Presentation on theme: "Plant Reliability Larry Jump JDSU Field Applications Engineer"— Presentation transcript:
1 Plant Reliability Larry Jump JDSU Field Applications Engineer TAC Opt. 3 / 2
2 Agenda 3 major areas of concern CoaxFiberInside plant
3 To provide better service to our customers in light of competition PurposeTo provide better service to our customers in light of competitionMaintain plant instead of reacting to problemsBe alerted to issues before the customer noticesMaintain reliability for essential servicesTo increase revenues
7 Sweep vs. Signal Level Meter Measurements References: Sweep systems allow a reference to be stored eliminating the effect of headend level error or headend level drift.Sweep Segments: Referenced sweep makes it possible to divide the HFC plant into network sections and test its performance against individual specifications.Non-Invasive: Sweep systems can measure in unused frequencies. This is most important during construction and system overbuilding.BEST Solution to align: Sweep systems are more accurate, faster and easier to interpret than measuring individual carriers.56
8 Frequency Response Definition System’s ability properly to transmit signals from headend to subscriber and back throughout the designed frequency rangeExpected Results (Traditionally): n/10 + x = max flatness variationwhere n = number of amplifiers in cascadewhere x = best case flatness figure (supplied by manufacturer)Expected Results in current HFC Networks: Typically < 3 to 4 dB max flatness variation anywhere in the network (check with your Manager for max flatness variation limits)55
9 Forward Path Considerations Diverging SystemConstant OutputsChannel Plan to Match Fixed Signalsvideo / audio / digital carriersSweep Telemetry Carriers, 1MHz wideSystem Noiseis the sum of cascaded amplifiersBalance or Align (Sweep)compensate for losses before the amp66
10 Sweep Reference Considerations Typically the node is used for the referenceUse test probe designed for node/ampIt’s a good engineering practice to store a new reference each dayEstablish 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 levelsOnce the transmitter is configured properly, the next step is to store a reference in the receiver to enable accurate normalized tests at each amplifier output test point. This reference is usually stored at the node. The response at subsequent amplifiers is compared with this reference to verify operation according to the unity gain principle (theoretically every amplifier will have the same output levels and response).16
11 Unity Gain in the forward path LRREach amplifier compensates for theloss in the cable and passives beforethe amplifier under test. The system isaligned so that the levels at each greenarrow are exactly the same.In the forward path, signals originate at the headend and are transmitted to many customer drops. One output feeds many inputs.In the forward system the outputs of like devices are typically set to same output level. Each amplifier compensates for the cable and passive loss before it. This principal (Gain = Loss) is Unity Gain.Level changes in the forward path occur due to changes in cable loss caused by temperature. Automatic level or gain controls (ALC or AGC) are located in the amplifiers to compensate for these changes in level. A section of the alignment procedure for the forward path involves setting the operating point for the automatic control circuit.In short all amplifiers have a constant output to compensate for the losses in the cable and any passives before the amplifier.
12 Why do we need Unity Gain? 32/2631/2530/2429/2322222222232323If unity gain is not observed then the signal impairments quickly overtake the desired signals.In the case shown above, we experience a 3 dB degradation in CNR with just 3 amps in cascade. In today’s systems, 3 dB would easily make or break us.If the signals were 1 db high at each amp, then CSO would be worse by 6 dB and CTB would be worse by 3 dB.It is very important to maintain constant levels!If Unity Gain is not observed distortions and or noise build up quickly!
14 A Sweep Finds Problems That Signal Level Measurements Miss MisalignmentStanding WavesRoll off at band edges666
15 Sweeping Reverse Path Goals 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.Adjust sweep response to match 0dB flat line Sweep reference and 0dBmV Telemetry level111212
16 Before reverse sweeping begins…. Optimize the upstream nodeSplitting, combining and padding considerations in the headend.
17 Return OpticsWe discuss this first because it has the greater impact on the MER at the CMTS input because it has the lowest dynamic rangeOptimized by measuring NPR at the input to the CMTS by injecting different total power at the input to laser.Carriers should be derated according to bandwidth using power per hertz.Not part of the unity gain portion of the HFC plant.Set up is laser and node specificThe input to the laser and the OMI setting are normally taken care of at the factory
18 NPR MeasurementMeasured by injecting a wideband noise source with a notch filter at the input. Then measuring essentially the noise to the notch at the output.Measured as 10 log Power/hz of the signal/Power/hz of the notch noiseThe lower the signal the lower the CNR, the higher the signal, the more distortion.Input starts low and then raised in 1 dB steps
19 Power per Hertz Calculation dBmV/Hz = Total Power – 10 Log (BW)dBmV/HZ = 45 – 10 Log (37,000,000)dBmV/ Hz = 45 – 10 (7.57)dBmV/ Hz = 45 – 75.7dBmV/ Hz = -29.3Total Power Input for 6.4 MHz 64 QAMdBmV = Log (BW)dBmV = Log (6,400,000)dBmV = (6.8)dBmV =dBmV = 38.7
20 REVERSE LEVEL20 dBmVOpticalReceiverNODE20 dBmVOpticalReceiverNODECombinerReverseOpticalReceiverNODEOpticalReceiverNODEPad for0 dBmVAll signal levels must be set to same output level at the optical receiver in the headend or hubsite with the same input at the node.FREQCHANENTERFCNCLEARhelpstatusalphalightabcdefghijklmnopqrstuvwxyzspace+/-123456789x.FILEAUTOSETUPTILTSCANLEVELC/NHUMMODSWEEPSPECTPRINTSystem Sweep Transmitter 3SRStealth Sweep131414
