On the pH response of fiber optic evanescent field absorption sensor having a U-shaped probe: An experimental analysis

Pankaj Kumar Choudhury, Toshihiko Yoshino

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

An investigation is made of the response of fiber optic evanescent field absorption sensors in respect of the concentration of dye as well as its pH value. Patent blue VF dye is chosen as the measurand sample, and it is found that the evanescent absorbance of the dye is a nonlinear function of dye concentration, which is in contradiction with the theory of Beer-Lambert law of absorption, which states that the absorbance of the sample is linearly related to the sample concentration. Further, it is also observed that the degree of nonlinearity is a function of the pH value of the measurand sample; it (the nonlinearity) decreases with the decrease in sample pH. The reason is attributed to the accumulation of positively charged chromophores on the bare silica surface of the fiber in the case of higher pH values. Justification of it is also made on the basis of the results obtained through free-beam method. A U-shaped sensor probe is used for the investigation because the sensitivity of the system improves due to the higher penetration depth achieved in this case; this is experimentally shown too.

Original languageEnglish
Pages (from-to)13-18
Number of pages6
JournalOptik (Jena)
Volume114
Issue number1
Publication statusPublished - 2003
Externally publishedYes

Fingerprint

Evanescent fields
Fiber optics
fiber optics
Coloring Agents
Dyes
dyes
probes
sensors
Sensors
nonlinearity
Bouguer law
Chromophores
Silicon Dioxide
patents
Silica
chromophores
penetration
Fibers
silicon dioxide
fibers

Keywords

  • Chemical sensors
  • Evanescent wave absorption
  • Fiber optic sensors

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

On the pH response of fiber optic evanescent field absorption sensor having a U-shaped probe : An experimental analysis. / Choudhury, Pankaj Kumar; Yoshino, Toshihiko.

In: Optik (Jena), Vol. 114, No. 1, 2003, p. 13-18.

Research output: Contribution to journalArticle

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