Cisco ONS 15501 User manual

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Tel: [phone]
800 553-NETS (6387)
Fax: [phone]
Cisco ONS 15501 User Guide
Release 1.0
February 2002
Customer Order Number: DOC-7814134=
Text Part Number: 78-14134-01

THE SPECIFICATIONS AND INFORMATION REGARDING THE PRODUCTS IN THIS MANUAL ARE SUBJECT TO CHANGE WITHOUT NOTICE. ALL
STATEMENTS, INFORMATION, AND RECOMMENDATIONS IN THIS MANUAL ARE BELIEVED TO BE ACCURATE BUT ARE PRESENTED WITHOUT
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OR LIMITED WARRANTY, CONTACT YOUR CISCO REPRESENTATIVE FOR A COPY.
The following information is for FCC compliance of Class A devices: This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant
to part 15 of the FCC rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial
environment. This equipment generates, uses, and can radiate radio-frequency energy and, if not installed and used in accordance with the instruction manual, may cause
harmful interference to radio communications. Operation of this equipment in a residential area is likely to cause harmful interference, in which case users will be required
to correct the interference at their own expense.
The following information is for FCC compliance of Class B devices: The equipment described in this manual generates and may radiate radio-frequency energy. If it is not
installed in accordance with Cisco’s installation instructions, it may cause interference with radio and television reception. This equipment has been tested and found to
comply with the limits for a Class B digital device in accordance with the specifications in part 15 of the FCC rules. These specifications are designed to provide reasonable
protection against such interference in a residential installation. However, there is no guarantee that interference will not occur in a particular installation.
Modifying the equipment without Cisco’s written authorization may result in the equipment no longer complying with FCC requirements for Class A or Class B digital
devices. In that event, your right to use the equipment may be limited by FCC regulations, and you may be required to correct any interference to radio or television
communications at your own expense.
You can determine whether your equipment is causing interference by turning it off. If the interference stops, it was probably caused by the Cisco equipment or one of its
peripheral devices. If the equipment causes interference to radio or television reception, try to correct the interference by using one or more of the following measures:
• Turn the television or radio antenna until the interference stops.
• Move the equipment to one side or the other of the television or radio.
• Move the equipment farther away from the television or radio.
• Plug the equipment into an outlet that is on a different circuit from the television or radio. (That is, make certain the equipment and the television or radio are on circuits
controlled by different circuit breakers or fuses.)
Modifications to this product not authorized by Cisco Systems, Inc. could void the FCC approval and negate your authority to operate the product.
The Cisco implementation of TCP header compression is an adaptation of a program developed by the University of California, Berkeley (UCB) as part of UCB’s public
domain version of the UNIX operating system. All rights reserved. Copyright © 1981, Regents of the University of California.
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OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
Cisco ONS 15501 User Guide
Copyright © 2002, Cisco Systems, Inc.
All rights reserved.
CCIP, CCSP, the Cisco Arrow logo, the Cisco Powered Network mark, Cisco Unity, Follow Me Browsing, FormShare, and StackWise are trademarks of Cisco Systems, Inc.;
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All other trademarks mentioned in this document or Website are the property of their respective owners. The use of the word partner does not imply a partnership relationship
between Cisco and any other company. (0403R)

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CONTENTS
Preface vii
Audience vii
Organization vii
Conventions viii
Related Documentation x
Obtaining Documentation x
World Wide Web x
Documentation CD-ROM x
Ordering Documentation x
Documentation Feedback xi
Obtaining Technical Assistance xi
Cisco.com xi
Technical Assistance Center xi
Cisco TAC Web Site xii
Cisco TAC Escalation Center xii
Product Overview 1-1
Product Description 1-1
Optical Specifications 1-2
Key Features 1-2
Constant Gain Flatness 1-3
Optimized Automatic Gain Control 1-3
Variable Gain 1-3
Transient Suppression 1-4
Low Noise Figure 1-4
High Maximum Output Power 1-4
Network Management 1-4
Cisco ONS 15501 Applications 1-5
Point-to-Point Topologies 1-5
Ring Topologies 1-5
Adding or Dropping Wavelengths 1-7
Adjusting to Span Loss Changes 1-7
Cisco ONS 15501 Front Panel 1-7
Cisco ONS 15501 LED Alarm Definitions 1-8

