Bandwidth limitation of conventional electrical demultiplexer restricts the data capacity of long-haul optical time division multiplexing (OTDM) systems. It is desirable to demultiplex the OTDM signal in optical domain, thereby lifting the bandwidth limitation of the electrical demultiplexer. The general principle of all-optical time division demultiplexing is to effect asymmetric changes to the optical properties of the target and non-target channels. The different optical properties of the target and non-target channels facilitate the separation of the target channel(s) from the aggregate OTDM signal. The change of optical properties of the OTDM signal can be achieved by exploiting various types of nonlinear optics effects, such as cross-phase modulation and four-wave mixing. Although the technical viability of all-optical demultiplexing has been successfully demonstrated in laboratories, there is still a lack of understanding regarding the noise and crosstalk characteristics of all-optical demultiplexers. This PhD study attempts to investigate noise and crosstalk performance of two types of all-optical time division demultiplexers, namely nonlinear optical loop mirror (NOLM) and terahertz optical asymmetric demultiplexer (TOAD). In order to evaluate the noise and crosstalk performance of NOLM and TOAD demultiplexers, mathematical models are developed to simulate the transmission window for demultiplexing the target channel. The shape of the transmission window is dependent on the device parameters of the demultiplexers. Varying input parameters of the mathematical models can simulate the effects of changing device parameters on the transmission window. Nevertheless, it is onerous to calculate transmission windows for infinite combinations of device parameters. To simplify the noise and crosstalk analysis, device parameters of NOLM and TOAD demultiplexers are optimised for maximising the peak of the transmission windows. Noise and crosstalk models are also developed forNOLM and TOAD demultiplexers. The optimised device parameters of NOLM and TOAD demultiplexers are fed into the noise and crosstalk models for analysis. Simulation results show that a tradeoff between noise and crosstalk exists for the two types of demultiplexers. Device parameters can be optimised to minimise either noise or crosstalk, but not both. Finally, the noise and crosstalk models are connected to a receiver model, where the bit-error-rate (BER) performance of OTDM systems is evaluated. The BER performances of the NOLM and TOAD demultiplexing are compared using the optimised device parameters. It is found that TOAD has a slightly better BER performance compared with NOLM for lower baseband bit rate (i.e. a larger number of OTDM channels for an aggregate bit rate).

As high bandwidth applications continue to emerge, investigation in technologies that will increase transmission capacity become necessary. Of these technologies, Optical Time Division Multiplexing (OTDM) has been presented as a possible solution, supporting a next generation bit rate of 160 Gbit/s. To perform the demultiplexing task, the use of tandem electro-absorption modulators (EAMs) has been widely studied, and due to its benefits was chosen as the topology of this thesis. To create an effective model of an OTDM system, the vector based mathematical simulation tool MatLab is used. Care was taken to create an accurate representation of an OTDM system, including: the development of a realistic pulse shape, the development of a true pseudo-random bit sequence in all transmitted channels, the optimization of the gating function, and the representation of system penalty. While posing impressive bit rates, various sources of system performance degradation pose issues in an OTDM system, owning to its ultra-narrow pulse widths. The presence of dispersion, timing jitter, polarization mode dispersion, and nonlinear effects, can sufficiently degrade the quality of the received data. This thesis gives a clear guideline to the tolerance an OTDM system exhibits to each of the aforementioned sources of system penalty. The theory behind each impairment is thoroughly discussed and simulated using MatLab. From the simulated results, a finite degree of sensitivity to each source of system penalty is realized. These contributions are of particular importance when attempting to implement an OTDM system in either the laboratory, or the field. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2010-05-17 22:51:56.471