Effect of UV-induced birefringence on long-period-grating coupling characteristics

For the first time, an investigation into the effect of photoinduced birefr ingence on the coupling characteristics of long-period-gratings (LPGs) is p resented. Current values of photoinduced birefringence are shown to be suff icient to induce the polarisation-dependent coupling of two components sepa rated by similar to 2-3nm into each cladding mode. Consequently, a major ch ange in the coupling growth characteristics has been experimentally recorde d during the photoinscription thereby avoiding total losses to the cladding modes.