Deteksi Gas Amonia Berbasis Struktur Serat Optik SMS (Singlemode-Multimode-Singlemode)

Manurung, Johannes Vanreen (2026) Deteksi Gas Amonia Berbasis Struktur Serat Optik SMS (Singlemode-Multimode-Singlemode). Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Penelitian ini bertujuan untuk mengkarakterisasi dan menganalisis kinerja sensor gas amonia berbasis serat optik dengan konfigurasi Singlemode Multimode Singlemode (SMS) dalam kondisi tanpa Coating. Prinsip deteksi memanfaatkan interaksi langsung antara medan evanescent dari cahaya yang merambat dalam MMF dengan molekul amonia (NH₃) yang teradsorpsi pada permukaan cladding silika (SiO₂) yang terekspos. Interaksi ini mengubah indeks bias efektif lokal, yang kemudian memodulasi pola interferensi multimode dan menghasilkan pergeseran spektrum transmisi yang dapat diukur menggunakan Optical Spectrum Analyzer (OSA). Hasil eksperimen menunjukkan bahwa sensor mampu mendeteksi amonia dengan memantau pergeseran dua lembah interferensi (dips) utama dalam spektrum. Lembah pertama (sekitar 1513 nm) menunjukkan red-shift dengan sensitifitas pergeseran panjang gelombang sebesar 0.0495 nm/mL namun disertai pelemahan intensitas (-0.4747 dBm/mL), mengindikasikan peningkatan indeks bias sekaligus hamburan optik. Sebaliknya, lembah kedua (sekitar 1578 nm) menunjukkan red-shift dengan sensitifitas lebih tinggi (0.1405 nm/mL) dan diiringi peningkatan intensitas (+0.2486 dBm/mL). Kesimpulan penelitian ini menegaskan bahwa konfigurasi SMS tanpa coating berhasil berfungsi sebagai sensor amonia melalui mekanisme transduksi fisis fundamental. Kinerja optimal dicapai dengan memantau lembah kedua, yang menawarkan sensitifitas lebih tinggi dan sinyal yang menguat. Penelitian ini memberikan landasan penting bagi pengembangan sensor serat optik yang sederhana, berbiaya rendah, dan mengungkap kompleksitas dinamika interferensi multi moda yang kaya akan informasi. ======================================================================================================================================
This study aims to characterize and analyze the performance of an ammonia gas sensor based on an optical fiber Singlemode-Multimode-Singlemode (SMS) configuration in an uncoated (cladding-stripped) condition. The detection principle utilizes the direct interaction between the evanescent field of light propagating within the Multimode Fiber (MMF) and ammonia (NH₃) molecules adsorbed onto the exposed silica (SiO₂) surface. This interaction alters the local effective refractive index, subsequently modulating the multimode interference (MMI) pattern and resulting in a measurable transmission spectrum shift via an Optical Spectrum Analyzer (OSA). Experimental results demonstrate that the sensor effectively detects ammonia by monitoring the shifts of two primary interference dips in the spectrum. The first dip (centered around 1513 nm) exhibits a red-shift with a wavelength sensitivity of 0.0495 nm/mL, accompanied by an intensity attenuation of -0.4747 dBm/mL, indicating an increase in the refractive index alongside optical absorption/attenuation. Conversely, the second dip (centered around 1578 nm) shows a higher red-shift sensitivity of 0.1405 nm/mL, accompanied by an intensity enhancement of +0.2486 dBm/mL. This research confirms that the uncoated SMS configuration functions successfully as an ammonia sensor through fundamental physical transduction mechanisms. Optimal performance is achieved by monitoring the second dip, which offers superior sensitivity and signal amplification. This study provides a vital foundation for developing simple, low-cost optical fiber sensors while uncovering the complex and information-rich dynamics of multimode interference.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Amonia, Cladding fiber optic, Medan evenescent, Silika, SMS fiber optic. Ammonia, Cladding fiber optic, Evanescent Wave, Silica, SMS fiber optic.
Subjects:	T Technology > T Technology (General) > T55 Industrial Safety T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK6592.O6 Optical radar
Divisions:	Faculty of Science and Data Analytics (SCIENTICS) > Physics > 45201-(S1) Undergraduate Thesis
Depositing User:	Johannes Vanreen M
Date Deposited:	03 Feb 2026 08:44
Last Modified:	03 Feb 2026 08:44
URI:	http://repository.its.ac.id/id/eprint/132028

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