US-12625318-B2 - Optical fibre assemblies and methods of use

US12625318B2US 12625318 B2US12625318 B2US 12625318B2US-12625318-B2

Abstract

An optical fibre assembly comprises a hollow core optical waveguide comprising a hollow core surrounded by a structured arrangement of longitudinally extending capillaries providing an inner cladding surrounded by an outer cladding; a diagnostic solid core optical waveguide comprising a solid core surrounded by a cladding, and extending substantially parallel to the hollow core optical waveguide; and a jacket surrounding both the hollow core optical waveguide and the solid core optical waveguide and forming a common mechanical environment for the hollow core optical waveguide and the solid core optical waveguide. The optical fibre assembly may be or may comprise or be included in an optical fibre cable, and may be used in a method for testing hollow core optical waveguides.

Inventors

Andrew Thomas Harker
Andrew Paul Appleyard
Raymond John HORLEY
Ian Dewi Lang

Assignees

MICROSOFT TECHNOLOGY LICENSING, LLC

Dates

Publication Date: 20260512
Application Date: 20231025
Priority Date: 20181003

Claims (20)

1 . A method of testing a hollow core optical waveguide, the method comprising: providing the hollow core optical waveguide in an optical fibre assembly; launching one or more test light signals into a solid core optical waveguide of the optical fibre assembly; detecting a portion of the test light signals emitted from the solid core optical waveguide proximate one or both ends of the optical fibre assembly; analysing the detected portion of the test light signal to determine a state of the solid core optical waveguide; deducing a state of the hollow core optical waveguide of the optical fibre assembly from the determined state of the solid core optical waveguide; and designating the optical fibre assembly as operable or inoperable according to the deduced state of the hollow core optical waveguide.
2 . The method according to claim 1 , wherein the optical fibre assembly comprises an optical fibre cable, the method further comprising deploying the optical fibre cable as an optical signal transmission pathway before or during the launching of the one or more test light signals.
3 . The method according to claim 1 , wherein the launching, detecting and analysing is in accordance with at least one of a visual fibre tracer technique, a visual fault locator technique, an optical time domain reflectometry technique or an optical frequency domain reflectometry technique for testing optical fibres.
4 . The method according to claim 1 , wherein the optical fibre assembly comprises: a hollow core optical waveguide comprising a hollow core surrounded by a structured arrangement of longitudinally extending capillaries providing an inner cladding surrounded by an outer cladding; a diagnostic solid core optical waveguide comprising a solid core surrounded by a cladding, and extending substantially parallel to the hollow core optical waveguide; and a jacket surrounding both the hollow core optical waveguide and the solid core optical waveguide and forming a common mechanical environment for the hollow core optical waveguide and the solid core optical waveguide.
5 . The method according to claim 4 , wherein one or more properties of the hollow core optical waveguide and of the solid core waveguide are matched, the properties comprising: microbending sensitivity, fundamental mode field diameter, outer diameter of the cladding, macrobend loss, background optical attenuation, and temperature sensitivity.
6 . The method according to claim 4 , wherein the hollow core optical waveguide is a photonic bandgap waveguide configured to guide light along the hollow core by a photonic bandgap effect, the inner cladding comprising a microstructured regular array of longitudinally extending capillaries.
7 . The method according to claim 6 , wherein the hollow core optical waveguide is a nested antiresonant nodeless hollow core waveguide, the inner cladding comprising one or more additional capillaries nested within each longitudinally extending capillary.
8 . The method according to claim 4 , wherein the solid core of the solid core optical waveguide is embedded in the outer cladding of the hollow core optical waveguide so that the outer cladding acts as the cladding of the solid core optical waveguide, and optionally including one or more additional solid cores embedded in the outer cladding to provide one or more additional solid core optical waveguides.
9 . A method of testing a hollow core optical waveguide, the method comprising: providing the hollow core optical waveguide in an optical fibre assembly, wherein the optical fibre assembly comprises: a hollow core optical waveguide comprising a hollow core surrounded by a structured arrangement of longitudinally extending capillaries providing an inner cladding surrounded by an outer cladding; and a diagnostic solid core optical waveguide comprising a solid core surrounded by a cladding, and extending substantially parallel to the hollow core optical waveguide; and launching one or more test light signals into the solid core optical waveguide of the optical fibre assembly; detecting a portion of the test light signals emitted from the solid core optical waveguide proximate one or both ends of the optical fibre assembly; analysing the detected portion of the test light signal to determine a state of the solid core optical waveguide; deducing a state of the hollow core optical waveguide of the optical fibre assembly from the determined state of the solid core optical waveguide; and designating the optical fibre assembly as operable or inoperable according to the deduced state of the hollow core optical waveguide.
