The 400mtr Nufern Cladding Mode Free (CMF) Photosensitive SM Fiber C&L Bragg Grating is a high-quality optical component designed for precise control of light in various industrial and research applications. Made by Nufern in the United States, this product offers a unique solution for achieving free spectral range without the need for mechanical tuning, making it a valuable tool for those working in the field of optical engineering and photonics.