Optimisation of the Key SOA Parameters for Amplification and Switching
description
Transcript of Optimisation of the Key SOA Parameters for Amplification and Switching
Client Network
Client Network
Low-speed packet
Low-speed packet
High-speed packet
Core Network
Proposed core optical router
Source / target node
All-optical router
Buffer
Input
Output
Main modules Optional modules
Packet
Delay unit
Clock Extraction
Header Extraction
Header Recognition
Look-up Routing Table
Reconfiguration
Optical Switching Unit
Controlling Contention
Signal Processing (2R, 3R, equalization)
Splitter
Symetric Mach-Zehnder Interferometer(SMZI)
CP1
SOA1
SOA2 CP2
Input Output 1
Output 2
To design a bi-directional SMZ and implement it in the router to reduce components, time and cost.
To optimize the performance of the SOA to be adapted for bi-directional operation.To overcome the slow time recovery of the SOA gain.To propose a bi-directional model for the SOA.To design a bi-directional model for the SMZ and implement it in the proposed router.
Injection current (I)
L
Input facet of active region Input signals
Output signals
Output facet
H
w
Energy gap
E2 (conduction band)
E1 (valence band)
Stimulated absorption
Stimulated emission
Spontaneous emission
Hole Electron (carrier)
Photon Inducing photon
Stimulated photon
Input optical signal (photon)
Output amplified optical signal
segment1
segment2
………….. …………….
segment5
t=0 t=l/vgg
t=L/vg
input signal
output signal
Ni
N(1)
N(5)
0 1 2 3 4 5 6
x 10-9
0
0.2
0.4
0.6
0.8
1
Time (s)
Nor
mal
ized
gai
n • Normalised gain response of the SOA with no input signal.
• Normalised gain response of the SOA due to the injection of a short input pulse.
0 1 2 3 4 5 6
x 10-9
0
0.2
0.4
0.6
0.8
1
Time (s)
Nor
mal
ized
gai
n
Injection of the input pulse
• Normalised gain response of the SOA due to the injection of a continuous input signal.
0 1 2 3 4 5 6
x 10-9
0
0.2
0.4
0.6
0.8
1
Time (s)
Nor
mal
ized
gai
n
Injection of the continuous wave
Saturation gain
Condition: The signal should not be affected by the SOA
nonlinear effect (i.e: SOA gain depletion should not reach saturation value).
Note: The reference is the saturation value for a 1mW
continuous input signal.
• The output gain corresponding to the input power at different bias currents.
•Reference saturation gain:
• at I=150mA 66• at I=200mA 96• at I=250mA 1270 1 2 3 4 5 6 7 8 9 10
0
500
1000
1500
2000
2500
Input power (mW)
Out
put
gain
I=250mA
I= 200mA
I=150mA
• Condition:– The signal should be affected by the nonlinearity of
the SOA and achieve a 180o phase shift for the deconstructive interference. (i.e: SOA gain depletion of a control pulse (CP) should reach the gain saturation value).
• Note:– A control pulse (CP) is required to be launched to
the SOA, then the input signal should be injected in order to achieve the 180o phase shift.
• The saturation control pulse (CP) for the corresponding input power at different bias currents.
1 2 3 4 5 6 7 8 9 102
4
6
8
10
12
14
16
18
20
Input power (mW)
CP
inpu
t po
wer
(m
W)
I=150 mA
I=200mA
I=250 mA
• SOA gain dependence on the bias current.
0 50 100 150 200 25010
15
20
25
30
35
40
Bias current (mA)
SO
A g
ain
(dB
)
• Normalised gain response of the SOA due to the injection of a short input pulse.
0 1 2 3 4 5 6
x 10-9
0
0.2
0.4
0.6
0.8
1
Time (s)
Nor
mal
ised
gai
n
Recovery time
• Normalised gain response of the SOA due to partial increase of the bias current.
0 1 2 3 4 5 6
x 10-9
0
0.2
0.4
0.6
0.8
1
Time (s)
Nor
mal
ised
gai
n
segment1
segment2
………….. …………….
segment5
t=0 t=l/vgg
t=L/vg
Propagating input signal
Propagating output signal
Partial increase of bias current
• SOA gain recovery due to the additional of different bias currents.
0 10 20 30 40 50 60 70 80 900
100
200
300
400
500
600
700
800
900
Additional bias current (mA)
Rec
over
y tim
e of
the
SO
A g
ain
(ps)
100% recovery
99% recovery
95% recovery
Recovery time=37ps
Improvement of:86% for 95% recovery90% for 99% recovery84% for 100% recovery
• SOA bit rate due to the additional bias current.
0 10 20 30 40 50 60 70 80 900
5
10
15
20
25
30
Additional bias current (mA)
SO
A b
it ra
te (
Gb/
s)
100% recovery
99% recovery
95% recovery
SOA bit rate=27.027 Gbps
Improvement of:7.5 times at 95% recovery
• Time needed to apply additional bias current.
10 20 30 40 50 60 70 80 9020
40
60
80
100
120
140
160
Additional bias current (mA)
Tim
e ne
eded
to a
pply
add
ition
al b
ias
curre
nt (p
s)
Time needed :35ps for 90mA154ps for 10mA
segment1
segment2
………….. …………….
segment5
t=0 t=l/vgg
t=L/vg
Propagating input signal
Propagating output signal
Co-propagating input signal
Co-propagating output signal
Uni-directional SMZ
Bi-directional SMZ
Practical work on the SMZ.The replacement of active components in the router by passive components (FBGs) such as demultiplexing, add/drop devices, filtering, and switching .Solving the contention resolution problem using a novel multiplexing solution.
The SOA is modelled using a segmentation method.The effect of input parameters on the gain and carrier density response of an SOA is presented.Optimum performance conditions are investigated in which the SOA can be used as a standalone amplifier and in a SMZ switch.The dependence on of the SOA on the bias current is presented.
Results show an acceleration in the gain recovery time due to partially increasing the bias current applied to the SOA. SOA gain recovery time and bit rate corresponding to the additional bias current is investigated.
Optical Communication Research Group
Northumbria Communication Research Laboratory
School of Computing, Engineering, Information and Sciences
Ultra-fast all-optical WDM router based on bidirectional SMZs and FBGs.
Submitted Accepted/Completed Rejected/Delayed
Conference/ Journal Abstract Full Paper
STCEII (Msc) 2006 Published
ICC 2008 (co-author) Published
ICEE 2008 (co-author) Published
SENACITEL 2008(co-author) Accepted
PGNET 2008 Published
ICON-MW 2008 Accepted Submitted
ELECTRONICS LETTER Submitted to supervisor