infrared avionics signal distribution: (phase 2

1Infrared Avionics Signal Distribution

Atiquzzaman and Sluss

Infrared Avionics Signal Distribution: (Phase 2: Experimental Setup and Verification)

Mohammed AtiquzzamanSchool of Computer Science

Jim Sluss & Filip SlaveskiSchool of Electrical & Computer

Engineering

University of OklahomaNorman, Oklahoma

Final PresentationNASA Glenn Research Center, Cleveland, Ohio

July 16, 2002

Hung NguyenDuc Ngo

NASA Glenn Research CenterCleveland, Ohio.



Introduction

n Pilots need to communicate with groundn Communications between aircraft and ground is Radio

Frequency (RF)n Signal Distribution within an aircraft is RFn Limited Communication within aircraft� Audio signal distribution� Telephone (new)� No video distribution� No communication between passengers and crew



RF Signal Distribution

n Coaxial Cables for RF signal distribution� Low bandwidth� Lossy

n Interference� Low signal to noise ratio

n Weight� Coaxial cables add weight to the aircraft

n Inflexible to future applications� passengers can select video to view� Internet browsing



Optical Communications

n No Electromagnetic interference, low transmission loss and electrical isolation (no spark hazard)� signal security� safer aircrafts

n Lightweight� suitable for aircraft

n Lots of bandwidth� Good for future applications� Voice, video, data can be carried over the same infrastructure

n Difficult to multiplex and demultiplex signals



Outline of presentation

n History of the project� Review of phase 1 (University of Dayton and NASA)

n Objectives of phase 2n Tests carried out in phase 2 (University of Oklahoma and

NASA)n Conclusions



Review of Phase 1



Point to Point Fiber Communication

TX

RX

TX

RX

RX

TX

TX

RX

950 1450MHz 950 1450MHz

100 150 MHz

100 150 MHz4 channnes(Passenger)

4 channels(VHF Antenna 2)

24 channels (Cockpit) 24 channel

(UHF Antenna 1)OF

OF

OF(1.3/1.55 micron)OF



Wavelength Division Multiplexing

TX

TX RX

RX

1280+1330nm1330 nm 1330 nm

1280 nm 1280 nm

(Cockpit) ( UHF Antenna 1)

(VHF Antenna 2) (Passenger)

OF

OF

OF

OF

OF

WAVELENGTHDEMUX

RX

RX TX

TX

1280+1330 nm

1330 nm 1330 nm

1280 nm1280 nm

( VHF Antenna 2) (Passenger)

(Cockpit) (UHF Antenna 1)

OF

OF

OF

OF

OF

WAVELENGTHDEMUX

n Signal extraction by splitters and wavelength demultiplexersn Signal injection by wavelength combiners



Signal Broadcast

n Optical signal split into 8 equal parts by power splittersn Distribution tree by two or more levels of splitters

Rx Rx Rx Rx Rx RxRxRx Rx

Rp Rp Rp

Tx

VHF Antenna(4 channels)

Repeater (Rp)



Optical fiber

AntennaPassenger

Optical Receiver

RF cable

Optical Transmitter

Cockpit

Optical combiner

Optical Splitter

Wavelength Demultiplexer

Optical Implementation in Aircraft



Objectives of Phase 2



Project Objectives

n Assemble a prototype of the previous fiber optic transmission system design.

n Carry out measurements to verify proof of concepts and establish performance metrics.

n Based on experimental findings, make recommendations for “best practice” system architectures for use in aircraft.



Basic Communications Link

ChannelSource Transmitter Receiver Destination

Noise Interference



Basic Fiber Transmission Link

DriveCircuit

SignalRestorer

LightSource

AmpPhoto-detector

Transmitter Channel Receiver

Electrical OutputSignal

Electrical InputSignal

Attenuation Distortion



Analog/Digital Transmission Link



Wavelength Division Multiplexing (WDM)

WDM

1300 nm

1550 nm WDM 1550 nm

1300 nm

WDM1550 nm

1300 nm

WDM 1550 nm

1300 nm

Unidirectional

Bidirectional

• Insertion loss



Dense WDM (DWDM)

TX

TX

TX

RX

RX

RX

λ1

λ2

λN

λ1

λ2

λN

.

.

.

.

.

.

WDM

(mux)

WDM

(demux)

Fiber



Bus-based Fiber Backbone Using DWDM

C F

D

B

E

A

Fiber Fiber

Fiber Fiber Fiber



Phase 2 Deliverables

n Experimental data for various measurements taken for different modulation schemes.

n Proof of concepts validation.n Establishment of performance specifications.n Recommendations on “best practice” implementations for

incorporation into aircraft.



