Masayuki Morisawa

Plastic optical fibre sensor for detecting vapour phase alcohol

New plastic optical fibre sensors for detecting alcohol vapour have been studied. A certain kind of polymer such as a Novolac resin causes swelling when it is exposed to alcohol vapour. This effect produces a change in the polymer refractive index. Based on this principle, the plastic optical fibre (POF) type sensor head was fabricated by coating Novolac-resin and Novolac/Fe:SO complex film as a cladding layer on the plastic fibre core. When this sensor head was exposed to ethanol and methanol vapour, the light intensity passing through the sensor head changed remarkably depending on the vapour pressure. The sensor response was also found to be fast, stable and reproducible.

New cladding polymer for optical oxygen sensor using fluorescent plastic fiber

Improvement of the optical fiber oxygen sensor based on the fluorescence quenching by oxygen gas was studied. Using the newly synthesized poly-l-methylmethacrylate (PMtMA) and its blend of the PMtMA/PMP as the cladding layer, in which sensing dye was doped, the plastic optical fiber (POF) O2 sensor with high sensitivity and a fast response time could be realized. In addition this sensor didnt receive any affect by humidity.

Improvement of Sensitivity in Plastic Optical Fiber Gasoline Leakage Sensors

Optical fiber sensors for detecting leakage of gasoline have been studied. When exposed to gasoline vapor, certain rubber-type polymers such as polyisoprene cause swelling and their refractive indexes decrease depending on the vapor pressure of gasoline. Based on this effect, the fiber-type sensor heads were fabricated by coating the swelling polymer as a cladding layer on the fiber core with slightly lower refractive index than that of cladding. This sensor head changes its fiber structure from leaky to guided, and then, change in the transmitted light intensity by leakage of gasoline can be observed. The improvement of sensitivity in a wide range of gasoline vapor pressure was attempted.

Plastic optical fiber sensors for detecting leakage of alkane gases and gasoline vapors

New optical fiber sensors for detecting leakage of vapor phase alkanes and gasoline have been studied. When exposed to these vapors, certain rubber-type polymers such as polyisoprene and polyisobutylene cause swelling and their refractive indexes decease depending on the vapor pressure of these substances. Based on this effect, the fiber-type sensor heads were fabricated by coating the swelling polymer as a cladding layer on the fiber core with slightly lower refractive index than that of cladding. When was exposed to vapor phase substances, the sensor head changed its fiber structure from leaky to guided one, and then a large change in the transmitted light intensity was observed in a wide range of the vapor pressure. The response was also found to be reversible and reproducible.

Optical sensing of taste substances using rhodamine-dye-doped LB film

In order to develop a simple sensing system for taste substances, an optical method using an LB film doped with a voltage-sensitive dye was studied experimentally. The blended LB film of arachidic acid and rhodamine B (RBC18) dye with a long hydrocarbon chain, which as a mixture ratio of 75:1, was transferred on to the ITO substrate and was used to measure both the fluorescence intensity around (lambda) f equals 600 nm and the membrane potential of the RBC18-LB film in various taste substance solutions. As a result, for example, it was found that the fluorescence intensity increased as the NaCl concentration increased but on the other hand the membrane potential decreased. The different patterns were obtained for the different taste substance solutions. These experimental results show the possibility of an optical fiber taste substance sensor using blended LB film of arachidic acid and RBC18.

Simple optic sensor for fuel gases

Simple optic sensors for detecting fuel gases, which consist of plastic optical fibers (POFs), have been studied. The sensing mechanism is based on the swelling phenomena in the rubber-type polymers. The POF-type sensor head was fabricated by coating the swelling polymer on the plastic fiber core and was connected to the normal POFs. When this system was exposed to fuel gases such as gasoline and propane, the light intensity passing through the sensor head changed remarkably depending on the pressure of fuel gases. The sensor response was also found to be fast, stable and reproducible.

DO-sensing based on enhancement of cladding fluorescence in dye-doped plastic fiber

A new technique for the optical sensing of dissolved oxygen (DO) is proposed here. It is based on the enhancement in fluorescence yield of TPP dye at (lambda) equals 656 nm, when excited by He-Cd blue laser of (lambda) equals 441 nm in the presence of dissolved oxygen. The sensor head was fabricated by cladding the ARTON fiber core with the poly-4-methyl-1- pentene polymer matrix suitably doped with Tetraphenylporphine dye. This sensor head, when placed in a test chamber and end-pumped by He-Cd laser, generates the intense fluorescence at 656 nm. Its intensity was noticed to increase with increasing the amount of DO. A theoretical model of the sensor response was designed and is also discussed.

Improvement of sensitivity and stability of fiber optic oxygen sensing based on cladding fluorescence

An attempt has been made to improve the sensitivity and stability of optical fiber sensor used for the continuous monitoring of gaseous oxygen. It utilizes the quenching phenomena of cladding fluorescence. Two polymers viz. poly cyclohexyl methylacrylate (PCMA) and poly (4-methyl-1-pentene) (PMP) were selected which were doped with 9,10-diphenyl anthracene (DPA) and sensor head was prepared by dipcoating the polymer on a 4.2 cms length of an especially designed ARTONTM plastic fiber with 1 mm core diameter. For dipcoating, polymer matrix containing 3% wt of fluorescent dye was used. The sensor head thus prepared was tested for various oxygen concentrations varied by mixing nitrogen. D2lamp was used for UV side pumping and thus the fluorescence generated in the cladding was coupled to another plastic optical fiber at the output end. The change in fluorescence due to oxygen content was recorded using a photo-multiplier at the (lambda) equals 430 nm. The results obtained have been tabulated in the form of comparative studies. The response was found to be fast, reversible and reproducible with recovery time of the order of few seconds in both the cases. The sensors were found to detect a wide range of oxygen concentration ranging from 0.5% to 100% of O2. In the case of PCMA, better stability in long-term was observed. The effect of cladding thickness on the sensor performance was also explored.