TEST 8

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)

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)