BROAD-BAND SPATIAL MODE CONVERSION BY CHIRPED FIBER BENDING

We solve the coupled-mode equations for linearly chirped codirectional mode couplers and use the results to develop design rules for broadba nd couplers. By comparing a chirped coupler with a uniform coupler hav ing the same effective coupling length we find that high coupling effi ciency can be obtained over a substantially wider bandwidth. We design a chirped device to have a 99% bandwidth of 47 nm at 1090 nm, which i s 5.8 times larger than for the uniform coupler. Experimentally the ba ndwidth was improved by a factor of 5.4. Optical Society of America