A device comprising: a first semiconductor component comprising at least two lasers (125-1, 125-2) to emit light at a first wavelength; a second semiconductor component comprising at least two lasers (125-3, 125-4) to emit light at a second wavelength, the first wavelength being different from the second wavelength; and an optical multiplexer component to receive light from two lasers (125-1, 125-2) at the first wavelength and light from two lasers (125-3, 125-4) at the second wavelength, characterised in that the optical multiplexer component includes: a first output interface to couple light from one laser at the first wavelength and light from one laser at the second wavelength to a first optical fiber, and a second output interface to couple light from one laser at the first wavelength and light from one laser at the second wavelength beams to a second optical fiber; and in that: the optical multiplexer component further comprises: one reflector to reflect substantially all wavelengths of light; and one wavelength selective filter to allow light at either the first wavelength or the second wavelength to pass through and to reflect other wavelengths of light, wherein, the one reflector and the one wavelength selective filter are positioned relative to the first and second semiconductor components to direct light from one laser at the first wavelength and light from one laser at the second wavelength to the first output interface and to direct light from one laser at the first wavelength and light from one laser at the second wavelength to the second output interface. a first semiconductor component comprising at least two lasers (125-1, 125-2) to emit light at a first wavelength; a second semiconductor component comprising at least two lasers (125-3, 125-4) to emit light at a second wavelength, the first wavelength being different from the second wavelength; and an optical multiplexer component to receive light from two lasers (125-1, 125-2) at the first wavelength and light from two lasers (125-3, 125-4) at the second wavelength, characterised in that the optical multiplexer component includes: a first output interface to couple light from one laser at the first wavelength and light from one laser at the second wavelength to a first optical fiber, and a second output interface to couple light from one laser at the first wavelength and light from one laser at the second wavelength beams to a second optical fiber; and in that: the optical multiplexer component further comprises: one reflector to reflect substantially all wavelengths of light; and one wavelength selective filter to allow light at either the first wavelength or the second wavelength to pass through and to reflect other wavelengths of light, wherein, the one reflector and the one wavelength selective filter are positioned relative to the first and second semiconductor components to direct light from one laser at the first wavelength and light from one laser at the second wavelength to the first output interface and to direct light from one laser at the first wavelength and light from one laser at the second wavelength to the second output interface. a first output interface to couple light from one laser at the first wavelength and light from one laser at the second wavelength to a first optical fiber, and a second output interface to couple light from one laser at the first wavelength and light from one laser at the second wavelength beams to a second optical fiber; and in that: the optical multiplexer component further comprises: one reflector to reflect substantially all wavelengths of light; and one wavelength selective filter to allow light at either the first wavelength or the second wavelength to pass through and to reflect other wavelengths of light, wherein, the one reflector and the one wavelength selective filter are positioned relative to the first and second semiconductor components to direct light from one laser at the first wavelength and light from one laser at the second wavelength to the first output interface and to direct light from one laser at the first wavelength and light from one laser at the second wavelength to the second output interface. one reflector to reflect substantially all wavelengths of light; and one wavelength selective filter to allow light at either the first wavelength or the second wavelength to pass through and to reflect other wavelengths of light, wherein, the one reflector and the one wavelength selective filter are positioned relative to the first and second semiconductor components to direct light from one laser at the first wavelength and light from one laser at the second wavelength to the first output interface and to direct light from one laser at the first wavelength and light from one laser at the second wavelength to the second output interface.