Study of the Kerr Phase-Interrogator and Its Applications
Creators: name: Lu, Yang
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2015
Subjects: Nonlinear optics
Fiber
Phase measurement

description: This thesis proposes and develops a novel optic configuration, Kerr phase-interrogator, which investigates the phase-shift between two sinusoidally modulated optical signals (SMOS) utilizing Kerr effect. The Kerr phase-interrogator gives birth to an entirely new technique for measuring the phase-shift between two light-waves. Taking advantage of all-optical signal processing, ultrafast responses, and being free from the coherent properties of a laser source, the Kerr phase-interrogator based technique for measuring the phase-shift is a promising novel approach for monitoring and sensing applications. The thesis begins with theoretically demonstrating the operation of Kerr phase-interrogator. As the core of optical process occurs in Kerr phase-interrogator, nonlinear interactions between two SMOSs in the Kerr medium are theoretically analyzed utilizing the models of nonlinear phase-modulation and four-wave mixing (FWM). The phase-modulation-based model is intuitive and allows for conceptual understanding of the operation of the Kerr phase-interrogator. However, this model does not account for the impact of chromatic-dispersion (CD) of the Kerr medium on the operation of the Kerr phase-interrogator. Compared with the former model, the FWM-based model is essential for acquiring insight into Kerr phase-interrogator, and can explain the CD impact of the Kerr medium. The analytical solution of the power of the first order sideband as a result of the nonlinear interaction is obtained in both theoretical models. The obtained solution shows sinusoidal dependence of the power on the phase-shift of the SMOSs. Utilizing this sinusoidal dependence, the phase-shift of two SMOSs can be acquired by measuring the power of the first-order sideband. Birefringence and CD are critical factors that affect the nonlinear interactions and thus impact the operation of Kerr phase-interrogator. In this work, vector analysis is performed on the nonlinear interaction between two SMOSs in a Kerr medium with randomly varying birefringence, and the effect of polarization-states of SMOSs on the operation of Kerr phase-interrogator is investigated. Impact of CD of Kerr medium on the operation of Kerr phase-interrogator is theoretically investigated using theory of FWM and is experimentally verified. Four typical applications, which comprehensively reflect the advantages of Kerr phase-interrogator, are proposed and experimentally demonstrated in this thesis. First, we present a novel approach for measurements of CD in long optical fibers using a Kerr phase-interrogator. The Kerr phase-interrogator measures the phase variation of a SMOS induced by CD in a fiber under test as the laser carrier wavelength is varied. This approach takes advantage of all-optical signal-processing based on Kerr effect to acquire the phase variation, and consequently removes the requirement of complex electrical signal-processors in existing techniques of CD measurement. CD measurement for several fibers is experimentally demonstrated. Second, a novel temperature sensor that utilizes temperature dependence of reflection group-delay in a linearly chirped fiber Bragg grating is presented. The reflection group-delay of chirped grating changes with temperature leading to a variation in the phase of a SMOS reflected from the grating. A Kerr phase-interrogator converts the phase-variation into power variation allowing for temperature sensing with a resolution of 0.0089 oC and a sensitivity of 1.122 rad/oC. Third, a Kerr phase-interrogator is applied for implementation of real-time CD monitoring. CD induces a phase-shift between two SMOSs carried by two different wavelengths. A Kerr phase-interrogator converts the phase-shift into power variation and CD monitoring is achieved by measurement of the power variation in real time with a resolution of 0.196 ps/nm. This application takes advantages of ultrafast response of Kerr phase-interrogator and achieves the real-time monitoring. Lastly, a novel approach for incoherent optical frequency-domain reflectometry based on a Kerr phase-interrogator is presented. The novel approach eliminates the limitation of finite coherent length of the light source, and achieves measurement of long-range distance beyond the coherent length of the light source. Long-range detection of reflection points as far as 151 km at a spatial-resolution of 11.2 cm is experimentally demonstrated.