A filter module includes a first optical fiber collimator, a second optical fiber collimator, and a filter located between the first and second optical fiber collimators. The first optical fiber collimator includes a first optical fiber, a first optical fiber chip for holding the first optical fiber, and a first lens. The second optical fiber collimator includes second optical fibers, a second optical fiber chip for holding the second optical fiber, and a second lens. The filter is located between and coaxial with the first and second lenses. The filter, the first lens, and the second lens form a center piece of the filter module.