Fiber-optic time and frequency distribution system OSTT-3

OSTT-3 Local Module

OSTT-3 Remote Module

Introduction and key features

OSTT-3 has been developed by Polish AGH University of Science and Technology.

The local module of the system accepts the frequency and time signals (10MHz and 1PPS) and transmits them via an optical fiber to the remote module. In contrary to standard two-way systems, our solution delivers stabilized and calibrated replica of source signals, thus may be described as a virtual atomic clock at the end of the fiber. OSTT-3 may be used for clock comparisons, and is a great way for a perfect time and frequency distribution to the users not maintaining their own clocks.

Clients are the best reference. Please see a list of some noted users below:

  • National Institute of Standards and Technology (NIST) - Boulder, USA,
  • The United States Naval Observatory (USNO) - Washington, USA,
  • Physikalisch-TechnischeBundesanstalt (PTB) - Germany,
  • The National Physical Laboratory (NPL) - United Kingdom,
  • Deutsche Telekom - Germany.

Active delay stabilization

The unique features of the system are based on the concept of active compensation of variations of the fiber delay. The signal reaching the remote module is redirected backward to the local module and used for compensation of path delay fluctuations.


Calibration of the time transfer is based on round-trip delay measurement, which is performed locally at the transmitting side of the system. After installation and initial calibration, the input-to-output delay is constant and there is no need for any further measurements or data exchange.


OSTT-3 consists of a local and remote module for time and frequency transfer,

Transfers 10 MHz signals (100MHz as an option), ADEV below 3x10-13 for 1 s averaging, below 3´10-17 for 105 s averaging s averaging,

Transfers 1PPS signal (also 100PPS), phase synchronous with frequency signal, TDEV below 3 ps for 10s averaging, below 1 ps for 105s averaging s averaging,

Operates bi-directionally on a single optical fiber in C band, maximum optical loss 25 dB,

OSTT-3 is actively stabilized against fiber induced phase fluctuations; the phase correction range is 2000 ns,

As an option the system can be enriched with optical amplifiers OBA-2.

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