Method and apparatus for enhanced evanescent field exposure in an optical fiber resonator for spectroscopic detection and measurement of trace species

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive optical fiber;
• at least one sensor in line with the optical fiber, the at least one sensor having a portion thereof exposed to the sample gas or sample liquid;
• a coherent source of radiation;
• coupling means for i) introducing a portion of the radiation emitted by the coherent source to the passive optical fiber and ii) receiving a portion of the radiation resonant in the passive optical fiber;
• a detector for detecting a level of the radiation received by the coupling means and generating a signal responsive thereto;
• and
• a processor coupled to the detector for determining a level of the trace species in the gas sample or liquid sample based on the signal generated by the detector,
• wherein the level of the trace species is determined based on a rate of decay of the signal generated by the detector.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive optical fiber;
• at least one sensor in line with the optical fiber, the at least one sensor having a tapered portion thereof exposed to the sample gas or sample liquid;
• a coherent source of radiation;
• coupling means for i) introducing a portion of the radiation emitted by the coherent source to the passive optical fiber and ii) receiving a portion of the radiation resonant in the passive optical fiber;
• a detector for detecting a level of the radiation received by the coupling means and generating a signal responsive thereto;
• and
• a processor coupled to the detector for determining a level of the trace species in the gas sample or liquid sample based on the signal generated by the detector,
• wherein the tapered portion is formed by heating and adiabatic stretching of the optical fiber.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive optical fiber;
• at least one sensor in line with the optical fiber, the at least one sensor having a portion thereof exposed to the sample gas or sample liquid, the exposed portion having a “D” shaped cross section;
• a coherent source of radiation;
• coupling means for i) introducing a portion of the radiation emitted by the coherent source to the passive optical fiber and ii) receiving a portion of the radiation resonant in the passive optical fiber;
• a detector for detecting a level of the radiation received by the coupling means and generating a signal responsive thereto;
• and
• a processor coupled to the detector for determining a level of the trace species in the gas sample or liquid sample based on the signal generated by the detector,
• wherein the “D” shaped cross section is formed by abrading a surface of a cladding of the optical fiber.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive optical fiber ring;
• at least one sensor in line with the optical fiber, the at least one sensor having a portion thereof exposed to the sample gas or sample liquid;
• a coherent source of radiation;
• coupling means for i) introducing a portion of the radiation emitted by the coherent source to the passive fiber optic ring and ii) receiving a portion of the radiation resonant in the passive fiber optic ring;
• a detector for detecting a level of the radiation received by the coupling means and generating a signal responsive thereto;
• and
• a processor coupled to the detector for determining a level of the trace species in the gas sample or liquid sample based on the signal generated by the detector,
• wherein coherent source of radiation is a pulsed laser. parametric amplifier.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive optical fiber;
• at least one sensor in line with the optical fiber ring, the at least one sensor having a portion thereof exposed to the sample gas or sample liquid;
• a coherent source of radiation;
• coupling means for i) introducing a portion of the radiation emitted by the coherent source to the passive fiber optic ring and ii) receiving a portion of the radiation resonant in the passive fiber optic ring;
• a detector for detecting a level of the radiation received by the coupling means and generating a signal responsive thereto;
• and
• a processor coupled to the detector for determining a level of the trace species in the gas sample or liquid sample based on the signal generated by the detector,
• wherein coherent source of radiation is a continuous waver laser.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive optical fiber;
• at least one sensor in line with the optical fiber, the at least one sensor having a portion thereof exposed to the sample gas or sample liquid;
• a coherent source of radiation;
• coupling means for i) introducing a portion of the radiation emitted by the coherent source to the passive fiber optic ring and ii) receiving a portion of the radiation resonant in the passive fiber optic ring;
• a detector for detecting a level of the radiation received by the coupling means and generating a signal responsive thereto;
• and
• a processor coupled to the detector for determining a level of the trace species in the gas sample or liquid sample based on the signal generated by the detector,
• wherein the passive optical is formed from one of fused silica, sapphire and fluoride based glass.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive optical fiber;
• at least one sensor in line with the optical fiber, the at least one sensor having a portion thereof exposed to the sample gas or sample liquid;
• a coherent source of radiation;
• coupling means for i) introducing a portion of the radiation emitted by the coherent source to the passive fiber optic ring and ii) receiving a portion of the radiation resonant in the passive fiber optic ring;
• a detector for detecting a level of the radiation received by the coupling means and generating a signal responsive thereto;
• a processor coupled to the detector for determining a level of the trace species in the gas sample or liquid sample based on the signal generated by the detector;
• and
• an input detector for determining when energy from the coherent source of radiation is provided to the optical fiber.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive optical fiber;
• at least one sensor in line with the optical fiber, the at least one sensor having a portion thereof exposed to the sample gas or sample liquid;
• a coherent source of radiation;
• coupling means for i) introducing a portion of the radiation emitted by the coherent source to the passive fiber optic ring and ii) receiving a portion of the radiation resonant in the passive fiber optic ring;
• a detector for detecting a level of the radiation received by the coupling means and generating a signal responsive thereto;
