M. F. Chiang, Z. Ghassemlooy, Wai Pang Ng, H. Le Minh, and V. Nwanafio

1. Crosstalk Investigation of an All-Optical Serial-to-Parallel Converter Based on the SMZ M. F. Chiang, Z. Ghassemlooy, Wai Pang Ng, H. Le Minh, and V. Nwanafio Optical Communication Research Group Northumbria University, United Kingdom http://soe.unn.ac.uk/ocr/

2. Contents • Introduction • Semiconductor Optical Amplifier • Symmetric Mach-Zehnder (SMZ) • Gain Profiles and Switching Window • Serial-to-Parallel Converter • Crosstalk • Results • Conclusions

3. Introduction • There is a growing demand for all optical switches and router at very high speed, to avoid the bottelneck imposed by the electronic switches. • In all-optical packet-switched networks, a Serial-to-Parallel Converter (SPC) is an important element in the header processing unit for address recognition. • SPC based on non-linear all-optical devices, e.g. SOAs, have have non-ideal switching window, thus experiencing residual channel crosstalk. • Here we investiagte a SPC at 80Gb/s investigating its crosstalk characteristics.

4. 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)

5. SOA Gain Profile gm: the material gain, :the optical loss,g0: the gain coefficient, I: the injection current,N: the carrier density at the operating current I,N0: the carrier density at transparency,i: the current injection efficiency,s: the spontaneous recombination lifetime of the carriers,e: the electronic charge,L,w, and d:the length, width, and thickness of the active region of the SOA.

6. PC1 PC1 SOA1 SOA1 PBS PBS Output1 Output1 Coupler2 Coupler2 Coupler1 Coupler1 Coupler4 Coupler4 Output2 Output2 PC2 PC2 Coupler3 Coupler3 SOA2 SOA2 PBS PBS CP1 CP2 PC 3 - dB coupler PBS Symmetric Mach-Zehnder (SMZ) Case 1: Without CP (SMZ is balanced) Case 1: Without CP (SMZ is balanced) 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) Signals emerge form output1 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) 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

7. Gain Profiles of SOA1&SOA2 and SMZ Switching Window (SW) ; Pout,1(t): The power at output1 of SMZ, Pin(t): the power of the input signal, : the phase difference of the input signals between the upper and lower arms of the SMZ, and LEF: the linewidth enhancement factor.

8. Serial-to-Parallel Converter (SPC) - 1 Tsw CP1 3Tb Bit 0 1 x 4 Splitter 2Tb Bit 3 Bit 2Bit 1Bit 0 Bit 1 Tb Bit 2 Bit 3 CP2

9. Output parallel bits CP1 3Tb SMZ1 SOA1 Input serial bits 0 SOA2 2Tb MSB LSB 1x4 Spliter 1 .. .1.. 1.. 0.. 1 Tb 2 3 CP2 FDL PC 3-dB coupler PBS Serial-to-Parallel Converter (SPC) - 2

10. No-target channels Crosstalk (CXT) Switching window Pnt: sum of the output signal power of all non-target channels and Pt: the output signal power of the target channel.

11. VPI Simulation Parameters

12. Simulation Results – 1

13. Simulation Results – 2

14. Simulation Results – 3

15. Simulation Results – 4

16. Conclusions • In the SPC,CXT is highly dependent on the gain of the SMZ switching window and the difference in the gain profiles of the SOAs in the gain recovery region. • There is a trade-off between the amount of CXT and the power level of the output signal. • By carefully selecting the SOA parameters the CXT level of the SPC could be further controlled to ensure the optimum performance.

17. Thank You ! Question, please ?