Limiting loss in leaky fibers
A theoretical understanding of what makes some hollow-core optical fibers
more efficient than others will inspire the design of new low-loss fibers

Date:
July 3, 2023
Source:
University of Bath
Summary:
Scientists have developed a mathematical model to explain how
antiresonant hollow-core fibers guide light in a way that keeps data
loss ultra-low. Until now, scientists had no complete explanation
for this well-observed phenomenon.


Facebook Twitter Pinterest LinkedIN Email

==========================================================================
FULL STORY ==========================================================================
A theoretical understanding of the relationship between the geometrical structure of hollow-core optical fibres and their leakage loss will
inspire the design of novel low-loss fibres.

Immense progress has been made in recent years to increase the efficiency
of optical fibres through the design of cables that allow data to
be transmitted both faster and at broader bandwidths. The greatest
improvements have been made in the area of hollow-core fibres -- a
type of fibre that is notoriously 'leaky' yet also essential for many applications.

Now, for the first time, scientists have figured out why some air-filled
fibre designs work so much more efficiently than others.

The puzzle has been solved by recent PhD graduate Dr Leah Murphy and
Emeritus Professor David Bird from the Centre for Photonics and Photonic Materials at the University of Bath.

The researchers' theoretical and computational analysis gives a clear explanation for a phenomenon that other physicists have observed in
practice: that a hollow-centred optical fibre incorporating glass
filaments into its design causes ultra-low loss of light as it travels
from source to destination.

Dr Murphy said: "The work is exciting because it adds a new perspective
to a 20-year-long conversation about how antiresonant, hollow-core fibres
guide light. I'm really optimistic that this will encourage researchers to
try out interesting new hollow-core fibre designs where light loss is kept ultra-low." The communication revolution Optical fibres have transformed communications in recent years, playing a vital role in enabling the
enormous growth of fast data transmission. Specially designed fibres have
also become key in the fields of imaging, lasers and sensing (as seen, for instance, in pressure and temperature sensors used in harsh environments).

The best fibres have some astounding properties -- for example, a pulse
of light can travel over 50km along a standard silica glass fibre and
still retain more than 10% of its original intensity (an equivalent
would be the ability to see through 50km of water).

But the fact that light is guided through a solid material means current
fibres have some drawbacks. Silica glass becomes opaque when the light it
is attempting to transmit falls within the mid-infrared and ultraviolet
ends of the electromagnetic spectrum. This means applications that need
light at these wavelengths (such as spectrometry and instruments used
by astrophysicists) cannot use standard fibres.

In addition, high-intensity light pulses are distorted in standard fibres
and they can even destroy the fibre itself.

Researchers have been working hard to find solutions to these drawbacks, putting their efforts into developing optical fibres that guide light
through air rather than glass.

This, however, brings its own set of problems: a fundamental property
of light is that it doesn't like to be confined in a low-density region
like air.

Optical fibres that use air rather than glass are intrinsically leaky
(the way a hosepipe would be if water could seep through the sides).

The confinement loss (or leakage loss) is a measure of how much light
intensity is lost as it moves through the fibres, and a key research goal
is to improve the design of the fibre's structure to minimise this loss.

Hollow cores The most promising designs involve a central hollow core surrounded and confined by a specially designed cladding. Slotted within
the cladding are hollow, ultra-thin-walled glass capillaries attached
to an outer glass jacket.

Using this set-up, the loss performance of the hollow-core fibre is
close to that of a conventional fibre.

An intriguing feature of these hollow-core fibres is that a theoretical understanding of how and why they guide light so well has not kept up
with experimental progress.

For around two decades, scientists have had a good physical understanding
of how the thin glass capillary walls that face the hollow core (green
in the diagram) act to reflect light back into the core and thus prevent leakage. But a theoretical model that includes only this mechanism greatly overestimates the confinement loss, and the question of why real fibres
guide light far more effectively than the simple theoretical model would predict has, until now, remained unanswered.

Dr Murphy and Professor Bird describe their model in a paper published
this week in the leading journal Optica.

