EFFICIENT SELF-ALIGNING MULTIBEAM COUPLING INTO A SINGLE-MODE FIBER

We present and demonstrate a method for efficient coupling of many bea ms into a single-mode fiber. Using the phase conjugating property for mutually incoherent beams of the Double Phase Conjugate Mirror (DPCM), we achieved coupling for a full 6x6 matrix of beams into a single-mod e fiber. In principle, this number of input channels can be increased manifold beyond the 36 used in our experiment. Of the phase conjugate generated by the DPCM in the direction of the fiber, over 97% (Fresnel corrected) entered the fiber, thus giving a highly accurate coupling. The DPCM transmission efficiency itself was measured at 40% (Fresnel corrected), thus giving an overall coupling efficiency of 39%. By opti mizing the DPCM parameters, a significantly higher overall coupling co uld be achieved. An additional advantage of this method is that the DP CM will reconfigure if there are small changes in the system, thus mak ing the system very robust. This multichannel coupling method can be o f importance in the coupling of the output beams of a Vertical Cavity Surface Emitting Laser (VCSEL) into a single-mode fiber where each cha nnel may carry independently modulated information. This technique can be further generalized to a bidirectional multisingle-mode fiber inte rconnection system, of which a basic 3x2 system is demonstrated.