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Installing the Cisco ONS 15501 2-1
Creating a Site Log 2-1
Required Tools and Parts 2-2
Installation Checklist 2-2
Rack-Mounting the Chassis 2-3
Optical Connection 2-3
DC Power Connection 2-4
Grounding the Chassis 2-5
Connecting the Power 2-5
Communication Connections 2-6
Setting Up Alarm Contacts 2-7
Installation Commands 2-7
Introductory Commands 2-7
Review and Operational Commands 2-7
Configuring the Cisco ONS 15501 3-1
Configuring Local Serial Communication 3-1
Setting Up the Software 3-1
Configuring a Basic System 3-2
Monitoring Alarms and Traps 3-2
Upgrading the Flash Image 3-3
Configuring Remote Communication 3-3
Configuring for Telnet 3-3
Configuring for SNMP 3-4
Alarm Contact Closures 3-4
Command Reference 4-1
add-snmp-com 4-2
add-snmp-mgr 4-3
alarm 4-4
boot-bank 4-5
del-snmp-com 4-6
del-snmp-mgr 4-7
ethmode 4-8
gain 4-9
gainmean 4-10
gaintrig 4-11
get-snmp-com 4-12

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get-snmp-mgr 4-13
help 4-14
hide-trap 4-15
host-config 4-16
inpwr 4-17
inpwrmean 4-18
inpwrtrig 4-19
ip-config 4-20
logout 4-21
ntp 4-22
ntp-ip 4-23
optoutpwr 4-24
outattn 4-25
outsigpwr 4-26
outsigpwrmean 4-27
outsigpwrtrig 4-28
ping 4-29
ps1 4-30
ps2 4-31
reboot 4-32
resetmeantrig 4-33
restore 4-35
setgainmean 4-36
setgaintrig 4-37
setinpwrmean 4-38
setinpwrtrig 4-39
set-master-pwd 4-40
setoutsigpwrmean 4-41
setoutsigpwrtrig 4-42
settempmean 4-43
settemptrig 4-44
set-time 4-45
set-user-pwd 4-47
show-trap 4-48
status 4-49

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sw-download 4-50
sys-info 4-51
temp 4-52
tempmean 4-53
temptrig 4-54
time 4-55
timeout 4-56
timezone 4-57
Troubleshooting 5-1
Basic Diagnostic Procedures 5-1
Isolating the Problem 5-2
Reading the Front Panel LEDs 5-2
Password Recovery 5-3
Technical Support 5-3
Technical Specifications A-1
Cisco ONS 15501 Optical Specifications A-1
Cisco ONS 15501 Electrical Specifications A-1
Cisco ONS 15501 Mechanical Specifications A-2
Cisco ONS 15501 DC Input Power Requirements A-2
Connector Pinouts B-1
Time Zone Codes C-1
Translated Safety Warnings D-1
Wrist Strap Warning D-1
Restricted Area Warning D-2
Qualified Personnel Warning D-3
DC Protection D-4
Disconnect Device Warning D-5
Laser Radiation Warning D-6
INDEX

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Preface
This preface describes the audience, organization, and conventions for the Cisco ONS 15501 User
Guide. It also provides information about how to obtain related documentation and technical assistance.
Audience
Only trained and qualified personnel should be allowed to install, maintain, or troubleshoot the
Cisco ONS 15501. Such individuals must be familiar with general optical transmission technology to
properly utilize the unit.
Organization
This guide includes the following chapters:
Chapter Title Description
Chapter 1 Product Overview Describes the Cisco ONS 15501 and its key features and ap-
plications.
Chapter 2 Installing the Cisco
ONS 15501
Describes how to install the Cisco ONS 15501.
Chapter 3 Configuring the Cisco
ONS 15501
Describes how to configure the Cisco ONS 15501 for onsite
or remote monitoring.
Chapter 4 Command Reference Lists the CLI commands used in the Cisco ONS 15501 envi-
ronment.
Chapter 5 Troubleshooting Describes the basic fault investigation and diagnostic (trou-
bleshooting) procedures for the Cisco ONS 15501.
Appendix A Technical Specifica-
tions
Lists the technical specifications for the Cisco ONS 15501.
Appendix B Connector Pinouts Illustrates the pin configuration of the RS-232 DB-9 type
connector and the Alarm Out RJ-45 connector.
Appendix C Time Zone Codes Lists time zones and their correlating abbreviations, which
are used when setting the time of the system.
Appendix D Translated Safety
Warnings
Lists the warnings in this guide and translates them into
different languages.

