Radek Velc

Precise time transfer on the IPE - VUGKT line - a detailed analysis

We present implementation of a pilot bidirectional line IPE-VUGKT for precise time transmission. Directional non-reciprocities are evaluated together with uncertainties. Emphasis is given to the evaluation of the Sagnac effect. Our approach improves significantly the uncertainty.

Simultaneous transmission of standard data, precise time, stable frequency and sensing signals and their possible interaction

Since optical fibre is a standard medium for all current and new networks, these optical networks offer possibility for connecting new applications over long distances almost to anywhere. However with increasing number of applications, the large number of dedicated fibres will be necessary. This constitution is quite unpractical in terms of costs, however since wavelength division multiplexing enables transmission of multiple different signals over one fibre it is more than suitable to use this technology for cost reduction and network efficiency increase. Wavelength division multiplexing technology is common in data networks where parameters of all signals may be optimized (especially maximum optical power launched into the fibre) for simultaneous transmission. In case of non-data applications the situation is more difficult because each application is connected by different type of signal and with its own requirements for transmission parameters. Hence it is necessary to evaluate possible interactions before field deployment. In this paper we deal with possible interaction of a coherent 100 Gb/s dual polarisation QPSK data signal with new applications like accurate time and stable frequency transmission and high-power pulse signal used for distributed sensing. In laboratory setup we performed a measurement with a standard G.652D single mode optical fibre and also with G.655 fibre which can also be found in some networks and may be source of more nonlinear interactions. All signals were transmitted in a grid with 100GHz spacing according to ITU standard. Results confirmed our assumptions that 100GHz spacing is not large enough and also that G.655 optical fibre is prone to more non-linear interactions.

Interference of Data Transmission in Access and Backbone Networks by High-Power Sensor System

ABSTRACT Currently, individual optical fibers are mostly used for each non-data application, which is very inefficient and uneconomical. Sharing a single fiber for multiple applications is a promising solution. However, in the case of a non-data application, the situation is much more complicated compared to data because of special application´s requirements. In laboratory setup, we performed a measurement with a standard G.652D optical fiber for analyzing possible interaction of stable frequency/accurate time transmission, 1.25/10Gbps data transmission (typical bitrates for access point-to-point networks), and high-power sensor signal for different channel spacing and different pulse duration of sensor signal.

Joint stable optical frequency and precise time transfer over 406 km of shared fiber lines — Study

We present a preliminary study of bidirectional ultra-stable optical frequency and precise time transmission over 406 km long path in the telecom-grade fiber optic infrastructure of dense wavelength division multiplexing. The main challenge in this application is the need of bidirectional amplification to compensate for signal loss. Directional non-reciprocities of the time transfer are evaluated together with their uncertainties. Solutions are proposed to significantly limit the final uncertainty.

Multi-purpose infrastructure for dissemination of precise stable optical frequency

Long distance precise frequency and accurate time transfer methods based on optical fiber links have evolved rapidly in recent years, demonstrating excellent performance. They are attractive both for very high-performance applications and as a secure alternative complement to radio- and satellite-based methods. In this paper, we present development of infrastructure for such transmission containing 700+km of transmission lines, with planned cross border optical frequency connectivity. According to our knowledge, this will be the third such line globally. The infrastructure also shares fibers with existing data transmissions, both amplitude and phase modulated, which poses high demands on mutual isolation and insensitivity to cross talks.

CLONETS - clock network services: Strategy and innovation for clock services over optical-fibre networks

Methods for long-distance time and frequency transfer over optical fibers have demonstrated excellent performances and are evolving rapidly. CLONETS is a European Union-funded coordination and support action intended to facilitate the vision of a sustainable, pan-European optical fiber network for precise time and frequency reference dissemination.

Optical stabilization for time transfer infrastructure

In this paper, we propose and present verification of all-optical methods for stabilization of the end-to-end delay of an optical fiber link. These methods are verified for deployment within infrastructure for accurate time and stable frequency distribution, based on sharing of fibers with research and educational network carrying live data traffic. Methods range from path length control, through temperature conditioning method to transmit wavelength control. Attention is given to achieve continuous control for relatively broad range of delays. We summarize design rules for delay stabilization based on the character and the total delay jitter.

Comparison of interferometry based and polarization based sensing systems for use in fiber infrastructure protection

Almost all data transmissions over long distances are transmitted through optical fibers. Fiber infrastructure is therefore very important and is necessary to protect it against fiber cuts caused e.g. by digging activity. Many network operators seeking appropriate solution for self protecting infrastructure system. We performed comparative measurement of the polarization based sensing system and the interferometry based sensing system to determine the sensitivity and accuracy of both systems. The results confirmed theoretical assumptions that both systems are suitable for strain measurement and the interferometry based sensing systems are more sensitive.

Pre-Commercial Procurement in Optical Networking domain

Public procurements are essential legislative procedures to ensure acquiring best possible costs, to meet the needs of the procurer in terms of quality and quantity, time, and location. In this paper, we provide you with the information about Pre-Commercial Procurement (PCP) procedures being beneficially experienced in a specific area of Optical Networking in public sector, especially National Research and Education Networks (NRENs). To optimize the usage of public funds for building beyond state-of-the-art public networks, this is the main goal of the project: Communication Platform for Tenders of Novels Transport Networks (COMPLETE).

Joint accurate time and stable frequency distribution infrastructure sharing fiber footprint with research network

In this paper, we present infrastructure for accurate time and stable frequency distribution. It is based on sharing of fibers of research and educational network carrying data traffic. Accurate time and stable frequency transmission uses mainly created dark channels amplified by special bidirectional amplifiers with the same propagation path for both directions. Paper also targets challenges joined with bidirectional transmission, which represents directional non-reciprocities and interaction with parallel data transmissions.