j. monari 2 nd skads workshop 10-11 october 2007 best-2 test bed: radio over fiber experiences...

J. Monari2nd SKADS Workshop 10-11 October 2007

BEST-2 test BEST-2 test bedbed: : Radio over Fiber Radio over Fiber

experiencesexperiences

Presented by Monari Jader IRA-INAF Radiotelescopio Croce del Nord Villafontana (BO) ITALY Email : [email protected]


SummarySummary

• Introduction: Coax Cables Vs. Fibers Introduction: Coax Cables Vs. Fibers

• Digital Optical link Vs. Analog Optical link Digital Optical link Vs. Analog Optical link

• Which kind of Fibers or connectors?Which kind of Fibers or connectors?

• Home made linkHome made link

• Collaboration with industry: ANDREW and Collaboration with industry: ANDREW and MITEQMITEQ


The costs of both of them are very similar (hardware and manpower)

Which solutions?

Coaxials vs FibersCoaxials vs Fibers

Coaxial cables to external cabins where

signals can be digitized and sent via Fast Ethernet links to the processing room

Analogue Optical Links directly from Focal Lines to the Processing Room


Coaxial solution:

MTBF: 10624h -> ~1.2y

RoF solution:

MTBF: 37137h -> ~4.2y

• MIL-HDBK-217-FN2 data base

• series reliability model

• 100% duty cycle

• operating temperature: 30°C

• environments:

• GM (Ground Mobile) for antenna equipment

• GF (Ground Fixed Uncontrolled) for cabin equipment

• GB (Ground Benign Controlled) for processing room equipment


RF Analog Optical Link Vs RF Analog Optical Link Vs digital link….digital link….

Big efforts are spent to design low cost analog links because they offer several benefits:

1) The electronic move from the outside cabins to the processing room in the central building.

2) More Reliable, less risks and easier maintenance.

3) No Sync, LO and PPS distribution from the main building to cabins.

4) Fibers are cheaper, lighter and more flexible than coaxial cables.

5) Fibers have more phase stability vs temperature and amplitude equalization in wide bandwidth than coaxial.


ConnectorsConnectors

APC (Angle Polished Connector) has RL>70dB → increases the performance of the RoF link (Dynamic and NF)

DIN/APC

SC/APC


Which kind of fiber to Which kind of fiber to choose?choose?

Tnom

T

t

nomt

TCD

610610

0

10

20

30

40

50

60

70

80

-20 -10 0 10 20 30 40 50

Temperature [°C]

TC

D [

pp

m/°

C]

loose fiber 1loose fiber 2

loose fiber 3loose fiber 4

tight fiber 1tight fiber 2


(extrapolations from the previous measurements)

Relative Phase variation Relative Phase variation among fibers among fibers


Freq=408MHz, Links lenghts = 300mt

Relative PhaseRelative Phase Stability Vs. TimeStability Vs. Time


IRA INAF analog home IRA INAF analog home made linkmade link


in

outopta R

RkkgdBG

4log10

221

2

10

21

2

2

221

21024

2log10kgTk

IIeRINIR

Rkkg

RdBNF

opt

DarkDDin

outopt

in

Linee ottiche

Linee elettriche

The Theoretical modelThe Theoretical model


Direct modulation of the laser

Optical source: Laser DFB 1310nm

Resistive matching

Utilizzo di un fotodiodo di monitor per realizzare un controllo in retroazione sul livello di potenza ottica emessa

Circuito di accensione lenta

Direct detection by photodiode PIN

Passive optical RX (No post-amplification)

From the idea to the From the idea to the realization…realization…


Link optimised at408MHz @ 16MHz BW

Gain -22.9dB

Gain Flatness

<0.1dB

Input Return Loss

>28.6dB

Output Return Loss

>30.9dB

Input IP3 +32.8dBm

Noise Figure 31dB

Link (not optimised) in the

300-600MHz band

Gainmin-23.7dB

Gainmax-22.1dB

Input Return Loss

>9.5dB

Output Return Loss

>24.2dB

Input IP3 >+30dBm

Noise Figure <31.25dB

MeasurementsMeasurements


0

100

200

300

400

500

600

1 10 100 1000

Quantity

Las

er (

DF

B)

cost

[eu

ro]

Year: 2004

Estimated cost = 500€ for a mass production of 400 pieces (3 years ago quotation)

Cost of the optical sourceCost of the optical source


Custom product:

1. Electrical specs (<1GHz)

2. Mech. Specs (RX housing)

TX RX=1310nm NF=36dBdB Gain=-25dB BW=(0.1-1)GHz IIP3>+33dBm

Input RL>15dB Output RL>20dB Power Supply=(12-15)Volt@=75mA

The collaboration withThe collaboration with industryindustry


BEST-2 optical link BEST-2 optical link slides show slides show


Collaboration with MITEQCollaboration with MITEQ


ConclusionConclusion

• Fibers are better than coaxials in the array for BEST purposes

• The Analog Optical link (RoF) simplifies and it is more reliable than the digital optical connection ones

• Loose fiber and APC connectors could be useful for large arrays

• Home made links are convenient if:

• keep in touch directly the factories of laser source to produce them

• To prepare a lab to test the home made links

• A collaboration with industry as ANDREW and MITEQ could be an useful and interesting opportunity

The experience gained with BEST SKA test best has shown:

…thank you for your attention


First observation of the transit of Cassiopea with BEST-1

1 Rx=¼ of cylinder

4 receivers=1 cylinder

5.6 deg.

7.1 deg. (1.7 deg.)

Old Crosshardwaredetector &

chart recorderBEST-1

IF


Future with MITEQFuture with MITEQ


700mt long

Dielectric protection against rodens

Loose cable construction

min (/T)

The BEST-2 analog optical linkThe BEST-2 analog optical link

j. monari 2 nd skads workshop 10-11 october 2007 best-2 test bed: radio over fiber experiences...

Documents