Fluke FOM Operating and installation instructions

PN 617891
January 1997
1996 Fluke Corporation. All rights reserved. Printed in U.S.A. Product names are trademarks of their respective companies.
FOM/FOS
Fiber Optic Meter
Fiber Optic Source
Service Information
Warning
To avoid injury: do not service the FOM or FOS unless you are qualified to do so. The
service information provided in this document is for the use of qualified personnel
only.
Caution
The FOM and FOS contain parts that can be damaged by static discharge. Follow the
standard practices for handling static sensitive devices.
Introduction
This Service Information provides the following
service information for the Fiber Optic Meter
(hereafter referred to as the FOM) and the Fiber
Optic Source (hereafter referred to as the FOS).
•Parts and warranty service information
•Specifications
•Schematic
•Cleaning procedures
•Required equipment
•Performance tests
•Procedures for disassembling and reassembling
the FOM and FOS
•Calibration adjustments
•Parts and accessories lists
For operating instructions, refer to the Fiber Optic
Meter/Fiber Optic Source Instruction Sheet.
Parts and Warranty Service
The FOM and FOS are warranted to be free from
defects in material and workmanship for one year,
while under normal use. Parts and repairs are
warranted for 90 days.
Refer to the Instruction Sheet for the complete
warranty statement.
To order parts, receive operating assistance, or get
the location of the nearest Fluke distributor or
Service Center, call:
800-44FLUKE (800-443 5853) in the U.S.A. and
Canada.
(31 40) 267 8200 in Europe
+ 1 206-356-5500 from other countries
Address correspondence to:
Fluke Corporation Fluke Europe B.V.
P.O. Box 9090 P.O. Box 1186
Everett, WA 98206-9090 5602 B.D Eindhoven
U.S.A. The Netherlands
Specifications
Accuracy is specified for a period of one year after
calibration, at 18°C to 28°C (64°F to 82°F) with
relative humidity to 75%.
Specifications are shown in Tables 1 and 2.
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Advanced Test Equipment Rentals
www.atecorp.com 800-404-ATEC (2832)
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FOM/FOS
Service Information
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Table 1. FOM Specifications
Output 1 mV per 1 dB
Input Connector Type Fixed ST
Photodetector Type Germanium
Application range 800 to 1600 nm
Calibrated
Wavelengths 850, 1300, and 1550 nm
Acceptable Fiber
Types 9/125 to 100/140 µm
Operating Range +3 to -50 dBm
Maximum Power Level +5 dBm
Absolute Accuracy ±0.25 dB (specified at 25°C
-10 dBm per NIST standard)
Relative Accuracy ±0.15 dB, (specified over any
10 dB within measurement
range)
Repeatability ±0.04 dB
Battery Life 9V alkaline, NEDA 1604A or
IEC 6LR61
Battery Type 16 hours minimum, 100
hours typical, 9V alkaline
Low Battery Indication Blinking LED indicator
Operating Temperature 0°to +40°C
Storage Temperature -20°to +70°C
Humidity 0 to 40°C up to 75% RH
Table 2. FOS Specifications
Type Infrared LED
Wavelength 850 ±30 nm
1300 -40/+50 nm
850/1300 ±30 nm,
-40/+50 nm
Output power -20 dBm, nominal into
62.5/125 micron multimode
fiber
Output connector type Fixed ST
Beam divergence 0.3 radians
Pulse duration Continuous wave
Maximum output 200 µW (radiated into free
space)
Stability ±0.2 dB per 8 hours at 20°C
after 20 minute warmup
Temperature
coefficient -0.08 dB per °C, < 18°C or >
20°C
Battery Life 9V alkaline, NEDA 1604A or
IEC 6LR61
Battery Type 16 hours minimum, 24 hours
typical, 9V alkaline
Low Battery Indication Blinking LED indicator
Operating Temperature 0°to +40°C
Storage Temperature -20°to +70°C
Humidity 0 to 40°C up to 75% RH
Safety Information
CLASS I
LED PRODUCT
The FOS is rated as a class 1 LED source per
IEC 825.
General Description
The FOM measures optical power on fiber optic
cables. It indicates power loss on tested cables
using any digital multimeter (DMM) or graphical
multimeter (GMM) that has a 10 Meinput
impedance, standard diameter banana jacks, and
mVdc capability. The FOS is used as a light source
with the FOM or other fiber optic meters.
Low Battery Detection
For both the FOM and FOS, a steady, green LED
indicates a good battery. A blinking LED indicates
a low battery that needs to be replaced.
Cleaning the Optical Connector
Most problems with optical power meters and light
sources result from contaminated connectors.
Therefore, always clean the connector before
troubleshooting or calibration.
To clean the FOM or FOS ST connector, wipe the
internal portion gently with an optical-grade swab
dampened with optical-grade alcohol. To remove
loose dirt and dust from the connector, use filtered,
compressed air.
Always cover the connector with a dust cap when
the unit is not in use.
Equipment Required
The following equipment is required for servicing
the FOM:
•0-10V power supply
•Digital multimeter
•Optical power meter calibrated at 850, 1300,
and 1550 nm traceable to NIST Standards
•850 nm laser source; Po= -10 dBm
•1300 nm laser source; Po= -10 dBm
•1550 nm laser source: Po= -10 dBm
•Variable optical attenuator

