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Extron Electronics - Multiplexing AV Signals in Fiber Optic Systems 01/26/2012 Revision 1.0
Table of Contents
Multiplexing Signals in Fiber Optic Systems ................2
Bidirectional Signaling ...............................................4
AV Signal Transmission Distance ................................4
Daisy-chaining ..........................................................5
Secure Systems ........................................................6
Switching and Distribution .........................................6
Summary .................................................................9
Abstract
A fiber optic AV system converts video,
audio, and control signals into one or
more serial digital streams of light pulses
for transmission along optical fiber.
Common multiplexing techniques include
time division multiplexing TDM and
wavelength division multiplexing WDM.
This paper examines both methods to
help designers and integrators make the
appropriate decisions when selecting
equipment for a fiber optic AV system.
Multiplexing AV Signals in Fiber Optic Systems
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1
23 2 1
3 2 1
3
1
2
3
Serializer
Deserializer
Serializer Deserializer
Transmitter Receiver
DVI - Clock
DVI - TMDS 2
DVI - TMDS 1
DVI - TMDS 0
RS-232 Send
AUDIO
DVI - Clock
DVI - TMDS 2
DVI - TMDS 1
DVI - TMDS 0
RS-232 Send
AUDIOA-to-D
ConverterD-to-A
Converter
E-to-OConverter
O-to-EConverter
Extron Electronics - Multiplexing AV Signals in Fiber Optic Systems 01/26/2012 Revision 1.0
Multiplexing Signals in Fiber Optic SystemsTime Division MultiplexingTDM combines multiple digital signals into a single serial digital bit stream. A specialized
circuit, called a serializer, allocates parallel input streams into time slots in the serial
output. In a fiber optic system, the serial bit stream is transmitted as a single wavelength
down a fiber optic cable. On the far end of the channel, a deserializer reconstructs the
original parallel signal from the serial bit stream as shown in Figure1. The serial data
rate must be sufficiently fast to ensure no data is lost. Fiber optic transmitters and
receivers for high resolution AV signals typically operate at a 4 to 6Gbps data rate.
TDM is used to transmit a wide variety of signals, including HDMI, DVI, multi-rate
SDI, RGB, HD and SD component video, S-video, composite, USB, audio, and RS-232
control. In modern fiber optic AV systems, analog video and audio are converted to
digital signals, avoiding nonlinear effects that plague direct optical conversion of analog
signals. Digital transmission ensures high-resolution video is transmitted pixel-for-pixel
along the fiber optic cable.
The transmitter in Figure2 accepts HDMI/DVI video, stereo audio, and RS-232 control
signals. The multiplexer combines the signals as a serial stream of digital pulses. An
electrical-to-optical E-to-O converter changes the digital pulses to light pulses at a
single wavelength for transmission down the fiber. The receiver on the far end converts
the signal from optical to electrical O-to-E before deserializing to restore the original
signal.
Figure 1: Serializer Deserializer
Figure 2: TDM Fiber Optic Transmitter and Receiver for HDMI/DVI, Audio, and Control
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WDMMultiplexer/
De-Multiplexer
WDMMultiplexer/
De-Multiplexer
DVI - Clock
DVI - TMDS 2
DVI - TMDS 1
DVI - TMDS 0
DVI - Clock
DVI - TMDS 2
DVI - TMDS 1
DVI - TMDS 0
RS-232 Send
RS-232 Return RS-232 Return
RS-232 Send
O-to-EConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
O-to-EConverter
O-to-EConverter
O-to-EConverter
O-to-EConverter
O-to-EConverter
MultipleWavelengths
Over a Single Fiber
Transmitter Receiver
Extron Electronics - Multiplexing AV Signals in Fiber Optic Systems 01/26/2012 Revision 1.0
Wavelength Division MultiplexingWDM refers to transmitting two or more optical signals at different wavelengths along
a single fiber. Multiple wavelengths traveling down a fiber is similar to multiple radio
signals traveling through the air at different frequencies. Each wavelength can carry a
different signal that is independent of the other wavelengths. Additionally, the different
wavelengths can travel in the same or opposite directions, enabling bidirectional
optical communication over a single fiber as shown in Figure3. As long as the optical
converters have a sufficiently high bandwidth, WDM enables the original signal format
and data rate to be maintained in both the electrical and optical domains.
