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Presentation Outline Introduction  All-optical packet switching  All-optical router  Mach-Zehnder Interformeter(MZI) SOA structure Problem Proposed Our proposal

Presentation Outline Segmentisation model Uniform biasing Non-uniform biasing  Triangular bias current  Sawtooth bias current Comparison between uniform and non-uniform biasing techniques Conclusions

All-optical packet switching

All-optical router

Mach-Zehnder Interformeter (MZI)

Symmetric Mach-Zehnder (SMZ) Mach-Zehnder Interformeter (MZI)

Advantages of SMZ  Narrow and square switching window  Compact size  Thermal stability and low power operation  High integration potential  Strong nonlinearity characteristics Mach-Zehnder Interformeter (MZI)

Injection current (I) L Input facet of active region Input signals Output signals Output facet H w SOA structure

Problem For high-speed applications, the SOA must have a fast gain recovery time to avoid system penalties arising from bit pattern dependencies. The gain recovery of the conventional SOAs is limited by the long carrier-recovery time.

Proposed The slow gain recovery can be improved by increasing the injected bias current, the device length or by changing the pulse width (input energy) of the input signal [5]. Several research groups have reported theoretical and experimental results on externally injected SOAs (assist light or holding beam ) [6,7].

Our proposal Novel non-uniform bias current techniques are injected to the SOA in order to achieve a linear output gain compared to the uniform biasing for ultra-high speed routers.

segment1segment2…………..…………….segment5 t=0 g t=l/v g t=L/v g input signal output signal NiNi N(1) N(5) Segmentisation model of the SOA

Normalized SOA gain response to single (doted) and multiple (solid) input pulses. Uniform Biasing

Normalized output gain achieved by successive input pulses. Uniform Biasing

Sawtooth (doted) and triangular (solid) bias currents. Non-uniform Biasing

Normalized SOA gain response to multiple of input pulses using triangular bias current. Triangular bias current

Normalized output gain achieved by successive input pulses using triangular bias current as a ratio of uniform bias current. Triangular bias current

Normalized SOA gain response to multiple of input pulses using sawtooth bias current. Sawtooth bias current

Normalized output gain achieved by successive input pulses using sawtooth bias current as a ratio of uniform bias current. Sawtooth bias current

Comparing uniform and non-uniform biasing Gain standard deviation against the input signal energy for uniform (dot- dashed), sawtooth (doted) and triangular (solid) biasing for a range of data rates.

Comparing uniform and non-uniform biasing Improvement of the gain standard deviation upon uniform biasing For sawtooth bias current: at 10 Gbps 3.25 dB at 20 Gbps 0.51 dB at 40 Gbps min improvement For triangular bias current: at 10 Gbps 2.4 dB at 20 Gbps 0.4 dB at 40 Gbps min improvement

Gain standard deviation against the average sawtooth bias current for 1 fJ input signal energy.

Conclusions We have proposed novel techniques to bias the SOA. The total gain response of a segmentized SOA model is simulated. We have investigated applying triangular and sawtooth biasing shapes in order to optimize the gain standard deviation for data rates of 10, 20 and 40 Gbps. Results showed an enhancement to the gain uniformity achieved using non-uniform biasing, especially sawtooth biasing. The impact of the input pulse energy on the gain standard deviation and the output gain for all biasing techniques are investigated. The impact of the average bias current used on the gain uniformity is presented.