Wavelength filter arrangements for use in fiber optics

摘要

A wavelength filter for use with optical fibers comprises a plurality of filter units, each unit comprising first and second collimating lenses separated by a filter element, the filter elements of the two units being capable of passing first and second wavelengths respectively, and each unit being such as to reflect light transmitted by the filter element of each of the other units. A first of the units has its first lens connected to an input optical fiber and also connected to a first connecting optical fiber positioned so that one of these optical fibers is capable of receiving light from the other fiber reflected off the filter element of the first unit. The first unit has its second lens connected to a second connecting optical fiber carrying light of a first wavelength transmited from the input optical fiber through the first filter unit. A second of the units has its first lens connected to the first connecting optical fiber and its second lens connected to the second connecting optical fiber and to an output optical fiber in transmitted light relationship with the first connecting optical fiber. The second connecting optical fiber and the output optical fiber are positioned so that one of these latter fibers is capable of receiving light from the other reflected off the filter element of the second unit.