EVLA Fiber Selection Critical Design Review

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EVLA Fiber Selection Critical Design Review

• December 5, 2001

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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)

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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

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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 lt1 Loss of Data

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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

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Identify Optical Requirements
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IF Parameters
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IF Signal Path
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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

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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
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Fiber Comparison
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Transmission Losses
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Erbium Doped Fiber Amplifiers

• ( )
• ( )
• ( )

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OEM of EDFA
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EDFA Performance

• All channels will fall in the linear region

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Result 1

• Single Mode Fiber with an EDFA will have
  adequate optical power.
• But what about Q ?

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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.

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Transmission Quality

• For BER 10-9 the system requires
• Received Q gt 6
• Received power gt 20 dBm.

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Eye Pattern
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Polarization Dependent Loss
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Chromatic and Polarization Dispersion
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Power Penalty Budget
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Q Budget
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Result 2

• Achieve a BER of 10-9
• Launch Requirements - 10 Gbits/s _at_ 0 dBm
• Launch Q 31

• Receiver
• Assumes sensitivity -20 dBm
• 10-9 , _at_ 10 Gbits/s

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Cost Comparison
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Fiber Allocations
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System Budget
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CDR Recommendation

• Single Mode Fiber, SMF
• Twelve fibers per pad
• Fourteen connectors
• Twenty-seven erbium doped fiber amplifiers
• Prototype before purchase