EVLA Fiber Selection
Critical Design Review
December 5, 2001
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
Identify Optical Requirements
IF Parameters
Bit Rate / Channel
Number WDM Channels
Channel Spacing
Channel Wavelengths
Bit Error Rate
Digital RMS SNR (Q)
Maximum Fiber Length
Minimum Fiber Length
Operation Temperature
10 Gbits/s
12 or 16 Channels
200 GHz Spacing
C-Band
10-9 Initial, 10-6 Final
6 - Initial, 4.7 - Final
21.6 km
625 m
-12 C to 35 C
IF Signal Path
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)
Maximum Bit Rate w/o Penalty
Dispersion Power Penalty (22 km)
Max. Launch Power
Cost Relative to SMF-28
5.5 dB
16.4 Gbits/s
0.5 dB
3.8 dBm
>200%
5.5 dB
20.8 Gbits/s
0.3 dB
2.5 dBm
167%
6.6 dB
8.2 Gbits/s
2 dB
4.3 dBm
100%
Transmission Losses
Fiber Attenuation
Connectors, Splices, Bends
MUX, DMUX
Total Transmission Losses
-6.6 dB
-6.3 dB
-12.5 dB
-24.5 dB
Elements
No. Units
Loss/Unit (dB)
IF Rack to Vertex Room Bulk head
Launch Power
16ch WDM MUX
1
-6.00
Connector
3
-0.30
Fiber (km)
0.004
-0.30
Vertex Room Bulk head to Antenna Pad
Pv tx bulkhead =
Connector
1
-0.30
Fiber (km)
0.02
-0.30
Farthest Antenna Pad to CB Termination Panel
Plast antenna pad =
MIL Connector
2
-0.50
Connector
1
-0.30
Fiber (km)
0.7
-0.30
Splice
2
-0.10
Bends
18
-0.10
CB Termination Panel to Patch Panel
Ptermination panel =
Connector
3
-0.30
Fiber (km)
22
-0.30
EDFA Gain
1
Correlator Patch Panel to Correlator Receiver
PIF patch panel =
Fiber (km)
0.004
-0.30
Connector
3
-0.30
16ch WDM DMUX
1
-6.50
Received Power
Receiver Sensitivity
Margin
Loss (dBm)
0.00
-6.00
-0.90
0.00
Q (linear)
31.20
-6.90
-0.30
-0.01
-7.21
-1.00
-0.30
-0.21
-0.20
-1.80
-10.72
-0.90
-6.60
12.00
-6.22
0.00
-0.90
-6.50
-13.62
-20.00
6.38
-25.20
6.00
0.00
Erbium Doped Fiber Amplifiers
— (
)
— (
)
— (
)
OEM of EDFA
EDFA Performance
• All channels
will fall in the
linear region
Result #1
• Single Mode Fiber with an EDFA
will have adequate optical power.
•But what about Q ?
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.
Eye Pattern
Polarization Dependent Loss
Connectors[6]
Multiplexers
Receiver
Amplifier
Total PDL
No. Units
Loss/Unit
(dB)
PDL
(dB)
13
2
1
1
0.1
0.1
0.12
0.5
1.3
0.2
0.12
0.5
2.12
Chromatic and Polarization
Dispersion
tD when L = 22 km
PD at 10 Gbits/s
SMF-28
43 ps
2 dB
MetroCor
17 ps
0.3 dB
LEAF
21.6 ps
0.5 dB
Power Penalty Budget
EVLA IF System Power Penalties (in dB)
Extinction Ratio
Crosstalk
Chromatic Disp. (SMF-28)
PMD
Nonlinearities
PDL
Component Aging
Margin
Total Power Penalties (dB)
Total Power Penalties (Linear)
-1.86
-2.00
-2.00
-0.04
0.00
-2.12
-3.00
-3.00
-14.02
-25.23
Q Budget
Description
-9
Reciever (10 )
Power Penalties
Transmitter Q
Last Pad
6
25.23
31.2
First Pad
()
()
()
Result #2
Achieve a BER of 10-9
— Launch Requirements - 10 Gbits/s @ 0 dBm
— Launch Q = 31
Receiver
— Assumes sensitivity -20 dBm
— 10-9 , @ 10 Gbits/s
Cost Comparison
SMF 28
100%
MetroCor
167%
LEAF
200%
Fiber Allocations
IF 120 Gbps WDM
LO - 2.048GHz, 512 MHz, 128 MHz
MCB Ethernet
Battery Back-up Communication
Telephone Digital System
Total Lit Fibers per Antenna
12 Fibers Installed per Pad, 5 spares
1
1
2
1
2
7
System Budget
Double Armor Cable, SMF-28
EDF Amplifier (27)
Total
$636,000
$300,000
$936,000
CDR Recommendation
• Single Mode Fiber, SMF
• Twelve fibers per pad
• Fourteen connectors
• Twenty-seven erbium doped fiber amplifiers
• Prototype before purchase