Paulo Sérgio de Brito André *
Departamento de Física da Universidade de Aveiro
Instituto de Telecomunicações pólo de Aveiro
* Bolseiro de doutoramento da FCT (PRAXIS XXI/BD/17227/98), projecto DAWN.
4 70 km Point-to-point WDM system, with 3 channels
200 GHz spaced, modulated at 2.48832 Gbit/s.
4 Crosstalk Study.
4 Fibre Bragg Gratings (FBG).
4 Optical Add - Drop Multiplexer (OADM) based
on Fibre Bragg Gratings (FBG)
4 Tuning of FBG
4 Tunable OADM
1549.32 nm
1550.92 nm
1552.52 nm
0
Com recuperador de Relógio
Sem recuperador de Relógio
-1
-2
-3
Log (BER)
-4
-5
-6
-7
-9
BER=10
-8
-9
-10
Limite da medida
-11
-12
-13
-17
-16
-15
-14
-13
-12
-11
Potência (dBm)
-10
-9
-8
-7
Single Channel
-2
-3
75 Km
Directo
-4
-5
Log(BER)
-6
-7
-8
BER=10
-9
-9
-10
-11
Limite da medida
-12
-13
-11.0
-10.5
-10.0
-9.5
-9.0
-8.5
Potência (dBm)
-8.0
-7.5
-7.0
Multi-Channel, Central wavelength
-2
75 Km WDM
75 km Monocanal
Directo
-3
-4
-5
Log (BER)
-6
-7
-8
BER=10
-9
-9
-10
-11
Limite da medida
-12
-13
-11.0
-10.5
-10.0
-9.5
-9.0
-8.5
Potência (dBm)
-8.0
-7.5
-7.0
Optical Spectra on the system
-10
0
Potência Óptica (dBm)
-30
-40
-50
-60
-20
-30
-40
-70
1.535
-10
1.540
1.545
1.550
1.555
1.560
1.565
1.535
1.540
Comprimento de Onda ( µm )
1.545
1.550
1.555
1.560
1.565
Comprimento de Onda (υm)
0
-10
After MUX
After 2 EDFA
After DEMUX
Potência Óptica (dBm)
Potência òptica (dBm)
-20
-20
-30
-40
-50
-60
-70
- 28 dB XT
1.535
1.540
1.545
1.550
1.555
Comprimento de Onda (υm )
1.560
1.565
Bit Error Rate as function of the decision level
-1
-2
-3
-4
Log (BER)
-5
-6
-7
-8
BER=10
-9
-9
-10
-11
Limite da medida
-12
-13
-360
-355
-350
-345
330
335
Nível de Decisão (mV)
340
345
350
Data after propagation on 70 km of fiber
Eye diagram without
signal reformatting
Eye diagram with
signal reformatting
Data
Clock
4 Another technical key issue on a wavelength reused OADM
network is how to reduce the crosstalk, which severely degrade the
system performance.
4 Heterodyne Crosstalk, due to low rejection of the FBG
between adjacent channels and the central wavelength.
Pp
= − 10 ⋅ log (1 −
X)
4 Homodyne Crosstalk, due to reflectivity of the FBG to the
central wavelength (limit the number of nodes of a network).
Pp = − 10 ⋅ log (1 − Q ⋅ X )
2
Q - SNR
Homodyne
Crosstalk
Heterodyne
Crosstalk
12
10
Penalidade de Potência (dB)
Penalidade de Potência (dB)
10
Simulação no PTDS
Experimental
Analítico
Simulação no PTDS
Experimental
Analítico
8
6
4
2
8
6
4
2
0
0
-34
-32
-30
-28
-26
-24
-22
-20
-18
-16
-40
-14
-35
-30
-25
-20
-15
-10
-5
0
Ratio de Diafonia (dB)
Ratio de Diafonia (dB)
-1
-2
Homodyne Crosstalk
Diafonia Homodina
Diafonia Heterodina
-3
Heterodyne Crosstalk
BER
Log (BER)
-4
-5
-6
-7
-8
-9
-10
-40
-35
-30
-25
-20
-15
-10
Ratio de Diafonia (dB)
-5
0
5
5
Heterodyne Crosstalk
- 40 dB
- 4 dB
Diafonia Homodina
- 40 dB
- 15 dB
0 dB
-8 dB
-5
1550.92 nm
- 0.5 dB Bandwidth
0.256 nm
- 1 dB Bandwidth
