UNIVERSITY OF CALIFORNIA, LOS ANGELES
Department of Computer Science
CS M 171L & CS 117 Laboratory
Student name: _____________________
Laboratory Exercise 6
Dense Wavelength Division Multiplexing (DWDM)
In this lab you will examine the two channels of the 4-channel DWDM system
with 200GHz (or 400GHz) channel spacing (see Lecture note; ITU standard in
DWDM, Table 8-1). The signals optical carrier in the system is designed for
SONET hierarchy OC-24 with rate 1,244.160 Mbps using 1552.52 nm, 1554.13
nm, 1555.75 nm and 1557.36 nm wavelength light signals multiplexing.
In the lab you will unable to examine the multiplexing carrier hierarchy OC-24
because of restricted bandwidth of the oscilloscopes (200 MHz), but theoretical
concepts related to the multiplexing techniques you can check on hierarchies
OC-1 (51.840 Mbps) and OC-3 (155.520 Mbps).
In the experiment is recommended DWDM with 400GHz channel spacing
using light carriers with 1554.13 nm and 1557.36 nm wavelength.
You will investigate the simultaneous transmission of signals through a singlemode optical fiber. You will determine the characteristics of a Dense
Wavelength Division Multiplexing system and of the various components of the
DWDM system. For this purpose, you will measure the emitted light spectra
and power, determine the light power distribution in the system's splitters,
multiplexers and demultiplexers, measure channel separation and cross-talk in
the system. You will investigate DWDM system properties.
The main goals for experiments are:
1. Determine the characteristics of the dense wavelength division
multiplexing communication components.
2. Determine communication system power and bandwidth budgets.
3. Determine the information capacity of a backbone fiber optic cable.
1
For this purpose:
a. Measure the emitted light power of the laser transmitters.
b. Measure the power distribution in the wavelength dependent couplers
(Multiplexer/Demultiplexer),
c. Measure channel separation and crosstalk of the system.
2
Exercise #6: Theory
(Include with protocol)
In the data communications, the two techniques are available for multiplexing:
Time Division Multiplexing (TDM) and Wavelength Division Multiplexing
(WDM). TDM divides a high-bandwidth transmitted signal into time slots,
where each time slot carries a different low-bandwidth signal.
1)
How does WDM work and what are its advantages over the TDM?
2)
What are the components of a DWDM network? Briefly, what are their
functions?
3
Exercise #6: Theory (continued)
(Include with protocol)
A wavelength dependent coupler can be used as a multiplexer (to combine light
of different wavelength onto a single fiber), or as a demultiplexer (to split
combined light back into the component signals).
3)
For a wavelength dependent coupler, how do you calculate:
a)
Channel separation?
b)
crosstalk?
a)
b)
4)
What is the complete formula to calculate the power budget of a Dense
WDM communication link? Include all necessary component losses assuming
two wavelength dependent couplers are used for multiplexing and
demultiplexing.
4
Exercise #6: Theory (continued)
(Include with protocol)
The maximum channel capacity of each channel of the DWDM system can be
determined from Shannon’s formula.
5)
a) What are the formulae to calculate maximum channel capacity?
b) What is system bandwidth if you know system components rise times?
c) What is 4 channel DWDM system channel capacity in bits per second:
a)
b)
c)
5