High-Accuracy and Fast Measurement of Optical Transfer Delay

Li, Shupeng; Qing, Ting; Fu, Jianbin; Wang, Xiangchuan; Pan, Shilong

doi:10.1109/tim.2020.3011585

Cited by 16 publications

(6 citation statements)

References 14 publications

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“…Therefore, the measurement precision in the closed‐loop system is around 0.1 ps, which meets with the result obtained in a fiber link. [ 26,27 ]…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the measurement precision in the closed-loop system is around 0.1 ps, which meets with the result obtained in a fiber link. [26,27] To test the stability of the stabilized RoFSO link, a second ATD measurement system with a different optical wavelength is established, which is independent of the closed-loop system. (The details about the out-of-loop measurement are shown in Note S6, Supporting Information).…”

Section: Applications and Discussionmentioning

confidence: 99%

“…Then, the value of N is calculated using a phase unwrapping algorithm. [ 27 ] Finally, the absolute phase delays (unwrapped phases) φ i at different frequencies are obtained. The ATD can be calculated as [ 26 ]

\begin{equation}\tau = \left( {{N_{\rm{M}}} + \frac{{{\theta _{\rm{M}}}}}{{2{{\pi}}}}} \right)\frac{1}{{{f_{\rm{M}}}}}\end{equation}

where f M is the maximum frequency that is used in the measurement, θ M is the wrapped phase measured at f M , and N M can be calculated at f M by the phase unwrapping algorithm.…”

Section: Principle and Experimentsmentioning

confidence: 99%

“…High-precision ATD measurement in fiber links based on the phase-derived ranging has previously been demonstrated. [26,27] Here, we use an optical delay line (General Photonics, DL-002 OEM) to test the precision of our system. The ATD can be changed by the optical delay line, of which the resolution is finer than 1 fs and the accuracy is ±0.01 ps.…”

Section: Atd Measurement Of the Rofso Linkmentioning

confidence: 99%

“…In 2019, we demonstrated optical transfer delay measurement directly over an RoF link based on phase‐derived ranging, [ 26 ] by which the measurement accuracy in a 34 km optical fiber was less than 0.1 ps. [ 27 ] The proposed method achieves high‐precision measurement with a narrowband signal, while barely changing the hardware, which is attractive to be applied in a distributed RF system.…”

Section: Introductionmentioning

confidence: 99%

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Absolute Time Delay Measurement Over an Existing Radio Over Free‐Space Optical Link with Sub‐Picosecond Precision

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Zhang

et al. 2023

Laser & Photonics Reviews

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Distributed RF systems are referred to as the fundamental structure for future wireless communication and sensors. To enable wideband coherent operation, synchronization across the distributed systems with massive parallel absolute time delay (ATD) measurements up to sub‐picosecond precision should be implemented. Traditional ways to achieve precise ATD measurements usually rely on probe signals with broad bandwidth, while that of RF systems is limited. Although an all‐optical solution has high precision, it is complex and not compatible with RF systems. Microwave photonics, which combines the merits of RF and photonics, potentially provides a low‐cost and high‐precision solution that can be deployed in existing RF systems. Here, ATD measurement with sub‐picosecond precision directly over an existing radio over free‐space optical (RoFSO) link, requiring no additional hardware beyond the link, is achieved. The bandwidth of the system is only 10 MHz, while the measurement results meet well with those obtained by optical combs. The measurement errors caused by atmospheric turbulence are well suppressed by a dynamic Kalman filter. The RoFSO links can be stabilized in a closed‐loop measurement. The standard deviation of the timing jitter is 0.28 ps, and the Allan variance is around 1.9 × 10−19 @ 1000 s, which is sufficient to synchronize millimeter‐wave signals.

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“…Therefore, the measurement precision in the closed‐loop system is around 0.1 ps, which meets with the result obtained in a fiber link. [ 26,27 ]…”

Section: Resultsmentioning

confidence: 99%

Section: Applications and Discussionmentioning

confidence: 99%

\begin{equation}\tau = \left( {{N_{\rm{M}}} + \frac{{{\theta _{\rm{M}}}}}{{2{{\pi}}}}} \right)\frac{1}{{{f_{\rm{M}}}}}\end{equation}

where f M is the maximum frequency that is used in the measurement, θ M is the wrapped phase measured at f M , and N M can be calculated at f M by the phase unwrapping algorithm.…”