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Transcript of Sweep Overview Mark Ortel Sales Support Eng. © 2005 JDSU. All rights reserved.JDSU CONFIDENTIAL &...
Sweep Overview
Mark Ortel
Sales Support Eng
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION2
Conditioning the Network for Triple Play Services
Know Your HFC Network
System Sweep and Ingress Suppression
Testing and Hardening the Drop (Home Wiring)
Line Conditioning to Optimize Two-way Plant Performance
Fiber Optic Testing Maintenance
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION3
Web BrowsingE-mail
Digital MusicVoIP
Digital Photos
Video on Demand
Video Mail
Online Gaming
Podcasting
Video Blogs
High Definition Video on Demand
All Video on Demand Unicast per Subscriber
Meg
abit
s p
er S
eco
nd
20
10
30
40
50
60
70
80
90
100
Time
Bandwidth Demand is Growing Exponentially
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION5
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION6
Voice Quality Impairments – it’s not always the plant!
PSTN
Cable
CMTS
CMTS
CMTS
Aggregationswitch
Core IPNetwork
HUB SITE
MEDIA POP
MEDIA POP
Trunk MediaGateway
Trunk MediaGateway
CableModem
MTA POTSPhone
HOMEBackground noise, handsetspeaker/mic interference,inadequate volume, insidewiring, mis-configured MTA
(CoS-Diffserv / firewallsettings), wireless phonedelay exacerbates echo
problems, MTA DSP/echocanceller performance
CABLE PLANTRF downstream and/or
upstream errors leading toIP packet loss, bandwidthcapacity limitations (esp.upstream) may lead to
CMTS congestion (droppedIP packets) and excessive
jitter (packet drops by codec)
Customer Problem?Cable Provider
Problem?
HUB SITEExcessive NE pollingand/or high utilization
lead to congestioncausing jitter, droppedpackets and increased
transit delay
UPSTREAM orDOWNSTREAM?
What’s the problem?
CORE IP NTWKHigh utilization lead to
congestion causing jitter,dropped packets and
increased transit delay,mis-configured routing
can cause inappropriatehops leading to increased
latency
MEDIA GW POPDSP codec
performance, echocanceller config., jitterbuffer config. / packet
drops
Telco Problem?
PSTNanalog problems on PSTNpath passed through to IP
network
Cable Provider Problem?
Where is the Problem?
What is the Problem?
CMTS-Blade-Port or Switch-
Slot-Port?
What’s the problem?
Router-Slot-Port?
LSP/VLAN, Route?
What’s the problem?
MediaGW-Slot-Port?DSP Card-Port-CPU?
What’s the problem?
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION7
‘Pre-HFC’ Networks
No Optics Standardized ‘Tree & Branch’ Architecture Few Amplifier Types Limited Operating Levels
Networks were optimized for forward plant performance with minimal reverse plant engineering.
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION8
‘Pre-HFC’ Networks
No Optics Standardized ‘Tree & Branch’ Architecture Few Amplifier Types Limited Operating Levels
Networks were optimized for forward plant performance with minimal reverse plant engineering.
Headend
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION9
HFC Networks
Combines fiber optics with coaxial distribution network Return path is more sensitive than the forward path Most of the ingress comes from home wiring on low value
taps Wide variety of hardware with many connectors
Today’s ‘HFC” networks must be optimized for both forward and reverse performance
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION10
HFC Network Architecture
NODE
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION11
HFC Network Architecture
NODE
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION12
CMTS
Downstream 0
Upstream 0
Upstream 1
Upstream 2
Upstream 3
Cable Modems
Cable Modems
Cable Modems
Cable Modems
Fiber Nodes
Basic DOCSIS® NetworkDownstream Laser and
Upstream Optical Receivers
Coax Fiber Coax
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION13
Types of Lasers used in HFC Networks
Fabry-Pérot (FP) – Less Expensive– Mediocre Performance– No Isolation or Cooling Required
Distributed Feedback (DFB)– Expensive– High Performance– Isolation and Cooling Required
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION14
Forward System
Diverging System Constant Outputs with Variable Inputs Fixed Signals
– video / audio / digital carriers
System Noise– is the sum of cascaded amplifiers
Balance or Align (Sweep)– compensate for losses before the amp
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION15
Forward Path Unity Gain
OUT+36 dBmV
OUT+36 dBmV
OUT+36 dBmV
OUT+36 dBmV
AMP # 1 AMP # 2 AMP # 3
AMP # 4
IN+12 dBmV
IN+11 dBmV
IN+10 dBmV
2 dB
8 dB 24 dB @ 750 MHz 23 dB @ 750 MHz
18
dB
@ 7
50
MH
z
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION16
Reverse System
Converging System Constant Inputs with Variable Outputs No Fixed Signals
– impulse digital carriers
System Noise– is the sum of all active components
Balance or Align (Sweep)– compensate for losses after the amp
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION17
Return Path Unity Gain
IN+20 dBmV
IN+20 dBmV
IN+20 dBmV
IN+20 dBmV
AMP # 1 AMP # 2 AMP # 3
AMP # 4
OUT+24 dBmV
OUT+26 dBmV
OUT+30 dBmV
2 dB
8 dB 4 dB @ 40 MHz 4 dB @ 40 MHz
2 d
B @
40
MH
z
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION18
Ingress and electrical noise
Common Path Distortion (CPD)
Thermal (intrinsic) noise
Laser clipping noise
Micro-Reflections
Reverse Path Impairments
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION19
There are a variety of impairments that can affect two-way operation.
They are classified in three main categories: stationary impairments, which include thermal noise, intermodulation distortion,and frequency response problems; transient impairments, which include RF ingress, impulse noise, and signal clipping; and multiplicative impairments, which include transient hum modulation and intermittent connections.
Reverse Path Impairments
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION20
Thermal noise —The majority of thermal noise is generated in active components. Besides choosing active equipment with a relatively low noise figure, there is little else that you can do about the thermal noise in active devices, other than ensure proper network alignment.
