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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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Field propagation in metamaterial based optical fibres?

We have an optical fibre having HMM cladding ( $\mu=1$ and have a permittivity tensor with one component different in sign than others) and a core having permittivity equal to one. How will light ...
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When building a fiber optic interferometer what methods are used to reduce microphonic effects?

When building a fiber optic interferometer what methods are used to reduce microphonic effects? I'm familiar with a few methods such as: enclosing the interferometer under a sound dampening cover, ...
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Are there any commercially made optical fibers which are made specifically to have very low microphonic properties for application in interferometry

Are there any commercially made optical fibers which are made specifically to have very low microphonic properties for applications in interferometry. While building a fiber optic interferometer I ...
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Why laser output power fluctuates after passing through two 1x2 fiber optic couplers?

When laser source is launched into two 1x2 50/50 fiber optic couplers connected as below the output power constantly fluctuates in range of 70 uW. The fluctuation happen roughly one to two times per ...
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Mode propagation constant in optical fibers

$$\beta = k \sqrt{n_1^2 - \left(\frac{m\lambda}{2a}\right)^2}$$ where $m$ is one of the possible modes (from $0$ to $M-1$ where $M$ is no. of guided modes) and $a$ is the diameter of the optical fiber....
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Coupling a single mode laser to multimode fibre - does this reduce coherance?

If I have a single mode laser coupled to a multimode fibre with imperfect overlap between the laser mode and the fibre core, the light will propagate in several LP modes. In this case, does the light ...
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Why does a larger diameter optical fiber reduce the resolution of a spectrometer

I am working in an experiment in optics, measuring transmittance. Light is shone on a sample, collected by an integrating sphere, the output of which is coupled to a spectrometer through an optical ...
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Inconvenience of speed of light in optic fiber

As far as I'm concerned, optic fiber is great in order to transport information quickly using light. Since light needs to undergo total internal reflection every single time it hits the walls of the ...
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Fraunhofer temporal far-field condition for dispersive Fourier transform (DFT) technique

I am trying to understand the dispersive Fourier transform (DFT) technique for spectral characterization of pulses. In the literature, I found this far-field condition from Fraunhofer approximation in ...
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Why fiber optic Sagnac interferometers don't produce multiple interference fringes

I have seen a few Sagnac fiber optic interferometers however, those that I've seen don't produce multiple fringes but rather just one luminant dot with varying intensity. Even if a beam expander is ...
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What is the meaning of a fiber cutoff wavelength when given as a range?

Many polarization maintaining fibers (for example Corning PM 1550) have a cutoff wavelength specified as a range (for example 1300-1440nm). What is the meaning of this range from the physics point of ...
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How to eliminate polarization mismatch in the Michelson interferometer based on single-mode optical fiber?

We are developing a mobile system for optical coherence tomography based on fiber optic Michelson interferometer. We are facing a problem of chenging the polarization during a movement of the fiber. ...
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Why some laser diodes have angled window?

Why some laser diodes have angled window? Here is an example
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Can Sagnac effect be observed in coiled, rotating electrical cables conducting electric signals?

Can Sagnac effect be observed in coiled, rotating electrical cables conducting electric signals, in a similar way to that observed in coiled, rotating optical fibers? And if so then who demonstrated ...
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Will light of 405nm wavelength behave in a single mode (SM) fiber , in multimode manner?

Since the wavelength of 405nm is substantially shorter than the wavelengths of 1310-1550nm, and since the ratio of the diameter of a single mode fiber core to the wavelength, at 405nm, is several ...
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What is the connection between Ray (Geometric) optics and Electromagnetic theory optics in fiber optics?

I am currently reading about fiber optics and wave propagation in fiber optics and encountered the following part of Gerd Keiser's Book : according to the diagram shown, its a general case when the ...
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Understanding the use of Group Velocity Dispersion Optics

I am a bit confused on the topic of GVD. Most information I read on the topic tells me something like this: "GVD means that the group velocity will be different for different wavelengths in the ...
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How do optical fibres work with high critical angles?

