A zinc-oxide deposited excessively tilted fibre grating sensor was used for ambient refractive index sensing and encouraging sensitivity was recorded. But i need to know the resolution of this sensor bearing in mind that the instrument used to monitor the optical characteristic is an optical spectrum analyzer at a resolution of 0.05nm. Many thanks.
In nm your resolution will 0.05 or the minimum wavelength change you can measure if higher.
In refractivity which has no unitd it will be the minimum wavelength x the slope assuminh refractivity is on thr y axis.
I don't know if you could work with solution samples. If yes, then you could work with different concentrations of sucrose or glycerol or salt in water. These solutions have different refractive indices depending on the concentration.
Make solutions of different refractive indices ensuring that the values are as close as possible and measure their RI using your instrument. Thus you can experimentally determine the resolution of your setup.
I assume you achieve your sensing from the shift of the resonances of your fiber grating. From your experimental results, you can calculate how much refractive index change results in a resonance shift of 0.05 nm. That will be your resolution, provided that there is no other equipment / phenomena that further limit your resolution.
First you need to come up with a plot of the wavelength shift of your sensor (y-axis) versus the index of refraction (x-axis): use preferably five to six different indices of refraction (you can use different sucrose solutions like Kishore mentioned). The slope of this graph is your sensitivity: if the graph is linear, the sensitivity is constant otherwise the sensitivity will be variable. The resolution of your sensor will be 0.05nm divided by the sensitivity. That is one way of doing it.
Another way is to find out what is the refractive index difference that you can measure for a 0.05nm wavelength shift. The first method is simpler, of course...
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