Transmission of analogue signals over fiber optics using...

Fourth International Conference on “New developments in photodetection”, Beaune, France, 19-24 June 2005 Daniel V. Camin, Dipartimento di Fisica and INFN, Milano 1

Transmission of analogue signals Transmission of analogue signals over fiber optics using the over fiber optics using the

OpticallyOptically--Coupled CurrentCoupled Current--Mirror architectureMirror architecture

Daniel V. Camin,Valerio Grassi, Lorenzo Caggioni and Massimiliano SquerzoniDipartimento di Fisica dell’Università and INFN, Milano, Italy

[email protected]

•• The origin and the principle of operation of the OCCM. The origin and the principle of operation of the OCCM. •• Reading out slow star signals with the Pierre Auger FD telescopReading out slow star signals with the Pierre Auger FD telescopes. es. •• Operating the OCCM with its input stage cooled to cryogenic temOperating the OCCM with its input stage cooled to cryogenic temperature.perature.•• Extending the signal bandwidth.Extending the signal bandwidth.•• Summary and conclusionsSummary and conclusions


A Fluorescence Detector telescope at the A Fluorescence Detector telescope at the Pierre Auger ObservatoryPierre Auger Observatory

MirrorMirrorCamera:Camera:20x22 20x22 PMTsPMTs

Corrector ringCorrector ring

UV filter:UV filter:300300--400 nm400 nm

2.20 m2.20 m

Detecting star signals allows determination of the absolute poinDetecting star signals allows determination of the absolute pointing ofting ofthe telescopes as well as its long term stability along its 20 ythe telescopes as well as its long term stability along its 20 years life. ears life.


The currents in a PMT biased with positive HVThe currents in a PMT biased with positive HV

IsIa

IRL

D1

Id+Ia

Dn HVPS

Id

Id

Ia

Vo = -Rf x IaRf

IsIa

IRL

D1

Id=Is-Ia

Id+Ia Is

Dn HVPS

AC coupling

AC coupling

Mirroring IMirroring IDD to ground potential would allow the measurement of to ground potential would allow the measurement of DC or very slowlyDC or very slowly--varying anode current.varying anode current.


How could the divider current be mirrored ?How could the divider current be mirrored ?State of the art on Galvanically decoupled amplifiers:

•• 1973, J. Sunderland1973, J. Sunderland’’s scheme:s scheme:

i

i f

i-i f

i L

HV REGION

V+

V-

~0

~i

-

+

V+

V-

i oK1

K2=

K1

i

i f

i-i f

i L

HV REGION

V+

V-

~0

~i

-

+

V+

V-

i oK1

K2=

K1

i oK1

K2=i o

K1

K2=

-

+i f

K2

-

+i f

K2

-

+i f

K2

-

+i f

K2

• LV power supply isrequiredrequired at the HV, or isolated region.

• In the last 32 years32 yearsmany solutions were proposed to bring bring LV to that regionLV to that region.

QuickTime™ and aTIFF (Group 4 Fax) decompressor

are needed to see this picture.

•• 1995, 1995, Hodson Hodson ((Texas InstrumentTexas Instrument):):• Introduction of the Linear Optocoupler (L.O.)• Still, LV was always required at the isolatedor HV region.

• Unacceptable for AugerUnacceptable for Auger: (10560 PMTs): (10560 PMTs)


Understanding the principle of operation of theUnderstanding the principle of operation of theOpticallyOptically--Coupled CurrentCoupled Current--Mirror Mirror in in three stepsthree steps..

i(t) ~~

Typ : PMT or ionizing detector

H.V.H.V.

(1) Detector biased

Step 1Step 1


UnderstandingUnderstanding……

i(t)H.V.H.V.

iL1~i(t)

~~

~~

ipd~ 0

i(t)

~~~<

i(t) ~~


H.V.H.V.

(1) Detector biased (2) Diodes interposed

Step 2Step 2


UnderstandingUnderstanding……

i(t) ~~


H.V.H.V.

(1) Detector biased

i(t)H.V.H.V.

iL1~i(t)

~~

~~

ipd~ 0

i(t)