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Conventions
Conventions
Notes use the following conventions:
Note Means reader take note. Notes contain helpful suggestions or references to material not covered in the
publication.
Cautions use the following conventions:
Caution Means caution should be taken. Cautions contain information that is important to follow so as not to
cause harm to the equipment.
Warnings use the following conventions:
Warning This warning symbol means danger. You are in a situation that could cause bodily in-
jury. Before you work on any equipment, be aware of the hazards involved with elec-
trical circuitry and be familiar with standard practices for preventing accidents. To
see translations of the warnings that appear in this publication, refer to the Regulatory
Compliance and Safety Information document that accompanied this device.
Waarschuwing
Dit waarschuwingssymbool betekent gevaar. U verkeert in een situatie die lichamelijk
letsel kan veroorzaken. Voordat u aan enige apparatuur gaat werken, dient u zich be-
wust te zijn van de bij elektrische schakelingen betrokken risico's en dient u op de
hoogte te zijn van standaard maatregelen om ongelukken te voorkomen. Voor vertalin-
gen van de waarschuwingen die in deze publicatie verschijnen, kunt u het document
Regulatory Compliance and Safety Information (Informatie over naleving van veilig-
heids- en andere voorschriften) raadplegen dat bij dit toestel is ingesloten.
Varoitus
Tämä varoitusmerkki merkitsee vaaraa. Olet tilanteessa, joka voi johtaa ruumiinvam-
maan. Ennen kuin työskentelet minkään laitteiston parissa, ota selvää sähkökyt-
kentöihin liittyvistä vaaroista ja tavanomaisista onnettomuuksien ehkäisykeinoista.
Tässä julkaisussa esiintyvien varoitusten käännökset löydät laitteenmukana olevasta
Regulatory Compliance and Safety Information -kirjasesta (määräysten noudattaminen
ja tietoa turvallisuudesta).
Attention
Ce symbole d'avertissement indique un danger. Vous vous trouvez dans une situation
pouvant causer des blessures ou des dommages corporels. Avant de travailler sur un
équipement, soyez conscient des dangers posés par les circuits électriques et famil-
iarisez-vous avec les procédures couramment utilisées pour éviter les accidents. Pour
prendre connaissance des traductions d’avertissements figurant dans cette publica-
tion, consultez le document Regulatory Compliance and Safety Information (Confor-
mité aux règlements et consignes de sécurité) qui accompagne cet appareil.

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Conventions
Warnung
Dieses Warnsymbol bedeutet Gefahr. Sie befinden sich in einer Situation, die zu einer
Körperverletzung führen könnte. Bevor Sie mit der Arbeit an irgendeinem Gerät begin-
nen, seien Sie sich der mit elektrischen Stromkreisen verbundenen Gefahren und der
Standardpraktiken zur Vermeidung von Unfällen bewußt. Übersetzungen der in dieser
Veröffentlichung enthaltenen Warnhinweise finden Sie im Dokument Regulatory Com-
pliance and Safety Information (Informationen zu behördlichen Vorschriften und
Sicherheit), das zusammen mit diesem Gerät geliefert wurde.
Avvertenza
Questo simbolo di avvertenza indica un pericolo. La situazione potrebbe causare in-
fortuni alle persone. Prima di lavorare su qualsiasi apparecchiatura, occorre
conoscere i pericoli relativi ai circuiti elettrici ed essere al corrente delle pratiche
standard per la prevenzione di incidenti. La traduzione delle avvertenze riportate in
questa pubblicazione si trova nel documento Regulatory Compliance and Safety Infor-
mation (Conformità alle norme e informazioni sulla sicurezza) che accompagna questo
dispositivo.
Advarsel
Dette varselsymbolet betyr fare. Du befinner deg i en situasjon som kan føre til person-
skade. Før du utfører arbeid på utstyr, må du vare oppmerksom på de faremomentene
som elektriske kretser innebærer, samt gjøre deg kjent med vanlig praksis når det
gjelder å unngå ulykker. Hvis du vil se oversettelser av de advarslene som finnes i
denne publikasjonen, kan du se i dokumentet Regulatory Compliance and Safety Infor-
mation (Overholdelse av forskrifter og sikkerhetsinformasjon) som ble levert med
denne enheten.
Aviso
Este símbolo de aviso indica perigo. Encontra-se numa situação que lhe poderá causar
danos físicos. Antes de começar a trabalhar com qualquer equipamento, familiarize-
se com os perigos relacionados com circuitos eléctricos, e com quaisquer práticas
comuns que possam prevenir possíveis acidentes. Para ver as traduções dos avisos
que constam desta publicação, consulte o documento Regulatory Compliance and
Safety Information (Informação de Segurança e Disposições Reguladoras) que acom-
panha este dispositivo.
¡Advertencia!
Este símbolo de aviso significa peligro. Existe riesgo para su integridad física. Antes
de manipular cualquier equipo, considerar los riesgos que entraña la corriente eléc-
trica y familiarizarse con los procedimientos estándar de prevención de accidentes.
Para ver una traducción de las advertencias que aparecen en esta publicación, con-
sultar el documento titulado Regulatory Compliance and Safety Information (Infor-
mación sobre seguridad y conformidad con las disposiciones reglamentarias) que se
acompaña con este dispositivo.
Varning!
Denna varningssymbol signalerar fara. Du befinner dig i en situation som kan leda till
personskada. Innan du utför arbete på någon utrustning måste du vara medveten om
farorna med elkretsar och känna till vanligt förfarande för att förebygga skador. Se
förklaringar av de varningar som förkommer i denna publikation i dokumentet Regula-
tory Compliance and Safety Information (Efterrättelse av föreskrifter och säkerhetsin-
formation), vilket medföljer denna anordning.

