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).

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Photonic crystals (PCs) are nano-structured materials in which a periodic variation of the dielectric constant of the material results in a photonic band gap. By introducing defects into PCs, it is possible to build waveguides that can channel light along certain paths. It is also possible to construct micro-cavities that can localize photons in extremely small volumes. In this dissertation, to begin with, we computed the photonic crystals dispersion relations and found the photonic band gap (PBG) by the plane wave expansion method (PWE) in the frequency domain. Then, the finite difference time domain method (FDTD) along with the perfectly matched layer boundary conditions was adopted to solve Maxwell¡¦s equations, equivalent to simulate the movement behavior of the Photonic crystals. By properly varying the size of the defect on the PCs, it could really drop the particular wavelengths and guide them to output channels by PCs waveguides. We proposed the structures that would function as Wavelength-Division-Multiplexer (WDM). Secondly, coupled cavity waveguide of PC was used to control group velocity that achieved the slow light property. By calculating dispersion curve with PWE, we obtained group velocity characteristics in PCs waveguide. Meanwhile, we designed a novel Time-Division-Multiplexer (TDM) system by controlling the group velocity characteristics. Finally, we designed cascade ring resonators and expected to obtain an extendable delay line. Conventional delay line devices are propagating in a long waveguide to obtain the delay line property. An excellent delay line and ultra-small size properties are expected in the proposed structure. Because nano-technology has been making great progress steadily, it surely can be used to demonstrate a practical breakthrough in which the devices based on the PC integrated circuits are realized. These devices will be a potential key component in the applications of ultra-high-speed and ultra-high-capacity optical communications and optical data processing systems.

När olika datatyper överförs mellan två platser har, historiskt sett, detta skett på skildinfrastruktur; analoga signaler för sig, och digitala data för sig. Inom flygindustrin hanteras båda dessa datatyper än idag, då övergång från analoga röstsamtal till digitala röstsamtal tar tid. För att förenkla infrastrukturen är det önskvärt att skicka all data på samma medium. Time Division Multiplexing (TDM) möjliggör detta och har studerats med fokus på robusthet och prestanda. Studien har fokuserat på hur TDM-enheter ska konfigureras med avseende på Ethernet-frame-storlek för att till fullo utnyttja länkkapaciteten. Teoretiska resonemang har validerats av experimentella data som utförts på TDM-enheter sammankopplade med en fiberlänk. Antalet förlorade frames för systemet har mätts med varierande datatillförselshastighet. Detta upprepades för ett flertal Ethernet-frame-storlekar. Mindre frame-storlekar gav en högre möjlig överföringshastighet innan data förloras, och uppvisade koherens mellan teori och experiment. Stora frame-storlekar fyllde i snitt TDM-tidsluckorna sämre, och gjorde att databuffert på enheten fylldes snabbare än för mindre framstorlekar. Detta ledde till dataförluster i systemet. Andra faktorer, som overhead och payload, gjorde att framestorleken borde väljas efter applikation. Mindre datamängder som skickas ofta kan med fördel använda mindre frame-storlekar, medan stora datamängder som behöveröverföras snabbt effektivare överförs med större frame-storlekar. / When transferring different data types between two sites, they have historically been transferred on separate infrastructures; analog signals separately, and digital data separately. Within the aviation industry, both these data types are still handled today, as transition from analog voice data to digital voice data takes time. To simplify the infrastructure, it is desirable to send all data on the same medium. Time Division Multiplexing (TDM) makes this possible and has been studied with focus on robustness and performance. The study has focused on how TDM devices should be configured with respect to Ethernet frame size to fully utilize link capacity. Theoretical reasoning has been validated by experimental data performed on TDM devices coupled with a fiber link. The number of lost frames for the system has been measured while varying data rates. This was repeated for several Ethernet frame sizes. Smaller frame sizes showed a higher possible transfer rate before data loss was recorded. This shows coherence between theory and experiments. Larger frame sizes were less good at filling the TDM time slots, causing data buffer on the device to overflow faster than for smaller frame sizes. This created data loss in the system. Other factors, such as overhead and payload, implies that the frame size should be chosen by application. Smaller data volumes that are sent frequently have an advantage when using smaller frame sizes, while when handling largeramounts of data that need to be transmitted quickly, it is more efficient to use larger frame sizes

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / An advanced electro-optic hybrid rotary joint (EOHRJ) has been developed in Phase II of an AF SBIR effort with Physical Optics Corporation (POC) to replace cable wrap structure for multi-channel rotation-to-fixed (RTF) signal transmission. The EOHRJ meets AFFTC and other range special needs with a generic, high performance, rotary joint solution. At the moment, we have successfully installed and tested the EOHRJ on our KTM tracker system with the following capabilities: 1) able to accommodate hundreds of transmission channels, including electrical power, control, feedback, and low-speed signals; 2) able to accommodate multiple channel, high data rate (over gigabits per second), and bi-directional signal transmission; 3) able to be reliable for harsh environmental operation, adaptive to stringent sized requirement, and accommodating existing electrical and mechanical interfaces. The completed EOHRJ contains three uniquely integrated functional rings. The first and the outmost one is power ring, which provides RTF transmission channels for over 50 high voltage and high current channels. The second and the middle one is low speed electrical signal ring, which provides RTF transmission for over hundred control, feedback, and low speed data signals. The third and the inmost one is optical fiber slip ring, which, incorporating with current advanced signal multiplexing technologies (either time division or wavelength division multiplexing ) is able to provide multiple channel, high data rate, and bi-directional signal transmission. At the moment, the prototype module of the tree-layer EOHRJ has been successfully assembled in Air Force’s tracker system, and is providing a satisfactory performance. This paper presents our joint work on this project.

