A communication apparatus for a fibre-optic communication system, the apparatus comprising: an optical coupler; an input port optically coupled to the optical coupler via a first waveguide, the input port being arranged to receive light; a modulator optically coupled to the optical coupler via a second waveguide, the modulator comprising a fibre having a fibre Bragg grating, FBG, arranged to receive the light from the input port via the optical coupler, the modulator being operable to vary a strain force applied to the fibre to modulate a wavelength of a modulated light signal reflected by the FBG back to the optical coupler; and an output port optically coupled to the optical coupler via a third waveguide so as to receive the modulated light signal therefrom, the output port being operable to output the modulated light signal; characterised in that: the apparatus further comprises a visual indicator in optical communication with the modulator so as to receive at least part of the modulated light signal therefrom, the visual indicator being operable to generate a visual indication based on the at least part of the modulated light signal, wherein the visual indicator comprises: a light port, or a photoluminescent material; and in that the modulator comprises: a mechanical input and a mechanical actuator, physically coupled to the fibre and in mechanical communication with the mechanical input, the mechanical actuator being operable to generate the strain force based on a mechanical signal received at the mechanical input; and an extra optical coupler located within the second waveguide, and a semi-reflective reflector in optical communication with the extra optical coupler and the visual indicator, wherein the extra optical coupler is operable to transmit the light from the optical coupler to the FBG, to transmit the modulated light signal from the FBG to the semi-reflective reflector, and to transmit light reflected by the semi-reflective reflector to the optical coupler, wherein the semi-reflective reflector is operable to transmit a first portion of the modulated light signal to the visual indicator and to reflect a remaining portion of the modulated light signal to the extra optical coupler. an optical coupler; an input port optically coupled to the optical coupler via a first waveguide, the input port being arranged to receive light; a modulator optically coupled to the optical coupler via a second waveguide, the modulator comprising a fibre having a fibre Bragg grating, FBG, arranged to receive the light from the input port via the optical coupler, the modulator being operable to vary a strain force applied to the fibre to modulate a wavelength of a modulated light signal reflected by the FBG back to the optical coupler; and an output port optically coupled to the optical coupler via a third waveguide so as to receive the modulated light signal therefrom, the output port being operable to output the modulated light signal; the apparatus further comprises a visual indicator in optical communication with the modulator so as to receive at least part of the modulated light signal therefrom, the visual indicator being operable to generate a visual indication based on the at least part of the modulated light signal, wherein the visual indicator comprises: a light port, or a photoluminescent material; and in that the modulator comprises: a mechanical input and a mechanical actuator, physically coupled to the fibre and in mechanical communication with the mechanical input, the mechanical actuator being operable to generate the strain force based on a mechanical signal received at the mechanical input; and an extra optical coupler located within the second waveguide, and a semi-reflective reflector in optical communication with the extra optical coupler and the visual indicator, wherein the extra optical coupler is operable to transmit the light from the optical coupler to the FBG, to transmit the modulated light signal from the FBG to the semi-reflective reflector, and to transmit light reflected by the semi-reflective reflector to the optical coupler, wherein the semi-reflective reflector is operable to transmit a first portion of the modulated light signal to the visual indicator and to reflect a remaining portion of the modulated light signal to the extra optical coupler. a mechanical input and a mechanical actuator, physically coupled to the fibre and in mechanical communication with the mechanical input, the mechanical actuator being operable to generate the strain force based on a mechanical signal received at the mechanical input; and an extra optical coupler located within the second waveguide, and a semi-reflective reflector in optical communication with the extra optical coupler and the visual indicator, wherein the extra optical coupler is operable to transmit the light from the optical coupler to the FBG, to transmit the modulated light signal from the FBG to the semi-reflective reflector, and to transmit light reflected by the semi-reflective reflector to the optical coupler, wherein the semi-reflective reflector is operable to transmit a first portion of the modulated light signal to the visual indicator and to reflect a remaining portion of the modulated light signal to the extra optical coupler.