Agilent Technologies 11980A Operation manual

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Agilent 11980A
Fiber Optic Interferometer
Operation and Service Manual

ii
© Copyright
Agilent Technologies 2000
All Rights Reserved. Repro-
duction, adaptation, or trans-
lation without prior written
permission is prohibited,
except as allowed under copy-
right laws.
Agilent Part No. 11980-90012
Printed in USA
April 2000
Agilent Technologies
Lightwave Division
1400 Fountaingrove Parkway
Santa Rosa, CA 95403-1799,
USA
[phone]
Notice.
The information contained in
this document is subject to
change without notice. Com-
panies, names, and data used
in examples herein are ficti-
tious unless otherwise noted.
Agilent Technologies makes
no warranty of any kind with
regard to this material, includ-
ing but not limited to, the
implied warranties of mer-
chantability and fitness for a
particular purpose. Agilent
Technologies shall not be lia-
ble for errors contained herein
or for incidental or conse-
quential damages in connec-
tion with the furnishing,
performance, or use of this
material.
Restricted Rights Legend.
Use, duplication, or disclo-
sure by the U.S. Government
is subject to restrictions as set
forth in subparagraph (c) (1)
(ii) of the Rights in Technical
Data and Computer Software
clause at DFARS 252.227-7013
for DOD agencies, and sub-
paragraphs (c) (1) and (c) (2)
of the Commercial Computer
Software Restricted Rights
clause at FAR 52.227-19 for
other agencies.
Warranty.
This Agilent Technologies
instrument product is war-
ranted against defects in
material and workmanship for
a period of one year from date
of shipment. During the war-
ranty period, Agilent Technol-
ogies will, at its option, either
repair or replace products
which prove to be defective.
For warranty service or repair,
this product must be returned
to a service facility desig-
nated by Agilent Technolo-
gies. Buyer shall prepay
shipping charges to Agilent
Technologies and Agilent
Technologies shall pay ship-
ping charges to return the
product to Buyer. However,
Buyer shall pay all shipping
charges, duties, and taxes for
products returned to Agilent
Technologies from another
country.
Agilent Technologies war-
rants that its software and
firmware designated by Agi-
lent Technologies for use with
an instrument will execute its
programming instructions
when properly installed on
that instrument. Agilent Tech-
nologies does not warrant that
the operation of the instru-
ment, or software, or firmware
will be uninterrupted or error-
free.
Limitation of Warranty.
The foregoing warranty shall
not apply to defects resulting
from improper or inadequate
maintenance by Buyer, Buyer-
supplied software or interfac-
ing, unauthorized modifica-
tion or misuse, operation
outside of the environmental
specifications for the product,
or improper site preparation
or maintenance.
No other warranty is
expressed or implied. Agilent
Technologies specifically dis-
claims the implied warranties
of merchantability and fitness
for a particular purpose.
Exclusive Remedies.
The remedies provided herein
are buyer's sole and exclusive
remedies. Agilent Technolo-
gies shall not be liable for any
direct, indirect, special, inci-
dental, or consequential dam-
ages, whether based on
contract, tort, or any other
legal theory.
Safety Symbols.
CAUTION
The caution sign denotes a
hazard. It calls attention to a
procedure which, if not cor-
rectly performed or adhered
to, could result in damage to
or destruction of the product.
Do not proceed beyond a cau-
tion sign until the indicated
conditions are fully under-
stood and met.
WARNING
The warning sign denotes a
hazard. It calls attention to a
procedure which, if not cor-
rectly performed or adhered
to, could result in injury or
loss of life. Do not proceed
beyond a warning sign until
the indicated conditions are
fully understood and met.
The instruction man-
ual symbol. The prod-
uct is marked with this
warning symbol when
it is necessary for the
user to refer to the
instructions in the
manual.
The laser radiation
symbol. This warning
symbol is marked on
products which have a
laser output.
The AC symbol is used
to indicate the
required nature of the
line module input
power.
|The ON symbols are
used to mark the posi-
tions of the instrument
power line switch.
❍The OFF symbols
are used to mark the
positions of the instru-
ment power line
switch.
The CE mark is a reg-
istered trademark of
the European Commu-
nity.
The CSA mark is a reg-
istered trademark of
the Canadian Stan-
dards Association.
The C-Tick mark is a
registered trademark
of the Australian Spec-
trum Management
Agency.
This text denotes the
instrument is an
Industrial Scientific
and Medical Group 1
Class A product.
Typographical Conven-
tions.
The following conventions are
used in this book:
Key type for keys or text
located on the keyboard or
instrument.
Softkey type for key names that
are displayed on the instru-
ment’s screen.
Display type for words or
characters displayed on the
computer’s screen or instru-
ment’s display.
User type for words or charac-
ters that you type or enter.
Emphasis type for words or
characters that emphasize
some point or that are used as
place holders for text that you
type.
ISM1-A