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Related Documentation
Related Documentation
Refer to the following documents for additional information about the Cisco ONS 15501:
•Regulatory Compliance and Safety Information for the Cisco ONS 15501
•Introduction to DWDM Technology
•Cisco ONS 15540 ESP Planning and Design Guide
•Cisco ONS 15540 ESP Configuration Guide and Command Reference
•Cisco ONS 15540 ESP Troubleshooting Guide
•Cisco ONS 15540 ESP MIB Quick Reference
•Glossary of Optical Networking Terms
Obtaining Documentation
The following sections explain how to obtain documentation from Cisco Systems.
World Wide Web
You can access the most current Cisco documentation on the World Wide Web at the following URL:
http://www.cisco.com
Translated documentation is available at the following URL:
http://www.cisco.com/public/countries_languages.shtml
Documentation CD-ROM
Cisco documentation and additional literature are available in a Cisco Documentation CD-ROM
package, which is shipped with your product. The Documentation CD-ROM is updated monthly and may
be more current than printed documentation. The CD-ROM package is available as a single unit or
through an annual subscription.
Ordering Documentation
Cisco documentation is available in the following ways:
•Registered Cisco Direct Customers can order Cisco product documentation from the Networking
Products MarketPlace:
http://www.cisco.com/cgi-bin/order/order_root.pl
•Registered Cisco.com users can order the Documentation CD-ROM through the online Subscription
Store:
http://www.cisco.com/go/subscription
•Nonregistered Cisco.com users can order documentation through a local account representative by
calling Cisco corporate headquarters (California, USA) at 408 526-7208 or, elsewhere in North
America, by calling 800 553-NETS (6387).

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Obtaining Technical Assistance
Documentation Feedback
If you are reading Cisco product documentation on Cisco.com, you can submit technical comments
electronically. Click Leave Feedback at the bottom of the Cisco Documentation home page. After you
complete the form, print it out and fax it to Cisco at 408 527-0730.
You can e-mail your comments to [e-mail].
To submit your comments by mail, use the response card behind the front cover of your document, or
write to the following address:
Cisco Systems
Attn: Document Resource Connection
170 West Tasman Drive
San Jose, CA 95134-9883
We appreciate your comments.
Obtaining Technical Assistance
Cisco provides Cisco.com as a starting point for all technical assistance. Customers and partners can
obtain documentation, troubleshooting tips, and sample configurations from online tools by using the
Cisco Technical Assistance Center (TAC) Web Site. Cisco.com registered users have complete access to
the technical support resources on the Cisco TAC Web Site.
Cisco.com
Cisco.com is the foundation of a suite of interactive, networked services that provides immediate, open
access to Cisco information, networking solutions, services, programs, and resources at any time, from
anywhere in the world.
Cisco.com is a highly integrated Internet application and a powerful, easy-to-use tool that provides a
broad range of features and services to help you to
•Streamline business processes and improve productivity
•Resolve technical issues with online support
•Download and test software packages
•Order Cisco learning materials and merchandise
•Register for online skill assessment, training, and certification programs
You can self-register on Cisco.com to obtain customized information and service. To access Cisco.com,
go to the following URL:
http://www.cisco.com
Technical Assistance Center
The Cisco TAC is available to all customers who need technical assistance with a Cisco product,
technology, or solution. Two types of support are available through the Cisco TAC: the Cisco TAC
Web Site and the Cisco TAC Escalation Center.

