Compact multi-period offset-spliced SMO-LPFG for ultralow-crosstalk dual-parameter sensing

Area of Science:

• Photonics and Optical Sensing
• Fiber Optic Sensors
• Biomedical and Chemical Sensing

Background:

• Temperature fluctuations cause spectral drift, limiting the precision of surrounding refractive index (SRI) sensors.
• Accurate SRI measurements are crucial for various applications, including environmental monitoring and medical diagnostics.

Purpose of the Study:

• To propose and demonstrate a compact single-mode-multimode offset-spliced long-period fiber grating (SMO-LPFG) sensor.
• To achieve high sensitivity and low temperature crosstalk for accurate SRI sensing.
• To enable simultaneous decoupling of SRI and temperature for multiparameter measurements.

Main Methods:

• Fabrication of a compact SMO-LPFG using three periods of SMF-MMF offset splicing (20µm lateral offset, 2.4mm device length).
• Analysis using beam-propagation simulations and experimental validation.
• Application of a sensitivity matrix approach for data analysis.

Main Results:

• The SMO-LPFG sensor demonstrated SRI sensitivities of 14.5 nm/RIU and 217.88 nm/RIU.
• A temperature sensitivity of 105 pm/°C was recorded.
• An ultralow temperature crosstalk of 2.04 × 10^-5 RIU/°C was achieved.

Conclusions:

• The developed SMO-LPFG sensor effectively mitigates temperature-induced spectral drift.
• The sensor's high sensitivity, low crosstalk, and ability for simultaneous SRI and temperature decoupling make it suitable for high-precision sensing.
• The simple fabrication and compact design enhance its attractiveness for practical multiparameter sensing applications.