iii
General Safety Considerations
General Safety Considerations
This product has been designed and tested in accordance with IEC Publica-
tion 61010-1, Safety Requirements for Electrical Equipment for Measurement,
Control and Laboratory Use, and has been supplied in a safe condition. The
instruction documentation contains information and warnings that must be
followed by the user to ensure safe operation and to maintain the product in a
safe condition.
WARNING If this instrument is not used as specified, the protection provided by
the equipment could be impaired. This instrument must be used in a
normal condition (in which all means for protection are intact) only.
WARNING No operator serviceable parts inside. Refer servicing to qualified
personnel. To prevent electrical shock, do not remove covers.
WARNING To prevent electrical shock, disconnect the Agilent 11980A from
mains before cleaning. Use a dry cloth or one slightly dampened with
water to clean the external case parts. Do not attempt to clean
internally.
WARNING This is a Safety Class 1 product (provided with a protective earthing
ground incorporated in the power cord). The mains plug shall only be
inserted in a socket outlet provided with a protective earth contact.
Any interruption of the protective conductor inside or outside of the
product is likely to make the product dangerous. Intentional
interruption is prohibited.
WARNING For continued protection against fire hazard, replace line fuse only
with same type and ratings, (type T 0.315A/250V for 100/120V
operation and 0.16A/250V for 220/240V operation). The use of other
fuses or materials is prohibited. Verify that the value of the line-
voltage fuse is correct.
•For 100/120V operation, use an IEC 127 5×20 mm, 0.315 A, 250 V, Agilent
part number 2110-0449.
•For 220/240V operation, use an IEC 127 5×20 mm, 0.16 A, 250 V, Agilent
Technologies part number 2110-0448.

iv
General Safety Considerations
CAUTION Before switching on this instrument, make sure that the line voltage selector
switch is set to the line voltage of the power supply and the correct fuse is
installed. Assure the supply voltage is in the specified range.
CAUTION This product is designed for use in Installation Category II and Pollution
Degree 2 per IEC 1010 and 664 respectively.
CAUTION VENTILATION REQUIREMENTS: When installing the product in a cabinet, the
convection into and out of the product must not be restricted. The ambient
temperature (outside the cabinet) must be less than the maximum operating
temperature of the product by 4°C for every 100 watts dissipated in the
cabinet. If the total power dissipated in the cabinet is greater than 800 watts,
then forced convection must be used.
CAUTION Always use the three-prong ac power cord supplied with this instrument.
Failure to ensure adequate earth grounding by not using this cord may cause
instrument damage.
CAUTION Do not connect ac power until you have verified the line voltage is correct.
Damage to the equipment could result.
CAUTION This instrument has autoranging line voltage input. Be sure the supply voltage
is within the specified range.
Measurement accuracy—it’s up to you!
Fiber-optic connectors are easily damaged when connected to dirty or damaged cables
and accessories. The Agilent 11980A front-panel OPTICAL OUT connector is no excep-
tion. When you use improper cleaning and handling techniques, you risk expensive
instrument repairs, damaged cables, and compromised measurements.
Before you connect any fiber-optic cable to the Agilent 11980A, refer to “Cleaning Con-
nections for Accurate Measurements” on page 3-3.

Contents
Contents-1
1 General Information
Description 1-2
Options 1-3
Initial Inspection 1-4
Returning the Instrument for Service 1-5
Preparing the instrument for shipping 1-5
Agilent Technologies Service Offices 1-8
2 Specifications
Specifications 2-2
3 User Precautions
Front-Panel Knob 3-2
Connector Care 3-2
Cleaning Connections for Accurate Measurements 3-3
Choosing the Right Connector 3-3
Inspecting Connectors 3-6
Cleaning Connectors 3-10
4Operation
Theory of Operation 4-2
Applications 4-3
Static Linewidth Measurement 4-3
Chirp and FM Measurements 4-5
5 Operation Verification
Operation Verification 5-2
Optical Insertion Loss Test 5-3
Interferometric Test 5-5
6 Replaceable Parts
Replaceable Parts 6-2

1
Description 1-2
Options 1-3
Initial Inspection 1-4
Returning the Instrument for Service 1-5
Agilent Technologies Service Offices 1-8
General Information

1-2
General Information
Description
Description
The Agilent 11980A fiber optic interferometer is a Mach Zehnder interferome-
ter built with a fixed length of single-mode optical fiber. The Agilent 11980A
splits the optical energy into two paths, delaying one path with respect to the
other, and recombines them in a second optical coupler. A polarization adjust-
ment helps align the optical fields for maximum interference, as shown in
Figure 1-1.
The Agilent 11980A is a lightwave accessory for use with the Agilent 71400C,
71401C, and 83810A lightwave signal analyzers. The Agilent 11980A allows
you to measure linewidth, chirp, and FM characteristics of single-line lasers.
Figure 1-1. Agilent 11980A Fiber Optic Interferometer, Simplified Schematic