WDM is suitable for any application where multiple signals are transmitted over fiber
optic cabling. The signals can be completely independent, such as for different channels
in a cable television environment, bidirectional USB or RS-232 signals, components of
a multi-lane HDMI or DVI signal, or a combination of these. Each signal is applied to
a different wavelength for independent transmission along the same fiber optic cable.
The WDM transmitter and receiver shown in Figure3 enable transmission of an HDMI/
DVI signal over fiber optic cable. The transmitter has five inputs and one output.
Each input has its own E-to-O converter with a laser diode that operates at a unique
wavelength. A special device called a WDM multiplexer/de-multiplexer combines the
various wavelengths for transmission down a fiber optic cable.
Figure 3: WDM Fiber Optic Transmitter and Receiver for HDMI/DVI
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t Skew
t Skew
Serializer Deserializer
Transmitter Receiver
DVI - Clock
DVI - TMDS 2
DVI - TMDS 1
DVI - TMDS 0
RS-232 Send RS-232 Send
AUDIO
DVI - Clock
DVI - TMDS 2
DVI - TMDS 1
DVI - TMDS 0
AUDIO
RS-232 ReturnRS-232 Return
A-to-DConverter
D-to-AConverter
E-to-OConverter
O-to-EConverter
E-to-OConverter
O-to-EConverter
Switch
Extron Electronics - Multiplexing AV Signals in Fiber Optic Systems 01/26/2012 Revision 1.0
The WDM multiplexer/demultiplexer also separates the optical signal used for the return
data, which operates at a wavelength different from the inputs. The return data optical
signal passes through an O-to-E converter to recover the original signal.
The WDM receiver shown in Figure 3 has one input and five outputs. The WDM
multiplexer/demultiplexer in the receiver separates the optical signals, sending each to
a separate O-to-E converter.
Bidirectional SignalingBidirectional signals, such as USB, RS-232, or Ethernet, are used in a wide variety of
AV applications. As shown previously in Figure3, a WDM system transmits bidirectional
signals over a single fiber using a unique wavelength for the return data. In a TDM
system, single wavelength transmission is inherently unidirectional, so bidirectional
signaling is accomplished by using a second fiber as shown in Figure5.
AV Signal Transmission DistanceIn a WDM system, the maximum transmission distance is affected by optical loss, fiber
bandwidth, and inter-channel skew. Optical loss equates to attenuation in the fiber,
connections, and splices. The loss budget, determined by transmitter output power and
receiver input sensitivity, is the maximum amount of allowable optical loss in the fiber
link between the transmitter and receiver. Fiber bandwidth is the maximum frequency
or data rate that can be transmitted along a given length of fiber optic cable. Skew
is caused by the various wavelengths propagating at different speeds along the fiber
as shown in Figure4. The result is similar to skew created by varying twist ratios in
Category cable within a twisted pair system.
Figure 4: Inter-Channel Skew in WDM Applications Limits Transmission Distance
Figure 5: Two-Fiber Bidirectional Signaling in a TDM System
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ScatteringWater Peaksin OS1 Fiber
OS2 Fiber
Absorption
ATTENUATION
WAVELENGTH
1300850 1550
HDMI/DVI Transmission Distance Over OM4 Multimode FiberHDMI/DVI Transmission Distance Over OM4 Multimode Fiber
TDM
WDM2
1. Based upon a pixel clock of 225 MHz and maximum inter-channel skew of 1.78 ns.2. Based upon a pixel clock of 165 MHz and maximum inter-channel skew of 2.42 ns.