0.532 nm
- 3 dB Bandwidth
0.748 nm
- 20 dB Bandwidth
1.388 nm
Insertion Loss at
λ
C
Reflectivity for adjacent Channels
Reflectivity at
λ
C
30.7 dB
-10
-15
Reflectividade (dB)
Central Wavelength
-20
28.3 dB
-25
-30
-35
28.3 dB
99.99 %
-40
-45
1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556
Comprimento de Onda (nm)
Optimised for the ITU 200 GHz frequency grid, λc = 193.3 THz
4 3 channels at 193.1, 193.3 and 193.5 THz
4 Externally modulated at 2.48832 Gbit/s (STM -16)
4 Transmission over 70 km of fibre G.652
-10
0
-5
193.3 THz
193.5 THz
193.1 THz
-20
-15
Potência Óptica (dBm)
Potência Óptica (dBm)
-10
In
-20
-25
-30
Removed
28.1 dB
-30
-40
-50
-60
-35
-70
-40
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
-80
1545
1556
1546
1547
Comprimento de Onda (nm)
1550
1551
1552
1553
1554
1555
1556
1554
1555
1556
-15
Pass
-20
Potência Óptica (dBm)
Potência Óptica (dBm)
1549
Comprimento de Onda (nm)
-10
-20
1548
30.7 dB
-30
-40
-50
Out
-25
-30
-35
-40
-45
-50
-60
1545
1546
1547
1548
1549
1550
1551
1552
1553
Comprimento de Onda (nm)
1554
1555
1556
-55
1545
1546
1547
1548
1549
1550
1551
1552
1553
Comprimento de Onda (nm)
Removed Channel
Added Channel
-2
-2
Directo
Canal removido com 50 km de fibra
50 km de fibra
-3
Directo
Canal adicionado com 20 km de fibra
20 km de fibra
-3
-4
-4
-5
Log (BER)
Log (BER)
-5
-6
-7
-9
BER=10
-8
-7
-8
-9
-10
Limite da Medida
-11
-11
-12
-12
-10.0
BER=10
-9
-9
-10
-6
-9.5
-9.0
-8.5
-8.0
-7.5
Potência (dBm)
-7.0
-6.5
-6.0
-10.0
Limite da Medida
-9.5
-9.0
-8.5
-8.0
-7.5
Potência (dBm)
Pp=0.08 dB
Pp=0.18 dB
Ppt=0.01 dB
Ppt=0.14 dB
-7.0
-6.5
-6.0
Espaçamento entre Canais (GHz)
50
75
100
125
150
175
200
225
5
Penalidade de Potência (dB)
- 3 dB BW
4
- 20 dB BW
3
2
- 1 dB BW
1
0
0.4
0.6
0.8
1.0
1.2
1.4
Espaçamento entre Canais (nm)
1.6
1.8
Desintonia (GHz)
-50
8
-40
-30
-20
0
10
20
30
40
50
- 0.5 dB BW
7
Penalidade de Potência (dB)
-10
6
5
4
3
2
1
0
-0.4
-0.3
-0.2
-0.1
0.0
0.1
Desintonia (nm)
0.2
0.3
0.4
4 A wavelength tunable OADM, giving access to all the
wavelengths of the WDM signals provides more flexibility to
satisfy reconfiguration requirements and to enhance network
protection.
4 The wavelength tuning capacities of the OADM are related
with the FBG capacities to shift their central reflection
wavelength.
4 To shift the Bragg grating central wavelength peak there are
two main methods: by modifying the fibre refractive index or by
changing the grating period. These variations can be induced
thermally or/and by mechanical stress.
lB =
2 ⋅ neff ⋅ Λ
4 Mechanical stress: Large tuning range ( > 36 nm), high tuning
speed ( < 10 ms/nm), low reproducibility and reversibility.
4 Thermal: High reproducibility and reversibility, built-in
temperature compensation, low tuning range ( < 1 nm) and low
tuning speed ( > 10 s/nm).
4 We present a hybrid method based on a thermal-stress
thermally enhanced actuation on a FBG .
∆lB

