An optical gyro comprising: a ring resonator having a predetermined mode and comprising an optical fiber coil having a hollow core and first and second ends; a first optical element configured to direct a portion of a first input light beam into said hollow core at said first end of said optical fiber coil and further configured to derive a first transmission component of a first circulating light beam; and a second optical element configured to direct a portion of a second input light beam into said hollow core at said second end of said optical fiber coil and further configured to derive a second transmission component of a second circulating light beam, said second circulating light beam derived from said portion of said first input light beam having said predetermined mode, said first circulating light beam derived from said portion of said second input light beam having said predetermined mode; and a third optical element configured to: receive said first and second input light beams; transmit said portion of said first input light beam to said first optical element; transmit said portion of said second input light beam to said second optical element; direct together with said first and second optical elements (54, 56) a majority of said first circulating light beam in a first counter-propagating direction of the ring resonator; and direct together with said first and second optical elements (54, 56) a majority of said second circulating light beam in a second counter-propagating direction of the ring resonator. a ring resonator having a predetermined mode and comprising an optical fiber coil having a hollow core and first and second ends; a first optical element configured to direct a portion of a first input light beam into said hollow core at said first end of said optical fiber coil and further configured to derive a first transmission component of a first circulating light beam; and a second optical element configured to direct a portion of a second input light beam into said hollow core at said second end of said optical fiber coil and further configured to derive a second transmission component of a second circulating light beam, said second circulating light beam derived from said portion of said first input light beam having said predetermined mode, said first circulating light beam derived from said portion of said second input light beam having said predetermined mode; and a third optical element configured to: receive said first and second input light beams; transmit said portion of said first input light beam to said first optical element; transmit said portion of said second input light beam to said second optical element; direct together with said first and second optical elements (54, 56) a majority of said first circulating light beam in a first counter-propagating direction of the ring resonator; and direct together with said first and second optical elements (54, 56) a majority of said second circulating light beam in a second counter-propagating direction of the ring resonator. receive said first and second input light beams; transmit said portion of said first input light beam to said first optical element; transmit said portion of said second input light beam to said second optical element; direct together with said first and second optical elements (54, 56) a majority of said first circulating light beam in a first counter-propagating direction of the ring resonator; and direct together with said first and second optical elements (54, 56) a majority of said second circulating light beam in a second counter-propagating direction of the ring resonator.