Polarization sensing using submarine optical cables

Abstract

Observation of polarization modulation at the output of a submarine link, extracted from a standard coherent telecom receiver, can be used to monitor geophysical events such as sea waves and earthquakes occurring along the cable. We analyze the effect of birefringence perturbations on the polarization at the output of a long-haul submarine transmission system, and provide analytical expressions instrumental to understanding the dependence of the observed polarization modulation on the amplitude and spatial extension of the observed events. By symmetry considerations, we show that in standard single mode fibers with random polarization coupling, if polarization fluctuations are caused by strain or pressure, the relative birefringence fluctuations are equal to the relative fluctuations of the polarization averaged phase. We finally show that pressure induced strain is a plausible explanation of the origin of polarization modulations observed in a long submarine link. The presented analysis paves the way for the transformation of transoceanic fiber optic links during operation into powerful sensing tools for otherwise inaccessible geophysical events occurring in the deep ocean.

Surface Gravity Wave Interferometry and Ocean Current Monitoring With Ocean‐Bottom DAS

“…In this case, a local change in pressure exerts an isotropic radial stress on the 10.1029/2021JC018375 cable, resulting in longitudinal strain according to the Poisson's ratio of the cable itself. Mecozzi et al (2021) considered the effect of direct pressure loading to account for ocean swell observations on Google's transoceanic Curie cable and estimated a sensitivity of 𝐴𝐴 𝜀𝜀 Δ𝑝𝑝 ≈ 3 × 10 −9 Pa −1 . The result of Mecozzi et al ( 2021) is also consistent with the transfer function between OBDAS and a collocated pressure gauge reported by Matsumotu et al (2021) for high-frequency hydroacoustic waves.…”

“…Mecozzi et al. (2021) considered the effect of direct pressure loading to account for ocean swell observations on Google's transoceanic Curie cable and estimated a sensitivity of $$\frac{\varepsilon }{{\Delta}p}\approx 3\times 1{0}^{-9}$$ Pa −1 . The result of Mecozzi et al.…”

Polarization multiplexed diffractive computing: all-optical implementation of a group of linear transformations through a polarization-encoded diffractive network

“…As another important physical property of light, polarization specifies the geometrical orientation of electromagnetic wave oscillations. Utilizing the polarization state of light has played a pivotal role in numerous applications, including telecommunications 53 – 55 , imaging 56 – 61 , sensing 62 – 64 , computing 65 , and displays 66 , 67 . For example, polarization-division multiplexing (PDM) has been used in telecommunication systems to permit two channels of information to be simultaneously transmitted using orthogonal polarization states over a single wavelength 54 , 68 .…”

Transoceanic Phase and Polarization Fiber Sensing using Real-Time Coherent Transceiver

“…Frequency dependence is also neglected. A Jones matrix therefore contains more "sensing" information than a single Stokes vector [7] . To remove the ≤2 dB PDL from the measured Jones matrix, Eq.…”