Fibre frequency dissemination with a resolution below 10 -17 O. - - PowerPoint PPT Presentation

• O. Lopez, A. Amy Klein, Ch. Daussy, and Ch. Chardonnet
• F. Narbonneau, M. Lours, and G. Santarelli

Laboratoire de Physique des Lasers, Université Paris 13, Villetaneuse, France LNE-SYRTE, Observatoire de Paris, 61, avenue de l’Observatoire F-75014 Paris

Fibre frequency dissemination with a resolution below 10-17

Primary standard

H-maser/Cs fountain 9.2 GHz

Secondary standard

SF6 molecular beam 28 THz

LPL (Villetaneuse) BNM-SYRTE (Paris)

Optical Fibre Link 43 km

frep

Femtosecond laser frequency comb ν

SF6

SYRTE

= 13 km

telecom optical fibre

• f the urban france telecom

paris network (44 km)

• A few different sections of buried fibre cable
• Splicing to ensure the continuity
• 10 dB one way optical losses (@ 1.55 μm)

Two 43-km dedicated telecom fibers of the Paris metropolitan network

Optical Time Domain Reflectometry measurement Syrte / LPL (44 km) [Fibre: 22 Index: 1,46500 λ=1553 nm pulse of 3 ms (07/20/02)]

10 10

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• 14

Closed loop Open loop

Overlapping Allan Deviation σy(τ)

τ[s]

Frequency stability of the double

• ptical link

10 10

1

10

2

10

• 15

10

• 14

10

• 13

σy (τ)

τ [s]

~3 10-14 τ-1/2

LPL CO2/OsO4 (30 THz) vs SYRTE CSO (11.9 GHz)

• C. Daussy et al, Physical Review Letters, 94, 203904, 2005.

F.Narbonneau et al, Rev. of Scient. Instrum., 76, 2006. νSF6= 28 412 764 347 323.0 ± 1.4 Hz

20000 40000 60000 80000 100000

• 0,0018
• 0,0016
• 0,0014
• 0,0012
• 0,0010
• 0,0008
• 0,0006

Féchantillon = 1 Hz fluctuations relatives de phase entre les 2 fibres sur 1 jour (86400 secondes) Δφ rds secondes

Relative phase fluctuations between the 2 fibers over one day seconds

0 20000 40000 60000 80000 100000

0.6 0.4 0.2

• 0.2
• 0.4
• 0.6

Δφ (mrd) DL 1.55µm AM

SYRTE

100 MHz detector

LPL Δφ

0.5 mW 20 mW

detector

1 10 100 1000 10000 1E-17 1E-16 1E-15

variance des fluctuations relatives entre les 2 fibres

σ

τ secondes

1 10 100 1000 10000 Allan deviation of the relative frequency between the two fibers

1E-15 1E-16 1E-17

seconds

Cryo. Oscill.

Laser Diode RF modulation Optical circulator Laser Diode Photodiode 1 7 1 7 1 10 1 10 Telecom optical fibre 2,5 km 1 GHz SAW 100 MHz VCXO Loop filter Mixer Down-conversion Mixer Phase detection Mixer Frequency divider Band-pass filter 3rd harmonic selection Band-pass filter @ 571.43(…) MHz Reference source @ 1 GHz Band-pass filter @ 1428,57(…) MHz Band-pass filter @ 428,57(…) MHz

BNM-SYRTE DFB Laser Diode 1.55 µm AM 100 MHz LPL detector Ultra Low Noise Crystal Oscillator 100 MHz SAW Oscillator 1 GHz Ultra Low Noise Crystal Oscillator 100 MHz SAW Oscillateur 1 GHz x 10 x 10 Data acquisition variance DFB Laser Diode 1.55 µm local detector detector thermal correction mechanical correction 1 km fibre 15 m fibre DFB Laser Diode 1.55 µm remote CRO 900 MHz CRO 900 MHz x 10 x 10 CRO 900 MHz CRO 900 MHz

