Do you mean energy transfer? Because when you say  "use a fluorophore emission radiation as a excitation source for another one" it means re-absorption of light.

You may go though the topic multi-colour FRET

http://www.sciencedirect.com/science/article/pii/S0006349504736127?via%3Dihub

http://onlinelibrary.wiley.com/doi/10.1002/cphc.200400261/abstract;jsessionid=27F1302B8AE412D358AE417EAB840FD5.f03t01

http://pubs.rsc.org/en/Content/ArticleLanding/2005/PP/b416478d#!divAbstract

https://www.nature.com/nmeth/journal/v7/n10/full/nmeth.1502.html

http://pubs.acs.org/doi/abs/10.1021/nn304736j

If the distance between the two fluorophores is close enough, the phenomenon known as fluorescence resonance energy transfer (FRET) can result. The second fluorophore (acceptor) is excited by the excitation energy from the first one (donor) in a radiationless process (i.e. no photon is emitted by the first fluorophore). This is a commonly used technique. The selection of the fluorophores and the distance between them (as short as possible) are the most important factors. Companies that supply custom oligonucletoides can attach the fluorophores and quenchers for you, at substantially increased cost compared with unlabeled oligos.

I thought the F in FRET stood for Forsters instead of fluorescense. Anyway thank you very much.

By the way Adam, upon which distances FRET happen?? 20 nm is a short enough distance??

The F in FRET can also mean Forster, after the person who developed the theory. Sometimes the F is omitted.

20 nm is too far. 2 nm would be in the right range. In practice, this means that the donor and acceptor should not be at opposite ends of the DNA, unless it is very short. I have had good success with FRET using double stranded DNA in which the 5' end of one strand and the 3' end of the other were labeled, so that the donor and acceptor were right next to each other.

Do a simple experiment. Mix the emitting fluorophore withe one that is to be excited, either in solution or on a solid phase both dry and wet,  and see if the receptor fluorphore is excited by the emitting flurophore. If it works then just do your hybridisation experiment.

As mentioned by by Adam and Wahab, FRET stands for Forster resonance  energy transfer. In case of fluorescent chromophores, it is also abbreviated for fluorescence resonance energy transfer also. FRET efficiency depends on critical transfer distance as well as on donor acceptor distance (sixth power). Critical transfer distance depends on the overlap of donor emission and acceptor absorption. In your case FRET should be there but as the distance between donor and acceptor the efficiency will be too small.There is plenty of literature in this topic. Again as there is overlap between donor emission and acceptor absorption, the emitted photons from donor will be absorbed by acceptor. This is called radiative transfer. As mentioned by Wahab, there is no change in donor lifetime but the donor fluorescence spectrum shows successive shift with increase in acceptor concentration.

OK thank you all for your your answers. May I ask you something besides? I am searching an alternative FRET pair to Fluorescein that is not rhodamine or a derivative like TAMRA. Which one do you recommend me?

The company Dyomics supplies a range of dyes that can be excited by the fluorescence emission of fluorescein.  In particular the long stokes shift dyes are useful as their fluorescence is easily distinguished from that of fluorescein . They can be obtained with a range of different reactive groups for coupling to other molecules