Reverse Path Impairments
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION21
Intermodulation distortion—The most common types of intermodulation distortion affecting the reverse path are second and third order distortions. These can be generated in amplifiers and reverse lasers. A more troubling type of intermodulation can occur in some passive components. It is known as common path distortion (CPD), and usually occurs at a dissimilar metals interface where a thin oxide layer has formed.
Reverse Path Impairments
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION22
Frequency response— Frequency response problems are due to improper network alignment, unterminated lines, or damaged components. When reverse frequency response and equipment alignment have been done incorrectly or not at all, the result can be excessive thermal noise, distortions, and group delay errors.
Reverse Path Impairments
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION23
RF ingress — The 5-40 MHz reverse spectrum is shared with numerous over-the-air users.
Reverse Path Impairments
Signals in the over-the-air environment include high power shortwave broadcasts, amateur radio, citizens band, government, and other two-way radio communications.
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION24
Downstream and Upstream Noise Additions
Headend Headend
Reverse System “Noise Funneling”
Ingress from seven amplifiers ends upat the headend.
Forward Signals
Noise
Noise
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION25
Impulse noise —Most reverse data transmission errors have been found to be caused by bursts of impulse noise. Impulse noise is characterized by its fast risetime and short duration.
Common sources include vehicle ignitions, neon signs, static from lightning, power line switching transients, electric motors, electronic switches, and household appliances.
Reverse Path Impairments
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION26
Impulse Noise in the Upstream
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION27
Sample: “Loose Plant” Performance History
• Average noise floor at 17 MHz varies consistently by time of day
• Indication of return path with an ingress problem.
•Maintenance now will prevent future problems
Single Frequency Time Window for 72 Hours from one return path
7:00AM 11:00PM 7:00AM11:00PM
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION28
Sample: ‘Tight’ Performance History
• 17 MHz noise floor tracked over time
• Average noise floor stays fairly flat and consistent over the 3 day period
Single Frequency Time Window for 72 Hours from one return path
Peak
Average
Minimum
InconsistentProblem(high peak,low average)
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION29
Sample: “Telephony” Performance History
Single Frequency Time Window for 3 days from one return path
• Average telephony signal at 36 MHz varies consistently by time of day
• Indication of higher telephony usage times
7:00AM 11:00PM 7:00AM11:00PM
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION30
6MHz CPD
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION31
Signal clipping —RF ingress and impulse noise can cause signal clipping, or compression, in reverse plant active components. Excessive levels from in-home devices such as pay-per-view converters also can cause clipping. Clipping occurs in reverse amplifiers and optical equipment.
Reverse Path Impairments
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION32
Ingress
75 – 90% of ingress originates in the subscriber’s home
To minimize the effects of ingress, operate the subscriber terminals (modems & set-tops) near maximum transmit level
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION33
Non-linear mixing from a diode junction
– Corrosion (metal oxide build-up) in the coaxial portion of the HFC network
– Dissimilar metal contacts
– 4 main groups of metals• Magnesium and its alloys• Cadmium, Zinc, Aluminum and its alloys• Iron, Lead, Tin, & alloys (except stainless steel)• Copper, Chromium, Nickel, Silver, Gold, Platinum, Titanium,
Cobalt, Stainless Steel, and Graphite
Second and third order distortions
Common Path Distortion (A.K.A. CPD)
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION34
24 MHz
Common Path Distortion (A.K.A. CPD)
CPD distortions are spaced at 6 MHz apart from each other starting at 6 MHz
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION35
DOCSIS®Modem Carrier
Wide band noise
beyond 42 MHz diplex roll-off
24 Hour Performance History Max Hold Detail Graph
Diplex roll-off above 42 MHz
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION36
Thermal Noise and Laser Noise
Maintain a tight control of reverse RF signal levels – Laser drive level too high
• causes excessive laser clipping– Laser drive level too low
• reduces C/N and C/I ratios
Reverse levels must be held to a relatively narrow ‘window’ in order to guarantee that they fall comfortably between a lower limit (imposed by the noise floor) and a higher limit (set by laser clipping noise)
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION37
Micro-reflections
Damaged or missing end-of-line terminators Damaged or missing chassis terminators on directional coupler, splitter, or multiple-output amplifier
unused ports Loose center conductor seizure screws Unused tap ports not terminated; this is especially critical on low value taps, but all unused tap
ports should be terminated with 75-ohm terminations (locking terminators without resistors or stingers do not terminate the tap port)
Poor isolation in splitters, taps and directional couplers Unused customer premises splitter and directional coupler ports not terminated Use of so-called self-terminating taps at feeder ends-of-line; these are the equivalent of splitters,
and do not terminate the feeder cable unless all tap ports are terminated Kinked or damaged cable (includes cracked cable, which causes a reflection and ingress) Defective or damaged actives or passives (water-damaged, water-filled, cold solder joint, corrosion,
loose circuit board screws, etc.) Cable-ready TVs and VCRs connected directly to the drop (return loss on most cable-ready devices
is poor) Some traps and filters have been found to have poor return loss in the upstream, especially those
used for data-only service
Causes:
RON HRANAC
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION38
Why Go Digital?
Efficiency
– Source signals are digital
• Standard and High Definition TV (SDTV, HDTV)
– High Speed Data and Digital Video is more efficient than analog
• Transmit equivalent of 6 to 10 analog channels (VCR quality) or 2 HDTV programs over one 6 MHz bandwidth
Quality
– Better Picture and Sound Quality
– Less Susceptible to noise
• Error detection and correction is possible
Flexibility
– Data-casting easily multiplexed into digital signal
– Higher Data Security
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION39
Generate Digital
What is Digital?
