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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Why is it possible to couple multiple wavelengths into a single mode optical fiber?

I'm quite new to the mode theory, but as I understand, single mode fiber should only allow a single pattern of wavelength + polarization. I'm assuming a non-modulated non-coherent light (a white LED, ...
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Coupling a light source into an optical fiber ring

My question is whether the following scenario is realistic. Imagine coupling a source of photons (say a laser) into a ring made of an optical fiber using a y-junction. (see picture) If the ...
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Why are daylighting fibre optics so much more inefficient than other fibre optic cables?

Comparing Optical Fiber Light Tubes losses and regular Fiber Optic Losses, there seems to be a large disparity. The light tubes reach 100m, whereas the regular ones go for kilometers. I've tried to ...
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How to derive group velocity dispersion (GVD)?

I'm trying to arrive to the following expression to group velocity dispersion: $$\text{GVD} = \frac{\lambda^3}{2 \pi c^2} \frac{d^2n}{d \omega^2}.$$ I know that GVD can be expressed as: $$\text{GVD} = ...
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What causes the relationship between fiberoptic core diameter and wavelength?

I am wondering what is the relationship between the wavelength of the light which can propagate by total internal reflection inside a fiberoptic cable core. Is there a phenomenon which dictates the ...
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Dispersion / group velocity in tapered fiber

dispersion in fibers are defined as: $$D=-\frac{2 \pi c}{\lambda^2}\ddot{\beta}$$ where: $$\ddot{\beta}=-\frac{1}{v_g^2}\frac{dv_g}{d\omega}$$ where $v_g$ is group velocity Does the group velocity / ...
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Difference of refractive indices of fiber layer

recently I received a simulation related document from a fiber manufacturer. The simulated fiber has an inner core, outer core and a cladding. The strange thing about the document is, that in the ...
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Zero-dispersion wavelength

Please help me understanding the zero-dispersion wavelength in fibers. I found this wiki-article on the topic. Accordingly: "In a single-mode optical fiber, the zero-dispersion wavelength is the ...
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Maxwell's equation along a curve and Evolution of the polarization vector

So here is the setup: There is a coiled cylindrical wire. At each point on its axis, we define a tangent direction $\hat{t}(s)$, and a normal $\hat{n}(s)$ and binormal $\hat{b}(s)$, $s$ is a ...
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Collection efficiency of a fiber probe

Suppose we have a point source that emits photons isotropically, e.g. a small spot on a sample. Now we want to position an optical (single mode) fiber above this point source and collect the photons ...
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Propagation constant limits in optical fibers

I am trying to write a numerical routine to determine the propagation constant $\beta$ of an $n$-layered optical fiber. The routine is already mostly written, but I am running into problems regarding ...
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Why is fiber optic not affected by EMI?

If light is an electromagnetic wave, why is it not affected by electromagnetic interference? I've heard it's because fiber optic do not use electrical voltages. Can someone go deeper into the subject?
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Existence of $\mathrm{HE}_{11}$ mode in optical fibers for $v \to 0$

In a step-index optical fiber, the eigenvalue equation for the $\mathrm{HE}_{11}$ fundamental mode, under the weak guidance approximation, can be written as $$\frac{J'_n (u)}{u J_n (u)} = - \frac{K'_n ...
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Normalization of Phase Noise / RF Power Spectrum to 1 Hz RBW

I used a Rohde & Schwarz Phase Noise Analyzer to take some phase noise and RF spectrum measurements. All in all, I'm trying to compute the linewidth of a laser from a measurement. I cannot detail ...
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Fiber bragg grating simulation

I am trying to simulate a FBG with a windows based software. It would be great if someone suggest a proper software for me. Thanks all!
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Phase shifted Optical Fiber Bragg grating Response

As we know there is a narrow notch in the reflectance spectrum of a Phase shifted FBG. We have Bragg condition for reflected band of any uniform FBG. My question is that, does anyone know any relation ...
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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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How to identify the multimodes of an optical fiber?

I use Lumerical mode software to simulate a photonic crystal fiber of NANF type. The solver gives me a lot of modes (solutions). I want to know how to know if this fiber is a single mode fiber or ...
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Effective refractive index can be equal zero?

Can someone please explain the cases that the Effective refractive index $n$ on it can be equal zero? Does such a situation even exist? I am trying to solve an ordinary differential equation to find ...
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Effective refractive index and refractive index [duplicate]

Is there any relation connecting between the effective refractive index $N$ and the refractive index $n$ in waveguide?
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How to determine the effective index of the fundamental mode?

Suppose I have an optical fiber, the cladding refractive index n1 = 1.53 and the that of the core is n2 = 1.55. How to estimate the effective index? Is it right in between the two values?
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Creating Different Colours From A Pulsed Monochromatic Light Source

I am currently learning about fibre optic communications, which I understand use pulsed laser sources to generate a "bitstream" to send through the fibre using some form of pulse width ...
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Ray Power Equation for Bent Fiber Optics

I came across this equation while reading the book, Optical Waveguide Theory (by Snyder and Love) on page 182: where P(0) is the initial power from the straight fiber, R is the curvature radius, ρ is ...
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How can I bond a fiber to waveguide grating coupler?

