MAN-VLC
Operator's Manual
Fiberoptic Transmitter
Model 3120A/10357A
10-200 MHz
Fiberoptic Receiver
Model 4120A/10457A
10-200 MHz
2015 West Chestnut Street
Alhambra, California 91803
www.ortel.com
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
File: G:\EDC\DOCSRLSD\MAN\VLC-IF\Ifman_cv_F.doc
Rev. F
July 26, 1999
Operating Manual
IF Fiberoptic Link
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
Operating Manual
IF Fiberoptic Link
Disclaimer
Every attempt has been made to make this material complete, accurate, and up-to-date. Users are cautioned,
however, that Ortel Corporation reserves the right to make changes without notice and shall not be responsible for
any damages, including consequential, caused by reliance on the material presented, including, but not limited to,
typographical, arithmetical, or listing errors.
Copyright Information
© 1999 by Ortel Corporation
Ortel Corporation
Alhambra, California, 91803, USA
www.ortel.com
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
Operating Manual
IF Fiberoptic Link
WARNINGS, CAUTIONS, AND GENERAL NOTES
Safety Considerations
When installing or using this product, observe all safety precautions during handling and operation.
Failure to comply with the following general safety precautions and with specific precautions described
elsewhere in this manual violates the safety standards of the design, manufacture, and intended use of this
product. Ortel Corporation assumes no liability for the customer's failure to comply with these precautions.
Calls attention to a procedure or practice which, if ignored, may result in damage to the system or
system component. Do not perform any procedure preceded by a CAUTION until the described
conditions are fully understood and met.
Electrostatic Sensitivity
ESD = Electrostatic Sensitive Device
Observe electrostatic precautionary procedures.
Semiconductor laser transmitters and receivers provide highly reliable performance when operated in
conformity with their intended design. However, a semiconductor laser may be damaged by an
electrostatic charge inadvertently imposed by careless handling.
Static electricity can be conducted to the laser or photodiode chip from the center pin of the RF connector,
and through the DC connector pins. When unpacking and otherwise handling the transmitter or receiver,
follow ESD precautionary procedures including use of grounded wrist straps, grounded workbench
surfaces, and grounded floor mats.
Susceptibility to electrostatic discharge is greatly reduced after the transmitter or receiver has been installed
in an operational circuit.
If You Need Help
If you need additional help in installing or using the system, need additional copies of this manual, or have
questions about system options, please call Ortel's Sales Department.
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Ortel Corporation
Model 3120A/10357A Transmitter
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Operating Manual
IF Fiberoptic Link
Service
Do not attempt to modify or service any part of the system other than in accordance with procedures
outlined in this Operator's Manual. If the system does not meet its warranted specifications, or if a problem
is encountered that requires service, return the apparently faulty plug-in or assembly to Ortel for evaluation
in accordance with Ortel's warranty policy.
When returning a plug-in or assembly for service, include the following information: Owner, Model
Number, Serial Number, Return Authorization Number (obtained in advance from Ortel Corporation's
Customer Service Department), service required and/or a description of the problem encountered.
Warranty and Repair Policy
The Ortel Corporation Quality Plan includes product test and inspection operations to verify the quality
and reliability of our products.
Ortel uses every reasonable precaution to ensure that every device meets published electrical, optical, and
mechanical specifications prior to shipment. Customers are asked to advise their incoming inspection,
assembly, and test personnel as to the precautions required in handling and testing ESD sensitive optoelectronic components.
These products are covered by the following warranties:
1.
General Warranty
Ortel warrants to the original purchaser all standard products sold by Ortel to be free of defects in
material and workmanship for one (1) year from date of shipment from Ortel. During the
warranty period, Ortel's obligation, at our option, is limited to repair or replacement of any
product that Ortel proves to be defective. This warranty does not apply to any product which has
been subject to alteration, abuse, improper installation or application, accident, electrical or
environmental over-stress, negligence in use, storage, transportation or handling.
2.
Specific Product Warranty Instructions
All Ortel products are manufactured to high quality standards and are warranted against defects in
workmanship, materials and construction, and to no further extent. Any claim for repair or
replacement of a device found to be defective on incoming inspection by a customer must be
made within 30 days of receipt of the shipment, or within 30 days of discovery of a defect within
the warranty period.
This warranty is the only warranty made by Ortel and is in lieu of all other warranties, expressed
or implied, except as to title, and can be amended only by a written instrument signed by an
officer of Ortel. Ortel sales agents or representatives are not authorized to make commitments on
warranty returns.
In the event that it is necessary to return any product against the above warranty, the following
procedure shall be followed:
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Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
Operating Manual
IF Fiberoptic Link
a.
Return authorization shall be received from the Ortel Sales Department prior to returning
any device. Advise the Ortel Sales Department of the model, serial number, and the
discrepancy. The device shall then be forwarded to Ortel, transportation prepaid.
Devices returned freight collect or without authorization may not be accepted.
b.
Prior to repair, Ortel Sales will advise the customer of Ortel test results and will advise
the customer of any charges for repair (usually for customer caused problems or out-ofwarranty conditions).
If returned devices meet full specifications and do not require repair, or if non-warranty
repairs are not authorized by the customer, the device may be subject to a standard
evaluation charge. Customer approval for the repair and any associated costs will be the
authority to begin the repair at Ortel. Customer approval is also necessary for any
removal of certain parts, such as connectors, which may be necessary for Ortel testing or
repair.
c.
3.
Repaired products are warranted for the balance of the original warranty period, or at
least 90 days from date of shipment.
Limitations of Liabilities
Ortel's liability on any claim of any kind, including negligence, for any loss or damage arising
from, connected with, or resulting from the purchase order, contract, or quotation, or from the
performance or breach thereof, or from the design, manufacture, sale, delivery, installation,
inspection, operation or use of any equipment covered by or furnished under this contract, shall in
no case exceed the purchase price of the device which gives rise to the claim.
EXCEPT AS EXPRESSLY PROVIDED HEREIN, ORTEL MAKES NO WARRANTY OF
ANY KIND, EXPRESSED OR IMPLIED, WITH RESPECT TO ANY GOODS, PARTS
AND SERVICES PROVIDED IN CONNECTION WITH THIS AGREEMENT
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. ORTEL
SHALL NOT BE LIABLE FOR ANY OTHER DAMAGE INCLUDING, BUT NOT
LIMITED TO, INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES ARISING
OUT OF OR IN CONNECTION WITH FURNISHING OF GOODS, PARTS AND
SERVICE HEREUNDER, OR THE PERFORMANCE, USE OF, OR INABILITY TO USE
THE GOODS, PARTS AND SERVICE.
Ortel will not be responsible for loss of output or reduced output of opto-electronic devices if the
customer performs chip mounting, ribbon bonding, wire bonding, fiber coupling, fiber
connectorization, or similar operations. These processes are critical and may damage the device
or may affect the device's output or the fiber output.
Ortel test reports or data indicating mean-time-to-failure, mean-time-between-failure, or other
reliability data are design guides and are not intended to imply that individual products or samples
of products will achieve the same results. These numbers are to be used as management and
iii
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
Operating Manual
IF Fiberoptic Link
engineering tools, and are not necessarily indicative of expected field operation. These numbers
assume a mature design, good parts, and no degradation of reliability due to manufacturing
procedures and processes.
Ortel is not liable for normal laser output degradation or fiber coupling efficiency degradation
over the life of the device.
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Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
Operating Manual
IF Fiberoptic Link
DANGER
This fiberoptic laser transmitter contains a class IIIb laser product as defined by the U.S. Department of Health and
Human Services, Public Health Service, Food and Drug Administration. This laser product complies with 21 CFR,
Chapter I, Subchapter J of the DHEW standards under the Radiation Control for Health and Safety Act of 1968.
The laser module certification label is located on the top of the transmitter enclosure and it also shows the required
DANGER warning logotype (as shown below).
The Ortel laser products are used in optical fiber communications systems for radio frequency and microwave
frequency analog fiberoptic links. In normal operation, these systems are fully enclosed and fully shielded by the
hermetically sealed laser metal package. Laser bias current is limited by the internal control circuitry. The
transmitters are coupled to glass fiber and have 1300 nm optical output wavelength with typically 0.5 to 7.0mW
output depending on the model. The optical radiation is confined to the fiber core. Under these conditions, there is
no accessible laser emission and hence no hazard to safety or health. Variations in the different models reflect the
bandwidth, optical output, noise, and distortion of the laser.
Since there is no human access to the laser output during system operation, no special operator precautions are
necessary when fiber is connected to the transmitter and receiver. During installation, service, or maintenance, the
service technician is warned, however, to take precautions which include not looking directly into the fiber
connector or the fiber which is connected to the fiber connector before it is connected to the fiberoptic
receiver. The light emitted from the fiberoptic connector or any fiber connected to the connector is invisible
and may be harmful to the human eye. Use either an infrared viewer or fluorescent screen for optical output
verification. All handling precautions as outlined by the FDA and ANSI Z136.2 and other authorities of class
IIIb lasers must be observed.
Do not attempt to modify or to service the laser transmitter. Return it to Ortel Corporation for service and
repair. Contact the Ortel Corporation Customer Service Department for a return authorization if service is
necessary.
DANGER
INVISIBLE LASER RADIATION
AVOID DIRECT EXPOSURE TO BEAM
PEAK POWER 30 mW
WAVELENGTH 1300/1550 nm
CLASS IIIb LASER PRODUCT
THIS PRODUCT COMPLIES WITH 21 CFR
CHAPTER I SUBCHAPTER J
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Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
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Operating Manual
IF Fiberoptic Link
TABLE OF CONTENTS
CHAPTER 1 TYPICAL APPLICATIONS & GENERAL FEATURES ................................ 2
1.1
1.2
FIBEROPTIC LINK............................................................................................................................................3
OPTIONAL FEATURES .....................................................................................................................................3
CHAPTER 2 RF PERFORMANCE. .......................................................................................... 5
2.1
RF AND ENVIRONMENTAL SPECIFICATIONS ...................................................................................................5
CHAPTER 3 DC POWERING, MONITORS, AND ALARMS .............................................. 6
3.1
DC ELECTRICAL POWER REQUIREMENTS .......................................................................................................6
3.2
DC INPUTS/OUTPUTS .....................................................................................................................................6
3.2.1
Flange-mount Module............................................................................................................................6
3.2.2
10K Plug-in Module...............................................................................................................................8
3.2.2.1.
Model 10990A chassis & power supply monitoring and connections ........................................................... 9
CHAPTER 4 FIBEROPTIC COMPONENTS ........................................................................ 10
4.1
4.2
4.3
4.4
4.5
OPTICAL SPECIFICATIONS .............................................................................................................................10
OPTICAL FIBER BASICS ................................................................................................................................10
OPTICAL FIBER .............................................................................................................................................11
OPTICAL CONNECTORS.................................................................................................................................11
DETECTING OPTICAL POWER........................................................................................................................13
CHAPTER 5 INSTALLATION ................................................................................................ 15
5.1
5.2
5.3
5.4
CHECKLIST FOR UNPACKING CARTONS ........................................................................................................15
INSTALLING FLANGE-MOUNT MODULES IN THE OUTDOOR NEMA ENCLOSURE ..........................................16
INSTALLING FLANGE-MOUNT MODULES IN THE 1U RACK MOUNT CHASSIS ................................................17
INSTALLING 10K PLUG-IN STYLE MODULES IN THE 3U RACK MOUNT CHASSIS ..........................................20
CHAPTER 6 OPTIMIZING RF PERFORMANCE............................................................... 21
6.1
6.2
LINK GAIN ....................................................................................................................................................21
COMMON LINK PERFORMANCE PARAMETERS ..............................................................................................21
CHAPTER 7 TROUBLESHOOTING AND MAINTENANCE ............................................ 23
7.1
7.2
7.3
7.4
7.5
LOW OR NONEXISTENT RF GAIN ..................................................................................................................23
HIGH NOISE OR INTERMODULATION DISTORTION ........................................................................................23
LOW OPTICAL POWER AT THE RECEIVER .....................................................................................................23
DC CIRCUIT VERIFICATION ..........................................................................................................................24
FUSE REPLACEMENT ....................................................................................................................................24
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
2
Operating Manual
IF Fiberoptic Link
Chapter 1 Typical Applications & General Features
The 3120A/10357A series fiberoptic transmitter and the 4120A/10457A series fiberoptic receiver, connected with a
single mode fiberoptic cable, make up an interfacility link (IFL) designed for use in satellite earth terminals. The
3120A/10357A, 4120A/10457A link covers the frequency range 10MHz to 200MHz and replaces the traditional
coaxial cable link between the earth station's outdoor unit at the antenna and the indoor unit (receiver, modem, etc.).
The specifications and options are designed to satisfy the requirements for use in earth terminals for:



