Single-ended probing through a multimode fiber having distributed reflectors

Patent metadata

Field	Value
Publication number	US-11035754-B2
Application number	US-201816230115-A
Country	US
Kind code	B2
Filing date	Dec 21, 2018
Priority date	Dec 21, 2018
Publication date	Jun 15, 2021
Grant date	Jun 15, 2021

Abstract

An optical frequency-domain reflectometer (OFDR) capable of estimating the transfer matrix of a multimode optical fiber using mode-selective measurements performed from a single end of the fiber. In an example embodiment, the multimode optical fiber includes distributed reflectors designed to generate relatively strong light reflections along the length of the fiber at a desired spatial resolution. The embodiments may employ a signal-processing algorithm to estimate the fiber's transfer matrix by estimating segment transfer matrices corresponding to the fiber segments located between different ones of the distributed reflectors. Different embodiments of the disclosed OFDR can beneficially be adapted for use in different applications, such as fiber-optic component and module characterization, distributed optical sensing, biomedical imaging, OCT, etc.

First claim

What is claimed is:

1. An apparatus comprising:
a tunable laser configured to generate probe light and controllable to sweep a wavelength of said probe light;
a first spatial mode-selective optical filter to transmit a received part of said probe light primarily to a selectable spatial propagation mode of a multimode optical fiber at a first end thereof;
a second spatial mode-selective optical filter to receive light from the first end of the multimode optical fiber in response to reflection therein and to transmit a portion of said received light, said portion being primarily received from a chosen spatial propagation mode of said multimode optical fiber at the first end;
an optical interferometer connected to mix other part of the probe light with the light transmitted by the second spatial mode-selective optical filter to generate an optical interference signal; and
a digital signal processor connected to receive measurements of said optical interference signal and configured to determine a single-direction transfer matrix of the multimode optical fiber from said measurements.

2. The apparatus of claim 1 , further comprising the multimode optical fiber, the multimode optical fiber having reflectors distributed along at least a portion thereof.

3. The apparatus of claim 2 , wherein the multimode optical fiber has a grating distributed over at least half of the length of the multimode optical fiber.

4. The apparatus of claim 2 , wherein the multimode optical fiber has spatially separated gratings distributed over at least half of the length of the multimode optical fiber.

5. The apparatus of claim 2 , further comprising an optical endoscope and an apparatus for forming images with light received from the optical endoscope, the optical endoscope including the multimode optical fiber.

6. The apparatus of claim 2 , wherein the apparatus is capable of performing optical coherence tomography imaging with light received from the multimode optical fiber.

7. The apparatus of claim 1 , further comprising an electronic controller capable of causing the first and second spatial mode-selective optical filters to change at least one of the selectable spatial propagation mode and the chosen spatial propagation mode.

8. The apparatus of claim 1 , wherein the apparatus is configured to measure said optical interference signal in a manner that is sensitive to polarization state of the light of the chosen spatial propagation mode.

9. The apparatus of claim 8 , wherein the digital signal processor is configured to estimate the single-direction transfer matrix of the multimode optical fiber using estimates of transfer matrices of different segments of the multimode optical fiber.

10. The apparatus of claim 9 , wherein the digital signal processor is further configured to estimate roundtrip transfer matrices for the different segments of the multimode optical fiber, each of the roundtrip transfer matrices being a transfer matrix for light reflected at a corresponding end region of a respective fiber segment.

11. The apparatus of claim 1 , further comprising a mode-selective multiplexer that includes the first spatial mode-selective optical filter.

12. The apparatus of claim 11 , further comprising a mode-selective demultiplexer that includes the second spatial mode-selective optical filter.

13. The apparatus of claim 1 , further comprising a mode-selective demultiplexer that includes the second spatial mode-selective optical filter.

Assignees

• Nokia Technologies Oy

Inventors

• Neilson David
• Winzer Peter
• Fontaine Nicolas
• Chen Haoshuo
• Ryf Roland

Classifications

• G01M11/3172 Primary

  Reflectometers detecting the back-scattered light in the frequency-domain, e.g. OFDR, FMCW, heterodyne detection · CPC title

• G01D5/35306 Primary

  using an interferometer arrangement · CPC title

• G01B9/02091

  Tomographic interferometers, e.g. based on optical coherence · CPC title

• A61B5/0066

  Optical coherence imaging · CPC title

• G01M11/3181

  Reflectometers dealing with polarisation · CPC title