Electronic And Photonic Devices

Step 1: Historical background of quantum well lasers.
Quantum well lasers were initially fabricated using GaAs/AlGaAs material systems. This material system was widely used for semiconductor lasers, including those based on quantum well structures.

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In the first window of optical fibre communication, light sources such as GaAlAs (Gallium Aluminium Arsenide) are commonly used. GaAlAs is a semiconductor material that emits light in the near-infrared region, which is ideal for transmission in the first window of optical fibre, typically around 850 nm.
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Optical fibres transmit data using light, typically in the infrared or visible spectrum. The most common transmission frequencies in optical fibre communication systems are in the range of Hz (near-infrared). This frequency is ideal for transmitting data through optical fibres due to the low loss at these frequencies.
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In an optical fibre, the core has a higher refractive index than the cladding. This difference in refractive indices causes total internal reflection, which allows light to be guided through the core of the fibre. The cladding has a lower refractive index to ensure that light remains confined within the core.
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Attenuation in optical fibres is typically expressed in decibels per meter (dB/m). This represents the loss of signal strength per unit length as the signal travels through the fibre.
While other units such as dB/km and dB/mm can be used in different contexts, dB/m is the most commonly used unit in practical applications.
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Step 1: Formula.
Å.

Step 2: Substitute.
Å, which is closest to 6533 Å.

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Fibre optic sensors are generally classified into intensity-modulated, phase-sensitive, and diffraction-based sensors. "Conducting sensors" is not a classification commonly used for fibre optic sensors, making it the incorrect option.
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