# What is Fibre: Definition and 88 Discussions

Fiber or fibre (from Latin: fibra) is a natural or man-made substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate fibers, for example carbon fiber and ultra-high-molecular-weight polyethylene.
Synthetic fibers can often be produced very cheaply and in large amounts compared to natural fibers, but for clothing natural fibers can give some benefits, such as comfort, over their synthetic counterparts.

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1. ### Engineering Photonics / Fibre Optics - (Supermodes, PBGFs, Coupling)

Hi, Looking for a good photonics / fibre optics textbook that covers the field, while also addressing said topics in the title. Thank you!
2. ### Most compressible volumes: synthetic fibre versus natural eider down?

I'm just purchasing some exped kit including coats and sleeping bags containing down as the insulator. The key superlative of down is that it can be compressed and then recovers to a big volume. If one ounce of material re-expands, after compression, to 800 cubic inches then this is called '800...
3. ### Vacuum Tank Query (Aluminium, Carbon Fibre, etc, Composition)

Hi, I'm hoping this will be a fairly easy question for someone on here to answer. If I wanted to make a (small?) vacuum tank (basically a hollow cylinder capped with two similarly hollow hemispheres - like so: (===)), how thick would the walls of the tank need to be for it to withstand the...
4. ### Relationship between Excess Pressure and Surface Tension for a Drop on a Fibre

Homework Statement Think of a drop of radius ##R## deposited on a fibre of radius ##b(b<<L)##.Find ##{\Delta{P}}## Homework Equations The relationship between excess pressure and the surface tension is given by Yong-Laplace equation, $$\Delta{P} = \sigma{(\frac{1}{R_1}+\frac{1}{R_2})}$$ The...
5. ### Attenuation Coefficient in an optical fibre

Homework Statement In a particular fibre, the attenuation coefficient for Rayleigh scattering is measured to be 0.30 dB/km at 1.20 μm. (a) How large would it be expected to be at 0.80 μm? (b) Ignoring other sources of attenuation, if a signal of a certain initial power was sent over a...
6. ### What is the internal radius of the optical fibre

Homework Statement A Capillary tube is made of glass of refractive index n1 . The outer radius of the tube is R.The tube is filled with a liquid of refractive index n2 < n1 .what should be the minimum internal radius of the tube so that any ray that hits the tube would enter the liquid...
7. ### Fibre attenuation with absoring cladding

Homework Statement Given a single mode fibre with non-absorbing core and absorbing cladding where the power propagating in the fundamental mode is split 70%:30% between core and cladding, calculate overall attenuation of the mode along the fibre in dB/km at 1550nm source wavelength where the...
8. ### I Understanding Fibre Bundles: A Layman's Guide

Hello! I am having some troubles understanding fibre bundles and I would be really grateful if someone can explain them to me in layman terms (at least how to visualize them). To begin with, I am not sure what is the fibre bundle, is it the projection function, or the total space (or something...
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### Carbon fibre tube -- is round or oval stronger?

Hi all, my question is if i have a length of carbon fibre tube, one is round the other is oval and orientated along its longest side is it more stiff than the round one? Reason for asking is i am trying to make a telescopic carbon fibre pole that is more rigid than the round ones on the market...
10. ### Single-mode optical fibre output not Gaussian?

Is there anything that would make a single mode fibre's speckle pattern not look Gaussian? I've attached two images (below) The Fibre C speckle pattern looks multimode The Fibre A speckle pattern doesn't really look convincingly like multimode or like single mode. A HeNe laser was used to...
11. ### How does Total Internal Reflection in a mm/sm fiber work?

I know Snell's Law and I do understand that there are single and multimode fibers. A fiber carries light hence to total internal reflection. so far so good. But is it only a single mode fibre that works with total internal reflection? And if so, how does the multimode fibre carry light then?
12. ### How to specify carbon fibre material properties in ANSYS ACP

Hey there, my honours year thesis is on the design and analysis of a carbon fibre wheel for a Formula Student racecar. However, I am unable to obtain carbon fibre material properties to input into the Engineering Data section. I am required to specify the Youngs Modulus in the x, y and z...
13. ### Glass fibre Aquarium pool minimum thickness?

Hello, I am working on a Project and it has been a while since i did calculations With mechanics. The pool would be made in glassfibre with polyester and will be: L=2000mm W= 1750mm h= 400mm we use the E-module for glass, so we use E= 70 000 N/mm2 I= bh3/12 = 2000mm x 4003 mm /12 = 1,067 x...
14. ### Maximum angle of acceptance - optical fibre

Hi all Tearing my hair out trying to calculate the Maximum acceptance angle for a problem. Experiment involved shining a laser into a tube of water. I have calculated the angle of refraction based on the average of two critical angles (one known and one measured manually) as 52.49 degrees...
15. ### Amyloid Fibres: Understanding Elasticity & Bending Angles

Hello, I`m studying amyloid fibres, which are filamentous proteins that intertwine between them (from 2 to 4 and more) and form fibres (2-20nm thick). I see that when that below a threshold length, the fibre is linear, beyond the threshold length, the fibre bend always with the same, constant...
16. ### Power backups for fibre optic networks

Can anyone tell me what kind of power back ups they use for fiber optic networking equipment in ISP networks and across the world. Do they tend to all use UPS from batteries or do they have generators for in the events of major long term power outages?
17. ### How does graded-index material reduce pulse spreading in optical fibres?

