1 Razali Ngah, and Zabih Ghassemlooy Optical Communication Research Group School of Engineering & Technology Northumbria University, United Kingdom http: soe.unn.ac.uk/ocr/ The Performance of An OTDM Demultiplexer Based on SMZ Switch

2 Contents Introduction OTDM All optical switches Simulations and results Conclusions

3 Introduction Solution: All optical transmission, multiplexing, switching, processing, etc.  Multiplexing:- To extend a transmission capacity  Electrical  Optical Drawbacks with Electrical: Speed limitation beyond 40 Gb/s (80 Gb/s future) of: Electo-optics/opto-electronics devices High power and low noise amplifiers Bandwidth bottleneck due to optical-electronic-optical conversion

4 Multiplexing - Optical Wavelength division multiplexing (WDM) Optical time division multiplexing (OTDM)  Hybrid WDM-OTDM

5 The total capacity of single-channel OTDM network = DWDM Overcomes non-linear effects associated with WDM: (i) Self Phase Modulation (SPM) – The signal intensity of a given channel modulates its own refractive index, and therefore its phase (ii) Cross Phase Modulation (XPM) – In multi-channel systems, other interfering channels also modulate the refractive index of the desired channel and therefore its phase (iii) Four Wave Mixing (FWM) – Intermodulation products between the WDM channels, as the nonlinearity is quadratic with electric field Less complex end node equipment (single-channel Vs. multi-channels) Can operate at both: 1500 nm 1300 nm OTDM

6 OTDM - Principle of Operation Multiplexing is sequential, and could be carried out in: A bit-by-bit basis (bit interleaving) A packet-by-packet basis (packet interleaving) Clock Receiver Transmitter Clock recovery Light source Light source Data (10 Gb/s) N Network node Network node Drop Add Rx 10 GHz N*10 Gb/s Data (10 Gb/s) OTDM DEMUX OTDM MUX AmplifierModulators Fibre delay line Fibre Span

7 All Optical Switches Non-linear Optical Loop Mirror (NOLM) Terahertz Optical Asymmetric Demultiplexer (TOAD) Requires high control pulse energy and long fiber loop Asymmetrical switching window profile due to the counter-propagating nature of the data signals

8 All Optical Switches – contd. Symmetric Mach-Zehnder (SMZ) Symmetrical switching window profile Integratable structure

9 All Optical Switches – contd. DeviceSwitching Time Repetition Rate (GHz) Noise Figure (dB) Ease of Integration? Practicality SMZ< 1 ps100+ GHz6YESHIGH TOAD< 1 ps100+ GHz6YESMEDIUM NOLM0.8 ps100+ GHz0NOLOW UNI< 1 ps100+ GHz6NOMEDIUM Comparative study of all optical switches [Prucnal’01]

10 SMZ Switch: Principle (i) No control pulses (ii) With control pulses

11 SMZ : Switching Window G 1 and G 2 are the gains profile of the data signal at the output of the SOA1 and SOA2, ΔФ is the phase difference between the data signals, and LEF is linewidth enhancement factor

12 SMZ : Switching Window (simulation) TABLE I. SIMULATION PARAMETERS ParameterValue SOA. LengthL SOA 0.3 mm. Active area, 3.0x m 2. Transparent carrier density, N o 1.0x10 24 m -3. Confinement factor,  Differential gain, g2.78x1020 m2. Linewidth enhancement, 4.0. Recombination coefficient A1.43x10 8 1/s. Recombination coefficient B1.0x m 3 /s. Recombination coefficient C3.0x m 6 /s. Initial carrier density2.8x10 24 m -3. Total number of segments50 Data and control pulses. Wavelength of control & data1550 nm. Pulse FWHM2 ps. Control pulse peak power1.2 W. Data pulse peak power2.5 µW

13 SMZ : Switching Window (comparison) TheoreticalSimulation

14 The ratio of the output power in the on-state to the output power in the off-state SMZ : On-Off Ratio Input signal of the SMZTransmitted output of the SMZ

15 SMZ : On-Off Ratio – contd. On-off ratio and normarlised transmission power Against linewidth enhancement factor On-off ratio at different data rate

16 SMZ : BER Performance ___________________________________ ParameterValue Pre-amplifier ModeGain controlled Noise Figure4 dB Gain25 dB PIN detector Responsivity1 A/W Thermal noise10 pA/Hz 1/2 Cutoff frequency7.0x10 9 Hz __________________________________________ Receiver parameters

17 SMZ : BER Performance – contd. BER against the average received power for (a) back-to-back without demultiplexer, (b) 40 – 10 Gb/s demultiplexer, (c) 80 – 10 Gb/s demultiplexer and (d) 160 – 10 Gb/s demultiplexer

18 SMZ : BER Performance – contd. Ngah’04Tekin’02 IWC4 Diez’00 Elec. Lett Hess’98 PTL Jahn’95 Elec. lett Back-to-back (10 Gb/s) Sensitivity -38 dBm -35 dBm -35 dBm -34 dBm -37 dBm Gb/s demux. Power penalty 1.2 dBNA 0 dB2.5 dB Gb/s demux. Power penalty 1.4 dB1 dB1.2 dB4 dBNA Gb/s demux. Power penalty 1.5 dB3.5 dB2.8 dBNA Comparison with experimental results

19 Application of SMZ switch: 1x2 All OTDM Router

20 Conclusions An all optical demultiplexer based on SMZ has been implemented in a simulation environment using VPI. BER analysis has been performed. The power penalty of the demultiplexer is mainly due to the ASE noise in the SOAs of the SMZ. The application of low noise SOA will reduce the power penalty.  An all optical demultiplexer based on SMZ has been implemented in a simulation environment using VPI.  Simulation results show a small power penalty of 0.7 dB for the system with all optical SMZ demultiplexer compared with the system without a demultiplexer.  An all optical demultiplexer based on SMZ has been implemented in a simulation environment using VPI.  Simulation results show a small power penalty of 0.7 dB for the system with all optical SMZ demultiplexer compared with the system without a demultiplexer.

21 Acknowledgement  Thanks to the University of Teknologi Malaysia for sponsoring the research.

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