VSAT - One Way
VSAT - Two Way
In-building IF extension
Refer to the block diagrams in Figure 1-1 for examples of these typical applications.
Transceiver
Fiberoptic
Tx
Downconverter
Fiberoptic
Rx
Modem
Upconverter
Fiberoptic
Rx
Fiberoptic
Tx
Transmit and Receive
Downconverter
Fiberoptic
Tx
Fiberoptic
Rx
Modem
Receive Only
Upconverter
Fiberoptic
Rx
Fiberoptic
Tx
Modem
Transmit Only
Figure 1-1
Typical applications of the Ortel IF-band IFL.
Both the 3120A and the 4120A models are flange-mount modules which are designed for mounting in
outdoor NEMA box enclosures, in a 1U high, 19 inch rack mount chassis (here, "U" indicates rack unit which, in a
standard 19" rack, is equivalent to 1.75"), or in other small spaces. For DC powering, these units take bias voltage
via wire leads. In an outdoor environment the wire leads should be connected using silicone-filled wire nuts for
waterproofing and the RF and optical connectors should be potted with RTV (the optical connectors are not to be
potted with silicone as it can harm optical fiber).
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
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Operating Manual
IF Fiberoptic Link
The model 10357A and 10457A units are designed specifically to mount in Ortel's System 10000 rack
mount chassis. This chassis (Model 10990A) is a 3U high 19" rack mountable unit which can hold up to 8 plug-in
modules. It is intended for indoor applications and can be powered easily from standard AC inputs via the Model
10901 power supply.
1.1
Fiberoptic Link
At the heart of the fiberoptic link is a wideband, uncooled, directly modulated laser transmitting an optical
signal to a photodiode receiver. The laser is biased with a DC current, on top of which is modulated the RF signal
from the satcom link. This produces an intensity modulation of the optical output, as demonstrated in Figure 1-2.
The modulated light from the laser is then coupled into the fiber. At the other end of the fiber, a semiconductor PIN
photodiode converts this optical signal into an electrical current which is amplified and delivered to the output load,
The resulting signal is a recovered copy of the original RF signal.
1.2
Optional Features
In addition to the primary packaging and frequency range features, other options are available, as listed in
Table 1-2 and shown in Figures 1-3 and 1-4. The readily available options are module gain and characteristic
impedance. For example, the amount of amplification in the standard transmitter and receiver was designed to
provide an overall RF link gain of 0dB when implemented with an optical loss of 1dB; and to provide roughly
equivalent S/N and C/I when the total input power is near -27dBm. However, for those applications with higher
power input signals, or where a different link gain is required, option 102 may be used (as detailed in chapter 2.)
Figure 1-2
Heart of a fiberoptic link—conversion of electrical and optical RF signals.
Table 1-1
Option
Designator
Option
Availability
Flange
Plug-in
101
X
X
102
X
X
IF-BAND OPTIONS
Option Description
50 characteristic impedance with
BNC female connector.
For higher signal input.
Tx: Single stage of amplification.
Rx: Two stages of amplification.
Standard Configuration
75 BNC connector, female.
Tx: Two stages of amplification.
Rx: Single stage of amplification.
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
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Operating Manual
IF Fiberoptic Link
POWER LED
Alarm/
monitors
(Flange mount only)
LED
Power on indicator
(10k plug-in only)
DC INPUT
Regulator/
bias