21 REVERSE LEVEL20 dBmVOpticalReceiverNODE20 dBmVOpticalReceiverNODE20 dBmVCombinerReverseOpticalReceiverNODEOpticalReceiverNODEPad for0 dBmVAll signal levels must be set to same output level at the optical receiver in the headend or hubsite with the same input at the node.FREQCHANENTERFCNCLEARhelpstatusalphalightabcdefghijklmnopqrstuvwxyzspace+/-123456789x.FILEAUTOSETUPTILTSCANLEVELC/NHUMMODSWEEPSPECTPRINTSystem Sweep Transmitter 3SRStealth Sweep131414
22 REVERSE LEVEL20 dBmVOpticalReceiverNODE20 dBmVOpticalReceiverNODE20 dBmVCombinerReverseOpticalReceiverNODE20 dBmVOpticalReceiverNODEPad for0 dBmVAll signal levels must be set to same output level at the optical receiver in the headend or hubsite with the same input at the node.FREQCHANENTERFCNCLEARhelpstatusalphalightabcdefghijklmnopqrstuvwxyzspace+/-123456789x.FILEAUTOSETUPTILTSCANLEVELC/NHUMMODSWEEPSPECTPRINTSystem Sweep Transmitter 3SRStealth Sweep131414
23 REVERSE LEVEL20 dBmVOpticalReceiverNODE20 dBmVOpticalReceiverNODE20 dBmVCombinerReverseOpticalReceiverNODE20 dBmVOpticalReceiverNODE20 dBmVPad for0 dBmVAll signal levels must be set to same output level at the optical receiver in the headend or hubsite with the same input at the node.FREQCHANENTERFCNCLEARhelpstatusalphalightabcdefghijklmnopqrstuvwxyzspace+/-123456789x.FILEAUTOSETUPTILTSCANLEVELC/NHUMMODSWEEPSPECTPRINTSystem Sweep Transmitter 3SRStealth Sweep131414
24 REVERSE NOISENoise -35 dBmVOpticalReceiverNODENoise -35 dBmVOpticalReceiverNODECombinerReverseNoise -35 dBmVOpticalReceiverNODENoise -35 dBmVOpticalReceiverNODEIf your headend has multiple reverse trunks you will need to patch in the appropriate trunk to be swept. It’s a good idea to set up a patch panel to quickly move the reverse sweep to different trunks.Ideally all combined nodes should have same noise floor to maximize C/N ratio.FREQCHANENTERFCNCLEARhelpstatusalphalightabcdefghijklmnopqrstuvwxyzspace+/-123456789x.FILEAUTOSETUPTILTSCANLEVELC/NHUMMODSWEEPSPECTPRINTSystem Sweep Transmitter 3SRStealth Sweep121313
25 Headend combining and splitting Other Return ServicesCMTSPathTrakThe headend lash up should be carefully planned. Notice that even though there are only 4 return services that 8 way splitters are used with open ports terminated. This allows for future expansion and a test point without having re-engineer the entire return path.Notice the pad on the input to the CMTS port. This should be padded so that the input is the optimum 0 dBmv with the reference signal injected at the node. Again that forces the modems in the field to run at their highest levels to maximize C/I.Set top converterFREQCHANENTERFCNCLEARhelpstatusalphalightabcdefghijklmnopqrstuvwxyzspace+/-123456789x.FILEAUTOSETUPTILTSCANLEVELC/NHUMMODSWEEPSPECTPRINTSystem Sweep Transmitter 3SRStealth Sweep
26 Return Sweep considerations Instead of point to multipoint, the system is multipoint to pointUnity gain at the inputs to the amplifiersTelemetry carriers upstream and downstreamNoise and ingress are additive from the entire node. One bad drop can take down the entire node.Channel Plan to match bursty digital signals. No sweep points on upstream carriersReturn Sweep compensates for losses after the ampSet telemetry carrier level and sweep level to the same thing.
27 Advantages of return sweep over the older methods Not as labor intensive as the older methods.Align forward and reverse with the same stop at the amplifierNo cumbersome equipment in the field or the headendMinimum use of bandwidth for test equipmentControl over the measurementsWe are aligning the entire spectrum in both directions, not just 2 carriers!Using a return sweep system is the most efficient method for alignment and troubleshooting of the return path.
28 5 things you need to know to set up your return path correctly Know your equipmentBlock diagrams of amplifiers, nodes, receivers, etc.Test EquipmentDetermine reverse sweep input levelsDetermine reference pointsOptimize return lasers portion firstSweep coaxial portion of the plantHere are 5 steps you should consider before attempting to align your return path. Let’s discuss each one individually.
29 Typical Node RF Block Diagram STATIONFWDEQPADLOW PASSFILTERHLREVSwitchDiplexFilterPORT 4Port 4OutputTPREVSwitchDiplexFilterPORT 6Port 6OutputTPHLPORT 3Port 3Fwd SignalfromOpticalRcvr.HLREVSwitchDiplexFilterPORT 5Port 5OutputTPReturnSignal toOpticalTransmitterNotice the test points of this node. The test points on the outside of the diplexer are directional for the forward direction. If the return path is viewed from these ports, it will be at a greatly reduced amplitude.The test points inside the diplexer are also directional, but for the return path.The bottom 2 legs are combined in the return through a splitter, but since the test points are directional too, ingress from one leg would be greatly reduced if not eliminated if viewed on the the other return test point.How are your amplifiers and nodes configured?
30 Typical RF Bridging Amplifier Block Diagram (1) Test Points are Bi-DirectionalNotes: ALL test points can be -20 or -25dBALC PINDIODEATTENInterstageEQPre-AmplifierPlug-InPADHighPassFilterDiplexHLIGCMainReverseLow PassALC CircuitBridgerACPowerRF/ACRFAuxREVTRANSPONDERRF INTERFECEBRIDGERRF TESTREVERSESTATIONPORT 1PORT 5PORT 2PORT 3PORT 6BRIDGE(1)Notice her that the test points are bi-directional, that means that both the forward and return signals are present and that means a LPF is necessary. In this instance also notice that the only isolation between the test points is the plug-in splitter or DC. Ingress present on one leg this amplifier would probably be viewable from the other test point, but at a reduced level.FNBs:Forward PathInput: Port 1RF and AC separated.Port 1 Test Point (Bi-Directional)Diplex FilterStation Fwd EQ.Adjust for TiltStation Pad.Adjust levelPre amplifierHigh pass filterInter stage CompersatorInter stage EQPin Diode circuitMain AmplifierOn output to Port 4.