Tests Carried out in Phase 2



Tests Performed

n Power Test� Transmitted Power� Reflected Power

n Delay Measurementsn SNR Testn CNR Testn Signal Quality Testn Distortion Testn Laser Spectrum Testn Video Testn BERT



Power Tests



Power Test Setup

n Power Measurements performed with the Network Analyzern Transmitted and Reflected Power measured for 1310 and 1550

nm

SPECTRUM ANALYZERTEKTRONIX

8554B


8554B

RF GENERATORFluke 6060B


NETWORK ANALYZER

Agilent 8712ET

NETWORK ANALYZER

Agilent 8712ET

TX ORTEL3541C 1310 nm


TX ORTEL1741A 1550 nm


RX ORTEL4518B 1310 nm


RX ORTEL2516A 1550 nm


WDM WDM

fiber

WDM WDM



Power Test Experimental Setup



Optical Tx and Rx



WDM



Transmitted Power in WDM

n Transmitted power averages:� – 45 dB for the 1310 nm� – 55 dB for 1550 nm

Power Measurements in WDM

-80

-70

-60

-50

-40

-30

-20

-10

0

0 200 400 600 800 1000 1200 1400

Frequency(MHz)

Pow

er (d

B)

Power for 1310 nm

Power for 1550 nm

1550 nm channel has greater insertion losses in the WDM network

Results comparable with literature: –50 dB for 1310 nm channel



Reflected Power in WDM

Reflected Pow e r in WDM

-50

-40

-30

-20

-10

00 500 1000 1500

Fr e quency(M Hz)

Po

wer

(d

B)

R e f le c t e d P o we r in 13 10 n m

R e f le c t e d P o we r in 15 5 0 n m

n Reflected power is the power reflected from the circuit in our case due to the electrical to optical conversion

n Reflected power averages:� – 25 dB for the 1310 nm� – 30 dB for 1550 nm

Results comparable with literature: 20 to 30 dB loss for electrical to optical conversions



Delay Measurements



Delay Measurements in WDM

n Delay is due to:� Electrical components � Optical components

n Delay averages 60 ns for the 1310 and 1550 nmn Optical delay is approximately 50 ns

Delay in WDM

0.0E+00

2.0E-08

4.0E-08

6.0E-08

8.0E-08

1.0E-07

1.2E-07

1.4E-07

1.6E-07

1.8E-07

2.0E-07

0 200 400 600 800 1000 1200 1400

Frequency(MHz)

Del

ay(s

)

Delay 1310nm

Delay 1550nm

10 ns of electrical delay is very negligible and ensures low phase distortion



CNR and SNR Test



CNR and SNR Test Setup

n CNR and SNR measured with the spectrum analyzern FM and AM on 1310 nm and 1550 nm n Network Analyzer used to enable analog traffic on the second channel


8554B


8554B



NETWORK ANALYZER

Agilent 8712ET

NETWORK ANALYZER

Agilent 8712ET









WDM WDM

fiber

WDM WDM



SNR Test Results

n SNR for both AM and FM for the 1310 nm channel averages 55 dB n SNR for both AM and FM the 1550 nm channel is around 40 dB

SNR in WDM

20

30

40

50

60

70

80

90

100

100 200 300 400 500 600 700 800 900 1000

Frequency (MHz)

SNR

(dB)

SNR for AM in 1310nm

SNR for FM in 1310 nmSNR for AM in 1550 nm

SNR for FM in 1550 nm

nLiterature survey shows SNR of 57 dB for AM in 1310 nm fibernSNR of 30 dB is a good FM radio reception and CD quality audio is 98 dB



CNR Test Results

CNR in WDM

20

30

40

50

60

70

80

90

100

100 200 300 400 500 600 700 800 900 1000

Frequency (MHz)

CNR

(dB)

CNR 1330 nm

CNR 1550 nm

n CNR for the 1310 nm channel averages 65 dB n SNR for the 1550 nm channel is 52 dB

Literature survey shows CNR of 60 dB for AM in 1310 nm fiber



Signal Quality Test



Signal Quality Test Setup

n Signal Quality measured with the digital oscilloscopen Input and Output AM and FM measuredn Network Analyzer used to enable analog traffic on the second channel