Source and Destination is digital data– Assign unique patterns of 1’s and 0’s
Transmission path is via an analog QAM carrier – Choice of modulation is the one that optimizes bandwidth
(data versus frequency ‘space’) and resiliency to noise
00 01 10 11 00 01 10 11
Receive Digital
QAM Analog Carrier
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION40
QAM combines QPSK and AM modulation. QAM uses 2 channels of information each carrying half
the data.
10 11
AM Modulator
AM Modulator
Bit StreamCarrier
Carrier + 90°
Combiner
I Channel
Q Channel
Quadrature Amplitude Modulation (QAM)
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION41
Vector Sum of I and Q Channels
Combining 2 carriers 90° of out of phase results in a carrier with amplitude and phase modulation
4 Levels of I
Channel
+ =
00
00
01 10 11
01
10
11
4 Levels of Q
Channel
..10 11..Data Stream
..10 11..
16 QAM
4 Levels of Q
4 Levels of I
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION42
Constellations, Symbols and Digital Bits
16 QAM
Each “dot” on constellation represents a unique symbol
Each unique symbol represents unique digital bits
Digital data is parsed into data lengths that encode the symbol waveform
4 Levels of Q Channel
4 L
evel
s of
I
Ch
ann
el
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION43
64 QAM and 256 QAM
64 QAM has 8 levels of I and 8 levels of Q making 64 possible locations for the carrier
256 QAM has 16 levels of I and 16 levels of Q making 256 possible locations for the carrier
8 Levels of Q Channel
16 L
evel
s of
I
Ch
ann
el
16 Levels of Q Channel
8 L
evel
s of
I
Ch
ann
el
64 QAM 256 QAM
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION44
QAM and CATV
16 QAM is part of the DOCSIS® 1.0/1.1 upstream specifications
64 QAM and 256 QAM is used for both digital video and DOCSIS downstream, allowing more digital data transmission using the same 6 MHz bandwidth
– Transmit equivalent of 10 to 12 analog channels (standard definition) or 2 HDTV programs over one 6 MHz bandwidth
Standard for data over Cable
– Cable systems provide higher signal to noise ratios than over-the-air transmission. A well designed and maintained cable plant meets these QAM signal to noise requirements
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION45
QAM Data Capacity (Annex B)
16 QAM(Upstream)
64 QAM(Downstream)
256 QAM(Downstream)
Symbol Rate (Msps)
2.560 (@ 3.20 MHz)
5.0569(@ 6 MHz)
5.3605(@ 6 MHz)
Bits per symbol
4 6 8
Channel Data Rate (Mbps)
10.24 30.3417 42.8843
Information bit rate(Mbps)
9.0 26.9704 38.8107
Overhead 12.11% 11.11% 9.5%
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION46
Constellation Display
The constellation is a visual representation of the I and Q plots
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION47
Effects of Noise and Interference
Ideal Locations
Noise and Interference moves the carrier away from its ideal location causing a spreading of the cluster of dots.
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION48
Modulation Error Ratio (MER)
Analogous to S/N or C/N A measure of how tightly symbols are recorded
with respect to desired symbol location
MER(dB) = 20 x log RMS error magnitude average symbol magnitude
Good MER– 64 QAM: 28 dB MER– 256 QAM: 32 dB MER
RMS errormagnitude
Average symbol
magnitude
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION50
Constellation Zoom
Zooming in on the constellation you can see how the carrier spread and how close it came to the decision boundaries.
Decision Boundaries
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION51
Digital Content – Analog Carrier
The Carrier, by the way, is ANALOG Modulation
Analog Content – Analog Carrier
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION52
PathTrak QAM Analyzer View – Good Node
QPSK & 16QAM Constellation
MER & Level Graphed over Time
MER & LevelAvg/Max/Min
Live MER, Level & Symbol Count
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION53
Interference causing intermittent low MER
Interference easily visible in 16 QAM
constellation
Interference easily visible in 16 QAM
constellation
Interference easily visible in 16 QAM
constellation
PathTrak QAM Analyzer View – Bad Node
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION54
“Back to the Basics” Troubleshooting
Majority of problems are basic physical layer issues Check AC power Most of the test strategy remains the same – divide
and conquer technique Check forward and return RF levels, analog and digital Check forward / reverse ingress Do a visual inspection of connectors / passives Replace questionable connectors / passives Tighten F-connectors per your company’s installation
policy– Be very careful not to over tighten connectors on CPE (TVs,
VCRs, converters etc.) and crack or damage input RFI integrity
System Sweep and Ingress Suppression
Why sweep?
Why suppress Ingress?
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION56
• Less manpower needed
• Sweeping can reduce the number of service calls
VOD not working
Internet not workingChannel 12 video
problemsCracked hardline
found with SWEEP
WHY SWEEP?
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION57
Success rate of finding and fixing the following problems using:– Signal Levels– TILT– Gain / Loss– Suck-outs (notches)– C/N– HUM– CTB/CSO Intermodulation– CPD - Forward and Reverse– Reverse Ingress– BER / MER– Reflections / Standing waves
What faults cause CATV signals to fail ?(80-90% of the time, the same faults…)
Source: Research 11/97-2/98 Market survey with 200 US and European CATV operators
21% Reverse Ingress
23% Signal Level Meters
11% BER Digital Analyzers
72% Forward & Reverse Sweep
5% Spectrum Analyzers
7% Visual TV-picture inspection
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION58
CATV amplifiers have a trade-off between noise and distortion performance
Tightly controlling frequency response provides the best compromise between noise and distortion.
WHY SWEEP?
