M. F. Chiang 1, Z. Ghassemlooy 1, W. P. Ng 1, and H. Le Minh 2 1. Optical Communications Research Group School of Computing, Engineering and Information Sciences Northumbria University, Newcastle upon Tyne, UK 2. Department of Engineering Science, University of Oxford, UK Simulation of an All-Optical 1  2 SMZ Switch with a High Contrast Ratio

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

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: SMZ UNI TOAD Ref: (Princeton) Ref: (Japan) Introduction All-Optical Switches

Symmetric Mach-Zehnder (SMZ)

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 window 2.compact size 3.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) P out,1 (t)=S’’’(t)+S’’’(t+π/2+π/2) P out,2 (t)=S’’’(t+π/2)+S’’’(t+π/2) P in (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) P out,1 (t)=S’’’(t + π)+S’’’(t+π/2+π/2) P out,2 (t)=S’’’(t+π/2 + π)+S’’’(t+π/2) P in (t)=S(t) Signals emerge form output1 CP1 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) CP2 π P out,2 (t)=S’’’(t+π/2 + π)+S’’’(t+π/2 + π) P out,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 PBS S’’(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 1  2 Switch  The inter-output CR of a 1×2 switch is defined as the power ratio between the switched and non-switched signals at outputs ij where i, j = 1 or 2. Typically the value of inter-output CR observed at the SMZ output 2 (CR 21 ) is less than 10 dB.  Here we propose a 1×2 switch utilizing an optical inverter that offers improved CR 21.

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

All-optical Inverter Based on SMZ AA bar SOA Input (CLK) CP 1 (CLK) CP 2 (A) Output (A bar)

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

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

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

Simulation Results- The contrast ratio (CR) against the input packet power

Simulation Results- The contrast ratio (CR) against the control pulse power

Conclusion  T he 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.  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 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.

Special Thanks Special Thanks for Prof. Z. Ghassemlooy Dr. Wai Pang Ng Dr. Hoa Le Minh All colleagues in NCRLab & Your Attention

Questions/Suggestions/Comments, please Thank you for your kind attention.