Dense Wavelength Division Multiplexing DWDM

1
Dense Wavelength Division Multiplexing (DWDM)

• This report was prepared for Professor L.
  Orozco-Barbosa in partial fulfillment of the
  requirements for the course CEG 4183
• Luc Pelletier 1820890 -- Miguel Pinard 1486555
• March.12.2002

2
What is DWDM ?

• technology that uses fiber-optics transmission
  techniques that employ light wavelengths to
  transmit data

Figure 1
Source http//www.iec.org/online/tutorials/dwdm/t
opic03.html
3
What is DWDM ?

• Allows providers to offer the following services
  as IP data over ATM or voice over SONET (or SDH)
• Video
• Multimedia
• E-mail

4
How does DWDM work ?

• Flexibility and Expansion Capabilities
• Assigns each incoming signal to a specific
  frequency (i.e. wavelength, ?)
• Multiplexes resulting signals out onto a single
  fiber
• Independent of format and / or bit rate allows
  easy integration into existing networks

5
How does DWDM work ?
Figure 2
Source http//www.iec.org/online/tutorials/dwdm/t
opic03.html
6
Technology

• Optical amplifiers allow for the high-speed,
  high-volume transmission.
• amplifiers are optimized to work with existing
  fibers
• they boost lightwave signals without having to
  convert to electrical form
• this type of amplification could potentially
  handle a terabit of information.

7
DWDM Advantages

• Capacity Expansion
• Grow-as-you-go infrastructures can be used
• Capability to add current and next-generation TDM
  systems for expansion

8
DWDM Advantages

• DWDM vs. Repeater-Based applications
• DWDMs optical amplifiers benefit long-distance
  providers
• Improved efficiency with fewer regenerators over
  long distances.
• Ex 16 channel DWDM system reduces the number of
  amplifiers at each regenerator

9
DWDM Advantages (example)
Figure 3
Source http//www.itpapers.com/cgi/PViewIT.pl?sc
id47paperid8042
10
DWDM Advantages (example)
Figure 4
Source http//moon.pr.erau.edu/pettitl/DWDM2.htm
A3
11
Applications

• Used in long-distance telecommunications where
  point-to-point or fiber optics rings are already
  in place.
• 40 Gb/sec. protected ring using only two fibers.

Figure 5
Source http//www.itpapers.com/cgi/PSummaryIT.pl?
paperid8042scid47
12
Applications

• Network wholesalers can take advantage of DWDM to
  lease capacity instead of an entire fiber.
• This is due to the fact that
• Multiple channels (up to 16) are available on one
  fiber.
• DWDM is transparent to various bit rates and
  protocols.

13
Applications

• DWDM is also used to extend the lifetime of
  submarine cables.
• Considerably cheaper to use DWDM to augment the
  capacity of the cable than to install more cables.

14
Future Trends

• Telecommunications industry changes rapidly and
  is unpredictable.
• DWDM has the ability to adapt itself to new
  technologies.
• Ex. DWDM can transmit data that uses different
  protocols on the same fiber.

15
Future Trends

• There is still a lot of room for improvements in
  transmission capacity.
• Solutions currently provide 16 channels (40
  Gb/sec.) but demos have been made with over 100
  channels (1 Tb/sec).
• Ex. 1 Tb/sec can transmit all the worlds TV
  channels.

16
TDM vs DWDM
Figure 6

• TDM does not utilize the full potential of the
  fiber optics link.
• The fiber can be compared to a highway
• TDM uses only one lane
• DWDM uses multiple lanes

Source http//moon.pr.erau.edu/pettitl/DWDM2.htm
17
Questions

• Q1. Name two applications for DWDM.
• A1. DWDM is used in long-distance
  telecommunications where point-to-point or
  fiber-optic rings are already in place. DWDM is
  also used to extend the lifetime of submarine
  cables.
• Q2. Explain why DWDM is efficient for long
  distances.
• A2. DWDMs efficiency over long-distance can be
  attributed to the following
• greater distance between network elements
  (economic savings)
• optical amplifiers reduce the number of
  regenerators over long distances (another less
  costly approach).

18
Questions

• Q3. What are the differences between TDM and
  DWDM?
• A3. TDM splits the capacity of a link into
  timeslots and does not utilize the full potential
  of the fiber optics link. When comparing the
  fiber optics link to a highway, TDM only uses one
  lane and consequently, the maximum capacity is
  quickly reached. DWDM assigns each incoming
  signal to a lane of the highway (i.e. a
  wavelength) therefore maximizing the use of the
  fibers capacity.
• Q4. How does DWDM work?
• A4. Each incoming signal is assigned to a
  frequency within a specified frequency band. It
  is then multiplexed onto a single fiber.

19
Questions

• Q5. Why is DWDM indifferent towards the bit-rate
  and format of the data being transmitted ?
• A5. Because incoming signals are never terminated
  at the optical layer, the DWDM interface is
  bit-rate and format independent. This allows the
  provider to easily integrate the DWDM technology
  into existing network structures.

20
Acronyms

• ATM Asynchronous transfer mode
• SONET Synchronous data transmission on optical
  media (American National Standards)
• SDH Synchronous digital hierarchy
  (international equivalent of SONET)
• IP Internet protocol
• TDM Time division multiplexing
• STM Synchronous transport module
• OC Optical carrier

21
Resources

• http//www.itpapers.com/cgi/PViewIT.pl?scid47pap
  erid8042
• http//moon.pr.erau.edu/pettitl/DWDM2.htmA3
• http//www.iec.org/online/tutorials/dwdm/
• http//whatis.com
• http//www.cableu.net/fibrtech/dwdm.htm