31 Know your test equipment Different test equipment operates differently.Size Matters!
32 How is a reference level determined? From trunk return52 dBmv max modem output23db tap2 dB drop loss7 dB directional couplerThe goal of reverse design is to keep the plant levels as high as possible to optimize C/I ratio. The levels are controlled by long loop AGC from the CMTS.The worst case will be from the high value taps because they have the most loss in the path from the house to the return active.The reference level inputs are calculated by finding the worst case signal loss from a transmitter in the home to the reverse input to a multi-port device. Modems put out 58 dBmv max.EXAMPLE:26 tap9 db for DC that feeds the modem2 db drop lossNote, we did not consider cable loss. At the sub frequencies, this is minimal.Does your system use this as the reference point?20dBmV at the reference pointHLHL23
34 Constant outputs in the return path? LRRReturn Equip.In the return path, signals originate at the customer drops and are transmitted back to the headend. In other words, many outputs feed one input. In this slide we can see that all amplifiers are receiving signals not only from one or more return amps, but from transmitters in the home as well.If all the return amplifiers are aligned to have constant outputs, the signal levels will vary widely by the time they get back to the headend. Of course this is unacceptable.Because of this, a different approach needs to be taken to the maintain the unity gain concept in the reverse path .If the return amplifiers were balanced withconstant outputs, the levels would vary widely by the time they got back to the headend. This is due to return amplifiers having several inputs.
35 How does reverse sweep work? The DSAM receives data from thetransmitter and displays sweepfrom the headend unit3.The field unit initiates the sweep through the return path at the reference level.1.HLRRReturn Equip.With this method the field unit injects a sweep signal into the return amplifier at the reference level. This sweep signal is essentially all frequencies in the return spectrum. The headend recognizes this sweep signal from the field unit, digitizes it’s own trace, and then sends it back out via the forward path to the field unit. The field unit detects the forward digital carrier from the headend unit and displays the results of the sweep trace at the headend.RF inFREQCHANENTERFCNCLEARhelpstatusalphalightabcdefghijklmnopqrstuvwxyzspace+/-123456789x.FILEAUTOSETUPTILTSCANLEVELC/NHUMMODSWEEPSPECTPRINTSystem Sweep Transmitter 3SRStealth SweepThe headend unit receives the sweep from the field unit, digitizes it’s own trace, and sends out on a forward telemetry pilot.2.RF out
36 Normalizing or Storing a Sweep Reference, reverse HLRRReturn Equip.With this method the field unit injects a sweep signal into the return amplifier at the reference level. This sweep signal is essentially all frequencies in the return spectrum. The headend recognizes this sweep signal from the field unit, digitizes it’s own trace, and then sends it back out via the forward path to the field unit. The field unit detects the forward digital carrier from the headend unit and displays the results of the sweep trace at the headend.RF inFREQCHANENTERFCNCLEARhelpstatusalphalightabcdefghijklmnopqrstuvwxyzspace+/-123456789x.FILEAUTOSETUPTILTSCANLEVELC/NHUMMODSWEEPSPECTPRINTSystem Sweep Transmitter 3SRStealth SweepInject correct input sweep levelCheck for adjust raw sweep levelStore reference fileRF out
37 Continuing On Inject correct input sweep level HLRRReturn Equip.With this method the field unit injects a sweep signal into the return amplifier at the reference level. This sweep signal is essentially all frequencies in the return spectrum. The headend recognizes this sweep signal from the field unit, digitizes it’s own trace, and then sends it back out via the forward path to the field unit. The field unit detects the forward digital carrier from the headend unit and displays the results of the sweep trace at the headend.RF inFREQCHANENTERFCNCLEARhelpstatusalphalightabcdefghijklmnopqrstuvwxyzspace+/-123456789x.FILEAUTOSETUPTILTSCANLEVELC/NHUMMODSWEEPSPECTPRINTSystem Sweep Transmitter 3SRStealth SweepInject correct input sweep levelUse the reverse sweep reference to compare and adjust amplifier output levelsRF out
38 Reverse Sweep Display Scale Factor Markers Start Frequency Stop FrequencyMarker FrequenciesMax Variation within Frequency RangeMarker Relative Levels
40 Loose Fiber Connector : A display an RF guy can understand SC connector not pushed in all the wayBeforeAfterThis slide was provided by Jim Kuhns and he made the following statement.An SC connector that had not been pushed all the way in. The first picture has a wavy motion that rolls from left to right on the analyzer screen.
41 Cross section of an Single Mode optical fiber Fiber Structure consists of a glass core, an outer protective glass cladding,and a buffer or coatingBufferCladdingCore2501259- What is fiber characterization? A series of tests to perform network base-lining on a fiber network. Fiber characterization mainly consists of the 5 following tests:- Optical Insertion Loss- Optical Return Loss- Optical Time Domain Reflectometry traces- Chromatic Dispersion testing- Polarized Mode Dispersion testingSideFront
42 RefractionRefraction is the bending of a ray of light at an interface.Cladding- What is fiber characterization? A series of tests to perform network base-lining on a fiber network. Fiber characterization mainly consists of the 5 following tests:- Optical Insertion Loss- Optical Return Loss- Optical Time Domain Reflectometry traces- Chromatic Dispersion testing- Polarized Mode Dispersion testingCore
43 IOR = Index of Refraction The Velocity of light in glass is different than the velocity of lightin a vacuum. This ratio is known as the Index of Refraction.n = c / vn = refractive indexc = velocity of light in a vacuumv = velocity of light in glassGlass- What is fiber characterization? A series of tests to perform network base-lining on a fiber network. Fiber characterization mainly consists of the 5 following tests:- Optical Insertion Loss- Optical Return Loss- Optical Time Domain Reflectometry traces- Chromatic Dispersion testing- Polarized Mode Dispersion testingVacuum
44 Reflection Reflection is the abrupt change in the direction of a light ray at an interface.Cladding- What is fiber characterization? A series of tests to perform network base-lining on a fiber network. Fiber characterization mainly consists of the 5 following tests:- Optical Insertion Loss- Optical Return Loss- Optical Time Domain Reflectometry traces- Chromatic Dispersion testing- Polarized Mode Dispersion testingCore
45 Light in an optical fiber – Total Internal Reflection If, for a moment, we could magnify a fiber and slow down the speed of light,we could visualize one pulse as it reflects off the core/cladding boundary.This is known as Total Internal ReflectionCore- If we magnify a fiber for a moment and slow down the speed of light,we can visualize one pulseof light as it reflects off the core/cladding boundary.This is referred to as “total internal reflection”Magnified 25400xTimed slowed to 1 nanosecondCladding
46 Bending Large noticeable bends and microscopic irregularities can both attribute to loss in a fiber.MacrobendingMicrobending
47 AttenuationAs the light signal travels down the fiber it decreases in power and is expressedin a rate of loss known as dB/kmCladdingCladding- What is fiber characterization? A series of tests to perform network base-lining on a fiber network. Fiber characterization mainly consists of the 5 following tests:- Optical Insertion Loss- Optical Return Loss- Optical Time Domain Reflectometry traces- Chromatic Dispersion testing- Polarized Mode Dispersion testingCoreCore100 km
48 Optical Return Loss = Optical Reflectance Loss Excessive Reflectance or high Optical Return Loss (ORL)can decrease the performance of a transmission system,eventually damage the transmitter and increase noise.CladdingCladding- What is fiber characterization? A series of tests to perform network base-lining on a fiber network. Fiber characterization mainly consists of the 5 following tests:- Optical Insertion Loss- Optical Return Loss- Optical Time Domain Reflectometry traces- Chromatic Dispersion testing- Polarized Mode Dispersion testingCore
49 Common Connector Types SC Commonly referred to as Sam CharlieST Commonly referred to as Sam TomFC Commonly referred to as Frank CharlieLC Commonly referred to as Lima Charlie
50 Connector Configurations PC or UPS vs APCSC - PCSC - APC
51 Inspect Before You Connectsm Dave intros the webinar and intros me
52 Focused On the Connection Bulkhead AdapterFerruleFiberFiber ConnectorAlignment SleeveAlignment SleevePhysical ContactFiber connectors are widely known as the WEAKEST AND MOST PROBLEMATIC points in the fiber network.