Laser
Matching
RF Input

Figure 1-3
Fiber
output
Laser
IF-band transmitter block diagram. Standard gain configuration is shown.
Low gain model (option 102) has a single stage pre-amplifier.
PDIM
POWER LED
Alarm/
monitors
DC INPUT
(flange mount only)
ALARM
LED
Power on LED
(10k plug-in only)
Regulator/
bias
PD
Matching
Fiber
input
Figure 1-4
Photodiode
LED
Optical power
indicator (10k plug-in only)

RF Output

IF-band receiver block diagram. High gain (option 102) configuration is
shown. Standard gain model has a single stage pre-amplifier.
Ortel Corporation
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Model 4120A/10457A Receiver
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Operating Manual
IF Fiberoptic Link
Chapter 2 RF Performance.
Since the fiberoptic link has an analog RF input and output, its performance can be specified and analyzed
like any RF component, with parameters such as noise figure, third order intercept (IP3), VSWR, etc. The main
caveat is that the optical loss and the specific choice of transmitter and receiver must be known. In the tables below,
the worst case RF performance has been specified for the case of 1dB of optical loss. Some units may have gain
much higher than that listed below.
If the optical loss is greater than 1dB, the RF gain will drop 2dB for each additional 1dB of optical loss and
the noise figure will begin to degrade. (For example, a standard gain link with 2dB of optical loss would have an RF
gain of –2dB, while the same link with 1dB optical loss would have 0dB.) The exact amount of noise degradation
will depend on the optical back reflections and length of the fiber, but as a rough rule of thumb, the noise will stay
fairly close to the value for 1dB optical loss up to about 3-4dB of optical loss, and then begin degrading about 2dB
for each additional 1dB of optical loss. For high optical losses, optical back-reflections also must be minimized to
avoid degrading the C/I. This generally means that these IF-band transmitters will work well with quality optical
splitters and connectors, but may suffer some RF degradation when used with fibers with lengths upwards of several
kilometers. Chapter 4 describes in greater detail the use of fiberoptic components with these links.
2.1
RF and Environmental Specifications
When optimizing the RF performance, the main concern involves setting the input RF signal level. A
detailed analysis may be carried out using Table 2-2 below, or as another rough rule of thumb, the optimal total RF
power into the transmitter should be near –27dBm for a standard gain transmitter and –10dBm for a low gain unit.
Due to the dynamic range of these links, the RF power can deviate some from this optimal level and still provide
good results. For specific examples of optimizing links, see Chapter 6.
Table 2-1
RF SPECIFICATIONS
For complete link of Tx, Rx, 1dB optical loss, & >60dB optical return loss
Tx gain option
Std.
-102 (low)
Std.
-102 (low)
Rx gain option
Std.
-102 (high)
-102 (high)
Std.
Link gain (at 25C), min.
0dB
0dB
+15.0dB
-15.0dB
Amplitude flatness
full band
0.5dB
0.5dB
0.5dB
0.5dB
any 40MHz
0.25dB
0.25dB
0.25dB
0.25dB
Noise figure, max.
28dB
43dB
28dB
43dB
Input IP3, min.
(Tx to -20C)
0dBm
+5dBm
-10dBm
+15dBm
Input 1dB compression
(Tx to -20C)
 -10dBm
 -5dBm
 -20dBm
 +5dBm
(typical)
Gain vs. temperature
Tx
0.07dB/C
0.06dB/C
0.07dB/C
0.06dB/C
(typical)
Rx
0.06dB/C
0.07dB/C
0.07dB/C
0.06dB/C
VSWR
(input/output)
1.5 : 1
1.5 : 1
1.5 : 1
1.5 : 1
Maximum RF input (Tx)
-8dBm
+7dBm
-8dBm
+7dBm
In/out impedance
75 BNC, female (50 BNC, option 101)
Table 2-2
Operating Temperature
Storage Temperature
ENVIRONMENTAL SPECIFICATIONS
Flange-mount
Transmitter
Receiver
-20 to +60C
-40 to +60C
-45 to +85C
10K style Plug-in
0 to +50C
-45 to +85C
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Operating Manual
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Chapter 3 DC Powering, Monitors, and Alarms
3.1
DC Electrical Power Requirements
The fiberoptic transmitters (Tx) and receivers (Rx) described in this manual require a DC bias input of
+12V to +24V and a current as specified in Table 3-1.
Table 3-1
MAXIMUM CURRENT REQUIREMENTS
Input voltage
12V
15V*
18V
24V
Transmitter
170mA
135mA
115mA
85mA
Receiver
150mA
120mA
100mA
70mA
*+15V may be provided by Ortel Model 10901A or 10901B power supplies.

