sjd/jjadvisory - sept 20031 fiber phase stability status steven durand & jim jackson september...

SJD/JJ Advisory - Sept 2003 1

Fiber Phase Stability Status

Steven Durand & Jim Jackson

September 8, 2003

National Radio Astronomy Observatory

a facility of the National Science Foundation

operated under cooperative agreement by

Associated Universities, Inc.


ArrayDistribution

Panel

I FPatch Panel12 WDM per

Fiber

LOPatch Panel

M & CPatch Panel(TX & RX)

74 Fibers 148 Fibers 148 Fibers

Array FO TerminationRoom

North ArmFiber Entrance

(23 Pads,276 Fibers)

East ArmFiber Entrance


West ArmFiber Entrance


Space ReservedE Array Option

(360 Fibers)


OFS BrightWave Cable

• Double armor loose tube cable

– Corrugated, copolymer coated carbon, steel tape applied longitudinally

• Polyethylene jacket– 1.4 mm Outer, 1.2 mm Middle, 1.0 mm Inner

• Glass/epoxy composite dielectric rod core


Cable Cross Section


OFS Matched Cladding Fiber

• Matched cladding single-mode – Nonzero-dispersion optical fiber

• Gel-filled buffer tubes– Installed in a reverse oscillation lay – 12 fibers per tube


OFS Matched Cladding Specifications @ 1310 nm

• Attenuation coefficient: 0.31-0.35 dB/km• Chromatic dispersion: -9 ps/nm-km• Dispersion slope: 088 ps/nm2-km• Group index of refraction: 1.471• Polarization M dispersion: ≤0.5 ps/(km)1/2 • Rayleigh Backscattering: -49.6 dB• Coefficient of Expansion*: 6 PPM/˚C

* NRAO Estimate


LO Technical RequirementsBased on the Scientific Goals

after all Round-Trip Corrections

• Short Term: < 0.5 ps RMS per second

• Long Term: < 1.4 ps per 30 minutes ~20 degrees at 40 GHz

• Delta Slope: < 0.2 ps change per minute Over 30 minutes


Phase Error Allocation

• Front End 0.4 ps per 30 Min

• LO Converters 0.6 ps per 30 Min

• Fiber System 0.4 ps per 30 Min– RTP measurement accuracy* 0.05 ps

– 512 MHz + 128 Hz jitter* 0.1 ps

– Fiber induced errors 0.25 ps

*NRAO estimates


Round Trip Block Diagram

1310 nm LaserModulator

Optical Receiver-30 dBm

Correlator

PhaseLock Loop

128 HzSignal

512 MHz Signal

Maser

512 MHz Generator128 Hz Generator

5 MHz Generator

512 MHz + 128 HzOffset Generator

Phase Detector

Comparitor


Verification

• Is the magnitude and rate of change of the phase caused by the 22Km tolerable?

• How identical are the two fibers used in the round trip phase measurement system?

Or Is the un-compensated difference in phase uncertainty tolerable?


RTP Test Setup

X

OptTx

OptRx

RTP1

512 MHz

RTP1

DC Out

RTP2

DC Out

Mixers

XOptRx

RTP2

Laser

OpticalSplitter

Test designed and operated byDoug Gerrard and Don Haenichen


RTP Test Hardware


Analog Mixer as a Phase Detector


Temperatures

10

15

20

25

30

35

40

45

8/11/03 18:00 8/11/03 20:00 8/11/03 22:00 8/12/03 0:00 8/12/03 2:00 8/12/03 4:00 8/12/03 6:00 8/12/03 8:00 8/12/03 10:00

Date/Time

Deg

rees C

Inner Temp Room Temp Outer Temp

RTP and Diff

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

160.00

180.00

200.00

8/11/03 18:00 8/11/03 20:00 8/11/03 22:00 8/12/03 0:00 8/12/03 2:00 8/12/03 4:00 8/12/03 6:00 8/12/03 8:00 8/12/03 10:00

Date/Time

Ro

un

d T

rip

Ph

as

e S

hif

t (d

eg

ree

s)

70.00

75.00

80.00

85.00

90.00

95.00

100.00

Dif

f P

ha

se

Sh

ift

(de

gre

es

)

RTP (degrees) Diff (degrees)

65 Km Spool Test

5 cycles X 360° / 13° = 137 Ratio

6 ppm / °C


Calculated Temperature Effects on Phase

• 22 Km Length Change per (6 ppm / °C)– 30 minutes = 5.4 um → 0.028 ps– 6 months = 1.4 m → 6677 ps (3.4 cycles)

• 30 meters in Control Building per– 30 minutes = 10.4 mm → 49 ps

• 28 meters up the Antenna per– 30 minutes = 10.7 mm → 51 ps

Total ~ 100 ps/30 min (EVLA Memo – 44)