53 What Makes a GOOD Fiber Connection? The 3 basic principles that are critical to achieving an efficient fiber optic connection are “The 3 P’s”:Perfect Core AlignmentPhysical ContactPristine Connector InterfaceLight TransmittedCoreCladdingCLEAN
54 What Makes a BAD Fiber Connection? CONTAMINATION is the #1 source of troubleshooting in optical networks.A single particle mated into the core of a fiber can cause significant back reflection, insertion loss and even equipment damage.Visual inspection of fiber optic connectors is the only way to determine if they are truly clean before mating them.LightBack ReflectionInsertion LossCoreCladdingDIRT
55 Illustration of Particle Migration 11.8µ15.1µ10.3µCoreCladdingActual fiber end face images of particle migrationEach time the connectors are mated, particles around the core are displaced, causing them to migrate and spread across the fiber surface.Particles larger than 5µ usually explode and multiply upon mating.Large particles can create barriers (“air gap”) that prevent physical contact.Particles less than 5µ tend to embed into the fiber surface creating pits and chips.
56 Types of Contamination A fiber end-face should be free of any contamination or defects, as shown below:SimplexRibbonCommon types of contamination and defects include the following:DirtOilPits & ChipsScratches
57 Contamination and Signal Performance Fiber Contamination and Its Affect on Signal Performance1CLEAN CONNECTIONBack Reflection = dBTotal Loss = dB3DIRTY CONNECTIONClean Connection vs. Dirty ConnectionThis OTDR trace illustrates a significant decrease in signal performance when dirty connectors are mated.Back Reflection = dBTotal Loss = 4.87 dB
59 Visual Fault LocatorVFLs provide a visible red light source useful for identifying fiber locations, detecting faults due to bending or poor connectorization, and to confirming continuity.VFL sources can be modulated in a number of formats to help identify the correct VFL (where a number of VFL tests may be performed).FFL-100FFL-050
60 Advanced Tests Optical Return Loss (ORL) Optical Time Domain Reflectometer (OTDR)Detect, locate, and measure events at any location on the fiber linkFiber CharacterizationDetermines the services that the fiber can be carryBasic tests plus:Chromatic Dispersion (CD)Polarization Mode Dispersion (PMD)Optical Spectrum Analysis (OSA)Spectral analysis for Wavelength Division Multiplexing (WDM) systems
61 T-BERD 4000 FTTx / Access OTDR Introduction to OTDRIt’s the single most important tester used in the installation, maintenance & troubleshooting of fiber plantMost versatile of Fiber Test ToolsDetect, locate and measure events at any location on the fiber linkIdentifies events & impairments (splices, bends, connectors, breaks)Provides physical distance to each event/ impairmentMeasures fiber attenuation loss of each event or impairmentProvides reflectance / return loss values for each reflective event or impairmentManages the data collected and supports data reporting.T-BERD 4000 FTTx / Access OTDRIf you can only afford one piece of test gear in your network (and it’s not a small LAN), the OTDR is the tool you will need. It will do almost everything you need to fundamentally evaluate the fiber (except for advanced test, such as PMD, CD)
62 Background on Fiber Phenomena OTDR depends on two types of phenomena:Rayleigh scatteringFresnel reflections.Light reflection phenomenon = Fresnel reflectionRayleigh scattering and backscattering effect in a fiber
63 How does it work ?The OTDR injects a short pulse of light into one end of the fiber and analyzes the backscatter and reflected signal coming backThe received signal is then plotted into a backscatter X/Y display in dB vs. distanceEvent analysis is then performed in order to populate the table of results.OTDR Block DiagramExample of an OTDR traceOTDR’s are similar in principle to:Copper TDRRadarSonarShoot from one endcollect reflected signaltie round trip time to one way distance.
64 Type of Fiber and Wavelengths Single Mode (SM)1310 & 1550nm are primary wavelengths used in SM OTDR measurements1625nm is used in trouble-shooting when testing on active networks is neededMultimode (MM)850 & 1300nm are dominant wavelengths used in MM transmission & testing1490 FTTH operating wavelengthWe believe 1490 is an unnecessary expense (to OTDR at 1490)1550 test wavelength is fully adequate to evaluate fiber for 1490 operation
65 Dynamic Range & Injection Level Dynamic Range determines the observable length of the fiber & depends on the OTDR design and settingsInjection level is the power level in which the OTDR injects light into the fiber under testPoor launch conditions, resulting in low injection levels, are the primary reason for reductions in dynamic range, and therefore accuracy of the measurementsEffect of pulse width: the bigger the pulse, the more backscatter we receiveThe higher the dynamic range the further the OTDR will see.The higher the dynamic range, the more expensive the OTDR will be.For best value determine the right module for the job.