DIGITALOSCILLOSCOPE

TEKTRONIXTDS 784C

DIGITALOSCILLOSCOPE

TEKTRONIXTDS 784C



NETWORK ANALYZER

Agilent 8712ET

NETWORK ANALYZER

Agilent 8712ET









WDM WDM

fiber



AM Signal Quality Results

n AM modulation� Carrier: 2 MHz � Modulating signal: 200

KHz � Modulation Index:30%

A M In p u t a t 2 M H z

-8

-6

-4

-2

0

2

4

6

8

- 1 . 0 E - 0 5 - 5 . 0 E - 0 6 0 .0 E + 0 0 5 .0 E - 0 6 1 .0 E - 0 5

T im e ( s )

Am

plit

ud

e (V

)

A M O u tp u t a t 2 M H z

- 0 . 0 5

- 0 . 0 4

- 0 . 0 3

- 0 . 0 2

- 0 . 0 1

0

0 . 0 1

0 . 0 2

0 . 0 3

0 . 0 4

0 . 0 5

- 1 . 0 E - 0 5 - 5 . 0 E - 0 6 0 .0 E + 0 0 5 . 0 E - 0 6 1 . 0 E - 0 5

T im e ( s )

Am

plit

ud

e (V

)

n High signal quality of the AM signal is preserved in the output waveform.

n Output shows very little distortion, which is numerically measured and presented in the Distortion Test



FM Signal Quality Results

FM input for 100MHz

-6

-4

-2

0

2

4

6

-0.0005 -0.0003 -0.0001 0.0001 0.0003 0.0005

Time (s)

Ampli

tude

(V)

FM output at 100 MHz

-0.025

-0.02

-0.015

-0.01

-0.005

0

0.005

0.01

0.015

0.02

0.025

-0.0005 -0.0003 -0.0001 0.0001 0.0003 0.0005

Time (s)

Ampli

tude

(V)

n FM modulation� Carrier: 100 MHz � Modulating signal: 1000

Hz � Deviation:20 KHz

n High signal quality of the FM signal is preserved in the output waveform.

n Output shows very little distortion, which is numerically measured and presented in the Distortion Test



Distortion Test



Power Spectrum of a Modulated Signal

n The peak is the carrier and smaller peaks are the sidebands.



Distortion Basics

n a0: peak of the fundamental frequencyn a1: first harmonicn a2: second harmonicn a3: third harmonic

%100*(%)0

23

22

21

aaaa

THD++

=



Distortion Test Setup


8554B


8554B



NETWORK ANALYZER

Agilent 8712ET

NETWORK ANALYZER

Agilent 8712ET









WDM WDM

fiber

WDM WDM



Input Carrier Distortion Results

n Input carrier distortion generated by RF signal generatorn Input carrier distortion ranges between 0 and 0.2 %

I n p u t C a r r i e r D is t o r t i o n

0 . 0 0

0 . 0 5

0 . 1 0

0 . 1 5

0 . 2 0

0 . 2 5

0 . 3 0

1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0 9 0 0 1 0 0 0

F r e q u e n c y ( M H z )

TH

D (

%)

In p u t C a r r i e r T H D fo r F M

In p u t C a r r i e r T H D fo r A M

Spec on the RF signal generator for THD is less than 1%



Output Carrier Distortion Results

n Output carrier distortion ranges from 0 to 0.8 %

O u tp u t C a r r ie r D is to r t io n

0 . 0

0 . 1

0 . 2

0 . 3

0 . 4

0 . 5

0 . 6

0 . 7

0 . 8

0 . 9

1 . 0

1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0 9 0 0 1 0 0 0

F r e q u n c y (M H z )

TH

D (

%)

F M o n 1 5 5 0 n m

A M o n 1 5 5 0 n m

F M o n 1 3 1 0 n m

A M o n 1 3 1 0 n m

nThe output carrier distortion is very low (less than 1%)



Input Signal Distortion

Input Signal Distortion

0.0

0.5

1.0

1.5

2.0

2.5

3.0

100 200 300 400 500 600 700 800 900 1000

Frequency( MHz)

TH

D (

%)

Input S ignal THD for FM

Input S ignal THD for AM

n Input signal distortion generated by external modulator of RF signal generatorn Input carrier distortion ranges between 0 and 2 %



Output Signal Distortion

n Output distortion level for the modulating signal ranges from 0 to 7%

Output Signal Distortion

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

100 200 300 400 500 600 700 800 900 1000

Frequency (MHz)

THD

(%)

FM on 1550 nm

AM on 1550 nm

FM on 1310 nm

AM on 1310 nm

Distortion is due to the high frequency range of operation and external modulation



