Tài liệu WDM Module Value-Added Module (VAM) System doc

Overview
Wavelength division multiplexing (WDM) remains the prevailing technology for adding flexibility and
functionality to today’s optical networks. By transmitting signals at different wavelengths through the
same fiber, WDMs can multiply transmission capacity, improve testing, and transmit voice services
over video. Value-Added Module (VAM) systems equipped with WDM technology are used in a
variety of applications to reduce operational expenses and increase revenue opportunities.
Increasing Transmission Capacity
Fiber overlays can be expensive and time consuming. In order to deliver broadband services, many
service providers are integrating WDM modules into the network to gain capacity without deploying
additional fiber.
Adding a WDM on each end of a circuit instantly doubles the bandwidth on a fiber pair. A typical
application features one fiber for the transmit direction and another fiber for the receive direction.
(See Figure 1.) In most cases, legacy equipment will operate at 1310 nm. It is simply a matter of
incorporating a WDM module at each end of the span and adding new equipment transmitting at
1550 nm. In a higher capacity network, transmission signals operating at 1310 nm and 1550 nm are
then simultaneously transmitted over the same fibers. (See Figure 2.) This enables the existing fiber in
the plant to double capacity. The WDM approach also enables providers to work with existing
electronic equipment, which proves to be much more cost-effective than incorporating new DWDM
modules or additional fibers into the network.
WDM Module
Value-Added Module (VAM) System
application note
Figure 1
Original Network
1310 FOT
1310
1310
Single
Fiber
Near End Far End
Tx

Rx
1310 FOT
Tx
Rx
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Value-Added Module (VAM) System
WDM Module
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Nonintrusive Testing
WDM modules introduce out-of-band testing by enabling networks to operate and test at different
wavelengths. A network operating at 1310 nm can be tested at 1550 nm and networks operating at 1550
nm can be tested at 1625 nm. Out-of-band testing is a simple, effective solution that is easy to implement
into the network. (See Figure 3.)
Often, access to the customer or co-location site is restricted. With WDMs, a signal at a different
wavelength from the normal traffic is injected at the near end of a system and travels to the far end, where
it is looped back via a WDM at the demarcation point and returns to the original end. This allows full bi-
directional OTDR (optical time domain reflectometer) testing on a live transmit/receive pair to be conducted
from a central location. The service provider reduces operational expenses by not rolling a truck to the far
end or disrupting customer’s service for testing purposes.
Figure 2
Higher Capacity Network with WDMs
1550
Near End
1310 FOT
Tx
Rx
WDM
Module

WDM
1550 FOT
Tx
Rx
WDM
Module
WDM
Far End
1310 FOT
Tx
Rx
WDM
Module
WDM
1550 FOT
Tx
Rx
WDM
Module
WDM
1310
Single
Fiber
Single
Fiber
1550
1310
Figure 3
Continual Nonintrusive Testing
Single

Fiber
Single
Fiber
1550
Near End
1310 FOT
Tx
Rx
WDM
Module
WDM
1550
Test
Box
Tx
Rx
WDM
Module
WDM
Far End
1310 FOT
Tx
Rx
WDM
Module
WDM
Tx
Rx
WDM
Module

WDM
1310
1550
1310
1550
Test
Box
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Value-Added Module (VAM) System
WDM Module
Figure 4
REAR FRONT
Connectorized
Pigtail
Adapter Port
Adapter
Port
OPTICAL
COMPONENTS
Connectorized
Pigtail
(3 mm Jacketed)
Bare Pigtail
(2 mm Jacketed)
Transmitting Voice Services over Video
When video requirements arise, a WDM network offers a cost-competitive option compared to additional
fiber deployment. In most applications, a 1310 nm fiber route has already been established to

accommodate traditional voice grade service. By using a 1550 nm video transmitter, both video and voice
co-exist on the same fiber pairs, but are independently delivered to the subscriber.
Value-Added Functionality
ADC’s plug-in VAM modules can be purchased with most industry standard singlemode connectors.
Module inputs and outputs can be made via adapter, pigtail or bare fiber depending on customer
requirements. (See Figure 4.) Various combinations of all front access to input/output ports or rear access to
both input/output ports are also available. All bare fiber options use 2 mm jacketing.
The variety of module configurations allows the provider the opportunity to determine the number and
type of optical connections necessary depending on whether a cross-connect or interconnect arrangement
is used in the fiber cable management scheme.
ADC Telecommunications, Inc., P.O. Box 1101, Minneapolis, Minnesota USA 55440-1101
Specifications published here are current as of the date of publication of this document. Because we are continuously improving our products, ADC
reserves the right to change specifications without prior notice. At any time, you may verify product specifications by contacting our headquarters
office in Minneapolis. ADC Telecommunications, Inc. views its patent portfolio as an important corporate asset and vigorously enforces its patents.
Products or features contained herein may be covered by one or more U.S. or foreign patents. An Equal Opportunity Employer
1226582 5/02 Original © 2002 ADC Telecommunications, Inc. All Rights Reserved
Web Site: www.adc.com
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