1. TEST 8

2. 8. EMITTERS AND PDs Optical sources emit light by means of
lanterns
photonic absorption
incandescence
electronic excitation
The operating wavelength of an optical source is mainly determined by
the amount of pumping
the band gap energy
the width of the active region (depletion region)
Heisenberg’s Uncertainty Principle
Which one of the following features does NOT apply to LEDs?
Coherent emission
Wide spectrum
Low cost
Low power
In an operating laser diode, which one of the following conditions does NOT apply?
Population inversion
Stimulated emission
Pumping
Incoherent emission
The spectral width of an optical source is measured by means of FWHM parameter. What does FWHM stand for?
In a photodetector, the trade-off for the active region establishes that
a narrow region is faster but has wavelength instability
a wider region is slower but absorbs more photons
a wider region is faster but cheaper
a wider region is slower but unreliable
PESO
- Menos de la décima parte que coaxial
INCONVENIENTES
- No es capaz de llevar la alimentación (como hace el coaxial)

3. 8. EMITTERS AND PDs
Data of a photodetector: Qantum efficiency η = 0.8. Electrical charge of an electron e- = 1.6·10–19 C. Operation wavelength λ = 1550 nm. Planck’s constant h = 6.63·10–34 J·s. Speed of light in vacuum c = 3·108 m/s. Calculate the responsivity of the device.
The maximum responsivity of a PD is reached when the photon’s energy is:
Smaller than the energy gap
Exactly equal to the energy gap
Slightly greater than the energy gap
Much greater than the energy gap
Can a PD have a responsivity greater than 1 A/W?
Data of an APD: Responsivity R = 0.9 A/W. Multiplication factor M = 50 times. Optical received power po = 1 μW. Calculate the total photocurrent.
Data of a PD: Dark current ID = 1 nA. Calculate the sensitivity (dBm).
In a certain photodetector, when the received power is –30 dBm, BER is 10–6. Then, if the power received is –25 dBm, BER will be
smaller than 10–6
equal to 10–6
higher than 10–6
PESO
- Menos de la décima parte que coaxial
INCONVENIENTES
- No es capaz de llevar la alimentación (como hace el coaxial)