ELSTAB—Fiber-Optic Time and Frequency Distribution Technology: A General Characterization and Fundamental Limits

Krehlik, P.; Śliwczyński, Ł.; Buczek, Ł.; Kołodziej, Joanna; Lipiński, Marek

doi:10.1109/tuffc.2015.2502547

Cited by 67 publications

(47 citation statements)

References 34 publications

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“…Each individual link is equipped with the ELSTAB fiber optic time (1 PPS) and frequency (10 MHz) transfer system with active fiber delay stabilization [22][23], and a number of single-path bi-directional optical amplifiers (SPBA) used to compensate for the fiber losses [24]. ELSTAB technology uses an intensitymodulated light that conveys T/F signals between the local and remote modules in both directions over the same optical fiber.…”

Section: Description Of Ott Infrastructureand Equipment Involvedmentioning

confidence: 99%

“…Thanks to the symmetry of the propagation conditions and exploiting a feedback loop, the delay of both transmitted 1 PPS and 10 MHz signals can be stabilized at the output of the remote module. The specially designed matched electronic delay lines, manufactured as an application specific integrated circuit (ASIC), work as an active stabilization element with the range of delay change adequate for links up to about 100 km long [22]. In combination with additional optically switched delay banks this distance can be extended up to 1000 km [23].…”

Section: Description Of Ott Infrastructureand Equipment Involvedmentioning

confidence: 99%

“…3. Yet another reason justifying the use the correction factor Γ is the fact that the laser pulses (which are used by ELSTAB to convey T/F information [22]) traveling along a dispersive fiber undergo distortions that depend on the characteristics of the laser, especially on its wavelength chirping. We observed that this could introduce some small asymmetry between the forward and backward directions because laser parameters are usually slightly different.…”

Section: Determining λ τ ∆mentioning

confidence: 99%

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Calibrated optical time transfer of UTC(k) for supervision of telecom networks

et al. 2018

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We report on the evaluation of the performance of optical time transfer links connecting a facility of Deutsche Telekom in Bremen with the Physikalisch-Technische Bundesanstalt in Braunschweig. In the current configuration three links have been established, two via a hub in Hannover and one using an independent alternate route. They are equipped with electronically stabilized fiber optic time and frequency transfer systems and parallel operation is maintained since December 2016. A novel method of link calibration, composed of two steps (one performed in the laboratory and the second one in the field), to accurately determine the influence of fiber chromatic dispersion is discussed in detail, and a thorough analysis of the uncertainty budget is given. We show that the time transfer performance achieved is difficult to characterize based on measurements with time interval counters that are the standard equipment in timing laboratories and in the telecommunications sector. In our experiments, values of TDEV at the low ps-level at averaging times between 10 4 to 10 6 seconds have been achieved. The uncertainty of time transfer (including all kinds of delays) is of the order of 50 ps in a cascade of links. The results obtained show that such a kind of link is capable to deliver signals to a remote end with an instability being at least two orders of magnitude below the current requirements included in relevant Recommendations of the International Telecommunication Union-Telecommunication Sector (ITU-T). Moreover, the current implementation would allow primary Cs fountain clocks to be compared at the level of their performance, that is characterized by an uncertainty at the low 10-16 level and a frequency instability of the same order of magnitude at one day averaging.

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Section: Description Of Ott Infrastructureand Equipment Involvedmentioning

confidence: 99%

Section: Description Of Ott Infrastructureand Equipment Involvedmentioning

confidence: 99%

Section: Determining λ τ ∆mentioning

confidence: 99%

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Calibrated optical time transfer of UTC(k) for supervision of telecom networks

et al. 2018

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“…Each time transfer link is composed of two terminals that exchange an optical carrier modulated with one pulse per second (PPS) signals (in practice they are often associated with a radio frequency carrier). The link can be organized either in a two-way configuration (in analogy to TWSTFT) [4], or as a feedback system, [7], [8], which can stabilize the delay or the phase of the signal delivered to the remote end of such a link. Hybrid systems, intended to transfer RF, PPS and optical carrier [22]- [24], have also been investigated.…”

Section: Introductionmentioning

confidence: 99%

“…This requires measurement of various delays associated with either the terminals or the optical fiber used to connect them [4]- [9]. This procedure is especially convenient in fiber optic links with stabilized propagation delay, where it can be performed from one side of the link only [5], [7], [13].…”

Section: Introductionmentioning

confidence: 99%

Picoseconds-Accurate Fiber-Optic Time Transfer With Relative Stabilization of Lasers Wavelengths

Śliwczyński

Krehlik

Buczek

et al. 2020

J. Lightwave Technol.

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In this paper we focus on analyzing the accuracy of time transfer in bidirectional fiber optic links. It has been pointed out that one of the main uncertainty contributions in such links is related to insufficient stabilization of the lasers' wavelengths and to the asymmetry of propagation caused by the fiber's chromatic dispersion. To reduce these contributions, we propose a scheme where the difference (offset) of the wavelengths of forward and backward lasers is stabilized and where optical interleavers are used as diplexers. This allows implementing a λ-swapping technique to assess dispersion-related link asymmetry during the link calibration. For the investigation of these approaches and the measurement of the associated stability we utilize a frequency-synchronized offset laser module (FSOLM) to realize an offset of 25 GHz. In this paper, we show that with the proposed λ-swapping technique the uncertainty associated with the propagation asymmetry due to fiber chromatic dispersion can be reduced to values below 2.5 ps for links up to 1000 km long, making it insignificant compared to other uncertainty contributions. A laboratory proof-of-concept experiment, in which distances up to 540 km were tested, showed good agreement between the measured and the anticipated propagation delay of investigated links.

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Time and phase alignment of distributed gateways: Theoretical analysis and experimental demonstration

Mollaymeri,

Delamotte,

Knopp

2023

Satell Commun Network

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SummaryVery high throughput satellite systems have recently been developed to offer high‐speed connectivity, especially in remote areas, planes, and ships. The high data rates can be achieved by using a multibeam approach with an aggressive reuse of the available frequency resources. Due to the high number of user beams, the system must support a large aggregated bandwidth. Multiple‐gateway architectures are a necessary solution to sustain the immense bandwidth requirements. Multiple‐input multiple‐output (MIMO) feeder links have been proposed to address the ground segment design challenges of multiple‐gateway architectures. The deployment costs and the link availability performance can in particular benefit from this approach. However, to coordinate the operation of multiple gateways, high precision time and phase synchronization is necessary. In this paper, the effect of time and phase misalignment in MIMO feeder links is studied. The performance limitation due to imperfect time and phase distribution is analyzed. Synchronization via optical fiber is considered in this study. The accuracy of time distribution was verified through laboratory measurements. The impact of the residual timing error on the achievable system bandwidth was assessed. Results showed that several GHz of bandwidth can be supported. On the other hand, a recently proposed phase synchronization approach is considered as a promising candidate for MIMO feeder links. Its phase stability performance is assessed, and it is emphasized that requirements in terms of link outage are fulfilled.

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ELSTAB—Fiber-Optic Time and Frequency Distribution Technology: A General Characterization and Fundamental Limits

Cited by 67 publications

References 34 publications

Calibrated optical time transfer of UTC(k) for supervision of telecom networks

Calibrated optical time transfer of UTC(k) for supervision of telecom networks

Picoseconds-Accurate Fiber-Optic Time Transfer With Relative Stabilization of Lasers Wavelengths

Time and phase alignment of distributed gateways: Theoretical analysis and experimental demonstration

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