Method for determining distributed birefringence variations in a polarization-maintaining optical fiber
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Publication Number
US-12529623-B2
Publication Date
2026-01-20
Expiration Date
Abstract
System and method for determining distributed birefringence variations in a polarization-maintaining optical fiber (PM fiber). The method includes causing a pump signal to be sent into the PM fiber to generate a Brillouin dynamic grating (BDG) therein, causing a first chirped probe optical pulse to be sent into the PM fiber, receiving a first reflected signal, the first reflected signal being a first portion of the first chirped probe optical pulse reflected by the BDG, receiving a second reflected signal, the second reflected signal being a second portion of the first chirped probe optical pulse reflected by the BDG, and determining a variation of birefringence of the PM fiber indicative of a variation of physical disturbance of the PM fiber between times of reflections on the BDG of the first and second reflected signals.
Core Innovation
The disclosed invention relates to determining distributed birefringence variations in a polarization-maintaining optical fiber by generating a Brillouin dynamic grating and interrogating the Brillouin dynamic grating with orthogonally polarized chirped probe optical pulses. A pump signal is caused to be sent into the polarization-maintaining optical fiber at a first moment in time along a first polarization direction at an interaction region, and the pump signal is polarized in the first polarization direction to generate the Brillouin dynamic grating in the polarization-maintaining optical fiber along the first polarization direction.
A first chirped probe optical pulse is caused to be sent into the polarization-maintaining optical fiber at a second moment in time subsequent to the first moment in time, where the probe is polarized in a second polarization direction orthogonal to the first direction. Reflected signals are received at different time moments, including a first reflected signal at a third moment in time and a second reflected signal at a fourth moment in time, where each reflected signal is a portion of the chirped probe optical pulse reflected by the Brillouin dynamic grating at the interaction region.
The birefringence variation of the polarization-maintaining optical fiber at the interaction section is determined based on the second, third and fourth moments in time, and the determined variation is indicative of a variation of physical disturbance of the polarization-maintaining optical fiber between times of reflections on the Brillouin dynamic grating of the first and second reflected signals. This enables distributed determination of birefringence variation associated with physical disturbance in the polarization-maintaining optical fiber using polarization-aligned pump generation of the Brillouin dynamic grating and orthogonally polarized chirped probe interrogation.
Claims Coverage
The patent includes two independent claims: a method executed by a computer-implemented system and a system configured to perform the same Brillouin dynamic grating-based interrogation. The independent claims share the same core inventive concept: polarization-aligned Brillouin dynamic grating generation using a pump, orthogonally polarized chirped probe interrogation, and determining distributed birefringence variation from reflection time moments indicative of physical disturbance.
Polarization-aligned BDG generation in PM fiber
Causing a pump signal to be sent into the polarization-maintaining optical fiber at a first moment in time to generate a Brillouin dynamic grating in the polarization-maintaining optical fiber along a first polarization direction at an interaction region of the polarization-maintaining optical fiber, the pump signal being polarized in the first polarization direction.
Orthogonally polarized chirped probe interrogation
Causing a first chirped probe optical pulse to be sent into the polarization-maintaining optical fiber at a second moment in time subsequent to the first moment in time, the first chirped probe signal being polarized in the second polarization direction, the second polarization direction being orthogonal to the first direction.
Time-moment based reception of reflected portions
Receiving a first reflected signal at a third moment in time, the first reflected signal being a first portion of the first chirped probe optical pulse reflected by the Brillouin dynamic grating; and receiving a second reflected signal at a fourth moment in time, the second reflected signal being a second portion of the first chirped probe optical pulse reflected by the Brillouin dynamic grating at the interaction region of the polarization-maintaining optical fiber.
Distributed birefringence variation indicative of physical disturbance
Determining a variation of birefringence of the polarization-maintaining optical fiber at the interaction section based on the second, third and fourth moments in time, the variation of birefringence being indicative of a variation of physical disturbance of the polarization-maintaining optical fiber between times of reflections on the Brillouin dynamic grating of the first and second reflected signals.
Across the independent claims, the inventive combination is: generating a Brillouin dynamic grating in a polarization-maintaining optical fiber using a pump polarized along a first polarization direction, interrogating the Brillouin dynamic grating with a chirped probe polarized along an orthogonal polarization direction, receiving reflected portions at different time moments, and determining a distributed birefringence variation indicative of physical disturbance based on those time moments.
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