cs or GNSS Sync network SSU SSU NE NE NE PRTC (G.8272) Frequency + phase PRTC : GNSS Sync network Packet slave clock Packet master clock NE NE NE ePRTC (G.8272.1) Frequency + phase GNSS Sync network Packet slave clock Packet master clock NE NE NE CsCombiner Cs as backup
  3. 3. © 2017 ADVA Optical Networking. All rights reserved.3 ePRTC: enhanced PRTC (ITU-T G.8272.1) What is enhanced? Cesium clock to filter GNSS instabilities: • Atmospheric interference • Solar storms • Equatorial diurnal ionospheric variation  30ns MTIE in GNSS locked mode Cesium clock: resiliency against GNSS outage  100ns MTIE over 14 days in holdover mode MTIE τ(s) 15ns 100ns 1ns 0.1 1 10 100 400k1k 10k 10ns 100k 1M 10M 100M 30ns 4ns 30ns 30ns 100ns 4ns
  4. 4. © 2017 ADVA Optical Networking. All rights reserved.4 Where is ePRC hiding? ePRTC (G.8272.1) Frequency + phase GNSS Sync network Packet slave clock Packet master clock NE NE NE Cs Combiner ePRTC ePRC (G.811.1) Frequency domain Requires 10-12 frequency accuracy (Achieved with magnetic cesium clocks) Cs
  5. 5. © 2017 ADVA Optical Networking. All rights reserved.5 ePRTC Class A holdover requirement ePRTC-A holdover spec Free running cesium oscillator Frequency of cesium made coherent to UTC in tracking mode (ePRTC) ePRTC Class A phase/time holdover measurement
  6. 6. © 2017 ADVA Optical Networking. All rights reserved.6 ePRTC G8272.1 – phase error in holdover Evolution toward Class B holdover Class B: requires a frequency accuracy below 1 x 10-14 ePRTC Class Holdover performance ePRTC-A 100ns over 14 days ePRTC-B 100ns over 80 days (project) Could also be a tighter error budget over a shorter period
  7. 7. © 2017 ADVA Optical Networking. All rights reserved.7 F=3,4 RFLaser Laser N S N S F=3,4 RF • Weak flux • Strong velocity selection (bent) • Magnetic deflection (atoms kicked off) • Typical performances: ADEV • 2.7 x 10-11 x t-1/2 • High flux (x100) • No velocity selection (straight) • Optical pumping (atoms reused) • Typical performances: ADEV • 3 x 10-12 x t-1/2 Improving frequency stability with optical pumping (versus magnetic deflection)
  8. 8. © 2017 ADVA Optical Networking. All rights reserved.8 Improving frequency stability with optical pumping (versus magnetic deflection) • Atomic energy states • Ground states (F=3,4) equally populated • Excited states (F’=2,3,4,5) empty • Switching between ground states F by RF interaction 9.192GHz without atomic selection (no useful differential signal) • Atomic preparation by magnetic deflection (loss of atoms) • Atomic preparation by optical pumping with laser tuned to F=4 F’=4 transition (gain of atoms) F’=5 F’=4 F’=3 F’=2 nRF = 9.192GHz F=4 F=3 133Cs atomic energy levels l = 852.1nm or nopt = 352THz Absorption Spontanousemission Cs beam Resonant cavity (Ramsey)
  9. 9. © 2017 ADVA Optical Networking. All rights reserved.9 Available commercial Cs clock products • Long-life magnetic Cs clock • Stability : 2.7 x 10-11 x t-1/2 • Floor : 5 x 10-14 • Lifetime : 10 years • High-performance magnetic Cs clock • Stability : 8.5 x 10-12 x t-1/2 • Floor : 1 x 10-14 • Lifetime : 5 years • High-performance and long-life optical clock • Stability : 3.0 x 10-12 x t-1/2 • Floor : 5 x 10-15 • Lifetime : 10 years Long-life MAGNETIC High-perf MAGNETIC Super-high-perf long-life OPTICAL ADEV: Allan Deviation Three generations of commercial clocks
  10. 10. © 2017 ADVA Optical Networking. All rights reserved.10 Decomposition of ePRTC holdover phase error budget Origin of phase error Note Required for ePRTC-B Initial phase error GNSS instabilities + clock stability +/- 30ns as per ePRTC G.8272.1 How to use only ±10ns? High-stab. GNSS+ High-stability clock Random phase excursions (holdover) White frequency noise + flicker frequency noise cesium clock Higher- stability clocks Typ. Φ excursion magnetic Typ. Φexcursion optical (±20ns) (±5ns) Phase drift due to initial clock freq. offset Which is a function of: - Clock stability @Tau > 1d - GNSS stability @Tau >1d Higher-stability GNSS + Higher-stability clock (long term) Required: Freq. error < 5 x 10-14 ePRTC-A Freq. error < 1 x 10-14 ePRTC-B White frequency noise Flicker frequency noise (floor) Initial frequency error + +
  11. 11. Thank You IMPORTANT NOTICE The content of this presentation is strictly confidential. ADVA Optical Networking 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 Optical Networking 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 Optical Networking.

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