Laser diode module for single-mode fiber based on new confocal combination lens method

A practical laser diode module is demonstrated for single-mode fiber applications. The module was developed through the use of a new combination lens method. The second lens in the confocal two-lens method is divided into two lenses. One is attached to the single-mode fiber front endface, thus forming a virtual fiber. Since both virtual fiber and lens misalignment tolerances are large in this coupling method, soldering is easily applicable. The laser diode module could be fabricated as easily as that for a multimode fiber. High coupling efficiency, excellent reproducibility, and high reliability were confirmed in trial-fabricated modules. Moreover, output power fluctuation due to reflected lightwaves was found to be very small.