Fiber Bragg Grating 200 um Long-period grating 500 nm Bragg grating 125um Cladding 8 Core 1 mm to 1500 mm Singlemode fibre Regions with higher refractive index than that of core’sFiber Bragg Grating ~ 500 nm (Bragg grating) ~ 200 µm (Long-period grating) 125 µm 8 µm 1 mm to 1500 mm Singlemode fibre Core Cladding Regions with higher refractive index than that of core’s