WDM1 300 meters (984 feet)
400 meters (1,312 feet)
2,000 m (6,561 ft)
Extron Electronics - Multiplexing AV Signals in Fiber Optic Systems 01/26/2012 Revision 1.0
The amount of skew in a WDM system depends upon the range of wavelengths used
in the system. In multimode systems using wavelengths around 850nm, skew can be
the dominant effect limiting transmission distance. For example, an HDMI system with
a 225MHz pixel clock has a maximum allowable inter-channel cable skew of 1.78ns.
A popular device used in multimode WDM HDMI and DVI extenders has a specified
maximum distance around 300meters (984feet) before the skew exceeds 1.78ns. The
same device can operate up to 400meters (1,312feet) for an HDMI or DVI signal with
a 165MHz pixel clock to allow a maximum skew of 2.42ns.
A TDM system transmits the fiber optic signal at a single wavelength, such that the entire
signal propagates at the same speed. With negligible skew, the maximum transmission
distance is limited only by the available loss budget and system bandwidth. A well-
managed loss budget and use of high-bandwidth, laser-optimized OM4 fiber enables
multimode TDM systems to achieve distances up to 2km (6,561 feet), as shown in
Figure6. As a result, TDM systems achieve much greater transmission distances than
WDM systems used for AV signal extension.
Singlemode systems use long wavelengths around 1310 nm or 1550 nm. At these
wavelengths, WDM systems experience less inter-channel skew to achieve longer
transmission distances. A typical WDM singlemode system for HDMI/DVI signals
transmits up to 12 km (7.5 miles), compared to 30 km (18.75 miles) for a TDM
singlemode system. However, not all WDM systems support OS1 fiber, which is the most
common type of installed singlemode fiber. WDM systems with wavelengths around
1390nm suffer high attenuation in OS1 fiber due to water peak absorption as shown
in Figure7.
Attenuation severely limits the transmission distance. Around the 1390nm wavelength,
OS1 fiber attenuation can 4dB/km or more due to water peak absorption. Assuming
a loss budget of 10 to 13dB, the maximum transmission distance is only 2 to 3km
at this wavelength. In order to achieve longer transmission distance, this type of WDM
system requires OS2 low water peak singlemode fiber. Alternatively, a singlemode TDM
system uses either a 1310nm or 1550nm wavelength, where OS1 fiber attenuation
is typically 1dB/km or less, so it operates at its full distance capability over both OS1
and OS2 fiber types.
Daisy-chainingDaisy-chaining allows a signal to be delivered to multiple destinations without the need
for routing or distribution equipment, or multiple transmitters as shown in Figure8. An
AV signal from a single transmitter, or from a single output on a matrix switcher, is sent Figure 8: Daisy-chain Configuration
Fiber Optic
Receiver
Fiber Optic
Receiver
Fiber Optic
Receiver
Figure 7: Attenuation in Optical Fiber
Figure 6: TDM Systems Experience Negligible Skew to Achieve Longer Transmission Distance
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Deserializer
Receiver
DVI - Clock
DVI - TMDS 2
DVI - TMDS 1
DVI - TMDS 0
RS-232 Send
AUDIO
RS-232 Return
TO NEXT RECEIVER IN DAISY CHAIN
D-to-AConverter
O-to-EConverter
E-to-OConverter
Switch
UnidirectionalFiber Optic Transmitter
Glass Fiber
UnidirectionalFiber Optic
Receiver
Public Black
AV Source
Secure Red
AV System
Extron Electronics - Multiplexing AV Signals in Fiber Optic Systems 01/26/2012 Revision 1.0
to a receiver with daisy-chain capability. The receiver provides a loop-out signal that is
sent to the next receiver in the daisy-chain. This configuration utilizes a single fiber from
the transmitter or matrix output to the first receiver in the chain. A single fiber connects
each consecutive receiver in the chain for efficient use of the fiber infrastructure. A
daisy-chain configuration is ideal for digital signage applications.
In a TDM system, the second fiber used for bidirectional communications is often
available as a loop out for creating a daisy-chain configuration as shown in Figure9.
Since there is a single bit stream, retransmission of the signal requires only a single
E-to-O converter. Alternatively, a WDM system is transmitting multiple bit streams,
requiring multiple optical converters and an additional WDM multiplexer/demultiplexer
to implement a loop-through. Therefore, a WDM receiver typically has only a single fiber
connection, and cannot be connected in a daisy-chain configuration.