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Obtaining Technical Assistance
Inquiries to Cisco TAC are categorized according to the urgency of the issue:
•Priority level 4 (P4)—You need information or assistance concerning Cisco product capabilities,
product installation, or basic product configuration.
•Priority level 3 (P3)—Your network performance is degraded. Network functionality is noticeably
impaired, but most business operations continue.
•Priority level 2 (P2)—Your production network is severely degraded, affecting significant aspects
of business operations. No workaround is available.
•Priority level 1 (P1)—Your production network is down, and a critical impact to business operations
will occur if service is not restored quickly. No workaround is available.
Which Cisco TAC resource you choose is based on the priority of the problem and the conditions of
service contracts, when applicable.
Cisco TAC Web Site
The Cisco TAC Web Site allows you to resolve P3 and P4 issues yourself, saving both cost and time. The
site provides around-the-clock access to online tools, knowledge bases, and software. To access the
Cisco TAC Web Site, go to the following URL:
http://www.cisco.com/tac
All customers, partners, and resellers who have a valid Cisco services contract have complete access to
the technical support resources on the Cisco TAC Web Site. The Cisco TAC Web Site requires a
Cisco.com login ID and password. If you have a valid service contract but do not have a login ID or
password, go to the following URL to register:
http://www.cisco.com/register/
If you cannot resolve your technical issues by using the Cisco TAC Web Site, and you are a Cisco.com
registered user, you can open a case online by using the TAC Case Open tool at the following URL:
http://www.cisco.com/tac/caseopen
If you have Internet access, it is recommended that you open P3 and P4 cases through the Cisco TAC
Web Site.
Cisco TAC Escalation Center
The Cisco TAC Escalation Center addresses issues that are classified as priority level 1 or priority
level 2; these classifications are assigned when severe network degradation significantly impacts
business operations. When you contact the TAC Escalation Center with a P1 or P2 problem, a Cisco TAC
engineer will automatically open a case.
To obtain a directory of toll-free Cisco TAC telephone numbers for your country, go to the following
URL:
http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml
Before calling, please check with your network operations center to determine the level of Cisco support
services to which your company is entitled; for example, SMARTnet, SMARTnet Onsite, or Network
Supported Accounts (NSA). In addition, please have available your service agreement number and your
product serial number.

CHAPTER
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Product Overview
The Cisco ONS 15501 is a low-noise, gain-flattened C-band optical EDFA (erbium-doped fiber
amplifier). This guide describes how to install and operate the Cisco ONS 15501.
The Cisco ONS 15501 complements high-performance digital transmitters in topologies requiring
amplification of 1550-nm optical signals.
This chapter includes the following sections:
•Product Description, page 1-1
•Optical Specifications, page 1-2
•Key Features, page 1-2
•Cisco ONS 15501 Applications, page 1-5
•Cisco ONS 15501 Front Panel, page 1-7
Product Description
The Cisco ONS 15501 contains an erbium-doped optical fiber, optical couplers, and one or more pump
lasers and isolators. An optical signal (within a range of 1530 to 1563 nm) arrives at the input connector.
The 1550- nm signal travels through a length of erbium-doped fiber cable. Inside the amplifier, light
from a laser at a wavelength of 980 nm (called the pump laser) is used to amplify the signal at 1550 nm.
The amplified signal is coupled to the output cable for transmission to a node. In longer cable runs, up
to six Cisco ONS 15501 EDFAs can be connected in tandem.
The Cisco ONS 15501 uses 980-nm pump lasers that are built to meet Bellcore TR-NWT-000468 and
MIL-883D standards. With a noise figure approaching the theoretical minimum, the amplifier achieves
results superior to that obtained from a 1480-nm pump laser. The 980-nm pump laser has a long lifetime,
exceeding one million hours. Use of a small number of high-quality components makes the
Cisco ONS 15501 a highly reliable product.
The Cisco ONS 15501 is polarization, modulation, and frequency independent, and operates in
gain-controlled mode. It is optimized for different input and output powers, and can be used as a
preamplifier, inline amplifier, or booster. The unit provides excellent gain flatness for the cascading of
amplifiers in DWDM applications.
The Cisco ONS 15501 is physically designed to fit into a 19-inch, 23-inch, or ETSI equipment rack, with
front, middle, or rear mounting capability. It is equipped with connectors for optional monitoring either
locally or remotely.

