Abstract: An optical pH sensor and a gas sensor utilizing the pH sensor. The pH sensor includes an indicator whose absorbance is a function of the concentration of hydronium ions in a media surrounding the indicator. Light transmitted and reflected through the indicator of the sensor undergoes an absorption that is characteristic of the concentration of the hydrogen ion. The pH sensor can be used as to sense the concenration of a gas in a sample by surrounding the indicator with a liquid or liquid-containing media that changes pH as it is exposed to the gas, and separating the indicator and liquid or liquid-containing media from the gas with a membrane that is permeable to the gas to be measured. A measuring system used with the sensors transmits coherent radiation to the sensor through an optical fiber, separates the radiation returning from the sample into two wavelength bands, and digitally samples the photocurrents produced within the two wavelength bands.

Abstract: Physical changes induced in the spectral modulation sensor's optically resonant structure by the physical parameter being measured cause microshifts of its reflectivity and transmission curves, and of the selected operating segment(s) thereof being used, as a function of the physical parameter being measured. The operating segments have a maximum length and a maximum microshift of less than about one resonance cycle in length for unambiguous output from the sensor. The input measuring light wavelength(s) are selected to fall within the operating segment(s) over the range of values of interest for the physical parameter being measured. The output light from the sensor's optically resonant structure is spectrally modulated by the optically resonant structure as a function of the physical parameter being measured. The spectrally modulated output light is then converted into analog electrical measuring output signals by detection means.

Abstract: An optical pressure-sensing system in which an optical beam splitter couples input light from a light source to an optically resonant pressure sensor and couples output light reflected from the sensor to a light detector. The light detector may divide the output light into bands having different wavelengths and then take the ratio of the light in one band to the light in the other band in order to provide an output that is insensitive to various spurious responses in the system. The optical beam splitter may be formed by two pairs of graded refractive index lenses. A partially reflective, partially transmissive mirror is sandwiched between the lenses of one pair, while a dichroic mirror is sandwiched between the second pair. The pairs of lenses are placed in abutting relationship to each other. The optical beam splitter may also be formed by a block of transparent material having a partially reflective, partially transmissive mirror on one edge.

Abstract: Physical changes induced in the spectral modulation sensor's optically resonant structure by the physical parameter being measured cause microshifts of its reflectivity and transmission curves, and of the selected operating segment(s) thereof being used, as a function of the physical parameter being measured. The operating segments have a maximum length and a maximum microshift of less than about one resonance cycle in length for unambiguous output from the sensor. The input measuring light wavelength(s) are selected to fall within the operating segment(s) over the range of values of interest for the physical parameter being measured. The output light from the sensor's optically resonant structure is spectrally modulated by the optically resonant structure as a function of the physical parameter being measured. The spectrally modulated output light is then converted into analog electrical measuring output signals by detection means.

Abstract: The invention relates to optical devices for sensing and measuring various physical parameters. More particularly, this invention relates to an optical device having a spectral modulation sensor in which the physical parameter being measured causes spectral changes in the reflectivity and/or transmission of the sensor's optically resonant structure, thereby spectrally modulating the output light from the sensor as a function of the physical parameter being measured.