Secure SystemsSecure environments include any system that deals with sensitive information, such as
government and military briefing rooms, emergency operations centers, or a corporate
presentation or planning room for proprietary technology. Many of these systems must
access information from both secure and public sources. Secure sources are referred to
as red signals, while public sources are referred to as black signals.
The detailed requirements for secure systems are often classified and not available to
the public, but general guidelines have been declassified. Secure systems with black
sources must take great care to ensure red information does not leak out through
the connection to the black source. Red and black systems must be electrically
isolated from each other. In a copper-based system, red and black signals must remain
physically separated. Since fiber optic cables are made of glass, a fiber optic system is
preferred as it provides near-perfect electrical isolation between black and red signals,
see Figure10.
Secure systems require that signals from public sources be unidirectional. Transmission
of any signal from a red secure system to a black unsecure system is not permitted.
Because of this, TDM fiber optic systems are preferred over WDM systems. Bidirectional
fiber optic devices that use WDM techniques are prohibited from use to connect a black
source to a red system.
Switching and Distribution
Active Switching and Distribution in AV SystemsSwitching systems used in fiber optic AV systems typically employ optical input-
electrical switching-optical output OEO technology. The optical signal is converted
to the electrical domain at the input of the router, switcher, or distribution amplifier.
Figure 9: TDM Receiver Configured for Daisy Chain
Figure 10: TDM is Preferred in Secure Fiber Optic AV Systems
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INPUT 1
INPUT 2
INPUT 3
INPUT 4
INPUT N
INPUT 1
INPUT 2
INPUT 3
INPUT 4
INPUT N
O-to-EConverter
O-to-EConverter
N x NMatrix Switcher
O-to-EConverter
O-to-EConverter
O-to-EConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
ANAHEIM, CA
RESETRS232/RS422
REMOTE LAN
ACT LINK
100-240V 50/60Hz
1.2A MAX.
100-240V 50/60Hz
1.2A MAX.
REDUNDANT
PRIMARY
PRIMARY POWER SUPPLYDISCONNECT BOTH POWERCORDS BEFORE SERVICING REDUNDANT POWER SUPPLY
FAN ASSIMBLY
FAN ASSIMBLY
1 - 1
617
- 32
33 -
4849
- 64
65 -
8081
- 96
97 -
112
113
- 128
129
- 144
A B C D E F G H I J K L M N O P
OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN
A B C D E F G H I J K L M N O P
OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN
A B C D E F G H I J K L M N O P
OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN
A B C D E F G H I J K L M N O P
OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN
A B C D E F G H I J K L M N O P
OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN
A B C D E F G H I J K L M N O P
OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN
A B C D E F G H I J K L M N O P
OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN
A B C D E F G H I J K L M N O P
OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN
A B C D E F G H I J K L M N O P
OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN
12V 0.3A MAX
FOX 3G HD-SDI
HD/SDI IN
POWER
BUFFERED OUTPUTS
MODEOPTICAL
RxTx
1 21 2
ON
12V 0.3A MAX
