1. PGNET2006 M.F, Chiang 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/ Crosstalk Investigation of an All-Optical Serial-to-Parallel Converter Based on the SMZ

2. PGNET2006 M.F, Chiang Contents Introduction Semiconductor Optical Amplifier Symmetric Mach-Zehnder (SMZ) Gain Profiles and Switching Window Serial-to-Parallel Converter Crosstalk Results Conclusions

3. PGNET2006 M.F, Chiang 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. PGNET2006 M.F, Chiang Input signals (light) Carrier density & SOA gain (XGM) SOA refractive index & Induced phase (XPM) Input signals P N Injection current SOA Semiconductor Optical Amplifier (SOA)

5. PGNET2006 M.F, Chiang SOA Gain Profile g m : the material gain,  : the optical loss, g 0 : the gain coefficient, I: the injection current, N: the carrier density at the operating current I, N 0 : 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. PGNET2006 M.F, Chiang 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

7. PGNET2006 M.F, Chiang 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. PGNET2006 M.F, Chiang Bit 3 Bit 2 Bit 1 Bit 0 1 x 4 Splitter 3Tb3Tb 2Tb2Tb Tb Tb Bit 0 Bit 1 Bit 2 Bit 3 T sw CP1 CP2 Serial-to-Parallel Converter (SPC) - 1

9. PGNET2006 M.F, Chiang Serial-to-Parallel Converter (SPC) - 2

10. PGNET2006 M.F, Chiang Crosstalk (CXT) P nt : sum of the output signal power of all non-target channels and P t : the output signal power of the target channel. Switching window No-target channels

11. PGNET2006 M.F, Chiang VPI Simulation Parameters SOA Parameters Default Values SOA ParametersDefault Values Injection current 0.15 A Carrier density at transparency 1.4 x 10 24 m -3 Length500 x 10 -6 m Linewidth enhancement factor 4 Width3 x 10 -6 m Recombine constant A 1.43 x 10 8 s -1 Height80 x 10 -9 m Recombine constant B 1 x 10 -16 m 3 s -1 Confinement factor 0.15 Recombine constant C 3 x 10 -41 m 6 s -1 Internal losses40 x 10 2 m -1 Initial carrier density3 x 10 24 m -3 Differential gain 2.78 x 10 -20 m 2 System ParametersDefault Values Signal power1 mW Control power20 mW T sw 10 ps FWHM of signal & control pulses2 ps Emission wavelength of signal & control pulses 1552.52 nm Operation bit rate80 Gb/s

12. PGNET2006 M.F, Chiang Simulation Results – 1

13. PGNET2006 M.F, Chiang Simulation Results – 2

14. PGNET2006 M.F, Chiang Simulation Results – 3

15. PGNET2006 M.F, Chiang Simulation Results – 4 SOA Parameters Optimum Values System Parameters Optimum Values Injection current0.15 A Signal power0.5 mW Length1000 x 10 -6 m Control power20 mW Confinement factor 0.15 T sw 3 ps Linewidth enhancement factor 0.5 FWHM of signal & control pulses 1 ps Operation bit rateSPC Output power CXT 80 Gb/s2.80 mW – 33.27 dB 160 Gb/s1.40 mW– 28.20 dB 320 Gb/s0.47 mW– 22.78 dB

16. PGNET2006 M.F, Chiang 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. PGNET2006 M.F, Chiang Thank You ! Question, please ?