Page 732 - Introduction to Information Optics

716 12. Networking with Optics

BPF suppresses the unwanted channel to 25 dB down the wanted
channel, in the case of two-channel DWDM, how much lower should
every unwanted channel be relative to the wanted channel if channel
counts increase to 80?
12.5 Chromatic dispersion in optical fiber limits the bandwidth-distance
product of a system. For 140 km of single mode fiber having 17
ps/nrn/km chromatic dispersion, assuming the laser source has 10 nm
FWHM (full width at half maxim) and system 20% bandwidth effi-
ciency, what is the maximum dispersion-limited data rate of the system?
12.6 Find the numerical steady-state solutions for amplifier rate equations
(12.1) to (12.5), assuming 20 meter Erbium fiber length, 90 rnW pump
power at 980 nm, and —10 dBm input signal at 1550 nm.
12.7 An optical amplifier produces 2.00 //W amplified spontaneous emission
(N EDFA), for a signal wavelength of 1550 nm and a bandwidth of 0.5 nm.
What is the corresponding noise figure?
12.8 Draw a configuration of a transmit transponder having a 1310-nm
SONET interface, SONET 3R, and FEC, as well as asynchronous 2R
capabilities. Describe in detail the functions of each block.
12.9 Refer to Exercise 12.6. Draw the configuration of the corresponding
receiver transponder. Describe in detail the functions of each block.
12.10 Modern optical communication systems use the wavelength range 1300
1650 nm in a silica fiber for signal transmission. If the channel spacing
is 12,5 GHz, how many channels can be carried by a single fiber?
12.11 Typically, optical signal experiences 0.8 dB insertion loss when it passes
through a commercial dielectric thin-film filter, and 0.4 dB insertion loss
when it is reflected by the same filter. Estimate the maximum insertion
loss of the eight-channel DWDM demultiplexer in Fig. 12.8.
12.12 Derive the transmission expression of a chain of Mach-Zehnder inter-
ferometers acting as a filter.
12.13 Demonstrate how the Mach-Zehnder interferometer is used as a demul-
tiplexer and show the design schematic of a 1 x 4 demultiplexer.
12.14 Design a 32-channel, 50-GHz channel-spacing DWDM demultiplexer
based on the knowledge learned from Sec. 12.2.3. There may be multiple
solutions; compare the technical merit and economy of different sol-
utions.
12.15 Estimate the threshold power of stimulated Brillouin scattering in
conventional single mode fiber.
12.16 Explain why self-phase modulation in optical fiber causes the peak of an
optical pulse to travel slower in the fiber than the wings.
12.17 Two wavelengths, at frequency /, and / 2, can also interact through
optical fiber to generate four wave-mixing sidebands. Derive the ex-
pression of the frequencies of the sidebands.