Dear Venkata DINESH Avvari, this free downloadable document may answer your question. My Regards

https://www.hindawi.com/journals/jnm/2012/327369/

Via the link below you will find an overview on the various methods used. My advice is to test all the once you have the resources for and choose the most handy/suitable one.

http://electrospintech.com/thickness-measurement.html

it can be done by the operator of the SEM,

After deposition of Au particle on the nanofibers on the plate, he or she can rotate the root and take images of nanofibers thickness, for example it can varied from 5 micrometer to 250 micrometer depends on the accuracy and precision of instrument

Dear Hamid Sir,

One problem arose when we go below 1 um of optical nanofiber then it broke every time, so how can you properly hold it? Please tell.