1. M. F. Chiang, Z. Ghassemlooy, Wai Pang Ng,
Simulation of an All-Optical 1  2 SMZ Switch with a High Contrast Ratio
M. F. Chiang, Z. Ghassemlooy, Wai Pang Ng,
and H. Le Minh
Optical Communication Research Group
Northumbria University, United Kingdom
M. F. Chiang

2. Contents Introduction Symmetric Mach-Zehnder (SMZ)
Optical inverter based on SMZ
All-Optical 1  2 SMZ Switch with a High Contrast Ratio
Simulation Results
Conclusions
M. F. Chiang

3. 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).
M. F. Chiang

4. Introduction All-Optical Switches
UNI
TOAD
Ref:
Ref: (Princeton)
SMZ
Ref: (Japan)
M. F. Chiang

5. Semiconductor Optical Amplifier (SOA)
Input signals
Injection current P
Input signals (light)
Carrier density &
SOA gain (XGM) N
SOA
SOA refractive index &
Induced phase (XPM)
M. F. Chiang

6. SMZ (Symmetric Mach-Zehnder)
Advantages:
narrow and square switching window
compact size
thermal stability and low power operation
Undesired signal
Drawback:
1. Low inter-output CR (< 10 dB) due to the problem of maintaining the same phase shift.
M. F. Chiang

7. Symmetric Mach-Zehnder (SMZ)
Case 1: Without CP (SMZ is balanced)
Case 1: Without CP (SMZ is balanced)
PC2
Output2
Output1
Coupler4
Coupler3
Coupler2
Coupler1
SOA2
SOA1
PBS
PC1
Pout,1(t)=S’’’(t)+S’’’(t+π/2+π/2)
S’’(t)
S’(t)
S’’’(t)
Pin(t)=S(t)
S’(t+π/2)
S’’’(t+π/2)
S’’(t+π/2)
Pout,2(t)=S’’’(t+π/2)+S’’’(t+π/2)
Signals emerge from output2
Case 2: With CP1 only (SMZ unbalanced)
Case 3: With both CP1&CP2
(SMZ is balanced again)
Case 2: With CP1 only (SMZ unbalanced)
CP1
Signals emerge form output1
PC2
Output2
Output1
Coupler4
Coupler3
Coupler2
Coupler1
SOA2
SOA1
PBS
PC1
S’’(t)
Pout,1(t)=S’’’(t + π)+S’’’(t+π/2+π/2 + π)
Pout,1(t)=S’’’(t + π)+S’’’(t+π/2+π/2) π
S’(t)
S’’’(t+ π)
Pin(t)=S(t)
CP2
S’’(t+π/2)
S’(t+π/2) π
S’’’(t+π/2+ π )
S’’’(t+π/2)
Pout,2(t)=S’’’(t+π/2 + π)+S’’’(t+π/2 + π)
Pout,2(t)=S’’’(t+π/2 + π)+S’’’(t+π/2)
Signals emerge from output2 again
M. F. Chiang PC 3 -
dB coupler
PBS

8. All-Optical 1  2 SMZ Switch with a High Contrast Ratio
low inter-output CR (< 10 dB)
Improved CR (> 32 dB)
CEM: clock extraction module
M. F. Chiang

9. All-optical inverter based on SMZ
SOA
Input (CLK) CP 1
(CLK) 2
(A)
Output (A bar) A
A bar 1
M. F. Chiang

10. Simulation Results-Simulation Parameter
Simulation Tool: Virtual Photonic Inc. (VPI)
TABLE I
SOA SIMULATION PARAMETER
TABLE II
SIGNAL AND CONTROL PULSES DEFAULT PARAMETERS
M. F. Chiang

11. Simulation Results-Time Waveforms
Input packets
Control pulse
Output1
Output2
Output waveforms observed at the proposed 12 switch
M. F. Chiang

12. Simulation Results-Time Waveforms
CR (< 10 dB)
The improved
CR (> 30 dB)
Output CR ratio observed at the proposed 12 switch
M. F. Chiang

13. The contrast ratio (CR) against the input packet power
Simulation Results-
The contrast ratio (CR) against the input packet power
M. F. Chiang

14. Conclusion
In this paper, the advantages and drawbacks of SMZs were introduced.
The principle of the proposed all-optical 1  2 SMZ switch with a high contrast ratio was explained.
It was shown that a high Inter-output CR ( > 32 dB) was achieved over a wide range of input packet power (12 dB).
The proposed 12 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.
M. F. Chiang

15. Special Thanks for Prof. Fary Ghassemlooy Dr. Wai Pang Ng
Mr. Hoa Le Minh
All colleagues in NCRL
&
Your Attention
M. F. Chiang

16. Thank You !
Question, please ?
M. F. Chiang