Homework Statement [/B] The textbook is talking about pulse spreading/dispersion in optical fibres. Book says: "The spreading of the pulse is due to two dispersion effects: (i) Chromatic dispersion occurs because the refractive index of the fibre is different for different frequencies...
18. ### Can Fiber Optic Cables Create Coherent Light Circuits?

By what we know, optic cable can guide waves by TIR. So what if it guides into itself, for instance, to keep it virtually flat and high angle reflection; I lay cable around the circumference of the planet and it loops back into itself with double entry: one guided and other newly introduced with...
19. ### Understanding Modes in Fibre: Equations for Allowed Angles of Propagation

So I've got the equation for 'allowed angles of propagation': SinΘp = pλ / 2πdnf With p is the mode, λ the wavelength, d the width and n the refractive index. I'm just not sure what to do with this equation, and my lecture notes don't go into any more detail. For example, if I knew the the max...
20. ### Fibre optics and multipath disspersion

Hey I don't understand why multipath disspersion doesn't occur still when monochromatic lights are directed at a fibre obtic. (For example sending dozens of infrared waves at the same time). Wouldn't they still overlap and perhaps superpose?
21. ### Light pipes - is there a limit

I have seen light pipes which "conduct" sunlight from an outdoor receptor to the dark recesses of buildings ... but they all seem to be awkward bulky metallised tubes. Is it not possible to achieve the same effect with fibre optics? Could one not focus the light at the receptor into a...
22. ### Making a Nylon - Fibre Composite

Hi, I was tasked to design a composite material that will undergo a 3 point bending test. Maximum deflection will be of 15mm and a maximum load of 5kN. The scope of this task is not to prevent failure but to analyse the composite and learn from the design process. Nonetheless the composite...

24. ### Fibre Optic Questions: Understanding Cladding and Critical Angle

Hi, I have some fibre optics questions that I can't seem to get my head around. How does providing a cladding of a refractive index slightly lower than the core increase the critical angle? I can do the mathematics to see that it does however is there a logical explanation. Why is increasing...
25. ### When is a foliated manifold a fibre bundle?

I k-foliation of a ##n##-manifold ##M## is a collection of disjoint, non-empty, submanifolds who's union is ##M##, such that we can find a chart ##(U,x^1, \ldots mx^k, y^{k+1}, \ldots, y^n)=(\phi, (x^\mu, y^\nu))## about any point with the property that setting the ##n-k## last coordinates equal...
26. ### Number of reflections in an Optical fibre

How many reflections will be made by a light entering a 2m long optical fibre cable. If the angle of incidence with the axis of the core is 3.43° . Given that the core diameter and refractive index are 60μm and 1.48 respectively I got the answer as 36368.48 is this correct? L=2m...
27. ### Fibre optics for use in lighting?

Is it possible to send enough light down a fibre optic cable to produce say 1000 Lumens? How would I go about calculating this? My thoughts here are using fibre optic cables to transfer light from the rooftops of buildings to the rooms inside. Is it possible? I know fibre optics are used to...
28. ### Is Fibre Bundles Cartan's Generalization of Klein's Erlagen Program?

As I understand it, Felix Klein sought to classify geometries with respect to what groups G that respected the structure of the given space X. Lately i read in an article on "the history of connections" by Freeman Kamielle that Cartan wished to generalize this notion. Is it correct to think of...
29. ### Difference between physical reach and logical reach of fibre optic

Difference between "physical reach" and "logical reach" of fibre optic Undergrad physics student here, working with fibre optic cables for my final year project, specifically to do with amplifying signals for fibre-to-the-home internet service. I understand the physical reach of fibre optics...
30. ### Incident Angle Limitation Derivation in Optical Fibre

Homework Statement derive the angle of limitation sinθ=[(n2^2-n3^2)^1/2]/n1 n1 is the air out side of the fibre n2 is inside of the fibre n3 is the fibre wall Homework Equations Snells Law: n1sinθ1=n2sinθ2 The Attempt at a Solution I'm pretty stuck and don't really know...
31. ### Exploring Fibre Optic Bandwidth & Single Mode

It's given, "fibre optics are thin to accommodate single electromagnetic mode" what do they mean by single electromagnetic mode...? And also mentioned it has high bandwidth, i know that bandwidth is difference of highest and lowest frequencies of the signal. So if fibre optics has high...
32. ### Modelling buckling of long thin carbon fibre tubes

Hi all, I´m a researcher in computational biology thinking on topics quite far from my field. I want to model long thin-walled tubes of dimensions like those treated here, for example: ≈2 m long, radius ≈50mm and thickness ≈1mm. The tubes I´m interested in should be made of...
33. ### On local trivializations and transition functions of fibre bundles

Hi everyone! I would like to ask you some clarifications on an explicit example of local trivializations and transition functions of fibre bundles: namely on the [-1,1]\hookrightarrow E\rightarrow S^1 bundle (which I guess is the simplest possible example). Following Nakahara (chapter 9...
34. ### How Do Fiber Optic and Copper Cables Differ in Physics?

