Bidirectional optical amplifier for time transfer using bidirectional WDM transmission

Ding, Xuan; Wu, Guiling; Zuo, Faxing; Chen, Jianping

doi:10.1007/s11801-019-9025-1

Cited by 7 publications

(4 citation statements)

References 17 publications

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“…The advantage is that this way the "circulation" of backscattered/reflected signals is eliminated, and higher gains of amplifiers may be set. Similar solutions were presented in [13] and [14], where the isolation for backscattered signal is obtained in different topology. The common drawback of all these solutions is that the amplifier is no longer fully symmetrical.…”

Section: Introductionsupporting

confidence: 56%

Electrical Regeneration for Long-Haul Fiber-Optic Time and Frequency Distribution Systems

Krehlik

Śliwczyński

Buczek

2021

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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In recent years fiber-optic based long-haul installations for time and frequency (T&F) distribution have become operational at various sites. The common practice to cope with large attenuation of long fiber path is to use bidirectional optical amplifiers. This, however, becomes insufficient in case of very long links and/or long spans between amplifiers, because of unavoidable deterioration of the signal-to-noise ratio (SNR). In this paper we present a solution where the optical signal amplification is combined with optical-electrical-optical (OEO) regeneration, performed in a few points along the link. We analyze the impact of replacing some optical amplifiers with OEOs and demonstrate the resulting improvement in terms of SNR of the received optical signal and the phase noise at the output of the T&F distribution system. Laboratory experiments performed with both spooled and metropolitan-area fibers (total length up to 900 km) confirmed the theoretical predictions and showed that placing the OEO regenerators in appropriate points along the link allows reaching the required SNR.

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Section: Introductionsupporting

confidence: 56%

Electrical Regeneration for Long-Haul Fiber-Optic Time and Frequency Distribution Systems

Krehlik

Śliwczyński

Buczek

2021

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…Last but not least, the proximity of the signals made it difficult (expensive) to separate the signals at amplification points. Therefore, there is no simple way to optimize the gains of amplifiers separately for RF&T and OC subsystems or to use quasi-bidirectional amplifiers with optical isolators preventing propagation of backscattered and reflected signals [28]- [30] However, all these issues could be seriously relaxed if a slightly larger bandwidth could be allocated to the metrological signals (such as 200 GHz), so that the signal spacing could be increased to e.g. ±25 GHz.…”

Section: Discussionmentioning

confidence: 99%

Optical Multiplexing of Metrological Time and Frequency Signals in a Single 100-GHz-Grid Optical Channel

Krehlik

Śliwczyński

Buczek

et al. 2021

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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In this paper the concept of co-locating all metrological time and frequency signals in a single optical channel of a standard, 100 GHz-spaced optical grid is presented and evaluated. The solution is intended for situations where only a narrow optical bandwidth is available in a fiber heavily loaded with standard data traffic. We localized the optical reference signals in the middle of the channel, with signals related to RF reference and time tags shifted ±12.5 GHz apart. In the experimental evaluation with a 260 km-long fiber we demonstrate that the stability of frequency signals and the calibration of time tags remained at the very same level of stability and accuracy as for systems utilizing separate channels: the fractional long-term instability for the optical frequency reference was below 5×10 -20 , that for the RF reference at the level of 10 -17 , and the mismatch of the time tag calibration was not more than 10 ps. We also identify possible issues, mainly related to a risk of unwanted Brillouin amplification and scattering.

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“…The round-trip channel has a high degree of consistency, which is conducive to eliminating the asymmetry of the round-trip signal delay. It is one of the time-transfer methods with the highest time synchronization accuracy [8,9]. In 2013, the long-term stability of the optical fiber time synchronization experiment was less than 20 ps in the 540-km fiber link test at the Paris Observatory, France [10].In 2019, Cheng presented an optical fiber time-transfer scheme through the optical supervisory channel (OSC) in WDM systems [11].…”

Section: Introductionmentioning

confidence: 99%

A high-precision bidirectional time-transfer system over a single fiber based on wavelength-division multiplexing and time-division multiplexing

Guo

Liu²,

Kong³

et al. 2023

Front. Phys.

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In this paper, a high-precision bidirectional time-transfer system over a single fiber based on wavelength-division multiplexing and time-division multiplexing (SFWDM-TDM) is proposed, which combines the advantages of wavelength-division multiplexing and time-division multiplexing. It uses two dense wavelength-division channels to effectively suppress the problem of optical fiber reflection. At the same time, the time-division multiplexing method is used in combination with sampling and holding the time to complete the multi-user task. In hardware, we optimized the carrier processing and the high-precision time-delay control module of the SFWDM-TDM system to complete high-precision time-transfer equipment. In software and algorithm, the optical fiber time-interval measurement method and measurement times are optimized, and the SFWDM-TDM system reaches a synchronization accuracy of 8.9 ps at 1 s. Finally, a real-time detection mechanism with self-recovery ability is added to the system. This lays the foundation for a reliable, long-distance, high-precision, and multi-user mode optical fiber time- and frequency-transfer network.

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Bidirectional optical amplifier for time transfer using bidirectional WDM transmission

Cited by 7 publications

References 17 publications

Electrical Regeneration for Long-Haul Fiber-Optic Time and Frequency Distribution Systems

Electrical Regeneration for Long-Haul Fiber-Optic Time and Frequency Distribution Systems

Optical Multiplexing of Metrological Time and Frequency Signals in a Single 100-GHz-Grid Optical Channel

A high-precision bidirectional time-transfer system over a single fiber based on wavelength-division multiplexing and time-division multiplexing

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