Fiber Optic Meter/Source
Performance Tests
3
•2 ST/ST multimode fiber optic patch cables
The following equipment is required for servicing
the FOS:
•Calibrated FOM
•Digital multimeter
•One ST/ST multimode fiber optic patch cable
Performance Tests
Use the following performance tests to confirm that
the FOM or FOS is working properly. If the FOM
or FOS fails any of these tests, it needs calibration
adjustments or repair.
FOM -10 dBm Checkout
1. Turn on the FOM and the three light sources.
Allow the FOM to warm up for 10 minutes.
Allow the sources to warm up according to the
manufacturer’s specifications.
Perform the remaining steps using the light
sources in the following order: (1) 850 nm, (2)
1550 nm, and (3) 1300 nm.
2. Connect the light source to the reference power
meter using a fiber optic patch cable.
3. Adjust the output of the source for a power
meter reading of -10.00 ±0.05 dBm. Record this
reading as Po(power out) to use in step 5.
4. Set the FOM switch to the wavelength position
being tested.
5. Connect the FOM to the light source using the
patch cable from step 2.
Allow a few seconds for the reading to
stabilize; then verify that the reading is Po
±0.25 dBm.
6. Disconnect the light source from the FOM.
FOM -50 dBm Checkout
1. Connect the 1300 nm light source to the optical
attenuator.
Connect the attenuator to the reference power
meter using a second fiber optic patch cable.
2. Set the optical attenuator for a power meter
reading of -50.00 ±0.05 dBm. Record this
reading as Po to use in step 4.
3. Connect the FOM to the attenuator using the
patch cable connected to the reference power
meter.
4. Allow a few seconds for the reading to
stabilize; then verify that the reading is Po±0.4
dBm.
5. Turn off the DMM, FOM, and the light sources.
Disconnect the FOM from the DMM.
Disconnect the fiber optic patch cables from the
attenuator, source, and FOM.
FOS Checkout
1. Connect the FOS to the calibrated FOM with a
patch cable.
Turn the FOS on to the wavelength being tested
and let it stabilize for 20 minutes.
2. Connect the FOM to a DMM with at least
0.1 mV resolution.
Turn the FOM on and set the switch to the
wavelength being tested.
3. Verify that the FOS output is -20 ±0.5 dBm
(-19.5 to -20.5 mV on the DMM).
4. For a dual source, repeat steps 1 through 3 for
each wavelength.
Disassembling and Reassembling
the FOM and FOS
To perform calibration adjustments for the FOM
and the FOS, you must disassemble them. When
you finish the adjustments, reassemble them. A
Phillips-head screwdriver is required for
disassembling and reassembling the FOM and FOS.
To disassemble the FOM or FOS, proceed as
follows:
1. Set the FOM or FOS switch to OFF.
2. Remove the battery door; then disconnect the
battery.
3. Remove the two Phillips screws found under
the battery door; then separate the top and
bottom cases.
4. To remove the pca, remove the Phillips screw
near SW1; then lift out the pca.
To reassemble the FOM or FOS, proceed as
follows:
1. Reinsert the pca; then replace the screw that
holds the pca.
2. Tuck the battery wires into the notch at the side
of the battery compartment.

FOM/FOS
Service Information
4
3. Tuck the battery wires down against the pca so
they will not interfere with SW1.
4. Set SW1 to the off position.
5. Set the slide switch actuator on the top case to
the OFF position. For the FOS, place the
lanyard into the notch in the bottom case.
6. Put the top and bottom cases together; then
replace the two screws under the battery door.
Calibration Adjustments for the
FOM
To ensure that the FOM performs to specifications,
calibrate it annually using the procedure that
follows.
Always perform the complete calibration
adjustment procedure.
Preparing for Calibration
To prepare for calibration, proceed as follows:
1. Remove the dust cap from the FOM.
2. Connect a voltage supply of 8V ±1.0V dc to the
FOM battery strap.
3. Set the FOM switch to the 1300 nm position.
Allow the FOM to warm up for 10 minutes.
4. Allow all sources to warm up according to the
manufacturer’s specifications.
Coarse Calibration Adjustment
Refer to the FOM drawing (Figure 1) for the
locations of measurements and components.
1. Connect the 1300 nm light source to the
attenuator input.
Connect the attenuator output to the reference
power meter. Set the attenuator for 0 dB
attenuation. Set the 1300 nm light source for a
power meter reading of -10 ± 0.05 dBm.
Note
For the remaining calibration adjustments,
use the cable that was used in step 1 for
connecting the attenuator to the reference
power meter or the FOM. To reduce errors,
limit the movement of the cable when making
connections between the attenuator and the
reference power meter or the FOM. To limit
cable movement, coil and tape the excess
cable to the work surface.
2. Connect the attenuator output to the FOM.
3. Measure Vdet between U1 pin 7 and the analog
ground reference at U1 pin 5 with the DMM.
(See Figure 1.)
4. Adjust R2 for an output on the DMM of 0.23
±0.01V dc.
1300 nm Fine Calibration Adjustment
1. Connect the 1300 nm light source to the
attenuator input. Connect the attenuator output
to the reference power meter. Set the attenuator
for 0 dB attenuation. Set the 1300 nm light
source for a power meter reading of -10 ±0.05
dBm.
Record this reading as Poto use in step 3.
2. Connect the attenuator output to the FOM.
Connect the FOM to the DMM.
3. Adjust R10 for an output on the DMM of Po
±0.05 dBm.
4. Connect the attenuator output to the reference
power meter. Set the attenuator for a power
meter reading of -45 ±0.05 dBm.
Record this reading as Poto use in step 6.
5. Connect the attenuator output to the FOM.
6. Adjust R2 for an output on the DMM of Po
±0.05 dBm.
7. Repeat steps 1 through 6 until the FOM’s -10
dBm and -45 dBm readings are within
specifications.
8. Apply insulating varnish, such as red GLPT, to
the R10 and R2 potentiometers.

