There is provided an optical module incorporating active elements such as light emitting devices or photo detective devices mounted on a single substrate. The optical module can suppress optical and electrical crosstalk by a blocking trench formed between the active elements for blocking optical and electromagnetic waves, and a metal barrier formed within the blocking trench for blocking the optical and electromagnetic waves. Further, the optical module can suppress the optical and the electrical crosstalk due to the optical and the electromagnetic waves directed upward the substrate by a housing body enclosing the substrate, a housing cover provided on the housing body, and a metal slit formed below the housing cover and above the metal barrier.