Pavel Skoda

Photonic services, their enablers and applications

The paper introduces photonic service as a new type of multi-domain, end-to-end network service, that besides traditional data transmission enables also non-data or real-time communication, e.g. the remote control and sharing of different, typically unique, devices. We proved the concept of photonic services on a specialized metrology application - comparison of time scales, where time offset between atomic clock is measured. The experiment has been conducted over distance of 550 km (342 miles).

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.

Simultaneous transmission of accurate time and stable frequency through bidirectional channel over telecommunication infrastructure with excessive spans

In this paper, we present simultaneous transmission of accurate time and stable frequency over 306 km long fiber link. The fiber link belongs to the Time and Frequency infrastructure that is being gradually developed and which shares fiber footprint with data network. The link had been originally deployed with wavelength division multiplexing systems for C and L band systems. But it has been recently upgraded to support 800 GHz wide super-channel with single signal path for both directions. This bidirectional super-channel spans over two extensive segments with attenuation of 28 and 25 dB.

Optical infrastructure for precise time and stable frequency transfer

Time and frequency transfer is new usage of optical links. Recently, it started to deploy as a service of optical networks. Due to principle of time and frequency transfer, it is not possible implement it over data transport layer. The paper describes optical infrastructure for time and frequency transfer in the Czech Republic. The infrastructure is heterogeneous and utilizes resources of the Czech academic optical network. The paper also shows achieved results and indicates necessary steps for further transmission stability improvements.

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.

Simultaneous transmission of accurate time in parallel with stable optical frequency in real fibre network over 612 km

We achieved simultaneous transmission of both stable optical frequency and precise time over real field deployed fiber line. The line was originally deployed by two transmission systems, one operated in C band, second in L band. Within C band system, we created bidirectional 800 GHz wide dark channel and light it up by bidirectional optical amplifiers with single signal path.

Photonic services enables real-time applications over long distances

The paper introduces photonic service as a new type of multi-domain, end-to-end network service, that besides traditional data transmission enables also non-data or real-time communication, e.g. the remote control and sharing of different, typically unique, devices. We proved the concept of photonic services on a specialized metrology application - comparison of time scales, where time offset between atomic clock is measured over distance of 560km.

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.

Time transfer over 1900 km of DWDM network

Since a dedicated optical infrastructure for atomic clock comparison is extremely expensive, we present our tests allowing sharing optical DWDM network. We expanded optical reach of our atomic clock comparison system and demonstrated the transfer of time information over 1900 km of DWDM system with other 8 neighbouring optical channels. NRENs have good potential to host time comparison applications for the academic community over long distances.