Low-cost high-performance fiber-optic pH sensor based on thin-core fiber modal interferometer

Abstract

A new fiber-optic pH sensor based on a thin-core fiber modal interferometer with electrostatic self-assembled nanocoating is presented. After inserting a segment of thin-core fiber into a standard single-mode fiber, high-order cladding modes are excited and interfere with the core mode to form an in-fiber modal interferometer. The side surface of the sensor is then deposited with poly(allylamine hydrochloride) and poly(acrylic acid) nanocoating by electrostatic self-assembly technique. A fast and linear response is obtained in either acid or alkali solution (in the pH range 2.5 to 10) with resolution of 0.013 pH unit.

Design of Nanostructured Functional Coatings by Using Wet-Chemistry Methods

“…An important consideration is that the optical fiber field has shown a considerable growth thanks to the implementation and development of nanostructured thin films onto diverse optical fiber configurations. These nanostructured coatings make possible an enhancement in the response time as well as in the resultant sensitivity [114][115][116][117][118][119][120][121]. In addition, the presence of nanoparticles in these sensitive thin films has resulted in the design of high-performance fiber-optic sensors due to the inherent properties of the nanoparticles such as high surface area ratio and porosity [122][123][124][125][126].…”

“…Layer-by-layer assembly pH (range 4-7); Good repeatability and high sensitivity [114] Layer-by-layer assembly Fast and linear response in either acid or alkali solution (pH range 2.5 to 10); Resolution of 0.013 pH unit [115] bacteriostaticity and sensorics. The design of superhydrophobic surfaces for metallic alloys and fabrics has been successfully obtained by the sol-gel process involving hybrid or single silica matrices combined with water-repellent precursors.…”

Nanostructured Materials in Optical Fiber Sensing

“…In [24] the well known poly(allylamine hydrochloride) / poly(acrylic acid) (PAH/PAA) structure [25][26][27][28] is deposited onto an optical fiber tip to create a pH-sensitive nanocavity.…”

Salinity sensor based on polyimide-coated photonic crystal fiber

“…In addition to the unique features reported in [1][2][3], PCFs also possess the advantages of conventional optical fibers in sensing applications such as EMI immunity, compact size, corrosion resistance, light weight, multiplexing capability, etc. Optical fiber sensors are also attractive for in situ monitoring of different physical, chemical, and biological parameters, e.g., strain [4,5], temperature [6], refractive index [7], pH [8], relative humidity [9,10], and water salinity [11][12][13][14][15][16][17][18]. Salinity sensors play an important role in manufacturing process control and protection of ecosystems.…”