FOX 3G HD-SDI
HD/SDI IN
POWER
BUFFERED OUTPUTS
MODEOPTICAL
RxTx
1 21 2
ON
S
M
M
S
M
S
S
M
S
FOX AV Rx
Y/VID
OUTPUTS
RS-232OVER FIBER
RS-232REMOTE
Tx Rx Tx Rx
AUDIO
L R
RxTx
ALARM
1 2R-Y
B-Y/C
S-VID
OPTICAL
POWER12V 0.8A MAX
FOX 500 TX100-240V 0.3A
50/60 Hz
AUDIO INPUTS
RGB INPUT
R G B
H/HV V
ORL R
RS-232PASS THRU
TX Rx NA
RS-232CONTROL ALARM
* OPTIONAL FORRETURN DATA
TX Rx 1 2
INPUT LOOP THRU
RGB
OPTICAL1 2*
LIN
K
LIN
K
FOX AV Tx
Y/VID
INPUTS
RS-232OVER FIBER
RS-232REMOTE
Tx Rx Tx Rx
AUDIO
L R ALARM
1 2R-Y
B-Y/C
S-VID
OPTICAL
POWER12V 0.8A MAX
RxTx
FOXBOX Tx VGA
RGB
AUDI
O
OPTICAL
RxTx
LIN
K
LIN
KCONFIG
FOXBOX Rx DVI Plus
DVI
AUDI
O
OPTICAL
RxTx
LIN
K
LIN
KCONFIG
FOX 500 Rx100-240V 0.3A
50/60 Hz
AUDIO OUTPUTS
RGB OUTPUT
R G B
H V
L R
RS-232PASS THRU
TX Rx NA
RS-232CONTROL ALARM
* OPTIONAL FORRETURN DATA
TX Rx 1 2S
RGB
OPTICAL2* 1
LIN
K
LIN
K
FOX AV TransmitterMultimode
FOX AV ReceiverMultimode
FOX Matrix 14400Modular Fiber Optic Matrix Switcher
FOXBOX DVI Plus ReceiverSinglemode
FOXBOX VGA TransmitterSinglemode
FOX 500 RGB ReceiverSinglemode
FOX 3G HD-SDI TransceiverSinglemode
FOX 500 RGB TransmitterMultimode
FOX 3G HD-SDI TransceiverMultimode
Singlemode HD-SDIMultimode
FOXBOX Tx HDMITransmitter Multimode
FOXBOX SR HDMIScaling Receiver Multimode
MUTI-RATE SDI INPUTS
HGA D E FCB
MUTI-RATE SDI OUTPUTS
HGA D E FCB
MUTI-RATE SDI INPUTS
HGA D E FCB
MUTI-RATE SDI OUTPUTS
HGA D E FCB
A B C D E F G H I J K L M N O P
OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN 3G P BNC
A B C D E F G H I J K L M N O P
OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN OUT IN 3G P BNC
FOXBOX Tx HDMI
OPTICALHDMI INPUT AUDIO INPUT
RS-232OVER FIBER ALARM
Tx Rx 1 2
POWER12V 1.0 A MAX
LIN
K
LIN
K
RxTx
AUD
IO
HD
CP
HD
MI
CONFIG
HDMI LOOP THRUEDID MINDER 50Hz
AUDIO
DIGITAL
ANALOG60Hz
1 2
FOXBOX Tx HDMI FOXBOX SR HDMI
LIN
K
LIN
K
OPTICAL
RxTx
HDMI
AUDIO
OUTPUTS
REMOTERS-232
Tx Rx
RS-232OVER FIBER ALARM
Tx Rx 1 2
POWER12V 1.0 A MAX L R
OFF
ONHDMI AUDIO
POWER
PHONES
INPUT
MIXING
EXT 1-4
IMX
5-8REC
REC
CH1 5 CH2 6
UNITY VARIABLE
CH3 7 CH4 8 CUE
CUE
L
R MONITOR
PREVIEW AUTO EDIT
DMC EDIT DELETE
REVIEW
LIST GOOD SHOT MARK TRIM
CH1 5 CH2 6 CH3 7 CH4 8
PB
REC
PB
REMOTE EJECT1(9P) 2(50P) RS-232C
MPEG IMX Digital BETACAM HDCAM HDCAM High DefinitionVideo System
MEMORY
REC/ERASE AUDIO
ENTRY
PREROLL
REW
REC
PLAY
EDIT
F FWD
STANDBY
STOP
IN
IN
OUT
OUT
REC INHI
REVER
SE FORWARD
JOG
SHUTTL
E VAR
F1 F2 F3 F4 F5 F6
JOG
HOME
SHUTTLE/VAR
DISPLAYFULL/FINE
CHANNELCONDITION
ASSEMBLE INSERT
VIDEO CH1 CH2 CH3 CH3 CUE
RESET
TC
00:00:00:00KEY INHIALARM
PUSH/SHIFT
MULTICONTROL
PLAYER
RECORDER
HD SDI HD SDI HD SDI HD SDI
db db db db0
10
20
30
40
50
0
10
20
30
40
50
0
10
20
30
40
50
0
10
20
30
40
50
db0
10
20
30
40
50
H
COMMUN
ICATION
Tx
COMMUN
ICATION
Tx
Extron Electronics - Multiplexing AV Signals in Fiber Optic Systems 01/26/2012 Revision 1.0
It is then processed in the electrical domain, and restored to an optical signal at the
output. OEO systems restore full transmission power level on the output to preserve
the optical loss budget. The use of OEO technology avoids the losses that occur in
optical input-optical switching-optical output OOO systems that use passive splitters
to distribute optical signals to multiple destinations, which is particularly important when
multicasting a fiber optic AV signal to several displays.
