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Ch 39: Wave Functions and Uncertainty
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Non è quello che usi tu?Cambia libro di testo
Capitolo 39, Problema 19

A 1.5-μm-wavelength laser pulse is transmitted through a 2.0-GHz-bandwidth optical fiber. How many oscillations are in the shortest-duration laser pulse that can travel through the fiber?

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Determine the relationship between the bandwidth (Δf) and the time duration (Δt) of the pulse using the time-bandwidth product. For a Gaussian pulse, the time-bandwidth product is approximately Δt * Δf ≈ 0.44. Rearrange this to find the shortest pulse duration: Δt = 0.44 / Δf.
Substitute the given bandwidth of the optical fiber, Δf = 2.0 GHz (2.0 × 10⁹ Hz), into the equation for Δt to calculate the shortest pulse duration.
Calculate the period of one oscillation of the laser light using the relationship T = 1 / f, where f is the frequency of the laser. The frequency of the laser can be found using the speed of light equation: f = c / λ, where c = 3.0 × 10⁸ m/s (speed of light) and λ = 1.5 μm (1.5 × 10⁻⁶ m).
Substitute the calculated frequency of the laser into the equation T = 1 / f to find the period of one oscillation.
Determine the number of oscillations in the shortest-duration pulse by dividing the pulse duration (Δt) by the period of one oscillation (T): Number of oscillations = Δt / T.

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Wavelength and Frequency

Wavelength and frequency are inversely related properties of waves. The wavelength (λ) is the distance between successive peaks of a wave, while frequency (f) is the number of oscillations per second, measured in hertz (Hz). For light, the speed of light (c) relates these two by the equation c = λf. Understanding this relationship is crucial for determining the number of oscillations in a laser pulse.
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Pulse Duration

Pulse duration refers to the time interval during which a pulse is active or has significant amplitude. In the context of laser pulses, shorter durations correspond to higher frequencies of oscillation. The duration of a pulse can be estimated using the bandwidth of the optical fiber, as a larger bandwidth allows for shorter pulse durations, which is essential for calculating the number of oscillations in the pulse.
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Bandwidth and Information Transmission

Bandwidth is the range of frequencies that a communication channel can transmit, measured in hertz. In optical fibers, a higher bandwidth allows for the transmission of more data and shorter pulse durations. The relationship between bandwidth and pulse duration is given by the time-bandwidth product, which indicates that a pulse's duration is inversely proportional to the bandwidth, thus affecting the number of oscillations in the pulse.
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