Performance of Rayleigh-based phase-OTDR with correlation-based diversity combining and bias removal

Patent metadata

Field	Value
Publication number	US-11378443-B2
Application number	US-202016879407-A
Country	US
Kind code	B2
Filing date	May 20, 2020
Priority date	May 22, 2019
Publication date	Jul 5, 2022
Grant date	Jul 5, 2022

Abstract

Aspects of the present disclosure describe systems, methods and apparatus for improving the performance of Rayleigh-based phase-OTDR with correlation-based diversity combining and bias removal.

First claim

The invention claimed is:

1. A distributed acoustic sensing (DAS) system using phase optical time-domain reflectometry based on Rayleigh scattering comprising:
an optical interrogator unit that generates optical pulses at one or more optical frequencies and introduces them into an optical fiber under test;
a receiver unit that detects Rayleigh backscatter from the optical fiber under test, and
a data processor unit that determines acoustic vibrations experienced by the optical fiber under test by computing a plurality of delay interferometric products based on different combinations of polarizations and/or frequencies of the detected Rayleigh backscatter, adding the interferometric products in phase by aligning their vectors using correlation, followed by bias removal wherein phase rotations φ l,k are determined by first choosing an appropriate window size of M samples and then determining a b k [l, m] term according to the following relationship:

k
0

=

max
k

⁢

(

∑

m
=
1

M

⁢



b
k

⁡

[

l
,
m

]



2

)

;

; and

subsequently determining the phase rotations by correlating remaining terms according to b k [l, m] according to the following:

φ

l
,
k

=

angle
⁢

⁢

(

∑

m
=
1

M

⁢

b
k

⁡

[

l
,
m

]

⁢

b

k
0

*

⁡

[

l
,
m

]

)

where b k [l, m] are delay interferometric products, l is a position index and m is a time index.

2. The system of claim 1 wherein the receiver unit detects the Rayleigh backscatter at each optical frequency of the one or more optical frequencies using a plurality of coherent receivers.

3. The system of claim 1 wherein the receiver unit detects the Rayleigh backscatter at each optical frequency of the one or more optical frequencies using a plurality of optical delay interferometers.

4. The system of claim 1 wherein the optical pulses are introduced into the optical fiber under test at regular intervals (pulse repetition rate) and the Rayleigh impulse response is sampled at the pulse repetition rate.

Assignees

• Nec Lab America Inc
• Nec Corp

Inventors

• Ip Ezra
• Huang Yue-Kai

Classifications

• H04B10/071

  using a reflected signal, e.g. using optical time domain reflectometers [OTDR] · CPC title

• G01D5/35361

  using elastic backscattering to detect the measured quantity, e.g. using Rayleigh backscattering · CPC title

• G01H9/004 Primary

  using fibre optic sensors (light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125) · CPC title

• G01B9/0209

  Low-coherence interferometers · CPC title