optical installation planning
DESCRIPTION
opticTRANSCRIPT
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Installation Planning
LPB & RTB
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Tool for System Planning
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Power Budgeting Definition
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Power Budgeting dan Pemilihan Perangkat
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System Design Choices: Photodetector, Optical Source, Fiber
• Photodetectors: Compared to APD, PINs are less expensive and more stablewith temperature. However PINs have lower sensitivity.
• Optical Sources: 1- LEDs: 150 (Mb/s).km @ 800-900 nm and larger than 1.5
(Gb/s).km @ 1330 nm 2- InGaAsP lasers: 25 (Gb/s).km @ 1330 nm and ideally around
500 (Gb/s).km @ 1550 nm. 10-15 dB more power. However more costly and more complex circuitry.
• Fiber: 1- Single-mode fibers are often used with lasers or edge-emitting
LEDs.2- Multi-mode fibers are normally used with LEDs. NA and
should be optimized for any particular application.
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Use of Power Budgets
Anggaran terpenuhi jika daya terima di detektor ≥ sensitifitas penerima
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Link Power/Loss Analysis
Margin System][]/[][2
][][][
kmLkmdBdBlP
dBmPdBmPdBP
fcT
RsT
Total Power Loss
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Receiver Sensitivities vs. Bit Rate
The Si PIN & APD and InGaAsP PIN plots for BER= . The InGaAs APD plot is for BER= .
910
1110
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Link Loss Budget [Example 8.1]
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Power Margin
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Transmission Types
• Two types of transmissions:1. Link (point to point)
2. Networka. point to multipointb. Meshc. Ring
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Elements of Link/ Network Design
• Transmitter : Operating wavelength (), Linewidth (),Rise time, Bit-rate, Line format, Power
level
• Fiber : SMF/MMF, Fiber type – SMF28, DSF, etc, Cable loss, Spool length
• Rx : PSEN, PSAT, Rise time
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Elements of Link/ Network Design (cont.)
• Connection: No. of splice, Splice lossNo. of connectors, Connector Loss
• In Line Devices: Splitter, Filter, Attenuator, Amplifier
Insertion loss, Gain
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The Main Problems• Attenuation and
Loss• Dispersion
The Main Question • In Digital System - Data Rate
- Bit Error Rate• In Analog System - Bandwidth
- Signal to Noise Ratios
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System Factor Considerations Type of Fiber Single-mode or Multimode Operating Wavelength 780, 850, 1310 and 1550 nm
typical Transmitter Power Typically expressed in dBm Source Type LED or Laser Receiver Sensitivity and Overload Characteristics
Typically expressed in dBm
Detector Type PIN Diode, APD or IDP
Factors for Evaluating Fiber Optic System Design
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System Factor Considerations Modulation Code AM, FM, PCM or Digital Bit Error Rate (BER) (Digital Systems Only)
10-9 ,10-12 Typical
Signal to Noise Ratio Specified in decibels (dB) Number of Connectors Loss increases with the number of
connectors Number of Splices Loss is Loss increases with the
number of splices Environmental Requirements
Humidity, Temperature, Exposure to sunlight
Mechanical Requirements Flammability, Indoor/Outdoor Application
Factors for Evaluating Fiber Optic System Design (cont.)
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Optical Transmitter/ Sources LEDs
Output PowerModulation BandwidthCenter WavelengthSpectral WidthSource SizeFar-Field Pattern
Laser DiodesOutput PowerModulation BandwidthCenter Wavelength, Number of ModesChirp, LinewidthMode Field of the Gaussian beam
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Optical FiberMultimode Fiber
AttenuationMultimode DispersionChromatic DispertionNumerical ApertureCore Diameter
Single-Mode FiberAttenuationChromatic DispersionCutoff WavelengthSpot Size
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Optical Receiver/ Photodiode
Risetime/BandwidthResponse Wavelength RangeSaturation LevelMinimum Detection Level
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Simple Link
TX RX
Medium and Devices
OA OA
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Link Budget Considerations
Three types of budgets:
(1) Power Budget(2) Bandwidth or Rise Time Budget
(3) ?