= 2 ⋅  Λ ⋅

dneff
dl
+
neff
dΛ
dl

 ⋅∆l +



2 ⋅  Λ ⋅

dneff
dT
+
neff
dΛ
dT

 ⋅ ∆T


∆ l BT = l B ⋅ (1 −
pe ) ⋅ e z
e Z = a CTE ⋅ ∆ T
∆ l = l B ⋅ [(1 −
∆ l BT = l B ⋅ (a Λ + a n ) ⋅ ∆ T
Deformação axial (stress)
pe ) ⋅ a CTE + (a Λ + a n )]⋅ ∆ T ≈ l B ⋅ 26.31⋅ 10− 6 ⋅ ∆ T
KTS = 41.1 pm / ºC
Aluminium Coefficient of thermal expansion α CTE = 22.0 x 10-6 ºC-1
Silica Photo elastic coefficient pe = 0.22
Sílica Thermal expansion coefficient α Λ = 0.55 x 10-6
Sílica Thermal optic coefficient α n = 8.6 x 10-6
Comprimento de onda de reflexão (nm)
1550.0
KTS = 44.3 pm / ºC
Data
Fit
1549.6
1549.2
1548.8
1548.4
1548.0
1547.6
20
25
30
35
40
45
Temperatura (º C)
Potência Reflectida (dBm)
-5
T
T
T
T
T
T
T
T
-10
-15
=
=
=
=
=
=
=
=
22
25
30
35
40
45
50
55
º
º
º
º
º
º
º
º
C
C
C
C
C
C
C
C
-20
-25
1547
1548
1549
Comprimento de onda (nm)
1550
1551
50
55
60
65
0.70
Largura de Banda (nm)
0.60
Largura de banda a - 20 dB
Largura de banda a - 3 dB
Reflectividade
-1.8
-2.0
0.55
-2.2
0.50
-2.4
0.45
-2.6
0.40
-2.8
0.35
-3.0
0.30
-3.2
0.25
-3.4
0.20
-3.6
0.15
-3.8
0.10
-4.0
1547.8 1548.0 1548.2 1548.4 1548.6 1548.8 1549.0 1549.2 1549.4 1549.6
Comprimento de Onda (nm)
Reflectividade (dB)
0.65
-1.6
-10
-2
-20
-40
-50
-60
-70
-80
1546
1547
1548
1549
1550
1551
1552
Potência Óptica (dBm)
Comprimento de Onda (nm)
100 GHz
-8
-10
-12
-14
-16
-10
-18
-20
-20
-30
-22
1547.0
1547.5
-40
1548.0
1548.5
1549.0
1549.5
Comprimento de Onda (nm)
-50
-60
-5
-70
-80
1546
1547
1548
1549
1550
1551
-10
1552
Potência Óptics (dBm)
Comprimento de Onda (nm)
-10
-20
Potência Óptica (dBm)
30 º C
40 º C
50 º C
-6
Reflectividade (dB)
Potência Óptica (dBm)
-4
-30
-30
-40
-50
-15
-20
-25
-30
-35
-60
-40
-70
-80
1546
1546
1547
1548
1549
1550
Comprimento de Onda (nm)
1551
1547
1548
1549
1550
1552
Comprimento de onda (nm)
1551
1552
1550.0
4 We have reported an OADM solution for DWDM systems
using a FBG.
4 The OADM performance was demonstrate in a 200 GHz, 3
channels WDM system, working at STM-16 bitrate.
4 The OADM show a good performance with respect to channel
spacing and crosstalk.
4 We also reported a tunable OADM based on a thermal - stress
thermal enhanced tunable FBG.