An optical measurement apparatus comprising: a source of optical electromagnetic radiation; an optical detector; a beamsplitter; and a combined input and output port arranged to permit, when in use, propagation of optical electromagnetic radiation therethrough; wherein the beamsplitter is aligned within a housing with respect to the optical source, the optical detector and the combined input and output port in order to direct optical electromagnetic radiation emitted by the optical source to the combined input and output port and to direct optical electromagnetic radiation received from the combined input and output port to the optical detector; the apparatus characterised by: a bidirectional optical transceiver component providing the housing, the source of optical electromagnetic radiation, the optical detector, the beamsplitter and the combined input and output port; wherein the housing has a first side wall, a second side wall and comprises the combined input and output port; the source of optical electromagnetic radiation is sealingly coupled to the first side wall; the optical detector is sealingly coupled to the second side wall; a single optical waveguide is sealingly coupled to the combined input and output port at a first end thereof, and a second end of the optical waveguide has a surface that extends at a substantially non-perpendicular angle with respect to a longitudinal axis of the optical waveguide; an optical launch assembly is disposed at the second end of the optical waveguide and comprises a length of propagation medium abutting the second end of the optical waveguide, a refractive index of the length of propagation medium being arranged substantially to match a refractive index of the optical waveguide; and the beamsplitter is arranged to direct more than 50% of the received optical electromagnetic radiation from the combined input and output port towards the optical detector. a source of optical electromagnetic radiation; an optical detector; a beamsplitter; and a combined input and output port arranged to permit, when in use, propagation of optical electromagnetic radiation therethrough; wherein the beamsplitter is aligned within a housing with respect to the optical source, the optical detector and the combined input and output port in order to direct optical electromagnetic radiation emitted by the optical source to the combined input and output port and to direct optical electromagnetic radiation received from the combined input and output port to the optical detector; the apparatus characterised by: a bidirectional optical transceiver component providing the housing, the source of optical electromagnetic radiation, the optical detector, the beamsplitter and the combined input and output port; wherein the housing has a first side wall, a second side wall and comprises the combined input and output port; the source of optical electromagnetic radiation is sealingly coupled to the first side wall; the optical detector is sealingly coupled to the second side wall; a single optical waveguide is sealingly coupled to the combined input and output port at a first end thereof, and a second end of the optical waveguide has a surface that extends at a substantially non-perpendicular angle with respect to a longitudinal axis of the optical waveguide; an optical launch assembly is disposed at the second end of the optical waveguide and comprises a length of propagation medium abutting the second end of the optical waveguide, a refractive index of the length of propagation medium being arranged substantially to match a refractive index of the optical waveguide; and the beamsplitter is arranged to direct more than 50% of the received optical electromagnetic radiation from the combined input and output port towards the optical detector. a bidirectional optical transceiver component providing the housing, the source of optical electromagnetic radiation, the optical detector, the beamsplitter and the combined input and output port; wherein the housing has a first side wall, a second side wall and comprises the combined input and output port; the source of optical electromagnetic radiation is sealingly coupled to the first side wall; the optical detector is sealingly coupled to the second side wall; a single optical waveguide is sealingly coupled to the combined input and output port at a first end thereof, and a second end of the optical waveguide has a surface that extends at a substantially non-perpendicular angle with respect to a longitudinal axis of the optical waveguide; an optical launch assembly is disposed at the second end of the optical waveguide and comprises a length of propagation medium abutting the second end of the optical waveguide, a refractive index of the length of propagation medium being arranged substantially to match a refractive index of the optical waveguide; and the beamsplitter is arranged to direct more than 50% of the received optical electromagnetic radiation from the combined input and output port towards the optical detector.