A conventional optical system having a low f-number and a wide field of view contains many reflecting and refracting elements. Such a system poses problems in alignment and mechanical stability, especially when operating in sever environments over a wide range of temperature. A fiber bundle designed in the form of a cone with a larger diameter at the entrance than the diameter at the exit transmits and reduces the image size. This permits the use of a simple lens of longer focal length and larger effective aperture. Since there is a net gain in flux per unit area, this system intensifies as well as transmit an image. It also enables the use of detector of smaller size to achieve a higher signal-to-noise ratio.