In-field Raman amplification on coherent optical fiber links for frequency metrology.

Area of Science:

• Optical Engineering
• Metrology
• Telecommunications

Background:

• Distributed Raman amplification (DRA) is common for data links but not yet for frequency metrology.
• Frequency metrology demands differ significantly from standard data transmission.

Purpose of the Study:

• Investigate the feasibility and performance of DRA in deployed, in-field optical metrological links.
• Assess DRA's compatibility with wavelength division multiplexing (WDM) and existing amplification methods.

Main Methods:

• Tested DRA on a 94 km metro-network link with multiplexed ITU data channels.
• Evaluated DRA on a 180 km dedicated fiber link, combined with Erbium-doped fiber amplification (EDFA).
• Measured performance impacts on metrological signals and data channels, including coherence properties.

Main Results:

• DRA introduced no noticeable penalties for metrological signals or ITU data channels.
• Raman amplification proved compatible with WDM architectures.
• DRA can be used alongside or as an alternative to bidirectional EDFAs.
• No deterioration in signal coherence was observed, maintaining frequency instability at the 10⁻¹⁹ level.

Conclusions:

• Distributed Raman amplification is a viable and effective technique for enhancing optical metrological links.
• DRA can be integrated into existing WDM systems without compromising signal integrity or metrological performance.
• This research supports the deployment of continental fiber networks for advanced frequency metrology.