There are other approaches, but they have significant drawbacks: Fbg interrogator thesis FBGs are at distinctly different nominal center wavelengths from their neighbors, and the interrogator uses these unique FBG wavelengths to keep track of which sensor is which.
External cavity tunable lasers are slow, expensive, and do not have a wide operating temperature Fbg interrogator thesis or the required mechanical robustness.
They lack the speed, compact size, and usability necessary to move into mainstream test and measurement. Wesley Mont Kunzler, Brigham Young University - Provo Follow Abstract Spectrally-based fiber optic sensors are a rapidly maturing technology capable of sensing several environmental parameters in environments that are unfitting to electrical sensors.
The actual translation is given by the gage factor supplied with the FBG sensor. This method cannot achieve the required wavelength measurement repeatability and resolution with commercially available diode arrays.
By dramatically increasing speed, shrinking size, and targeting an interface that can be used in large-scale industrial interrogation systems, spectrally-based fiber optic sensors can now find more widespread use in both research labs and industrial applications.
Time division multiplexing TDM systems use the known speed of light in the fiber to discern which signal is reflected from which FBG along the fiber path. Laboratory OSAs are large, slow, expensive, and do not have a wide operating temperature range.
Multi-line wavelength meters acquire data at slow speeds only, and are not mechanically robust. Light is sent into a fiber and reflects back from the FBG. Sensor capacity on each fiber is determined by the range that each sensor will measure and the total spectral range of the instrument.
When more than one FBG is present on a fiber this is often the casethe instrument will use one of two schemes to discriminate between one FBG and the next.
Polarization properties of the narrow line lasers may not be an ideal match for all sensing applications. Minimum physical grating spacing limits some applications. However, the sensor interrogation systems for this type of sensors are not yet fit to replace conventional sensor systems.
The technology developed in this thesis was demonstrated by producing two advanced interrogators: WDM ranges are now very large and can also accommodate more than sensors per fiber.
The most utilized scheme is wavelength division multiplexing, or WDM. Wavelength information is converted to engineering units, e. This coupled with the high dynamic range of the instrument make the system much more flexible for measurements over tens of kilometers of fiber.
The addition of power meters and wavelength meters add to the bulk, complexity, and cost, as well as reduce reliability and speed. Here are the basics. Theoretically, or more FBGs can be on the same fiber at the same nominal center wavelength.Fig. Chirped fiber Bragg gratings. The refractive index of the core has a linear increasing or decreasing variation of the grating period.
. Spectrometers based on linear detector arrays have proven to be capable of precisely monitoring fiber Bragg grating (FBG) signals. However, anti-aliasing inherently is only poorly integrated.
Thus, these devices do not suffice for providing a reliable anti-aliasing in critical applications like real-time structure control. An optical interrogator, also known as measurement unit or data acquisition system, is an optoelectronic instrument, which allows the reading of optical fiber Bragg grating (FBG) sensors in static and dynamic monitoring applications.
the FBG and the output is a convolution between the spectrum of the tunable filter and that of the FBG, or a charge coupled device (CCD) spectrometer  . Technically, an edge filter functions as a static frequency discriminator to convert the wavelength shift into an intensity change or an intensity spatial displacement.
The WIDE Spectra is a multi-wavelength spectrum analyzer, with high spectral resolution and wide measurement bands. This compact and robust device coupled with a SLED source is a new FBG interrogator solution offering high multiplexing and high sensitivity possibilities in a very compact package.
The technology developed in this thesis was demonstrated by producing two advanced interrogators: one that was one half the size of commercially available systems, and one that accelerated live spectral capture by one thousand times – both of which were operated by non-developers with little training.Download