Ripple & Noise Requirement: 20mVp-p below 100kHz, 100mVp-p above 100kHz
Table 3-2
Product
3120A, 10357A (Tx)
4120A, 10457A (Rx)
3.2
DC Inputs/Outputs
3.2.1
Flange-mount Module
MAX. CURRENT REQUIREMENTS
Standard gain
250mA
250mA
Gain option -102
350mA
150mA
The flange-mount packages possess 5 flying leads which carry the DC input voltage and the alarms and
status monitors listed in Table 3-3 below. Any unused wires should be wrapped with electrical tape to avoid short
circuits. The Ortel provided 1U high rack mount chassis or NEMA-style enclosure both include terminal strips for
these leads. Chapter 5 contains detailed procedures for installing units in these boxes.
Table 3-3
Lead
Color
Red
Brown
Black
Orange
Yellow
FLANGE-MOUNT DC LEADS
Tx, IF-band, Flange-mount
Signal
Description
DC INPUT
+12-24VDC
GND
DC return.
GND
DC return.
POWER LED Output capable of driving an
LED for remote monitoring
purposes. Indicates presence of
regulated DC voltage in the unit.
GND
DC return.
Rx, IF-band, Flange-mount
Signal
Description
DC INPUT
12-24VDC
ALARM
Low received optical power.
GND
DC return.
POWER LED Output capable of driving an
LED for remote monitoring
purposes. Indicates presence of
regulated DC voltage in the unit.
PDIM
Photodiode current monitor.
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Operating Manual
IF Fiberoptic Link
Vcc
ALARM
R
Tx
+6.5V
432
Vcc
R
Figure 3-1
Normal condition: transistor ON, ALARM  0V
Alarm condition: transistor OFF, ALARM  Vcc
Rx
+10V
825
ALARM circuit for both flange-mount and plug-in style IF-band receivers.
Transistor switches at approximately 0.1mW received optical power.
.13 DIA SLOTTED
for #6 SCREW
2.40"
1.80"
2.88"
4.45"
5.08"
5.29"
Optical Connector
FC/APC
RF Connector
1.41"
Dimensions are in inches
Figure 3-2
Flange-mount package dimensions.
Ortel Corporation
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3.2.2
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Operating Manual
IF Fiberoptic Link
10K Plug-in Module
Plug-in style units may be used with an Ortel rack mount chassis (model 10990A), main power supply (model
10901A), and optional back-up power supply (model 10901B). Figure 3-3 shows an outline drawing of a plug-in
receiver module (the transmitter is nearly identical). The fiberoptic transmitter or receiver can be installed into any of
eight designated slots in the chassis. D-connectors on the rear panel of the plug-ins automatically engage blind-mate Dconnectors on the chassis back plane which are wired to the power supplies. The only remaining connections to be made
are to the RF and optical connectors. Transmitters and receivers may be inserted with the power supply turned on or off.
Refer to Table 3-4 for a listing of the input and output signals for this unit.
9 .1 2
1 .3 9
RF
10457A
F ib e r o p tic
R e c e iv e r
1 0 -2 0 0 M H z
O P T IC A L
Po w er
On
O p tic a l
Pow er
5 .0 6
FRONT PANEL
Figure 3-3
REAR PANEL
Plug-in package dimensions.
The status of the Tx and Rx plug-ins and power supplies can be monitored either from the front panel LEDs or
from back panel DC connectors. Both the Tx and Rx have a “Power On” LED, while the Rx also has an “Optical Power”
LED which is illuminated if the optical power into the receiver is greater than approximately 0.1mW. The 8
transmitter/receiver slots of the 10990A chassis each have a 5 pin connector (P11-P18, facing the rear) which provides
external access to the various status and alarm signals from the transmitters and receivers.
Table 3-4
Tx/Rx Dsub Pin #
1
2
3
4
5
6
BACK PANEL SIGNALS OF MODEL 10990A CHASSIS AND IF-BAND PLUG-INS
Back Panel P20
2
1
3
4
Back Panel
P11-P18
(+15VDC)
(+5V)
(–15V)
(GND)
7
8
9
nc = No Connection
1
2
Transmitter
Signal
Description
DC INPUT
+15VDC
nc
nc
nc
nc
GND
GND
nc
nc
nc
nc
nc
nc
nc
nc
3
4
5
Receiver
Signal
Description
DC INPUT
+15VDC
nc
nc
nc
nc
GND
GND
Photodiode
PDIM
current monitor.
1V/mA
Low optical
power alarm.
ALARM
0V/low Z if
Poptical>0.1mW.
+10V/high Z if
Poptical<0.1mW.
nc
nc
nc
nc
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Operating Manual
IF Fiberoptic Link
3.2.2.1. Model 10990A chassis & power supply monitoring and connections
The status of the Model 10901 power supply can be monitored from a pair of relays wired to a 9 pin in-line
connector (P19) on the 3U chassis. The pinouts are of the connector are described in Table 3-5. Another connector (P20)
connects directly to the power supply in the “main” slot in the chassis, which is the farthest left slot when viewed from
the back. This connector allows direct monitoring of the DC power voltages of the main power supply. This connector
can also be used for powering the chassis via an external source (i.e. without a chassis-mounted 10901A or B power
supply). The main power supply slot and P20 connect to the plug-ins through a set of diodes which allows for the power
supply redundancy, hence neither the back-up power supply voltages nor the actual voltage at the plug-in can be
monitored via P20 (voltage drops across the diodes must be accounted for).
Table 3-5
Pin
POWER SUPPLY STATUS MONITORING VIA THE 10990A CHASSIS CONNECTOR (P19)
Description
Main normal*
Main alarm*
Aux. normal*
Aux. alarm*
1
nc
--
--
--
--
2
nc
--
--
--
--
--
--
low Z to center tap
(relay closed)
high Z to center tap
(relay open)
--
--
center tap
center tap
--
--
high Z to center tap
(relay open)
low Z to center tap
(relay closed)
center tap
center tap
--
--
low Z to center tap
(relay closed)
high Z to center tap
(relay open)
--
--
high Z to center tap
(relay open)
low Z to center tap
(relay closed)
--
--
--
--
--
--
3
Aux. Status
(normally closed)
4
Aux. Status
(center tap)
5
Aux. Status
(normally open)
6
Main Status
(center tap)
7
Main Status
(normally closed)
8
Main Status
(normally open)
9
Ground
* Power supply status is determined by monitoring the power supply's +5V output only. The “Main” slot is the
farthest left slot when viewed from the back.
Table 3-6
Back Plane Connector
P11-P18
P19
P20
10990A CHASSIS MATING CONNECTORS AND PINS
Mating Connector
Crimp Pins
Molex P/N 22-01-2057
Molex P/N 08-50-0114
Molex P/N 22-01-2097
Molex P/N 08-50-0114
Molex P/N 09-50-3031
Molex P/N 08-50-0108
Ortel Corporation
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Model 4120A/10457A Receiver
10
Operating Manual
IF Fiberoptic Link
Chapter 4 Fiberoptic Components
4.1
Optical Specifications
The information included in Table 4-1 describes the optical parameters of the transmitter and receiver.
Table 4-1
OPTICAL SPECIFICATIONS (at +25C)
Transmitter
Wavelength
Power
Laser DC modulation gain
Receiver
Wavelength
Photodiode DC responsivity
Fiber
Connector
4.2
1310  30 nm
1.20  0.4mW
 0.02W/A
1280-1550nm
 0.85A/W @ 1310nm
Singlemode, 9/125
(Corning SMF-28 or equivalent)
FC/APC “tight fit”
(Type ‘R’ per IEC 1754-10-1)
 60dB optical return loss
Optical Fiber Basics
Light traveling in an optical fiber uses the principle of total internal reflection. Generally, when light is
incident on a boundary between two transparent media of different optical densities, there is a refracted and a
reflected ray. However, if the incident medium is more optically dense (higher index of refraction), there is an angle
of incidence below which there is no refracted ray; all the light is reflected. In optical fiber, the central core has a
slightly higher index of refraction than the cladding (see Figure 4-1). Also, the core is small enough in diameter that
all light that can be transmitted through the fiber will always be traveling in a path where all angles of incidence are
such that the light is totally reflected.
Figure 4-1
Light propagation in a step indexed fiber
Multimode fiber has a core large enough that there may be many spatial modes in the fiber. This is
analogous to sending an 18 GHz RF signal through waveguide designed for 200 MHz. There will be a lot of modal
dispersion that severely limits the bandwidth of modulated signals and makes the transmission sensitive to the
movement and bending of the fiber. Singlemode fiber has a core diameter small enough that only one mode is
passed. This minimizes dispersion and makes the fiber's transmission properties insensitive to movement. For this
reason, only singlemode fiber should be used with Ortel links.
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
4.3
11
Operating Manual
IF Fiberoptic Link
Optical Fiber
Ortel transmitters and receivers are designed for use with singlemode optical fiber (with the dispersion
minimum at 1310 nm). This fiber accounts for the majority of the fiber installed in the world today. While many
styles exist for the outer jackets and cables, the fundamental glass portion of the fiber is consistently 125 microns in
total diameter, with the inner 8-10 microns being the core which actually contains the light. With such a small core,
cleanliness and care of bare fiber is critical. This is why most singlemode fibers are covered with several layers of
protection, the first of which is a 250 micron coating. After that, indoor cables have a 900 micron plastic “tight
buffer”, while many outdoor cables use a “loose tube” instead in which the fiber floats in a petroleum-based jelly
inside a durable outer shell. Other cable designs include strength members, armor plating, and often multiple fibers.
As an example, 5/8 inch diameter cable assemblies are available containing as many as 96 fibers. The exact cable
style will depend on the application.
