Questions tagged [fiber-optics]

Fiber optics is the study of optical fibers, which are thin pieces of high quality optical materials which are able to act as a waveguide for some frequencies of light. This waveguide or 'light pipe' feature of optical fibers allows them to transmit light with very low loss from one end of the fiber to the other.

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13
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1answer
3k views

Can a burning laser be directed through fiber optics?

Can a laser powerful enough to cut(100w for example) be redirected using fiber optics ? What issues need to be considered? To be clear it should retain the ability to cut after exiting the fiber.
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How do non-mechanical solid-state optical switches work?

I am currently looking for a fiber-optical switch (FOS) in order to be able to change the light source of a spectrometer. As this will be used in harsh conditions, I was hoping to find a FOS with no ...
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Focusing light into an optical fiber cable

I'm trying to focus light from a flashing light lamp throught two lens into a optical fiber cable which is around 0.8cm in diameter. flashing light: a bulb and then covered by a glass of 7.5cm x 7cm ...
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Does optical fiber preserve the angles of incoming light?

I am reading up on optical fibers and there's one thing I haven't understood yet: Does an optical fiber preserve the angles of incoming light? For example, if we light two LEDs in front of an ...
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2answers
914 views

Single-mode fibers and ray-theory of light

I have read ray-theory cannot be applied to single-mode fibers. Why? I know rays are kind of an approximation to describe the real behavior of light, and electromagnetic theory and photonics are ...
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3answers
695 views

Fiber optics with broadband, incoherent light

I wonder if someone could help clarify waveguiding with broadband, incoherent light please. If we take a telecomms fiber, which is single-moded above ~1.4 μm and couple a laser beam in, we assume ...
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3answers
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Cladding of optical fibers

Why do optical fibers usually have a cladding? Ok, if you put make a bundle of optical fibers this prevents that light leaks from one fiber to another fiber in contact. However, are there other ...
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4answers
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Intensity fluctuations at the output of a single mode fiber coupled to a He Ne laser

I have coupled a Thorlabs HNL050L-EC - HeNe, 632.8 nm, 5 mW, Polarized Laser to a 2 meter long single mode fiber patch chord using a Thorlabs F230-FC-B aspheric lens. While I am certainly able to ...
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5answers
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Why should optical fibers be thin?

What are the reasons that optical fibers have to be thin (small radius of the fiber)? Is there a good picture which explains this in detail?
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Efficiencies of Coupling Light into a Fiber

I am in AMO Physics and work a lot with optics. I just wanted to get an idea of what coupling efficiencies one "should" get in a "reasonable time"* by coupling light into a fiber using different ...
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Meaning of imaginary part of complex field amplitude for waveguide modes (e.g. TE, TM, HE, EH)

In classical waveguide analysis (e.g. for optical fibers, as in the notes Modal analysis of step-index fibers, ECE 4006/5166 Guided Wave Optics, Robert R. McLeod, University of Colorado), one can find ...
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3answers
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Calculating reflection of light when the refractive index changes continuously

Suppose you have 2 materials, one with refractive index $n_1$ and the other with refractive index $n_2$, and a plane-wave coming from the first material hits the interface with an incident angle of $0^...
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878 views

Will overlapping two different beams of coherent light with different wavelength cause interference?

If I use two different wavelength lasers to transmit light into a single mode optic fiber will they interfere with each other? If so, how much will be that interference.
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1answer
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What happens if we use an optical fibre for light at a different wavelength than the one specified on the fibre?

Say the fibre is for 700 nm, and we shine light at 1064 nm into it. Would it change the mode? The polarisation? The beam shape (i.e. introducing ellipticity in the beam)?
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1answer
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I do not understand the operating principle of a subwavelength-diameter optical fiber?

