Diamond TX Series User manual

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Transmitter
TX and QTX SERIES
TRANSMITTERS
Contents
Equipment Description ................................................................................................................................................79
Models ..........................................................................................................................................................................82
Controls, Indicators, and Connectors .................................................................................................................84
DT-TX Series Transmitters ..............................................................................................................................84
DT-QTX Controls and Connectors ...........................................................................................................89
Functional Description .................................................................................................................................................91
RF Signals .....................................................................................................................................................................93
Optical Signals ...........................................................................................................................................................94
Control Signals .........................................................................................................................................................94
DC Power ..................................................................................................................................................................95
Automatic Shutdown ....................................................................................................................................................96
Break in the Forward Link .................................................................................................................................97
Break in the Return Link .....................................................................................................................................97
Setting Up Automatic Shutdown ..................................................................................................................98
Installation .........................................................................................................................................................................100
Before You Start ..................................................................................................................................................100
Tools and Equipment ........................................................................................................................................101
Installing a Transmitter in the DT Shelf ...................................................................................................102
Checking Optical Output ................................................................................................................................105
Checking Laser Bias Current .........................................................................................................................108
Connecting the Optical Fiber .......................................................................................................................109
Connecting the RF Signal ................................................................................................................................113
Setting Up the Transmitter .....................................................................................................................................114
Tools and Equipment ........................................................................................................................................114
Activating the Transmitter ..............................................................................................................................115
Setting the Transmitter for Manual Mode (DT-TX Series) ........................................................118
Setting Up AGC ...................................................................................................................................................120
Specifications ...................................................................................................................................................................125
AM Optical Link Performance ..............................................................................................................................127

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Transmitter
Equipment Description
DT-TX series plug-in transmitters convert radio frequency
(RF) input into an optical signal and send it, through single
mode fiber optic cable, to optical receivers (nodes) in a
hybrid fiber-coaxial network. The 200-TX modules are return
transmitters; the 700-TX and 800-TX modules are forward
transmitters.
The DT-QTX facilitates the
use of dense wave division
multiplexing (DWDM) for
services such as high-speed
internet access, telephony,
and video-on-demand.
DT-QTX quadrature amplitude modulated (QAM)
transmitters are part of the SpectraHubä1550 nm Analog/
Digital Overlay Transport System designed for use in the
Diamond Transport Shelf. The 810-QTX offers a 400 MHz
to 870 MHz frequency response and is designed for forward
narrowcast applications. The 210-QTX offers a 5 MHz to
200 MHz frequency response for return path applications.
Figure 35. Diamond™Transport Transmitter Module
All DT-TX and DT-QTX series transmitters fit into the DT-Shelf’s
universal slots. TX series transmitters transmit analog broadband
signals over optical fiber. QTX series transmitters are part of
Philips’ 1550 nm Analog/Digital Overlay Transport System.

80 9 November 2001 Transmitters
Transmitter Frequency Response
Each Diamond Transport transmitter amplifies RF signal and
directly modulates a DFB laser diode to produce optical
output. Transmitter modules occupy one universal module
slot in the 3U-high Diamond Transport Shelf.
Housing The die-cast aluminum housing protects sensitive internal
circuits. The housing’s patented thermal design improves the
heat dissipation, extending product life and enhancing
reliability. An additional heat sink for the laser helps protect it
in high-temperature environments.
Internal Circuits Each transmitter module contains a variable attenuator,
adjusted automatically or manually, which lets you adjust the
RF drive level to the laser. RF signals are amplified and
pre-distorted before they reach the laser. Pre-distortion acts
to linearize laser performance by improving second order
distortions of the analog channels through distortion
cancellation.
Electronic control circuits inside the module maintain
constant optical output power and laser temperature, while
communicating the transmitter’s status to the optional
network interface card (NIC) on the Diamond Transport
shelf; the NIC serves as the interface with local or remote
monitoring systems.
The 800E-TX and 800G-TX series transmitters offer high
isolation on the auxiliary RF input to facilitate insertion of
local targeted video channels.
Transmitter Series Total Bandwidth Analog Bandwidth
200-TX 5-200 MHz 5-200 MHz
700-TX 45-750 MHz 45-550 MHz
800C-TX 45-862 MHz 45-862 MHz
800E-TX 45-862 MHz 45-650 MHz
800G-TX 45-862 MHz 45-862 MHz
210-QTX 5-200 MHz —
810-QTX 400-870 MHz —

