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

-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

 

 

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) 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

 

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

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

 

Cost Comparison

SMF 28 MetroCor LEAF100% 167% 200%

 

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

 

System Budget

Double Armor Cable, SMF-28 $636,000EDF Amplifier (27) $300,000Total $936,000

 

CDR Recommendation

• Single Mode Fiber, SMF

• Twelve fibers per pad

• Fourteen connectors

• Twenty-seven erbium doped fiber amplifiers

• Prototype before purchase