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

Fibre frequency dissemination with a resolution below 10 -17 O. Lopez, A. Amy Klein, Ch. Daussy, and Ch. Chardonnet F. Narbonneau, M. Lours, and G. Santarelli Laboratoire de Physique des Lasers, LNE-SYRTE, Observatoire de Paris, Université Paris 13, Villetaneuse, 61, avenue de l’Observatoire France F-75014 Paris

Optical Fibre Link Secondary standard Primary standard SF 6 molecular beam H-maser/Cs fountain 28 THz 9.2 GHz 43 km LPL SF 6 BNM-SYRTE (Villetaneuse) (Paris) ν Femtosecond laser f rep frequency comb

� Two 43-km dedicated telecom fibers of the Paris metropolitan network • A few different sections of buried fibre cable • Splicing to ensure the continuity • 10 dB one way optical losses (@ 1.55 μ m) = 13 km telecom optical fibre of the urban france telecom paris network (44 km) SYRTE Optical Time Domain Reflectometry measurement Syrte / LPL (44 km) [ Fibre: 22 Index: 1,46500 λ =1553 nm pulse of 3 ms (07/20/02) ]

-13 10 Closed loop Overlapping Allan Deviation σ y ( τ ) Open loop -14 10 σ y ( τ ) -15 10 -14 10 -16 10 ~3 10 -14 τ -1/2 Frequency stability of the double -17 optical link 10 -15 10 0 1 2 10 10 10 LPL CO 2 /OsO 4 (30 THz) vs τ [s] 0 1 2 3 4 5 10 10 10 10 10 10 SYRTE CSO (11.9 GHz) τ [s] ν SF6 = 28 412 764 347 323.0 ± 1.4 Hz C. Daussy et al, Physical Review Letters, 94 , 203904, 2005. F.Narbonneau et al, Rev. of Scient. Instrum., 76 , 2006.

20 mW 100 DL detector 0.5 mW AM MHz 1.55µm detector Δφ SYRTE LPL Cryo. Oscill. Allan deviation of the relative Relative phase fluctuations variance des fluctuations relatives fluctuations relatives de phase entre les 2 fibres frequency between the two fibers between the 2 fibers over one day entre les 2 fibres sur 1 jour (86400 secondes) -0,0006 0.6 0.4 -0,0008 1E-15 1E-15 -0,0010 0.2 Δφ (mrd) 0 -0,0012 Δφ rds σ -0.2 -0,0014 1E-16 1E-16 -0.4 -0,0016 -0.6 -0,0018 1E-17 1E-17 0 20000 40000 60000 80000 100000 1 10 100 1000 10000 1 10 100 1000 10000 0 20000 40000 60000 80000 100000 secondes τ secondes F échantillon = 1 Hz seconds seconds

Phase compensation systems operating with 1 GHz carrier frequency Mixer Phase detection Band-pass filter @ 571.43(…) MHz 1 1 @ 428,57(…) MHz Reference source 10 10 Band-pass filter Mixer @ 1 GHz 100 MHz 1 GHz SAW 1 1 VCXO 7 7 Loop filter Frequency divider Laser Diode Band-pass filter Photodiode 3rd harmonic selection Band-pass filter Mixer Telecom optical fibre @ 1428,57(…) MHz Down-conversion 2,5 km BNM-SYRTE Laser Diode REMOTE DFB Laser Diode 1.55 µm AM 100 MHz Optical circulator Fibre 25 kms LOCAL detector LPL RF modulation detector thermal correction DFB Laser Diode 1.55 µm remote mechanical correction CRO CRO Ultra Low Noise Crystal Ultra Low Noise Crystal 1 km fibre 900 MHz 900 MHz Oscillator 100 MHz Oscillator 100 MHz x 10 x 10 x 10 x 10 CRO CRO 900 MHz 900 MHz 15 m fibre SAW Oscillateur SAW Oscillator 1 GHz 1 GHz detector DFB Laser Diode Data acquisition 1.55 µm local variance

