1：Experimental Design and Method Selection:

The study designed a macro-bend fiber sensor coated with agarose gel for humidity and temperature sensing. The working principle is based on macro-bend loss theory and whispering-gallery mode (WGM) at the interface between cladding and coating. The sensor's performance was evaluated by measuring wavelength shifts and intensity variations in response to humidity and temperature changes.

2：Sample Selection and Data Sources:

A single mode fiber (Corning SMF-28e) was used as the sensor substrate. Agarose gel (A6013 from Sigma Aldrich) was prepared as the coating material. Data were collected from transmission spectra using an optical spectrum analyzer (OSA) under controlled humidity and temperature conditions in a climatic chamber.

3：List of Experimental Equipment and Materials:

Equipment includes a mid-infrared super-continuum (SC) source (AdValue Photonics AP-SC-MIR), climatic chamber, optical spectrum analyzer (OSA) (Yokogawa AQ6375B), magnetic stirring apparatus, and Norland Optical Adhesive 61. Materials include agarose powder (Sigma Aldrich A6013), distilled water, absolute alcohol, and single mode fiber (Corning SMF-28e).

4：Materials include agarose powder (Sigma Aldrich A6013), distilled water, absolute alcohol, and single mode fiber (Corning SMF-28e). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The agarose gel was prepared by dissolving agarose powder in distilled water and stirring at 65°C for 30 min. The fiber was cleaned with alcohol, coated with agarose gel via dip coating, dried at room temperature for 24 h, bent into a necktie structure, and fixed on glass with adhesive. The sensor was placed in a climatic chamber, and transmission spectra were recorded using the SC source and OSA while varying humidity (40–95% RH at 25°C) and temperature (20–50°C at 50% RH). Human breath monitoring was also conducted by placing the sensor near the nose.

5：Data Analysis Methods:

Wavelength shifts and intensity variations in transmission spectra were analyzed to determine sensitivities to humidity and temperature. Linear and polynomial fits were applied to the data, and response/recovery times were calculated from human breath experiments. Stability was assessed by monitoring wavelength variations over time at fixed humidity levels.