Investigation of single sideband optical frequency comb generations using a dual-electrode Mach-Zehnder modulator in a fiber recirculating loop

Abstract

The precise measurement of difference frequencies between two lasers in a terahertz (THz) region is a basic technique for optical frequency standards and for many other applications, such as dense WDM communication systems. Frequency difference measurements based on the beat signal between two lasers become quite difficult when the frequency difference exceeds the detector bandwidth. An optical frequency comb (OFC) generator with an electro-optic (EO) phase modulator inside a Fabry-Perot cavity can overcome this problem. The OFC generator creates a large number of sidebands, which can be applied for frequency markers. In conventional OFC generation, modulation sidebands appears on both sides of the carrier, which is a disadvantage for the efficient use of frequency bandwidth. The limit of the frequency difference measurement with this scheme depends on the power degradation in the sidebands. We propose an alternative technique for generating OFC which employs a dual-electrode Mach-Zehnder Modulator (D-MZM) inside a fiber recirculating loop to generate optical single sideband (SSB). This enables the efficient use of the frequency bandwidth. An optical amplifier is used in the loop to compensate for the losses.