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Chapter 1 Product Overview
Optical Specifications
Optical Specifications
Table 1-1 lists the Cisco ONS 15501 optical specifications. For other technical specifications, see
Appendix A, “Technical Specifications.”
Key Features
The Cisco ONS 15501 has the following key features:
•Constant flat gain of 17dB over the 1530 to 1563 nm band
•Optimized automatic gain control for the MAN
•Variable gain for flexibility in network design
•Typical transient suppression within 50 microseconds
•Low noise figure of < 6.0 dB
•Input power range of -29 to 0 dBm
•Network management
Table 1-1 Cisco ONS 15501 Optical Specifications
Description Specification
Wavelength range 1530 to 1563 nm
Input power range -29 to 0 dBm
Saturated output power 17.3 ± 0.3 dBm
Noise figure < 6.0 dB
Nominal gain +17 dB
Gain flatness < 1.5 dB
Settable variable gain 17 dB - 7 dB1
1. Gain flatness is <1.5 dB for 17-13 dB; <2.0 dB for 7-13 dB.
Automatic gain control accuracy ± 1.0 dB
Transient suppression response time 50 microseconds
Backward ASE (amplified spontaneous emission) power < -25 dBm
PMD (polarization mode dispersion) < 0.6 ps
Mode of operation Unidirectional
Optical return loss > 27 dB
Input and output isolation > 30 dB
Polarization sensitivity < 0.5 dB

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Chapter 1 Product Overview
Key Features
Constant Gain Flatness
The Cisco ONS 15501 is a constant gain amplifier. It does not deliver a constant output, but rather
ensures that the output energy spectrum is gain-flattened irrespective of input power (up to the maximum
allowed). If a channel is removed, the output level will drop at the wavelength that is removed, but the
remaining energy spectrum will remain nearly flat over its wavelength band. The gain flatness is also
only minimally affected if the input signal is not flat by several decibels.
Optimized Automatic Gain Control
The Cisco ONS 15501 has a wide input power range of 0 to -29 dBm, over which it maintains gain
flatness as well as a low noise figure across the entire C band. The Cisco ONS 15501 maintains a high
level of precision, as well as speed, which allows it to be used as a booster, inline or preamplifier, thus
reducing sparing expenses. The constant gain and noise figure capabilities of the Cisco ONS 15501
make network designs simpler and more predictable.
The lower gain available in the Cisco ONS 15501, combined with its ability to handle input signal
powers of up to 0 dBm, also enables the network designer to achieve much higher OSNR (optical
signal-to-noise ratio) after cascading several EDFAs. In addition, it allows the network to expand beyond
32 wavelengths to a maximum of 128 wavelengths if necessary. The OSNR improvements of 6 dB is
equivalent to a four-fold increase in the number of EDFAs that can be cascaded. Alternatively, the unit
can accommodate signals with four times the data rate (for instance, OC-192 as opposed to OC-48).
Thus, the limitations of higher gain EDFAs that have input powers limited to -6 dBm can be easily
overcome by using the Cisco ONS 15501. Some representative figures are included in Table 1-2,
assuming a flat input to the first Cisco ONS 15501.
.
Variable Gain
When the gain of an EDFA is fixed, the assumption is that all networks can be laid out with equally
spaced EDFAs. In reality, this is rarely the case. For designs in which the spacing must be flexible,
variable gain allows the network designer to tailor network requirements much more accurately. For
instance, when an Cisco ONS 15501 is used as a preamplifier for receivers having an overload point of
-8 dBm per wavelength, the output VOA (variable optical attenuator) can prevent overload by reducing
Table 1-2 Relative OSNR in Cascading EDFAs
Number of
Cascaded
EDFAs
Number of
Wavelengths
Worst Case OSNR at 17 dB Gain1at
Gain Minimum
1. 0 dBm total input power.
OSNR, 23 dB Gain2
2. -6 dBm total; -21 dBm per channel.
1 32 37.00 dB 31.00 dB
2 32 33.25 dB 27.25 dB
3 32 30.70 dB 24.70 dB
4 32 28.75 dB 22.70 dB
5 32 27.00 dB 21.00 dB
6 32 25.50 dB 19.50 dB