Switching and Routing Fiber Optic TDM AV SignalsTDM switching systems process a single serial bit stream for each signal to produce an
efficient, compact design. The single wavelength/single fiber switching system performs
a single E-to-O conversion for each input and a single O-to-E conversion on each output
as shown in Figure11. High-speed digital switching ensures pixel-for-pixel performance
for high resolution video signals. The matrix switcher also maintains the serial format of
the signal to simplify switching and maintain proper timing.
Maintaining the serial digital bit stream enables switching to be independent of the
underlying video format as shown in Figure 12. This allows the distribution system
to support a wide variety of digital signals, including HDMI/DVI, multi-rate SDI, USB,
RS-232, and other digital signals. Signal types are defined by the endpoints the
transmitter and receiver. Serial digital signals, such as multi-rate SDI, are supported in
their native format, enabling local inputs and outputs.
Bidirectional signals are easily handled by using two fibers, an input and output that
are switched together. However, multi-lane signals such as HDMI, DVI, and RGB require
external transmitters and receivers to provide local inputs and outputs. The ability to
support a wide variety of signals simplifies upgrading of sources and displays with
minimal impact on the switching and routing system.
Figure 11: Matrix Switcher for TDM Systems
Figure 12: TDM Fiber Optic Signal Routing Easily Handles Multiple Video Formats
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WDMMultiplexer/
De-Multiplexer
WDMMultiplexer/
De-MultiplexerTMDS Clock
N x N Matrix Switcher
TMDS 2N x N
Matrix Switcher
TMDS 1N x N
Matrix Switcher
TMDS 0N x N
Matrix Switcher
DATAN x N
Matrix Switcher
RETURN DATAN x N
Matrix Switcher
INPUT 1
O-to-EConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
O-to-EConverter
O-to-EConverter
O-to-EConverter
O-to-EConverter
O-to-EConverter
OUTPUT 1
WDMMultiplexer/
De-Multiplexer
WDMMultiplexer/
De-Multiplexer
INPUT N
O-to-EConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
E-to-OConverter
O-to-EConverter
O-to-EConverter
O-to-EConverter
O-to-EConverter
O-to-EConverter
OUTPUT N
Extron Electronics - Multiplexing AV Signals in Fiber Optic Systems 01/26/2012 Revision 1.0
The efficient design of a TDM matrix switcher enables a large number of inputs
and outputs in a compact space with moderate power requirements. The Extron
FOXMatrix14400 shown in Figure12 provides a full 144x144 non-blocking fiber optic
matrix switcher in an 8U frame.
Switching and Routing Fiber Optic WDM AV SignalsA matrix switcher for WDM signals is larger and more complex than that used for a
TDM signal as shown in Figure13. Each fiber optic input includes the complete WDM
receiver circuit to convert the optical signal to an HDMI/DVI format. The core switching
system supports the multi-lane format of an HDMI/DVI signal, which requires multiple,
parallel internal switching components. Each fiber optic output includes the complete
WDM transmitter circuit to convert the HDMI/DVI signal back into an optical signal. The
additional switching resources and I/O circuitry causes WDM matrix switchers to be
large, high powered, and require additional cooling. Since the core switching system
supports HDMI/DVI signals in their native format, local inputs and outputs are easily
added to the matrix. Supporting other signal types, such as multi-rate SDI, requires
external converters to change the original signal into a DVI/HDMI signal. WDM matrix
switchers do not typically support local multi-rate SDI signals.
