Application Specification
Singlemode Fixed
Buildout Attenuators
NOTE
114-1129
24 AUG 06
Rev C
All numerical values are in metric units [with U.S. customary units in brackets]. Figures and illustrations are for
identification only and are not drawn to scale.
i
1. INTRODUCTION
In a fiber optic system, buildout attenuators play an important role in controlling optical power levels in
telecommunications and CATV applications. As such, they must offer consistent performance over a range of
operating conditions so that attenuation levels remain constant and predictable.
A key feature of buildout attenuators (BOAs) is easy use. Configured as a connector with the plug or ferrule at
one end and the receptacle at the other, they can be installed at a patch panel or receiver by simply unplugging
the cable, plugging the attenuator into the bulkhead adapter, and plugging the cable into the receptacle end of
the attenuator. BOAs are available in a range of fixed loss values typically up to 25 dB. Figure 1 shows
examples of common BOAs.
When corresponding with Tyco Electronics Personnel, use the terminology provided in this specification to
facilitate your inquiries for information. Basic terms and features of this product are provided in Figure 1.
Typical Buildout Attenuators
Protective Cover
SC/UPC, SM
Protective Cover
SC/APC, SM
ST/UPC, SM
Protective Cover
Protective Cover
LC/UPC, SM
D4/PC, SM
FC/UPC, SM
Protective Cover
Figure 1
E
2006 Tyco Electronics Corporation, Harrisburg, PA
*Trademark
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Other products, logos, and company names used are the property of their respective owners.
Singlemode Fixed Buildout Attenuators
2. REFERENCE MATERIAL
2.1. Revision Summary
Revisions to this application specification include
S
Updated document to corporate requirements
S
Changed reference part number in Paragraph 2.2
2.2. Customer Assistance
114-1129
Reference Base Product Part Number 5209250 and Product Code G912 are representative of Singlemode
Fixed Buildout Attenuators. Use of these numbers will identify the product line and expedite your inquiries
through a service network established to help you obtain product and tooling information. Such information can
be obtained through a local Tyco Electronics Representative or, after purchase, by calling the Product
Information number at the bottom of page 1.
2.3. Drawings
Customer Drawings for product part numbers are available from the service network. If there is a conflict
between the information contained in the Customer Drawings and this specification or with any other technical
documentation supplied, call the Product Information number at the bottom of page 1.
2.4. Instructional Material
Instruction Sheet 408–8895 provides information for Attenuator Installation and Cleaning Instructions.
2.5. Specifications
Design Objective 108–2099 and Product Specification 108–2221, which are based on Telcordia GR–910,
provides expected product performance and test information.
3. REQUIREMENTS
DANGER
Never look into the end of a fiber optic connector or attenuator when optical power or laser light inspection devices are
attached to any of the connecting ends of the cable. Infrared light can not be seen but can severely damage the eye.
3.1. Storage
Components are packaged and shipped in protective containers and should remain in them until ready for use
to prevent physical damage. Components should be used on a first in, first out basis to avoid storage
contamination. Storage temperatures should be within –40
_
to 70
_
C [–40
_
F to 158
_
F].
3.2. Attenuator Installation
Refer to Instruction Sheet 408–8895 for Attenuator Installation and Cleaning Instructions.
3.3. System Design Considerations
There are three basic factors a system designer must consider in determining the appropriate buildout
attenuator to use: attenuation level, attenuator housing type, attenuator interface type, and reflectance.
S
Attenuation level (1–30 dB)
–– This parameter is a function of the system budget and the receiver’s
dynamic range.
S
Attenuator housing type (ST, SC, FC, LC, or D4)
–– The attenuator housing type is a function of con-
nectors and adapters used in the system.
S
Attenuator interface type and reflectance (UPC and APC)
–– The choice of the attenuator interface
(UPC or APC) is driven by reflectance tolerance in a system. For instance, CATV systems are very sen-
sitive to reflectance causing signal degradation and require APC finish (8° typically), which offers at least
–65 dB reflectance. On the other hand, digital systems, which are less sensitive to reflectance, can use
UPC finish, yielding –55dB reflectance.
3.4. Applications
Singlemode fixed buildout attenuators are very versatile in their physical application. They can be installed at a
connector panel, inserted in line between two patch cords, or mounted directly at the receiver interface. The
two main applications of buildout attenuators are power attenuation at the receiver and power balancing of
multiple outputs.
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Singlemode Fixed Buildout Attenuators
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Buildout attenuators enable the installer to adjust the optical power level without changing the other
components, or cutting and splicing the fiber as in the case of the in line attenuator. The result is minimum
downtime and maintenance of the overall system configuration.
3.5. Typical Uses of Singlemode Fixed Buildout Attenuators
A. Power Equalization (Balancing) at Patch Distribution Panel or Receiver Panel
Patch panels are extensively used in the telephony and test (laboratory) environments to connect fiber
optic lines to transmission equipment. Occasionally some lines may need to be attenuated at the
distribution or receiver panel to closely match the power in other lines, and, thereby, achieve power
uniformity. One way to achieve this is by inserting the buildout attenuator at the panel without having to
disturb or cut lines. See Figure 2. Because of its compactness and design versatility, the buildout
attenuator can be easily installed on any type of fiber optic panel.