Laser Spectrum Test



Laser Spectrum Test Setup

n Laser quality in the optical transmitters was measured with the optical spectrum analyzer

OPTICALSPECTRUM ANALYZERHP 71450B

OPTICALSPECTRUM ANALYZERHP 71450B



NETWORK ANALYZER

Agilent 8712ET

NETWORK ANALYZER

Agilent 8712ET







Laser Spectrum Test Results

n 1310 nm shows peak wavelength at 1311 nm with narrow bandwidth of 1 nm

n 1550 nm shows peak wavelength at 1543 nm with narrow bandwidth of 1.5 nm

1310 nm 1550 nm

There is no overlap in the laser bandwidths since they are very narrow, which ensures no cross talk, no interference and no leakage.



Video Test



Video Test Setup

n Video Tester provides a baseband test video signal to the Impathn The video signal goes through FDM and is output on a 1310 fiber in the Impathn Network Analyzer used as analog traffic on the second channel

VIDEO TESTERVIDEOTEK

VSG 21

VIDEO TESTERVIDEOTEK

VSG 21

NETWORK ANALYZER

Agilent 8712ET

NETWORK ANALYZER

Agilent 8712ET

TX IMPATH1310 nm

TX IMPATH1310 nm



TX IMPATH1310 nm

TX IMPATH1310 nm



WDM WDM

DIGITALOSCILLOSCOPE

TEKTRONIXTDS 784C

DIGITALOSCILLOSCOPE

TEKTRONIXTDS 784C

fiber



Test Signal Picture Quality

n No visible distortion of the output picture quality

Input Output



Camera Picture Quality

n Camera snapshot input and output show identical qualityn No distortion in the output picture

Input Output



Input and Output Waveform Comparison

n Output amplification due to Impath TX

n Almost no distortion in the output waveform

Input for Multiburst Test Video Signal

-0.002

0

0.002

0.004

0.006

-3.0E-05 -2.0E-05 -1.0E-05 0.0E+00 1.0E-05 2.0E-05 3.0E-05 4.0E-05 5.0E-05

Time (s)

Am

plit

ud

e (V

)Output for Muliburst Video Test Signal

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

-4.0E-05 -3.0E-05 -2.0E-05 -1.0E-05 0.0E+00 1.0E-05 2.0E-05 3.0E-05 4.0E-05 5.0E-05

Time (s)

Am

plit

ud

e (V

)Cross correlation of the input and output =0.9984



Input and Output Streaming Video

n Input Video Stream

n Output Video Stream

n Output video was the same quality as the input video from a human eye perspective.



Bit Error Rate Test (BERT)



BERT Setup

n BERT Tester supplies pseudo-random sequence to GDI TX via RS 232 port

n GDI TX converts the pseudo-random sequence into FSK modulated signal

n Network Analyzer provides analog traffic on the second channel

BERT TESTERDCB BT-1

BERT TESTERDCB BT-1

NETWORK ANALYZER

Agilent 8712ET

NETWORK ANALYZER

Agilent 8712ET

GDI FLD2SATX 1310 nm

GDI FLD2SATX 1310 nm



GDI FLD2SARX 1310 nm

GDI FLD2SARX 1310 nm



WDM WDM

fiber



BERT Experimental Setup



BERT Results

n Asynchronous BERT output:� Messages: ú ABC printable char.ú All 256 hex for 8 bit char.

(00 to FF)ú A “Quick brown fox” (QFB)

messageú 63,511, and 2047 bit random

sequence� Transmission speed:ú 9600 bpsú 14400ú 19200ú 38400

� Running Time: 30 min.



BERT Test Scenarios

19200 bps ABC

14400 bps QBF

9600 bps 00 to FF

38400 bps 511 seq.



BERT Test Remarks

n No bits received in error in all possible tests

n No interference between the digital and the analog channels

n No power loss on the analog side due to the digital transmission



Conclusions

n Measurements carried out on our WDM testbed.� Power Test� Delay Measurements� SNR Test� CNR Test� Signal Quality Test� Distortion Test� Laser Spectrum Test� Video Test� BERT

n Publications: � 1 conference paper accepted at DASC 2002 conference.� One journal paper planned.



n Acknowledgements� NASA Glenn Research Center� Dr. Hung Nguyen and Dr. Duc Ngo - NASA Glenn� Ronald LaSpisa, Univ. of Oklahoma.

n Further InformationMohammed [email protected], (405) 325 8077

n These slides are available at www.cs.ou.edu/~atiq

infrared avionics signal distribution: (phase 2

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