10 . The method according to claim 9 , wherein the optical fibre assembly further comprises a jacket surrounding both the hollow core optical waveguide and the solid core optical waveguide and forming a common mechanical environment for the hollow core optical waveguide and the solid core optical waveguide.
11 . The method according to claim 9 , wherein the optical fibre assembly comprises an optical fibre cable, the method further comprising deploying the optical fibre cable as an optical signal transmission pathway before or during the launching of the one or more test light signals.
12 . The method according to claim 9 , wherein the launching, detecting and analysing is in accordance with at least one of a visual fibre tracer technique, a visual fault locator technique, an optical time domain reflectometry technique or an optical frequency domain reflectometry technique for testing optical fibres.
13 . The method according to claim 9 , wherein the hollow core, inner cladding and outer cladding of the hollow core optical waveguide form a first optical fibre strand which has a coating layer, and the solid core and cladding of the solid core optical waveguide form a second optical fibre strand which has a coating layer and is distinct from the first optical fibre strand, the optical fibre assembly further comprises an inner buffer layer surrounding the coated optical fibre strands.
14 . The method according to claim 9 , wherein the hollow core, inner cladding and outer cladding of the hollow core optical waveguide form a first optical fibre strand which has a coating layer, and the solid core and cladding of the solid core optical waveguide form a second optical fibre strand which has a coating layer and is distinct from the first optical fibre strand, and the optical fibre assembly further comprises a filler material occupying space between the coated fibre strands and the hollow tube.
15 . The method according to claim 9 , wherein the optical fibre assembly further comprises an elongate strengthener extending substantially parallel to the hollow core optical waveguide and the solid core optical waveguide.
16 . A method of testing a hollow core optical waveguide, the method comprising: providing the hollow core optical waveguide in an optical fibre assembly of an optical fibre cable comprising a hollow core optical waveguide, a solid core optical waveguide, and a jacket; launching one or more test light signals into the solid core optical waveguide of the optical fibre assembly comprising an optical fibre; detecting a portion of the test light signals emitted from the solid core optical waveguide proximate one or both ends of the optical fibre assembly; analysing the detected portion of the test light signal to determine a state of the solid core optical waveguide; deducing a state of the hollow core optical waveguide of the optical fibre assembly from the determined state of the solid core optical waveguide; designating the optical fibre assembly as operable or inoperable according to the deduced state of the hollow core optical waveguide; and deploying the optical fibre cable as an optical signal transmission pathway before or during the launching of the one or more test light signals.
17 . The method according to claim 16 , wherein the launching, detecting and analysing is in accordance with at least one of a visual fibre tracer technique, a visual fault locator technique, an optical time domain reflectometry technique or an optical frequency domain reflectometry technique for testing optical fibres.
18 . The method according to claim 16 , wherein: the hollow core optical waveguide comprises a hollow core surrounded by a structured arrangement of longitudinally extending capillaries providing an inner cladding surrounded by an outer cladding; the solid core optical waveguide comprises a solid core surrounded by a cladding, and extending substantially parallel to the hollow core optical waveguide; and the jacket surrounds both the hollow core optical waveguide and the solid core optical waveguide and forming a common mechanical environment for the hollow core optical waveguide and the solid core optical waveguide.
19 . The method according to claim 18 , The method according to claim 1 , wherein one or more properties of the hollow core optical waveguide and of the solid core waveguide are matched, the properties comprising: microbending sensitivity, fundamental mode field diameter, outer diameter of the cladding, macrobend loss, background optical attenuation, and temperature sensitivity.