Figure 13: WDM Matrix Switcher
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FOXMatrix14400
144x144
System (A)TDM
Design
Rack Height
System (B)WDM w/
BidirectionalSignal
System (C)WDM w/
UnidirectionalSignal
Third-partyWDMMatrix
Switcher80x80
Third-partyWDMMatrix
Switcher144x144
16U15U
8U
Extron Electronics - Multiplexing AV Signals in Fiber Optic Systems 01/26/2012 Revision 1.0
Relative Matrix Sizes of TDM and WDM Matrix SwitchersA high speed digital matrix switcher in a TDM system operates efficiently, typically
using less power than a WDM matrix switcher. The efficient design also enables a
TDM matrix switcher to occupy less rack space. For example, System A in Figure14
is the Extron FOX Matrix 14400 144x144 fiber optic matrix switcher that occupies
eight rack units. It is compatible with the complete family of FOX Series transmitters
and receivers to supports HDCP-compliant HDMI, DVI, multi-rate SDI, RGB,
HD/SD component, S-video, composite video, USB, stereo audio, and RS-232 control
signals. A matrix board is also available to provide local multi-rate SDI signals.
SystemB in Figure 14 is an 80x80 WDM matrix switcher that is almost twice the size
at 15rack units, and supports HDCP-compliant HDMI and DVI signals. It lacks support
for multi-rate SDI signals, standard definition video, audio, USB, and control, but does
provide local HDMI and DVI inputs and outputs. SystemC in Figure14 is a 144x144
WDM matrix switcher that consumes 16rack units, but only supports non-HDCP DVI,
VGA, HD component video, audio, and one-way RS-232 control. It lacks support for
multi-rate SDI signals, standard definition video, and bidirectional RS-232. As a WDM
matrix switcher, it does support local DVI or VGA inputs and outputs, but not HDCP-
compliant HDMI. The TDM system is the most compact design with complete support
for AV signal types. Support for local multi-rate SDI signals can be provided within the
modular matrix frame. Local inputs and outputs for other signal types are provided with
the compact transmitters and receivers. WDM systems require significantly more rack
space for the matrix switcher and support fewer signal types. For example, SystemB in
Figure14 would consume 30rack space units in order to provide the same switching
resources as in the FOXMatrix14400. The FOXMatrix consumes significantly less rack
space, even with the addition of a few transmitters and receivers for local HDMI inputs
and outputs.
SummaryBoth TDM and WDM are common technologies implemented in fiber optic AV systems.
Each has its own unique advantages and challenges. The table below compares and
contrasts the two technologies:
Figure 14: Relative Size of Matrix Switchers
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Extron Electronics - Multiplexing AV Signals in Fiber Optic Systems 01/26/2012 Revision 1.0
Extron Electronics, headquartered in Anaheim, CA, is a leading manufacturer of professional AV system integration products. Extron products are used to integrate video and audio into presentation systems in a wide variety of locations, including classrooms and auditoriums in schools and colleges, corporate boardrooms, houses of worship, command-and-control centers, sports stadiums, airports, broadcast studios, restaurants, malls, and museums.
www.extron.com 2012 All rights reserved.
TDM WDM
Up to 2 km on multimode fiber 300 to 400 m typicalUp to 30 km on singlemode fiber Up to 12 km on OS2 fiber. OS1 depends on wavelengthsBidirectional signaling Extend HDMI / DVI Signals Extend RGB Signals Extend multi-rate SDI signals Requires ConversionHDCP Support USB Extension Daisy Chain Capability w/ loop-through Not typically supported
Preferred for secure systems Low power matrix switcher High I/O density matrix switcher HDMI / DVI Local I/O w/ external converters RGB Local I/O w/ external converters Digital-to-analog conversion
Multi-Rate SDI Local I/O
Comparison of TDM and WDM Technologies