Regardless of the type of cable chosen, several considerations are universal, with perhaps the most critical
being bend radius. Like many types of RF cables, when an optical fiber is bent tighter than roughly a 1 inch (25 mm)
radius, the light will escape thus decreasing the RF gain of the link. Much tighter than 1 inch also may permanently
damage some fibers. Thus when storing or installing fiberoptic cable it should be wound and bent in loose coils or
turns. On the convenient side, optical fiber is immune to all electrical cross-talk, therefore optical cables can be
installed next to power and communication lines with no concern of signal degradation.
Finally, the fiber also must be singlemode, not multimode. Multimode fiber does not have sufficient
bandwidth nor gain stability for the applications serviced by Ortel links.
4.4
Optical Connectors
There are many optical connectors on the market. For high performance, high frequency RF applications,
the connector must be for singlemode fiber and be repeatable, low loss and, most importantly, have a low optical
return loss. Connectors with no return loss specification are for low speed digital and analog applications. Return
loss is important because optical reflections can degrade noise and linearity performance.
Connector styles. The Ortel connector of choice is the FC/APC, as indicated in Figure 4-2. In particular, the
connector used is the FC/APC “tight fit”, compatible with the Seikoh Giken connector. It has proved to be reliable
Figure 4-2
FC/APC style optical connector.
and repeatable, and most important, has very low backreflections of < -60dB. There are a number of manufacturers
who make connectors compatible with this connector; e.g., Seikoh Giken, Alcoa Fujikura and the Molex "Tight Fit".
Note that the Diamond FC/APC has a larger "key" and will not fit in the slot on the bulkhead optical connector. If in
doubt on the connector style, the width of the mating key can be measured. The tight fit style has a key width of 2.00
mm (+.02, -.03 mm) while the wider styles typically are 2.14 mm.
Ortel Corporation
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12
Operating Manual
IF Fiberoptic Link
Two other common styles of connectors include the ST, which is a bayonet style connector analogous to an
RF BNC connector, and the SC, which is a "snap together" connector. The FC style has a threaded sleeve for
making reliable mechanical connections. In all these cases the connectors themselves are sexless, with connections
being made using adapters that simply guide the tips of two common connectors together to make a continuous
optical path. While only FC/APC connectors can be mated directly with the Ortel transmitters and receivers, other
connector styles or optical splices may be used at patch panels provided the optical backreflections are kept low. The
best way to insure this is to use connectors with an 8 degree APC style polish or splices with optical reflections
comparable to that of APC connectors. Although no permanent damage to the transmitters or receivers occur, high
optical reflections can degrade the gain, noise, and linearity during operation.
Cleaning. Fiberoptic connectors on cable that come pre-terminated should be clean and capped, so one can
usually simply remove the cap and make the connection without cleaning the connector. But if there is any doubt, it
is good practice to clean the optical connectors before making the connection. Once the connection is made, there is
no need to periodically clean the connector as long as it remains connected. Additionally, the laser and photodiode
of the transmitter and receiver never require cleaning, although it is recommended to keep them covered when not in
use.
When handling or cleaning, remember that the light is emitted from an aperture only 9 m in diameter, so
even oils from your fingertips or a small scratch can easily cause interference. The concern is not just optical loss,
but also optical reflections, which can affect laser noise and distortion. To clean, moisten a cotton swab in alcohol
Figure 4-3
Cleaning optical connectors.
and gently wipe the tip of the connector ferrule several times. Allow to air dry. Refer to Figure 4-3.
Connecting. Once the connector is clean, bring it up to the bulkhead optical connector on the laser or
photodiode module. Note that the connector has a "key" on the side of its housing that must fit into the slot in the
bulkhead connector, as shown in Figure 4-4. Once these are aligned, carefully push the fiber connector into the
bulkhead connector so the key fits into the slot. (Not having the key properly aligned in the slot is a common
problem when using such optical connectors.) Next, push the threaded outer shell of the connector onto the bulkhead
so that the threads engage. The connector should be fastened finger tight only. Overtightening can damage the laser
or photodiode.
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
Figure 4-4
4.5
13
Operating Manual
IF Fiberoptic Link
Inserting FC-APC connectors.
Detecting Optical Power
The light from the transmitter is infrared and invisible to the human eye, hence some indirect method is
needed to detect it. The cheapest and easiest way to determine if the transmitter is emitting light is to direct the laser
or a fiber connector onto an infrared detection card (available, for example, from Fiber Instrument Sales, Inc., Part
#F1-4103 for approximately $10. Orsinsky, New York, USA, phone: 315-736-2206). Such cards glow a reddish
color with an intensity and shape corresponding to the infrared light. These cards are ideal for telling if a laser is on
or if a fiber has light in it.
DANGER
The light emitted from the fiberoptic connector or any fiber attached to the
connector is invisible and may be harmful to the human eye. Use either an
infrared viewer or fluorescent screen for optical output verification.
For a more quantitative measurement, an optical power meter with a calibrated detector can be used. (In
North America, Fiber Instrument Sales, EXFO [at 418-683-0211, or www.exfo.com], Newport Corporation [at 714253-1680, or www.newport.com] and many other companies make commercially available power meters.)
Additionally, the plug-in style receiver has a status monitor output, PDIM, which gives a voltage that is proportional
to the DC current on the photodiode (which is, in turn, proportional to the intensity of the received optical signal).
When the photodiode is illuminated with light, the DC current goes from near zero to a value which is proportional
to the intensity of the light.
The following equation describes the relationship between a link’s optical parameters and its corresponding
RF performance.
GRF, fiber = -20 log (PTx / PRx) = -20 log [(PTx  rRx) / IRx] = 2  Loptical
where,
GRF, fiber = RF gain of the optical medium
PTx = optical power from the transmitter
PRx = optical power at the receiver
= IRx/rRx
Eq. 4-1
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Operating Manual
IF Fiberoptic Link
IRx = DC current from the photodiode
rRx = DC responsivity of the receiver
Loptical = optical loss in dB between the transmitter and the receiver
It is evident that GRF is the effective RF gain (or loss, since GRF is normally 0) of the medium used to transport
the optical signal from the laser transmitter to the receiver. For example, if PTx = PRx (no optical loss), then GRF =
0dB.
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Operating Manual
IF Fiberoptic Link
Chapter 5 Installation
Setting up the fiberoptic link is fairly straightforward once the fiberoptic cable is in place with the proper
fiberoptic connectors. The cable must have FC/APC “tight fit” optical connectors compatible with the Seikoh
Giken connector. There are a number of manufacturers who make connectors compatible with this connector; e.g.,
Seikoh Giken, Alcoa Fujikura and the Molex "Tight Fit". However, the Rifocs Diamond FC/APC has a larger "key"
and will not fit in the slot on the bulkhead optical connector of your Ortel product. If in doubt on the connector style,
the width of the mating key can be measured. The tight fit style has a key width of 2.00 mm (+.02, -.03 mm) while
the wider styles typically are 2.14 mm. Additionally, for optimal noise and linearity performance, other connectors
and splices in the system should have low optical reflections, comparable to that of APC connectors.
This guide and checklist starts by listing the contents of the shipping cartons. It is followed by instructions
to install the flange mount modules in the outdoor enclosure and the 1U high rack mount chassis and the plug-in
units into the 3U high rack mount chassis.
5.1
Checklist for Unpacking Cartons
There are four different types of cartons used for packing the fiberoptic link: (A) a small cardboard box for
flange-mount modules, (B) a carton for the outdoor (NEMA) enclosure, (C) a carton for the 1U high rack mount
chassis, and (D) a carton for the 3U high rack mount chassis (for plug-in modules). The fiberoptic transmitter and
receiver modules must be installed in the outdoor enclosure or rack mount chassis by the user (see next section).
A)
Module Carton - for flange-mount modules
 This carton(s) contains the flange-mount modules which are packed separately from any of
the available mounting chassis.
B)
Outdoor Enclosure Carton (NEMA) - for flange-mount modules
 One (1) Type 3R NEMA Enclosure, Ortel P/N 1260-001-001.

