Martin Slapak

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.

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.

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.

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.

Coexistence of access and backbone networks with sensor systems

In recent years, new applications as distributed fiber-optic sensing or precise time transfer have been widely studied and developed. Especially, with the growing interest for smart cities sensor networks have been developed intensively. Currently, individual optical fibers are mostly used for individual applications which is very inefficient and uneconomical, especially for longer distances. Moreover, construction of new routes for individual applications is often impossible. It is therefore necessary to use either dark fibers or sharing of a single fiber for multiple applications. Whereas the most of current and newly built access networks are based on optical fiber it is possible to find optical fiber almost everywhere - in city centers, along roads, etc. And since a usable bandwidth of a standard single mode optical fiber is sufficiently large it is appropriate to consider the possibility of coexistence. We performed simulations and experimental measurements to analyze requirements of individual applications and to confirm suitability of coexistence of sensor systems and 1.25 Gbps data transmission in a single optical fiber.

Multiagent system in automatic light power balance in optical networks

This article deals with automatic power balancing along an optical line. For optimal transmission of an optical signal it is important to achieve certain parameters such as the signal to noise ratio or chromatic dispersion and also the sufficient output power level of in-line amplifiers. Pump diodes in amplifiers suffer from aging of material and therefore the driving current of pump diodes has to be accordingly increased to achieve the same gain as in the moment when the pump diodes were new. The use of a minimal required driving current leads to the longer lifetime of optical pumps. Therefore an automatic power balance is one of the methods used to achieve these goals.