66 What does an OTDR Measure ? DistanceThe OTDR measurement is based on “Time”: The round trip time travel of each pulse sent down the fiber is measured. Knowing the speed of light in a vacuum and the index of refraction of the fiber glass, distance can then be calculated.Fiber distance = Speed of light (vacuum) X time2 x IORConverts time (round trip time for signal to go out and backscatter return)
67 What does an OTDR Measure ? Attenuation (also called fiber loss) Expressed in dB or dB/km, this represents the loss, or rate of loss between two events along a fiber spanThe further the round trip of the backscatter the weaker the signal..The X axis plots distance & Y axis plots dB signal levelIt appears logically as a decreasing signal left to right over distance.
68 What does an OTDR Measure ? Event Loss Difference in optical power level before and after an event, expressed in dBAn event is either something that was placed on purpose (splice, connector)Or something that has happened to the fiber (bend)Depending upon the event, It’s going to look something like the aboveFusion Splice or MacrobendConnector or Mechanical Splice
69 What does an OTDR Measure ? Reflectance Ratio of reflected power to incident power of an event, expressed as a negative dB valueThe higher the reflectance, the more light reflected back, the worse the connectionA -50dB reflectance is better than -20dB valueTypical reflectance valuesPolished Connector ~ -45dBUltra-Polished Connector ~ -55dBAngled Polished Connector ~ -65dBReflectance relates to a specific event .This is especially critical in high speed networks (10G+)Or in applications that use high power lasers (RF Video overlay in FTTH)Reflectance can cause signal degradation and needs to be managed.
70 What does an OTDR Measure ? Optical Return Loss (ORL) Measure of the amount of light that is reflected back from a feature: forward power to the reflected power. The bigger the number in dBs the less light is being reflected.The OTDR is able to measure not only the total ORL of the link but also section ORLAttenuation (dB)ORL is similar to reflectance, but instead of a single event, ORL is a measure of a section or span of overall reflected signal.ORL of thedefined sectionDistance (km)
71 Optical Return Loss (ORL) Light reflected back to the sourcePAPCPPCPTPFLight SourcePhoto- diodeOptical return loss is the ratio of the output power of the light source to the total amount of back-reflected power (reflections and scattering). It is defined as a positive quantity.Reflectance (dB) is the ratio of reflected power to incident power due to a single interface. It is defined as a negative quantity PT: Output power of the light sourcePAPC: Back-reflected power of APC connectorPPC: Back-reflected power of PC connectorPF: Backscattered power of fiberPB: Total amount of back-reflected powerORL (dB) = 10Log > 0
72 Effects of High ORL Values All laser sources, especially distributed feedback lasers, are sensitive to optical reflection, which causes spectral fluctuation and, subsequently, power jitter. Return loss is a measure of the amount of reflection accruing in an optical system. A -45dB reflection is equivalent to 45dB return loss (ORL). A minimum of 45-50dB return loss is the industry standard for passive components to ensure normal system operation in singlemode fiber systems.Increase in transmitter noiseReducing the OSNR in analog video transmissionIncreasing the BER in digital transmission systemsIncrease in light source interferenceChanges central wavelength and output powerHigher incidence of transmitter damageThe angle reduces the back-reflection of the connection.SC - PCSC - APC
73 Optical Return LossRatio between the transmitted power and the received power at the fiber origin2 different test methods:Optical Continuous Wave Reflectometry (OCWR): A laser source and a power meter, using the same test port, are connected to the fiber under test.Optical Time Domain Reflectometry (OTDR)The laser source sends a signal at a know power level into the fiber, and the power meter measures the reflected power level at the same location.OCWR methodOTDR methodON/OFFBackscatter
74 CW Stabilized Light Source ORL Measurement MethodsOptical Continuous Wave ReflectometerAccuracy (typ.)± 0.5dBTypical Application- Total link ORL & isolated event reflectance measurements during fiber installation & commissioningStrengths- Accuracy- Fast & real time info- Simple & easy results (direct value)Weaknesses- No localizationCW Stabilized Light SourceProcess ControllerCouplerDisplayTermination PlugPower MeterOptical Time Domain ReflectometerAccuracy (typ.)± 2dBTypical Application- Perfect tool for troubleshooting- Spatial characterization of reflective events & estimation of the partial & total ORLStrengths- Locate reflective events- Single-end measurementWeaknesses- Accuracy- Long acquisition timePulsed Light SourceProcess ControllerCouplerDisplayPhotodetector
75 How to interpret a trace OTDR EventsHow to interpret a trace
76 How to interpret an OTDR Trace Do step you through interpretation of an OTDR trace, we’re going to utilize content from one of our Wall posters we’ve recently developed. It’s called “Undersanding OTDRs”.ILater in the Webex we’ll show you how you can get your own poster.So here you see an OTDR trace w/ lots of “events”.Let’s take a closer look at each one.
77 Front End ReflectionConnection between the OTDR and the patchcord or launch cableLocated at the extreme left edge of the traceReflectance:Polished Connector ~ -45dBUltra-Polished Connector ~ -55dBAngled Polished Connector up to ~ -65dBInsertion Loss: Unable to measureAt the very beginning of the OTDR trace you see the first connection.(reflective)Notice the spike (reflection) then a drop back down to a steady signal level.
78 Dead ZonesAttenuation Dead Zone (ADZ) is the minimum distance after a reflective event that a non-reflective event can be measured (0.5dB)In this case the two events are more closely spaced than the ADZ, and shown as one eventADZ can be reduced using shorter pulse widthsEvent Dead Zone (EDZ) is the minimum distance where 2 consecutive unsaturated reflective events can be distinguishedIn this case the two events are more closely spaced than the EDZ, and shown as one eventEDZ can be reduced using shorter pulse widthsAt some point you’ve probably heard people talk about dead zones.Where w/ your mobile phone, a dead zone is a spot where you can’t hear, an OTDR dead zone is an area where you cannot see true signal.It’s caused by reflective events (connector, mechanical splice)Within the definition of Dead Zone, there are two categories:ADZ & EDZ (above)
79 ConnectorA connector mechanically mates 2 fibers together and creates a reflective eventReflectance:Polished Connector ~ -45dBUltra-Polished Connector ~ -55dBAngled Polished Connector up to ~ -65dB Insertion Loss: ~ 0.5dB(loss of ~0.2dB w/ very good connector)A connector causes a reflection (air gap) which.An angled connector will have a much lower spike than a non-angled (PC type)
80 Fusion SplicesA Fusion Splice thermally fuses two fibers together using a splicing machineReflectance: NoneInsertion Loss: < 0.1dBA “Gainer” is a splice gain that appears when two fibers of different backscatter coefficients are spliced together (the higher coefficient being downstream)Fusion splices are the standard method of splicing fibers today.You won’t see them as much in LANs as you will in public networks.due to distances.Reflectance: NoneInsertion Loss: Small gain
81 Fusion Splices Direction A-B Direction B-A Biggest chalenge w/ OTDR’s here is getting the loss of the event accurate. If you need optimum accuracy you’ll need to shoort both directions. Bi directional measurements also emiminate gainers.
