An optical module includes a fiber array, a laser diode array and a photodiode array. The fiber array has optical fibers which are divided to a transmitter group and a receiver group. The laser diode array has laser diodes which are grouped in a transmitter group. The photodiode array has photodiodes which are divided to a monitor group and a receiver group. The laser diode array is provided between the fiber array and the photodiode array. Each optical fiber of the transmitter group, each laser diode of the transmitter group and each photodiode of the monitor group are optically aligned, respectively. Each optical fiber of the receiver group is optically aligned with each photodiode of the receiver group, respectively.