A monolithically integrated optic triplexer is described herein that can be mounted in one transistor outline (TO) can and can be used in a passive optical network. The monolithically integrated optic triplexer includes: an emitting laser; at least a first photodiode that is capable of receiving an optical signal; and a thin film filter that is located between the emitting laser and the first photodiode. In addition, the monolithically integrated optic triplexer may include a thin film filter that is located between the first photodiode and a second photodiode. Also described herein is a method for making the monolithically integrated optic triplexer.