Apparatus comprising: a heat sink, the heat sink comprising: a body formed out of a heat-transmissive material; at least one channel extending through the body, the at least one channel having an inlet port and an outlet port; at least one opening extending through the body, the at least one opening being configured to receive an optical module therein; at least one securement element mounted to the body for releasably securing an optical module within the at least one opening; and at least one alignment element mounted to the body for ensuring appropriate alignment of an optical module received in the at least one opening.