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Transmitter
Each 210-QTX and 810-QTX is tuned to a specific
International Telecommunication Union (ITU) channel
wavelength at 256 QAM. The 810-QTX permits adjustment
of fiber-length setting to meet the requirements of a
particular link.
Front Panel LEDs and test points on the front panel let you monitor a
transmitter’s performance. All Diamond Transport
transmitters come with an optical connector on the front
panel, providing access to both sides of the optical bulkhead.
The 200-TX, 700-TX, and 800C-TX series transmitters use
the AGC/MAN switch to select automatic or manual gain
control mode. The 800E-TX and 800G-TX transmitters offer
an additional setting for customer-set AGC (AGC active with
customer-optimized OMI). In the automatic mode, the
transmitter compensates for minor fluctuations in the RF
signal and maintains a constant RF drive level to the laser. In
the manual mode, you’ll adjust this level with the manual gain
control, also accessible through the front panel; RF drive level
varies with fluctuations in the signal source. The 210-QTX
and 810-QTX series transmitters do not have AGC.
Rear Panel RF, control, and DC signals enter the transmitter through
connectors on the housing’s back panel. TX Series
transmitters offer a second RF input for locally injected RF
signals.

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Models
Refer to “AM Optical Link
Performance”for details on
optical link budgets.
Diamond Transport transmitters are available in several
models. Use the following key to interpret model names.
To support local video injection, the 800E-TX and 800G-TX
transmitter series offer higher isolation between the auxiliary
and main inputs than the 800C-TX series offers. When
combined with the DT-SRS sub-rack splitter, the combined
isolation (between transmitters) of the locally injected
channels is ≥60 dB. In addition, the 800E-TX and 800G-TX
transmitter series provides three AGC options (Customer-set
level, Factory-set level, and Manual [i.e., AGC off]) while the
800C-TX offers only Factory-set and Manual settings.
DT- _ _ _ _-TX- _____
Diamond Transport System
Highest Forward Frequency
2 = 200 MHz (return)
7 = 750 MHz (forward)
8 = 862 MHz (forward)
Optical Connector Options
FC/APC = FC/APC
SC/APC = SC/APC
E2000D = E2000
Optical Link Budget (dB)*
10, 12, or 14 dB (200-TX models)
05 to 15 dB (700-TX & 800-TX models)
Isolation and/or Optimization Options
Blank = Optimized for 550 MHz Analog (700-TX only)
Blank = Standard isolation (200-TX only)
C = Optimized for 862 MHz Analog (800C-TX only)
E = Optimized for 650 MHz Analog, High Isolation
Auxiliary RF Input (800E-TX only)
G = Optimized for 862 MHz Analog, High Isolation
Auxiliary RF Input (800G-TX only)

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Transmitter
210-QTX and 810-QTX QAM Transmitters
The 810 series offers a 400 MHz to 870 MHz frequency
response and is designed for both forward narrowcast and
return path applications. The 210 series offers a 5 MHz to
200 MHz frequency response and is designed for return path
applications.
Each transmitter’s laser is tuned to a specific International
Telecommunication Union (ITU) channel wavelength:
•810-QTX modules are available for ITU 21-59 (odd)
•210-QTX modules are available for ITU 21-37 (odd)
DT- _ _ _-QTX _ _ - _____
Diamond Transport System
Bandwidth, Output Power
210 = 200 MHz, 10 dBm
810 = 870 MHz, 10 dBm
Optical Connector Options
FC/APC
SC/APC
E2000
QAM Transmitter
International Telecommunications Union (ITU) Channel

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Controls, Indicators, and Connectors
DT-TX Series
Transmitters Standardized controls, indicators, and connectors simplify installation and use of TX series transmitters.
Connectors on the rear of the transmitter modules plug into
the Diamond Transport shelf. Cabling is connected to the
shelf backplane, not directly to the module.
CAUTION
The bulkhead and optical connector on a Diamond
Transport transmitters is covered by a protective shield. To
make connections or to clean connectors, you must remove
the two screws holding the shield in place and then remove
the shield. DO NOT put the screws back into the
transmitters without the shield; doing so damages the Laser
Safety Interlock switch.
Figure 36. Standardized Controls, Indicators, and
Connectors
To simplify installation and use, DT-TX transmitters use a
common set of controls, status indicators, and points of
connection.