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION59
Segmented Error Budgets
Test Critaria Measurement Goal Start Seeing Degradation on Call
Quality
Delay (1-way) < 100 ms > 150 ms
Jitter < 5 ms > 15 msService Level Test Packet Loss < 0.5% > 2%
R-Value > 80 < 70
MOS > 4 < 3
MER 30dB(64), 33dB (256) 25dB(64), 28dB(256)
RF PRE-FEC BER 1.00E-09 1.00E-07At Home Rx - Level -5~+5 dBmV <-10dBmV or >+10dBmV
Tx - Level 35 ~45 dBmV < 30dBmV or >50dBmVMER 32dB(64), 35dB (256) 28 dB(64), 31dB(256)
RF PRE-FEC BER 1.00E-09 1.00E-07At Node Freq Response < 4dB > 5dB
Upstream SNR >35dB <25dB
CMTS CMTS Loading <50% >80%
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION60
Sweep Verifies Construction Quality
• Sweep can find craftsmanship or component problems
that aren’t revealed with other tests
• Damaged cable
• Poor connectorization
• Amplifier RF response throughout its frequency range
• Gain
• Slope
• Loose seizure screws, module hardware…….
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION61
System’s ability properly to transmit signals from headend to subscriber throughout the designed frequency range
“Sweep” tests verify performance to design specifications Expected Results: N/2 + X = max flatness variation
• where n = number of amplifiers in cascade• where x = best case flatness figure
Typical Flattness formulas are: n/10+1 old systems with 30 amp cascade 400 MHz Bandwidth N/2+2 new systems with and 5 to 7 amp cascade 750 MHz
Bandwidth
Frequency Response Definition
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION62
Test Probes
Will always be bi-directional unless they are in series with the circuit
Higher loss probes provide less of an impedance mismatch, but lower levels
F-to-Housing adapters cause severe standing waves because of;– Bad grounding
– RF power splitting
– Impedance mismatch
Be careful with in-line pads while probing seizure screws– Not usually dc blocked
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION63
Sweep Response of a Splitter
RFIN
RF OUT
INPUT
OUTPUT
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION64
100 ft of RG-59 cable
RFIN
RF OUT
INPUT
OUTPUT
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION65
Sweep Response of 17dB Tap
Tap Port
Tap RF
Out
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION66
Sweep Response of a Amplifier
Amplifier Forward
20dB
Amplifier Return
12dB
RF in
RF in RF out
RF out
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION67
A Sweep Finds Problems That Signal Level Measurements Miss
Standing Waves
Roll off at band edges
Misalignment
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION68
Balancing AmplifiersBalancing amplifiers using tilt
No TerminationLose Face Plate, or crack cable
shield
Node Reference Signal Sweep response with a Resonant FrequencyAbsorption
Sweep response with standing waves
Headend
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION69
Step 1) Forward & Reverse SweepWHY SWEEP?
Headend
No TerminationLose Face Plate, or crack cable
shield
Node Reference Signal Sweep response with a Resonant FrequencyAbsorption
Sweep response with standing waves
D = 492*Vp/F
F
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION70
Types of Sweep
Sweepless Sweep Forward Sweep Return Sweep
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION71
“Sweepless” Sweep Method
Developed by Wavetek in the late 1980s Compares headend levels to system test point
levels Totally non-interfering (no sweep injection signal) Relatively inexpensive (no headend unit) Normal level variations in headed signals cause
loss of valid reference information Blank spectrum not tested
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION72
‘Sweepless’ Sweep
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION73
Sweepless Sweep with Channel drop out
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION74
Sweep with Transmitter
Sweep transmitter and headend monitor Constantly monitors video, audio, and digital carriers plus
sweep insertion points Transmits any level variations to the SDA-5500 or DSAM
6000 on a telemetry carrier to update the reference– Keeps receiver up to date on headend levels
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION75
Typical Forward Sweep Response
Fiber Node Line ExtenderEnd of Line Tap
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION76
Bench Sweep Amplifiers
Verify old modules
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION77
Beware of Taps
Port 1 thru 8 not terminated Port 1 thru 8 terminated
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION78
System Problems
55.25 MHz 745.25 MHz
Low end roll off High end roll off
Resonant Frequencyabsorption
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION79
3 dB /100 MHz /
Signature
System Problem
System Problem vs. Signature
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION80
Headend to Tap
Typical system not swept or balanced for 6 months
HH
LL
SDA-5500 - Headend unit
FREQFREQ
CHANCHAN
ENTERENTER
FCNFCNCLEARCLEAR
helphelp
statusstatus
alphaalpha
lightlight
abcabc defdef ghighi
jkljkl mnomno pqrpqr
stustu vwxvwx yzyz
spacespace +/-+/-
11 22 33
44 55 66
77 88 99
00
xx
..
FILEFILE
AUTOAUTO
SETUPSETUP
TILTTILT SCANSCANLEVELLEVEL
C/NC/N HUMHUM MODMOD
SWEEPSWEEP
SPECTSPECT
PRINTPRINT
System Sweep Transmitter 3SRSystem Sweep Transmitter 3SRSystem Sweep Transmitter 3SRSystem Sweep Transmitter 3SRStealth SweepStealth SweepStealth SweepStealth Sweep
Ampifiers not balanced
Cracked Hardline
FCC Proof Failure
Customer Complaints
Noisy pictures!
HD Tiling
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION81
Headend to Tap
Typical system after Sweep and Balance
HH
LL
SDA-5500 - Headend unit
FREQFREQ
CHANCHAN
ENTERENTER
FCNFCNCLEARCLEAR
helphelp
statusstatus
alphaalpha
lightlight
abcabc defdef ghighi
jkljkl mnomno pqrpqr
stustu vwxvwx yzyz
spacespace +/-+/-
11 22 33
44 55 66
77 88 99
00
xx
..
FILEFILE
AUTOAUTO
SETUPSETUP
TILTTILT SCANSCANLEVELLEVEL
C/NC/N HUMHUM MODMOD
SWEEPSWEEP
SPECTSPECT
PRINTPRINT
System Sweep Transmitter 3SRSystem Sweep Transmitter 3SRSystem Sweep Transmitter 3SRSystem Sweep Transmitter 3SRStealth SweepStealth SweepStealth SweepStealth Sweep
Ampifiers balanced
Hardline good Condition
FCC Proof PASS!
