Fluorescein isothiocyanate (FITC)  is the original fluorescein molecule functionalized with an isothiocyanate reactive group (-N=C=S), replacing a hydrogen atom on the bottom ring of the structure. It is the most common fluorescent reagents for biological research because of their high absorptivity, excellent fluorescence quantum yield, and good water solubility.FITC has excitation and emission spectrum peak wavelengths of approximately 495 nm/519 nm.

Optolong Optics Co.,ltd is the brand owner of optolong who is a manufacturer of astronomy filters, fluorescence filters. We also offer other interference filters like UV filters, visible filters and Near inferred filters, beam splitter, anti-reflection coating and optical mirrors as a OEM service.

Located in Kunming city in China which is one of the four optics center and the coating experience of 18 years (since 1999) enable us to design and produce the filters with most sophisticated spectrum.

We are glad to declare that Optolong has been become the first and only non-replaceable brand for astronomical filters in China. Optolong brand is also known as the comparable filters with international brand by distributor client around the world.