I am wondering how can I bond a optical fiber to waveguide grating coupler. Should I use some type of glue? Or should I fix the fiber with a translation stage?
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Relationship between Optical Power output and luminous intensity

I have an LED with the following specification which I'm using for oxygen saturation measurements. Here the optical output power is given as >1.2mW for RED LED and >0.5mW for IR LED. How to ...
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Can a spectrometer detect interference pattern?

I am not sure whether this is the correct place to ask, otherwise, please point me to the appropriate platform. I have been reading about fibre optic interferometric sensors and notice that most ...
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Interference of Visible Light in Fiber Optics

I read this paper (the last sentence of Section 3.1). It is stated that in fiber optic interferometric sensors, the interference pattern cannot be detected if visible light is used because most fiber ...
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Fibre optic -physics

What is different between the lost of coupling and efficiency overall coupling ? I know both of them (power out/power in)e.g (5%) that means is 5% light transmission and 95% lost.
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Modal dispersion in optical fibers

I've got a couple of doubts regarding modal dispersion (with respect to optical fibers) What's the difference between intermodal and intramodal dispersion? How does intermodal dispersion affect ...
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Single mode fibre

I've got a couple of basic doubts about single-mode optical fibers - a) Why do single-mode fibers have lower attenuation than multimode fibers? b) Why do light rays in single-mode fibers travel in a ...
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Evaluating equation for cutoff condition of cylindrical dielectric waveguides

To determine the eigenvalues $u$, $w$ of a mode in a dielectric cylindrical waveguide (an optical fiber, for example), the following equation must be evaluated when $w \to 0$: $$\xi_1^2(u) - \xi_1(u) \...
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Why the optic axis of an crystal should has a proper direction; why it cannot be a single line? [closed]

In many books it is written that the optic axis of a crystal is a direction rather than a single line! I really cannot understand what is the necessity of the direction and why I cannot say that it ...
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Collimation issue with an DIY echelle spectrograph

I am trying to make an educational echelle spectrograph using easily available materials, basically in a cardboard box. An echelle grating (36 lines/mm) needs another prism to do a cross dispersion ...
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Why fiber optic cables looks colorful?

I wanted to know why fiber optics look green or blue, isn't it that it uses total internal reflection, so light shall remain in it? I think may be it's not monochromatic.
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What is the formal definition of Coupling efficiency

Does anyone knows the formal definition of Coupling efficiency? I have been reading the term in photonics devices and optics. I have been searching for it, but I could not find any. Thanks for the ...
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Is it possible to optimally transmit solar radiation by a system of multiple optical fibers?

As we all know, if an optical fiber is designed with the right material and properly bent, light can be transmitted along the fiber with very little attenuation. Figure 1 shows the interaction of ...
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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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Time independence of light in optical fibers

The propagation of light in optical fibers is governed by the equation $i\frac{\partial A}{\partial z} = \frac{\beta_2}{2}\frac{\partial^2A}{\partial T^2} - \gamma|A|^2A$ where $A(z,T)$ represents the ...
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Derivatives of the propagation constant in optical fibers

In many books on nonlinear fiber optics, the Taylor series expansion of the mode-propagation constant $\beta$ is performed about a frequency $\omega_0$ at which a pulse's spectrum is to be centered. $\...
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646 views

Numerical aperture of a multimode optical fibre

The refractive indices of the core and cladding of a multimode optical fiber are 1.62 and 1.52 respectively. Calculate its numerical aperture if the optical fiber is placed in (a) water (b) ice (c) ...
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Confinement factor for an optical fiber

I was reading the chapter about optical fibers of "Fiber - optic communication systems" and I have read this statement: The fraction of the power contained in the core is given by the ...
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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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Can a photon in a optic fiber interfere with itself destructively?

In Young double slit experiment the photons interfere with themselves destructively and constructively. So when there is an optic fiber with a mirror end the photon should return back and one can ...
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How do you combine two spatial modes of light into one spatial mode in optics?

Is there a lossless way to combine light coming from two different single photon sources into one spatial mode? Either free space of fiber would be fine. Let's assume the wavelength and polarization ...
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Is quantum network security an application of quantum entanglement?

If true, does it assume the link between the sending and receiving sides or servers acting on their behalf to be fully optical fiber physical layer or what practical approach is that heading towards?
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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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Etendue of the eye

I am tasked with calculating the Etendue of an eye with the given values: diameter of the pupil = 4 mm diameter of the retina (the active area) = 6 mm distance from the lens to the retina (b) = 20 ...
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Stark level manifold

In this figure from https://www.rp-photonics.com/effective_transition_cross_sections.html: When a high energy photon (920nm) is absorbed followed by phonon emission to lower energy level in the ...
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Ovalization of a pvc pipe under a weight

I'm not sure if this is the right place to ask this question, but it came up in one of my physics courses so here goes. I want to measure a weight using a Fiber Bragg Grating optic cable. Someone ...
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Min spot size for light collimated from an optical fiber?

We are currently setting up an experiment in which we need to pipe laser light from one optical table to another. One way we were thinking of doing this was by coupling into an optical fiber, running ...

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