C)
1
One (1) Mounting Kit. This hardware is for mounting up to two flange-mount modules inside
the NEMA box, not for mounting the NEMA box itself. It includes:

Eight (8) #6 x 3/16 inch long Phillips style pan head screws. The back panel of the
NEMA is pre-drilled and tapped for this hardware.

Eight (8) #6 split lock washers.

Two (2) wire saddles with adhesive base to be mounted inside the NEMA box on the
back panel. Used for strain relief for RF and optical cables.
Indoor Rack Mount Chassis Carton - for flange-mount modules
 One (1) 1U high, 19 inch rack mount chassis with or without optional internal universal
power supply.

One (1) AC power cord (North America version).

One (1) Mounting Kit. This hardware is for mounting up to four flange-mount modules inside
the chassis, not for mounting the chassis itself. It includes:

16 #6 flat head screws1

8 #6 split lock washers2
Applies to early versions of the 1U high chassis. Later versions come with pre-installed threaded studs, eliminating
the need for the user installed mounting screws.
2
Early versions of the 1U chassis utilized quantity 16 for each of the washer types and nuts.
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver

D)

8 #6 flat washers2

8 #6 hex nuts2

2 wire saddles with adhesive base to be mounted inside the chassis. Used for strain relief for
RF and optical cables.

4 resistors, 2.2k (for use with older transmitter and receiver modules)
Two (2) Chassis Mounting Brackets. Front panel rack mounting flanges.
Indoor Rack Mount Chassis Carton - for plug-in modules
 One (1) 3U high, 19 inch rack mount chassis, with or without internal power supplies.

