Download Optical Power

Coaxial Architecture
Tree-and-Branch Architecture
Express Trunk
HFC Architecture
HUBS
node
Tap
Customer
Homes
Businesses
amp in building
Rural Network
Other cable
outputs
Fiber
Optic
(Node) Optics
RX/TX
Headend
Active Device
Cable
RF
Near Passive Network
11
26
14
29
Headend
or Node
Two-Way Tap
Four-Way Tap
Eight-Way Tap
Directional Coupler
Splitter
Optics
RX/TX
29
24
LPI
LPS
21
17
Passive Network
2
9
Headend
or Node
2
6
23
20
17
17
11
Node
Two Way Tap
Four Way Tap
Slope Equalizer
4
Sample Headend
1
Analog Video
55-550 MHz
2 Way
RF
splitter
Com21
out
430MHz
2 Way
RF splitter
HCX comController
DT 815 Amp
5008ET2
2
3
EDFA
Hub
Public switch
EDFA
2RRX
HUB
Return TX
2RRX
DWDD
Return TX
DWDM
Connector Parts
Boot
Body
Ferrule
Types of Connectors
Biconic
FC
ST
SC
D4
Optical Loss Example
Coaxial Plant Design
and Operation
Optical Transmitters and
Receivers
Topics
• Overview
• Optical Transmitters
• Optical Receivers
• Units of Optical Power
• Power Budget
Optical Transmitter and Receiver
Input Electrical
Signal
Reproduced
Electrical
Signal
Optical Signal
Optical Fiber
Transmitter
Receiver
Optical Transmitter
Drive Level
RF Input
Control
Drive Level
Test Point
Optical Fiber
Optical
Connector
Laser
Laser Drive Levels
Optical Output Power
Clipped Output
Laser
Performance
Curve
Modulated
Optical Output
Current
Threshold
Current
Input RF
Bias
Current
Optical Receiver
Bias Voltage
Fiber
Optical
Connector
Test Point
Photo Detector
Pre
Amp
Post
Amp
RF
Out
Units of Optical Power
Optical Power Equations
dBm = 10 log mW
mW = inverse log (dBm/10)
+/-10dB Optical Power Table
Optical Power (dBm)
30
20
10
0
-10
-20
-30
Optical Power (mW)
1,000
100
10
1
0.1
0.01
0.001
Power Budget Formula
P b = T p - Rin where
P b = the Power Budget
T p = output Power of the Transmitter and
R in = required input to the receiver
Optical Node
System RF out
NOR
NRT
Optical Node Operation
Post
Amp
Node/Amplifier Block Diagram
RF to
Light
Converter
L
20
dBmV
Post
Amp
Pre
Amp
Attenuator
Level
Control
Tilt
Generator
Splitter
Light
to RF
Converter
H
H
L
Post
Amp
H
L
to RF
Post
Amp
Combiner
H
L
-20 dB
Rf TP
Forward Optical Receivers/NOR’S
RF
Gain
adjust
9A
pad
Optical
monitoring T/P
Optical
alarm
-30 down
Test Point
Diamond Net
RF Module
Coaxial Plant Design
and Operation
Amplifier Technology
Topics
• Semiconductor Configurations in CATV
–Single - Ended Amplifier
–Push - Pull Amplifier
–Parallel - Hybrid Amplifier
Semiconductor Amplifier
Configurations
Single - Ended Amplifier
2nd Harmonic
plus Noise
Push - Pull Amplifier
Parallel - Hybrid Amplifier
Push
Pull
Stage
Pin
Pout
Push
Pull
Stage
ADVANTAGES: High Gain and Reduced Distortions
Coaxial Plant Design
and Operation
Amplifier Configurations
Objectives
• Describe the most common amplifier
configurations and discuss their usage.
• Identify the components for each of the amplifier
configuration and explain their functions and
importance.
Forward Amplifier Characteristics
Amplifier Output Tilt
11dB of tilt @ 750 MHz
Attenuator Function
20 dBmV
20 dBmV
10 dBmV
10 dBmV
0 dBmV
50 MHz
750 MHz
0 dBmV
50 MHz
750 MHz
Equalizer Function
20 dBmV
Effect of Cable
10 dBmV
0 dBmV
50 MHz
10 dBmV
750 MHz
0 dB
10 dB
20 dB
50 MHz
Combined
Results
50 MHz
Effect of Equalizer
750 MHz
750 MHz
Response Equalizer
Examples of Peak to Valley
Responses. With Response
Equalizers Installed
These are available in
either bumps or traps
Equalizer Selection
20 dB
11 dB
12 dB
50 MHz
750 MHz
Interstage Eq Set for
desired Tilt @ Output
=
=
=
8 dB
62E750/11
50 MHz
750 MHz
Secondary Eq Set
Additional Tilt
11 dB
Low
DC
TP
High
Amplifier Block Diagram with
ALSC / AGC
Post
Amp
ALSC Optional Response Interstage
Plug In
Equalizer Slope Eq.