1-3
General Information
Options
Options
Several options are available when ordering the Agilent 11980A.
•Option 005 lengthens the delay line from 760 meters to 5.2 kilometers, al-
lowing measurement of narrower linewidths.
•Options 011 through 015 allow you to order your choice of several optical
connector interfaces. This makes it simple to interface to your connector
standard. Table 1-1 lists the available connector interface families.
Table 1-1. Agilent 11980A Connector Options
Option Agilent Part Numbera
a. Includes dust cap.
Interface Standard
011 81000AI HMS-10
012 81000FI FC/PC
013 81000SI DIN 47256
014 81000VI ST
015 81000WI Biconic

1-4
General Information
Initial Inspection
Initial Inspection
If the shipment contents are incomplete or damaged, refer to “Returning the
Instrument for Service”on page 1-5. If the shipping container is damaged, or
the cushioning material shows signs of stress, notify the carrier as well as the
Agilent Technologies office. Refer to “Agilent Technologies Service Offices”on
page 1-8. Keep the shipping materials for the carrier’s inspection. Agilent
Technologies will arrange for repair or replacement without waiting for a claim
settlement.

1-5
General Information
Returning the Instrument for Service
Returning the Instrument for Service
The instructions in this section show you how to properly return the instru-
ment for repair or calibration. Always call the Agilent Technologies Instrument
Support Center first to initiate service before returning your instrument to a
service office. This ensures that the repair (or calibration) can be properly
tracked and that your instrument will be returned to you as quickly as possi-
ble. Call this number regardless of where you are located. Refer to “Agilent
Technologies Service Offices”on page 1-8 for a list of service offices.
Agilent Technologies Instrument Support Center. . . . . . . . . . . [phone]
If the instrument is still under warranty or is covered by an Agilent Technolo-
gies maintenance contract, it will be repaired under the terms of the warranty
or contract (the warranty is at the front of this manual). If the instrument is
no longer under warranty or is not covered by an Agilent Technologies mainte-
nance plan, Agilent Technologies will notify you of the cost of the repair after
examining the unit.
When an instrument is returned to a Agilent Technologies service office for
servicing, it must be adequately packaged and have a complete description of
the failure symptoms attached. When describing the failure, please be as spe-
cific as possible about the nature of the problem. Include copies of additional
failure information (such as the instrument failure settings, data related to
instrument failure, and error messages) along with the instrument being
returned.
Preparing the instrument for shipping
1Write a complete description of the failure and attach it to the instrument.
Include any specific performance details related to the problem. The following

1-6
General Information
Returning the Instrument for Service
information should be returned with the instrument.
•Type of service required.
•Date instrument was returned for repair.
•Description of the problem:
•Whether problem is constant or intermittent.
•Whether instrument is temperature-sensitive.
•Whether instrument is vibration-sensitive.
•Instrument settings required to reproduce the problem.
•Performance data.
•Company name and return address.
•Name and phone number of technical contact person.
•Model number of returned instrument.
•Full serial number of returned instrument.
•List of any accessories returned with instrument.
2Cover all front or rear-panel connectors that were originally covered when you
first received the instrument.
CAUTION Cover electrical connectors to protect sensitive components from electrostatic
damage. Cover optical connectors to protect them from damage due to physical
contact or dust.
CAUTION Instrument damage can result from using packaging materials other than the
original materials. Never use styrene pellets as packaging material. They do not
adequately cushion the instrument or prevent it from shifting in the carton.
They may also cause instrument damage by generating static electricity.
3Pack the instrument in the original shipping containers. Original materials are
available through any Agilent Technologies office. Or, use the following
guidelines:
•Wrap the instrument in antistatic plastic to reduce the possibility of damage
caused by electrostatic discharge.
•For instruments weighing less than 54 kg (120 lb), use a double-walled, cor-
rugated cardboard carton of 159 kg (350 lb) test strength.
•The carton must be large enough to allow approximately 7 cm (3 inches) on
all sides of the instrument for packing material, and strong enough to accom-
modate the weight of the instrument.
•Surround the equipment with approximately 7 cm (3 inches) of packing ma-
terial, to protect the instrument and prevent it from moving in the carton. If
packing foam is not available, the best alternative is S.D-240 Air Cap™from

1-7
General Information
Returning the Instrument for Service
Sealed Air Corporation (Commerce, California 90001). Air Cap looks like a
plastic sheet filled with air bubbles. Use the pink (antistatic) Air Cap™to
reduce static electricity. Wrapping the instrument several times in this ma-
terial will protect the instrument and prevent it from moving in the carton.
4Seal the carton with strong nylon adhesive tape.
5Mark the carton “FRAGILE, HANDLE WITH CARE”.
6Retain copies of all shipping papers.

