Mode-Walk-off Interferometry for Position-Resolved Optical Fiber Sensing

Abstract

Simultaneously sensing and resolving the position of measurands along an optical fiber enables numerous opportunities, especially for application in environments where massive sensor deployment is not feasible. Despite significant progress in techniques based on round-trip time-of-flight measurements, the need for bidirectional propagation imposes fundamental barriers to their deployment in fiber communication links containing non-reciprocal elements. In this work, we break this barrier by introducing a position-resolved sensing technique based on the interference of two weaklycoupled non-degenerate modes of an optical fiber, as they walk-off through each other. We use this mode-walk-off interferometry to experimentally measure and localize physical changes to the fiber under test (axial strain and temperature) without the typical requirement of round-trip time-offlight measurements. The unidirectional propagation requirement of this method makes it compatible with fiber links incorporating non-reciprocal elements, uncovering a path for multiple sensing applications, including ultra-long range distributed sensing in amplified space-division-multiplexed telecommunication links.

Localization of seismic waves with submarine fiber optics using polarization-only measurements

“…Long-haul transoceanic cables, however, introduce unique challenges that cannot be tackled using the prevailing techniques applied for in-land cables (i.e., distributed optical fiber sensing 5 , 9 ). These methods often rely on weakly backscattered light, which restricts their application to the first ~100 km of cable, makes them incompatible with optical repeaters 10 , and elicits the use of high optical peak powers (leading to optical nonlinearities which compromise coexisting data channels in the same fiber strand 11 ). These limitations are often inconsequential for in-land or near-shore deployments, as the total cable lengths are shorter and the abundance of unused fiber strands facilitates the use of dedicated sensing fibers, but constitute critical roadblocks for transoceanic deployments.…”

Localization of Seismic Waves in Submarine Fiber Optics Using Polarization-only Measurements

“…Long-haul transoceanic cables, however, introduce unique challenges that cannot be tackled using the prevailing techniques applied for in-land cables (i.e., distributed optical fiber sensing 5,9 ). These methods often rely on weakly backscattered light, which restricts their application to the first ∼ 100 km of cable, makes them incompatible with optical repeaters 10 , and elicits the use of high optical peak powers (leading to optical nonlinearities which compromise coexisting data channels in the same fiber strand 11 ). These limitations are often inconsequential for in-land or near-shore deployments, as the total cable lengths are shorter and the abundance of unused fiber strands facilitates the use of dedicated sensing fibers, but constitute critical roadblocks for transoceanic deployments.…”