5.2
16
Operating Manual
IF Fiberoptic Link
Up to two (2) AC line cords (North America version), depending on power supply
configuration.
Installing Flange-mount Modules in the Outdoor NEMA Enclosure
The outdoor enclosure available from Ortel is pre-drilled to mount one or two modules. You will need a #2
Phillips screwdriver and a medium sized flat tip screwdriver.
1.
For a watertight seal, pot the optical connectors with RTV. This will be easier to do before the module is
secured to the back panel of the outdoor enclosure. Do not use silicone. Silicone outgases and, over time,
will darken the fiber. If the NEMA box alone provides enough environmental protection for the modules,
skip this step.
2.
Fasten the module to the back panel of the NEMA box using the #6 screws and split lock washers. The
holes in the back panel are tapped. Make sure that the RF and optical connectors are pointed down.
3.
The electrical connections are shown in Figure 5-1. Connect the red and black wire leads from the module
to the terminal block. Make sure the red lead goes to the terminal where the +VDC wire from the remote
power supply is connected. The other lead is Ground. The remaining three leads from each module may be
secured to the terminal strip.
Any unused wire lead should be shielded or otherwise protected to safeguard
against potentially damaging short circuits.
4.
An attenuator at the RF input to the transmitter may or may not be necessary to optimize the RF
performance (see Chapters 2 ).
5.
Use the adhesive-backed wire saddles and tie wraps supplied to secure the RF and optical cables to the
back panel. This provides strain relief for the RF and optical connectors.
6.
Replace the NEMA box front panel and secure it with the proper fasteners.
2
Early versions of the 1U chassis utilized quantity 16 for each of the washer types and nuts.
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
3120A
Figure 5-1
5.3
17
Operating Manual
IF Fiberoptic Link
4120A
Installing flange-mount units in the outdoor NEMA enclosure.
Installing Flange-mount Modules in the 1U Rack Mount Chassis
The 1U rack mount chassis available from Ortel is designed to mount up to four flange-mount modules.
There are two versions: one includes a +15VDC power supply with a universal AC input and a power cord (North
America version). The other does not include an internal power supply. You will need a screwdriver and a nut driver
or socket wrench for the terminal screws and mounting nuts. If the chassis is to be mounted in a rack, make sure to
install the front panel rack mount flanges (supplied).
1.
Fasten the modules to the bottom panel using the screws3, flat washers, lock washers and nuts.
2.
The DC connections are made to the terminal blocks as shown in Figure 5-2. Refer to Table 5-1 for a list of
all the connections to be made.
Any unused wire lead should be shielded or otherwise protected to safeguard
against potentially damaging short circuits.
3
Applies to early versions of the 1U high chassis. Later versions come with pre-installed threaded studs, eliminating
the need for the user installed mounting screws.
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Operating Manual
IF Fiberoptic Link
Rack
mounting
bracket
GND (Black)
PDIM (Yellow: rcvr only)
+VDC (Red)
Power supply
ALARM
(Brown:
rcvr only)
(only with chassis
P/N 1261-002-001)
(Black)
POWER LED
(Orange)
Power supply +VDC
(P/N 1261-002-001 only)
Brown: ALARM
(rcvr only)
Yellow: PDIM
(rcvr only)
Figure 5-2
Power
supply
Power supply ground
(P/N 1261-002-001
only)
Orange:
POWER
LED
Installing flange-mount units in the 1U chassis.
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Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
3.
19
Operating Manual
IF Fiberoptic Link
Position the chassis in front of the rack space where it is to be mounted. Pull the fiberoptic and RF cables
through from behind the rack. Route them through the opening in the chassis rear panel. Connect each input
and output to the appropriate module.
Make sure the optical connectors are finger tight only - do not over tighten
or the connector may be damaged.
4.
Use the adhesive-backed wire saddles and tie wraps supplied to secure the RF and optical cables to the
bottom panel providing service loops where possible. This provides strain relief for the RF and optical
connectors on the modules.
5.
Replace the top panel and attach it with the provided hardware.
Table 5-1
Block A
Terminal Block Connections
Module # / wire color
Block B
Module # / wire color
1
1
1 / Black & 2 / Black
2
2
3 / Black & 4 / Black
3
3
1 / Yellow
4
4
2 / Yellow
5
5
3 / Yellow
6
6
4 / Yellow
7
7
1 / Red & 2 / Red
8
8
3 / Red & 4 / Red
9
1 / Brown
9
G2
10
2 / Brown
10
G2
11
3 / Brown
11
12
4 / Brown
12
13
1 / Orange
13
14
2 / Orange
14
15
3 / Orange
15
+15VDC*
16
4 / Orange
16
PS / +15VDC*
G1
G1
G2
G2
G3
G3
G4
PS / Ground*
* PS = Power Supply.
G4
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5.4
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IF Fiberoptic Link
Installing 10k Plug-in Style Modules in the 3U Rack Mount Chassis
The 3U chassis supplied by Ortel can hold up to eight plug-in modules. Install the model 10357 transmitter
and 10457 receiver plug-ins into the 10990A chassis starting with the left-most slot.
1.
Carefully align the plug-in unit with the track in the desired slot of the chassis.
2.
Gently slide the plug-in unit into the chassis until the rear panel sets against the backplane. The 9-pin
D-connector will self align with the mating backplane connector. Do not force the unit against the
backplane. If excessive resistance is felt, remove the unit and re-align it in the chassis.
3.
Secure the plug-in by tightening the four corner screws on each module's front panel.
Refer to Tables 3-5 and 3-6 for connection information for the power supply status and monitoring signals available on
the model 10990A 3U rack mount chassis. Table 3-4 details the back panel connections for the status monitoring
features for the fiberoptic plug-in modules.
Ortel Corporation
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21
Operating Manual
IF Fiberoptic Link
Chapter 6 Optimizing RF Performance
This fiberoptic link has been designed to provide a transparent interfacility link for a wide range of small
satellite earth terminals. The link itself has fixed gain, noise figure and linearity characteristics so its effect on earth
station performance can be analyzed like any other active element in the signal path. The following sections give
some guidance to optimizing the RF performance for a number of different applications. Optimizing the RF
performance means setting the input RF drive level to the optimum value. If the available RF signal level is too
high, an RF attenuator should be used. If the available RF level is too low for good noise performance then
additional amplifiers or a higher gain fiberoptic transmitter should be used. (Some IF equipment combines both a
high level 10MHz reference tone with the 70 or 140MHz carrier signal on the same cable. The 3120A/4120A and
10357A/10457A products are not optimized for such simultaneous signals, therefore usually it is necessary to split
the 10 MHz onto a separate cable.)
6.1
Link Gain
The RF gain (G) for a complete linear fiberoptic link can be calculated as follows:
G = TG + RG – 2Loptical +10log(Rout/Rin)
where,
Eq. 6-1
TG is the transmitter gain in dB·W/A
RG is the receiver gain in dB·A/W
Loptical is the optical loss between the transmitter and receiver in dB.
Rin & Rout are the transmitter input and receiver output impedances,
respectively (either 50 or 75).
TG and RG are related to the unit’s total RF efficiency expressed in W/A or A/W (Tx, RF & Rx, RF, respectively).
The RF efficiencies include the laser or photodiode efficiency (slope efficiency or modulation gain for the laser,
responsivity for the photodiode) plus the gain contribution from matching networks and RF amplifiers. The terms
TG and RG are simply the RF efficiencies expressed in units of dB as follows:
TG = 20log (Tx, RF);
RG = 20log (Rx, RF)
For example, a typical link may consist of a 75 transmitter with a TG of -9dB·W/A, a 75 receiver with RG of
+13dB·A/W, and a 1dB optical loss. The total link gain would then be:
G = -9dB·W/A + 13dB·A/W - (2  1dB) +10log(75/75) = +2dB.
6.2
Common Link Performance Parameters
The link parameters in Table 6-1 are calculated based on the minimum specifications of separate
transmitters and receivers with a 1dB optical loss. The table shows data for the case where flange-mount units are
used, but the same results will apply to the plug-in style modules as well. Actual performance for an installed system
will vary primarily due to differences in the optical loss for the connector, splices and fiber used. This can be
calculated for the specific system with the equations below. Noise and linearity also are affected by optical loss and
optical reflections from components. However, provided that the link loss is only a few dB and that the optical
reflections are kept to a minimum by using APC connectors, the noise and linearity numbers in Table 1 may be used
for a reasonable first order approximation.
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
Table 6-1
Tx Specs
Gain version
Tx Gain (TG)
NF
Input TOI, 2-tone
Input 1 dB Comp.
Power, max.
Impedance
22
Operating Manual
IF Fiberoptic Link
EXAMPLE LINK PARAMETERS
3120A
Std
-10
26
0
-10
1.6
75
Rx Specs
4120A-102
Gain version
High
Rx Gain (RG)
27
PD Responsivity
0.85
Equiv. Noise Current
10
Output TOI, 2-tone
10
Output 1dB Comp.
0
Impedance
75
Calculated Link Performance
Tx gain version
Std
Rx gain version
High
Optical loss
1
RF Gain
15.0
Output 1dB
0.0
comp.
NF
27.3
C/N, 36 MHz BW
Input C = 0
*
(in dBm) -10
*
-20
50.9
-30
40.9
-40
30.9
-50
20.9
Input TOI
-5.6
Output TOI
9.4
C/I, 2-tone input
Input C = 0
*
(in dBm) -10
*
-20
28.7
-30
48.7
-40
68.7
-50
88.7
Amplitude Flatness
10 - 200 MHz
+ 0.5
over any 40 MHz
+ 0.25
* Indicates input is above the 1 dB compression point
Usually Preferred
3120A 3120A-102 3120A-102
Std
Low
Low
-10
-25
-25 dBW/A
26
41
41 dB
0
15
15 dBm
-10
5
5 dBm
1.6
1.6
1.6 mW
75
75
75 
4120A 4120A-102
Std
High
12
27
0.85
0.85
10
10
14
10
0
0
75
75
4120A
Std
12
0.85
10
14
0
75
dBA/W
A/W
pA/Hz½
dBm
dBm

