An identification apparatus comprising: (a) a first connector having mounted thereon an optical signal transmission path arrangement and an optical signal receiving path; (b) a second connector having mounted thereon an optical signal return path arrangement extending from an input end to an output path, the second connector configured to connect to the first connector in an operating position in which the input end of the optical signal return path arrangement is operatively aligned with the optical signal transmission path arrangement and the output path is operatively aligned with the optical signal receiving path; (c) an optical signal modification arrangement operable to provide a predefined modification to a base optical signal applied at the input end of the optical signal return path arrangement, the predefined modification resulting in an optical ID signal applied at the output path of the optical signal return path arrangement; (d) an optical transmitter arrangement operable to apply the base optical signal to the optical signal transmission path arrangement; (e) an optical receiver operable to receive the optical ID signal from the optical signal receiving path and produce an ID input signal responsive to the received optical ID signal; and (f) an identification processing unit connected to receive the ID input signal, the identification processing unit being operable to produce an identification output responsive to the ID input signal; characterised in that the base optical signal includes two or more optical signal components and wherein the two or more base optical signal components are temporally offset and/or each of the two or more base optical signal components is transmitted at a different respective modulation frequency. (a) a first connector having mounted thereon an optical signal transmission path arrangement and an optical signal receiving path; (b) a second connector having mounted thereon an optical signal return path arrangement extending from an input end to an output path, the second connector configured to connect to the first connector in an operating position in which the input end of the optical signal return path arrangement is operatively aligned with the optical signal transmission path arrangement and the output path is operatively aligned with the optical signal receiving path; (c) an optical signal modification arrangement operable to provide a predefined modification to a base optical signal applied at the input end of the optical signal return path arrangement, the predefined modification resulting in an optical ID signal applied at the output path of the optical signal return path arrangement; (d) an optical transmitter arrangement operable to apply the base optical signal to the optical signal transmission path arrangement; (e) an optical receiver operable to receive the optical ID signal from the optical signal receiving path and produce an ID input signal responsive to the received optical ID signal; and (f) an identification processing unit connected to receive the ID input signal, the identification processing unit being operable to produce an identification output responsive to the ID input signal;