Inter
Stage
Amp
Dist
EQ
DC
TP
Pad
Post
Amp
Shorting
Stub to One
Secondary or
DC 4-8-or 12
DC
TP
High
Manual Interstage
Pre
Amp Gain Adj. Atten.
Low
Input
EQ
High
Input
Atten
Low
Low
High
Pad
Forward Amplifier Characteristics
Forward Sweep
SWEEP GEAR
SYSTEM
AMPLIFIER
METER
Sweep System Requirements
Fiber Optic Interconnect
Sweep
Transmitter
Headend
Combiner
Fiber
Transmitter
Node
AMP
1
Amp
6
Amp
5
Amp
4
Amp
3
Amp
2
Reference
*The remaining amplifiers in the cascade are compared to the reference.
Raw Sweep
Low Level Signal Telemetry
Coaxial Plant Design
and Operation
Frequency Response Specifics
Non Linear Cable Loss
Characteristics
Signal Level
Signal Level
Ideal Response
50 MHz
550MHz
Non Linear
50 MHz
Cable Kinks
Z Mismatch
550MHz
Hardware Points of Concern
Connector
Tap
Cable
Amplifier
Cable
Cable
Connector
Frequency Characteristics
Peak to Valley
Impedance Mismatch
RF Suckout
Low End Loss
Correcting the Characteristics of
an Amplifier Signature
Correcting the Characteristics of
an Amplifier Signature
54
750
Before
After
Forward Amplifier Characteristics
Forward Amplifier Characteristics
Thermal Control
(TGSC plug-in)
Optional
Test Point
-30 dB Resistive
Test Point
-30 dB Resistive
Automatic Gain
Control(AGC series
plug-in) Optional
Atten.
Equalizer
Pre-Amp
Post-Amp
H
Downstream
Input/
Upstream
Output
H
Downstream
Output/
Upstream
Input
L
L
L
Return Amplifier Module
LER series plug-in
Optional
Return RF
AC
+24 VDC
Test Point
Power
Supply
Surge
Arrestor
AC
+24 VDC
Surge
Arrestor
Thru Power
Plug
Forward Amplifier Characteristics
40dB gain
+48/35.5
Input=
11/17.7dB
+ 43.1 dBmV
33.6 dBmV
+38.0/31.5 dBmV
+32.5/29 dBmV
29dB
-0.4
Needs a minimum
of 8dBMv at 870MHz
Cable Losses
@870 MHz=
1.5dB/100ft
@50 MHz=0.5dB/100ft
23dB
-0.6dB
300ft=
4.5dB@870
1.5dB@50
Each port has
19/6.5dBmV out
20dB
-1.0dB
17dB
-1.5
14dB
2.0
11dB
-3.5
Each port has
15.5/12dBmV out.
Network Operation and
Maintenance Procedures
Coaxial Plant Design
and Operation
Intermodulation Distortions
Distortion Cause: Amplifiers
VCC
55.25MHz
Fs Amp
Fs
110.5MHz
Fs+ 2 Fs
2nd Harmonic
Intermodulation Distortion
Distortions
Cross
Discrete
Modulation
Third
Order
2nd
Order
Distortion
Discrete Second Order Distortions
B
A
55.25 MHz 121.25 MHz
175.25 MHz
229.25 MHz
Active
Carrier 1
Carrier 2
120.00 MHz
Carrier 1
Carrier 2
Beat Product
A-B = Carrier 1 +/- Carrier 2
Beat Products
230.50 MHz
A+B
CSO Beats in a 77 Channel System
N 60
COMPOSITE
SECOND ORDER (CSO)
U
Subtraction Beats:
M 50
CSO -F1, -F2, -F3
B
•E CSO(
Single Amp.) = CSO(Spec.) + 2*(Rated Output40
R Actual Output)
O
30
F
68 + 2*(46 - 48) =
B
Addition Beats
E 20
68 + 2*( -2 ) =
CSO +F1, +F2, +F3
A
T 10
68 + -4 =
S
64 dBc
50
100
200
300
400
Frequency in MHz
500 550
Discrete Third Order
Carrier 1
Carrier 2
Carrier 3
Active
Beat Product
Beat Product = Carrier 1 +/- Carrier 2 +/- Carrier 3
Composite Triple Beat Distortions
Cross Modulation
Video
Aural
Channel A Un-modulated Carrier
Channel B
Channel A with Cross Modulation from Channel B
Composite Triple Beat
Multiple Amplifiers
CTB#Amps = CTB1Amp - 20log (#Amps)
2 Amplifiers
CTB2Amps = 68- 20Log (2)
CTB2Amps = 68- 20 x .3
CTB2Amps = 62 dBc
This is true if all the amplifiers are identical.
CTB is 20 Log because it is a voltage function.
Cross Modulation Calculation
• XMOD ( Cascade ) =
–XMOD ( Single ) - 20Log ( N )
–where N is the number of amplifiers in
cascade.