EE466 Optical Engineering
Homework #5
1. Calculate the dispersion limited length for a data rate of 100Mbps for the following
cases:
a. A graded index multi-mode optical fiber (use the spec sheet posted on the
class web site) with a single longitudinal mode Fabry-Perot laser with a
linewidth of λ=2nm and a center wavelength of =1550nm.
b. A graded index multi-mode optical fiber (use the spec sheet posted on the
class web site) with a DFB laser with a linewidth of f=10MHz and a center
wavelength of =1550nm.
c. An SMF28 single mode fiber (use the spec sheet posted on the class web site)
with a single longitudinal mode Fabry-Perot laser with a linewidth of λ=2nm
and a center wavelength of =1550nm.
d. An SMF28 single mode fiber (use the spec sheet posted on the class web site)
with a DFB laser that has a spectral width of f=10MHz and a center
wavelength of =1550nm.
2. An optical communications link consists of SMF28 optical fiber, a laser with power
of Pt=15mW and a wavelength of =1550nm, and a receiver that requires Prec>21dBm. The connection between the laser and the fiber is 75%, and the connection
from the fiber to the detector is 90%. The splices between sections of optical fiber
have a loss of 0.2dB and the fiber comes in sections that are 2km long. What is the
attenuation limited length?
3. P24.1-1 (2nd edition of the book)
For Problems 4-5
On the web page there are the following specification sheets (2) types of fiber, (4) lasers,
and (2) detectors. Assume that there is no loss associated with connection between
components and no loss associate with fusion splicing. No wave division multiplexing is
to be used. Assume that the detector sensitivity is independent of bit rate. Be sure to
calculate both the dispersion and attenuation limits. Be sure to consider both laser
linewidth and modulation linewidths.
4. Design a system with the longest distance. What is the maximum bit rate of this
system?
5. The alignment cost of the system is much less when using multimode optical fiber.
a. What is the maximum propagation distance if the pin photodetector and the
Coaxial DFB-LD Module laser are used with the multimode optical fiber?
b. What is the maximum bit rate of this system?
c. What is the (bit rate)*(distance) product of this system?
d. If the link needs to only be L=100m, what is the maximum bit rate?