Customers Satisfied!
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION83
Analog Integrity is Still Paramount, Supplemented by Digital Measurements
Majority of “digital” issues involve basic analog maintenance of the RF plant– Levels, including network tilt, must be optimized– RF distortions such as CSO and CTB can affect QAM carriers– Managing hum has been shown to improve QAM carrier quality– Carrier-to-noise and signal-to-noise (MER on QAM channels)– BER and DQI for intermittent impairments– Ingress management
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION84
Goal
The objective in reverse path alignment is to maintain unity gain with constant inputs and minimize noise and ingress.
Set all optical receivers in the headend to same output level and ideally the same noise floor to optimize C/N ratio.– The reverse path noise is the summation of all noise
from all the amplifiers in the reverse path.
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION85
Sweep Reference Considerations
Typically the node is used for the reference Use test probe designed for node/amp It’s a good engineering practice to store a new
reference each day Establish reference points to simplify ongoing
maintenance (sweep file overlay) Need to know amps hidden losses in return
path (Block diagrams / Schematics) Need to know where to inject sweep pulses and
the recommended injection levels
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION86
Optimizing the Node
Activation and maintenanceof the trunk network bySDA-5000 + SDA-OPT1 or SDA-4040D
Activation and maintenanceof optical nodes byDSAM 6000 with Reverse Sweep
Reverse-pathoptical receivers
HH
LL
ForwardLaser
Headend
SDA-5500 - Headend unit
FREQFREQ
CHANCHAN
ENTERENTER
FCNFCNCLEARCLEAR
helphelp
statusstatus
alphaalpha
lightlight
abcabc defdef ghighi
jkljkl mnomno pqrpqr
stustu vwxvwx yzyz
spacespace +/-+/-
11 22 33
44 55 66
77 88 99
00
xx
..
FILEFILE
AUTOAUTO
SETUPSETUP
TILTTILT SCANSCANLEVELLEVEL
C/NC/N HUMHUM MODMOD
SWEEPSWEEP
SPECTSPECT
PRINTPRINT
System Sweep Transmitter 3SRSystem Sweep Transmitter 3SRSystem Sweep Transmitter 3SRSystem Sweep Transmitter 3SRStealth SweepStealth SweepStealth SweepStealth Sweep
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION87
Rev
erse
Co
mb
iner
X dBmV
FREQ
CHAN
ENTER
FCNCLEAR
help
status
alpha
light
abc def ghi
jkl mno pqr
stu vwx yz
space +/-
1 2 3
4 5 6
7 8 9
0x
.
FILE
AUTO
SETUP
TILT SCANLEVEL
C/N HUM MOD
SWEEP
SPECT
System Sweep Transmitter 3SRSystem Sweep Transmitter 3SR Stealth SweepStealth Sweep
Pad input of the SDA-5510 for 0 dBmV
NODE
NODE
NODE
NODE
Optical Receiver
Optical Receiver
Optical Receiver
Optical Receiver
All Return Path RF signal levels must be set to same output “X” level at the optical receiver in the headend or hubsite with the same “X” level input at the node.
X dBmV
Return Path “X” LEVEL
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION88
Rev
erse
Co
mb
iner
X dBmV
FREQ
CHAN
ENTER
FCNCLEAR
help
status
alpha
light
abc def ghi
jkl mno pqr
stu vwx yz
space +/-
1 2 3
4 5 6
7 8 9
0x
.
FILE
AUTO
SETUP
TILT SCANLEVEL
C/N HUM MOD
SWEEP
SPECT
System Sweep Transmitter 3SRSystem Sweep Transmitter 3SR Stealth SweepStealth Sweep
Pad input of the SDA-5510 for 0 dBmV
NODE
NODE
NODE
NODE
Optical Receiver
Optical Receiver
Optical Receiver
Optical Receiver
All Return Path RF signal levels must be set to same output “X” level at the optical receiver in the headend or hubsite with the same “X” level input at the node.
X dBmV
X dBmVX dBmV
Return Path “X” LEVEL
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION89
Rev
erse
Co
mb
iner
X dBmV
FREQ
CHAN
ENTER
FCNCLEAR
help
status
alpha
light
abc def ghi
jkl mno pqr
stu vwx yz
space +/-
1 2 3
4 5 6
7 8 9
0x
.
FILE
AUTO
SETUP
TILT SCANLEVEL
C/N HUM MOD
SWEEP
SPECT
System Sweep Transmitter 3SRSystem Sweep Transmitter 3SR Stealth SweepStealth Sweep
Pad input of the SDA-5510 for 0 dBmV
NODE
NODE
NODE
NODE
Optical Receiver
Optical Receiver
Optical Receiver
Optical Receiver
X dBmV
X dBmV
All Return Path RF signal levels must be set to same output “X” level at the optical receiver in the headend or hubsite with the same “X” level input at the node.
X dBmV
X dBmV
X dBmV
Return Path “X” LEVEL
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION90
Return Path “X” LEVEL
All Return Path RF signal levels must be set to same output “X” level at the optical receiver in the headend or hubsite with the same “X” level input at the node.
Rev
erse
Co
mb
iner
X dBmVX dBmV
FREQ
CHAN
ENTER
FCNCLEAR
help
status
alpha
light
abc def ghi
jkl mno pqr
stu vwx yz
space +/-
1 2 3
4 5 6
7 8 9
0x
.
FILE
AUTO
SETUP
TILT SCANLEVEL
C/N HUM MOD
SWEEP
SPECT
System Sweep Transmitter 3SRSystem Sweep Transmitter 3SR Stealth SweepStealth Sweep
Pad input of the SDA-5510 for 0 dBmV
NODE
NODE
NODE
NODE
Optical Receiver
Optical Receiver
Optical Receiver
Optical Receiver
X dBmV
X dBmV
X dBmV
X dBmV
X dBmV
X dBmV
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION91
Reverse Noise Floor
All Return noise floor levels should be maintained to supply approximately “X level minus 40 dB” going into the node.
