Resumen
In the preceding years, the research society and genuine users have enabled to increase the consideration of Passive Optical Networks. Several authors discussed the various wavelength allocation techniques for different layers. This paper provides a detailed study about all the existing wavelength allocation techniques and also explains about limitations available in the techniques. Wavelength allocation includes 1524-1544 nm in upstream direction and 1596-1602 nm in downstream direction. Finally, this paper concludes with insights for research techniques about wavelength allocation in Passive Optical Networks.