Your question Dear Xiaojing Xia, is akin to asking what the end values are if one knows the birefringence of a given unknown mineral particle. If that is correct then I completely agree with those who say you can not pin down the RI of core and/or cladding. On the other hand, if an optical microscope is available you could grind some up and examine it to discover the RI of both materials ... if it makes sense to snip off a sample of a given fiber.

Your question may well be addressed by applying my specialty, about which you can learn more by visiting at least these four (4) files,

1. Preprint#4: https://tinyurl.com/y76yba6n

(Click Download to get 4 May 2020 PREPRINT#4)

2. Raw data: https://tinyurl.com/v9u4hkf

3. Video: https://tinyurl.com/uajcnxx (open in a video player)

4. 20200512 1325 Final E% COORDINATES & MORE .pdf, https://tinyurl.com/y9lrmnec

and maybe also by paying a visit to some of the other Supplemental Materials in folder https://tinyurl.com/to8tsbt .

I hope that this helps and that you will, in turn, share with me any thoughts you may have about how I could improve any aspect of my work.

With all best wishes for your own continuing successes! :-)

Sincerely, -Steve- [email protected]

P.S. Then, too: You could contact the manufacturer and ask your questions. ;-)

-s-

Check polarization variation, for transmitting radiation, by help bending the fiber

Hi,you can see these links:

Fiber opticArticle Fiber optic sensing of liquid refractive index

Article Absolute Measurement of the Nonlinear Refractive Indices of ...

Mark L. Gurari (Gourari) and Ban A. Naser, thanks for you answers about some experimental methods. I'd like to clarify my question more. I want to learn if I can get the absolute refractive index (n) from the known refractive differences (Δ n), and how? I attached an example figure with Δ n vs. radius here.

Looking at the picture the first mind is: You can measure reflective diffraction of the end of the fiber and such a way to get absolute value of the n.

My answer would be: no, you cannot. At least not with just the information on the difference provided, as the difference is just one value made out of two source values in which you are interested in. If you any other information on one of these source values, then it becomes easy, of course. For example the fiber type and a description of the glass, like undoped silica for the cladding (standard fibers) or radiation tolerant fibers (undoped silica core).

If you have access to a sample, you can measure it by yourself...

NA/2 = sqrt(n2^2-n1^2)=sqrt[(n2-n1)*(n2+n1)];

So,

n2+n1=(NA/2)^2 /delta(n);

I don't think you can invert the absolute value of n from the del_n between the core and cladding. But would it not suffice, at least for a first order back of envelope calculation, to look up the complex N=n+ik of the material in an optics handbook or some applied optics literature? Hope this helps.

To calculate the value of n from delta_n, you definitely need either the core index or the cladding one. However, the manufactures in their data sheets and authors in there papers usually don't provide this information.

For an optical fiber, one of the requirement for guiding of light is the refractive index contrast between the core and the cladding. This refractive index contrast can be obtained by variety of means, for example, by Ge-doped core with pure silica cladding, F-doped cladding with pure silica core, or a combination of both. Unless you are not sure about these approaches in a particular design, there is no way to obtain the exact refractive index values of the core and cladding from delta_n data.

Your question Dear Xiaojing Xia, is akin to asking what the end values are if one knows the birefringence of a given unknown mineral particle. If that is correct then I completely agree with those who say you can not pin down the RI of core and/or cladding. On the other hand, if an optical microscope is available you could grind some up and examine it to discover the RI of both materials ... if it makes sense to snip off a sample of a given fiber.

Your question may well be addressed by applying my specialty, about which you can learn more by visiting at least these four (4) files,

1. Preprint#4: https://tinyurl.com/y76yba6n

(Click Download to get 4 May 2020 PREPRINT#4)

2. Raw data: https://tinyurl.com/v9u4hkf

3. Video: https://tinyurl.com/uajcnxx (open in a video player)

4. 20200512 1325 Final E% COORDINATES & MORE .pdf, https://tinyurl.com/y9lrmnec

and maybe also by paying a visit to some of the other Supplemental Materials in folder https://tinyurl.com/to8tsbt .

I hope that this helps and that you will, in turn, share with me any thoughts you may have about how I could improve any aspect of my work.

With all best wishes for your own continuing successes! :-)

Sincerely, -Steve- [email protected]

P.S. Then, too: You could contact the manufacturer and ask your questions. ;-)

-s-

If you any other information on one of these source values, then it becomes easy, of course. For example the fiber type and a description of the glass, like undoped silica for the cladding (standard fibers) or radiation tolerant fibers (undoped silica core).

I also agree with Stephen answer

Your question can not apply, because of the core and cladding have different n-values. Absolute value of (n) means the change velocity of wavelength in these material. Absolute value can be occur when we using pure material.