Rev
erse
Co
mb
iner
X - 40 dBX - 40 dB
FREQ
CHAN
ENTER
FCNCLEAR
help
status
alpha
light
abc def ghi
jkl mno pqr
stu vwx yz
space +/-
1 2 3
4 5 6
7 8 9
0x
.
FILE
AUTO
SETUP
TILT SCANLEVEL
C/N HUM MOD
SWEEP
SPECT
System Sweep Transmitter 3SRSystem Sweep Transmitter 3SR Stealth SweepStealth Sweep
Return Telemetry must have at least a 20 dB SNR
NODE
NODE
NODE
NODE
Optical Receiver
Optical Receiver
Optical Receiver
Optical Receiver
X - 40 dB
X - 40 dB
X - 40 dB
X - 40 dB
X - 40 dB
X - 40 dB
Desired noise floors into node
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION92
Choose operating levels that maximize the distortion performance of your return path
Get all the information that you can on your nodes and amps from your manufacturer
Create a sweep procedure for your system– make up a chart showing injection levels at each
test point
ALIGNING THE RETURN PATH
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION93
ALIGNING THE RETURN PATH
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION94
Test Point Compensation
Graphical user interface
Store & recall of test point setups
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION95
Test Point Compensation
Graphical user interface
Store & recall of test point setups
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION96
User Interface: Forward Sweep
Raw Forward Sweep
Reference the Sweep Trace
Save the Reference name
Referenced Sweep Trace
Save the File for Records
Choose & Save the File name
Troubleshoot or Move to next device in the line
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION97
User Interface: Reverse Sweep
Raw Reverse Sweep
Reference the Sweep Trace
Save the Reference name
Referenced Reverse Sweep
Save the File for Records
Choose & Save the File name
Troubleshoot or Move to next device in the line
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION98
User Interface: Test Point Compensation
Test Point Comp menu can be accessed two ways:•Settings Hotkey in Sweep Measurement•Shift+4 on the keypad at any time
List of current TPC Files
Create a new TPC file
Name and save the TP device
Edit new TPC file
Specify TP device loses
Pick Reverse Tel & Insertion levels
Forward summary specs
Reverse Summary Specs
TPC now active on all tests
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION99
User Interface: Markers and Zooming
Go to View Menu
Move Markersto desired locations
Go to Zoom
New Frequency Range
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION100
User Interface: Sweep Settings
SelectSettings Tab
Sweep Settings
Turning on Tilt Compensation activates the Tilt settings
For bidirectional test points set the Reverse Sweep Port to Port 1For directional test points set it to Port 2 and attach the reverse test point to port 2 and the forward test point to port 1
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION101
User Interface: Telemetry Settings
SelectSettings Tab
Telemetry Frequency
If using an SDA-5500 headend unit only set the reverse Sweep to Single UserIf also using a SDA-5510 select Multi User for reverse Sweep
Set the telemetry of the SDA-5500 headend unit and SDA-5510 (if available)
PathTrak’sField ViewTelemetry
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION102
Sweeping Out
Connect to Input Test Point on Node
NODE
X dBmV
Telemetry = X dBmV
The sweep and alignment procedure for both the forward and return path starts at the node and then moves toward the end of line
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION103
Sweeping Out
X dBmV
Maintain unity gain with constant inputSet TP Loss as required
NODE
X dBmV
Telemetry = X dBmV
Connect to Input of First Reverse Amp
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION104
X dBmV
Maintain unity gain with constant inputSet TP Loss as required
X dBmV
NODE
Sweeping Out
X dBmV
Telemetry = X dBmV
Connect to Input of First Reverse Amp
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION105
X dBmV
Maintain unity gain with constant inputSet TP Loss as required
X dBmV
X dBmV
NODE
Sweeping Out
X dBmV
Telemetry = X dBmV
Connect to Input of First Reverse Amp
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION106
X dBmV
Maintain unity gain with constant inputSet TP Loss as required
X dBmV
X dBmV
X dBmV
NODE
Sweeping Out
X dBmV
Telemetry = X dBmV
Connect to Input of First Reverse Amp
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION107
X dBmV
Maintain unity gain with constant inputSet TP Loss as required
X dBmV
X dBmV
X dBmV X dBmV
NODE
Sweeping Out
X dBmV
Telemetry = X dBmV
Connect to Input of First Reverse Amp
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION108
Damaged or missing end-of-line terminators
Damaged or missing chassis terminators on directional coupler, splitter or multiple-output amplifier unused ports
Loose center conductor seizure screws
Unused tap ports not terminated. This is especially critical on lower value taps
Unused drop passive ports not terminated
Use of so-called self-terminating taps (4 dB two port; 8 dB four port and 10/11 dB eight port) at feeder ends-of-line. Such taps are splitters, and do not terminate the line unless all F ports are properly terminated
Common problems typically identified in outside plant
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION109
Kinked or damaged cable (including cracked cable, which causes a reflection and ingress).
Defective or damaged actives or passives (water-damaged, water-filled, cold solder joint, corrosion, loose circuit-board screws, etc.).
Cable-ready TVs and VCRs connected directly to the drop. (Return loss on most cable-ready devices is poor.)
Some traps and filters have been found to have poor return loss in the upstream, especially those used for data-only service.
Common problems typically identified in outside plant
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION110
Intermittent Connections
Poor craftsmanship on connectors
Loose center seizure screws & fiber connectors
Radial cracks in hard-line coaxial cable
Cold solder joints
Bad accessories
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION111
The Situation
Can’t justify taking the system down to troubleshoot Unacceptable to the subscribers who will;
– Lose communication
– Get a slower throughput
– Have periodic “clicking” in their telephone calls
To be non-intrusive we must;
– Understand test points
– Apply new procedures and applications
– Learn new troubleshooting techniques
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION112
Typical Problem Areas
Taps– Most ingress comes from houses with tap values of
17 dB or less
House Wiring– Drop Cable & F Connectors are approximately ~95%
of Problem
Amplifiers, hard line cable and the rest of the system are a small percentage of the problem if a proper leakage maintenance program is performed.
