Download optical/photonic bandwidth

OPTICAL/PHOTONIC BANDWIDTH
Definition: the width of some frequency or wavelength range
In photonics, the term bandwidth occurs with a variety of meanings:
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The bandwidth, or line width = width of the intensity spectrum of the output of
some light source—that is, a super luminescent source or a laser; the
bandwidth of ultra‒short pulses can be particularly large
The width of the frequency range which can be transmitted by some element,
e. g. an optical fiber
The gain bandwidth of an optical amplifier
the width of the range of some other phenomenon, such as a reflection, the
phase matching of a nonlinear process—→ phase-matching bandwidth—, or
some resonance
the maximum modulation frequency—or range of modulation frequencies—of
an optical modulator
Optical bandwidth values may be specified in terms of frequency or wavelength due
to the inverse relationship of frequency and wavelength. The conversion factor
between gigahertz and nanometres depends on the centre wavelength or frequency.
For converting a—small—wavelength interval into a frequency interval, the equation
can be used.
This shows that 1 nm is worth more gigahertz if the centre wavelength is shorter.
The term bandwidth is also often used for the data rate—that is, in Gigabytes per
seconds achieved in an optical communication system. Precisely, the data rate is
limited by the optical bandwidth, but is not really itself a bandwidth.
The optical bandwidth of a light source is strongly related to the temporal coherence,
characterized with the coherence time.
Both for passive resonators—that is, optical cavities and for the output of oscillators
—that is, lasers, the Q factor is the oscillation frequency divided by the bandwidth.
See also: time–bandwidth product, gain bandwidth, coherence time, transform limit,
Q factor, phase-matching bandwidth
Category: physical foundations