Power equalization through attenuation eliminates the need to carry receivers with different dynamic
ranges. This receiver standardization can reduce system costs and further simplify the designer’s system
budget. Some original equipment manufacturers (OEMs) incorporate buildout attenuators in fiber
distribution frames and as components for optical transport systems, including WDM systems.
Power Equalization at the Patch Panel
5dB Buildout Attenuator
-10dBm
-15dBm
-15dBm
-13dBm
-15dBm
-15dBm
-15dBm
-15dBm
2dB Buildout Attenuator
Connector Panel
Figure 2
B. Signal Attenuation to Meet Receiver's Dynamic Range
If the output power at the receiver exceeds the upper limit of the receiver’s dynamic range, signals may
become distorted, leading to high noise in analog systems and errors in digital transmissions.
See Figure 3.
This situation may arise when a system designer overestimates system losses due to fiber absorption,
connections, splices, and components and chooses the incorrect receiver sensitivity.
To remedy this problem, an inexpensive buildout attenuator can be inserted between the connector
(source) and receiver.
Power Matching at the Receiver
Signal
Dynamic Range
Maximum Signal
Strength
Noise Floor
Wavelength
Figure 3
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Singlemode Fixed Buildout Attenuators
C. Power Matching in SONET and ATM Systems
114-1129
Buildout attenuators may be installed at the optical receiver or at the patch panel of SONET and ATM
systems to equalize powers at the nodes. The distance between the host and the node can vary by
several kilometers depending on the node.
Figure 4 shows an example of a SONET optical layer. A transmitter puts out –3 dBm at a wavelength
range of 1260 to 1360 nm. The signal travelling over a singlemode fiber is divided into four equal outputs
at the 1x4 splitter. There are four receivers that share the same dynamic range (–14 dBm to –31 dBm) to
simplify the system’s design. The optical link distances between a node and the distribution patch panel
vary by several kilometers. The fiber is singlemode and the loss is 0.2dB/km.
Power Matching in a Theoretical SONET Model
3dB Buildout Attenuator
1dB Buildout Attenuator
Rx1
0.5 km
Rx2
Tx
1x4
10 km
Rx3
30 km
Rx4
60 km
Figure 4
The table in Figure 5 shows power and loss levels in the SONET example. A system designer may be
using a similar power budget scheme to determine the attenuation values to match the dynamic range of
the receivers. Analysis shows that a 3 dB buildout attenuator is needed at the Receiver 1 line and a 1 dB
BOA is needed at the Receiver 2 line to deliver power within the receiver dynamic range of –14 dBm to
–31 dBm.
ATTENUATION CALCULATION FOR THEORETICAL SONET MODEL
RECEIVER
Source Tx Output @ 1260 - 1360 nm
Splice / Connector Losses
SM Fiber Loss (0.2dB/km)
1x4 Splitter Loss
Output (0) at Receiver Rx
Rx Upper Dynamic Threshold (U)
= 0-U
Required BOA Attenuation Value
Rx1
-3 dBm
-1 dB
-0.5 dB
-7 dB
-11.5 dBm
-14 dBm
2.5 dB
3 dB
Rx2
-3 dBm
-1 dB
-2 dB
-7 dB
-13 dBm
-14 dBm
-1 dB
1 dB
Rx3
-3 dBm
-1 dB
-6 dB
-7 dB
-17 dBm
-14 dBm
-3 dB
n/a
Rx4
-3 dBm
-1 dB
-12 dB
-7 dB
-23 dBm
-14 dBm
-9 dB
n/a
Figure 5
D. CATV
Video applications demand more stringent reflectance and attenuation tolerance specifications. Reflections
can degrade the system performance. The buildout attenuator, with an 8 or 9 degree polished end face
(APC) meets the low reflectance (<65 dB) requirements. This system may call for attenuators either at the
transceiver, or in line. Figure 6 shows an example of using buildout attenuators to maintain proper power
levels at the splitter in a distribution node. Because distance between the node and the subscriber can
vary, a buildout attenuator can be used to adjust the power levels in each branch.
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Buildout Attenuator (BOA) in CATV System
CATV Headend
Distribution Node
BOA
1x4
Splitter
Patch Panel
BOA
Figure 6
E. DWDM Systems
As the need to multiplex/demultiplex several narrowly spaced signals increases in DWDM systems, so
does the need to match output powers with the receiver’s dynamic range. The buildout attenuator is well
suited for this application since it is wavelength independent. The designer has the option to insert an
attenuator at the detector or patch panel to achieve the proper power level as shown in Figure 7.
F. Test Systems
Manufacturers of erbium–doped fiber amplifiers (EDFA) and other fiber optic equipment use attenuators in
loop measurement setups to measure gain flatness of the EDFA over a certain bandwidth as a function of
distance (for example, 3000, 6000, 10,000 km).
Buildout Attenuator in a WDM System
Tx
Tx
1
2
1
2
Rxc
Rx
BOA
Tx
n
1xN DWDM
X km Fiber
1xN DWDM
n
Rx
Figure 7
4. QUALIFICATIONS/REPORTS
1, 3, 5, and 10dB SC/UPC Fixed Buildout Attenuators have been tested to the requirements of Telcordia
GR–910–CORE. See Tyco Electronics Engineering Reports 502–1197 (1dB), 502–1198 (3dB), 502–1199
(5dB), and 502–1200 (10dB) for results.
5. TOOLING
No tooling is required for the assembly of Singlemode Fixed Buildout Attenuators.
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