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION113
8 Port23 dB
tapThis would be a DC-12
The splitter network = ~11 dB of loss
Taps
Taps are a combination of a DC and a splitter network
Taps give an actual representation of what the subscriber is seeing and transmitting in to
Points to remember;– Lower valued taps equal more
through loss
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION114
Input Output
Testing at the Seizure Screws
If the problem is at the Forward Output, continue on
If the problem is at the Forward Input and not the Forward Output, then the problem is from one of the drops
Spring loaded seizure screw probes create a good ground and quick connect without causing outages
Forward Path
Return Path
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION115
Input Output
Testing at the Seizure Screws
Use a 20 db pad with AC block when using spring loaded seizure screw probes
Forward Path
Return Path
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION116
4 Port Tap
Probe the seizure screw for ingress
Taps are made up of a Directional Coupler and Splitters
Disconnect one drop at a time to determine the point of entry
-60
-50
-40
-30
-20
-10
0
10
20
30
40
Center: 25.000 MHzSpan: 40.000 MHzRBW: 300 KHz VBW: 100 KHz Dwell: 400 µS
In-Band Power 10.393 dBmV
-60
-50
-40
-30
-20
-10
0
10
20
30
40
Center: 25.000 MHzSpan: 40.000 MHzRBW: 300 KHz VBW: 100 KHz Dwell: 400 µS
In-Band Power 8.632 dBmV
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION117
Return Path
Taps - Probe the Seizure Screws for Ingress & CPD
If the problem is at the FWD Input and not the FWD Output, then the problem is likely from one of the dropsIf the problem is at
the FWD Output of tap, continue on towards end of line Forward Path
Disconnect one drop at a time to determine the point of entry
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION118
Electrical Impulse Noise from One House
-60
-50
-40
-30
-20
-10
0
10
20
30
40
Center: 25.000 MHzSpan: 40.000 MHzRBW: 300 KHz VBW: 100 KHz Dwell: 400 µS
In-Band Power 10.393 dBmV
-60
-50
-40
-30
-20
-10
0
10
20
30
40
Center: 25.000 MHzSpan: 40.000 MHzRBW: 300 KHz VBW: 100 KHz Dwell: 400 µS
In-Band Power 8.632 dBmV
•Reverse Spectrum shot at customer's drop
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION119
PathTrak Field View option combined with JDSU meters provides a complete “Find & Fix” field troubleshooting solution
• PathTrak Field View option on SDA and DSAM platform enables techs to greatly reduce MTTR (Mean Time to Repair), which increases customer satisfaction and loyalty
• PathTrak Field View option for DSAM provides a programmable CW carrier to aid in troubleshooting return problems
• Both SDA and DSAM have low pass filter for troubleshooting bi-directional test points
PathTrak™ Field View Option
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION120
NODE
Tracking Down Ingress and CPD
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION121
RBWSettings
Live Spectrum Analysis – RBW Setting
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION122
300kHz RBW
(Resolution Bandwidth setting)
+19.61 dBmV
Live Spectrum Analysis – RBW Setting
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION123
1,000kHz RBW
(Resolution Bandwidth setting)
+25.95 dBmV
Live Spectrum Analysis – RBW Setting
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION124
Live Spectrum Analysis – RBW Setting
30kHz RBW
(Resolution Bandwidth setting)
+11.31 dBmV
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION125
Quick and Easy Spectrum Scan
View from 4 to 110 MHz spectrum with programmable pass/fail limits
Spectrum view with adjustable marker and zoom function
Selectable peak hold Store in work folder Standard feature on DSAM
Platform
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION126
FM Band IngressFM Band Ingress
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION127
eMTA-CABLE MODEM
7 dB TAP
Drop Cable
High Pass Filter
GROUND BLOCK
3-WaySplitter
DIGITAL SET-TOP
House
2-Way Amplifier
Testing the RF Network
VoIP
OLDER TV SET
Return Equalizer
ONLINE GAMING
WIRELESS LAPTOP
COMPUTOR
ETHERNET
Disconnect drop from tap and check for ingress
coming from customer’s home wiring
INGRESS SPECTRUM MEASUREMENTS
If ingress is detected, terminate other end of
drop and scan spectrum again for ingress
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION128
Troubleshooting is “Back to the Basics”
Majority of problems are basic physical layer issues Most of the tests remain the same Check power Check forward levels, analog and digital Check forward / reverse ingress Do a visual check of connectors / passives Replace questionable connectors / passives Tighten F-connectors per your company’s installation
policy– Be very careful not to over tighten connectors on CPE (TVs,
VCRs, converters etc.) and crack or damage input RFI integrity
Line Conditioning and Return Path Equalization
Why should you worry about return attenuation?
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION130
Level Control Scheme
Reversereceiver Node
Subscriberterminal
RF distribution
Servicesplitter
Nodecombiner
Digital servicereceiver &
demod.
Optical link
level control
Leve
l
Frequency
Leve
l
Frequency
Target levelinto laser
Target levelinto receiver
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION131
Optimizing (Conditioning) the Reverse Path
Adding reverse path attenuation -– enables flexible, more cost efficient design– increases C/N performance of communicating devices– reduces dynamic range of communication devices– reduces opportunities for reverse laser clipping– affords a ‘more forgiving’ network set-up during reverse
balance and alignment
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION132
Step Attenuators
Low value taps produce the majority of ingress and trouble calls within a typical HFC network. This is due to the lack of sufficient reverse attenuation found in higher-value taps. Applied directly to the tap port, Step Attenuators provide unity gain with all cable modems and other critical reverse transmission products like digital voice and high-speed Internet.