I would love to know the difference in the transmission principle of light between a subwavelength-diamater optical fiber and a single-mode optical fiber. Please explain me the path of light in the ...
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426 views

Combining the energy from two optical fibers transmitting visible light

Can this be done? It wouldn't violate energy conservation... I've tried looking at 1xN beamsplitters used in reverse. But it won't work, since using them in reverse also splits the incoming power ...
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1answer
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Effective refractive index calculation of fiber core

Can someone pls explain what is effective refractive index of fiber core and how to calculate it theoretically? Suppose the fiber core refractive index=1.4446 and cladding refractive index is= 1.4271, ...
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1answer
331 views

How does a 2D MEMS based optical cross-connect control its mirrors?

Concerning fiber optics, I'd like to know how a 2D MEMS based optical cross-connect is able to switch optical signals. I've read that these mirrors are controlled with electrical signals to be either "...
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68 views

Measuring higher laser output behind single mode optical fiber than in front of it

I have a setup which includes a 637 nm toptica iBeamSmart laser which is reflected off two mirrors, passes through a line of dichroics (that should completely transmit it, they are used to couple ...
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3answers
463 views

Does light travel through a waveguide faster than electricity through a wire

So I have heard that using photons to compute is faster than electrons. I was wondering why exactly that is? Is it because light travels through a waveguide faster than electricity through a wire?
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Proper and rigourous derivation of Gaussian beam?

Gaussian beams are known solutions to the Paraxial Wave Equation: $$ \frac{\partial^2 \Psi(x,y,t)}{\partial^2 x} + \frac{\partial^2 \Psi(x,y,t)}{\partial^2 y} = 2ik\frac{\partial \Psi(x,y,t)}{\...
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Light in fibre optic cables

Imagine a fibre optic cable stretching from London to New York (5571 km) carrying a data signal This data signal is split into two parts, red and blue light Both signals start travelling down the ...
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3answers
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Why does a prism spread its "output" out over space, not time?

I'm having fun learning about the physics of optical networks at a new job. It's fun connecting elementary physics learned so many years ago with how they're leveraged today in practical application. ...
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818 views

Polarized light in single mode fiber

In single mode fiber the light propagates in two orthogonal planes. Input will be linearly polarized light, which state of polarization will be on output and why? And if there will be some different ...
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2answers
66 views

How is metadata transmitted alongside data, through light pulses (e.g. fibre optic)?

So fiber optic is used top transfer information around the world, including this post, between my computer and the SE server, wherever that is. But as I read, that info is transmitted through light ...
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2answers
826 views

What is the purpose of glass in common mirrors? [closed]

We know that the image is formed by the silver layer, so why don't we use silver layer on some other material in household mirrors?
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1answer
130 views

Can I (in principle) make an analog fibrescope/borescope for consumer phones using only a fibre optic cable? [closed]

This question is testing my (limited) understanding of optics. Here is the background. Many endoscopes work by using a fiber optic light guide to transmit light to a camera which sits at the end of ...
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1answer
2k views

Are fibre optic cables immune to electro-magnetic interference?

One benefit of fiber optic cables popularly cited is that they are "immune" to electro-magnetic interference. [See http://services.eng.uts.edu.au/~akadi/ite/major_assignments/barber/advdisad.htm] My ...
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3answers
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How to excite a certain mode in a waveguide?

Does anyone know how we can excite a certain mode, e.g. the second order mode, in a waveguide? I'm a little confused. According to the ray-optics theory, modes are related with incident angles, which ...
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1answer
2k views

How I can launch light into PM fiber

A polarization maintaining fiber preserves the linear polarization of the light at the output, the light at the input must be linear polarized to see signal at the photodetector... However I can't see ...
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2answers
2k views

Numerical aperture (NA) of an optical fiber

The Numerical Aperture (NA) (for fiber optics) is usually used to denote the acceptance cone for a multi-mode fiber. Does NA also describe the expansion of light emitted from the end of a fiber? I ...
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2answers
390 views

Mean free path of a photon in a fiber

Is there a way to calculate, or a reference table I can to look up which provides the average distance a photon travels before it encounters an electron and is absorbed or re-emitted in a fiber optics ...
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1answer
365 views

Does a lens with a given numerical aperture (NA) increase etendue, even if it follows a source (e.g. fiber) with lower NA?