Fiber Optic Meter/Source
Calibration Adjustments for the FOS
5
850 nm Calibration Adjustment
1. Set the switch on the FOM to the 850 nm
position.
2. Connect the light source to the reference power
meter. Set the 850 nm light source for a power
meter reading of -10 ±0.05 dBm.
Record this level as Po to use in step 4.
3. Connect the 850 nm light source to the FOM.
Connect the FOM to the DMM.
4. Adjust R1 for an output on the DMM of Po
±0.05 dBm.
5. Apply insulating varnish, such as red GLPT, to
the R1 potentiometer.
1550 nm Calibration Adjustment
1. Set the switch on the FOM to the 1550 nm
position.
2. Connect the light source to the reference power
meter. Set the 1550 nm light source to
-10 ±0.05 dBm.
Record this reading as Poto use in step 4.
3. Connect the 1550 nm light source to the FOM.
Connect the FOM to the DMM.
4. Adjust R3 for an output on the DMM of Po
±0.05 dBm.
5. Apply insulating varnish, such as red GLPT, to
the R3 potentiometer.
At this point, the calibration adjustment is
complete.
Verifying Calibration
Follow the procedure under "Performance Tests"
earlier in this document.
Calibration Adjustments for the
FOS
Refer to the FOS drawing (Figure 2) for the
locations of components.
1. Connect the FOS to the calibrated FOM with a
patch cable. Turn the FOS on and let it stabilize
for 20 minutes.
2. Connect the FOM to a DMM with at least 0.1
mV resolution. Turn the FOM on and set it to
the desired wavelength.
3. For 850 nm calibration, adjust R21 until the
output on the DMM reads -20 ±0.1 mV. For
1300 nm calibration, adjust R20 until the output
on the DMM reads -20 ±0.1 mV.
4. Apply insulating varnish, such as red GLPT, to
each potentiometer adjusted.
Parts and Accessories
Tables 3 and 4 contain replacement parts for the
FOM and FOS that are available from Fluke. Table
5 lists available accessories.
Table 3. Fluke Replacement Parts for the FOM
Description Fluke Part Number
FOM Plastic Case Assembly 617339
Battery Door 200474
Slide Switch Actuator 200482
PD1: Germanium Photodiode, 1 mm 602788
Table 4. Fluke Replacement Parts for the FOS
Description Fluke Part Number
FOS-850 Plastic Case Assembly 617354
FOS-1300 Plastic Case Assembly 617388
FOS-850/1300 Plastic Case Assembly 617412
Battery Door 200474
Slide Switch Actuator 200482
850 LED 602755
1300 LED 602760
Table 5. Accessories for the FOM and FOS
Description Fluke Part Number
ST to ST Multimode Patch Cable, 1m 617453
ST to ST Mating Sleeve 602810
ST to FC Patch Cable 617487
ST to SC Patch Cable 617511
ST to SMA Patch Cable 616545

FOM/FOS
Service Information
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J1 (Red)
J2 (Black)
U1 Pin 7, (V
det
)
U1 Pin 5, (Analog GND)
FPM1-00-0100
eq1f.eps
Figure 1. FOM Calibration Measurement and Adjustment Points

Fiber Optic Meter/Source
Calibration Measurement and Adjustment Points
7
FLS1-01-0100
J1 (Red)
1300 Source
Components
850 Source
Components
J2 (Black)
eq2f.eps
Figure 2. FOS Calibration Adjustment Points

FOM/FOS
Service Information
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FPM1-00-0300
eq4f.eps
Figure 3. Fiber Optic Meter Schematic

Fiber Optic Meter/Source
Fiber Optic Meter Schematic
9
cut cut
FLS1-00-0300
eq3f.eps
Figure 4. Fiber Optic Source Schematic

FOM/FOS
Service Information
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