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Transmitter
DT-TX Series Controls, Indicators, and Connectors
Key Switch Safety key switch. Turn key to activate laser. See “Test Points and Controls.”
Optical Connector Ferrule or snap connector (under shield). Carries forward optical signal out
of the transmitter module.
Front Panel
AGC/MAN Switch Toggle switch. With 200, 700, and 800 series, turns automatic gain control
on or off. A customer-set option is available on the 800E and 800G. See
“Test Points and Controls.”
AGC LED Two-color (green/red) LED. See “LED Status Indicators.”
PWR LED Green LED. See “LED Status Indicators.”
LASER LED Amber LED. See “LED Status Indicators.”
MAN ADJ/Manual Gain
Control Adjusts the RF drive level to the laser by ± 3 dB. (See “Test Points and Controls.”) Used—on 800E-TX and 800G-TX—to adjust AGC level.
BIAS/Laser Bias Test
Point DC test point (10 mV/mA). Measures laser bias current.
RF Test Point RF drive level monitor. Used to adjust the RF drive. See “Test Points and
Controls.”and specifications.)
DC Power Input 10-pin plug. Carries DC power into the transmitter.
Rear Panel
•Pins 1 and 2 –5 VDC
•Pin 3 Ground
•Pins 4 and 5 +5 VDC
•Pin 6 Ground
•Pins 7 and 8 Ground
•Pins 9 and 10 +24 VDC
Communications Edge connector. Connects to Diamond Transport shelf backplane. Carries
control information into and out of the transmitter module.
Main RF Input Connects to Diamond Transport shelf backplane. Allows primary RF signal
to enter the transmitter.
Auxiliary RF Input Connects to Diamond Transport shelf backplane. Allows auxiliary RF signal
to enter the transmitter.
RF Bandwidths:
•5–200 MHz for 200-TX
•550–750 MHz for 700-TX
•550–862 MHz for 800C-TX
•45–862 MHz for 800E-TX and 800G-TX.
Side Panel
SW3 & SW2 10-position switches used to configure the transmitter for Automatic
Shutdown. Set to accept logic signal from a specific 2RRX return receiver or
FRX forward receiver.

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LED Status Indicators Use the indicators, controls, and test points on the front
panel of the module to monitor transmitter performance.
Label LED
State Indicates
AGC
Green
Red
Off
Transmitter is in AGC mode, and its RF drive
level has been automatically adjusted to
match the factory-set AGC reference.
Transmitter is in AGC mode, but RF input to
TX is outside of AGC operating window.
The transmitter’s RF drive level cannot be
automatically adjusted to match the
factory-set RF level.
The transmitter is in manual mode. Use
manual gain control to adjust the RF drive
level by ± 3 dB from input level.
PWR
Green
Blinking
Green
Off
Transmitter module is powered.
Transmitter is stabilizing during initialization
or is disabled by Automatic Shutdown.
No power to transmitter.
LASER
(See also
p116.)
Yellow
Blinking
Yellow
Flashing
Yellow
Off
Laser is on.
Continuous blinking indicates laser
temperature is above 65°C.
Single, periodic flashes indicate that laser has
been disabled by Automatic Shutdown. The
associated receiver periodically initiates the
restart sequence.
If this occurs at start-up, the shield may be
out of place or the bottom screw securing
the shield is not tight.
If the unit has been running, laser
temperature may be greater than 75°C.

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Transmitter
Test Points and Controls Test points and controls are mounted on the front panel for
easy access.
CUST
FACT
MAN
Label indicates AGC options
and toggle positions.
Label Description
Key Switch Activates / deactivates laser. Allows the operator to “lock out”(by
removing the key) the transmitter for maintenance. (Note: Laser
operates only when the shield that covers the optical connection is
installed).
AGC/MAN
For more information, see
“AGC Labeling and Toggle
Positions”on page 88.
The 200-TX, 700-TX, and 800C-TX transmitters offer two AGC
settings: Factory-set AGC Active and Manual Mode (no AGC).
The 800E-TX and 800G-TX transmitters offer three AGC settings:
Customer-set AGC (optimized OMI) Active, Factory-set AGC Active,
and Manual Mode (No AGC).
MAN ADJ Manual gain control. When the AGC switch is in manual, an operator
may adjust the RF drive level to the laser.
When using customer-set AGC function (CUST setting) with 800E-TX
and 800G-TX transmitters, use the manual gain control to set the AGC
level.
BIAS DC test point. Use digital voltmeter to measure laser bias. (10 mV/mA).
RF Test Point RF drive level monitor test point (–20 dB relative to the transmitter’s
RF input level). Used to adjust the RF drive to the optimum level. (See
specifications.) For example, a transmitter with a rated input of
+15 dBmV, should be adjusted to a level of –5 dBmV at the test point.