20 . The method according to claim 18 , wherein the hollow core optical waveguide is a photonic bandgap waveguide configured to guide light along the hollow core by a photonic bandgap effect, the inner cladding comprising a microstructured regular array of longitudinally extending capillaries.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a division of U.S. patent application Ser. No. 17/281,330 filed Mar. 30, 2021, which is a National Stage of PCT International Application No. PCT/GB2019/052772 filed on Oct. 2, 2019, which claims priority to GB Application No. 1816146.3 filed Oct. 3, 2018, all of which are hereby incorporated by reference. BACKGROUND OF THE INVENTION The present invention relates to optical fibre assemblies and methods of using the optical fibre assemblies. An important use of optical fibres is in the transmission of data, such as in telecommunications applications, over both short and long distances. Conventionally, optical fibres having a solid waveguiding core configured for the propagation of a single optical mode (single mode or SM fibre) or multiple optical modes (multimode or MM fibre) have been used. A widely-used example is silica optical fibre carrying optical signals at a wavelength of about 1550 nm, where silica has its lowest loss so that signals can be propagated over long distances with the minimum attenuation. Optical fibres for carrying data signals can be packaged into cables including one or more fibres within an outer jacket that protects the fibres during deployment and use of the fibres. During installation of a cable and for subsequent maintenance, various testing techniques can be used to establish that data transmission is effective and the fibres are free from defects such as breaks or significant bends that induce additional loss. Techniques include use of a visible fibre tracer, a visual fault locator and an optical loss test set (OLTS) to check for breaks during and following cable installation (continuity testing), measurement of the attenuation level in the installed fibre (insertion loss) using an OLTS, and optical time domain reflectometry (OTDR) or occasionally optical frequency domain reflectometry (OFDR) measurements on the installed fibre to verify the distributed optical loss profile along the fibre length, quality of the installation and for maintenance. Visual fibre tracer and visual fault locator testing methods use visible light, and OTDR measures backscatter from within the optical fibre. Accordingly, these techniques are well-adapted for conventional solid core optical fibre cables, but tend to work poorly or not at all with a more recently developed type of optical fibre, namely hollow core optical fibres, which use a structured inner cladding to produce a waveguiding function. Often, a hollow core structure does not transmit visible light, and the absence of material in the central core can reduce Rayleigh backscattering below levels required by both widely deployed standard and high performance specialist OTDR systems. Hollow core optical fibres are of significant interest for optical data transmission applications. They provide an alternative to conventional solid core fibres that offers a wide optical transmission bandwidth and low transmission loss, and enables the propagation of higher optical powers free from issues such as nonlinear and thermo-optic effects that can affect optical waves travelling in solid material. However, their incompatibility with conventional testing methods is a significant obstacle to developing this application; testing the quality of installation and longer terms checks of the integrity and performance quality of hollow core optical fibres installed in the field is challenging. Therefore, approaches to enable the testing of hollow core optical fibres and cables including hollow core optical fibres, including testing during installation and for subsequent maintenance, are of interest. SUMMARY OF THE INVENTION Aspects and embodiments are set out in the appended claims. According to a first aspect of certain embodiments described herein, there is provided an optical fibre assembly comprising: a hollow core optical waveguide comprising a hollow core surrounded by a structured arrangement of longitudinally extending capillaries providing an inner cladding surrounded by an outer cladding; a diagnostic solid core optical waveguide comprising a solid core surrounded by a cladding, and extending substantially parallel to the hollow core waveguide; and a jacket surrounding both the hollow core optical waveguide and the solid core optical waveguide and forming a common mechanical environment for the hollow core optical waveguide and the solid core optical waveguide. According to a second aspect of certain embodiments described herein, there is provided an optical fibre cable comprising or including at least one optical fibre assembly according to the first aspect. According to a third aspect of certain embodiments described herein, there is provided a method of testing a hollow core optical waveguide, the method comprising: providing the hollow core optical waveguide in an optical fibre assembly according to the first aspect; launching one or more test light signals into the solid core optical wave