Intrinsic fiber optic chemical sensor for the detection of dimethyl methylphosphonate

1-5 Napthalenedisulphonic Acid Doped Polypyrrole thin films as Coatings to Optical Fibers for Organophosphate Sensing

“…The light transmission through the fiber sensing elements were tested for the influence of temperature. It was reported earlier that there is a light power transmission decrease as the temperature is increased from room temperature (25°C) to (50°C) as seen in figure 15a [33]. Four probe resistivity measurements on the polypyrrole thin films, shown in figure 15b.…”

“…Four probe resistivity measurements on the polypyrrole thin films, shown in figure 15b. This decrease in output power is attributed to the decrease in the resistivity of doped polypyrrole films upon temperature increase [33][34][35][36]. Thermal stability of the polypyrrole films is reported to have improved by incorporation of aromatic dopants such as anthraqunione-2-sulphonic acid in polypyrrole [37].…”

A novel optical aerosol detector utilizing an optic fiber with conductive polymer coating

“…2b. The optical fiber PMMA core has a refractive index of 1.48, and the refractive index of the PPy nanofilm is approximately 1.817 (Khalil et al, 2004), which is much higher than those of the PMMA core and air (1.0) and satisfies the total internal reflection. As shown in Fig.…”

Volatile Organic Compound Optical Fiber Sensors: A Review

“…In most of them, there is a segment of the fiber that acts as the sensing area, so there is no open path between the light source and the detector. The passive cladding of the optical fiber is replaced, using different schemes, along a small section by a sensitive material; so any change in the optical or structural characteristic of the chemical dye due to the presence of the vapors, provokes a change in the effective index of the optical fiber, changing its transmission properties [27]. The sensitivity of these sensors depends on the optical power transferred into the evanescent field and also by the penetration depth of these waves into the sensing cladding, which can be calculated by Beer-Lambert law [28].…”

“…In this case, the sensor response is governed by the intensity modulation caused by light absorption of the evanescent wave which is guided through the cladding; this interaction results in the attenuation of the guided light in the fiber core [29]. On the other hand, if the modified cladding has a higher refractive index than the core, part of the optical power is refracted into the cladding, and another part is reflected back into the core [27]. Both the optical power reflected in the core and the light passing through the cladding depend on the optical properties of the cladding, which change in presence of the organic vapors to be detected.…”