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dB, dBm, mW
dB = 10 log (P1/P2)dBm Value % of 1 mW Power Application
0.0 100% 1.0 mW Typical laser Peak Output
-13.0 5% 50.0W Typical PIN Receiver Sensitivity
-30.0 0.1% 1.0W Typical APD Receiver Sensitivity
-40.0 0.01% 100.0W Typical LED Peak Output
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dB Power Out as a % of Power In
% of Power Lost
Remarks
1 79% 21% - 2 63% 37% - 3 50% 50% ½ the power 4 40% 60% - 5 32% 68% 6 25% 75% ¼ the power
7 20% 80% 1/5 the power
8 16% 84% 1/6 the power
9 12% 88% 1/8 the power
10 10% 90% 1/10 the power
Decibel to Power Conversion
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dB Power Out as a % of Power In
% of Power Lost
Remarks
25 0.3% 99.7% 1/300 the power
30 0.1% 99.9% 1/1000 the power
40 0.01% 99.99% 1/10,000 the power
50 0.001% 99.999% 1/100,000 the power
Decibel to Power Conversion
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IS THIS SYSTEM GOOD?
Example: Power Budget Measurement for Long Haul Transmission
PTx = 0 dBm
185 km
PSEN = -28 dBmSplice
Attenuation Coefficient, = 0.25 dB/km
Dispersion Coefficient, D = 18 ps/nm-km
Number of Splice = 46
Splice Loss = 0.1 dB
PMargin = 6 dB
Connector Loss = 0.2 dB
Connector
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CONCLUSION: BAD SYSTEM!!
Simple Calculation…. Fiber Loss = 0.25 dB/km X 185 km
= 46.3 dB
Splice Loss = 0.1 dB X 46 = 4.6 dB
PMargin = 6 dB
Total Losses = 46.3 + 4.6 + 0.4
= 51.3 dB
Power Budget, PRX ≥ PSEN !!
PRX = -57.3 dB
PRX = PTX – Total Losses – PMargin
= 0 – 51.3 – 6
Connector Loss = 0.2 dB X 2 = 0.4 dB
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How To Solve?Answer… Place an amplifier
But… What is the gain value??
Where is the location?And…
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First we calculate the amplifier’s gain..
Gain PSEN - PRX
Gain -28 – (-57.3)
Gain 29.3 dBTo make it easy, Gain 30 dB
Now…Where to put the amplifier?
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Three choices availablefor the location
Power Amplifier – At the transmitter
Preamplifier – At the receiver
In Line – Any point along fiber
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Let us check one by one…Power Amplifier: PTX + Gain = POUT
0 + 30 = 30 dBm
But is there any power amplifier with 30 dBm POUT?
NO, THERE ISN’T
Hence …
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What about Preamplifier?
POUT received = -57 dBm
Remember…
Preamplifier with 30 dB available? Yes
But, can it take –57 dBm?
Typically, NO
Hence …
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Let us check In Line Amplifiers
30 dB gain amplifier available here…
But, What value can it take?
Typically –30 dBm
So…
Now, we can find the location…
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Where is the –30 dBm point?
PTX – Loss At That Point = 0 dBm – 30 dB
Loss At That Point = -30 dBm
30 = x Length of That Point
Remember = 0.25,Point Length = 30/0.25
= 120 kmBut 120 km from Tx,
No. of splice = 120/4
= 30
Assume Other Loss = 0, Loss At That Point = Fiber Loss,
Splice Loss = 0.1 dB x 30 = 3 dB
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Also remember connector loss at amplifier and Tx…
2 connectorsConnector Loss = 0.2 dB x 3 = 0.6 dB
Total Losses = Fiber Loss + Splice Loss + Connector Loss
Actually, at 120 km,
= 30 + 3 + 0.6 = 33.6 dB
33.6 dB > 30 dB!! NOT GOOD!