User-end p φ + φ c Optical fibre link + Phase perturbation ref φ φ p φ c φ p + − ACTION ref Correction fiber ref Loop filter φ φ MECHANICAL HEATING φ p 2 − = RF process + Rx φ p Laser source Tx φ c 2 2 + φ c 2 + ref φ ref φ Reference signal

• Fast small phase correction by fibre stressing on a piezo ceramic High voltage 0 → 1000V, 15m of fibre (15 ps range, 400Hz BW) Voltage supply up to 1000 V Voltage supply up to 1000 V e e Muller et al. arXiv/0511072 Piezoelectric actuator Piezoelectric actuator Fast phase corrections by thermal excitation L + L L + L L L of Al or Au coated fiber HighVolt. drive D D D + D D + D • Slow phase fluctuations correction by fibre heating Copper wheel 30 � 60 ° C 4-km fibre 150 ps /°C, 6 ns dynamic range Phase shift

Optical feed-back parasitic effects • Reflection on connectors 10 and splicing along the link return signal(900 MHz) 0 • Stimulated Brillouin -10 Scattering (SBS) Power [dBm] forward beam SBS (1GHz) -20 • To avoid these effects we use two different -30 modulation frequencies • 1 GHz and 900 MHz -40 -50 0.8 0.9 1.0 1.1 1.2 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) 12 10 DGD [ps] 8 First ord. PMD 1(0.05)ps/ vintage km 6 (modern) fiber for our 86 km fiber the average DGD is about 7 ps and fluctuates on a time scale from 1000 to 30000 4 seconds. Forward and backward beams do not 2 experience the same delay the wavelengths 0 20 40 60 80 100 120 140 are different, the input polarization states time[h] at each end fluctuates independently

-15 10 σ y ( τ ) -16 10 -17 10 3 4 5 10 10 10 τ [s] Frequency stability floor due to PMD at 1 GHz and 86 km

By fast modulation of 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).

Polarization state vector Poincare's Sphere

Fibre optical link 2 x 43-km of the Urban telecom polarization network scrambler CRO ULNCO 900 MHz 100 MHz slow correction DFB LD x 10 1.55 µm fast correction ULNCO 100 MHz SAW 1 GHz CRO 900 MHz x 10 DFB LD 1.55 µm SAW 1 polarization GHz scrambler

Overlapping Allan Deviation σ y ( τ ) -14 10 -15 10 -16 10 -17 10 -18 10 0 1 2 3 4 5 10 10 10 10 10 10 Averaging time τ [s]

Phase noise spectral density of the system -90 complete link closed loop phase noise 2 /Hz] @ 1 GHz -100 -110 -120 S φ ( f ) [rad -130 -140 system phase noise -150 0 1 2 3 4 5 10 10 10 10 10 10 frequency [Hz]

Measurement scheme for a 186-km link 2 x 43 km in 2 x 25dB gain Urban telecom 2 x 25 km EDFA network fiber spool Electronic compensator Or optical compensator 2 x 25 km fiber spool

Overlapping Allan Deviation σ y ( τ ) -13 10 optical compensator electronic compensator -14 10 -15 10 -16 10 -17 10 -18 10 0 1 2 3 4 5 10 10 10 10 10 10 Averaging time τ [s]

86km distribution system @ 186 km distribution system @ 1 1GHz GHz 3-5 10 -15 @ 1s 1-3x10 -14 @ 1s Short-term ADEV 2-3x10 -18 @ 1 day ~<10 -17 @ 1 day Long-term ADEV • 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 μ m for frequency transfer (ANR contract) This work was partially supported by the European Space Agency (ESOC contract n°17367/03/D/SW(SC))

a full European ultra-stable optical a full European ultra-stable optical fiber link network ? fiber link network ? Univ. NPL Hannover LONDON PTB Braunschweig Telecom fibre network MPQ Munchen Univ. SYRTE-LPL Paris Berlin INRIM Torino