Micro-ring resonators are a strong candidate for the basic building blocks of very-large-scale-integrated optics. They can be used in many applications, such as filters, routers, switches, lasers, and amplifiers. They are simple in design and concept, can be made very small, and do not require exotic materials or fabrication techniques. In this thesis, I describe my work on indium phosphide based active and passive micro-ring resonators. To enable low-loss devices, I develop a dry-etching process for InP using the methane chemistry in a capacitively-coupled reactive-ion-etching machine. Using the etch process, I demonstrate single-mode micro-ring resonators in the vertically- and laterally-coupled geometries, all-optical logic, and a tunable micro-ring notch filter. The best devices in the vertically-coupled geometry have bandwidth as low as $0.24~\nm$, free spectral range of $24~\nm$, $Q = 6200$, and finesse of $100$ while the laterally-coupled micro-rings have bandwidth as low as $0.25~\nm$, free spectral range of $8~\nm$, $Q = 6250$, and finesse of $32$. Some of the laterally-coupled devices have free spectral ranges as high as $28~\nm$, though the corresponding $Q$ is low. Tarek Ibrahim and I demonstrate all-optical logic (AND operation) using carrier-induced refractive index change by two-photon-absorption with switching speed of $100~\ps$, dominated by ambipolar diffusion. Finally, I demonstrate tuning by $100~\GHz$ ($0.8~\nm$) with $8~\volt$ reverse bias of an InP-based micro-ring resonator with a p-i-n structure using the quadratic electro-optic effect, obtaining $1.5~\GHz/\volt^2$ of tuning.