A carton has side panels extending upwardly from respective edges of the carton’s bottom. These regions facilitate quick editing and formatting of a compressed output signal; for example, logo insertion, color correction, blue-matting and various types of image sequence mixing and manipulation may be performed by decoding and processing individual regions rather than entire frames. The adjacent optical fibers at a forward end portion of the extension portion are fixed to one another integrally. The clamping portion includes at least three members with the first and second members pivotally mounted to each other and the second and third members pivotally mounted to each other. An excitation intensity adjustment circuit controls excitation intensity based on the detected second-harmonic component amplitude such that the second-harmonic component amplitude is kept constant.