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Key Features
the signal going to the receiver. Alternately, when EDFA spacing is only 10 dB, the output VOA can be
enabled to avoid saturation of the next stage EDFA, ensuring that the entire network has good gain
flatness and virtually consistent OSNR across all wavelengths.
The variable gain capabilites of the Cisco ONS 15501 greatly enhance the flexibility of an optical
network. System operators can add or drop optical elements, such as OADM (optical add/drop
multiplexer), without drastic network redesigns or costly equipment changes. When a change occurs in
span loss, the adjustable gain can be used to reset the network to a better operating point.
Transient Suppression
Transients in the performance of EDFAs are inevitable whenever the number of signals or the relative
power of signals change. For example, when channel rerouting or system failure (caused by a fiber cut
or equipment malfunction) transfers all incoming power to a single “surviving channel,”that channel
will momentarily experience a higher gain, which can cause BER (bit error rate) problems due to
eye-pattern closure. The amount of time required by an amplifier to recover from such a change indicates
its suitability for add/drop applications.
The most important parameters in transient suppression are the recovery time and the overshoot and
undershoot amplitude. The recovery time for the signal amplitude to get within 10% of the “steady state”
amplitude after the switching event is referred to as the transient suppression time. Smaller values are
desirable. From a 10 dB change in power (simulating the adding or dropping of 29 out of 32 channels
present), the Cisco ONS 15501 never exceeds 100 microseconds and is typically below 50
microseconds. The Cisco ONS 15501 can respond to the most drastic power changes with overshoots or
undershoots of less than 1 dB.
Low Noise Figure
The low noise characteristics of the Cisco ONS 15501 allow over six amplifiers to be cascaded and still
achieve an excellent OSNR at input powers as low as –21 dBm per channel. This enables seamless
migration to higher speeds beyond OC-48 and to a larger number of channels.
High Maximum Output Power
The high maximum optical power of the Cisco ONS 15501 increases the number of wavelengths that can
potentially be routed to it. The higher input power range available can be used to increase the number of
wavelengths to 128 from 32, without having any spectral gain tilt effects.
Network Management
The Cisco ONS 15501 supports SNMP, and it has a console port to facilitate setup and monitoring. With
a customer-supplied network monitor and the provided MIB file, all monitorable and settable parameters
are available remotely.

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Cisco ONS 15501 Applications
Cisco ONS 15501 Applications
The Cisco ONS 15501 supports the following applications:
•Point-to-point topologies
•Ring topologies
•Adding or dropping wavelengths
•Adjusting to span loss changes
Point-to-Point Topologies
In a metropolitan point-to-point DWDM network, the Cisco ONS 15501 can function as a pre-, post-,
and/or inline amplifier. Most metropolitan point-to-point DWDM networks require post-amplifiers, but
if a given span length exceeds the unit gain (>17 dB), a preamplifier may also be required to handle the
optical link loss budget. When the span length greatly exceeds 17 dB, an inline amplifier might also be
required.
Because of the wide input power range (-29 to 0 dBm) of the Cisco ONS 15501, trunk attenuation is
typically also necessary, especially when the unit is used as a post-amplifier. For instance, when the per
channel output power from the node is -5 dBm in a 32-channel system, the total output power from the
node is +10 dBm. Thus, at least 10 dB of trunk attenuation is required directly preceding the amplifier.
The Cisco ONS 15501 can also be tuned to meet post- or inline amplification input power requirements.
Assuming that the typical per channel power levels in a point-to-point network are identical at the source
node, and that there are fewer than four amplifiers between source and destination nodes, it is not
necessary to maintain per channel power equalization to satisfy each amplifier’s total input power
requirement and maintain acceptable OSNR for each channel.
Ring Topologies
An amplified ring topology requires more fine-tuning of power for each channel or band. Figure 1-1
illustrates a hubbed ring network utilizing counter-clockwise signal transmission. All bands (A, B, C and
D) are transmitted from node 1. Node 2 terminates and transmits bands A and B; node 3 terminates and
transmits band C; and node 4 terminates and transmits band D.

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Figure 1-1 Power Equalization in an Amplified Ring Network
In general, EDFAs in a ring topology should be placed so they maintain the power level at the receiver,
as well as the OSNR, of each channel. In this case, EDFAs serving as postamplifiers are located at nodes
2and4.
At node 2, the input power level of the EDFA is much higher than the input power level of the
pass-through band (bands C and D), due to the added power from bands A and B. If trunk attenuation is
employed directly before the EDFA at node 2 to keep the unit’s total input power within the required
range, the power levels of both the add band (bands A and B) and the pass-through band (bands C and
D) are attenuated equally. As a result, the power level of the pass-through band is much lower than that
of the add band. This significantly degrades the OSNR of the pass-through band, and in cases where
there are more than two EDFAs in the ring, some of the channels in the ring will not meet OSNR
requirements.
To solve this problem, optical power attenuation should be applied on a per channel or per band basis.
More attenuation is typically required for the add band than for the pass-through band. At the EDFA
input, the individual channel or band power levels should be equalized as close as possible to the
maximum per channel input power level, (for example, -15 dBm in a 32-channel system). This process
of optical power equalization is necessary to obtain better OSNR.