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AGC Labeling and Toggle
Positions 200-TX, 700-TX, and 800C-TX
The 200-TX, 700-TX, and 800C-TX series transmitters offer
two settings, with toggle positions indicated by the label
above the toggle switch:
800E-TX and 800G-TX
The 800E-TX and 800G-TX series transmitters offer three
settings, with toggle positions indicated bythe label above the
toggle switch:
NOTE
DT-QTX transmitters do not offer AGC.
AGC
MAN
Toggle UP to activate AGC at factory-set
level.
Toggle DOWN for manual mode.
Label not to scale.
Toggle UP to activate AGC at customer-set level.
Toggle CENTER to activate AGC at factory-set
level.
CUST
FACT
MAN Toggle DOWN for manual mode.
Label not to scale.

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Transmitter
DT-QTX Controls and
Connectors Standardized controls, indicators, and connectors simplify installation and use of QTX series transmitters.
Connectors on the rear of the transmitter modules plug into
the Diamond Transport shelf. Cabling is connected to the
shelf backplane, not directly to the module
CAUTION
The bulkhead and optical connector on a Diamond
Transport transmitter are covered by a protective shield. To
make connections or to clean connectors, you must remove
the two screws holding the shield in place and then remove
the shield. DO NOT put the screws back into the
transmitters without the shield; doing so damages the Laser
Safety Interlock switch.
Figure 37. DT-QTX Controls and Connectors
DT-810-QTX fiber-length setting may be optimized through the
front panel.

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Label Description
Key Switch Safety key switch. Turn key to activate laser.
Optical Connector Snap connector (under shield).
Front Panel
Fiber Length Adjustment Available on 810-QTX series only
Fiber Test Point 1 volt / 10 km of fiber (800 series only)
PWR LED Green LED.
LASER LED Amber LED.
RF Gain Control Adjusts the RF drive level to the laser by ± 3 dB.
Laser Bias Test Point DC test point (10 mV/mA). Measures laser bias current.
RF Test Point RF drive level monitor. (Note that readings are 20 dB down.)
Side and Rear Panels
DC Power Input 10-pin plug. Carries DC power into the transmitter.
Communications Edge connector. Connects to Diamond Transport shelf backplane.
Carries control information into and out of the transmitter module.
Main RF Input Connects to Diamond Transport shelf backplane. Allows RF signal to
enter the transmitter.
SW3 & SW2 10-position switches used to configure the transmitter for Automatic
Shutdown.

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Transmitter
Functional Description
All TX series plug-in transmitters convert radio frequency
(RF) input into an optical signal and process RF, optical,
control, and DC power signals.
Diamond Transport 800E-TX and 800G-TX transmitters
offer customer-adjustable AGC and a high-isolation auxiliary
RF input for insertion of targeted video programs.
Figure 38. DT 200-TX, 700-TX, and 800C-TX Functions
All Diamond Transport transmitters process RF, optical, control,
and DC power signals.
Figure 39. DT 800E-TX and 800G-TX Functions
DT 800E-TX and 800G-TX transmitters offer
customer-adjustable AGC and a high-isolation auxiliary RF input.

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The DT-QTX facilitates the use of dense wave division
multiplexing (DWDM) for digital services such as high-speed
internet access, telephony, and video-on-demand.
Each transmitter’s laser is tuned to a specific International
Telecommunication Union (ITU) channel wavelength.
Figure 40. DT-QTX Functions
Each transmitter’s laser is tuned to a specific ITU channel and is
factory-configured for fiber length at 256 QAM.

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Transmitter
RF Signals Input Ports: RF signals from the shelf backplane enter the
transmitter through RF connectors on the rear of the
transmitter module. The recommended RF input level
depends on the channel loading used.
In the 800E-TX and
800G-TX transmitters,
auxiliary RF signals are
injected after the
pre-amplifier hybrid. This
helps to provide higher
isolation between the
auxiliary and main RF input
ports.
•Main RF input allows primary RF signals to enter the
module.
•Auxiliary RF input (not available on the DT-QTX) allows
injection of auxiliary RF signals for applications such as
targeted services (local programming).
Combiner: Auxiliary signals are attenuated by an internal
directional coupler, yielding lower levels than those of the
main RF input. See specifications for details.
Variable PIN Attenuator: After passing through the
combiner, RF signals then pass through a variable PIN
attenuator, adjusted by AGC or manual gain control. The PIN
attenuator allows you to adjust, either manually or
automatically, the RF drive level by ±3 dB.
Pre-amplifier Hybrid: Next, a hybrid amplifies the signal.
RF Test Point (Drive Level Monitor): A directional coupler
directs a portion of the amplified signals to the RF drive level
monitor test point, which is used to adjust the RF drive to the
optimum level. Using this test point, you can adjust the
transmitter’s gain for –20 dB relative to the laser’s RF drive
level. (See specifications.) This test point is accessible through
the transmitter’s front panel.
Post-amplifier Hybrid: A post-amplifier hybrid amplifies the
RF signals.
Gain Control Circuitry: The 800E-TX and 800G-TX series
transmitters offer three AGC modes: Customer AGC (AGC
On with customer-optimized OMI), Factory AGC (ACG On
with factory-set OMI), and Manual (AGC Off). Other DT-TX
series transmitters offer Manual and Factory AGC modes
only. The DT-QTX series does not offer AGC.
If the transmitter is set to manual gain control mode, use the
manual gain control, a potentiometer accessible through the
front cover of the transmitters, to adjust the variable PIN
attenuator.

