Coupling Loss From Free Space to Large Mode Area Photonic Crystal Fibers

Simulated and measured results are presented for the coupling loss from free space into a large mode area (LMA) photonic crystal fiber. The total measured loss (using bulk optics) for a signal (¿ = 1.55 ¿m) going in and out of a 1-m-long fiber was -2.15 dB. It was also observed that the fiber is not that sensitive to lateral misalignment compared that to the conventional single-mode fiber. Due to the low loss, this type of fiber could be used to create long delays in optical true-time-delay engines based on the White cell concept and others. The above loss can be further reduced by using field lenses or lensed LMA.