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

Solar energy is widely used for electricity generation, heating systems, and indoor environment daytime illumination. Indeed, large amounts of Sunlight energy remain insufficiently used. In this work, we aim at employing sunlight for data transmission as another option for wireless communications. Being emitted by an uncontrollable source, taming the Sunlight is a challenging task that requires appropriate technolo- gies to manipulate incident light. Throughout this thesis, we first review switchable glass technologies and investigate their potential use for light modulation. Liquid Crystal Devices (LCD) have adequate response time and contrast characteristics for such an application. In this regard, we design a novel Dual-cell Liquid Crystal Shutter (DLS) by stacking two Liquid Crystal cells that operate in opposite manners, and we build our Sunlight modulator with an array of DLSs. Then, we adopt Time Division Multiplexing and polarization-based modulation to boost the data rate and eliminate the flickering effect. In addition, we provide mathematical modeling of the system and study its performance in terms of communication and energy consumption. Finally, we introduce some numerical results to examine the impact of multiple parameters on the system’s performance and compare it with state-of-the-art, which showed that our system features higher data rates and extended link ranges.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Current ground-based tracking systems at the DoD test and training ranges require transmission of a variety of signals from rotating platform to fixed control and process center. Implementation of commercial off the shelf (COTS) solution for transmitting high-speed, multiple-channel data signals over a rotational platform prompt the development of an advanced electro-optic hybrid rotating-to-fixed information transmission technology. Based on current demand, an Air Force-sponsored Small Business Innovative Research (SBIR) contract has been awarded to Physical Optics Corporation (POC) to modify existing tracking mounts with a unique electro-optic hybrid rotary joint (EOHRJ). The EOHRJ under current development is expected to provide the following features: 1) include a specially designed electrical slip-ring, which is able to accommodate hundreds of transmission channels, including electrical power, control, feedback, and low-speed data signals; 2) include an optical fiber slip-ring which, by incorporating with electrical time division mulitplexing (TDM) and optical wavelength division multiplexing (WDM) technologies, is able to provide multiple channel, high data rate (over gigabits per second), and bi-directional signal transmission; and 3) is designed to be reliable for harsh environmental operation, adaptive to stringent size requirement, and accommodating to existing electrical and mechanical interfaces. Besides the military use, other possible commercial applications include on board monitoring of satellite spinners, surveillance systems, instrumentation and multi spectral vision systems, emergency/medical instruments, remote sensing, and robotics.

It is often required in communication and navigation systems to be able to receive signals from multiple stations simultaneously. A common practice to do this is to use multiple hardware resources; a different set of resources for each station. In this thesis, a Coherent Amplitude Modulated (AM) receiver system was developed based on Software Defined Radio (SDR) technology enabling reception of multiple signals using hardware resources needed only for one station. The receiver system architecture employs Time Division Multiplexing (TDM) to share the single hardware resource among multiple streams of data. The architecture is designed so that it can be minimally modified to support any number of stations. The Verilog Hardware Description Language (HDL) was used to capture the receiver system architecture and design. The design and architecture are initially validated using HDL post-synthesis and post-implementation simulation. In addition, the receiver system architecture and design were implemented to a Xilinx Field Programmable Gate Array (FPGA) technology prototyping board for experimental testing and final validation.

Few mode fibers and multimode fibers (MMFs) are traditionally regarded as unsuitable for important applications such as communications and sensing. A major challenge in using MMFs for aforementioned applications is how to precisely control the waveguide modes propagating within MMFs. In this thesis, we experimentally demonstrate a generic method for controlling the linearly polarized (LP) modes within a two-mode fiber (TMF). Our method is based on adaptive optics (AO), where one utilizes proper feedback signals to shape the wavefront of the input beam in order to achieve the desired LP mode composition. In the first part of this thesis, we demonstrate the feasibility of AO-based mode control by using the correlation between the experimentally measured field distribution and the desired mode profiles as feedback for wavefront optimization. Selectively excitation of pure LP modes or their combinations at the distal end of a TMF are shown. Furthermore, we demonstrate that selective mode excitation in the TMF can be achieved by using only 5×5 independent phase blocks. Afterwards, we extend our AO-based mode control method to more practical scenarios, where feedback signals are provided by all-fiber devices such as a directional fiber coupler or fiber Bragg gratings (FBGs). Using the coupling ratio of a directional coupler as feedback, we demonstrate adaptive control of LP modes at the two output ports of the directional coupler. With feedback determined by the relative magnitude of optical power reflected by a FBG and the transmitted power, selective excitations of the LP01 and the LP11 modes are experimentally shown. As the final component of this thesis, we experimentally combine the AO-based mode control with time-division-multiplexing. By choosing reflected pulses with appropriate arrival time for mode control, we can selectively excite the LP11 mode at different FBG locations within the TMF, based on the ratio of optical signals reflected by FBGs in the TMF and the transmitted signal. Using two lasers set at the two FBG peak reflection wavelengths associated with the LP01 and the LP11 modes, we can accomplish AO-based mode control within a TMF by using only the reflection signals from the FBG. By using the ratio of the reflected signals of two lasers as feedback, we demonstrate selective excitation of almost pure LP01 or LP11 mode at the FBG location within the TMF. The method developed in this thesis is generic and can be extended to many other applications using appropriately chosen feedback signals. It is possible to generalize the AO-based mode control method to MMF as well. This method may find important applications in MMF-based communication, sensing and imaging et. al. in the future. / Ph. D.