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In this work, we demonstrate a tunable optical frequency comb (OFC) source based on a cascaded frequency modulator (FM) and two Mach–Zehnder modulators (MZMs). The setup includes one FM and two MZMs, and a sinusoidal RF signal source that directly drive all these modulators. A Flat OFC source with a high number of comb lines, and tunable frequency spacing and center wavelength is analytically modelled and simulated. The results reveal that 51 comb lines with a frequency spacing of 25 GHz are generated when only FM is used. Thirteen of these lines have power variations of 1 dB. Next, by cascading FM with two MZMs, 127 comb lines are obtained. In addition, 101 of these lines have power variations of 1 dB. An optical frequency comb, with tunable frequency spacing ranging from 10 to 40 GHz is successfully generated. Moreover, the center wavelength of the generated OFC can be tuned from 1310 to 1610 nm. [ABSTRACT FROM AUTHOR]

In this paper, a new method to realize the optical fibre sensor using an optical heterodyne technique (OHT) is proposed and numerically demonstrated. In this method, the bandpass filter (BPF) was utilized as a reference element and fibre Bragg grating (FBG) served as a sensing element. The wideband light is equally split and launched to sensing and reference elements. The reflected light of sensing element coherently interferes with the output of BPF inside 3-dB coupler. A photodiode detects the interfered signal and the beat frequency can be determined to achieve a high-resolution. To examine the proposed method, the scheme for temperature sensing is investigated. The Fabry-Perot narrow-bandpass filter type (F7 glass) serve as BPF. The results reveal that a good and fast response to temperature change with the sensitivity of 1.152 GHz/oC can be obtained. [ABSTRACT FROM AUTHOR]