One of the most common methods of joining two pieces of optical glass is epoxy bonding. The two pieces of glass are coated with optic epoxy, brought together, and the epoxy is cured by applying heat, UV light or both. Some epoxy can also be cured in room temperature by time (some takes over 24 hours). Epoxy bonding is pretty reliable and the practice is manufacturing friendly since it is an inexpensive process with high yield and that is why it has been widely used in fiber optic active and passive components manufacturing.