Highly stable multiple-access underwater frequency transfer with terminal phase compensation.

Area of Science:

• Underwater communication systems
• Precision frequency dissemination
• Metrology and timekeeping

Background:

• Accurate frequency transfer is crucial for various scientific and technological applications, including global navigation satellite systems and fundamental physics experiments.
• Underwater environments pose significant challenges for signal transmission due to signal attenuation and multipath propagation.
• Existing frequency transfer methods often struggle with stability and accuracy in submerged conditions.

Purpose of the Study:

• To demonstrate a novel multiple-access underwater frequency transfer scheme.
• To evaluate the performance of the proposed scheme using terminal phase compensation.
• To assess the feasibility of disseminating highly stable frequency signals to multiple underwater terminals.

Main Methods:

• Development and implementation of a multiple-access frequency transfer scheme.
• Utilization of terminal phase compensation to mitigate underwater signal distortions.
• Experimental dissemination of a 100 MHz frequency signal over a 3-meter underwater link for 5000 seconds.
• Measurement and analysis of timing fluctuation and fractional frequency instability.

Main Results:

• Successful dissemination of a highly stable 100 MHz frequency signal over the underwater link.
• Achieved a total root-mean-square (RMS) timing fluctuation of approximately 3 picoseconds (ps).
• Measured fractional frequency instabilities of 5.9×10^-13 at 1 second and 5.3×10^-15 at 1000 seconds.

Conclusions:

• The demonstrated multiple-access underwater frequency transfer scheme with terminal phase compensation is effective.
• The technique provides high stability and low timing fluctuation, suitable for demanding applications.
• The proposed method shows significant potential for distributing atomic clock signals to multiple underwater terminals.