~~~<

(2) Diodes interposed

A

~~~~~~~~<

~~~~~~~~ >

~i(t)

~~~~~~~~ >~~~~

H.V.H.V.i(t) ~~

~~~~

~ ~~~

~~~~

~~

~ 0iL1 ipd~i(t)

i(t)

iL2

APD

A= iL2 / iL1

β= ipd/ iL2

(3) Feedback action flips the currents and i(t) is mirrored

OCCMOCCM3rd step

(1) Detector biased (2) Diodes interposed (3) Feedback action flips the currents and i(t) is mirrored to ground potential.

Step 3Step 3


Features:Features:•• The input circuit is The input circuit is passivepassive andand low impedancelow impedance: ideal for current: ideal for current--signals.signals.•• NoNo LV power supply is requiredLV power supply is required at the input stage:less weight and spaceat the input stage:less weight and space•• DC to fast currentDC to fast current--signals signals linearly mirroredlinearly mirrored to ground potential.to ground potential.•• The only components The only components in contactin contact with the detector are: with the detector are:

aa LED, LED, aa photodiode, photodiode, and twoand two Optical Fibers. Optical Fibers.

i(t) ~~


H.V.H.V.

(1) Detector biased

i(t)H.V.H.V.

iL1~i(t)

~~

~~

ipd~ 0

i(t)

~~~<

(2) Diodes interposed

A

~~~~~~~~<

~~~~~~~~ >

~i(t)

~~~~~~~~ >~~~~

H.V.H.V.i(t) ~~

~~~~

~ ~~~

~~~~

~~

~ 0iL1 ipd~i(t)

i(t)

iL2

APD

A= iL2 / iL1

β= ipd/ iL2

(3) Feedback action flips the currentsand i(t) is mirrored

The The OpticallyOptically--Coupled CurrentCoupled Current--MirrorMirror


The OCCM: a current feedback loopThe OCCM: a current feedback loop

= Io

+-I

IL

A

K1 K2K1IL

I - K1IL

K2IL

Io = IK1

K2 .1

1+ 1K1A

= K’3I..

Includes:Includes:-- LEDLED--fiberfiber--APD optical couplingAPD optical coupling-- APD GainAPD Gain-- AmplifierAmplifier’’s current gains current gain

K1, K2: include LED/VCSELK1, K2: include LED/VCSEL--fibrefibre--photodiode optical couplingphotodiode optical coupling

Close to 1Close to 1


The OCCM integrated in the 880 PMT bases of the The OCCM integrated in the 880 PMT bases of the first two prototype telescopesfirst two prototype telescopes of Augerof Auger


The first star signals seen with an array of The first star signals seen with an array of PMTs PMTs biased with positive supplybiased with positive supply

Star: Alpha Lyrævmag: 0class: A0colour index (u-v): 0

Star: 13Vul, 17Vulvmag: 4.58, 5.06class: B9, B3colour index (u-v): -0.14, -0.67

0.1 µA → 1.5 pe/100ns →2.4pA

3.7 µA → 56 pe/100ns →90pA

Resolution referred to the cathode < 1 pAResolution referred to the cathode < 1 pA10 min 17Vul13Vul

µA

µA

Time slots of 20 sec

PMT

anod

e cu

rren

t


Pulsed operation: experimental resultsPulsed operation: experimental results

Open Loop Characteristcy = 8016.9x 2 + 2047.2x - 1.9582

R2 = 0.9998

0

50

100

150

200

250

0 0.025 0.05 0.075 0.1

Peak Current IN (mA)

Closed Loop Characteristc

y = 201.95x 2 + 177.6x + 6.5598R2 = 0.9999

0

50

100

150

200

250

0 0.2 0.4 0.6 0.8

Peak Current IN (mA)

Open LoopOpen Loop::saturation atsaturation ati i inin~ 85 ~ 85 µµAA

Driving LED currentDriving LED current vs. input currentvs. input current

Closed LoopClosed Loop::saturation atsaturation ati i inin ~ 750 ~ 750 µµAA

Small signal Small signal openopen--loop gain: loop gain: A = 2047A = 2047

Feedback return ratio:Feedback return ratio:ββ = (178)= (178)--11= 5.6 10= 5.6 10--33

Loop gain : 11.5 Loop gain : 11.5


Pulsed operation: InputPulsed operation: Input--Output characteristicsOutput characteristics

300K

Temperature Varying Open Loop Pulse Respon

0

50

100

150

200

250

300

-10 0 10 20 30

Time (us)

T = 77 KT = 300 K

Open-loop response at the driving-LEDs at 300 K and 77 K

Time [µs]

300K

77K

Pulse Response

-100

0

100

200

300

400

500

600

-1 0 1 2 3 4

Time (us)|

|

Transfer Characteristic; T = 77 K

y = 0,9948x - 2,9064R2 = 0,9996

0

100

200

300

400

500

600

0 200 400 600 800

Peak Current IN (uA)

I prepol. = 8 uALinear (I prepol. = 8 uA)

|

||

Transfer Characteristic

y = 0,8143x - 1,7505R2 = 0,9996

0

100

200

300

400

500

600

0 200 400 600 800

Peak Current IN (uA)

I prepol.= 80 uALinear (I prepol.= 80 uA)

300K

|

|

||


BehaviourBehaviour of an of an AlGaAsAlGaAs LED (LED (H22E4020IR)H22E4020IR) at 300Kat 300K

y = 2E-05x 2 + 0.0196x - 0.4147R2 = 0.9998

0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600 700

LED current (µA)

Rec

eive

r out

put (

mV)

300K

The LED efficiency is relativelysmall, specially at very low current where the LED operates

Pulse generator

Agilent 2406125 MHzAnalog receiver

200u fiber optics, SMA connector

77KPulse generator

Agilent 2406125 MHzAnalog receiver

200u fiber optics, SMA connector

77K

Light receiver: Agilent 2406 (pin photodiode followed by an amplifier)


……and at 77 Kand at 77 KStrong improvement, specially at very low current.

y = 0.1102x + 0.0298R2 = 0.9999

y = 2E-05x2 + 0.0196x - 0.4147R2 = 0.9998

0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600 700LED current (µA)

77K

300K

-- The LED efficiency is a factorThe LED efficiency is a factor5.65.6 higherhigher compared to 300 K. compared to 300 K.

-- Light flux is a perfectly Light flux is a perfectly linearlinearfunction of the current.function of the current.

-- Both are theBoth are the ideal characteristicsideal characteristicsfor the for the input stage input stage when it operates when it operates cooledcooled to cryogenic temperature.to cryogenic temperature.

Rec

eive

r out

put [

mV

]

MeanMean value of the linear term ratio atvalue of the linear term ratio at 77K/300K:77K/300K:15 with a 6 min to 36 max dispersion.15 with a 6 min to 36 max dispersion.


λ=782nm

Agilent Agilent 86142B86142B

Two Two GG--R R radiative centersradiative centersactive active at the at the same same time ?time ?

LED HFBR 1414LED HFBR 1414

Cooling optoelectronic componentsCooling optoelectronic components

T=300KT=300K826nm826nm

T=300KT=300K

782nm782nm

831nm831nm

T=77KT=77K


Avalanche photodiode C30902EAvalanche photodiode C30902E

•• Same Same responsivity responsivity atat 300 K 300 K and atand at 77 K77 K. . •• Required biasing voltage Required biasing voltage reducesreduces by by ~ 50 %.~ 50 %.

|

_


A compact scheme for the A compact scheme for the transmission of fast current signalstransmission of fast current signals

Optical Fibre 50/125

out

Input stage O.F.

i(t)

k1

k2

O.F.200/230

iout+

+

--

Driving VCSELs

RF

RAC

iL1 iL2

VCSELs

PREBIA

S

-Vb

APDRDC

O.F.

-Vpd


OpenOpen--loop vs closedloop vs closed--loop loop at 300Kat 300K

15.32 dB

Loop gain: 15.32 dB


OpenOpen--loop vs closedloop vs closed--loop loop at 77 Kat 77 K

13.32dB


Increasing the dynamic rangeIncreasing the dynamic range(preliminary, work in progress)(preliminary, work in progress)

i(t)H.V.H.V.

~~

~~i(t)