82 Macrobend Macrobending results from physical bending of the fiber. Bending Losses are higher as wavelength increases.Therefore to distinguish a bend from a splice, two wavelengths are used (typically 1310 & 1550nm)Here we’re only covering Macrobends; but…You’ll also here the two termsMacrobend & Microbend - Same result, but different causes…Macrobending loss refers to loss from physical bending of the fiberMicrobending loss is caused by pressure resulting in changing the physical shape fo the glass at a particular spot (core deformation)Reflectance: NoneInsertion Loss: Varies w/ degree of bend & wavelength
83 Mechanical SpliceA Mechanical Splice mechanically aligns two fibers together using a self-contained assembly.Don’t see too many of these anymore.Looks like a connector because it’s a mechanical connection w/ an air gap.This has been replaced for the most part by the fusion splice.Reflectance: ~ -35dBInsertion Loss: ~ 0.5dB
84 Fiber End or BreakA Fiber End or Break occurs when the fiber terminates.The end reflection depends on the fiber end cleavage and its environment.Reflectance: PC open to air ~ -14dBAPC open to air ~ - 35dBInsertion Loss: High (generally)An OTDR cannot tell you whether the end of the fiber is the real end or a cut or break.The signals look the same, so here you have to use your knowledge of the network.”How long is it supposed to be?”“ “Am I shooting the correct fiber?”
85 GhostsA Ghost is an unexpected event resulting from a strong reflection causing “echos” on the traceWhen it appears it often occurs after the fiber end.It is always an exact duplicate distance from the incident reflection.Ghosts are what they sound like (unless you believe in Ghosts)The are artifacts that show up on the trace that aren’t really there.But you can spot a ghost if you know what to look for…Now OTDRs have Ghost detect features that you can use to help identify them.Reflectance: Lower than echo sourceInsertion Loss: None
86 Typical Attenuation Values 0.2 dB/km for singlemode fiber at 1550 nm0.35 dB/km for singlemode fiber at 1310 nm1 dB/km for multimode fiber at 1300 nm3 dB/km for multimode fiber at 850 nm0.05 dB for a fusion splice0.3 dB for a mechanical splice0.5 dB for a connector pair (FOTP-34)Splitters/monitor points (varys with component)
88 Major Operational Challenges Plant Certification and Maintenance:Elevate plant performance to ensure reliable serviceHFC: Sweep & advanced return path certificationMetro Optical: Fiber and transport analysisMonitor Performance:Continuously monitor the health of your upstream and downstream carriersProactively identify developing problems before customers doMonitor both physical HFC & VoIP service call qualityUtilize advanced performance trending and analysis to prioritizeGet Installations Right the First TimeImprove installation practices to prevent service callbacks & churnVerify physical, DOCSIS® and PacketCable performanceDrive consistency across all techniciansTroubleshoot Fast:When issues occur, find and fix fastIsolate and segment from NOC, dispatch right tech at right timeField test tools that can find problems and verify fix
89 Return Path Monitoring Benefits Troubleshoot nodes faster to reduce MTTR and increase workforce efficiencyIdentify impairments before rolling a truck using both spectrum and packet monitoring technologyUse field meters to quickly locate ingress, the most common impairmentView performance history to understand transient problems to roll a truck at the right time to find and fix the issueReduce trouble tickets and customer churn by identifying problems before your subscribersRank nodes using convenient web-based reports for proactive maintenanceEasily and quickly detect impairments such as fast impulse noise, ingress, CPD, and laser clipping on all nodes 24/7View live spectrum, QAMTrak™ analyzers and a wide array of reports conveniently via the web
90 DOCSIS® 3.0 adds Capability to Bond up to 4 Upstream 64QAM Carriers! Four times 6.4 MHz = 25.6 MHz! (without guard-bands)Increased chances for laser clippingIncreased probability of problems caused by ingress, group delay, micro-reflections and other linear distortionsInability to avoid problem frequencies such as Citizens’ Band, Ham, Shortwave and CPD distortion beatsWhere are you going to place your sweep points?
91 Live Spectrum DisplayRemember only 2 people on the same RPM card at the same time and only 2 people on the same port at the same time.Discuss left side controlsDiscuss controls at the top of the screen includingSpectrum analyzer settingsZero spanReference Levels
92 Choose a carrier for QAMTrak First thing that needs to be done besides choose a node is to choose which upstream carrier for viewing
93 Getting To Know The QAMTrak Analyzer QAMTrak SectionsImpairment DashboardImpairment ChartsFFT Spectrum DisplayConstellationStrip ChartData TablesControl/Information Bar
94 QAMTrak Analyzer: Primary Sections Impairment DashboardThe top 3 selections show the health of the system; the bottom 6 show the impairments and frequency of the impairmentsDisplay in simple red light / green light format which impairments have violated admin-defined thresholds and what % of packets affected by each (rollup status)Shows min/max/average for health metrics and impairmentsProvides single-click launch points to detailed charts for each impairment type
95 Impairment Dashboard – Two Main Sections Top three boxes indicate HFC healthIs data corruption occurring within packets being demodulated?How tight are the constellation points before CMTS compensationHow well is the CMTS likely able to compensate for impairments presentBottom six boxes indicate how frequently each impairment type is occurringHow often does a packet come across which violates threshold?What is min/max/average for each impairment type?Which impairment(s) are my biggest problem right now?Clicking any button will launch a maximized impairment chart window within the QAMTrak Analyzer
96 Impairment Dashboard – General Interpretation Impairment/Health Metric LabelRollup Counter Percent of packets since start of QAMTrak session which have violated admin defined threshold for that impairment or metricSession Status (Background Color) Indicates whether impairment threshold has been violated during sessionLatest Value Value for last packet demodulated or current packet highlighted for historical packet analysisLatest Status Pass/Fail status for last packet demodulated or current packet highlighted for historical packet analysis( or )Min/Max/Average Minimum, Maximum, Average values for all packets captured during current QAMTrak session or since last resetCaveats: Only the latest 600 packets are displayed on strip chart and in tablesMin/Max/Average and Rollup Counter can reflect packets which are not visible in strip chart of tables for sessions with >600 packets captured!