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AGC AND PROOFING WITH CW CARRIERS
Do not use AGC when proofing transmitters that operate
with CW carriers. When CW carriers are used, the AGC
circuit reduces gain by about 2.0 dB, which reduces a link’s
C/N by 2.0 dB from what wouldbe achieved with modulated
carriers.
A coupler directs a portion of the amplified signals to an
automatic gain control (AGC) broadband detector. The DC
output of the AGC detector is routed to a comparator,
which checks the voltage against a factory-set reference. This
reference is set for modulated carriers; when constant wave
(CW) carriers are used in the AGC mode, the levels of the
carriers are 2.0 dB lower than they are when modulated
carriers are used. The DC output of the comparitor adjusts
the variable PIN attenuator.
Optical Signals Laser: The laser converts the RF signals to optical signals that
exit the module through an optical connector on the front
panel. (Output power varies by model.)
Control Signals A sample of the optical signal enters a closed loop circuit that
monitors the laser’s output power and temperature.
Photodetector: A photodetector captures this sample and
converts it to a DC voltage representing the optical output
power. Then, this voltage is sent to various monitoring
circuits.
•An optical power monitor circuit compares the voltage to a
factory-set reference level and generates a control signal.
•A bias control circuit receives information from the monitor
circuit and uses it to adjust the optical output power of the
laser, maintaining a constant power level. This control
circuit also receivesthe AutomaticShutdown signal, from a
2RRX return receiver, FRX forward receiver, or a remote
monitoring source. If triggered, the Automatic Shutdown
signal breaks the closed loop, disabling the laser.
•The control circuit also receives signals from the safety
interlock. If the shield protecting the optical connection is
removed, the safety interlock breaks the closed loop,
disabling the transmitter.

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Transmitter
Communications Connector: The communications
connector collects control information, from this closed loop
and others inside the transmitter module, and sends it
through an edge connector on the transmitter’s rear panel to
the shelf. When installed, the optional network interface card
(NIC) enables local and remote monitoring of transmitter
performance.
Thermoelectric Control Circuit: A second closed loop
circuit monitors the internal temperature of the laser,
adjusting it to maintain a constant level.
DC Power DC Power: Power enters the transmitter through the 10-pin
connector on the rear of the module.

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Automatic Shutdown
Automatic Shutdown prevents the transmission of light
through severed fiber optic cables.
NOTE
If you plan to use the Automatic Shutdown feature, you must
set the transmitter to support this feature before you install the
transmitter. Automatic Shutdown is factory set to OFF.
For more information on
Automatic Shutdown in
redundant systems, see
DT-Switch Driver.
Automatic Shutdown of the transmitter is triggered only
under the following conditions:
•the transmitter is part of a two-way optical link,
•both the return receiver and the transmitter in the link are
set up to communicate the logic signal over the same
communication line, and
•the return receiver senses an absence of light in the return
path and sends the necessary logic to the transmitter to
disable it.
Automatic Shutdown is an
active process that disables a
transmitter only when the
transmitter receives the
required logic signal. Absence
of the logic signal will not
disable the transmitter, so this
module will operate normally
if no return receiver is in place
or Automatic Shutdown is not
used.
Return receivers can shut down transmitters that reside in
the same shelf or in different shelves:
•For modules in the same shelf, no additional equipment is
needed because the Automatic Shutdown logic signals
travel from the return receiver to the transmitter via the
shelf’s back panel.
•For modules in separate shelves, the logic signal exits the
return receiver and travels to the shelf’s manual shutdown
connector on the Diamond Transport shelf’s back panel.
The logic signal passes through a ribbon cable to the
correct shelf and then travels through the shelf’s back
panel to the correct transmitter.
To carry the logic signal between shelves, install a ribbon
cable with a 16-pin connector on each end.