Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [photonics]

37 questions
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3 answers

How is 255 Tbit/s processed in optical fiber communication?

I have never understood how the new record breaking data transfer speeds are achieved in terms of converting from/to electrical and optical signals. Suppose we have 255 Tbits of data and we want to transfer it in one second. (This is a real world…
stevie
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4 answers

Why do we need nonlinear electronics for computing?

When I read about photonics, I always see that they can be used for linear transformations (just matrix multiplications), and that this is a limitation that makes them unsuitable for building a complete photonic microprocessor. Why are linear…
egemen404
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Why is the light emitted by the LED not of a single wavelength but consists of a narrow range of wavelength instead? Spectral linewidth change?

I do understand that the wavelength of the lights depends on the energy gap of the semiconductor, but why does it consist of a narrow range instead of a fixed value? is it because during recombination the photons have random phases? Also, how does…
Meep
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11
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6 answers

LED as power generator

As many of you probably know, a normal light emitting diode, while very handy as a cheap and ubiquitous indicator, can double as a power generator. The mechanism is the same that is exploited in photovoltaic cells, aka solar panels. When an LED is…
Vladimir Cravero
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9
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1 answer

Photon count with ADC, am I doing it right?

I have this LED and I want to characterize this photodiode. The LED should produce light of 370 nm, but I measured it and it is around 358 nm, and at that wavelength the quantum efficiency (\$\eta\$) of the photodiode is 0.5141. Now, I feed the…
Fernando Franco Félix
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4
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2 answers

Can I simply adjust the output power of these laser diodes to meet my specifications? If so, then what are the consequences of doing such a thing?

I need a CW laser diode, with an integrated photodiode, with wavelength around 800nm and power 1-1.5mW. Although I didn't find anything that exactly matching my specifications, I did find this from Thorlabs and this from Roithner Lasertechnik.…
The Pointer
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Charge transfer in CCD

I have a basic doubt about charge transfer between pixels of a CCD. Let's consider this animation (picture taken from wikipedia): A precise time sequence of applied voltages between gates and bulk allows to move the charge between a pixel…
Kinka-Byo
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3
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Building laser doppler vibrometer

I'm interested in building my own laser doppler vibrometer using laser diodes. The reason I mention laser diodes is because (1) I want it to be cheap and (2) I want to incorporate it into robotics projects. However, I'm unsure if it's possible to…
The Pointer
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How does the gate of MOSFET pass through an oxide layer?

I must be missing sone fundamental law of electronics. Why does the gate voltage of a MOSFET travel into the main “body”. Aren’t oxides insulators? If so, how do the electrons pass into the body of the MOSFET? My guess: The gate creates an…
gbe
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Biasing network for phototubes and photomultipliers

I have some doubts about typical biasing network for vacuum phototubes and photomultipliers. Precisely, let's start by a simple photocathode. I have seen some biasing network like this one: In this circuit, which is the precise role of \$R_L\$?…
Kinka-Byo
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Can linearity of photoreceptor be improved by calibration?

I am trying to determine if equipment I already have can be used to take a reading in mcd/m2, for a quality control test. I have a sensor which meets all the requirements listed in the standard test method except that it has a linearity error of <1%…
str3r
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Can we send multiple signals in same core at the same time in the fiber optics? If yes, how?

I am curious to know how exactly does the fiber optics works. I understand the basic concepts of the fiber optics communications but am curious to know if there is a way to send multiple signals in same core at the same time in the fiber optics? How…
dr3patel
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What does the term "boresight", and what do the phrases "boresight adjustment" or "boresight calibration", mean in the context of laser scanning?

I have been studying the laser scanning literature. In doing so, I often come across the term "boresight", and the phrases "boresight adjustment" or "boresight calibration". For example, see this paper. However, I have not seen any explanation of…
The Pointer
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Setup for fringe contrast measurement

I am currently reading the Fringe Contrast section of this document. This section says the following: Be sure to use a DC-coupled detector when measuring fringe contrast. Adjust the interferometer alignment to maximize the fringe contrast in the…
The Pointer
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Further Understanding Optical Parameter of Image Sensors for Use In Spectroscopy

I’m attempting to build a spectrometer and I’m having difficulty assessing the performance of a particular sensor. I am a novice and other posts on this forum have helped me greatly but I still haven’t been able to arrive at an answer that makes…
user3338262
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