Dynamic spectral maneuvering by fiber Sagnac loop filter

• Need for manipulation of post fabrication spectral response of a wavelength filter is stressed.
• An fiber loop mirror configuration is employed for maneuvering the post fabrication wavelength spectrum of the filter.
• Manipulation of the spectral pattern of a single-stage all-fiber Mach–Zehnder interferometer has been demonstrated.
• Amplified spontaneous emission spectrum of an erbium doped fiber is flattened over a range of 35 nm.

Post fabrication spectral tuning of an all-fiber wavelength filter is a pertinent challenge that needs to be resolved before the filters integration into the communication link. A simple Sagnac interferometer based all-fiber technique has been proposed for dynamic maneuvering of wavelength response of any type of filter so as to match the desired spectral pattern as intended before fabrication of the gadget. The method would prove its usefulness in obtaining preferred position of the wavelength notch, depth of the notch, full width at half maxima from the filter even after its fabrication and thus, mitigates the deleterious effects of departure from the deliberated spectrum. The wavelength response of an all-fiber Mach–Zehnder interferometer has been dynamically manipulated after its fabrication and a gain equalized filter has been realized by employing the projected process. As an application, amplified spontaneous emission of an erbium doped fiber has been flattened over a range of 35 nm within an accuracy of ± 0.26 dB in the C-band.