The theoretical and computational analysis focuses on the role played
by sections of the glass capillary walls (red in the diagram) that face
neither the inner core nor the outer wall of the fibre structure.

As well as supporting the core-facing elements of the cladding, the Bath researchers show that these elements play a crucial role in guiding
light, by imposing a structure on the wave fields of the propagating
light (grey curved lines in the diagram). The authors have named the
effect of these structures 'azimuthal confinement'.

Although the basic idea of how azimuthal confinement works is simple, the concept is shown to be remarkably powerful in explaining the relationship between the geometry of the cladding structure and the confinement loss
of the fibre.

Dr Murphy, first author of the paper, said: "We expect the concept
of azimuthal confinement to be important to other researchers who are
studying the effect of light leakage from hollow-core fibres, as well
as those who are involved in developing and fabricating new designs."
Professor Bird, who led the project, added: "This was a really rewarding project that needed the time and space to think about things in a
different way and then work through all the details.

"We started working on the problem in the first lockdown and it has now
been keeping me busy through the first year of my retirement. The paper provides a new way for researchers to think about leakage of light in hollow-core fibres, and I'm confident it will lead to new designs being
tried out." Dr Murphy was funded by the UK Engineering and Physical
Sciences Research Council.

* RELATED_TOPICS
o Matter_&_Energy
# Optics # Graphene # Construction # Biochemistry
o Computers_&_Math
# Computer_Modeling # Computational_Biology #
Mathematical_Modeling # Spintronics_Research
* RELATED_TERMS
o Mathematical_model o Earth_science o Statistics o
Introduction_to_quantum_mechanics o 3D_computer_graphics
o Computer_simulation o Electroluminescence o
Scientific_visualization

==========================================================================

Print

Email

Share ========================================================================== ****** 1 ****** ***** 2 ***** **** 3 ****
*** 4 *** ** 5 ** Breaking this hour ==========================================================================
* Screens_More_Versatile_Than_LED:_Fins_and_...

* GM_Pig_Heart_in_a_Human_Patient:_Update *
Multiple_Sclerosis_Severity * Wind_Farm_Noise_and_Road_Traffic_Noise
* Mavericks_and_Horizontal_Gene_Transfer *
Early_Reading_for_Pleasure:_Brains,_...

* New_Light_Shed_On_Evolution_of_Animals *
Gullies_On_Mars_from_Liquid_Meltwater?
* DNA_Organization_in_Real-Time *
How_the_Cat_Nose_Knows_What_It's_Smelling

Trending Topics this week ========================================================================== SPACE_&_TIME Astrophysics Galaxies Black_Holes MATTER_&_ENERGY Technology Nature_of_Water Organic_Chemistry COMPUTERS_&_MATH Information_Technology Spintronics_Research Communications


==========================================================================

Strange & Offbeat ========================================================================== SPACE_&_TIME First_'Ghost_Particle'_Image_of_Milky_Way Gullies_on_Mars_Could_Have_Been_Formed_by_Recent_Periods_of_Liquid_Meltwater, Study_Suggests Earliest_Strands_of_the_Cosmic_Web MATTER_&_ENERGY Displays_Controlled_by_Flexible_Fins_and_Liquid_Droplets_More_Versatile, Efficient_Than_LED_Screens Turning_Old_Maps_Into_3D_Digital_Models_of_Lost_Neighborhoods NeuWS_Camera_Answers_'Holy_Grail_Problem'_in_Optical_Imaging
COMPUTERS_&_MATH 'Electronic_Skin'_from_Bio-Friendly_Materials_Can_Track_Human_Vital_Signs_With Ultrahigh_Precision Researchers_Make_a_Quantum_Computing_Leap_With_a_Magnetic_Twist Physicists_Discover_a_New_Switch_for_Superconductivity Story Source:
Materials provided by University_of_Bath. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Leah R. Murphy, David Bird. Azimuthal confinement: the missing
ingredient
in understanding confinement loss in antiresonant, hollow-core
fibers.

Optica, 2023; 10 (7): 854 DOI: 10.1364/OPTICA.492058 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230703133108.htm

--- up 1 year, 18 weeks, 10 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)