97 Primary Impairments Impairment Dashboard Impairment Charts Provides detailed display for five primary impairment types plus codeword error strip chart – supplement Impairment DashboardCharts update for each packet in live mode or historical packet review modeY-Axes can be manually rescaled or auto-scaled, charts can be resized, many other options available through Flash interface
98 Primary MeasurementsImpairment DashboardImpairment ChartsFFT Spectrum DisplayProvides Spectrum Analyzer display without opening a separate windowFFT-based spectrum analyzer – will look different than standard PathTrak SADisplay will show what spectrum looked like at time of packet capture when reviewing captured packets in paused mode
99 Upstream Constellation Impairment DashboardImpairment ChartsFFT Spectrum DisplayConstellationCan display Equalized, UnEqualized symbol locations, or bothCan show latest packets, all historical packets, or bothDisplays constellation packet by packet when reviewing historical packets
100 QAMTrak Analyzer: Primary Sections Impairment DashboardImpairment ChartsFFT Spectrum DisplayConstellationStrip ChartSeparate chart traces for Equalized MER, Unequalized MER, and Carrier Level (on second Y-Axis)Detailed packet info available using hover functionCan use arrow keys to review historical packets one at a time
101 QAMTrak Analyzer: Primary Sections Impairment DashboardImpairment ChartsFFT Spectrum DisplayConstellationStrip ChartData TablesUsers can toggle between strip chart, all-packet data table, and unique MAC data tableTables are sortable by all rows, can be exported to .csv fileData can be copied from tables to clipboard for pasting into other apps
102 PathTrak WebView Code Word Errors CPE MAC Address The user can also place all metrics on the same pageCPE MAC Address
103 PathTrak WebView QAMTrak CPE MAC AddressCodeword Error DetectionEqualized and UnEqualized MERMicro-reflectionsIn Band Response – RippleGroup DelayIngress Under the CarrierImpulse Noise Detection
104 DOCSIS Downstream Codewords 122 of each RS codeword’s 128 symbols are data symbols, and the remaining six are parity symbols used for error correction.ITU-T J.83, Annex B states that the data is “…encoded using a (128,122) code over GF(128)…” which shows each RS codeword consists of 128 RS symbols (first number in first parentheses) and the number of data symbols per RS codeword is 122 (second number in first parentheses), leaving six symbols per RS codeword for error correction.DOCSIS downstream RS FEC is configured for what is known as “t = 3,” which means that the FEC can fix up to any three errored RS symbols in a RS codeword.
106 The Cable Video Network Video Passes Through Four Separate Operational Layers Before it Reaches the Home.MPEGHeadendMaster/Super HeadendIP TransportHub/HFCHomeOrigination and processingTransport through the IP networkMPEG edge-processingRF combiningDistribution over HFCInside PlantOutside PlantOff-air IngestVODCombinerDPISTBIP L2/L3CoreNetworkMPEG Mux.ModemEncryptionModulationPhonePurpose here is to illustrate the evolution of video monitoring for cable, highlight how JDSU arrived at the edge, and why this is the critical segment for monitoring.4 Segments are Ingest/Super Head-end, Backbone, Edge Head-end, HFC/Outside PlantEarly on, Video Monitoring in cable was driven by a corporate desire for “end to end” visibility of video services.Corporate owned the backbone portion of the network, and the early video monitoring solutions catered to this segment.The other “end” was then served by sticking light-duty probes at the egress of the edge headends.Net Result was limited visibility to the most critical element…In Backbone, pretty much only two things that can hurt video – IP packet loss or IP delays. These are fundamentally ethernet functions – no real value to deep service layer monitoring as nothing happens there.Cable continues to push video technology to the edge – this is where MPEG services are manipulated, massaged and processed. This is where visibility is most needed, but monitoring deep mpeg is complex and until recently, there was no cost-effective way to get deep 24/7 visibility.AT JDSU, we’ve been converging on the edge headend for years. With the Wavetek line we’ve always served the last segment – the HFC and outside plant – by providing RF engineers and techs with meters and more recently the RSAM for monitoring the RF at the combiner. On the inside plant side, our MPEG analyzer provide much needed visibility and troubleshooting for the MPEG elements in the head-end.Transition: In the original “end-to-end” diagram, the edge headend was a single node. In actuality there is a chain within the headend where MEPG streams are manipulated – isolating problem sources requires visibility between these devices. This is troublshooting need that JDSU has been serving for years with our MPEG analyzers.CMTSPCBut The MPEG Edge is the most critical layer and poses the most significant risk to video quality.
107 The RF edge is home to the most complex equipment in the network Current monitoring solutions focus on the national backbone and on validating the content when programming first enters the network.Often QoS issues (like tiling) are introduced by the complicated equipment at the network edgeIf you aren’t monitoring at the RF edge, only the subscriber will have visibility to the impairmentsYou’ve caused these problems, but you don’t see themTroubleshooting is initiated by a customer complaint and without this “edge” visibility you may spend multiple truck rolls and weeks isolating the source.MPEG edge-processingRF combiningOff-air IngestCombinerDPIMPEG Mux.EncryptionModulationCMTS
108 And currently this is the last place you’re monitoring the video? Often QoS issues are introduced by the complicated equipment at the network edgeLocal Off-Air Ingest:Provider issuesAntennas8VSB ReceiversMuxes to groom for regional networksProgram Insertion:Quality of ad being spicedPCR DiscontinuityDecoding/Timing of DPI informationMPEG edge-processingRF combiningEncryption:Encryption not-enabledEquipment configurationMultiplexing:Streams from regional networksGroomingTransratingOver-compressionEquipment configurationOff-air IngestCombinerDPIModulation:MPEG to RFEquipment configurationOversubscriptionMPEG Mux.EncryptionModulationCMTSRF Combining:Poor cablingPoor IsolationLoose connectorsDriver/Isolation amp issuesAnd currently this is the last place you’re monitoring the video?
