[Paper Review] Advanced Distributed Submarine Cable Monitoring and Environmental Sensing using Constant Power Probe Signals and Coherent Detection

Mikael Mazur, Nicolas K. Fontaine+7 more|arXiv (Cornell University)|Mar 12, 2023

Integrated Circuits and Semiconductor Failure Analysis9 citations

TL;DR

The paper demonstrates an FPGA-based coherent optical frequency domain reflectometry setup for submarine cable monitoring, achieving high SNR with constant-power probes and coherent processing over a trans-oceanic cable. It compares coherent monitoring to power-only methods and shows continuous phase/polarization sensing across ~80 repeaters with 1 s averaging.

ABSTRACT

In this work we demonstrate an FPGA-based coherent optical frequency domain reflectometry setup for cable monitoring. Using coherent detection for averaging and narrowband filtering, we significantly improve the signal-to-noise ratio (SNR) compared to traditional intensity-only techniques while also enabling continuous monitoring of phase and polarization. In addition, the probe signal has constant power, avoiding the nonlinear distortions and thereby enabling continuous use without interfering with data channels. We perform a field demonstration over a trans-oceanic cable using loopback configurations present in each repeater, demonstrating measurement SNR exceeding 30 dB for all about 80 repeaters with an averaging window of 1 second. We furthermore compare cable monitoring using coherent processing to today's solutions using power-only measurements. Our results show how transitioning to coherent technology for cable monitoring can improve sensitivity and enable new types of monitoring, exploring knowledge gained from transitioning from incoherent to coherent data transmission.

Motivation & Objective

• Demonstrate FPGA-based coherent optical frequency domain reflectometry (C-OFDR) for distributed submarine cable monitoring.
• Show benefits of coherent detection for averaging, filtering, and continuous phase/polarization monitoring.
• Validate constant-power probe signals to avoid nonlinear distortions and interference with data channels.
• Provide field demonstration over a trans-oceanic cable using repeater loopbacks.
• Compare coherent processing to traditional power-only monitoring methods.

Proposed method

• Use FPGA-based coherent optical frequency domain reflectometry setup.
• Apply averaging and narrowband filtering enabled by coherent detection to boost SNR.
• Employ constant-power probe signals to prevent nonlinear distortions and interference with data channels.
• Conduct field demonstration over a trans-oceanic cable leveraging loopback configurations in repeaters.
• Measure measurement SNR exceeding 30 dB across ~80 repeaters with 1 s averaging window.
• Contrast coherent monitoring results with power-only monitoring approaches.

Experimental results

Research questions

• RQ1 Can coherent OFDR provide higher sensitivity and continuous phase/polarization monitoring for submarine cables compared to traditional intensity-only methods?
• RQ2 What SNR and monitoring fidelity can be achieved across a long trans-oceanic link using constant-power probes and 1-second averaging?
• RQ3 How does coherent processing enable new types of environmental and cable-health sensing in distributed submarine cables?

Key findings

• Coherent detection with averaging and narrowband filtering yields higher SNR than intensity-only techniques.
• Constant-power probe signals avoid nonlinear distortions and do not interfere with data channels.
• Field demonstration over a trans-oceanic cable shows SNR > 30 dB for about 80 repeaters with 1 s averaging.
• Coherent processing enables continuous monitoring of phase and polarization along the cable.
• Results indicate potential advantages of transitioning from incoherent to coherent monitoring for submarine cables.