Now, We have excess of 3.6 dB…Find the distance,
Fiber Loss Length = 3.6/0.25 = 14.4 km
Good Location = 120 km – 14.4 km = 105.6 km
+ 1 connector at Tx
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Let us confirm the answer…At 105.6 km from Tx,
Fiber Loss = 0.25 x 105.6 = 26.4 dB
No. of Splice at 105.6 km = 105.6/4 =26.4 = 27
Splice Loss = 0.1 x 27 = 2.7 dB
Total Losses = 26.4 + 2.7 = 29.1 dB
29.1 dB < 30 dB !!
CONFIRM…105.6 KM IS A GOOD LOCATION!!
PTx = 0 dBm
185 km
PSEN = -28 dBmSplice Connector
105.6 KM
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IS THIS SYSTEM GOOD?
PTx = -15 dBm
500 m
Using 850nm
PSEN = -25 dBm
Attenuation Coefficient, = 4.5 dB/km
Dispersion Coefficient, D = 18 ps/nm-km
Number of Splice = 0
Splice Loss = 0 dB
PMargin = 2 dB
Connector Loss = 0.5 dB
Server A Server B
Example: Power Budget Measurement for LAN
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BANDWIDTH BUDGET
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• Calculate the total rise times Tx, Fiber, Rx
• Calculate Fiber rise time, TFiber
Tfiber = D x x L
D = Dispersion Coefficient = LinewidthL = Fiber Length
Tx Rise Time, TTX = normally given by manufacturerRx Rise Time, TRX = normally given by manufacturer
System Rise Time
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Total Rise time, Tsys:
Tsys=1.1(TTX2+TRX
2+Tfiber2)1/2
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Dispersion Analysis (Rise-Time Budget)
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Bandwidth Budget
TX RX
Medium and Devices
T’
Δτ = T’ - T
T
OA OA
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What is a good Rise time?For a good reception of signal Tsys < 0.7 x Pulse Width (PW)
PW = 1/BitRate for NRZ1/2BitRate for RZ
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System rise-Time & Information Rate
• In digital transmission system, the system rise-time limits the bit rate of the system according to the following criteria:
periodbit RZ of %35
periodbit NRZ of %70
sys
sys
t
t
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Pengkodean Transmisi Optik
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Two-level Binary Channel Codes
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Example: Rise Time Budget Measurement for Long Haul Application
Tx rise time, TTX = 0.1 ns
Rx rise time, TRX= 0.5 ns
Linewidth() = 0.15 nm
Dispersion Coefficient, D = 18 ps/nm-kmFiber length = 150km
Bit Rate = 622MbpsFormat = RZ
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Fiber rise time, TF =Length x D x Linewidth()
= 150 km x 18 x 0.15 nm
= 0.4 ns
Total Rise time, TSYS = 1.1 TLS2 + TPD
2 + TF2
= 1.1 0.01 + 0.25 + 0.16
Simple Calculation….
TSYS = 0.77 ns
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Let say,Bit Rate = STM 4 = 622 MbpsFormat = RZ
Tsys < 0.7 x Pulse Width (PW)
Pulse Width (PW) = 1/(622x106)= 1.6 ns
0.77 ns < 0.7 x 1.6 ns
0.77 ns < 1.1 ns !!
Good Rise Time Budget!!
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Let say,Bit Rate = STM 16 = 2.5 GbpsFormat = RZ
Tsys < 0.7 x Pulse Width (PW)
Pulse Width (PW) = 1/(2.5x109)= 0.4 ns
0.77 ns < 0.7 x 0.4 ns
0.77 ns ≥ 0.28 ns !!
Bad Rise Time Budget!!
