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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How does a photodetector work more specifically?

I’m studying how fiber-optic communication works. To transmit a signal, you need a transmitter that converts electrical impulses into luminous and a photodetector that performs the reverse operation. ...
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What are the difference between step-index and graded index fiber?

I was starting to study optical fibers and I came to the chapter: Classifications of optical fibers. Here I read about singlemode and multimode fibers, regarding the latter he explained the difference ...
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How about optical fiber without cladding and directly coated?

How about optical fiber without cladding and directly coated? I have got some answers from here, but how about optical fiber without cladding and directly coated? and the coating material have a ...
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How can I collimate a laser beam of 100 wavelengths in vacuum?

Before collimating, the beam will have diverged a bit to a radius of 5cm, the range of the wavelengths is 1400-1600nm and I don't want to lose more than 30% of initial power. I'm asking in general how ...
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How to calculate the Full Width at Half-Power (FWHP) at the output of two SMF and DCF connected in cascade

Assuming a Gaussian pulse with a wavelength $\lambda$ and $FWHP_i$ , a SMF with dispersion $D_{SMF}$ and length $L_{SMF}$, a DCF with dispersion $D_{DCF}$ and length $L_{DCF}$ How can I calculate the ...
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Data transmission through optical fiber and copper wire

I read the following in one reference: A copper wire (twisted pair), the link traditionally associated with low bit rate transmission, is still in use in the modern data centers transmitting data at ...
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Working of the optical fibre

I read about the mechanism of an optical fibre. It works on the basis of total internal reflection. But for total internal reflection it is necessary that the incident angle is more than the critical ...
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Wavelength-dependence of optical elements in integrated photonic circuits

I am interested in integrated photonic circuits or silicon photonic circuits. In the long run, I would like to analyze these circuits using a rigorous and analytical mathematical approach, taking the ...
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In fiber wave guide we only consider transverse (TM,TE,EH) modes of laser. Why not we consider londitudenal modes?

Laser beam guiding through fiber.
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How to find peak power at 1550nm using an optical meter?

I have a setup of tunable laser source at 1550nm connected to a spectrometer(Can't publish the name of spectrometer). The spectrometer has a range of 1510-1595 nm. The graph shows wavelength vs ...
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How to implement a very precise polarizer inside a fiber-based setup?

A tricky question: I need to use polarizers with a ~5 arcmin precision inside a PM fiber-based system. What are some (hopefully cost-effective) ways of achieving this? The setup works with linear ...
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How is certain area of waveguide becomes visible to user?

I was reading an article and came across this image As shown, image becomes visible to eye after reaching a specific area of the glass. But how does it work? Why is it being reflected at such a weird ...
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Why dielectric waveguides support hybrid modes and metallic waveguides don't?

Can anyone explain me qualitatively, why dielectric waveguides (core and infinite cladding) support hybrid modes ($E_z$ and $H_z$ components in the guided wave) while metallic waveguides cannot. I am ...
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Field at exactly cutoff of optical fiber

Can anyone give a clear qualitative explanation on what is the field inside and outside an optical fiber at EXACTLY cutoff?
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Why is a Small Coherence Length Desired for Fiber Optic Gyroscopes?

For interferometric measurements based on the Sagnac effect, typically a light source is injected into counter-propagating paths of a fiber optic coil. The rotation of this coil of fiber optic cable ...
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How fast, based on the laws of physics can the Internet be? [closed]

Assuming the actual physics, optics, signal processing and similar, how fast can we increase the 'speed' of the Internet? I know the limit would be $$v \le c,$$ but are there some other limits: ...
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Experimental detection of Anderson localization of light in 3D vs 2D

I have a question about the experimental realization of Anderson localization of light. I am a theorist, and have not worked much in optics, so please bear with me. Anderson localization of light in ...
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Drawing digital signal from analog signal

I was doing a question related to analogue to digital conversion. Here's the question, Draw the digital signal corresponding to the analogue signal given below. Assume that the system has a bit rate ...
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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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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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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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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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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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2 votes
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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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