Page 215 - Introduction to Information Optics

200 3. Communication with Optics

3.1.3 Calculate the maximum allowed thickness of the active layer of single
transversal mode operation of a 1.3 /im semiconductor laser. Assume that
«i = 3.5 and n 2 = 3.2.
3.14 Compute the grating space for an InGaAsP DFB laser diode operating
at 1.3 /mi. Give results for both the first- and second-order diffraction.
3.15 Plot the cutoff wavelength (in jum) as a function of the bandgap energy
(in eV) for a PIN photodiode for wavelengths from 0.4 to 1.6 nm.
3.16 Compute the responsivity of a Si photodiode operating at 1.55 /on and
having a quantum efficiency of 0.7.
3.17 In Prob. 3.16, how much optical power is needed by this detector to
produce 20 nA photo current?
3.18 Consider a silicon PIN photodiode with responsivity jR = 0.65 A/W,
R L — 1000 W, operating at 850 nm and at room temperature (i.e., T —
300 K). If the incident optical power is 500 nW and the bandwidth is 100
MHz,
(a) Compute the signal current.
(b) Compute the shot noise current.
(c) Compute the thermal noise current.
(d) Compute the signal-to-noise ratio (in dB).
3.19 Sketch a four-channel, full-duplex WDM network. Indicate the location
of the transmitters, receivers, multiplexers/demultiplexers, and so on.
3.20 Describe the DWDM optics networks.
3.21 Describe how to test the bit error ratio of optics networks.