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Cisco ONS 15501 Front Panel
Inserting attenuation devices such as VOAs (variable optical attenuators) between the OADM (optical
add/drop multiplexer) and the transmitter allows optical power management of individual channels. Per
band power management at the trunk line, between the OADM and the EDFA, is also an effective
method. The Cisco ONS 15501 is capable of supporting either approach, and its wide input range (-29
to 0 dBm) makes it an ideal amplifier for a broad array of ring network designs.
Adding or Dropping Wavelengths
Automatic gain control reacts to the adding or dropping of wavelengths in a network, without requiring
power equalization tuning. The fast response of the Cisco ONS 15501 reduces the impact of adding or
dropping channels, and prevents BER hits.
Adjusting to Span Loss Changes
It is typically necessary to adjust gain and attenuation values both for trunk attenuation and channel or
band power equalization.
Cisco ONS 15501 Front Panel
Figure 1-2 shows the Cisco ONS 15501 front panel. The front panel provides an all-front access
interface (fibers, power, alarm contact, and management) that complies with international standards.
Table 1-3 explains the front panel features.
Figure 1-2 Cisco ONS 15501 Front Panel
POWER
ALARM OUT
Cisco ONS 15501
FAI L
LOS
-48V RET -48V RET
LAN
RS-232
DC connectors shown
with cover removed
53 7 10
1 8 9 11 112 6
68377
4
INVISIBLE LASER RADIATION.
DO NOT VIEW DIRECTLY WITH
OPTICAL INSTRUMENTS.
CLASS 1M LASER PRODUCT.

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Cisco ONS 15501 Front Panel
Cisco ONS 15501 LED Alarm Definitions
The Cisco ONS 15501 front panel has three LEDs:
•The green POWER LED turns on or off to reflect the following conditions:
– On: An internal power supply is within tolerance (the Cisco ONS 15501 is powered normally).
– Off: An internal power supply is not present or is out of tolerance.
Table 1-3 Cisco ONS 15501 Front Panel Features
Feature Description
1. Output monitor (connector) Provides spectrum monitoring of the Cisco ONS 15501
output and uses an SC/UPC type bulkhead connector.
(A shutter automatically closes when the cable is removed.)
2. Output (connector) Provides output to an optical fiber cable and uses an SC/
UPC type standard connector. (A shutter automatically
closes when the cable is removed.)
3. Input (connector) Provides optical fiber cable access to the input of the
Cisco ONS 15501 and uses an SC/UPC type standard con-
nector. (This is a nonshuttered connector.)
4. Fail (red LED) Indicates a major failure, such as the pump laser, power
supply, or the temperature level.
5. Power (green LED) Indicates the unit is receiving normal operating power.
6. LOS (loss of signal) (yellow LED) Indicates a loss of input signal when the input signal falls
below the LOS threshold.
7. RS-232 (connector) Provides a console port for local monitoring of the
Cisco ONS 15501 and uses a DB-9 type female connector.
(See Appendix B, “Connector Pinouts.”) This port should
only be used for the evaluation of the unit by a trained tech-
nician. It is not designed for permanent connection.
8. Alarm out (connector) Provides four pairs of dry contacts for an optional external
alarm-monitoring system. Normally has open contacts and
uses an RJ-45 type connector. (See Appendix B, “Connector
Pinouts.”)
9. LAN (connector) Provides Ethernet access for connecting to a remote SNMP
monitoring location, and contains two LEDs. The left LED
(green) indicates that an Ethernet connection is established.
The right LED (yellow) indicates that a signal is being trans-
mitted to the Ethernet. It uses an RJ-45 type connector.
10. Frame ground attachment Provides tapped-screw mounting holes for attaching a frame
ground lug and wiring.
11. Dual-circuit DC power input Provides two sets of DC input barrier strip terminals. The
right-hand strip terminal is for the primary DC power
wiring; the left-hand strip terminal is for an optional backup
DC power source. The left screw terminal of each strip is for
–48 VDC; the right screw terminal is for the return path.