refractive index from joint loss

[vinodquilon]

two compatible MM SI fibers joined with small air gap.
If joint loss is 0.47dB , how can I find refractive index of perfectly aligned fiber ?

 

[killivolt]

two compatible MM SI fibers joined with small air gap.
If joint loss is 0.47dB , how can I find refractive index of perfectly aligned fiber ?

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https://www.compeng.dit.ie/staff/tfreir/optical_1/Unit_1.10.pdf