(100 ps / 30 min) / (137 Ratio ) = ~.73 ps / 30 min


Master Pad Fiber Enclosure


Fiber Enclosure Temperature


Master Pad Fiber EnclosureSlope represents 0.5 ps / 30 minutes½ for 2 way trip = 0.25 ps / 30 minutes

1° Phase Shift = 5.4 ps


Master Pad Fiber Enclosurewith Insulation


Insulated Fiber Box Temperatures


RTP1 and RTP2

62.0

64.0

66.0

68.0

70.0

72.0

74.0

76.0

78.0

80.0

82.0

84.0

8/29/0312:00

8/29/0318:00

8/30/030:00

8/30/036:00

8/30/0312:00

8/30/0318:00

8/31/030:00

8/31/036:00

8/31/0312:00

8/31/0318:00

9/1/030:00

9/1/036:00

9/1/0312:00

9/1/0318:00

9/2/030:00

9/2/036:00

9/2/0312:00

Date/Time

RT

P1

an

d R

TP

2 P

ha

se

Sh

ift

(de

gre

es

)

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

Dif

fere

nc

e P

ha

se

Sh

ift

(de

gre

es

)

RTP1 (degrees) RTP2 (degrees) Difference (degrees)

Insulated CB to MP

1° Phase Shift = 5.4 ps

Test Apparatus drift is +/- 0.5 ° per day

~ 0.22 ps per 30 minutes


Cable Wrap Test Fixture

• Antenna – 540 ° Total

– 40 ° / minute

• Test Fixture test results:

< 0.5 ° shift

@ 1.2 GHz


Conclusion

• The magnitude and rate of change of the phase shift caused by the buried 22Km is tolerable.

6 ppm / °C or Total ~ 0. 028 ps / 30 min

~ 3.4 cycles per 6 months

May have a problem with CB and Antenna fiber• The un-compensated difference of two fibers is

Measured less than ~.73 ps / 30 min• The cable wrap may also work.


Elevation Cable Bend


LO Block Diagram

512 MHzVCO

512 MHzVCXO

ZEROCROSSINGDETECTOR

PLL

512 MHz + 128 Hz

PHASEMONITOR

PLL

MASTER LOGENERATOR

MASTER LO128 Hz TO

DCSSYSTEM

MASTER LO128 Hz 5 MHz

MASTEROFFSETGENERATOR

ROUND TRIPPHASE

MEASUREMENT

MOD LASER

DEMOD

512 MHzDEMOD

512 MHzVCXO

PLLCLEAN

UP

LOREFERENCE

RECEIVER

512 MHz

ANTENNAFO

SYSTEM

CENTRALFOSYSTEM

OPTICALSplitter


LO Optical Loss Budget

1310 nm LaserModulator

-6.2 dB6 dBm

Optical Receiver-30 dBm

22 km Fiber

-8.8 dBm

-6.2 dB22 km Fiber

OpticalReceiver-30 dBm

-25 dBm

Connectionsand Splices

Connectionsand Splices

Splitter

5%95%

-23 dBm

-8.8 dBm

-1 dB -14 dB


Existing 6" Waveguide Conduit

1 5/8" Unitstrut

2" Liquid-Tight FMC

6" X 2" Threaded PVC45 degree ‘Y’

Track Level

Unistrut set inConcrete to 18" depth

SS Splice EnclosureAntennaUmbilicalJumper

Connector

8.5in. 14.5in.

17.0in.

19.0in. (min)

36.0in.(max)


EVLA Fiber

DN2 DN3 DN4 DN5 DN6 DN7 DN8 DN9 CN5

TDN

CN6 CN7 CN8 CN9

TCN

BN5BN6BN7BN8BN9AN5AN6AN7AN8AN9

TBN

TANb

TANc

EVLA North Arm FiberCable Plan

Control Building

TANa

96 f iber2,604 f t

60 f iber4,173 f t

60 f iber12,965 f t

60 f iber12,965 f t

60 f iber13,642 f t

36 f iber20,709 f t

STCN.01STDN.01

STBN.01

STAN.01

STAN.02STAN.03

Splice

Manhole

Trunk Cable

Homerun Cable

Symbol Key

STAN.03

TANc

AN9


Base SpliceEnclosure

SamplerRACK

LO System

Vertex Room

Lower PedRoom

Upper PedRoom

MCBRACK

ElevationCableBend

AzimuthCable Wrap

12:1 Mux

Vertex SpliceEnclosure

12 SingleMod Fiber

2

2

1

~92ToMIBs Multi

PedestalSplice

Enclosure

12 Single Mode Fibers to Control Building

24Multi

ToMIBs

24Multi

HybridCable

12

sjd/jjadvisory - sept 20031 fiber phase stability status steven durand & jim jackson september...

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