In his ITSF 2020 session, Claude Besse explained how optical cesium offers the industry a new level of accuracy. He discussed how this ePRC+ technology’s outstanding frequency stability enables the deployment of ePRTC solutions that outperform even the most stringent recommendations, as well as how optical cesium offers significantly longer lifetime than existing cesium clocks.

1. New optical cesium: ePRC+ and ePRTC+ enabler
Claude Besse, PLM, time and frequency, Oscilloquartz, ADVA
ITSF, 3-5 November 2020 – Online

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Optical cesium achieves
superior performance
Midterm advantages for optical cesium due to
synergies with photonic assembly technologies
Both cesium clock technologies apply proven,
highly-reliable components
Optical cesium is improving utilization of Cs
atoms, leading to longer lifetime
Optical and magnetic cesium
Lifetime Performance
Reliability Production

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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:
• 3E-11 t-1/2
• 8 years
Stringent alignment (bent beam)
High flux (x100)
• No velocity selection (straight)
• Optical pumping (atoms reused)
Typical performances:
• 3E-12 t-1/2
• 10 years
Relaxed alignment (straight beam)
Magnetic deflection technology for ePRC Optical pumping technology for ePRC+
Cesium atomic clock, magnetic compared to optical

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Governmental response SolutionProblem
Highly stable atomic clocks are subject of national interest
Atomic clocks for resilient critical infrastructures
Jamming and spoofing create
risk for business continuity in
power networks
e.g., Galileo e.g., GPS
Dual constellations
Packet
network
GPS
Atomic clock
Redundancy and terrestrial sync
delivery from atomic clock providing
highly stable timing signal
Executive order on strengthening
national resilience through responsible
use of positioning, navigation, and
timing services.
February 2020
PRTC
ePRTC

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GNSS vulnerability
• Maintains highly accurate UTC
• Free for everyone but not everywhere
• Critical infrastructure will not scale with ever-
increasing amount of GNSS antennas
• Vulnerable source
• Interferences
• Intentional (jamming), unintentional
• Multipath, spoofing, GNSS outages
• Atmosphere (solar activities)
• Indoor and outdoor (urban canyons)
• UK goverment : A study of critical dependencies
https://www.gov.uk/government/publications/sa
tellite-derived-time-and-position-blackett-
review

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Telecommunication network reference
• Telecom operators, accurate phase sync for 5G
(ePRTC)
Critical infrastructure
• Power utilities, railways, transport, airports
Enterprise / data centers (ICPs) / finance
• Synchronization of distributed databases
• High-frequency trading
Defense
• Precise timing for security applications
• Highly accurate localization
Optical cesium as GNSS backup and for higher stability as well as better holdover
Markets

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ePRTC logical implementation model
• Locked to UTC-traceable source (GNSS), filtering GNSS (30ns MTIE)
• Phase time output is coherent with UTC phase time
• Frequency output is coherent with UTC allowing minimal drift in holdover mode
GNSS
Cesium
Stable freq. ref
~ Makes frequency
UTC-coherent (accuracy of GNSS)
and stable (Cs stability)
Improves time
(less jitter)

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Suggestion for ePRC+ improvement
Optical cesium outperform the G.811.1 ePRC spec (MTIE and TDEV)
MTIE TDEV

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Typical implementation (single channel)
Cesium as a backup to any GNSS event
GNSS
receiver
Clock
combiner PPS/PPS+ToD
GNSS
GNSS antenna
10Mhz
BITS
Sync-E
PTP
NTP
Cesium
clock

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Typical implementation (1+1)
Cesium as a backup to any GNSS event
GNSS
Receiver
Clock
Combiner PPS/PPS+ToD
GNSS
GNSS antennas
10Mhz
BITS
Sync-E
PTP
NTP
Clock
combiner
GNSS
receiver
Cesium
clock 1
Cesium
clock 2

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Optical cesium ePRC+ for ePRTC+
When our optical cesium is used with OSA ePRTC, it provides improved holdover
(OSA ePRTC+ holdover)
Will not drift more then 35nsec in 14 days!
Beginning of
holdover
Allowed drift
In holdover

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Optical cesium ePRC+ in ePRTC – holdover test result
Locked to GPS
and Cs
GPS
disconnected
Holdover
17ns drift
after 14 days !

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A major innovation in atomic cesium technology
Key takeaways
- Optical cesium provides better stability
and longer lifetime (no compromise
between lifetime and performance)
- Essential solution for backup to GNSS
with mobile networks, power utilities,
defense, among others
- Optimized ePRTC+ performance in
combined use with our GNSS receivers
- Common and unique remote
management

14. Thank you
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cbesse@oscilloquartz.com