~~~< ~~~<

H.V.H.V.~~

~~i(t)

~~~< ~~~<

Stage with gain N

Stage with gain N/α


•• The OCCM has a The OCCM has a passive inputpassive input. There is . There is no needno need to bring any to bring any LVPS.LVPS.Power dissipationPower dissipation and and weightweight is saved.is saved.

•• 880880 OCCMOCCM’’s s installed in the basesinstalled in the bases of positively biased of positively biased PMTPMT’’ss, , allowed allowed recording the recording the extremely slowextremely slow star signals with two FD telescopes.star signals with two FD telescopes.

•• Cooling theCooling the OCCMOCCM’’s s input stage to input stage to 77 K77 K increases the open loopincreases the open loop--gain gain by a by a factor twofactor two and the signal threshold and the signal threshold decreasesdecreases. .

•• Fast pulses were sent via fiber optics to ground potential over Fast pulses were sent via fiber optics to ground potential over a a 12 MHz bandwidth and a ~12 MHz bandwidth and a ~100:1 dynamic range. 100:1 dynamic range.

•• The The only components in contact with the detectoronly components in contact with the detector: : a a LEDLED, a , a photodiodephotodiode and two and two optical fibersoptical fibers..

•• Work in progressWork in progress::-- Optimization of a scheme to increase dynamic range.Optimization of a scheme to increase dynamic range.-- Increase the feedback return ratio to extend the signal bandwidIncrease the feedback return ratio to extend the signal bandwidthth..

Summary and conclusionsSummary and conclusions

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