Tuning of long-period fibre gratings written by CO2 laser with resonant transmission below -45 dB

Long-period fibre gratings (LPGs) that were made to have resonant transmission below -45 dB are tuned via their simultaneous bending and straining. It was found that the position of the LPG resonance can be tuned over more than 6 nm, maintaining the level of the resonant transmission below -45 dB. Fine tuning of the resonance transmission without a change in its spectral position is also demonstrated. The reported LPGs should satisfy the strictest requirements on the control of LPG filtering characteristics, especially in terms of the phase response