It is well known that the etendue of an optical system cannot be decreased - i.e. the brightness of a source cannot simply be increased by using lenses to try and focus something more tightly. ...
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1answer
580 views

Mode groups in an optical fiber

I know what modes in an optical fiber mean but what are exactly mode groups in an optical fiber? From what I read until now, I have the impression that modes that have close propagation constants ...
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0answers
43 views

Attenuation in microwave and optical communications

I have read that the attenuations of microwave transmission lines and optical fibers are ~1 db/m and ~ 0.2 db/km, respectively. I understand that these values depend on the geometry, design, and ...
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0answers
59 views

Can I couple 1064 nm and its harmonic 532 nm in a single polarization maintaining fiber?

I have an experiment where I need to get a largish (40 mW) amount of 532 nm light and small amount (<50 µW) of 1064 nm light into a device under test. I need something with stable polarization so ...
3
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1answer
48 views

Temporal structure in multimode fiber during high-power application

I am trying to couple a 532nm laser with a 200 ns square pulse into an optical fiber (fused silica with damage threshold ~ 500 MW/cm^2). At lower intensities, < ~30 MW/cm^2, I see about what I ...
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0answers
697 views

Is it possible to use a tapered fiber to collimate a single-mode light beam?

I would like to collimate a light beam stemming from a single-mode LED source. As the source is pretty big (a few millimeters), collimation with a single lens gives a bad result, i.e. a quite ...
2
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3answers
498 views

How noisy are photon detectors?

I have a single photon detector and $N$ photons per second arrive at the detector. Then something happens and the number of incoming photons per second changes by the factor of $\alpha$. So now $(1+\...
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2answers
286 views

Photon dispersion in an optical fiber

What is the law of spatial dispersion of a photon in an optical fiber? Say I have a femto second photon ($\lambda$ around $700\,\text{nm}$) with gaussian shape ($\sigma = c\cdot 1\,\text{fs}\approx 3\...
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1answer
587 views

Solar energy and optical fiber

I'm not really good at science or physics, just wanted to ask about the idea (doesn't have an opportunity to test this). Will this scheme work and what can be its efficiency?(The goal is to make ...
2
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2answers
623 views

Self-phase modulation induced spectral broadening

How does one explain the fact that a pulse that has its phase modulated through SPM, generates new frequencies? How does the phase modulation affect the electrons so they emit not only the frequencies ...
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2answers
767 views

Modes in optical fibers

I am trying to understand the modes in step-index optical fibers and I saw that they say the electric field distribution in the core and cladding is as bellow. my question is that which component of ...
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1answer
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Understanding of a" Mode" in Optical Fibers

Basically, I am aware of single mode and multi mode fibers. I have also been reading about transverse electric and magnetic fields , their corresponding modes and TEM modes. Now I am a little bit ...
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1answer
60 views

Solar Sailing with Optical Amplification

The solar sail has been proposed as a means of carrying payloads into deep space without traditional thrusters. Most approaches seem to require a thin reflective chute that unfurls to a shape oriented ...
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1answer
272 views

What degenerates mode in a fiber have in common? Do they have the same eigenvalues?

According to the definition degenerates modes in a optical fiber "have the same propagation constants". These modes can be combined to from the linearly polarized modes. This "constant" should be the ...
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1answer
43 views

Brillouin scattering in multimode fibers

Fiber ring resonators made up of single mode fibers often incorporate an optical isolator to suppress the build-up of Brillouin scattering. However, ring resonators made of multimode fibers generally ...
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1answer
73 views

Why are bend losses higher at higher wavelengths in fiber optic cables

I have been reading about fiber optic cables for the past few months, specifically about bend losses. It is often mentioned that bend losses are higher at longer wavelength light and indeed this is ...
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2answers
318 views

Does the speed of light transmission in an optical fiber change with the refractive index of the surrounding material?

I am learning about distributed fiber optic sensors where properties along the cable can be continuously determined, eg. temperature from Raman backscatter shift at a resolution of ~0.1 C at ~1 m ...
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1answer
283 views

How can I estimate optical bending loss?

I just learned from a previous question that light encounters bend loss moving around curves in optical cable. Why is this and how can I calculate it?

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