Hey I am about to start a research paper on the physics concepts involved in relation to fibre optic cabling and copper cabling. In my report I have to discuss how the physics in both relate and differ from one another. In terms of fibre optic cabling I have decided to talk about snell's law...
35. ### Uncertainty principle regarding a narrow optical fibre?

If we take a narrow aperture(such as the one used in the double slit experiments) and attach a length of optical fibre to it, surely now we know the position (confined by the width of the fibre) and also the momentum(defined by the direction of the fibre). How does the uncertainty principle...
36. ### Acceptance Angle in Optical fibre

According to the derivation of acceptance angle the first step is, The condition for Total Internal reflection(TIR) is sin(i)≥n2/n1, where i is angle of incidence in the core, n2= refractive index of the cladding and n1=refractive index of the core. sin(i(c))=n2/n1, where i(c) is the...
37. ### Why is there no fibre for microwave (or other) frequencies?

Optical fibre communication depends on total internal reflection at the core-cladding boundary. Why not use the same principle for other portions of the spectrum? After all, total internal reflection occurs at all frequencies.
38. ### Build a Home Laser Engraver for Aluminum w/ LasersTEA

hello, I'm interested in make an fibre laser to engrave in aluminum, however in all foruns where i ask this question everyone sugest me to buy an professional machine. but I'm interested in learn more about this tecnology so i would like to make my own fibre laser. of course some componets i...
39. ### Refractive Index of Optical Fibre Core and Cladding

Homework Statement I need to find the refractive indexes of the core and cladding of an optical fibre by using the specs found here http://www.photonics.byu.edu/FiberOpticConnectors.parts/images/smf28.pdf Then I'm suppose to calculate the Numerical aperture and compare it with the one listed...
40. ### Path difference in Fibre Optics

Hi, This is a question from a homework which has stumped me: Light is traveling along a fibre optic cable of refractive index 1.52, the refractive index of the cladding is 1.51 and the critical angle between the two is 82. a) what is the most direct route for light along the fibre-optic cable...
41. ### High temperature fibre optic strain adhesive anyone?

So I am currently using a high temperature epoxy based strain adhesive on a polyimide coated single mode fibre. This however gives rubbish results in terms of creep at anything above 160 deg C. Does anyone have any experience with this type of problem at all? I know that there are...
42. ### Collimating light from Optical fibre problem

Homework Statement A thin lens of focal length f is used to collimate the light emerging from two different optical fibres. When used with a first fibre of small core diameter and numerical aperture NA it acheives a diffraction limited divergence of θ1 for the collumated beam. Find the...
43. ### Maths Video：Visible Fibre Bundle

Here is my maths seminar video:Visible Fibre Bundle,discussing the vivid picture of fibre bundle which is the basic concept in the modern differential geometry. My English is poor,but I think the maths ideal is helpful and interesting...
44. ### Understanding the Fibre Bundle Structure of Mobius Band

I don't understand the fibre bundle structure of the Mobius band, described by my textbook. "The base space ##X## is a circle obtained from a line segment L as indicated in Fig. by identifying its ends. The fibre ##Y## is a line segment. The bundle ##B## is obtained from the product ##L \times...
45. ### Aligning a laser with a single-mode fibre

Does anybody have any tips for doing this well? Frankly, I'm pretty terrible at it. I mean, once I get a small amount going through, I can do a little bit of optimisation by adjusting the angle of the fibre in one direction, and then adjusting the angle of the incident beam along the same plane...
46. ### Longitudinal modes in a fibre laser

Hi In the Wiki article on longitudinal modes (http://en.wikipedia.org/wiki/Longitudinal_mode) they state that: "The analysis of longitudinal modes is especially important in lasers with single transversal mode, for example, in single-mode fiber lasers. The number of longitudinal modes of such...
47. ### Fibre bundles for describing gauge invariance

Hello all ! My question: Does fibre bundles are necessary for describing gauge invariance in electromagnetic case? Or fibre bundles uses only for describing gauge invariance in cases of weak, electroweak and strong interactions? Thanks
48. ### Refractive index of optical fibre

http://www.fiberoptics4sale.com/Merchant2/fofs_img/how-optical-fiber-works.gif The refractive index of the core is higher than that of the cladding, I don't understand why!
49. ### Fibre Misalignment and Light Coupling

Hi, I have got a single mode fibre (SMF) with core diameter 8.4 microns. Fibre is aligned in front of horizental reflective surface at a distance of 500 microns. Light from SMF make a spot size of 24 microns and is reflected and coupled back into SMF. However, if I tilt the reflective surface...
50. ### Interference of fibre optic signals with mobile phones' microwaves?

I got an SMS educating people how to find out the presence of a hidden cam in a trial room of a textile showroom or bathroom. It goes like this :- "If you can't make a call in the room,the there is a hidden cam. This is due to the interference of the fibre optic with the signal transfer."...