Patent ID: 7327460

Claim:
A ring resonator for circulating light beams in first and second counter-propagating directions, the ring resonator comprising: an optical fiber coil having a hollow core and first and second ends; a first partially reflective body configured to: receive an input light beam; and direct a portion of said input light beam in said first counter-propagating direction of the ring resonator, said portion of said input light beam entering one of said first and second ends; and a second partially reflective body configured to: direct together with said first partially reflective body a majority of a circulating light beam in said first counter-propagating direction of the ring resonator, said circulating light beam based on said input light beam; and derive a transmission mode component of said circulating light beam at one of said first and second ends, said transmission mode component indicating a first resonance peak of said first counter-propagating direction of the ring resonator.