LOCAL REMOTE

Fibre 25 kms

Phase compensation systems

• perating with 1 GHz carrier frequency

Reference signal RF process + Rx Laser source Tx

Optical fibre link

ref

φ

c ref

φ φ +

p c ref

φ φ φ + +

p c ref

φ φ φ 2 2 + +

p c

φ φ 2 2 − =

Phase perturbation

φp

Loop filter

HEATING MECHANICAL ACTION

p ref

φ φ −

User-end

Correction fiber

• Fast small phase correction by fibre stressing on a piezo ceramic
• Slow phase fluctuations correction by fibre heating

Piezoelectric actuator Voltage supply up to 1000 V Piezoelectric actuator Voltage supply up to 1000 V

Copper wheel 30 60 °C 4-km fibre 150 ps /°C, 6 ns dynamic range

L L + L e D D + D L L + L e D D + D

HighVolt. drive

Phase shift High voltage 0 → 1000V, 15m of fibre (15 ps range, 400Hz BW)

Muller et al. arXiv/0511072 Fast phase corrections by thermal excitation

• f Al or Au coated fiber

Optical feed-back parasitic effects

• Reflection on connectors

and splicing along the link

• Stimulated Brillouin

Scattering (SBS)

• To avoid these effects we

use two different modulation frequencies

• 1 GHz and 900 MHz

0.8 0.9 1.0 1.1 1.2

• 50
• 40
• 30
• 20
• 10

10

forward beam SBS (1GHz) return signal(900 MHz) Power [dBm] frequency [GHz]

PMD (polarization mode dispersion) is caused by the birefringence of the optical fiber due to asymmetry of the fiber (stable in time) mechanical stress on the fiber due to movement or temperature (varies in time stochastically) First ord. PMD 1(0.05)ps/ vintage (modern) fiber for our 86 km fiber the average DGD is about 7 ps and fluctuates

• n a time scale from 1000 to 30000

seconds. Forward and backward beams do not experience the same delay the wavelengths are different, the input polarization states at each end fluctuates independently

20 40 60 80 100 120 140

2 4 6 8 10 12

DGD [ps] time[h]

km

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σy(τ) τ [s]

Frequency stability floor due to PMD at 1 GHz and 86 km

By fast modulation

• f

the input polarization with 3 non harmonically related frequencies we explore all polarization states in the fiber averaging the PMD. The modulation frequencies are close to the piezo electric resonances ranging from 30 to 200 kHz to drive with low voltages (a few Volts) a complete polarization flip of π.

Two polarization scrambler are placed at each end of the optical link. In this way forward and backward beams explore all polarization states on a time scale shorter than the round trip delay (~1ms).

Poincare's Sphere

Polarization state vector

Fibre optical link 2 x 43-km of the Urban telecom network

DFB LD 1.55 µm SAW 1 GHz x 10 ULNCO 100 MHz CRO 900 MHz

polarization scrambler

ULNCO 100 MHz SAW 1 GHz x 10 DFB LD 1.55 µm

slow correction

CRO 900 MHz

polarization scrambler

fast correction

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Overlapping Allan Deviation σy(τ) Averaging time τ[s]

Phase noise spectral density of the system

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• 140
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complete link closed loop phase noise system phase noise Sφ ( f ) [rad

2/Hz] @ 1 GHz

frequency [Hz]

Electronic compensator Or

• ptical

compensator 2 x 43 km in Urban telecom network 2 x 25 km fiber spool 2 x 25dB gain EDFA 2 x 25 km fiber spool

Measurement scheme for a 186-km link

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Overlapping Allan Deviation σy(τ) Averaging time τ[s]

• ptical compensator

electronic compensator

• In the short term :study of a longer distance link (3-400km)

using a microwave carrier (9 GHz) optical link with externally modulated laser diodes and optical amplifiers.

• Near future : single tone optical carrier a 1.55 μm for frequency

transfer (ANR contract)

86km distribution system @ 1GHz 186 km distribution system @ 1 GHz

Short-term ADEV

3-5 10-15 @ 1s 1-3x10-14 @ 1s

Long-term ADEV

2-3x10-18 @ 1 day ~<10-17 @ 1 day

This work was partially supported by the European Space Agency (ESOC contract n°17367/03/D/SW(SC))

Univ. Hannover SYRTE-LPL Paris NPL LONDON

Telecom fibre network

MPQ Munchen INRIM Torino PTB Braunschweig

a full European ultra-stable optical a full European ultra-stable optical fiber fiber link network ? link network ?

Univ. Berlin