Preparation of dual mode spectroscopic system for testing: Analysis of sample holder and investigation of intensity noise.

Absorption spectroscopy is combined with the principle of multiple wavelengths to develop a biomedical sensing mechanism, laid by two Fibre Bragg Gratings. It is essential to incorporate a sample holder in the setup in which the substances can be tested, necessitating its complete investigation without and with the holder, in both directions. The average losses of the fibre junctions are 0.44 and 0.18 dB, respectively, with accuracy of ±0.2 dB which lies within the intensity profile specified by the manufacturer (0.3 dB). Next, the spectral profiles and its respective factors (slope, threshold, mode spacing, intensity levels) of both systems are compared and thoroughly investigated on technical grounds, to examine any anticipated issues for the sensor's operation. Afterwards, we place the holder in the laser setup and check its efficiency by comparing it the intensity profiles of the system without it, under identical parametric values. The average Relative Intensity Noise is found to be consistently low and analogous in both setups, with scientific justifications. Repetition in the forward and reverse directions, and swapping the positions of the lenses, the outcomes show homogenous patterns, which provides conclusive approval with specified parametric regulations in this work.