Michelson interferometer based phase demodulation for stable time transfer over 1556 km fiber links.

Area of Science:

• Optical Physics
• Metrology
• Telecommunications

Background:

• Time transfer is crucial for modern networks.
• Phase modulation schemes offer precise time signal transmission.
• Existing methods face challenges in stability and distance.

Purpose of the Study:

• To propose and demonstrate an adjustable and stable Michelson interferometer for two-way time transfer.
• To implement a DC phase tracking algorithm for enhanced accuracy.
• To assess the system's performance over long-distance fiber links.

Main Methods:

• Utilizing a Michelson interferometer (MI) for demodulating time signals modulated onto an optical carrier.
• Employing a DC phase tracking algorithm to compensate for phase noise.
• Implementing a compact, cost-effective, and symmetrical demodulator design.
• Modulating a one pulse per second (1 PPS) time signal onto an optical carrier.

Main Results:

• Achieved a stability of 2.31 × 10^-11 at 1000 s averaging time for the demodulator.
• Demonstrated two-way time transfer over 1556 km of lab fibers.
• Obtained a time interval stability of 5.62 × 10^-11 for 1 PPS signals at 1000 s averaging time.

Conclusions:

• The proposed Michelson interferometer with DC phase tracking is a stable and effective solution for time transfer.
• The system demonstrates potential for reliable long-distance time signal transmission over fiber optic links.
• This technology can enhance synchronization accuracy in various applications.