109 You may already have monitoring… Outside PlantCMTSSTBPhonePCModemDPIMPEG Mux.EncryptionModulationIP L2/L3CoreNetworkVODCombinerInside PlantOff-air IngestIP monitoringIP monitoring… but your customers are still seeing issuesContent monitoring has traditionally been expensive.Typically deployed only where content enters the network.Content Monitoring is typically not deployed at the very edge of the networkThat leaves the most vulnerable spot in the network, in the dark
110 Detailed MPEG analysis detects the important issues Video/Audio QoS issues caused by equipment in the headend or local network are transport related and can be identified without performing content analysisVideo freeze result of lost programs or video PIDsAudio loss as a result of missing audio PIDsOther frozen/black/no-audio that are the result of content (and not the programs) in almost all cases isn’t anything local system personnel can do anything about.Content analysis also limited to unencrypted programming – preventing use at edge of the network.Content analysis is impractical and costly at the edge of the network.Investment is significantly more effective if focused on transport tools that provide complete visibility and troubleshooting directly at the edge modulator.
111 Get complete visibility – “Wrap the Edge” Video Monitoring is a video monitoring solution optimized for the network edgeMVP-200 probe (full line-rate MPEG over GigE)RSAM probe (Digital video RF, Analog video RF, DOCSIS)PVM – Simple, lightweight, centralized system to tie it all together.Origination and processingTransport through the IP networkMPEG edge-processingRF combiningDistribution over HFCInside PlantOutside PlantOff-air IngestVODCombinerDPISTBIP L2/L3CoreNetworkMPEG Mux.ModemEncryptionModulationPhoneCMTSPCMVP-200MVP-200RSAM
112 Example – TilingThe RF probe consistently reported Continuity error alarms on a QAM.This clip shows what your Customer experiencedthe impact of these CC errors
113 Another Example - Video Freeze Click on video to playHow do you explain this to your customer??Below are the alarms generated for the above event from the MVP:Event Starts - MinorContinues - MajorHLN_13 (27) MVP Trap QAM 28 OUTPUTTrap Console received trap traps/event.Time: January 6, :03:10 AM ESTSTB: 27 PID ID: -1 PID: -1 PID Type:Event ID: programLost Event Severity: minorFrom MVP: Card: 2Source IP: XX :60000 Dest. IP: XXX :28115Ends - ClearHLN_13 (27) MVP Trap QAM 28 OUTPUTTrap Console received trap traps/event.Time: January 6, :03:17 AM ESTSTB: 27 PID ID: -1 PID: -1 PID Type:Event ID: programLost Event Severity: majorFrom MVP: Card: 2Source IP: XX :60000 Dest. IP: XXX :28115HLN_13 (27) MVP Trap QAM 28 OUTPUTTrap Console received trap traps/event.Time: January 6, :03:21 AM ESTSTB: 27 PID ID: -1 PID: -1 PID Type:Event ID: programLost Event Severity: clearFrom MVP: Card: 2Source IP: XX :60000 Dest. IP: XXX :28115
114 Knowing is only half the battle… Monitoring tells you when you have a problem.To isolate the problem source, the ops staff needs troubleshooting tools as well.Remote access via PVM gives service level visibility at the edge of your network, from anywhere.Critical in digital video, where problems are intermittent and spurious.Critical at the edge, where staff may be hours from the equipment.JDSU’s monitoring probes are unique in providing integrated real-time analyzers for troubleshooting.Troubleshoot anytime, anywhere.
115 Video Monitoring Application Identify and segment problems using intuitive displaysRF or MPEG?Outside plan, headend or source issueWidespread or localized?Intermittent or persistent problem?Find root-cause with advanced troubleshootingClick an event or status bar to get a live displayCapture transport streams to share with your network equipment suppliersView table decodes to understand impairmentsAccess Historical PM ReportsNetCompletePer Program, Per NodeWorst OffendersKey Performance IndicatorsA source issue means it is coming into the headend bad, so it could be a transport problem, a problem with the content from the provider or a problem in the master headend. Basically it is not a problem created in this headend is the important thing to understand.
116 Network Management System Integration SNMP and XML API:Designed to be flexible and easily integratedPer Program and Per Stream, real-time dataReal-time per program status to one system viewWe can integrate with whomever whenever. We recognize that our customer already have management platforms in place, and do not want to have to deal with yet another monitoring platform.The MVP-200 was designed to be flexible and agnostic to the management system above it. We are a fact finder and truth seeker. Our job is to report on the MPEG services, and provide accurate information to the management platform. NO intermediary layer required! No need for a server to take our probe data and intrepret it. No need to deploy our own management system. Buy one MVP-200, buy 100 MVP-200’s, and plug them right into your existing management platform.Note that this slide has been very successful at getting customer’s engaged about the MVP-200 potential. This slide is Miranda’s iControl integration of the MVP The network model on top has block elements for the NEM equimpent – Cisco routers and SEM’s here. Prior to our MVP-200, Miranda could easily display diagnostics from those elements, and could monitor the physical layer, but had no fault management options for the programs at the MPEG Service layer. Once we were integrated, they got the bottom portion operational. All of the green “chicklets” on the bottom are real-time, per program statuses being provided by the MVP-200. Customizable alarm settings on a per program basis – SNMP interface. They can launch the MVP-200 GUI remotely for troubleshooting programs, with no impact to the monitoring done here.This is a good slide to end on – it’s repeated at the end of the deck.
117 Solve real problems today Why Video Monitoring?Solve real problems todayOptimized for an operations staffReal-time alarming direct to local staffComplete RF component for analog, digital and DOCSISCost-EfficientFraction of the cost of conventional content monitoringProximity to the EdgeMonitor right at hand-off to access network, visibility for entire digital networkIsolate problem sourcesIntegrated remote analyzers at IP and RF