Compact double-pass wavelength multiplexer-demultiplexer

Abstract

An optical multiplexing and demultiplexing device including a fiber mounting assembly for aligning optical fibers, a set of collimating and focusing optics, a transmission grating element, and a mirror element. The fiber mounting assembly alignment element aligns a series substantially close-spaced optical fibers with their ends flush and assembled in a substantially straight line. The optical fibers are either multi-mode or single mode communication fibers capable of transmitting optical wavelengths with substantially high transmittance. The set of collimating and focusing optics, preferably a lens (or mirror) system that contains two (2) or more elements, may be made from optical glasses with uniform refractive indices, optical glasses with gradient indices, plastic optical elements, or diffractive lenses. The transmission grating element can be made from holographic techniques utilizing photosensitive media, where the media having sufficient thickness to provide high diffractive efficiency and wide operation waveband. The photosensitive media providing high spatial resolution in order to generate high groove density—thus high spectral resolution for DWDM applications. The mirror element, having a high reflectance coating for the wavelengths of interest, is arranged at such an angle that the optical radiation will be reflected back to the grating. It will then be diffracted again by the grating then focused to the optical fibers.