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 Bandwidth2-4 GHz — Clock Rate 4096 MHz — Resolution3 Bits — Aperture Time50 Ps — Clock Jitter5 Ps — Clock Rise Time25 Ps

IF - DTS Specifications Bit-Error-Rate (End-of-Life)10 -6 Data Bit rate per Polarization24 GHz Data Bit rate per Antenna (12)96 GHz Formatted Bit rate per Antenna120 GHz Jitter ContributionN/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 -12 C to 35 COperation Temperature 625 mMinimum Fiber Length 21.6 kmMaximum Fiber Length 6 - Initial, FinalDigital RMS SNR (Q) Initial, FinalBit Error Rate C-BandChannel Wavelengths 200 GHz SpacingChannel Spacing 12 or 16 ChannelsNumber WDM Channels 10 Gbits/sBit Rate / Channel

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 WDM1 LO GHz, 512 MHz, 128 MHz1 MCB Ethernet2 Emergency Communication1 Telephone Digital System2 Total Lit Fibers per Antenna7 12 Fibers Installed per Pad with 5 spares

Fiber Comparison

Transmission Losses

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 = ( I 1 - I 0 ) / ( i 1 + i 0 ) ( I 1 – I 0 ) is the excess electric signal available for distinguishing between a 1 and a 0. ( i 1 + i 0 ) is the RMS electric current induced by noise during a transition.

Transmission Quality For BER = the system requires: Received Q > 6 Received power > –20 dBm.

Eye Pattern

Polarization Dependent Loss

Chromatic and Polarization Dispersion

Power Penalty Budget

Q Budget

Result #2 Achieve a BER of — Launch Requirements dBm — Launch Q = 31 Receiver — Assumes sensitivity -20 dBm — Gbits/s

Cost Comparison

Fiber Allocations

System Budget

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