Dual-Wavelength Cancellation of Dispersion-Induced Phase Noise in Opto-Terahertz Fiber Links

TL;DR

This paper demonstrates a method to distribute stable opto-THz signals over 38 km of fiber by canceling dispersion-induced phase noise using a dual-wavelength approach, achieving sub-femtosecond stability.

Contribution

It introduces a dual-wavelength Brillouin laser with a round-trip noise-cancellation scheme to mitigate dispersion effects in long-distance opto-THz transmission.

Findings

Achieved sub-femtosecond timing stability for 150, 300, and 600 GHz signals.

Demonstrated fractional frequency instability below 1e-17 at 10,000 seconds.

Successfully compensated dispersion-mediated phase fluctuations over 38 km of fiber.

Abstract

Stable dissemination of terahertz (THz) signals over long distances is important for next-generation synchronization networks, radio astronomy, and high-capacity wireless systems. Optical fiber provides a low-loss platform for coherent frequency transfer; however, when a THz carrier is encoded as the difference between two optical wavelengths, chromatic dispersion introduces differential phase noise that degrades spectral purity. Here, we demonstrate phase-coherent distribution of opto-THz carriers over 38 km of standard single-mode fiber using a dual-wavelength Brillouin laser (DWBL) combined with a dual-channel round-trip noise-cancellation architecture. By extracting the differential phase noise between the two optical lines via a dual-channel round-trip measurement, dispersion-mediated phase fluctuations are compensated, and the intrinsic stability of the source is effectively preserved at the remote end within the measurement sensitivity. Opto-THz carriers at 150, 300, and 600 GHz exhibit sub-femtosecond timing stability and fractional frequency instabilities below 1e-17 at 10,000 seconds of averaging.