• and
• a processor coupled to the detector for determining a level of the trace species in the gas sample or liquid sample based on the signal generated by the detector,
• wherein an index of refraction of the optical fiber is based on an index of refraction of the sample gas and an absorption band of the trace species.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive optical fiber;
• at least one sensor in line with the optical fiber, the at least one sensor having a portion thereof exposed to the sample gas or sample liquid;
• a coherent source of radiation;
• coupling means for i) introducing a portion of the radiation emitted by the coherent source to the passive fiber optic ring and ii) receiving a portion of the radiation resonant in the passive fiber optic ring;
• a detector for detecting a level of the radiation received by the coupling means and generating a signal responsive thereto;
• and
• a processor coupled to the detector for determining a level of the trace species in the gas sample or liquid sample based on the signal generated by the detector,
• wherein the portion of the radiation coupled into the optical fiber is less than about 1% a of the radiation provided to the coupling means.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive optical fiber;
• at least one sensor in line with the optical fiber ring, the at least one sensor having a portion thereof exposed to the sample gas or sample liquid;
• a coherent source of radiation;
• coupling means for i) introducing a portion of the radiation emitted by the coherent source to the passive fiber optic ring and ii) receiving a portion of the radiation resonant in the passive fiber optic ring;
• a detector for detecting a level of the radiation received by the coupling means and generating a signal responsive thereto;
• and
• a processor coupled to the detector for determining a level of the trace species in the gas sample or liquid sample based on the signal generated by the detector,
• wherein the portion of the radiation coupled into the optical fiber is variable.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a closed passive optical fiber optic ring;
• at least one sensor in line with the optic fiber ring, each of the at least one sensor having a tapered portion thereof exposed to the sample gas or sample liquid;
• a coherent source emitting radiation;
• a first optical coupler to provide at least a portion of the radiation emitted by the coherent source to a first section of the passive resonant fiber ring;
• a second optical coupler for receiving a portion of the radiation in the passive resonant fiber ring from a second section of the resonant fiber ring;
• a processor coupled to the second optical coupler for determining a level of the trace species in the gas or liquid sample based on a rate of decay of the radiation received by the second optical coupler.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive resonant fiber optic ring;
• at least one sensor in line with the fiber optic ring, each of the at least one sensor having a tapered portion thereof exposed to the sample gas or sample liquid;
• a coherent source emitting radiation;
• a first optical coupler to provide at least a portion of the radiation emitted by the coherent source to a first section of the passive resonant fiber ring;
• a second optical coupler for receiving a portion of the radiation in the passive resonant fiber ring from a second section of the resonant fiber ring;
• a processor coupled to the second optical coupler for determining a level of the trace species in the gas or liquid sample based on a rate of decay of the radiation received by the second optical coupler;
• and
• a first optical detector coupled between the second optical coupler and the processor for generating a signal responsive to the radiation received by the second optical coupler.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a passive resonant fiber optic ring;
• at least one sensor in line with the fiber optic ring, each of the at least one sensor having a tapered portion thereof exposed to the sample gas or sample liquid;
• a coherent source emitting radiation;
• a first optical coupler to provide at least a portion of the radiation emitted by the coherent source to a first section of the passive resonant fiber ring;
• a second optical coupler for receiving a portion of the radiation in the passive resonant fiber ring from a second section of the resonant fiber ring;
• and
• a processor coupled to the second optical coupler for determining a level of the trace species in the gas or liquid sample based on a rate of decay of the radiation received by the second optical coupler;
• and
• a second optical detector coupled between the first optical coupler and the processor for determining when energy from the coherent source of radiation is provided to the passive fiber optic ring.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a closed passive resonant fiber optic ring;
• at least one sensor in line with the fiber optic ring, each of the at least one sensor having a tapered portion thereof exposed to the sample gas or sample liquid;
• a coherent source emitting radiation;
• a first optical coupler to provide at least a portion of the radiation emitted by the coherent source to a first section of the passive resonant fiber ring;
• a second optical coupler for receiving a portion of the radiation in the passive resonant fiber ring from a second section of the resonant fiber ring;
• and
• a processor coupled to the second optical coupler for determining a level of the trace species in the gas or liquid sample based on a rate of decay of the radiation received by the second optical coupler,
• wherein the first and second optical couplers are a unitary coupler.

An apparatus for detection and measurement of trace species in at least one of a sample gas and a sample liquid comprising:

• a continuous closed passive resonant fiber optic ring;
• at least one sensor in line with the fiber optic, the at least one sensor having a “D” shaped cross section portion thereof exposed to the sample gas or sample liquid;
• a coherent source emitting radiation;
• a first optical coupler to provide at least a portion of the radiation emitted by the coherent source to a first section of the passive resonant fiber ring;
• a second optical coupler for receiving a portion of the radiation in the passive resonant fiber ring from a second section of the resonant fiber ring;
• and
• a processor coupled to the second optical coupler for determining a level of the trace species in the gas or liquid sample based on a rate of decay of the radiation received by the second optical coupler.