The critical angle is given by: c = arcsin(n2 - n1) For a typical optical fibre, it says on the web that refractive index (n2) for cladding is higher than that of the glass core (n1) but it's only a ...
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Why does an optical fibre employ total internal reflection instead of just reflection? [duplicate]

I learnt that an optic fibre uses the concept of total internal reflection (TIR) to transmit data at high speed, but why do they not use just simple mirrors instead of using refractive medium and ...
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Waveguide allowed modes | Transverse resonance condition

Consider a planar waveguide for example. The guiding index is $n_f$, and the cover and substrate indices are $n_c$ and $n_s$ respectively. Let the waveguide propagate along z, and have a height $h$ in ...
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Effective Refractive index of a mode less than that of the cladding refractive index?

Can the effective refractive index be less than the cladding if the waveguide width is very small. For example for the case of a ~100 nm waveguide.
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In which part of the Sagnac fiber optic setup will the light undergo the most intense interference?

Let's assume we have a Sagnac setup consisting of a 1310nm laser, 2X2 coupler injecting light into two opposite ends of a single mode fiber loop, and a photodiode receiving the light from both ends of ...
Jimski's user avatar
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Will light, from two different (but identical) lasers injected into one end of a long fiber, come out form the other end with the same polarization?

Two beams of light from two lasers of the same type, with the same wavelength but different polarization, are coupled with 2X1 coupler into a 100m long single mode regular fiber. Each laser can be ...
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Laser beam quality problem: The laser beam showed very different during using the CCD testing directly or using the M2 measurment machine

Recently, we encountered a problem with the laser beam profile characterization, where two testing methods showed two distinct results of the beam profile of the same laser system. When we used a CCD ...
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Problem measuring local reflectance through objective lens

Measuring the reflectance of copper substrates using only reflection probes gives an expected reflectance (orange plot). But when an objective lens is used to focus the incident light, I can see the ...
jlim1234's user avatar
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How to collapse telescope image cone into an optical fiber?

I have an application where a telescope will be receiving light from a laser source. I would like to couple the output of the telescope, which is the image cone, into an optical fiber. Does anyone ...
Anthony Knighton's user avatar
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How does an endoscope form the image?

I am trying to do ray tracing for an endoscope, but I don't see how it could form a sharp image that could be viewed at the eyepiece. In the diagram the box in the middle is the "fiber", but ...
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Dependency of attenuation in optic fibers on wavelength of light

I have read and heard that scattering, and attenuation in general increase with frequency. However, in an experiment we did as a part of our course, we found that attenuation constant for light of ...
Eternal Learner's user avatar
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How does MEMS low insertion loss fiber optic switch work? [closed]

I'm currently looking for a low insertion loss fiber optic switch to be able to change the light source of a spectrometer. Since this will be used in harsh conditions, I was hoping to find one with no ...
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How does the change in cavity length effect the interferometric frequency of a Fabry Perot cavity?

I'm working with FBG-based Fabry Perot interferometers, considering three FBGs in series to create 2 FP cavities. I'm confused about the following two things and cannot seem to get clear answers from ...
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Optic Fiber Gyroscope Within Its Frame

I understand why the fiber optic gyroscope works as well the calculations for the time discrepancy between the beams travel time, but only as observed from out side the ring, "watching" it ...
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Why can't a wave in the cladding of a waveguide phase match to a guided wave?

What is the physical reason behind why a wave in the cladding of a waveguide cannot phase match to a guided wave? I read that the most common solutions to coupling waves to a guided wave is to use ...
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Veracity of light field propagation simulation method (Combined Split-step Fourier and BPM)

When trying to simulate light propagation in three spatial dimensions and one temporal dimension I encountered a method given in this thesis. Here (on page 32), it is proposed to do a BPM within a ...
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SRS is reduced by increasing the bandwidth of the OC in high power fiber lasers generally. What happens if the bandwidth is increased too much?

Several articles suggest, in a MOPA configuration high power fiber laser, the SRS can be mitigated by increasing the bandwidth of the OC FBG. How to determine the optimized bandwidth of such FBG? Does ...
Chat0924's user avatar
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How to expand light from fibre optics?

