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Stable distribution of low jitter frequency standards over optical fiber networks

Stable distribution of low jitter frequency standards over optical fiber networks. David Jones Department of Physics and Astronomy University of British Columbia Vancouver, BC V6T 1Z1 Canada. Jason Jones, and Jun Ye JILA, National Institute of Standards and Technology

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Stable distribution of low jitter frequency standards over optical fiber networks

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  1. Stable distribution of low jitter frequency standards over optical fiber networks David Jones Department of Physics and Astronomy University of British Columbia Vancouver, BC V6T 1Z1 Canada Jason Jones, and Jun Ye JILA, National Institute of Standards and Technology and University of Colorado, Boulder, CO 80309 USA Co-workers Darren Hudson (JILA) Jan Hall (JILA) Steve Cundiff (JILA) Leo Holberg et al (NIST) Funding CFI,NSERC NIST,ONR

  2. Enabling Optical Clock Comparisons NIST Boulder Labs L. Holberg, J. Bergquist, S. Jefferts JILA at CU Jun Ye, Jan Hall ~3.5 km Fiber Link • Hydrogen Maser Ensemble • Hg+ and Al+ Ion Optical Standards • Calcium Optical Standard • Cesium Fountain Clock • Yb… • Iodine Optical Standard • Rb Spectroscopy • Sr Spectroscopy • Sr Optical Standard… • Comparison yields… • Identification of systematic errors in experimental setup • Possibility of measuring shifts in fundamental constants (fine structure constant, etc) • …

  3. Metrics for Performance Allan Deviation -typically used by metrology community as a measure of (in)stability -evaluates performance over longer time scales (> 1 sec or so) Timing jitter -typically used by ultrafast community -measured in time or frequency domains -measure of short-term stability ( < 10 sec)

  4. Allan Deviation Test Clock Master Clock Frequency counter Allan Deviation -typically used by metrology community as a measure of (in)stability -evaluates performance over longer time scales (> 1 sec or so) -can distinguish between various noise processes -indicates stability as a function of averaging time

  5. Dispersion-compensation fiber, 1.2 km Dispersion-shifted fiber (DSF), 4.5 km feedback Frequency comparison 8 frep 8 frep Installed SMF (roundtrip), 7 km Adjustable delay line: Large dynamic range, fast action f Stabilization of Transmission Fiber Mode-locked fiber laser Adjustable delay line remote 81 frep 81 frep local EDFA To reduce pulse stretching, transmit through: • Dispersion-compensation fiber w/ installed SMF • OR • Dispersion-shifted fiber Complete dispersion cancellation of 50 km transmission fiber demonstrated using a pulse shaper. Z. Jiang et al., Opt. Lett. 30, 1449 (2005).

  6. Stabilized Distribution Over 7 km • Dispersion shifted fiber (or dispersion compensation) allows reduced average power, reducing detector instability • Low bandwidth feedback (100 Hz) measurement-limited stability achieved (7 x 10-15 at 1 s)

  7. Timing jitter of installed fiber network w/ stabilization • Noise floor limited by RF amps, evident by removing one • Two limiting conditions: • Microwave noise floor • decrease microwave amplification by going to resonant photo-detection • leave microwave domain for optical detection • Uncompensated high frequency noise • Develop higher speed actuators (intra-cavity EOMs)

  8. Intra-cavity EOM for high-bandwidth stabilization Hudson, Holman, Jones, Ye and Jones, Opt Lett. • Use a bulk (non-resonant) LiNb03 as phase modulator as high speed actuator • Synchronization of two local fs lasers: 10 fs of jitter (1 Hz to 100 kHz) Master Laser (31 MHz) Slave Laser (93 MHz) Feedback

  9. Synchronization of repetition rate to local laser 10 fs

  10. Remote Synchronization 7 km installed fiber

  11. Local synchronization (10 fs) • (16 fs integrated to Nyquist frequency) • Link stabilization in-loop (16 fs) • Remote synchronization of two independent lasers • (20 fs)

  12. Cross Correlation of Local and Remote Lasers 50 MHz detection bandwidth • Local synchronization 50 MHz detection bandwidth • Remote synchronization

  13. RF Detection Limits • For 100 mW of detected optical power gives -48 dBm RF power at 81st harmonic (~8 GHz). At these levels, -Johnson (thermal) Noise of -129 dBc/Hz (4.7 fs of jitter to 100 kHz) -Shot Noise of -132 dBc/Hz (3.3 fs of jitter to 100 kHz)

  14. Dispersion-compensation fiber, 1.2 km Dispersion-shifted fiber (DSF), 4.5 km Frequency comparison 8 frep 8 frep Installed SMF (roundtrip), 7 km f Improved detection schemes • Not really using full benefit of ultrashort pulses in current microwave detection scheme Mode-locked fiber laser Adjustable delay line remote 81 frep 81 frep local EDFA • Optical error signal detection: • -could use sharp rising edge for cross-correlation schemes: but not easily accomplished in this case • -optical hetero-dyne at spectral extremes (optical error signal detection)

  15. Optical Error Signal Detection Remote (slave) comb Loop filter remote comb with synchronized frep Delivered comb AWG lred lblue • Present work at UBC • Optical for increased sensitivity, while beat detection is at ~100 MHz • Detection scheme shown in remote synchronization context • …but can be modified to deliver stabilized comb

  16. Performance Limits for RF Phase Noise Phase noise power spectral density:

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