40 MHz
54 MHz
5 MHz
-12 dB
-1.3 dB
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION133
Reverse ‘Window’
Problem: Reverse window can exceed dynamic range of terminals
23 20 17 11 8
Forward levels:45/35 dBmV
Terminal
NID
Terminal
NID
Required reverse input level:22 dBmV
55 dBmV 41 dBmV
Terminal reverse 'window':55 - 41 = 14 dB
-10 dB -3 dB
In red: required tap port reverse level45.0 38.0
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION134
Reduced Reverse ‘Window’
Same area, ‘NID’ design standardized – reverse terminal ‘window’ improved by 7 dB
23 20 17 11 8
Forward levels:45/35 dBmV
Terminal
NID
Terminal
NID
Required reverse input level:22 dBmV
55 dBmV 48 dBmV
55 - 48 = 7 dB
-10 dB -10 dB
In red: required tap port reverse level45.0 38.0
Terminal reverse 'window'
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION135
Reverse Tap Port ‘Window’- High Forward Levels, LEQ w/o RC -
Reverse ‘Window’ of required tap port levels: 44.9 - 31.2 = 13.7 dB
29 26 23 20
Forward levels:51/41 dBmV
17
14 8
11 8132' 110' 110' 120' 110' 110'
132' 120'
Required Reverse Level @ Amplifier Input Port: 15 dBmV
44.0 43.2 41.0 39.1 35.2 31.2
43.3 39.4
44.9
In red: required tap port reverse level
DC-12
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION136
Reverse Tap Port ‘Window’- High Forward Levels, Using LEQ/RC -
Reverse ‘Window’ narrowed from 13.7 to: 44.9 - 39.1 = 5.8 dB
29 26 23 20
Forward levels:51/41 dBmV
17
14 8
11 8132' 110' 110' 120' 110' 110'
132' 120'
Required Reverse Level @Amplifier Input Port: 15 dBmV
44.0 43.2 41.0 39.1 44.2 40.2
43.3 39.4
44.99 dB reversepad installed
In blue: previous reverse level required
35.2 31.2
DC-12
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION137
Reverse Tap Port ‘Window’- Low Density, LEQ w/o RC -
Reverse ‘Window”range of required tap port levels: 44.0 - 25.5 = 18.5 dB
29
Forward levels:51/41 dBmV
1,560'
Required reverselevel: 15 dBmV
44.0 25.5
4
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION138
Reverse Tap Port ‘Window’- Low Density, Using LEQ/RC -
Reverse ‘Window’ narrowed from 18.5 to: 44.0 - 40.5 = 4.5 dB
29
Forward levels:51/41 dBmV
1,560'
Required reverselevel: 15 dBmV
44.0 40.5
4
In blue: previous reverse level required
25.5
15 dB reversepad installed
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION139
Noise Floor Levels
Be careful with spectrum analyzer level readings
The level is based off the RBW setting and will be very different from one setting to another
A -20 dBmV noise floor with 30 kHz RBW is really 1.2 dBmV in a 4 MHz bandwidth
That’s why measurements with no point of reference are worthless
At least if there’s a reference carrier present, you can make a relative measurement
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION140
Severe Transient Hum Modulation
The RF choke can saturate with too much current draw and cause the ferrite material to break down
Same thing can happen in customer installed passives
Notice that this looks a lot like CPD
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION141
Correct pin length,Properly tightened
Pin length too short
Center Pin/Seizure Screws
Typical connector problems These may result in suckouts or roll off
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION142
Pin length too long
Overtightened seizure screwDamaged pin
Center Pin/Seizure Screws
This may also hamper the “seating” of the RF module
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION143
Pin tightened before turningconnector into housing
May result in a broken or twisted pin inside the connector
Center Pin/Seizure Screws
• A more typical result is the pin gets pushed back into the connector instead of pushing past the seizure screw
• Happens a lot to housing terminators
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION144
AfterBefore
Loose Fiber Connector
SC connector not pushed in all the way
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION145
Fiber Connectors Are Everywhere
Fiber optic connectors are common throughout the network, and they give you the power to add, drop, move and change the network.
Buildings
Multi-home UnitsResidential
Head End
Local Convergence Point
Network Access Points
Feeder Cables
Distribution Cables
Coaxial Network
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION146
Types of Contamination
A fiber end face should be free of any contamination or defects, as shown below:
Common types of contamination and defects include the following:
Dirt Oil Pits & Chips Scratches
SINGLEMODE FIBER
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION147
Where is it? – Everywhere
Airborne, hands, clothing, bulkhead adapter, dust caps, test equipment, etc.
The average dust particle is 2–5µ, which is not visible to the human eye.
A single spec of dust can be a major problem when embedded on or near the fiber core.
Even a brand new connector can be dirty. Dust caps protect the fiber end face, but can also be a source of contamination.
Fiber inspection microscopes give you a clear picture of the problems you are facing.
Your biggest problem is right in front of you… you just can’t see it!
DIRT IS EVERYWHERE!
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION148
Where is it? – Proliferation of Dirt
There are a number of different sources where dirt and other particles
can contaminate the fiber.
Test Equipment
Dust Caps
Bulkheads
People
Environment
Connectors and ports on test equipment are mated frequently and are highly likely to become contaminated. Once contaminated, this equipment will often cross-contaminate the network connectors and ports being tested.
Inspecting and cleaning test ports and leads before testing network connectors prevents cross-contamination.
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Conclusion
If we want our telecommunications networks to be as reliable/available as the telephony business at 99.98%, we must;– Stay up with technology– Have contingency plans for everything– Train our employees– Utilize equipment that will quickly characterize and separate real
problems from insignificant events– Be Proactive instead of Reactive!
© 2005 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION150
Thank You !Mark Ortel
Sales Support Engineer
Cable Networks Divisionwww.jdsu.com
SCTE Chapter