I am building a spectrophotometer for my robotics science club. I am using fibre optics cable to transport emission signal from the sample to spectrometer,next it is projected on the refelctive ...
Alek Przybyłkowski's user avatar
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The output laser power of fiber amplifier fluctuates up and down with the increase of pump power

I was engaged in the research of 2um thulium-doped fiber laser. During the experiment, I found that when the oscillator seed light was injected into the amplifier stage for amplification, the output ...
wesprit's user avatar
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Where can I find the derivation of $V$ number (fiberoptics) from analysis of the Maxwell’s equation?

This is from Optics (5th ed.) by Hecht, p. 209. I was studying fiberoptics and this parameter called $V$-number came up. Also there is another term called the normalized propagation constant, b which ...
AYM Shahriar Rahman's user avatar
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Does carriers lifetime introduce any dispersion to a LED diode emitter?

I'm asked to calculate the maximum chromatic dispersion coefficient D for which an optical cable is able to transmit at a 100 Mbps bitrate working in SMS. The maximum bitrate is given by B≤1/2∆τ, ...
Ketterle's user avatar
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Difference between seed and pump in chirped pulse amplifier

What is the difference between to seed an optical amplifier (such as Chirped Pulse Amplifier) and to pump it with a laser source?
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Can a fibre preserve the shape of the light being transported through it?

Can some fibres retain the shape of the light being transported through them? If I emit radiation towards a sample (in the shape of an "S") and this is reflected back into a fibre, will the ...
user7077252's user avatar
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Total Energy of an Asymetric 3x3 Coupler

In our experiments, we are using a 3×3 fibre couplers with light as part of an interferometer-setup. This coupler isn't symmetric; it's phase relation of every output is unequal to 120° and the ...
bilaljo's user avatar
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What are some of the best materials to use for building a fiber laser safety enclosure of 1060nm - 1085nm?

I have gotten a 30W JPT-LP Litemarker Fiber Laser which has a wavelength range of 1060nm - 1085nm. Before even thinking about using it, i want to build an enclosure for it to increase the level of ...
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Understanding the Light propagation through multimode fibers

I'd appreciate it if anyone could help me clarify the theory behind this. I am playing with this code found on Github, https://github.com/wavefrontshaping/pyMMF to simulate the light propagation in ...
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Question about fiber to chip coupling in silicon photonics

I asked a similar question earlier (How is the fiber alignment done in pluggable optical transceiver module (e.g., QSFP-DD)?), but few things are still not clear to me, so I'm posting another one here....
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How is the fiber alignment done in pluggable optical transceiver module (e.g., QSFP-DD)?

I recently started learning silicon photonics. After reading a few books, I understand that a single-mode fiber (especially non-polarization-maintaining fiber) supports two degenerate guided modes. ...
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How to find integrated power of a optical signal using wavelength amplitude graph?

I have a wavelength amplitude graph as shown below. This a screenshot captured from optical spectrum analyzer. From the image I can see what is the power at each wavelength. But, I would like to ...
Kishore Kumar S's user avatar
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What is the best way to couple diffuse light into a single-mode fiber?

I understand the requisites to couple a laser beam into a single-mode fiber, including mode-field diameter and numerical aperture. However, when trying to couple diffuse light into a single-mode fiber,...
Pablo Fernández Esteberena's user avatar
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Choosing the right lenses for optical fiber

I need to measure optical emission of lanthanides when excited with X-ray, so I have to problems, difficult to align (X-ray radiation) and poor signal. In this case I need to choose some lenses to ...
3u63n10's user avatar
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How to achieve uniform gaussian profile? Beam profile has grainy/multimode pattern, EO says it's due to different emissivity of each phosphor atom

I'm required to make a jig that measures the divergence angle of a collimated beam. The setup is straightforward as shown below. The single-mode fiber optic cable, collimator & NIR camera are the ...
Hazman's user avatar
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How to choose the right lens for projecting a certain area to a fiber optic

I am looking for a lens to magnify a certain area so that it can be captured by a fiber optic. Specifically, I want the fiber optic to capture a certain object, which requires it to be at a distance ...
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