Electronic Photonic Integrated Circuits and Control Systems

Photonic systems can operate at frequencies several orders of magnitude higher than electronics, whereas electronics offers extremely high density and easily built memories. Integrated photonic-electronic systems promise to combine advantage of both, leading to advantages in accuracy, reconfigurability and energy efficiency. This work concerns of hybrid and monolithic electronic-photonic system design. First, a high resolution voltage supply to control the thermooptic photonic chip for time-bin entanglement is described, in which the electronics system controller can be scaled with more number of power channels and the ability to daisy-chain the devices. Second, a system identification technique embedded with feedback control for wavelength stabilization and control model in silicon nitride photonic integrated circuits is proposed. Using the system, the wavelength in thermooptic device can be stabilized in dynamic environment. Third, the generation of more deterministic photon sources with temporal multiplexing established using field programmable gate arrays (FPGAs) as controller photonic device is demonstrated for the first time. The result shows an enhancement to the single photon output probability without introducing additional multi-photon noise. Fourth, multiple-input and multiple-output (MIMO) control of a silicon nitride thermooptic photonic circuits incorporating Mach Zehnder interferometers (MZIs) is demonstrated for the first time using a dual proportional integral reference tracking technique. The system exhibits improved performance in term of control accuracy by reducing wavelength peak drift due to internal and external disturbances. Finally, a monolithically integrated complementary metal oxide semiconductor (CMOS) nanophotonic segmented transmitter is characterized. With segmented design, the monolithic Mach Zehnder modulator (MZM) shows a low link sensitivity and low insertion loss with driver flexibility

A system model for the effect of Polarization Mode Dispersion on digital modulated optical signals in single mode fibers

A comprehensive systems model that retains the discrete nature of the output delay distribution in order to accurately characterize the pulse broadening due to Polarization Mode Dispersion (PMD) is developed in this thesis. PMD in optical channels has been a critical factor limiting high-speed data transmission over long distances in optical networks. PMD is a source of Inter Symbol Interference (ISI) and its impact increases with the transmission data rate. Since economical adaptive compensation schemes are currently unavailable, it is essential to characterize this impairment to completely understand its impact and develop effective countermeasures. An incremental approach has been developed to methodically grow the output DGD distribution of single mode optical fibers. It provides the flexibility to change individual beat segment delays and enables the simulation and characterization of the distributed and the deterministic effects of PMD. The model also accurately evaluates the impact of the PMD impairment on the performance of optical networks in terms of Q. Results from comparing performance penalties at 10G bus, 40G bps and 100 Gbps data rates of transmission are in agreement with published trends

Birefringent fibre ring resonators: Analysis and stabilization techniques

The polarization stability of single-mode fibre resonators has been recognized as a potential problem in their operation. One method to overcome the polarization drift is to use a polarization-maintaining optical fibre, in the resonator system. Even this kind of resonators, still suffer from environmentally-induced polarization instabilities. Depending on the type of resonator, these instabilities are manifest as a split resonant dip, reduced finesse, reduced fringe modulation, fringe asymmetry, and unequal spacing between successive fringes. If we assume that a non zero amount of polarization crosstalk at the coupler is inevitable, then there is only one ideal type of resonator which is free from instabilities: a resonator made from polarizing fibre (or one that incorporates a perfectly aligned polarizer in the loop). The fringe shape variation can be reduced if the resonator is made with a deliberate 90 deg. axis twist at the splice or coupler, or if it is made with a polarization-selective coupler. No practical technique has been demonstrated so far, for producing consistently stable resonators with high finesse, using birefringent fibre. This is because the tolerable amount of coupler polarization crosstalk is very small, and the above ideal form is not easily made. It is therefore important to compare the output stability of the different resonator types as well as to investigate possible techniques for passive or active stabilization of the output. In this thesis work we have developed a experimentally verifiable resonator model that can be applied to different resonator types with minor modifications. We have derived tolerances for the coupler polarization crosstalk, splice alignment, and input polarization mode purity necessary for optimum operation of each type. A fringe shape stabilization system has been constructed, for use with fibre ring resonators with power exchange between the birefringent axes. The system works by keeping the depth of successive resonant dips equal, through a feedback electronic servo system, that controls the fibre birefringence. Two schemes for controlling the fibre birefringence are investigated

Distributed Fiber Ultrasonic Sensor and Pattern Recognition Analytics

Ultrasound interrogation and structural health monitoring technologies have found a wide array of applications in the health care, aerospace, automobile, and energy sectors. To achieve high spatial resolution, large array electrical transducers have been used in these applications to harness sufficient data for both monitoring and diagnoses. Electronic-based sensors have been the standard technology for ultrasonic detection, which are often expensive and cumbersome for use in large scale deployments. Fiber optical sensors have advantageous characteristics of smaller cross-sectional area, humidity-resistance, immunity to electromagnetic interference, as well as compatibility with telemetry and telecommunications applications, which make them attractive alternatives for use as ultrasonic sensors. A unique trait of fiber sensors is its ability to perform distributed acoustic measurements to achieve high spatial resolution detection using a single fiber. Using ultrafast laser direct-writing techniques, nano-reflectors can be induced inside fiber cores to drastically improve the signal-to-noise ratio of distributed fiber sensors. This dissertation explores the applications of laser-fabricated nano-reflectors in optical fiber cores for both multi-point intrinsic Fabry–Perot (FP) interferometer sensors and a distributed phase-sensitive optical time-domain reflectometry (φ-OTDR) to be used in ultrasound detection. Multi-point intrinsic FP interferometer was based on swept-frequency interferometry with optoelectronic phase-locked loop that interrogated cascaded FP cavities to obtain ultrasound patterns. The ultrasound was demodulated through reassigned short time Fourier transform incorporating with maximum-energy ridges tracking. With tens of centimeters cavity length, this approach achieved 20kHz ultrasound detection that was finesse-insensitive, noise-free, high-sensitivity and multiplex-scalability. The use of φ-OTDR with enhanced Rayleigh backscattering compensated the deficiencies of low inherent signal-to-noise ratio (SNR). The dynamic strain between two adjacent nano-reflectors was extracted by using 3×3 coupler demodulation within Michelson interferometer. With an improvement of over 35 dB SNR, this was adequate for the recognition of the subtle differences in signals, such as footstep of human locomotion and abnormal acoustic echoes from pipeline corrosion. With the help of artificial intelligence in pattern recognition, high accuracy of events’ identification can be achieved in perimeter security and structural health monitoring, with further potential that can be harnessed using unsurprised learning

Amplified Fiber-Optic Recirculating Delay Lines

Experimental and theoretical results on single- and double-amplified recirculating delay lines are presented. One of our aims is to emphasize their application as filters, showing a wide flexibility of design. Analysis of their performance in the spectral and time domains have been carried out. A novel method of understanding the behavior of double structures has been developed and successfully tested with experimental results employing Er-doped fiber amplifiers as delay lines.Publicad