Abstract
In this paper, we present the simulation and experimental results of the first closed-loop system based on a directly modulated VCSEL in a gain-switching condition to generate optical frequency combs (OFC). In order to simulate the self-starting VCSEL-based optical frequency comb generator (SVOFC), we applied an intrinsic parameter extraction process to a C-band VCSEL using laser rate equations, static and dynamic measurements, and equivalent circuit models. The widest (62 GHz) and flattest (0.8) simulated OFC is obtained when the repetition frequency f0 is 2.5 GHz. Implementation of the C-band SVOFC also shows that under constant electrical conditions, flatness higher than 0.85 and spectral widths of 50 GHz are obtained when f0 = 2.5 GHz. The lowest phase noise at 10 kHz from the extracted electrical carrier is -127 dBc/Hz and is obtained when the optical fiber length is 5 km and f0 = 1.25 GHz.
Highlights
Over the last few years, optical frequency comb (OFC) generation has emerged as a research topic of particular interest with a wide variety of applications such as spectroscopy [1,2], THz generation [3], LIDAR [4], optical communications [5], and physical variable sensing [6]
We have presented and experimentally demonstrated the first closed-loop system for optical frequency comb generation using a modulated vertical-cavity surface-emitting lasers (VCSELs) in gain-switching condition
Through C-band started VCSEL-based optical frequency comb generator (SVOFC) simulation and implementation, we demonstrated that the performance of the optical frequency comb generated with the SVOFC is related to the bias current, the modulating electrical power, and the repetition frequency
Summary
Over the last few years, optical frequency comb (OFC) generation has emerged as a research topic of particular interest with a wide variety of applications such as spectroscopy [1,2], THz generation [3], LIDAR [4], optical communications [5], and physical variable sensing [6]. The OFC generation through closed optoelectronic loops has been widely investigated during the last decade This mechanism has two features: the absence of external microwave signal generators and the presence of one or more cascade external modulators, which allow the generation of flat optical combs and sometimes, adjustable frequency spacing. Unlike the systems with gain-switched VCSELs available in the literature, our system called self-started VCSEL-based optical frequency comb generator (SVOFC) does not require an electrical microwave reference signal. On the contrary, it can generate a low phase noise signal provided by the quality factor of the optical resonant cavity used.
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