Std
Std
1
0.0
-10.0
Low
High
1
0.0
0.0
Low
Std
1 dB
-15.0 dB
-10.0 dBm
27.3
42.7
42.7 dB
*
*
50.9
40.9
30.9
20.9
0.0
0.0
*
45.9
35.9
25.9
15.9
5.9
9.4
9.4
55.9
45.9
35.9
25.9
15.9
5.9
15.0
0.0
*
*
40.0
60.0
80.0
100.0
*
38.7
58.7
78.7
98.7
118.7
30.0
50.0
70.0
90.0
110.0
130.0
+ 0.5
+ 0.25
+ 0.5
+ 0.25
dB
dB
dB
dB
dB
dB
dBm
dBm
dB
dB
dB
dB
dB
dB
+ 0.5 dB
+ 0.25 dB
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
23
Operating Manual
IF Fiberoptic Link
Chapter 7 Troubleshooting and Maintenance
Once the fiberoptic link has been installed, there is no need for any regular maintenance. However, if
problems do arise the most common causes and cures are listed here.
7.1
Low or Nonexistent RF Gain
For low RF gain, first check the option numbers and optical loss and then verify from Table 2-1 and
Equation 6-1 that the correct link gain is being measured. If the gain is lower than it should be, first verify that the
DC power to the optical transmitters and receivers has the correct voltage and current (Chapter 3). Next, check the
optical elements as highlighted in section 7.3 below. Another possibility is that the receiver is being saturated by a
transmitter which has too much optical power (approximately 2mW or greater) or the link has an excessive RF input
level. Model 3120A/10357A transmitters emit <2mW of optical power - low enough to never saturate a
4120A/10457A receiver - so this is only a concern if another transmitter is used. Lastly, the DC circuitry of the unit
itself may be verified as described in 7.4.
7.2
High Noise or Intermodulation Distortion
For a system with good gain but poor noise or intermods, the most likely cause is RF signal levels that are
either too high or too low. Review Chapter 2 and Chapter 6 to determine the optimal RF power and adjust as
necessary. High optical back reflections into the laser also can degrade noise and linearity, so verify that the FCAPC style connector is used to connect to the transmitters and receivers. Also check that all other connectors and
splices between the transmitter and receiver also have good optical return loss. Refer to Chapter 4 for tips on the
proper care of fiberoptic components.
7.3
Low Optical Power at the Receiver
If it appears that low gain or poor noise is due to low received optical power, review Chapter 4 to be sure
that the optical connectors and fibers are being used properly. The most common problem, and easiest to fix, is that
the connector key in not aligned with the mating slot. Other common problems include dirty connectors, bent fibers,
broken fibers, disconnected connectors and overly tightened optical connectors. To determine exactly where light is
being lost, start at the transmitter and work forward to the receiver, measuring or detecting power along the way. (As
noted in section 4.3., an IR detection card at less than $10 is an indispensable piece of test equipment.)
DANGER
The light emitted from the fiberoptic connector or any fiber attached to the
connector is invisible and may be harmful to the human eye. Use either an
infrared viewer or fluorescent screen for optical output verification.
Another good clue is the status of the optical power alarm and/or photodiode current monitor outputs from
the receiver. Bear in mind though that the optical power alarm triggers at approximately 0.1mW, therefore this only
gives an indication of extreme cases. Also, some applications expect and can tolerate high optical losses, so in such
cases if the RF performance is OK, the optical alarm may be ignored.
Ortel Corporation
Model 3120A/10357A Transmitter
Model 4120A/10457A Receiver
7.4
24
Operating Manual
IF Fiberoptic Link
DC Circuit Verification
Chapter 3 details the DC monitoring and powering functions available with the IF-band IFL. Beyond the
more obvious external problems such as no electrical power or disconnected cables, the internal DC circuits also can
be quickly verified. The POWER LED indicator is provided on the flange-mount transmitter and receiver. A logic
"high" on this output (+6.5VDC for the transmitter; +10VDC for the receiver) when DC power is applied to the
unit indicates that regulated DC voltage is present inside the module. For plug-in units, the POWER ON indicator
LED is provided on the front panel and will be illuminated when DC power is applied to the unit. If the POWER
LED signal is not "active" (flange-mount) or the front panel LED is not illuminated (plug-in) when DC power is
applied to the unit, then it may have suffered a DC failure or burned fuse. An alternative method for checking the
health of a transmitter is as follows: when DC power is applied, infrared light should be emitted from the laser
connector. It can be observed with an IR detection card. For the receiver, when DC power is applied and the optical
connector is disconnected, the ALARM pin should be active (+10VDC). If these tests fail, then the unit may have
suffered a DC failure or burned fuse.
7.5
Fuse Replacement
An internal fuse in the plug-in versions of the IF-band transmitters can be replaced by pulling the unit from
the chassis, removing the four small screws holding the U-shaped side panel, and removing this panel. (Removing
the cautionary stickers to replace the fuse does not void the warranty.) The fuse should be replaced with a quickblow style with a rating of 0.8A.
Newer versions of the flange mount transmitter and receiver have a field replaceable fuse which is
accessible on the rear of the unit's housing. The fuse should be replaced with a quick-blow style with a rating of
0.8A.
Neither the plug-in receiver nor older versions of the flange-mount products have a user replaceable fuse.
These units must be returned to the factory for fuse replacement.
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