Pulse compression utilizing hybrid Sagnac etched double clad fiber interferometer

A fiber hybrid Sagnac interferometer pulse compressor was designed and implemented in this work, which is a special type of interferometer that incorporates different types of interferometers. The Sagnac interferometer is implemented utilizing four single mode fibers (SMF’s), while the other interferometer is an inline Mach Zehnder interferometer (IMZI) that is implemented utilizing a double cladding fiber (DCF). Five different diameters of DCF-based sensing heads are obtained after etching using hydro-fluric (HF) acid for (0, 10, 20, 30, 40) minutes, they are (122.857, 98.435, 90.704, 73.975, 46.459) µm and are spliced between two identical SMF’s of the same length (8 cm). These etching durations were selected to have differences between acquired results, and because etching for 50 min could result in breaking the optical fiber as it would become too fragile to be implemented in the setup. To the authors’ knowledge, there is no previous research about using the DCF13 as the sensing head of a hybrid Sagnac IMZI, and no earlier research covering it being etched by HF acid and simulating the remaining number of modes in each case. For each one of the resulting IMZI’s after etching, a hybrid Sagnac interferometer is implemented. The designed system performance was studied in terms of various parameters, they include the spatial compression factor and the optical signal to noise ratio (OSNR). The maximum obtained value of spatial compression factor is about 1.851, which is obtained when sensing head of IMZI was etched for 20 min and it is preceded by an erbium doped fiber amplifier with 25 dBm gain. The Maximum obtained value of OSNR is about 7.53528 dB. An oscilloscope is also used in place of the optical spectrum analyzer in all reading cases in order to obtain temporal response results in addition to spatial ones. In all cases, the used source is a pulsed laser source with 80.854 µW peak power, 1546.514 nm central wavelength, 220.219 pm Full Width at Half Maximum (FWHM), and 50% duty cycle.