1-8
General Information
Agilent Technologies Service Offices
Agilent Technologies Service Offices
Before returning an instrument for service, call the Agilent Technologies
Instrument Support Center at [phone], visit the Test and Measurement
Web Sites by Country page at http://www.tm.agilent.com/tmo/country/English/
index.html, or call one of the numbers listed below.
Agilent Technologies Service Numbers
Austria 01/25125-7171
Belgium 32-2-778.37.71
Brazil (11) 7297-8600
China 86 10 6261 3819
Denmark 45 99 12 88
Finland 358-10-855-2360
France 01.69.82.66.66
Germany 0180/524-6330
India 080-34 35788
Italy [phone]
Ireland 01 615 8222
Japan (81)-426-56-7832
Korea 82/2-3770-0419
Mexico (5) 258-4826
Netherlands 020-547 6463
Norway 22 73 57 59
Russia [phone]
Spain (34/91) 631 1213
Sweden 08-5064 8700
Switzerland [phone]
United Kingdom 01 344 366666
United States and Canada [phone]

2
Specifications

2-2
Specifications
Specifications
Specifications
Table 2-1 lists specifications for the Agilent 11980A. An asterisk (*) placed
after an entry indicates that it is a supplemental characteristic. Characteristics
are not specifications; they are included as additional information for the user.
Table 2-1. Agilent 11980A Specifications
Optical Insertion Loss < 8 dB at 1320 nm
< 8 dB at 1550 nm
Wavelength Range* 1250 nm to 1600 nm
Delay Time* 3.5
µ
s
Delay Time, Option 005* 25
µ
s
Connectors Single-mode optical
Maximum Input Power
as limited by lightwave analyzer*
250 mW
Temperature Range Operating: 0°C to 55°C
Storage: –40°C to 75°Ca
a. Unmated condition; at temperatures above 55°C, connectors will be damaged if mated.
Weight* Net: 1.9 kg (4.2 lb)
Shipping: 3.2 kg (7 lb)
Weight, Option 005* Net: 2.3 kg (5 lb)
Shipping: 3.5 kg (7.8 lb)
Maximum Dimensions 105 mm H ×215 mm W ×290 mm L
(4.1 in H ×8.5 in W ×11.4 in L)

3
Front-Panel Knob 3-2
Connector Care 3-2
Cleaning Connections for Accurate Measurements 3-3
User Precautions

3-2
User Precautions
Front-Panel Knob
Front-Panel Knob
CAUTION The front-panel polarization adjust knob will break if it is turned with too much
force. Do not continue to turn the knob past its stops.
Connector Care
CAUTION Do not touch the tips of the front-panel input or output connectors. The optical
interface of the Agilent 11980A is composed of precision-polished single-mode
connectors that are easily scratched. Any damage to the optical interface will
increase the insertion loss of the Agilent 11980A and damage the connector
interfaces.
The precautions listed below will help prevent fiber damage and help ensure
accurate measurements.
•Before any mating of fiber-optic tips, clean the tips to assure that no dust or
other particles adhere to them. Refer to “Cleaning Connections for Accurate
Measurements”on page 3-3 for further information.
•Always replace protective dust caps on any exposed fiber-optic tip.

3-3
User Precautions
Cleaning Connections for Accurate Measurements
Cleaning Connections for Accurate
Measurements
Today, advances in measurement capabilities make connectors and connec-
tion techniques more important than ever. Damage to the connectors on cali-
bration and verification devices, test ports, cables, and other devices can
degrade measurement accuracy and damage instruments. Replacing a dam-
aged connector can cost thousands of dollars, not to mention lost time! This
expense can be avoided by observing the simple precautions presented in this
book. This book also contains a brief list of tips for caring for electrical connec-
tors.
Choosing the Right Connector
A critical but often overlooked factor in making a good lightwave measure-
ment is the selection of the fiber-optic connector. The differences in connec-
tor types are mainly in the mechanical assembly that holds the ferrule in
position against another identical ferrule. Connectors also vary in the polish,
curve, and concentricity of the core within the cladding. Mating one style of
cable to another requires an adapter. Agilent Technologies offers adapters for
most instruments to allow testing with many different cables. Figure 3-1 on
page 3-4 shows the basic components of a typical connectors.
The system tolerance for reflection and insertion loss must be known when
selecting a connector from the wide variety of currently available connectors.
Some items to consider when selecting a connector are:
•How much insertion loss can be allowed?
•Will the connector need to make multiple connections? Some connectors are
better than others, and some are very poor for making repeated connections.
•What is the reflection tolerance? Can the system take reflection degradation?
•Is an instrument-grade connector with a precision core alignment required?
•Is repeatability tolerance for reflection and loss important? Do your specifica-