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Fiber Sensor Integrated Monitor (FSIM)

The FSIM is a low power high speed Fiber Bragg Grating interrogation system. Fitting in the palm of a hand this system is able to deliver real-time measurements. Revision II of the FBG interrogation system is being developed and promises to deliver speeds of up to 100 kHz, while still maintaining it's small size and low power requirements.

Power Consumption:Less than 1.5 Watts
Spectral Range:~1515 - 1610nm

Optical fiber sensors are finding increased application as smart sensors because of their relatively high immunity to environmental phenomena and small size. While much research is focused on developing and applying new optical sensing technologies, there is also a great need for better fiber sensor interrogators. Fiber sensor interrogators differ from traditional sensor interrogators in that the demodulation of the sensor requires measurement of optical phenomena rather than electrical phenomena such as a voltage or current. For example, the figure below shows the transmission and reflection spectrum of an array of fiber Bragg grating (FBG) sensors. Each individual FBG sensor reflects a narrow band of wavelengths at the Bragg wavelength, allowing the remaining optical power to be transmitted. The wavelength of this reflected band, or peak, shifts in the presence of different environmental phenomena, such as temperature or strain. Therefore, sensor interrogation requires the measurement and analysis of the wavelength spectrum. Similar wavelength-based sensor interrogation is also required for other optical sensors, such as Fabry-Perot and long period grating sensors.

Many optical sensor monitoring systems are large and bulky, costly, have high power consumption, and perform only the most basic functions. Thus while the sensor itself can be extremely compact and adaptable to a variety of situations, the interrogation system is not. The goal of the FSIM project at BYU is to create a new fiber sensor monitoring system that is specifically designed for embedded instrumentation applications. Not only will this system need to be smaller, lighter, and consume less power, it will require enhanced "smart" features that will enable it to respond to commands and easily network with other sensor systems.

The figure below shows a size comparison of 3 different fiber sensor monitoring systems. The first is a typical optical spectrum analyzer (OSA), which is quite large and bulky and has lots of functionality that is unnecessary for standard sensor monitoring. The second system is a state of the art fiber Bragg grating interrogator made by Micron Optics. It was designed specifically for fiber sensor applications and is much more similar in functionality to the FSIM. The third system is the current version of the FSIM system.

As a smart sensor, the FSIM system not only measures standard wavelength spectrums, it can also be operated in an adaptable configuration. For example, it can zoom in and scan specific spectral locations, track multiple peaks, etc. This simple embedded data processing can also have a dramatic impact on the data size and acquisition time by analyzing the data and transmitting only the desired parameter such as strain or temperature rather than simply sending the entire wavelength spectrum. It also has the capability to perform self calibration, communicate directly with the data network to vary the rate and interval of the measurement time, and convert the data into the correct digital format to be placed onto a data bus.
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