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Budget Summary Option Power
BudgetBandwidth
BudgetFinancial
A Source (LED vs. LD)
Δλ
850nm Mediocre Bad Cheap
1310nm Good Good Less expensive
1550nm Very good Very good Expensive
Modulation Bandwidth
LED NA Bad Cheap
LD NA Good Expensive
Output Power LED Mediocre NA Cheap
LD Good NA Expensive
Radiation pattern LED (far-field pattern)
NA Bad Cheap
LD (Gaussian beam)
NA Good Expensive
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Budget Summary
B Fiber Option Power Budget
Bandwidth Budget
Financial
Attenuation MM Mediocre Mediocre Cheap
SM Good Good Expensive
Dispersion MM Mediocre Mediocre Cheap
SM Good Good Expensive
Numerical Aperture (NA)
MM Mediocre Mediocre Cheap
SM Good Good Expensive
Core Diameter MM Mediocre Mediocre Cheap
SM Good Good Expensive
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Budget SummaryC Receiver (PIN vs.
APD)
Option Power Budget Bandwidth Budget
Financial
Rise time/ Bandwidth
PIN Mediocre Mediocre Cheap
APD Good Good Expensive
Response wavelength range
PIN Mediocre Mediocre Cheap
APD Good Good Expensive
Saturation Level PIN Mediocre Mediocre Cheap
APD Good Good Expensive
Minimum detection level
PIN Mediocre Mediocre Cheap
APD Good Good Expensive
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Cost/Performance Considerations
Components considerations such as :– Light Emitter Type – Emitter Wavelength – Connector Type – Fiber Type – Detector Type
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Link Power Budget Table [Example 8.2]
• Example: [SONET OC-48 (2.5 Gb/s) link]
Transmitter: 3dBm @ 1550 nm; Receiver: InGaAs APD with -32 dBm sensitivity @ 2.5 Gb/s;
Fiber: 60 km long with o.3 dB/km attenuation; jumper cable loss 3 dB each, connector loss of 1 dB each.
Component/loss parameter
Output/sensitivity/loss
Power margin (dB)
Laser output 3 dBm
APD Sensitivity @ 2.5 Gb/s
-32 dBm
Allowed loss 3-(-32) dBm 35
Source connector loss
1 dB 34
Jumper+Connector loss
3+1 dB 30
Cable attenuation 18 dB 12
Jumper+Connector loss
3+1 dB 8
Receiver Connector loss
1 dB 7(final margin)
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Sample Power Budget Calculation
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excercise
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Solution
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Example
• Laser Tx has a rise-time of 25 ps at 1550 nm and spectral width of 0.1 nm. Length of fiber is 60 km with dispersion 2 ps/(nm.km). The InGaAs APD has a 2.5 GHz BW. The rise-time budget (required) of the system for NRZ signaling is 0.28 ns whereas the total rise-time due to components is 0.14 ns. (The system is designed for 20 Mb/s).
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Example: Transmission Distance for MM-Fiber• NRZ signaling, source/detector: 800-900 nm LED/pin or AlGaAs
laser/APD combinations. ; LED output=-13 dBm;fiber loss=3.5 dB/km;fiber bandwidth 800 MHz.km; q=0.7; 1-dB connector/coupling loss at each end; 6 dB system margin, material dispersion ins 0.07 ns/(km.nm); spectral width for LED=50 nm. Laser ar 850 nm spectral width=1 nm;
laser ouput=0 dBm, Laser system margin=8 dB;
910BER
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Example:Transmission Distance for a SM Fiber• Communication at 1550 nm, no modal dispersion, Source:Laser;
Receiver:InGaAs-APD (11.5 log B -71.0 dBm) and PIN (11.5log B-60.5 dBm); Fiber loss =0.3 dB/km; D=2.5 ps/(km.nm): laser spectral width 1 and 3.5 nm; laser output 0 dBm,laser system margin=8 dB;