m. f. chiang 1, z. ghassemlooy 1, w. p. ng 1, and h. le minh 2 1. optical communications research...
TRANSCRIPT
M. F. Chiang1, Z. Ghassemlooy1, W. P. Ng1, and H. Le Minh2
1. Optical Communications Research Group
School of Computing, Engineering and Information Sciences
Northumbria University, Newcastle upon Tyne, UK2. Department of Engineering Science, University of Oxford, UK
http://soe.unn.ac.uk/ocr/
Simulation of an All-Optical 12 SMZ Switch with a High Contrast Ratio
Contents
Introduction
Symmetric Mach-Zehnder (SMZ)
Optical inverter based on SMZ
All-Optical 12 SMZ Switch with a High Contrast Ratio
Simulation Results
Conclusions
Introduction- Research Aim
There is a growing demand for all optical switches and router at very high speed, to avoid the bottleneck imposed by the electronic switches.
All-optical switches, such as SMZs are the key components adopted for switching and routing due to their ultrafast switching time (pico- to sub-picoseconds). However, SMZs have low inter-output CR (< 10 dB).
It is essential to have a high inter-output CR switch for lower value of output crosstalk (CXT).
Ref: www.iqe.ethz.ch/photonics
SMZ SMZ
UNIUNI TOAD TOAD
Ref: (Princeton)
Ref: (Japan)
Introduction All-Optical Switches
Semiconductor Optical Amplifier (SOA)
Input signals (light)
Carrier density &
SOA gain (XGM)
SOA refractive index &
Induced phase (XPM)
Input signals
P
N
Injection current
SOA
Advantages: 1. narrow and square switching window2. compact size3. thermal stability and low power operation
Drawback: 1. low inter-output CR (< 10 dB) due to the problem of maintaining the same
phase shift.
Undesired signal
Symmetric Mach-Zehnder (SMZ)
S’(t+π/2)
S’(t)
S’’(t)
S’’’(t)
S’’’(t+π/2)
Pout,1(t)=S’’’(t)+S’’’(t+π/2+π/2)
Pout,2(t)=S’’’(t+π/2)+S’’’(t+π/2)
Pin(t)=S(t)
Signals emerge from output2
S’(t+π/2)
S’(t)
S’’(t)
S’’(t+π/2)
S’’’(t+ π)
S’’’(t+π/2)
Pout,1(t)=S’’’(t + π)+S’’’(t+π/2+π/2)
Pout,2(t)=S’’’(t+π/2 + π)+S’’’(t+π/2)
Pin(t)=S(t)
Signals emerge form output1CP1
π
Case 1: Without CP (SMZ is balanced)
Case 2: With CP1 only (SMZ unbalanced) Case 3: With both CP1&CP2
(SMZ is balanced again)
CP2π
Pout,2(t)=S’’’(t+π/2 + π)+S’’’(t+π/2 + π)
Pout,1(t)=S’’’(t + π)+S’’’(t+π/2+π/2 + π)
Signals emerge from output2 again
S’’’(t+π/2+ π )
Symmetric Mach-Zehnder (SMZ)Case 1: Without CP (SMZ is balanced)
Case 2: With CP1 only (SMZ unbalanced)
PC2
Output2
Output1
Coupler4
Coupler3
Coupler2
Coupler1
SOA2
SOA1 PBS
PC1
PBSS’’(t+π/2)
PC2
Output2
Output1
Coupler4
Coupler3
Coupler2
Coupler1
SOA2
SOA1 PBS
PC1
PBS
PC 3-dB coupler PBS
Inter-output Contrast Ratio (CR) of a 12 Switch
The inter-output CR of a 1×2 switch is defined as the power
ratio between the switched and non-switched signals at
outputsij
where i, j = 1 or 2.
Typically the value of inter-output CR observed at the SMZ
output 2 (CR21) is less than 10 dB.
Here we propose a 1×2 switch utilizing an optical inverter
that offers improved CR21.
All-Optical 12 SMZ Switch with a High Contrast Ratio
SMZ1
SMZ2
inverter CP
CP
CP
Output1 (SMZ1_op1) Input packets
CLK CEM
SMZ1_op2
Output2 (SMZ2_op1)
CEM: clock extraction module
low inter-output CR (< 10 dB)
Improved CR (> 32 dB)
All-optical Inverter Based on SMZ
A A bar
1 0
0 1
SOA
SOA
Input (CLK)
CP 1 (CLK)
CP 2 (A)
Output (A bar)
Simulation Results-Simulation Parameter
Simulation Tool: Virtual Photonic Inc. (VPI)
Parameter and description Value
Inject current 0.15 A
Length 500 x 10-6 m
Width 3 x 10-6 m
Height 80 x 10-9 m
Confinement factor 0.15
Differential gain 2.78 x 10-20 m2
Carrier density at transparency 1.4 x 1024 m-3
Initial carrier density 3 x 1024 m-3
Linewidth enhancement factor 5
Recombine constant A 1.43 x 108 s-1
Recombine constant B 1 x 10-16 m3s-1
Recombine constant C 3 x 10-41 m6s-1
TABLE ISOA SIMULATION PARAMETER
TABLE IISIGNAL AND CONTROL PULSES
DEFAULT PARAMETERS
Parameter and description Value
Data packet bit rate – 1/Tb 160 Gb/s
Packet payload length 1 bytes (8 bits)
Packet guard time 1.5 ns
Wavelength of data packet 1554 nm
Data & control pulse widths – FWHM 2 ps
Bit duration Tb 6.25 ps
Control signal (CP) power 40 mW
Simulation Results-Time Waveforms
Output waveforms observed at the proposed 12 switch
Input packets
Control pulse
Output1
Output2
Simulation Results-Time Waveforms
Output CR ratio observed at the proposed 12 switch
CR (< 10 dB)
The improvedCR (> 30 dB)
Simulation Results-The contrast ratio (CR) against the
input packet power
0
5
10
15
20
25
30
35
40
45
50
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Input packet pow er (dBm)
CR
(dB
) CR of CP
CR at output1
CR at output2
CP
Simulation Results-The contrast ratio (CR) against the
control pulse power
7
12
17
22
27
32
37
42
47
13 14 15 16 17 18 19
Control pulse power (dBm)
CR
(dB
) CR of abar
CR at output1
CR at output2
CP
Conclusion
The advantages and drawbacks of SMZs were introduced.
The principle of the proposed all-optical 12 SMZ switch with a high contrast ratio was explained.
By carefully selecting the power of the control pulses, inter-output CR of > 32 dB was achieved over a wide range of input packet power (12 dB).
The proposed 12 switch offered an improvement in the inter-output CR of ~ 25 dB in comparison with a single SMZ switch. The proposed switch could potentially be adopted for high-speed signal processing and packet routing in all-optical networks.
Special ThanksSpecial Thanks for
Prof. Z. Ghassemlooy
Dr. Wai Pang Ng
Dr. Hoa Le Minh
All colleagues in NCRLab
&
Your Attention