Abstract: An optical channel monitor is described, the optical channel monitor includes an optical input port, a photodetector disposed in an optical path communicating at least intermittently with the optical input port, an optical filter disposed in the optical path between the optical input port and the photodetector, and an optical band splitter disposed in the optical path between the optical filter and the photodetector. The optical filter is a multibandpass filter, such as a scanning Fabry-Perot filter. The optical channel monitor also comprises a reference light system for providing a calibration standard against which an optical signal input through the input port may be compared. The channel monitor finds application in optical transmission systems including wavelength division multiplexed (WDM) optical communication systems.

Abstract: A passive, temperature compensated tunable filter calibration device in a Bragg-grating interrogation system. The invention comprises two systems: 1) a dual substrate Bragg grating calibration system, the temperature of an array of gratings is estimated using an array of gratings bonded to a common host substrate and a single grating bonded to a material with a different coefficient of thermal expansion; 2) a hydrogen cyanide wavelength reference absorption cell that absorbs light at discrete wavelengths corresponding to the molecular vibration mode frequencies of the gas. A first photodetector sees the transmission spectrum and a second sees the reflections from Bragg gratings in a sensing array. In this system there is no temperature compensation step as the absorption lines are not sensitive to temperature.

Abstract: A new optical sensing device containing fiber Bragg gratings, a scanning bandpass filter, an interferometer and multiple photodetectors is disclosed. The present invention also describes a new system and method for fibre Bragg grating (FBG) sensor interrogation and multiplexing. The new system combines a scanning Fabry-Perot (SFP) bandpass filter used to wavelength-multiplex multiple gratings in a single fiber, and an unbalanced Mach-Zehnder fibre interferometer made with a 3×3 coupler to detect strain-induced wavelength shifts. A passive technique for interferometer drift compensation using non-sensing FBGs is included in the system. A complete prototype system interrogates four gratings in a single fiber at a Nyquist sampling rate up to 10 kHz, with a noise floor measured near 4 n&egr; Hz−1/2 above 0.1 Hz. The inclusion of the interferometer drift compensation technique is shown to make quasi-static measurements feasible.

Abstract: A passive, temperature compensated tunable filter calibration device for a Bragg grating interrogation system. In a first system, a dual-substrate Bragg grating calibration system, the temperature of an array of gratings is estimated using an array of gratings bonded to a common host substrate and a single grating bonded to a material with a different coefficient of thermal expansion. Changes in a common temperature of the substrates is measured by monitoring the difference between shifts of grating wavelength. As a filter voltage is scanned from its lowest to its highest voltage, the voltages are recorded. The second lowest wavelength corresponds to the grating attached to the differing substrate. The voltages are used to calculate a voltage-to-wavelength function for the scanning range of the filter. To compensate for variations in a calibration curve and temperature variations of the calibration array, the temperature is estimated and function re-calculated at every pass of the scanning filter.

Abstract: The invention includes a method and apparatus for monitoring wavelength of an optical channel. A tunable optical bandpass filter is used to correlate a signal from an optical transmission line with a signal from a reference light source. The signal from the reference light source passes through a reference gas cell. The absorption lines of the reference gas provide a known calibration standard against which measured values may be compared. The invention finds applications in optical transmission systems, including wavelength division multiplexed and dense wavelength division multiplexed (WDM and DWDM) optical communication systems.

Abstract: A passive, temperature compensated tunable filter calibration device for a Bragg grating interrogation system. In a first system, a dual-substrate Bragg grating calibration system, the temperature of an array of gratings is estimated using an array of gratings bonded to a common host substrate and a single grating bonded to a material with a different coefficient of thermal expansion. Changes in a common temperature of the substrates is measured by monitoring the difference between shifts of grating wavelength. As a filter voltage is scanned from its lowest to its highest voltage, the voltages are recorded. The second lowest wavelength corresponds to the grating attached to the differing substrate. The voltages are used to calculate a voltage-to-wavelength function for the scanning range of the filter. To compensate for variations in a calibration curve and temperature variations of the calibration array, the temperature is estimated and function re-calculated at every pass of the scanning filter.

Abstract: An optical channel monitor is described, the optical channel monitor includes an optical input port, a photodetector disposed in an optical path communicating at least intermittently with the optical input port, an optical filter disposed in the optical path between the optical input port and the photodetector, and an optical band splitter disposed in the optical path between the optical filter and the photodetector. The optical filter is a multibandpass filter, such as a scanning Fabry-Perot filter. The optical channel monitor also comprises a reference light system for providing a calibration standard against which an optical signal input through the input port may be compared. The channel monitor finds application in optical transmission systems including wavelength division multiplexed (WDM) optical communication systems.

Abstract: The invention includes a method and apparatus for monitoring wavelength of an optical channel. A tunable optical bandpass filter is used to correlate a signal from an optical transmission line with a signal from a reference light source. The signal from the reference light source passes through a reference gas cell. The absorption lines of the reference gas provide a known calibration standard against which measured values may be compared. The invention finds applications in optical transmission systems, including wavelength division multiplexed and dense wavelength division multiplexed (WDM and DWDM) optical communication systems.

Abstract: A new optical sensing device containing fiber Bragg gratings, a scanning bandpass filter, an interferometer and multiple photodetectors is disclosed. The present invention also describes a new system and method for fibre Bragg grating (FBG) sensor interrogation and multiplexing. The new system combines a scanning Fabry-Perot (SFP) bandpass filter used to wavelength-multiplex multiple gratings in a single fiber, and an unbalanced Mach-Zehnder fibre interferometer made with a 3×3 coupler to detect strain-induced wavelength shifts. A passive technique for interferometer drift compensation using non-sensing FBGs is included in the system. A complete prototype system interrogates four gratings in a single fiber at a Nyquist sampling rate up to 10 kHz, with a noise floor measured near 4 n&egr; Hz−½ above 0.1 Hz. The inclusion of the interferometer drift compensation technique is shown to make quasi-static measurements feasible.