Fiber Selection CDR
• Decision about what fiber to install
— Select cable (Jan 02)
— Order cable (Jan 02)
— Receive cable (May 02)
— Start installation (June 02)
— Complete install (June 03)
IF Scientific Requirements
• Samplers Dominate the Digital Performance
— Input Bandwidth 2-4 GHz
— Clock Rate 4096 MHz
— Resolution 3 Bits
— Aperture Time 50 Ps
— Clock Jitter 5 Ps
— Clock Rise Time 25 Ps
IF - DTS Specifications
• Bit-Error-Rate (End-of-Life) 10-6
• Data Bit rate per Polarization 24 GHz
• Data Bit rate per Antenna (12) 96 GHz
• Formatted Bit rate per Antenna 120 GHz
• Jitter Contribution N/A
• Loss of Synchronization <1% Loss of Data
Task at Hand
• Select a fiber and a Configuration that can transmit the IF data from the antennas to the correlator.
— Identify Optical Requirements
— Compare Fibers
— Select Fiber
IF Parameters
-12 C to 35 COperation Temperature
625 mMinimum Fiber Length
21.6 kmMaximum Fiber Length
6 - Initial, 4.7 - FinalDigital RMS SNR (Q)
10-9 Initial, 10-6 FinalBit Error Rate
C-BandChannel Wavelengths
200 GHz SpacingChannel Spacing
12 or 16 ChannelsNumber WDM Channels
10 Gbits/sBit Rate / Channel
Types of Fiber Analyzed• Corning Products
— SMF-28, Standard Single Mode Optical Fiber
— MetroCor, Non-Zero Dispersion Shifted Fiber
— LEAF, Large Effective Area Fiber
• All three fiber types will work for EVLA
Fiber Allocations
IF 120 Gbps WDM 1
LO - 2.048GHz, 512 MHz, 128 MHz 1
MCB Ethernet 2
Emergency Communication 1
Telephone Digital System 2
Total Lit Fibers per Antenna 7
12 Fibers Installed per Pad with 5 spares
Fiber Comparison
Parameter LEAF MetroCor SMF-28
Attenuation (22 km) 5.5 dB 5.5 dB 6.6 dB Maximum Bit Rate w/o Penalty 16.4 Gbits/s 20.8 Gbits/s 8.2 Gbits/s Dispersion Power Penalty (22 km) 0.5 dB 0.3 dB 2 dB Max. Launch Power 3.8 dBm 2.5 dBm 4.3 dBm Cost Relative to SMF-28 >200% 167% 100%
Transmission Losses
Fiber Attenuation -6.6 dBConnectors, Splices, Bends -6.3 dBMUX, DMUX -12.5 dBTotal Transmission Losses -24.5 dB
Elements No. Units Loss/Unit (dB) Loss (dBm) Q (linear)IF Rack to Vertex Room Bulkhead
Launch Power 0.00 31.2016ch WDM MUX 1 -6.00 -6.00Connector 3 -0.30 -0.90Fiber (km) 0.004 -0.30 0.00
Vertex Room Bulkhead to Antenna Pad Pv tx bulkhead = -6.90
Connector 1 -0.30 -0.30Fiber (km) 0.02 -0.30 -0.01
Farthest Antenna Pad to CB Termination Panel Plast antenna pad = -7.21
MIL Connector 2 -0.50 -1.00Connector 1 -0.30 -0.30Fiber (km) 0.7 -0.30 -0.21Splice 2 -0.10 -0.20Bends 18 -0.10 -1.80
CB Termination Panel to Patch Panel Ptermination panel = -10.72
Connector 3 -0.30 -0.90Fiber (km) 22 -0.30 -6.60EDFA Gain 1 12.00
Correlator Patch Panel to Correlator Receiver PIF patch panel = -6.22
Fiber (km) 0.004 -0.30 0.00Connector 3 -0.30 -0.9016ch WDM DMUX 1 -6.50 -6.50
Received Power -13.62 -25.20Receiver Sensitivity -20.00 6.00Margin 6.38 0.00
Digital SNR (Q)
• Q is the ratio of signal current to noise current.
• Q = ( I1 - I0 ) / ( i1 + i0 )
• ( I1 – I0 ) is the excess electric signal available for distinguishing between a 1 and a 0.
• ( i1 + i0 ) is the RMS electric current induced by noise during a transition.
Transmission Quality
For BER = 10-9 the system requires:
• Received Q > 6
• Received power > –20 dBm.
Polarization Dependent Loss
No. Units Loss/Unit PDL (dB) (dB)
Connectors[6] 13 0.1 1.3 Multiplexers 2 0.1 0.2
Receiver 1 0.12 0.12 Amplifier 1 0.5 0.5
Total PDL 2.12
Chromatic and Polarization Dispersion
SMF-28 MetroCor LEAF tD when L = 22 km 43 ps 17 ps 21.6 ps
PD at 10 Gbits/s 2 dB 0.3 dB 0.5 dB
Power Penalty Budget
EVLA IF System Power Penalties (in dB)Extinction Ratio -1.86Crosstalk -2.00Chromatic Disp. (SMF-28) -2.00PMD -0.04Nonlinearities 0.00PDL -2.12Component Aging -3.00Margin -3.00
Total Power Penalties (dB) -14.02Total Power Penalties (Linear) -25.23
Q Budget
Description Last Pad First Pad
Reciever (10-9) 6 ()Power Penalties 25.23 ()Transmitter Q 31.2 ()
Result #2
Achieve a BER of 10-9
— Launch Requirements - 10 Gbits/s @ 0 dBm
— Launch Q = 31Receiver
— Assumes sensitivity -20 dBm
— 10-9 , @ 10 Gbits/s
Fiber Allocations
IF 120 Gbps WDM 1LO - 2.048GHz, 512 MHz, 128 MHz 1MCB Ethernet 2Battery Back-up Communication 1Telephone Digital System 2Total Lit Fibers per Antenna 712 Fibers Installed per Pad, 5 spares