DWDM
(Dense Wavelength Division Multiplexing) is a fiber optic transmission
technique that works by combining and transmitting multiple signals simultaneously
on the same fiber in a dense wavelength grid.
 |
| WDM conceptual view. |
DWDM
combines multiple optical signals to one single fibber in order to amplify the
transmission and to increase its bandwidth capacity.
DWDM
technology offers many key benefits such as:
1. Allowing the transmission of
e-mail, video, multimedia, data and more.
2. It is possible to use signals in
different rate and different format (ATM, SONET/SDH, IP, Ethernet and more).
3. A large amount of information can
be transferred.
4. It can handle high bit-rates.
5. Lower cost.
The optical network consists of lasers and optical fibers carrying
flashers of light from the lasers. Increasing the number of lasers will
increase the bit rate. All the lasers send their light to the optical fiber at
the same time, and in order to distinguish between the sources, each flasher
has its own color (which is of different wavelength), in this way the received
information in the other end of the network can be separated to its original.
With this
latest technology, individual lasers can transmit at 10 Gb/s ,and in WDMA
technology we can have several lasers transmitting at the same time (The number
of lasers is , usually , a multiplication of 2).
The
combination of several wavelengths together on the same fiber is called
multiplexing; the separation called de-multiplexing .In order to detect a
specific wavelength we need to use a specific light detector.
DWDM Mux and De-Mux:
 |
| DWDM mux and de-mux. |
The wavelengths of light usually vary around 1550 nanometer (in this
wavelength the loss and the attenuation consider to be low). The wavelength is
a multiply of 0.8nm therefore if you have three wavelengths, It is
possible to use the following wavelengths: 1549.2nm, 1550nm and 1550.8nm.
From a
Quality of Service standpoint, DWDM enables response to protocol changes and
customers' bandwidth demands at lower costs.
DWDM
System Structures:
A basic DWDM system structure is build from the
following components
- transmitters
- receivers
- EDFA
- Add and Drop.
- DWDM multiplexers
- DWDM de-multiplexers.
Explanation of structure entities:
1. Transmitters � lasers that transmit data with a very accurate wavelength � each laser is configured to transmit in a
certain wavelength
2. Receivers� components that receive the signal and transmit
them into a de-multiplexer.
3. EDFA - Erbium-Doped Fiber Amplifier. Optical repeater device that amplifies the optical
signal. Its is silica based optical fibers that is doped with erbium that boost
the power of the wavelength.
4. Add and
Drop � components that receive a fiber optic with some
wavelength multiplexed, and can drop or add a certain lambda from or
to the signal.
5. DWDM
multiplexers � receive many optical signals, each one in
different wavelength, and transmit the entire wavelength in one optic fiber.
6. DWDM de-multiplexers � Receive all the signals in one optic fiber , and transmit each
wavelength in a different fiber.
The
system structure is shown in the following diagram:
 | |
| system structure DWDM |
The
diagram shows that each wavelength transmitted by the laser is inserted into
the multiplexer. The multiplexer combines all
the signals from the different fibers into one signal in the optic fiber. The
optic fiber can be inserted to an add & drop which can take a certain lambda to its channel, or add a certain
lambda from the channel. It can move through EDFA for amplifying the signal. At
the end of the channel it is inserted to a de-multiplexer that separates the different
wavelengths into different optic fibers.
0 comments:
Post a Comment