1 Introduction For new applications : fibre-radio systems optically supplied microwave antennas...
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Transcript of 1 Introduction For new applications : fibre-radio systems optically supplied microwave antennas...
1
Introduction
For new applications :• fibre-radio systems• optically supplied microwave antennas
There is a need for microwave photonic functions
Emitters Optical switchingmatrixes
Receiversmicrowave microwave
optical fibre optical fibre
2
Axially coupled lasers : fabrication
At IEMN and Tempere University of Technology
Perot-Fabry lasers
Substrate InP SI
Active layer (MQW)
InP p+
GaInAs GaInAs
InP n+
InP p+ InP p+
Substrate InP SI
Active layer (MQW)
InP p+
GaInAs GaInAs
InP n+
Fabrication on semi-insulating substrate Fabrication on N+ substrate
European TMR project
3
f = 11,4 GHz
Axially coupled lasers: microwave experiments
• optical generation of a microwavesignal (beating of the optical modesin a photodetector)• tuning of the frequency withbias currents
• observed on the frequency response
4
The Dual Mode Laser structure
It is a sampled grating DFB laser
Sampled grating structure
P+
N+
elementary sampled grating
10 µm 80 µm
N Contact
P Contact
710 µm long device: - 7 DFB sections (10µm)- 8 FP sections (80 µm)- 2 end DFB sections (40 µm)
It is also a DFB laser with a reduced coupling coefficient
5
Digital Optical Switch
No carrier injection
Carrier injection
BPM Modelling
A Y junction unbalanced by injection of carriers
6
Variation de la puissance du signal hyper à 9GHz en fonction du courant injecté dans le DOS
-120
-100
-80
-60
-40
-20
0
0 5 10 15 20 25 30 35 40
I (mA)
P (
dB
m)
branche éteinte
branche commutée
Département Hyperfréquences & Semiconducteurs
58 dB !
7Département Hyperfréquences & Semiconducteurs
mesure du bruit de phase - modulation 9 GHz
-60
-50
-40
-30
-20
-10
00,00E+00 2,00E+05 4,00E+05 6,00E+05 8,00E+05 1,00E+06 1,20E+06
fréquence relative
P
référence moyenne
commutation moyenne
8
High power photodiodes : possible solutions
1. Travelling-Wave Photodetector– Increased absorption volume– Electrodes = 50 microwave line– Optical and microwave velocity
matching
2. Uni Travelling Carrier Photodiode– Absorption in P+ GaInAs layer (no
field)– Transit of photogenerated electrons
by diffusion (base) and drift (collector)
9
P+ InP
N+ InP
N+ InP
N+ InP
N+ InP
N+ InP
nid GaInAsN+ GaInAsP
N+ GaInAsP
N+ GaInAsP
N+ GaInAsP
N+ GaInAsP
N+ GaInAsP
- Good coupling to the fiber
- One quaternary GaInAsP and
InP layers
- Specific waveguide half lens
New concept : diluted multimode waveguide
1.3 µmor
1.55 µm
10
TM mode, 1.55µmInjection at -7.5µm
Air
Substrate
GaInAs layer
TM mode, 1.55µmInjection at -5µm
Air
Substrate
GaInAs layer
Typical behaviour of the optimized multimode
diluted waveguide
Air
Substrate
Photodetector behaviour
Diluted multimode waveguide : optical behaviour
Vertical scales dilated
11
Experimental results
• Device fabricated at Opto+ (Alcatel)
• 11µm thick epitaxial structure (MOCVD)
• =1.55µm : Max Resp=1.06A/W• =1.30µm : Max Resp=0.86A/W• -1 dB misalign. tolerance = 6.5 µm• Influence of optical polarisation : lower than 0.1dB in all cases • Cut-off frequency > 3GHz @-3V
Work in progress to get millimeter wave devices
• High reliability
0 5 10 15 20 25 30 35 40Bias voltage (V)
10-12
10-11
10-10
10-09
10-08
10-07
10-06
Dar
k cu
rren
t (A
)
After
Before
200°C / -10V / 1030 hours
12
Résultats des transmissions 32-QAM
1km MMFle câble coaxial(référence)
le diagramme
de constellation
le diagramme
de l ’oeil
Département Hyperfréquences & Semiconducteurs
13
Réponses fréquencielles de MMF
fréquence, GHz
rép
on
se,
dB
>80% des fibres intra -bâtiment < 300m
-10
-8
-6
-4
-2
0
2
0 2 4 6 80 2 4 6 8
1km
500m
100m
2
0
-2
-4
-6
-8
-10
Département Hyperfréquences & Semiconducteurs