Wavelength-parallel techniques for efficient spectral polarimetry, polarization mode dispersion penalty monitoring, and differential group delay emulations

Shawn X Wang, Purdue University

Abstract

Polarization of light within an optical fiber constantly changes due to environmentally induced birefringence in the fiber, and the time scale of variation can be milliseconds or less. This phenomenon originates various fiber optic communication system impairments such as polarization mode dispersion (PMD) and polarization dependent loss. The first part of this thesis examines a purposefully designed spectral polarimeter for the use in performance monitoring of optical communication systems. The polarimeter is capable of performing polarization measurements for hundreds of wavelength division multiplexed (WDM) channels within 1ms---orders of magnitude faster than commercially available devices. A variation of the design boasts broadband and high resolution polarimetry necessary for resolving spectral polarization variations within each WDM channel for multiple channels simultaneously. The second part describes a non-intrusive PMD penalty monitoring technique utilizing our fast spectral polarimeter. PMD recently emerged as a key limiting factor in pushing the optical transmission rate to 10 Gb/s and beyond for long-haul optical transmission systems. Evaluating the PMD induced system penalty distinct from other system impairments is important for applications in PMD monitoring, compensation, and mitigation schemes. Most common PMD penalty monitoring techniques today require expensive equipments such as RF spectrum analyzers and gigahertz oscilloscopes. The technique described in this thesis allows cost-effective, near real-time PMD penalty monitoring, and has also been field tested on commercial systems at AT&T. Differential group delay (DGD) constitutes the magnitude of the PMD vector. The last topic of the thesis describes an all-order DGD emulator. The current DGD emulators are based on a multi-waveplate model, which mimics the random nature of PMD in real long-haul optical fibers. Our DGD emulator design is based on a Fourier pulse shaping technology which can be programmed to possess arbitrary user-defined frequency dependent DGD profile. This deterministic controllability is an important feature for applying importance sampling technique in systems testing to significantly increase efficiency in studying PMD effects.

Degree

Ph.D.

Advisors

Weiner, Purdue University.

Subject Area

Electrical engineering

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